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kitplane01
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C-17 Usage

Sun Dec 20, 2020 4:58 am

texl1649 wrote:
kitplane01 wrote:
RJMAZ wrote:
The USAF C-17 fleet works incredibly hard. The C-5 fleet has kept to smooth runways and with very low G loads. Managing fatigue life is part of extending the C-5 service life.

The C-17 gets used for all the rough work with tactical max effort landing and takeoffs on rough runways. Unless the C-17 fleet gets strict G load limits and kept on smooth runways it is incredibly difficult to extend and manage the service life. Applying these limits to the C-17 would be like limiting the F-15C fleet to only 3G so that it lasts another 50 years. It can no longer get the job done for the USAF.


My impression was that almost always the C-17's were flying from one airbase to another (or civilian airport) and were very rarely landing on anything else. I don't have data. Why do you think that the C-17s are getting lots of time on rough runways? Do you mean grass/sand/gravel?


I don’t think it is ‘just’ the surface they land on, but the conditions used to fly into places like Bagram/Baghdad etc. Steep, heavy load/stress approaches/landings to avoid/minimize risk of SAM/small arms fire.

They’ve been getting delivered since the early 90’s, and were designed with a 30 year, 30,000 hour service life. They’re not the military equivalent of a DC-9, able to just run out to 120K hours. Utilization over the past 20 years has been roughly double what expectations were.


texl1649 wrote:

I don’t think it is ‘just’ the surface they land on, but the conditions used to fly into places like Bagram/Baghdad etc. Steep, heavy load/stress approaches/landings to avoid/minimize risk of SAM/small arms fire.

They’ve been getting delivered since the early 90’s, and were designed with a 30 year, 30,000 hour service life. They’re not the military equivalent of a DC-9, able to just run out to 120K hours. Utilization over the past 20 years has been roughly double what expectations were.


(I don't want to hijack the C-2 thread, so new thread)

Two questions:

1) The original claim implied the C-17s were often/commonly used on rough strips. Is this true? I think it's way under 5%, but have no data so if someone even has a reasonable guess I'm interested. I really think almost every (but not all) C-17 flights are from runway to runway.

2) Why would a C-17 have less fatigue life than a normal civilian freighter? Is this true? Surely they get more maintenance per flight hour, and the landing gear are stronger. And does anyone know how many hours are on the C-17s?
 
WIederling
Posts: 10041
Joined: Sun Sep 13, 2015 2:15 pm

Re: C-17 Usage

Sun Dec 20, 2020 11:02 am

I really think almost every (but not all) C-17 flights are from runway to runway. ..

And average load is low. discussed here years ago : less than 10t on average.

Design service life targets are much lower than on commercial airframes.
(IMU the reason nigh nobody in civil transport has taken up the L100, a "white" C130 )
Afaik C160 civil use was limited to the French Post Office.
 
Ozair
Posts: 5582
Joined: Mon Jan 31, 2005 8:38 am

Re: C-17 Usage

Sun Dec 20, 2020 11:14 am

kitplane01 wrote:
Two questions:

1) The original claim implied the C-17s were often/commonly used on rough strips. Is this true? I think it's way under 5%, but have no data so if someone even has a reasonable guess I'm interested. I really think almost every (but not all) C-17 flights are from runway to runway.

runway to runway for 99.9999% of all landings (anywhere the aircraft lands is a runway really... ;) ) but it would be interesting to know how many were
1. sealed runway to sealed runway
2. sealed runway to rough field (gravel/sad/dirt etc)
3. rough field to sealed runway.

I doubt we will ever know this info.

How rough on the airframe are these landings, especially those with light loads? For example the following video from youtube https://www.youtube.com/watch?v=7Io-kun ... l=AleFox88 it looks like the aircraft came in very light and went out comparatively very light. I doubt those landings place any more stress on the airframe than a heavier weight landing on a sealed runway.

kitplane01 wrote:
2) Why would a C-17 have less fatigue life than a normal civilian freighter? Is this true? Surely they get more maintenance per flight hour, and the landing gear are stronger. And does anyone know how many hours are on the C-17s?

Like most USAF assets they probably get over serviced. For reference it is probably worth estimating overall fleet use based on the following,

C-17 fleet celebrates 3M flying hours

The C-17 Globemaster III has proved again that it remains the world's premier airlifter after the total C-17 fleet celebrated the historical milestone of achieving 3 million flying hours on May 5.

The C-17 is the only strategic airlifter in the world that has tactical capabilities that allow it to fly between continents; land on short, austere runways and airdrop supplies precisely where needed. The C-17 fleet is in its 22nd year of operation; it was first delivered in June 1993.

Getting to the 3 millionth flying hour all started on Sept. 15, 1991, when the aircraft made its maiden flight. The C-17 passed the 1-million-hour mark in March 2006 and the 2-million-hour mark in December 2010.

A ceremony was held at Robins Air Force Base, Georgia, and Joint Base Charleston to commemorate the fleet’s milestone. As part of the ceremony, a combined Charleston aircrew and Boeing team flew a ceremonial flight.

"It is such a great privilege and an honor to be a part of the C-17 program," said Col. Amanda Meyers, the C-17 System Program director. "In the C-17's relatively short history, it has done extraordinary things.

The platform provides unparalleled strategic and tactical airlift and airdrop capability to our nation as well as eight other partner nations," Meyers continued. "It has become the airlifter of choice for our Air Force. The incredible partnership between our active-duty, Reserve forces and National Guard make the C-17 a huge enabler for the United States of America. It not only allows us to fight and win our nation's wars, but also to provide humanitarian assistance at an international level."

The Air Force owns 222 C-17s and our international allied partners have 44 of these strategic airlifters.

"Our partner nations also benefit greatly from the capabilities that the C-17 brings to their defense organizations and national global contributions," Meyers said.

Meyers, who became the C-17 program director last summer, realizes now how much heavy lifting the C-17 does.

"Every time the news is on and there's a call for assistance or unquestionable capability, the C-17 is part of the story," she said. "Last summer, I turned on the news to see a Royal Australian Air Force C-17 conducting a dignified transfer after the MH17 (crash). Last week, I turn on the news to hear about the earthquake in Nepal and see an Indian Air Force C-17 providing humanitarian help, quickly followed by C-17s from the United States, Canada and United Kingdom.

“The C-17 is where and when the nation calls, wherever that is, to go to war or promote peace," Meyers continued. "Our mission is to acquire and obtain safe, effective and unrivaled global reach capability."

Along the flight with Meyers was retired Maj. Gen. Robert McMahon, the Boeing director of field operations.

"As many of you know, this is Boeing's 100th anniversary, and we have challenged each employee to build something better," McMahon said. "I will tell you that with the C-17, we have accomplished just that. The world's premier airlifter."

McMahon recognized that the success of the aircraft lies with the people that built it, maintain it and fly it.

"We and Boeing are tremendously proud of those that designed and built this aircraft, those today that maintain and sustain this aircraft and those the currently operate the aircraft," he said.

Over time, the world has come to see the C-17 as the vehicle that carries hope and freedom.

"What makes (the C-17) special is each and every day, no matter the condition, this aircraft carries something very special, and that is hope to the people on the ground," McMahon said. "Whether that was in Iraq or Afghanistan, or whether that's the streets of New Orleans during the floods, or whether that's someplace like Nepal today. When that t-tail shows up each and every day, what that means to the people on the ground, is hope for the future. That's what these tremendous crews deliver."

Following the preflight ceremony at Robins AFB, Charleston Airmen prepared for takeoff as they had their eyes set on returning home.

Once the crew arrived at Charleston, Col. John Lamontagne, the 437th Airlift Wing commander, addressed those in attendance at the ceremony.

"Today is an amazing celebration recognizing 3 million hours in the C-17," Lamontagne said. "We've come a long way since we first arrived here in July of 1993. Lots of lessons (have been) learned. It's a fantastic airplane built by Boeing for the Air force.

"The Air Force talks about ‘do something amazing,'" Lamontagne said. "This airplane does something amazing."

https://www.af.mil/News/Article-Display ... %20May%205.

So what do we know from above?

1 million hours passed in March 2006
2 million hours passed in December 2010
3 million hours passed in May 2015

So it feels like they should be close to 4 million hours soon. At the 1 million mark the USAF had received 148 aircraft, by the second million they had received 205 and by the third million the whole 220 fleet. Feels like they should be due to hit four million soon based on the above timeframes. We know some aircraft have been retired to an active reserve but none have been sent to AMARC (that I can tell from the register) while the USAF planned to retrofit all aircraft with the same avionics and upgrades that the final 70 received during production.

At four million hours the fleet then has an average of 18,200 hours with some of those airframes almost certainly above 20k and a number likely closer to 10k. If we take the comments from Everhart I posted in the other thread then AMC thinks they can get at least another ten years from the current fleet by rotating high use aircraft for low use and it looks like that should be quite possible. We know they are aiming for 42k hours from the aircraft based on this quote from 2015

The command has made “great progress” in upgrading its C-17 fleet so far, and it expects to push the C-17 fleet beyond its original lifespan of 30,000 flight hours to a new goal of 42,000 hours.

https://www.airforcemag.com/amc-to-fly- ... 2000-hour/

The issue then becomes whether the USAF can SLEP the aircraft and get additional years out of the airframe. Everhart a year later thought a re-engine was possible which you would expect wouldn't be done unless they thought there was another 10 to 15k available out of the airframe minimum.

Everhart said the C-17 “drinks a lot of gas” and may benefit from a re-engining at some point, and he expects there will be a service life extension program, but it will probably be done incrementally when the jets come in for depot maintenance. Applying “fleet dynamics”—swapping aircraft out of high-corrosion environments like the Pacific and making sure the fleet ages evenly by tail number—will buy as much as ten years of service life, Everhart said. The C-17 could be a “60-80-year airplane,” Everhart said

https://www.airforcemag.com/long-live-the-c-17/

So fleet average age today is about 18k flight hours. AMC is looking to get 42k flight hours out of them so that means the fleet as a whole has done less than half the number expected. Given the fleet has done those hours in approx 25 years you could expect another 25 years from the fleet taking their retirement past 2040. Will maintenance be more costly later in life, for sure, but the USAF is used to dealing with old aircraft given almost all their bomber fleet (last B-2 delivered in 2000) and until the arrival of the KC-46 their whole tanker fleet are all older than the whole C-17 fleet...
 
texl1649
Posts: 1956
Joined: Thu Aug 02, 2007 5:38 am

Re: C-17 Usage

Sun Dec 20, 2020 1:32 pm

This is a good new thread, thx. I’ve looked and can’t find hours per frame on these. The only thing we really seem to know is that they were designed for 30 year, 30K hour lives.

Downing emphasized the aircraft’s austere or “short field” landing capability, praising its recent performance in Afghanistan. The plane is engineered to land on a short field because thrust from the motor blows over flaps when the aircraft comes into land, providing additional lift at slower speeds, Downing explained.

The Air Force’s 222 C-17 aircraft are designed to fly for 30,000-flight hours or reach 30-years of service.


https://www.military.com/dodbuzz/2013/1 ... in-pacific

There was a quote, which I’m internet-inept at finding now, back around 2014 from a USAF general about ‘flying the wings off the C-17 fleet’ supporting Iraq and Afghan operations, but I can’t find more. I do think a rapid descent/closed airfield/rapid take off with cargo is harder on the wing box/frame in general, but again I don’t have documentation for how often it’s done, just the general data that it is often the chosen airlifter for this task. Once again I am not sure if most of the aircraft (other than tires) cares/knows if it’s on a gravel/dirt/rough field, one way or the other, but the stuff you see with it’s short field capability demonstrations does certainly exert a ton of stress, figuratively speaking. And that stuff also has to be trained, for the crews, of course, not just shown off at air shows.

I don’t see the cite showing an average per frame use in 2020 (or any year) of 18K hours. I am sure it is at/around 4 million flight hours overall, but surely the frames from the 90’s are well past that (likely well past 25K hours, and talk of ‘balancing’ wear on frames in the fleet is often a lot easier said than done.) My suspicion is that the USAF has no desire to highlight the need to SLEP/do anything to supplement the C-17 given the TACAIR and B-21 and KC-46 priorities in acquisition/funding the next 10 years. I don’t think that’s a tin foil hat theory, just a reality. It’s highly likely, imho, that as with the C-141 and C-5 fleets before it, some sort of cracks/serious structural issues will be ‘found’ in the older/higher time members of the C-17 fleet in the next 5 years, resulting in some being ‘temporarily’ sent to the desert.

I understand Gen. Everhart had expectations it would easily be done in 2016, but I am dubious as to his accuracy in this prognostication (how many flag officers really know the engineering/contracting costs likely in such a situation in advance?), and find the interest in fuel economy....particularly ironic given how long the USAF has flown certain engines on KC-135’s/707 frames (various flavors), B-52’s, C-5’s, E-4’s, C-141’s, etc. Fuel economy is often bantered about as a possible program justification driver, but rarely actually drives a timely upgrade (yes, eventually it happens, such as B-52/KC-135 sometimes). For goodness sakes, just look at the KC-46 they want to buy by the hundreds the next 10 years. Easily a 10 percent savings if they’d just tried to get a GEnX on it. The C-17 was simply not engineered to be fuel efficient (nor fast) relative to her civilian ‘peers.’

Finally, I’d note that at ASC/AFA meetings/discussions over the past actual 4 years, basically nothing has addressed long term sustainability of the Globemaster fleet. Sure, new HUD, Boeing taking over some of the maintenance contract (from L3), but it is anything but ‘on the radar’ vs. exciting stuff mentioned above, AFBMS etc.
 
Buckeyetech
Posts: 177
Joined: Wed Jul 03, 2013 1:11 am

Re: C-17 Usage

Sun Dec 20, 2020 2:12 pm

I can’t find the article, but I’m fairly confident there’s a single C-17 that surpassed 30,000 hours a couple years ago. Considering that most cargo TRANSCOM flies on milair, is not oversized, I feel like they can get the job done with with the KC-46’s coming online, and start retiring C-17s in large numbers in a decade or so from now.
 
Ozair
Posts: 5582
Joined: Mon Jan 31, 2005 8:38 am

Re: C-17 Usage

Sun Dec 20, 2020 6:31 pm

texl1649 wrote:
This is a good new thread, thx. I’ve looked and can’t find hours per frame on these. The only thing we really seem to know is that they were designed for 30 year, 30K hour lives.

Downing emphasized the aircraft’s austere or “short field” landing capability, praising its recent performance in Afghanistan. The plane is engineered to land on a short field because thrust from the motor blows over flaps when the aircraft comes into land, providing additional lift at slower speeds, Downing explained.

The Air Force’s 222 C-17 aircraft are designed to fly for 30,000-flight hours or reach 30-years of service.


https://www.military.com/dodbuzz/2013/1 ... in-pacific

There was a quote, which I’m internet-inept at finding now, back around 2014 from a USAF general about ‘flying the wings off the C-17 fleet’ supporting Iraq and Afghan operations, but I can’t find more. I do think a rapid descent/closed airfield/rapid take off with cargo is harder on the wing box/frame in general, but again I don’t have documentation for how often it’s done, just the general data that it is often the chosen airlifter for this task. Once again I am not sure if most of the aircraft (other than tires) cares/knows if it’s on a gravel/dirt/rough field, one way or the other, but the stuff you see with it’s short field capability demonstrations does certainly exert a ton of stress, figuratively speaking. And that stuff also has to be trained, for the crews, of course, not just shown off at air shows.

Here is some factual analysis to the "flying the wings off" claims... This report by The Office of the Under Secretary of Defense (Acquisition, Technology and Logistics), Property and Equipment Policy Office and Office of the Under Secretary of Defense (Comptroller), Accounting and Finance Policy Office which was released in 2008 stated the following,

...

The C-17A program has a design service life of 30,000 flight hours per aircraft. Currently, the C-17 airframes are not experiencing operational usage or fatigue that impacts their ability to achieve the 30,000 hour service lives. The missions that are flown are within the design assumptions/parameters of the aircraft. More specifically, the airframe was designed to withstand a higher percentage of airdrop, assault landing, and low level missions than has been experienced during C-17 operations. Because of that, the actual usage severity, in most cases, is less than predicted; therefore, there is no indication that C-17 airframes will be unable to meet or exceed the specified usage-based service life. However, future changes in C-17 operations/deployment strategies could have an adverse effect on service life and would need to be considered during service life analysis by factoring weighted hours using the methodology.

https://www.acq.osd.mil/pepolicy/pdfs/O ... Report.pdf

Now this report was released in Mar 2008 and you would expect that the recommendations factored in the start of the Iraq surge in 2007. It probably doesn't factor in the mass delivery of MRAPS from 2008-2013. Not sure how many of these 12000 were transported on C-17s and C-5s but would have to have been a decent percentage given the visibility. What is clear is that the GWOT mission to that date had not been significant as far as aircraft fatigue. They may have flown a lot of hours but those were not heavy fatigue inducing hours.

we also have the next quote,
For example, the Air Force Materiel Command has assessed that the C-17 program’s service life is 45,000 flight hours as opposed to the initial 30,000 flight hours projected by the original equipment manufacturer and PM based on fatigue and mission-type analysis


So a second reference to an AMC increase in expected service hours from that initial 30k to above 40k. Makes sense that in 2015 AMC then said 42k perhaps based on additional usage from ops during the later years of Iraq and Afghanistan.

texl1649 wrote:
I don’t see the cite showing an average per frame use in 2020 (or any year) of 18K hours. I am sure it is at/around 4 million flight hours overall, but surely the frames from the 90’s are well past that (likely well past 25K hours, and talk of ‘balancing’ wear on frames in the fleet is often a lot easier said than done.)

No one is claiming the average is sitting at 18k across the whole fleet, it is obviously nearly impossible given the span of deliveries. The USAF is very good at fleet management though, AMC would know the hours on every single aircraft and be able to rotate them through as required to minimise hours on high hour aircraft and maximise hours on low hour aircraft. It really isn't rocket science to manage the fleet this way.

texl1649 wrote:
My suspicion is that the USAF has no desire to highlight the need to SLEP/do anything to supplement the C-17 given the TACAIR and B-21 and KC-46 priorities in acquisition/funding the next 10 years. I don’t think that’s a tin foil hat theory, just a reality. It’s highly likely, imho, that as with the C-141 and C-5 fleets before it, some sort of cracks/serious structural issues will be ‘found’ in the older/higher time members of the C-17 fleet in the next 5 years, resulting in some being ‘temporarily’ sent to the desert.

That seems the wrong conclusion to draw from the data. The conclusion I draw is that the USAF doesn't need to talk about it because the USAF currently view the C-17 as being retired post 2040 which means they have more than ten years before they need to even start considering a replacement program. The C-5M is now expected to fly into the 2040s so there emerges an opportunity to replace both fleets with a single aircraft, if the respective requirements that both fleets cover can be met by one airframe.

texl1649 wrote:
I understand Gen. Everhart had expectations it would easily be done in 2016, but I am dubious as to his accuracy in this prognostication (how many flag officers really know the engineering/contracting costs likely in such a situation in advance?), and find the interest in fuel economy....particularly ironic given how long the USAF has flown certain engines on KC-135’s/707 frames (various flavors), B-52’s, C-5’s, E-4’s, C-141’s, etc. Fuel economy is often bantered about as a possible program justification driver, but rarely actually drives a timely upgrade (yes, eventually it happens, such as B-52/KC-135 sometimes). For goodness sakes, just look at the KC-46 they want to buy by the hundreds the next 10 years. Easily a 10 percent savings if they’d just tried to get a GEnX on it. The C-17 was simply not engineered to be fuel efficient (nor fast) relative to her civilian ‘peers.’

Finally, I’d note that at ASC/AFA meetings/discussions over the past actual 4 years, basically nothing has addressed long term sustainability of the Globemaster fleet. Sure, new HUD, Boeing taking over some of the maintenance contract (from L3), but it is anything but ‘on the radar’ vs. exciting stuff mentioned above, AFBMS etc.

Agree the engine upgrade may not occur, it obviously takes a lot to get an engine upgrade program through. You could also suggest that ASC/AFA talk the last few years hasn't focused on the C-17 because the KC-46 has taken a lot of time and discussion.

Buckeyetech wrote:
I can’t find the article, but I’m fairly confident there’s a single C-17 that surpassed 30,000 hours a couple years ago. Considering that most cargo TRANSCOM flies on milair, is not oversized, I feel like they can get the job done with with the KC-46’s coming online, and start retiring C-17s in large numbers in a decade or so from now.

No C-17s have flown 30k flight hours as far as I am aware. The highest C-17 was 91192, the sixth aircraft received in 1993, which passed 20k flight hours in 2013.

JB Charleston C-17 reaches 20,000 flight hours

The first C-17 Globemaster III to join the Air Force fleet, "The Spirit of Charleston," reached new heights recently by logging more than 20,000 flight hours.

...

https://www.amc.af.mil/News/Article-Dis ... ght-hours/

20 years of service, 20k flight hours so based on AMC expectations and it flying the same number of hours every year would serve until 2035. Given we know the USAF is managing the fleet I expect they will get longer out of it.
 
JayinKitsap
Posts: 2680
Joined: Sat Nov 26, 2005 9:55 am

Re: C-17 Usage

Sun Dec 20, 2020 9:56 pm

I regularly deal with fatigue issues in steel, not aluminum, which looks at stress range, configuration under review and number of cycles. Non-welded base metal in axial or flexure is a class A configuration. A cover plate welded across its ends is a Class E, the worst. With 50 KSI yield steel the Class E stress range is only 6 KSI at the highest range of 500,000+ cycles. So this detail logs a cycle if the stress changes only 6,000 psi max to min, it may be stressed constantly at 24 ksi, or a range from 24 to 30 ksi. Good fatigue design is to only use Class A, B, C configurations.

Aluminum is a more difficult metal, but I would expect stress ranges vs cycles to govern there also. An unimproved field landing may take as much life as 10 runway landings at the same weight. All this is predictive, what happens in the real world my differ, for example one heat of metal may show better (or worse) cracking over time.
 
texl1649
Posts: 1956
Joined: Thu Aug 02, 2007 5:38 am

Re: C-17 Usage

Sun Dec 20, 2020 10:26 pm

Ozair wrote:
Here is some factual analysis to the "flying the wings off" claims... This report by The Office of the Under Secretary of Defense (Acquisition, Technology and Logistics), Property and Equipment Policy Office and Office of the Under Secretary of Defense (Comptroller), Accounting and Finance Policy Office which was released in 2008 stated the following,

...

The C-17A program has a design service life of 30,000 flight hours per aircraft. Currently, the C-17 airframes are not experiencing operational usage or fatigue that impacts their ability to achieve the 30,000 hour service lives. The missions that are flown are within the design assumptions/parameters of the aircraft. More specifically, the airframe was designed to withstand a higher percentage of airdrop, assault landing, and low level missions than has been experienced during C-17 operations. Because of that, the actual usage severity, in most cases, is less than predicted; therefore, there is no indication that C-17 airframes will be unable to meet or exceed the specified usage-based service life. However, future changes in C-17 operations/deployment strategies could have an adverse effect on service life and would need to be considered during service life analysis by factoring weighted hours using the methodology.

https://www.acq.osd.mil/pepolicy/pdfs/O ... Report.pdf

Now this report was released in Mar 2008 and you would expect that the recommendations factored in the start of the Iraq surge in 2007. It probably doesn't factor in the mass delivery of MRAPS from 2008-2013. Not sure how many of these 12000 were transported on C-17s and C-5s but would have to have been a decent percentage given the visibility. What is clear is that the GWOT mission to that date had not been significant as far as aircraft fatigue. They may have flown a lot of hours but those were not heavy fatigue inducing hours.

we also have the next quote,
For example, the Air Force Materiel Command has assessed that the C-17 program’s service life is 45,000 flight hours as opposed to the initial 30,000 flight hours projected by the original equipment manufacturer and PM based on fatigue and mission-type analysis


So a second reference to an AMC increase in expected service hours from that initial 30k to above 40k. Makes sense that in 2015 AMC then said 42k perhaps based on additional usage from ops during the later years of Iraq and Afghanistan.

texl1649 wrote:
I don’t see the cite showing an average per frame use in 2020 (or any year) of 18K hours. I am sure it is at/around 4 million flight hours overall, but surely the frames from the 90’s are well past that (likely well past 25K hours, and talk of ‘balancing’ wear on frames in the fleet is often a lot easier said than done.)

No one is claiming the average is sitting at 18k across the whole fleet, it is obviously nearly impossible given the span of deliveries. The USAF is very good at fleet management though, AMC would know the hours on every single aircraft and be able to rotate them through as required to minimise hours on high hour aircraft and maximise hours on low hour aircraft. It really isn't rocket science to manage the fleet this way.

texl1649 wrote:
My suspicion is that the USAF has no desire to highlight the need to SLEP/do anything to supplement the C-17 given the TACAIR and B-21 and KC-46 priorities in acquisition/funding the next 10 years. I don’t think that’s a tin foil hat theory, just a reality. It’s highly likely, imho, that as with the C-141 and C-5 fleets before it, some sort of cracks/serious structural issues will be ‘found’ in the older/higher time members of the C-17 fleet in the next 5 years, resulting in some being ‘temporarily’ sent to the desert.

That seems the wrong conclusion to draw from the data. The conclusion I draw is that the USAF doesn't need to talk about it because the USAF currently view the C-17 as being retired post 2040 which means they have more than ten years before they need to even start considering a replacement program. The C-5M is now expected to fly into the 2040s so there emerges an opportunity to replace both fleets with a single aircraft, if the respective requirements that both fleets cover can be met by one airframe.

texl1649 wrote:
I understand Gen. Everhart had expectations it would easily be done in 2016, but I am dubious as to his accuracy in this prognostication (how many flag officers really know the engineering/contracting costs likely in such a situation in advance?), and find the interest in fuel economy....particularly ironic given how long the USAF has flown certain engines on KC-135’s/707 frames (various flavors), B-52’s, C-5’s, E-4’s, C-141’s, etc. Fuel economy is often bantered about as a possible program justification driver, but rarely actually drives a timely upgrade (yes, eventually it happens, such as B-52/KC-135 sometimes). For goodness sakes, just look at the KC-46 they want to buy by the hundreds the next 10 years. Easily a 10 percent savings if they’d just tried to get a GEnX on it. The C-17 was simply not engineered to be fuel efficient (nor fast) relative to her civilian ‘peers.’

Finally, I’d note that at ASC/AFA meetings/discussions over the past actual 4 years, basically nothing has addressed long term sustainability of the Globemaster fleet. Sure, new HUD, Boeing taking over some of the maintenance contract (from L3), but it is anything but ‘on the radar’ vs. exciting stuff mentioned above, AFBMS etc.

Agree the engine upgrade may not occur, it obviously takes a lot to get an engine upgrade program through. You could also suggest that ASC/AFA talk the last few years hasn't focused on the C-17 because the KC-46 has taken a lot of time and discussion.

Buckeyetech wrote:
I can’t find the article, but I’m fairly confident there’s a single C-17 that surpassed 30,000 hours a couple years ago. Considering that most cargo TRANSCOM flies on milair, is not oversized, I feel like they can get the job done with with the KC-46’s coming online, and start retiring C-17s in large numbers in a decade or so from now.

No C-17s have flown 30k flight hours as far as I am aware. The highest C-17 was 91192, the sixth aircraft received in 1993, which passed 20k flight hours in 2013.

JB Charleston C-17 reaches 20,000 flight hours

The first C-17 Globemaster III to join the Air Force fleet, "The Spirit of Charleston," reached new heights recently by logging more than 20,000 flight hours.

...

https://www.amc.af.mil/News/Article-Dis ... ght-hours/

20 years of service, 20k flight hours so based on AMC expectations and it flying the same number of hours every year would serve until 2035. Given we know the USAF is managing the fleet I expect they will get longer out of it.


I just don’t see how a 2008 paper/data point, can project forward the net utilization after the intervening 12 years. I also don’t think it’s ok to just assume the aircraft can be easily extended via inspections/paperwork to 50% beyond their expected life, nor that utilization’s have in fact...been consistent with 1995-2005. Note that the people saying that in 2008, and 2015, won’t be handling such a program in 2025-35. Finally, much of that analyses was back when USAF was still buying C-17’s, but of course didn’t want Congress to force ‘too many’ into their future procurement budgets. Yes, politics, but again the TACAIR R&D and shiny new toys were/are priorities.

Yes, the C-5 has been a...longtime fixture. Again, it’s tough to really make that comparison though; it took over 20 years for the real C-5B program for the originals, and then of course the laborious C-5M program, and for several decades load planners scheduled 2 when 1 was needed to hope one would be mission capable that day. If anything, I’d note the C-141 and C-5 programs are an argument against...”well the C-17 will live a lot longer at current op tempo rates with just some increased maintenance past it’s projected/design service life.”

Agree to disagree, respectfully. And while I respect the USAF fleet management capabilities, I again think all of their types have a certain component, and more as the type gets older that are hangar queens. If merely 20-50 globemasters fit this description toward 2025-2030, and there is another major deployment on the other side of the world...it’s not something that could wait until 2040 to begin fielding a replacement, imho.

Anyway, it’s something I hope we get more data on.
 
Ozair
Posts: 5582
Joined: Mon Jan 31, 2005 8:38 am

Re: C-17 Usage

Mon Dec 21, 2020 1:05 am

texl1649 wrote:
I just don’t see how a 2008 paper/data point, can project forward the net utilization after the intervening 12 years. I also don’t think it’s ok to just assume the aircraft can be easily extended via inspections/paperwork to 50% beyond their expected life, nor that utilization’s have in fact...been consistent with 1995-2005.

C'mon texl1649, did you actually read the report I linked or just the quote? From the C-17 analysis on page 24,
The PM monitors the critical aircraft components and assesses severity of usage on
those components through the U.S. Air Force Aircraft Structural Integrity Program (ASIP), which
is a preventive maintenance program of regularly scheduled inspections and replacement or
repair of various elements of the airframe. This is accomplished on an aircraft by aircraft basis.
While the airframe is not experiencing a decrease in service life due to GWOT operations, the
critical aircraft components are experiencing accelerated wear and tear due to GWOT
operations. Exposure to the sand environment, extreme heat, evasive maneuvering, and
steeper takeoffs and landings contribute to the increased wear and tear on the components of
the aircraft, most notably the engine, landing gear, and flight controls. The wear and tear on
these subsystems is mitigated by maintenance and repair, which drives up maintenance and
repair/overhaul costs in order to maintain aircraft availability. In summary, the C-17 ASIP
manages the fleet and identifies maintenance on the aircraft as needed to ensure each aircraft
reaches its 30,000 hour service life.

Usage data at the asset level for C-17 aircraft is available in the Reliability and
Maintainability Information System (REMIS), which holds usage data for Air Force aircraft. The
C-17 program does not have an automated fatigue measurement tool that tracks fatigue on the
airframes, so an estimate of fatigue must be applied in the methodology when operational and
mission demands warrant that fatigue be incorporated within the calculation. Since the PMO
has determined that fatigue currently has not posed a threat to the service life of the C-17 fleet
since the aircraft are not operating beyond their design life operating boundaries, fatigue is
estimated to be zero. C-17 engineers have noted that in the future, based on changes in
mission profiles and operating conditions, fatigue could pose an impact on the service life and
an estimate of the impact would need to be incorporated in the methodology.


Predicting aircraft useful life is core business for the USAF. They have a fleet of legacy aircraft and have literally done this for generations. It isn't like AMC is coming in to this blind, they are the operator and maintainer of the aircraft and have been for 27 years. The C-17 PMO is actively monitoring the jet and was doing so in 2007 when this analysis was completed. I highly doubt that they have stopped doing this.

texl1649 wrote:
Note that the people saying that in 2008, and 2015, won’t be handling such a program in 2025-35.

A frankly stupid statement. What you asserting is that these people didn't do their jobs, or deliberately misrepresented, because they felt they wouldn't be around in that timeframe to take the flak for it. The same could be said for the pilots flying the aircraft, they must be deliberately overstressing the jet because they don't care about the pilots who will fly the aircraft after them, or the people who built the aircraft didn't do a good job because they were never going to have to fly in it. I don't work that way nor have I worked with people who have that mindset. I expect you would be insulted if someone suggested the same thing to you and I see absolutely no justification for claiming that these people had those considerations in mind at the time.

texl1649 wrote:
Finally, much of that analyses was back when USAF was still buying C-17’s, but of course didn’t want Congress to force ‘too many’ into their future procurement budgets. Yes, politics, but again the TACAIR R&D and shiny new toys were/are priorities.

This point is irrelevant. Whether the USAF was receiving aircraft or not doesn't matter to their estimation of how long the aircraft will be able to function. The USAF ended up with significantly more aircraft than they expected so not sure why having more aircraft would be a bad thing for predicting and managing overall fleet life and hours.

texl1649 wrote:
Yes, the C-5 has been a...longtime fixture. Again, it’s tough to really make that comparison though; it took over 20 years for the real C-5B program for the originals, and then of course the laborious C-5M program, and for several decades load planners scheduled 2 when 1 was needed to hope one would be mission capable that day. If anything, I’d note the C-141 and C-5 programs are an argument against...”well the C-17 will live a lot longer at current op tempo rates with just some increased maintenance past it’s projected/design service life.”

Yet the C-141 did continue on long past its initial planned service date and hour usage with the fleet getting a SLEP. The C-17 is a more useful jet to the USAF than the C-141 given its cargo dimensions. The C-5 is a unique aircraft and I doubt the USAF will ever operate a similar sized aircraft again in the transport role, it would be hard to visualise a program for 60 to 80 aircraft to cover its replacement.

texl1649 wrote:
Agree to disagree, respectfully. And while I respect the USAF fleet management capabilities, I again think all of their types have a certain component, and more as the type gets older that are hangar queens.

Without evidence to support your position though it isn't really respect. Instead of accepting the USAF and their fleet management capabilities, including references, you are basically saying you know best and they don't know what they are doing.

Fleet management isn't just a USAF thing. It is common across militaries around the globe whether it is tanks, ships or aircraft. The USN makes the same analysis on their DDGs, the US Army on their Abrams fleet. In the case of the USAF and the C-17 we know the fleet hasn't been used anywhere near as much in the way it was envisioned. The same with fighter jets where going on operations instead of training has significantly extended the life of a number of aircraft, such as the classic Hornet. The RAAF have flown and managed their fleet to have aircraft capable of surviving out to 2023 before replacement by the F-35. The lower hour aircraft were sold to the Canadians to help them spread their fleet out. A significant benefit for the extension of the RAAF aircraft, out to 6000 hours, was their use on operations in the Middle East. Flying ops actually preserved fatigue in the aircraft compared to Australian based training. Some USMC Hornets have flown more than 10000 hours and a large reason for that is their time on ops. Compare that to the Swiss or the Finnish Air Forces with their Hornet fleets. The Finns have a life expectancy on their aircraft of 4500 hours. That is lower than almost any other operator and related to the fact the Finns have little ops work and spend alot of time training, doing high fatigue BFM.

Again, we know for a fact that while hours were high on the C-17 fleet the loads and missions types weren't as fatigue inducting as the designers had planned, that strongly lends to the aircraft being able to extend beyond the planned service hours.

texl1649 wrote:
If merely 20-50 globemasters fit this description toward 2025-2030, and there is another major deployment on the other side of the world...it’s not something that could wait until 2040 to begin fielding a replacement, imho.

So really the USAF are dammed if they do and dammed if they don't. Start a replacement now and then get told they are wasting money as the C-17 can continue on for longer or don't start a replacement and the sky falling in brigade will denounce them as foolish. If the USAF went into a major conflict today or ten years from now hours on the C-17 wouldn't matter. Aircraft in large national survival conflicts fly as long and as hard as they need to and if that does happen then defence budgets will adjust to compensate. I expect were the US to go to war with China tomorrow the day after there would be an order with Boeing for 200 strategic airlifters, the first of which needs to be delivered two years from now.

texl1649 wrote:
Anyway, it’s something I hope we get more data on.

I'm not sure what additional data we need. We have a very close assumption on total fleet hours to date, we have AMC statements on expected total flight hours, we have statements about what types of missions the aircraft has flown and their impact on fatigue. Other than knowing the number of aircraft above 20K flight hours or specific hours per frame what else do you want to know?
 
RJMAZ
Posts: 2481
Joined: Sat Jul 09, 2016 2:54 am

Re: C-17 Usage

Mon Dec 21, 2020 4:03 am

Tactical max effort takeoff and landings involve high G loads and a high sink rate when landing.

In Afghanistan and Iraq the enemy would want to sit under the flight path with all kinds of weapons. To reduce risk the transport aircraft would approach from a random direction, turn hard and descend quickly. When leaving it would rapidly climb and do a hard turn. This significantly reduces the risk of enemy fire and the protection radius required around the airport.

A pair of these hard turns could provide aircraft fatigue equivalent to a dozen normal flight hours. The high descent rate will mean the average sink rate when hitting the ground will be higher than normal. One average tactical landing might have the same fatigue growth as multiple normal landings from safe and long runways. The USAF C-17 fleet were flying into these dangerous airports on a regular basis. The C-5M were flying into safer airports where they could do gentle landings.

Then in terms of engines you have extra wear. Not only from sand but higher emergency power levels are often used. For instance with the RAAF C-130J aircraft they were using max effort takeoff for nearly every takeoff. Engine wear at these power levels are many times higher than normal.

The USAF would no doubt have strain gauges on their C-17 aircraft monitoring fatigue. I'm sure if there was no conflict for another 20 years the C-17 fleet could have a gentle and extended life. The USAF always plan for a worse case scenario. Another Afghanistan style conflict could see the C-17 fleet rapidly use up their remaining fatigue life in a fraction of the planned time. Like with the F-15EX purchase they will never get caught lacking in capability. The USAF will order a replacement or supplement.
 
texl1649
Posts: 1956
Joined: Thu Aug 02, 2007 5:38 am

Re: C-17 Usage

Mon Dec 21, 2020 1:02 pm

Ozair wrote:
texl1649 wrote:
I just don’t see how a 2008 paper/data point, can project forward the net utilization after the intervening 12 years. I also don’t think it’s ok to just assume the aircraft can be easily extended via inspections/paperwork to 50% beyond their expected life, nor that utilization’s have in fact...been consistent with 1995-2005.

C'mon texl1649, did you actually read the report I linked or just the quote? From the C-17 analysis on page 24,
The PM monitors the critical aircraft components and assesses severity of usage on
those components through the U.S. Air Force Aircraft Structural Integrity Program (ASIP), which
is a preventive maintenance program of regularly scheduled inspections and replacement or
repair of various elements of the airframe. This is accomplished on an aircraft by aircraft basis.
While the airframe is not experiencing a decrease in service life due to GWOT operations, the
critical aircraft components are experiencing accelerated wear and tear due to GWOT
operations. Exposure to the sand environment, extreme heat, evasive maneuvering, and
steeper takeoffs and landings contribute to the increased wear and tear on the components of
the aircraft, most notably the engine, landing gear, and flight controls. The wear and tear on
these subsystems is mitigated by maintenance and repair, which drives up maintenance and
repair/overhaul costs in order to maintain aircraft availability. In summary, the C-17 ASIP
manages the fleet and identifies maintenance on the aircraft as needed to ensure each aircraft
reaches its 30,000 hour service life.

Usage data at the asset level for C-17 aircraft is available in the Reliability and
Maintainability Information System (REMIS), which holds usage data for Air Force aircraft. The
C-17 program does not have an automated fatigue measurement tool that tracks fatigue on the
airframes, so an estimate of fatigue must be applied in the methodology when operational and
mission demands warrant that fatigue be incorporated within the calculation. Since the PMO
has determined that fatigue currently has not posed a threat to the service life of the C-17 fleet
since the aircraft are not operating beyond their design life operating boundaries, fatigue is
estimated to be zero. C-17 engineers have noted that in the future, based on changes in
mission profiles and operating conditions, fatigue could pose an impact on the service life and
an estimate of the impact would need to be incorporated in the methodology.


Predicting aircraft useful life is core business for the USAF. They have a fleet of legacy aircraft and have literally done this for generations. It isn't like AMC is coming in to this blind, they are the operator and maintainer of the aircraft and have been for 27 years. The C-17 PMO is actively monitoring the jet and was doing so in 2007 when this analysis was completed. I highly doubt that they have stopped doing this.

texl1649 wrote:
Note that the people saying that in 2008, and 2015, won’t be handling such a program in 2025-35.

A frankly stupid statement. What you asserting is that these people didn't do their jobs, or deliberately misrepresented, because they felt they wouldn't be around in that timeframe to take the flak for it. The same could be said for the pilots flying the aircraft, they must be deliberately overstressing the jet because they don't care about the pilots who will fly the aircraft after them, or the people who built the aircraft didn't do a good job because they were never going to have to fly in it. I don't work that way nor have I worked with people who have that mindset. I expect you would be insulted if someone suggested the same thing to you and I see absolutely no justification for claiming that these people had those considerations in mind at the time.

texl1649 wrote:
Finally, much of that analyses was back when USAF was still buying C-17’s, but of course didn’t want Congress to force ‘too many’ into their future procurement budgets. Yes, politics, but again the TACAIR R&D and shiny new toys were/are priorities.

This point is irrelevant. Whether the USAF was receiving aircraft or not doesn't matter to their estimation of how long the aircraft will be able to function. The USAF ended up with significantly more aircraft than they expected so not sure why having more aircraft would be a bad thing for predicting and managing overall fleet life and hours.

texl1649 wrote:
Yes, the C-5 has been a...longtime fixture. Again, it’s tough to really make that comparison though; it took over 20 years for the real C-5B program for the originals, and then of course the laborious C-5M program, and for several decades load planners scheduled 2 when 1 was needed to hope one would be mission capable that day. If anything, I’d note the C-141 and C-5 programs are an argument against...”well the C-17 will live a lot longer at current op tempo rates with just some increased maintenance past it’s projected/design service life.”

Yet the C-141 did continue on long past its initial planned service date and hour usage with the fleet getting a SLEP. The C-17 is a more useful jet to the USAF than the C-141 given its cargo dimensions. The C-5 is a unique aircraft and I doubt the USAF will ever operate a similar sized aircraft again in the transport role, it would be hard to visualise a program for 60 to 80 aircraft to cover its replacement.

texl1649 wrote:
Agree to disagree, respectfully. And while I respect the USAF fleet management capabilities, I again think all of their types have a certain component, and more as the type gets older that are hangar queens.

Without evidence to support your position though it isn't really respect. Instead of accepting the USAF and their fleet management capabilities, including references, you are basically saying you know best and they don't know what they are doing.

Fleet management isn't just a USAF thing. It is common across militaries around the globe whether it is tanks, ships or aircraft. The USN makes the same analysis on their DDGs, the US Army on their Abrams fleet. In the case of the USAF and the C-17 we know the fleet hasn't been used anywhere near as much in the way it was envisioned. The same with fighter jets where going on operations instead of training has significantly extended the life of a number of aircraft, such as the classic Hornet. The RAAF have flown and managed their fleet to have aircraft capable of surviving out to 2023 before replacement by the F-35. The lower hour aircraft were sold to the Canadians to help them spread their fleet out. A significant benefit for the extension of the RAAF aircraft, out to 6000 hours, was their use on operations in the Middle East. Flying ops actually preserved fatigue in the aircraft compared to Australian based training. Some USMC Hornets have flown more than 10000 hours and a large reason for that is their time on ops. Compare that to the Swiss or the Finnish Air Forces with their Hornet fleets. The Finns have a life expectancy on their aircraft of 4500 hours. That is lower than almost any other operator and related to the fact the Finns have little ops work and spend alot of time training, doing high fatigue BFM.

Again, we know for a fact that while hours were high on the C-17 fleet the loads and missions types weren't as fatigue inducting as the designers had planned, that strongly lends to the aircraft being able to extend beyond the planned service hours.

texl1649 wrote:
If merely 20-50 globemasters fit this description toward 2025-2030, and there is another major deployment on the other side of the world...it’s not something that could wait until 2040 to begin fielding a replacement, imho.

So really the USAF are dammed if they do and dammed if they don't. Start a replacement now and then get told they are wasting money as the C-17 can continue on for longer or don't start a replacement and the sky falling in brigade will denounce them as foolish. If the USAF went into a major conflict today or ten years from now hours on the C-17 wouldn't matter. Aircraft in large national survival conflicts fly as long and as hard as they need to and if that does happen then defence budgets will adjust to compensate. I expect were the US to go to war with China tomorrow the day after there would be an order with Boeing for 200 strategic airlifters, the first of which needs to be delivered two years from now.

texl1649 wrote:
Anyway, it’s something I hope we get more data on.

I'm not sure what additional data we need. We have a very close assumption on total fleet hours to date, we have AMC statements on expected total flight hours, we have statements about what types of missions the aircraft has flown and their impact on fatigue. Other than knowing the number of aircraft above 20K flight hours or specific hours per frame what else do you want to know?


You’ve cited nothing more current than 2016 and then dismissed any concern about the actual aging/utilization as unfounded, and disrespectful? LOL, ok, whatever. Politics in 2008-2010 is pertinent in how the USAF wanted to portray long term Globemaster use, as they didn’t want it to become simply a jobs program (though, notably, it was in the wrong state for this to really happen, Boeing certainly wanted to keep the cash spigot open).

As per the post above, you’re just wrong to dismiss how the aircraft has been used/abused the past 10 years in USAF service. I don’t really care if you disagree, it’s fine, it’s an Internet forum. Your note on the C-141 managing a long life neglects how outdated it was, and how much actual work went into fixing/even lengthening those frames to get that life. Of course, it’s a tangent we don’t need to go down, but the aircraft had a complementary capability, with a much lower capability to carry outsize cargo.

The tirade/tangent about tactical aircraft going a few thousand hours longer is just that; it’s a different bird; apples to oranges. Inspections are simpler, it’s smaller, known stress points can be checked easily, and the fleet balanced more easily. Particularly for the growlers, they can be flown in ‘lower stress’ manners than perhaps a ‘top gun’ aggressor frame might be handled on an annual basis. Anyway; I’m not trying to disparage the USAF (or others) at all, but rather asserting that we don’t, actually, know the real total hours per frame/average today, nor the impact of their use the past 10 years. Relying on an analysis from 2008, or 2015 (likely based on 2013 or so data)...misses a lot of abuse.

The USAF should I think realize, after the ‘tanker wars’ of the past 30 years to get a KC-135 replacement into service in numbers, that the Globemaster replacement won’t take just 5 years or so to develop, but likely a 10-15 year process. Beginning, and budgeting for this (wonderful if a sister variant could also do the Galaxy replacement), a la US Army FVL programs makes abundant sense, unless in fact the average aircraft really does have only around 15-20K hours (without more stress per RJMAZ and I have asserted) and a simple replacement is to be planned. It is ‘damned if you don’t’ I guess, but ‘fail to plan and you are planning to fail’ is a more apt saying. (BTW, it would be nice if this notional program could also have a tanker variant someday.)

I don’t see the current data on that on the internet, nor certainly this thread. I don’t think it’s ‘classified’ but believe more would need to be known, including from the contractor supporting the fleet (which is again just changing back to Boeing) and AMC, to conclude otherwise.
 
GalaxyFlyer
Posts: 8576
Joined: Fri Jan 01, 2016 4:44 am

Re: C-17 Usage

Mon Dec 21, 2020 4:16 pm

The C-5M were flying into safer airports where they could do gentle landings.


That’s unintentionally hilarious. You haven’t ridden thru some of the arrivals I have in Sky Pig.
 
Ozair
Posts: 5582
Joined: Mon Jan 31, 2005 8:38 am

Re: C-17 Usage

Mon Dec 21, 2020 10:03 pm

texl1649 wrote:
You’ve cited nothing more current than 2016 and then dismissed any concern about the actual aging/utilization as unfounded, and disrespectful? LOL, ok, whatever.

The question is what tactical changes have occurred between when the report I have cited was published and today.

From the report
Currently, the C-17 airframes are not experiencing operational usage or fatigue that impacts their ability to achieve the 30,000 hour service lives. The missions that are flown are within the design assumptions/parameters of the aircraft. More specifically, the airframe was designed to withstand a higher percentage of airdrop, assault landing, and low level missions than has been experienced during C-17 operations. Because of that, the actual usage severity, in most cases, is less than predicted; therefore, there is no indication that C-17 airframes will be unable to meet or exceed the specified usage-based service life. However, future changes in C-17 operations/deployment strategies could have an adverse effect on service life and would need to be considered during service life analysis by factoring weighted hours using the methodology.


So we have a fact released in May 2008 which states the USAF C-17 was not operating missions that were fatigue inducing compared to predictions when the aircraft was built. Those predictions factored in, as it states above, more airdrop, assault landing and low level missions.
Despite RJMAZ's claim
RJMAZ wrote:
The USAF C-17 fleet were flying into these dangerous airports on a regular basis.
we have an official report that actually states the opposite, that it wasn't occurring as frequently as expected.

So what tactical changes have occurred? What significant effort was conducted between 2008 and 2016 that would have fatigue impacted the fleet? Iraq and Afghanistan had a whole bunch of MRAPS delivered which would not have been delivered via assault landing so no serious impact on the fleet. No other major incidents present themselves, the air threat in both Afghanistan and Iraq has actually lessoned in that period than increased. Really then the C-17 work would have been business as usual and consistent with the previous ten years. We also know from fleet numbers that the number of hours on the fleet reduced post 2010 as they did one million between 2006 and 2010 with the next million, with more aircraft, took five years. That doesn't speak to more fatigue across the fleet...

How about post 2014 with ISIS? That conflict saw little forward deployed C-17s compared to other USAF airframes conducting strikes against ISIS positions and supporting foreign ground troops. Likely little impact on the fleet from a fatigue perspective and the total fleet hours didn't increase as stated above any more than had been consistent

Anything else happen globally between 2014 and 2020 that would have significantly impacted C-17 fatigue? In that context then, we know AMC expected the C-17 to be capable of 45k flight hours in 2008 and changed that to 42k in 2015.

In the absence of evidence that neither you are RJMAZ have provided what else do we have to go on except what I have referenced?

texl1649 wrote:
Politics in 2008-2010 is pertinent in how the USAF wanted to portray long term Globemaster use, as they didn’t want it to become simply a jobs program (though, notably, it was in the wrong state for this to really happen, Boeing certainly wanted to keep the cash spigot open).

The politics of 2008-2010 has no bearing on the fatigue of the aircraft. This whole discussion is about how much fatigue the fleet has accrued and whether this will impact them going past 30k flight hours.

texl1649 wrote:
As per the post above, you’re just wrong to dismiss how the aircraft has been used/abused the past 10 years in USAF service. I don’t really care if you disagree, it’s fine, it’s an Internet forum.

I can disagree because I have provided references to support my position. As asked above, provide some supporting reference that supports your claim about higher or greater fatigue inducing usage.

texl1649 wrote:
The tirade/tangent about tactical aircraft going a few thousand hours longer is just that; it’s a different bird; apples to oranges. Inspections are simpler, it’s smaller, known stress points can be checked easily, and the fleet balanced more easily. Particularly for the growlers, they can be flown in ‘lower stress’ manners than perhaps a ‘top gun’ aggressor frame might be handled on an annual basis. Anyway; I’m not trying to disparage the USAF (or others) at all, but rather asserting that we don’t, actually, know the real total hours per frame/average today, nor the impact of their use the past 10 years. Relying on an analysis from 2008, or 2015 (likely based on 2013 or so data)...misses a lot of abuse.

Actually the reference to fighter aircraft is pertinent. It shows how actual operations impact on aircraft fatigue. We know from my reference that the C-17 was doing less fatigue inducing flights than expected up to 2008. Why would the post 2008 timeframe be any different and why then wouldn't that less fatigue than expected translate to the potential for greater flight hours? Why is a fighter fleet easier to balance than a transport fleet?

texl1649 wrote:
The USAF should I think realize, after the ‘tanker wars’ of the past 30 years to get a KC-135 replacement into service in numbers, that the Globemaster replacement won’t take just 5 years or so to develop, but likely a 10-15 year process. Beginning, and budgeting for this (wonderful if a sister variant could also do the Galaxy replacement), a la US Army FVL programs makes abundant sense, unless in fact the average aircraft really does have only around 15-20K hours (without more stress per RJMAZ and I have asserted) and a simple replacement is to be planned. It is ‘damned if you don’t’ I guess, but ‘fail to plan and you are planning to fail’ is a more apt saying. (BTW, it would be nice if this notional program could also have a tanker variant someday.)

I am not opposed to replacing the C-17 but I am opposed to claims with no facts to support them on the early demise of the aircraft. As far as how long a replacement will take, that all depends on the requirements. If the USAF want a direct C-17, with the rough field capabilities that aircraft has, then the program may take some additional time. What we can be certain is that the USAF won't accept a lower payload given there will remain the requirement to transport US Army vehicles.
 
RJMAZ
Posts: 2481
Joined: Sat Jul 09, 2016 2:54 am

Re: C-17 Usage

Tue Dec 22, 2020 12:02 am

Ozair wrote:
We have an official report that actually states the opposite, that it wasn't occurring as frequently as expected.

So what tactical changes have occurred? What significant effort was conducted between 2008 and 2016 that would have fatigue impacted the fleet?

I never said the C-17 is working harder than intended. It simply works harder than the C-5. As I stated all previous life extension program came with tactical changes such as G limits to reduce fatigue. As soon as fatigue limits are applied to the C-17 it will no longer be able to do max effort takeoff and landings. The fleet is then put at greater risk to enemy fire in future conflicts.

Multiple USAF C-17 aircraft have exceeded 25,000 hours. The first C-17 hit 20,000 flight hours in December 2013. Around half the fleet has since hit 20,000 hours. The design life is 30,000 hours.

The USAF has four options with the C-17:

1) An expensive life extension program. Multiple
large parts deep inside the frame will need to be replaced. The aircraft can continue to do max effort tactical work beyond 2040.

2) A cheap life extension program. Very few parts are changed. Instead the usage is severely restricted. 2.25G limit applied. Restrictions on payload weight is applied to reduce wing root bending. Reduced thrust takeoffs become mandatory to increase engine life. Austere work is only for emergencies.

3) Retire the full fleet and do a full replacement starting in 2030 at the earlist or 2035 at the latest. A cleansheet design would probably need to launch in a few years. An improved C-2 would be the obvious choice.

4) Do the cheap life extension to a portion of the C-17 fleet so they can continue to do strategic work but then get a supplement. The USAF does not have the C-130J-30 with the extra cargo length. A big order of these with some newer performance tweaks added could work.
 
Ozair
Posts: 5582
Joined: Mon Jan 31, 2005 8:38 am

Re: C-17 Usage

Tue Dec 22, 2020 1:04 am

RJMAZ wrote:
Ozair wrote:
We have an official report that actually states the opposite, that it wasn't occurring as frequently as expected.

So what tactical changes have occurred? What significant effort was conducted between 2008 and 2016 that would have fatigue impacted the fleet?

I never said the C-17 is working harder than intended. It simply works harder than the C-5.

The inference was there multiple times and it clearly isn’t only me thinking that was your intent.
texl1649 wrote:
(without more stress per RJMAZ and I have asserted)


RJMAZ wrote:
As I stated all previous life extension program came with tactical changes such as G limits to reduce fatigue. As soon as fatigue limits are applied to the C-17 it will no longer be able to do max effort takeoff and landings. The fleet is then put at greater risk to enemy fire in future conflicts.

What SLEP has occurred which resulted in a G limit reduction? AMC and the C-17 PMO track fatigue and have placed no limits on the C-17 flying out past its current design limit.

RJMAZ wrote:
Multiple USAF C-17 aircraft have exceeded 25,000 hours. The first C-17 hit 20,000 flight hours in December 2013. Around half the fleet has since hit 20,000 hours. The design life is 30,000 hours.

Yes I provided most of those numbers. AMC in 2015 stated the aircraft will go to 42k flight hours past the original planned 30k flight hours. Given the USAF has many large and small aircraft that are flying past their design life limit today I don’t see what the issue is.

RJMAZ wrote:
The USAF has four options with the C-17:

1) An expensive life extension program. Multiple
large parts deep inside the frame will need to be replaced. The aircraft can continue to do max effort tactical work beyond 2040.

2) A cheap life extension program. Very few parts are changed. Instead the usage is severely restricted. 2.25G limit applied. Restrictions on payload weight is applied to reduce wing root bending. Reduced thrust takeoffs become mandatory to increase engine life. Austere work is only for emergencies.

3) Retire the full fleet and do a full replacement starting in 2030 at the earlist or 2035 at the latest. A cleansheet design would probably need to launch in a few years. An improved C-2 would be the obvious choice.

4) Do the cheap life extension to a portion of the C-17 fleet so they can continue to do strategic work but then get a supplement. The USAF does not have the C-130J-30 with the extra cargo length. A big order of these with some newer performance tweaks added could work.

You forgot option 5, understand that the fleet can fly to 42k flight hours and therefore not have to make this decision for another ten years or with good fleet management even further. If 42k is the new design life then
 
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kitplane01
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Re: C-17 Usage

Tue Dec 22, 2020 9:33 am

RJMAZ wrote:
A pair of these hard turns could provide aircraft fatigue equivalent to a dozen normal flight hours. .


This seems QUITE unlikely but I’m willing to be educated. Can your provide a source for this claim?
 
texl1649
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Re: C-17 Usage

Tue Dec 22, 2020 1:33 pm

Adding some more inconvenient facts relative to C-17 USAF utilization. In 2017 USAF awarded an extra 7.1 Billion to Boeing for C-17 sustainment due to increased utilization.

https://www.defense.gov/Newsroom/Contra ... e/1278194/

Boeing Co., Huntington Beach, California, has been awarded a $7,127,000,000 increase in indefinite-delivery/indefinite-quantity ceiling with modification (P00041) to a previously awarded contract for C-17 sustainment due to increase in fleet and number operating bases. Work will be performed worldwide and is expected to be completed Sept. 30, 2021. No funds are being obligated at the time of this modification. Air Force Life Cycle Management Center, C-17 Contracting Branch, Robins Air Force Base, Georgia, is the contracting activity (FA8526-12-D-0001).


Then, Boeing won in 2020 the trainer/logistics contract for the fleet. This is now run, notably, along/among their commercial ones. This dovetails into their maintenance contract (10 year award) which is incentive based; they’ve reported 40 percent savings in the maintenance side (which they’re paid to hit).

https://www.airforcemag.com/Boeing-Reca ... -Contract/

Speaking to Air Force Magazine on Monday at the Farnborough International Air Show here, Ed Dolanski, president of US Government Services for Boeing Global Services, said the six and a half year, $986 million contract to replace all of the Air Force’s C-17 trainers was a “very meaningful award.”

Boeing has had a performance-based logistics contract to sustain USAF’s C-17 fleet for more than a decade. During that time, the company has “reduced support dollars for aircraft by 40 percent while maintaining best in class mission capability of 81 percent or greater,” said Dolanski.

Now, with the new trainer contract, Boeing can simultaneously make modifications to both the airframe and the trainer, ensuring USAF C-17 operators always have the most up-to-date training available to them, he said. The contract award also opens the door to potential international deals.

“We paid really close attention to how we could bring value to this one. We understand the airframe very, very well,” said Dolanski. “What changed this time, is this more streamlined and agile approach to how we run services.”


Anything related to Boeing on a.net draws a slew of skepticism I think, right or wrong, but I think it’s safe to say ‘excess’ maintenance has not been performed on the aircraft.

Now, what I don’t understand is how the original award was for $2 billion from 2013-2017 for maintenance to hit a mission readiness goal, but the 2017 supplement was for an extra $7 billion while the aircraft was being ‘not over-used vs. projections’ and yet Boeing is killing the mission capable rate and nothing is breaking/wearing out abnormally. Notably, this also covers a lot of international users (26 additional frames?) so not all of this award is USAF-related.

https://www.defenseworld.net/news/7695/ ... -H1DS1HafA

Boeing has won a $2 billion follow-on contract from the U.S Department of Defense for the C-17 Globemaster III Integrated Sustainment Program (GISP). The program provides support services such as forecasting, purchasing and material management for the C-17 and all C-17-unique support. This Performance-Based Logistics (PBL) program, which started in 1998 with 42 aircraft, now covers 246 worldwide. It provides lower costs through economies of scale from supporting the entire global fleet. The latest contract covers fiscal years 2013 through 2017. Under a PBL arrangement, a customer receives an agreed-to level of system readiness, as opposed to a traditional contract for specific spare parts and support services. This integrated logistics approach – in which Boeing manages U.S. assets as a designated Inventory Control Point – has allowed Boeing to apply innovative spares forecasting and modeling tools to maximize aircraft availability while lowering costs. “This contract award and the recognition from the secretary of defense are testaments to the long-standing partnership between the U.S. Air Force and Boeing,” said Gus Urzua, Boeing vice president and GISP program manager.
 
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bikerthai
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Re: C-17 Usage

Tue Dec 22, 2020 1:39 pm

kitplane01 wrote:
RJMAZ wrote:
A pair of these hard turns could provide aircraft fatigue equivalent to a dozen normal flight hours. .


This seems QUITE unlikely but I’m willing to be educated. Can your provide a source for this claim?


Not necessarily a hard turn but sudden heavy turbulence would also do it.

The principle of fatigue life is complicated you may want to look up some publications. It may be hard to follow but you can think of it like this.

Fatigue life is based on crack growth. A crack will grow if the load at the crack reach some critical factor. So, if during regular flight, if the load at that location does not pass that factor, you can basically have for all practical purpose, unlimitted life.

However during a ground-air-ground cycle, you expect to have loads beyond this critical value but still way below the limit load of the aircraft. This would occur during rough turbulence or hard maneuver.

How fast the crack grows depends how much past critical your load. The cumulation of these crack growths determines the fatigue life of an aircraft.

As you can surmise, the growth may not be linear with applied load. Someone will have to back me ip on that. So if you have one hard maneuver or a hard landing that put the airplane near limit load, you may have eaten up the fatigue life of dozens if not hundreds of uneventful regular flights.

There are some publications out there. Look up GAG life cycle.

bt
 
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bikerthai
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Re: C-17 Usage

Tue Dec 22, 2020 1:51 pm

texl1649 wrote:
Now, what I don’t understand is how the original award was for $2 billion from 2013-2017 for maintenance to hit a mission readiness goal, but the 2017 supplement was for an extra $7 billion while the aircraft was being ‘not over-used vs. projections’ and yet Boeing is killing the mission capable rate and nothing is breaking/wearing out abnormally.


Another factor is as the planes gets older, it will cost exponentially more to keep the same capabilities. Example, increased inspection cycles for crack growth etc.

bt
 
Ozair
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Re: C-17 Usage

Tue Dec 22, 2020 8:22 pm

texl1649 wrote:
Adding some more inconvenient facts relative to C-17 USAF utilization. In 2017 USAF awarded an extra 7.1 Billion to Boeing for C-17 sustainment due to increased utilization.

https://www.defense.gov/Newsroom/Contra ... e/1278194/

Then, Boeing won in 2020 the trainer/logistics contract for the fleet. This is now run, notably, along/among their commercial ones. This dovetails into their maintenance contract (10 year award) which is incentive based; they’ve reported 40 percent savings in the maintenance side (which they’re paid to hit).

https://www.airforcemag.com/Boeing-Reca ... -Contract/


Anything related to Boeing on a.net draws a slew of skepticism I think, right or wrong, but I think it’s safe to say ‘excess’ maintenance has not been performed on the aircraft.

Now, what I don’t understand is how the original award was for $2 billion from 2013-2017 for maintenance to hit a mission readiness goal, but the 2017 supplement was for an extra $7 billion while the aircraft was being ‘not over-used vs. projections’ and yet Boeing is killing the mission capable rate and nothing is breaking/wearing out abnormally. Notably, this also covers a lot of international users (26 additional frames?) so not all of this award is USAF-related.

https://www.defenseworld.net/news/7695/ ... -H1DS1HafA

I don't think any of the above infers greater utilization compared to previous years, For example were utilization that much greater then the fleet as a whole would have hit four million hours already wouldn't it?

I also would read a lot into the contract values, as BT suggests as the aircraft ages it will have points where greater maintenance is required. It is also interesting to add this additional news release on the upcoming contract to replace the one you mentioned,

Boeing signs MoU for USAF C-17 fleet sustainment

Boeing has signed a memorandum of understanding (MoU) to continue the sustainment of the US Air Force’s (USAF) C-17 Globemaster III military transport aircraft fleet into the next decade.

The MoU was signed with the C-17 System Program Office (SPO) at Robins Air Force Base, Georgia, on 21 August.

...

https://www.airforce-technology.com/new ... ustainment

The value of the above award is potentially up to US$23.76 billion... although no specific timeframe is indicated.

We have Canada being approved for a sustainment contract just this December for US$275 million. https://www.dsca.mil/press-media/major- ... ustainment although no timeframe is indicated.
 
Ozair
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Re: C-17 Usage

Tue Dec 22, 2020 8:45 pm

Another sustainment link which shows how well the USAF is maintaining and is able to maintain the aircraft,

C-17 Integrated Sustainment Public/Private Partnership extension

...

Boeing guarantees C-17 aircraft availability. The C-17 continues to have one of the best Mission Capable Rates and Cost per Flight Hour rates in the Air Force inventory, at 80+% (consistent since 2003) and ~$24.4K per flight hour. Specification for the C-17 is no more than 18 maintenance man-hours per flight hour, but the USAF is performing at a superior level of five maintenance man-hours per flight hour. Thus, the C-17 is available for new missions sooner and more often compared to other fleets.

...

https://www.sachamber.org/wp-content/up ... 7-GISP.pdf

While I'm not sure on the accuracy of the above claim if the USAF does have the maintenance man hours down to five per flight hour that is a great achievement and shows why the USAF love the jet so much.
 
RJMAZ
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Re: C-17 Usage

Tue Dec 22, 2020 10:38 pm

bikerthai wrote:
Another factor is as the planes gets older, it will cost exponentially more to keep the same capabilities. Example, increased inspection cycles for crack growth etc.

I couldn't have said it better.

I will add some more detail for other members. Finding fatigue cracking is normal. The manufacturer will then develop a repair. Cracking from fastener holes will involve the hole being redrilled, then eddy current tested to make sure the crack is gone and an oversized fastener is fitted. Plate surface cracks can also have strengthening added which can be bonded, bolted or supersonic particle deposition.

The goal of a full scale fatigue test is to help the manufacturer find the locations of cracking but also determine the max allowable crack length at each location. Today they can use software to calculate the stress concentrations to give a list of areas to visually inspect. Once a large crack is found on a single aircraft then the entire fleet will be inspected at that location. Strengthening can be added before the area becomes a problem.

As the aircraft gets older, the inspections increase and the number of repairs increase exponentially. These repairs are effectively like micro life extension programs and can cost millions of dollars per repair. Eventually the cost becomes so high that it is better to retire the aircraft or change its usage.

A C-17 flying empty could pull 3G and it would have less fatigue growth than when fully loaded pulling 2.5G. G limits have to change for different payload weights. When pulling 2.5G the 70t of payload actually weighs 175t. A C-17 that hits 2.25G once per flight would have a fraction of the fatigue growth or service life of a C-17 that hits 2.5G 10 times per flight.

I do not think the USAF will accept strict G limits to extend the life and reduce maintenance. That is like saying a fighter jet can't turn. The greatest strength of the C-17 is its tactical performance and any G limits kills that capability.
 
GalaxyFlyer
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Re: C-17 Usage

Wed Dec 23, 2020 4:16 am

I’d be real surprised if any C-17 is even infrequently pulling over 2Gs, even tactical arrivals aren’t very high G maneuvers being at approach speeds. They were built to the normal 2.25G standard for transport category planes. The AF has and will accept all kinds of restrictions needed for fatigue life. They did on the -141s, on many fighters as they aged out like the longer on cracking on F-15s.
 
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kitplane01
Topic Author
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Re: C-17 Usage

Wed Dec 23, 2020 7:34 am

bikerthai wrote:
kitplane01 wrote:
RJMAZ wrote:
A pair of these hard turns could provide aircraft fatigue equivalent to a dozen normal flight hours. .


This seems QUITE unlikely but I’m willing to be educated. Can your provide a source for this claim?


Not necessarily a hard turn but sudden heavy turbulence would also do it.

The principle of fatigue life is complicated you may want to look up some publications. It may be hard to follow but you can think of it like this.

Fatigue life is based on crack growth. A crack will grow if the load at the crack reach some critical factor. So, if during regular flight, if the load at that location does not pass that factor, you can basically have for all practical purpose, unlimitted life.

However during a ground-air-ground cycle, you expect to have loads beyond this critical value but still way below the limit load of the aircraft. This would occur during rough turbulence or hard maneuver.

How fast the crack grows depends how much past critical your load. The cumulation of these crack growths determines the fatigue life of an aircraft.

As you can surmise, the growth may not be linear with applied load. Someone will have to back me ip on that. So if you have one hard maneuver or a hard landing that put the airplane near limit load, you may have eaten up the fatigue life of dozens if not hundreds of uneventful regular flights.

There are some publications out there. Look up GAG life cycle.

bt


That’s a lot of words to say “no”!

More seriously, I already knew he mechanism that causes fatigue. I already knew that fatigue was non linear with stress. But to conclude that two sharp turns is the equivalent to hundreds of small gusts over tens of hours ... it might be true but I’d want a source to say it.
 
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bikerthai
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Re: C-17 Usage

Wed Dec 23, 2020 10:57 am

Like I said google "aircraft gag cycle". There's documentation out there. You'll have to dig through a lot of text though. The next best thing is find a Loads analyst and ask. Alas I'm a design monkey and not a stress weenie.

bt
 
texl1649
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Re: C-17 Usage

Wed Dec 23, 2020 1:13 pm

Ozair wrote:
Another sustainment link which shows how well the USAF is maintaining and is able to maintain the aircraft,

C-17 Integrated Sustainment Public/Private Partnership extension

...

Boeing guarantees C-17 aircraft availability. The C-17 continues to have one of the best Mission Capable Rates and Cost per Flight Hour rates in the Air Force inventory, at 80+% (consistent since 2003) and ~$24.4K per flight hour. Specification for the C-17 is no more than 18 maintenance man-hours per flight hour, but the USAF is performing at a superior level of five maintenance man-hours per flight hour. Thus, the C-17 is available for new missions sooner and more often compared to other fleets.

...

https://www.sachamber.org/wp-content/up ... 7-GISP.pdf

While I'm not sure on the accuracy of the above claim if the USAF does have the maintenance man hours down to five per flight hour that is a great achievement and shows why the USAF love the jet so much.


It is a great plane and is hitting a mission capable rate that is tough to achieve, but it’s cost per hour/year to maintain that level per the contract in 2017 has certainly skyrocketed, PR aside. Further, for the decade that starts in October of next year, the award is now up to $23.76 billion. My cowboy math says the costs have been growing pretty rapidly.

The MOU committed their respective teams to awarding the fleet’s follow-on sustainment contract, providing coverage for the next decade. The event signified high-ranking leadership’s commitment toward streamlining acquisition processes and timelines with the aim of expeditiously awarding the follow-on contract, valued at $23.76 billion, to maintain continuous sustainment coverage for the C-17 virtual fleet once the current contract expires, Oct. 1, 2021.

The follow-on contract’s unique Performance-Based Logistic structure will provide comprehensive sustainment services to the worldwide C-17 fleet operated by the United States, United Kingdom, Australia, Canada, Kuwait, Qatar, India, United Arab Emirates and NATO.


https://www.aflcmc.af.mil/News/Article- ... -17-fleet/

The next award in 2029 would theoretically thus be somewhere in the $50 billion range if the growth rate is the same (which is not a safe assumption for a fleet with aircraft that will be hitting 35 years old).
 
Ozair
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Re: C-17 Usage

Wed Dec 23, 2020 10:29 pm

texl1649 wrote:

It is a great plane and is hitting a mission capable rate that is tough to achieve, but it’s cost per hour/year to maintain that level per the contract in 2017 has certainly skyrocketed, PR aside. Further, for the decade that starts in October of next year, the award is now up to $23.76 billion. My cowboy math says the costs have been growing pretty rapidly.

texl1649, you are confusing contracts awards with actual work completed. The 2017 US$7 billion award was an Indefinite Delivery, Indefinite Quantity award. What that means in contract terms is
Indefinite delivery, indefinite quantity contracts provide for an indefinite quantity of services for a fixed time. They are used when GSA can’t determine, above a specified minimum, the precise quantities of supplies or services that the government will require during the contract period. IDIQs help streamline the contract process and speed service delivery.

It does not mean that the contract will spend US$7 billion dollars, just that to speed up the contract process the Government assigns a not to exceed value that the contractor is happy to agree to. Same with the US$23 billion, that is an up to limit, not the actual likely spent.

If you review the USAF budget docs here for O&M https://www.saffm.hq.af.mil/Portals/84/ ... 154103-963

adding up all C-17 values for 2020 TOA required I get US$814 million for FY2020. If I compare that to some other aircraft I get

KC-135 US$1414 million for same TOA required for FY2020 - 396 aircraft
C-5 US$230 million for same TOA required for FY2020 - 52 aircraft
C-130 (excluding AC/MC/HC/LC etc) US$688 million for same TOA required for FY2020 - 334 aircraft
KC-10 US$404 million for same TOA required for FY2020 - 58 aircraft
B-52 US$429 million for same TOA required for FY2020 - 74 aircraft

The C-17 looks to be consistent with other aircraft based on fleet size and likely given usage probably under those other aircraft in overall cost for use.

texl1649 wrote:
The next award in 2029 would theoretically thus be somewhere in the $50 billion range if the growth rate is the same (which is not a safe assumption for a fleet with aircraft that will be hitting 35 years old).

That isn't a valid assumption. If we looked at the budget allocated to current aircraft as above then no other aircraft has ballooning costs in their later life as you are predicting, even though a number of them are significantly older.
 
Galaxy5007
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Re: C-17 Usage

Thu Dec 24, 2020 6:08 am

Just a note from reading this thread; The C-17 hour average is around 17K hours. Only 15-20 are actually above 20K hours. Most are in the 14K-18K range. The most hours on one jet is 26,500K and only one jet is close to that behind it. The next one is down around 23K. Most of the 05-10 models are between 8K-12K hours. The 97-02 models seem to be the most utilized with a 15K-21K range. Needless to say, the USAF fleet has been balanced out pretty well over the years, with the newer jets being utilized more than the older ones to allow them to catch up.
On another note, Other than software and a few special mods, the whole fleet is at the same standard, with the exception of the lack of ER installs on most of the pre-P-70 jets for whatever reason. There are definitely a few "troublemaker" jets out there that have their own issues, but for the most part they've held their own.

There has been rumors of future tail swaps to keep the fleet balanced, but there hasn't been any noteworthy ones since Charlotte and Pittsburgh got their jets. It has been a few years since Altus even got a swap out, with a few tails being there for over 10 years now. Unfortunately now that I'm retired, my info stream in the C-5/C-17 worlds has become minimal, but hopefully that helps out a little in the thread. The fleet is in better shape than anticipated, but as with any airframe, issues are popping up as time goes on.
 
Ozair
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Re: C-17 Usage

Thu Dec 24, 2020 11:20 am

Galaxy5007 wrote:
Just a note from reading this thread; The C-17 hour average is around 17K hours. Only 15-20 are actually above 20K hours. Most are in the 14K-18K range. The most hours on one jet is 26,500K and only one jet is close to that behind it. The next one is down around 23K. Most of the 05-10 models are between 8K-12K hours. The 97-02 models seem to be the most utilized with a 15K-21K range. Needless to say, the USAF fleet has been balanced out pretty well over the years, with the newer jets being utilized more than the older ones to allow them to catch up.
On another note, Other than software and a few special mods, the whole fleet is at the same standard, with the exception of the lack of ER installs on most of the pre-P-70 jets for whatever reason. There are definitely a few "troublemaker" jets out there that have their own issues, but for the most part they've held their own.

There has been rumors of future tail swaps to keep the fleet balanced, but there hasn't been any noteworthy ones since Charlotte and Pittsburgh got their jets. It has been a few years since Altus even got a swap out, with a few tails being there for over 10 years now. Unfortunately now that I'm retired, my info stream in the C-5/C-17 worlds has become minimal, but hopefully that helps out a little in the thread. The fleet is in better shape than anticipated, but as with any airframe, issues are popping up as time goes on.

That is some great info, really appreciate you sharing it. It is also good to see that as per expectations the USAF is managing the fleet very well. I'd be interested to know within the community what the expected service life is and whether they feel AMC's aspiration for 42k flight hours is achievable?
 
GlobalMoose
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Re: C-17 Usage

Thu Dec 24, 2020 4:44 pm

Wouldn't one think a landing on a SPRO field be somewhat less taxing on the airframe (ignore the engines here...). You're taking the jet onto a softer surface than a concrete surface spreading out the deceleration over a longer distance (as the SPRO surface will yield, the concrete one will not) reducing the G load. However, in the end, we are just splitting hairs here.
 
889091
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Re: C-17 Usage

Thu Dec 24, 2020 6:23 pm

GlobalMoose wrote:
Wouldn't one think a landing on a SPRO field be somewhat less taxing on the airframe (ignore the engines here...). You're taking the jet onto a softer surface than a concrete surface spreading out the deceleration over a longer distance (as the SPRO surface will yield, the concrete one will not) reducing the G load. However, in the end, we are just splitting hairs here.


Dust. That stuff gets everywhere. Similar to sandpaper, it eventually grinds things down.....
 
texl1649
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Re: C-17 Usage

Thu Dec 24, 2020 7:58 pm

I also appreciate Galaxy5007’s input here. Unless it’s completely off it sort of settles the matter for the time being.

The USAF if that is all accurate could easily wait at least another 5 years (possibly 10) to begin the C-17/C-5 replacement program(s), though I still think it should be part of the budgeting/program horizon if you will. Thx all.
 
GlobalMoose
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Re: C-17 Usage

Wed Dec 30, 2020 3:40 pm

I'd like to see new engines on the jet and a new APU.

Crowdsource replacement ideas for the P&W F117?
 
Reddevil556
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Re: C-17 Usage

Tue Jan 05, 2021 9:04 am

I know we are some time before the C17s start cycling out and that the AF has plenty of them, but does the DoD require manufacturers like Boeing, LM, GD, and such to keep tooling for military aircraft? I understand the logic behind dumping the tooling for planes like the 757 once production has ended, but for military aircraft it seems like the DoD would want the tooling available in the event production needs to be restarted. Theoretically speaking in 15 years as C17s start cycling out, Boeing introduces a C17B/C with upgrades like new engines, maybe a slight stretch, etc. It seems more cost effective to go that route if the basic design remains the same. Tooling could be retrieved from a DoD storage facility and production resumed with the changes. I don't think there will be a radical change in strategic airlift in the next two decades what will require a whole new design concept.
 
Ozair
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Re: C-17 Usage

Tue Jan 05, 2021 9:41 am

Reddevil556 wrote:
I know we are some time before the C17s start cycling out and that the AF has plenty of them, but does the DoD require manufacturers like Boeing, LM, GD, and such to keep tooling for military aircraft? I understand the logic behind dumping the tooling for planes like the 757 once production has ended, but for military aircraft it seems like the DoD would want the tooling available in the event production needs to be restarted. Theoretically speaking in 15 years as C17s start cycling out, Boeing introduces a C17B/C with upgrades like new engines, maybe a slight stretch, etc. It seems more cost effective to go that route if the basic design remains the same. Tooling could be retrieved from a DoD storage facility and production resumed with the changes. I don't think there will be a radical change in strategic airlift in the next two decades what will require a whole new design concept.

Retention of the unique tooling is mandated for all Major Defence Acquisition Programs but can be waived by the Def Sec if desired.

The Duncan Hunter National Defense Authorization Act for FY 2009 (P. L. 110-417, Title VIII, Subtitle B, Section 815), hereinafter Section 815, requires the Secretary of Defense to issue guidance requiring that unique tooling associated with the production of hardware for an MDAP be preserved and stored through the end of the service life of the related weapons system. Section 815 also allows the Secretary to waive this requirement in the interest of national security, with notice to the congressional defense committees.

https://www.acq.osd.mil/dpap/pdi/uid/do ... edMemo.pdf
 
Reddevil556
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Re: C-17 Usage

Tue Jan 05, 2021 10:21 am

Ozair wrote:
Reddevil556 wrote:
I know we are some time before the C17s start cycling out and that the AF has plenty of them, but does the DoD require manufacturers like Boeing, LM, GD, and such to keep tooling for military aircraft? I understand the logic behind dumping the tooling for planes like the 757 once production has ended, but for military aircraft it seems like the DoD would want the tooling available in the event production needs to be restarted. Theoretically speaking in 15 years as C17s start cycling out, Boeing introduces a C17B/C with upgrades like new engines, maybe a slight stretch, etc. It seems more cost effective to go that route if the basic design remains the same. Tooling could be retrieved from a DoD storage facility and production resumed with the changes. I don't think there will be a radical change in strategic airlift in the next two decades what will require a whole new design concept.

Retention of the unique tooling is mandated for all Major Defence Acquisition Programs but can be waived by the Def Sec if desired.

The Duncan Hunter National Defense Authorization Act for FY 2009 (P. L. 110-417, Title VIII, Subtitle B, Section 815), hereinafter Section 815, requires the Secretary of Defense to issue guidance requiring that unique tooling associated with the production of hardware for an MDAP be preserved and stored through the end of the service life of the related weapons system. Section 815 also allows the Secretary to waive this requirement in the interest of national security, with notice to the congressional defense committees.

https://www.acq.osd.mil/dpap/pdi/uid/do ... edMemo.pdf


Thanks for the response, I figured something had to be in place like that.
 
GalaxyFlyer
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Re: C-17 Usage

Tue Jan 05, 2021 7:18 pm

That’s now, but what about past programs? Tooling was lost for the C-5 and, I think the F-22 and B-2. There used to be contracts to store and maintain the tooling. When Lockheed kept pushing a third round of C-5 new production, they found their contract was terminated. Retaliation or good business?
 
texl1649
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Re: C-17 Usage

Tue Jan 05, 2021 8:14 pm

GalaxyFlyer wrote:
That’s now, but what about past programs? Tooling was lost for the C-5 and, I think the F-22 and B-2. There used to be contracts to store and maintain the tooling. When Lockheed kept pushing a third round of C-5 new production, they found their contract was terminated. Retaliation or good business?


Different eras in terms of legislation/appropriation. A given law of course can be superseded in any given appropriation bill. The B-2 was just so exorbitantly expensive as a first-of-it’s-class type it would never make sense to buy more 30 years later.

On the F-22, Obama-era congress naturally wanted to make sure they cancelled the thing for good, but further it’s the systems/computers that are now thoroughly outdated about the F-22 as concerns a new-build batch. We also don’t need thrust vectoring or a lot of the expensive to maintain surface materials it uses now. Finally, Lockheed has no motivation to compete with the USAF’s present darling the F-35 with a new F-22 derivative.

And, the coup de grace, the USAF has already built a next generation fighter they say out in the desert, so why go back to a block 1 Gen 5 design for more production?

https://nationalinterest.org/blog/buzz/ ... force-has-‘built’-and-‘flown’-potential-6th-generation-fighter-jet-169029
 
Ozair
Posts: 5582
Joined: Mon Jan 31, 2005 8:38 am

Re: C-17 Usage

Tue Jan 05, 2021 8:41 pm

GalaxyFlyer wrote:
That’s now, but what about past programs? Tooling was lost for the C-5 and, I think the F-22 and B-2. There used to be contracts to store and maintain the tooling. When Lockheed kept pushing a third round of C-5 new production, they found their contract was terminated. Retaliation or good business?

Pre the Carter directive it was all up to the individual services and acquisition programs. The USAF generally store tooling at AMARG although I don’t think they have a list of which aircraft.

it stores tooling for out-of-production aircraft

https://www.airforcemag.com/article/0213boneyard/

nor is it potentially in very good condition...
The tortured bones from tooling for the cockpit of a Northrop B-2 Spirit stealth bomber, semi-abandoned in the desert sun at AMARG. The military stores all of the tooling for closed production lines of legacy aircraft still in the inventory.

https://www.airspacemag.com/photocontes ... spirit-st/
There is an image of the condition of the B-2 cockpit tooling at the above link…

Then you have examples such as the F-22 but this is post the Ash Carter Memo.

Lockheed to preserve F-22 tooling for future use - https://www.flightglobal.com/lockheed-t ... 05.article

Realistically there are so few aircraft that have production restarted that I can see why it wasn’t a big issue but can understand with lifespans of military jets being longer, that this would be more of an issue. The flip side is that digital manufacturing/ 3D printing may make this less of an issue in the future than it has been.
 
Reddevil556
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Joined: Thu Dec 27, 2018 2:09 pm

Re: C-17 Usage

Sun Jan 10, 2021 8:14 pm

Just a random C-17 thought here...

So it seems like Boeing will be going with something similar to the 757 in regards to the NMA and those two aircraft have the same basic engines the PW2000. With the NMA possibly coming online about the same time the oldest C-17s are facing retirements, an updated C-17 could come out about the same time with the same engines as the NMA.
 
Ozair
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Joined: Mon Jan 31, 2005 8:38 am

Re: C-17 Usage

Sun Jan 10, 2021 11:35 pm

Reddevil556 wrote:
Just a random C-17 thought here...

So it seems like Boeing will be going with something similar to the 757 in regards to the NMA and those two aircraft have the same basic engines the PW2000. With the NMA possibly coming online about the same time the oldest C-17s are facing retirements, an updated C-17 could come out about the same time with the same engines as the NMA.

There have been multiple suggestions for mods to the C-17. Boeing suggested the following C-17B back in 2008 - https://www.flightglobal.com/boeing-off ... 95.article

Boeing then moved on to the C-17FE - https://www.airforcemag.com/c-17evolvesfromatobtofe/

Image

and then you have this RAND study that looks at the costs of restarting C-17 production - https://www.rand.org/pubs/technical_reports/TR1143.html which shows that the cost to restart production of a C-17 is significant and even higher for a potential derivative.

Now we are in 2021 I would expect the USAF to want to start from scratch and run a new development program for a new airlifter that would incorporate all the advances made in engine technology and digital manufacturing and well as customise it to the expected future battle and requirements. I don’t expect that program to start before 2030 (start of tender process) with aircraft deliveries starting around 2040.

A potential side option might be the USAF implementing the Digital Century Series in a similar way for transports as they are considering for fighter aircraft. That could see a paradigm shift in how transports are acquired, maintained and retired. Not sure the USAF is ready to take that leap yet with the transport fleet…
 
GalaxyFlyer
Posts: 8576
Joined: Fri Jan 01, 2016 4:44 am

Re: C-17 Usage

Tue Jan 12, 2021 1:42 am

Reddevil556 wrote:
Just a random C-17 thought here...

So it seems like Boeing will be going with something similar to the 757 in regards to the NMA and those two aircraft have the same basic engines the PW2000. With the NMA possibly coming online about the same time the oldest C-17s are facing retirements, an updated C-17 could come out about the same time with the same engines as the NMA.


The blown flaps arrangement might make re-engining expensive or problematic or both.
 
Legs
Posts: 271
Joined: Fri Jun 23, 2006 3:37 pm

Re: C-17 Usage

Tue Jan 12, 2021 11:32 am

GalaxyFlyer wrote:

The blown flaps arrangement might make re-engining expensive or problematic or both.


Any C-17 re-engine program is going to be more complicated than most; in order to keep the short field landing performance a nacelle/exhaust system that reverses the core thrust is probably going to be required.

Boeing would be going for an engine of approximately the same thrust, aiming for fuel efficiency and maintainability improvements. Unless they're going to be considering an MTOW increase, but that blows out the scope of the project. In that case, how would the flap system be affected?
 
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bikerthai
Posts: 4268
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Re: C-17 Usage

Tue Jan 12, 2021 6:15 pm

Reversing core thrust would involve a lot off titanium use. Might be easier and lighter to design a drag chute system.

bt
 
Reddevil556
Posts: 275
Joined: Thu Dec 27, 2018 2:09 pm

Re: C-17 Usage

Tue Jan 12, 2021 9:15 pm

GalaxyFlyer wrote:
Reddevil556 wrote:
Just a random C-17 thought here...

So it seems like Boeing will be going with something similar to the 757 in regards to the NMA and those two aircraft have the same basic engines the PW2000. With the NMA possibly coming online about the same time the oldest C-17s are facing retirements, an updated C-17 could come out about the same time with the same engines as the NMA.


The blown flaps arrangement might make re-engining expensive or problematic or both.


Gotcha, figured it wouldn't be all that simple.
 
Legs
Posts: 271
Joined: Fri Jun 23, 2006 3:37 pm

Re: C-17 Usage

Wed Jan 13, 2021 11:55 am

bikerthai wrote:
Reversing core thrust would involve a lot off titanium use. Might be easier and lighter to design a drag chute system.

bt


I can't see the USAF/Boeing going for something as maintenance intensive as a drag chute, especially since remote/austere field operations is a big part of the mission set.

The F117 already has a petal system to reverse core thrust as part of the reversers, but integrating that into another engine may push the cost calculation beyond whats feasible.
 
mxaxai
Posts: 2807
Joined: Sat Jun 18, 2016 7:29 am

Re: C-17 Usage

Wed Jan 13, 2021 12:11 pm

Legs wrote:
GalaxyFlyer wrote:

The blown flaps arrangement might make re-engining expensive or problematic or both.


Any C-17 re-engine program is going to be more complicated than most; in order to keep the short field landing performance a nacelle/exhaust system that reverses the core thrust is probably going to be required.

Core thrust reverse probably isn't needed on newer high-bypass engines. The higher the bypass ratio, the more thrust is generated by the bypass relative to the core.

If landing improvements are necessary, small aerodynamic changes would be easier to implement. I think takeoff is the more critical case, though, when it comes to STOL. This could be adressed by a slight thrust increase.
 
GalaxyFlyer
Posts: 8576
Joined: Fri Jan 01, 2016 4:44 am

Re: C-17 Usage

Wed Jan 13, 2021 1:53 pm

Landing distances and speeds are another design consideration. I believe they use in-flight reverse and spoilers for steep descents—one 360 from about 20,000’ to the runway. The flaps are more effective because they are “blown” by the exhaust flow. It is a unique design for transports
 
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bikerthai
Posts: 4268
Joined: Wed Apr 28, 2010 1:45 pm

Re: C-17 Usage

Thu Jan 14, 2021 11:49 am

The simplest solution for short runway is to reduce the payload. Less weight allows for lower landing speed.

bt
 
GalaxyFlyer
Posts: 8576
Joined: Fri Jan 01, 2016 4:44 am

Re: C-17 Usage

Thu Jan 14, 2021 4:02 pm

I knew that, the problem is most military loads are heavy and FOBs don’t have refueling options.

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