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mxaxai
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Re: Engine choices for the future C-17 replacement?

Fri Oct 08, 2021 9:09 am

What kind of vehicles do you want to deliver straight to the battle? The C-130 can easily carry lightly armored vehicles but once you want proper armor the C-17 is pretty much the only choice. Even the A400M and C-2 struggle with modern APCs and IFVs if they deploy with full armor (which you really want to if you're delivering them straight to the battle).

It's been pointed out multiple times that the USAF neither needs nor wants an intermediate sized aircraft. Tiltrotors will not change that. The C-17 fits USAF needs so perfectly that a reengine is highly likely, or at least a life extension. The engines offered for Boeing's NMA would be perfect, in particular RR's Ultrafan looks very promising towards the end of the decade.
 
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par13del
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Re: Engine choices for the future C-17 replacement?

Sat Oct 09, 2021 3:52 pm

How much different would we expect a C-17 replacement to look, does the C-17 bear any resemblance to the C-41 or even the C-5?
Other than engines and avionics, I assume the replacement will look like the existing a/c but have much more composite materials, now how much more can the OEM charge for such an a/c?
 
RJMAZ
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Re: Engine choices for the future C-17 replacement?

Sun Oct 10, 2021 3:47 am

mxaxai wrote:
The C-17 fits USAF needs so perfectly that a reengine is highly likely, or at least a life extension. The engines offered for Boeing's NMA would be perfect, in particular RR's Ultrafan looks very promising towards the end of the decade.

The chance of the C-17 getting new engines is zero. Engine technology has slowed dramaitcally. This is not like the KC-135 using first generation engines. Between 1960 and 1990 there was a huge improvement in fuel consumption in that 30 years. From 1990 to 2020 there was a tiny improvement by comparison.

The C-17 will definitely be getting a life extension. The oldest aircraft will be hitting the fatigue life limit around 2030 so they have to do a life extension as there is no replacement program started. Even with the life extension the fleet then would then line up with the C-5M retirement date. Due to the heavier fatigue usage of the C-17 fleet it is unlikely that the C-17 could be extended far beyond the C-5M.
 
RJMAZ
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Re: Engine choices for the future C-17 replacement?

Sun Oct 10, 2021 4:16 am

par13del wrote:
How much different would we expect a C-17 replacement to look, does the C-17 bear any resemblance to the C-41 or even the C-5?
Other than engines and avionics, I assume the replacement will look like the existing a/c but have much more composite materials, now how much more can the OEM charge for such an a/c?

There is no correct answer in terms of size. Carrying six medium weight vehicles into theatre on a very large transport does have cost savings over flying two smaller transports with 3 vehicles each. I think the modern USAF would take the smaller transport option as it gives more flexibility and they know that carrying tanks is a very rare situation.

The C-17 and C-5M was sized to carry two rows of Humvees and light trucks. But with the popular medium weight vehicles it results in wasted space. Two rows of medium weight vehicles would result in an aircraft too large. That is why I think the C-17 and C-5M will be replaced with a very efficient twin engine airlift with passenger airline running costs. Basically a slightly skinnier twin engine C-17 sized aircraft with 50% more range for the Pacific region.
 
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kitplane01
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Re: Engine choices for the future C-17 replacement?

Sun Oct 10, 2021 5:17 am

RJMAZ wrote:
mxaxai wrote:
The C-17 fits USAF needs so perfectly that a reengine is highly likely, or at least a life extension. The engines offered for Boeing's NMA would be perfect, in particular RR's Ultrafan looks very promising towards the end of the decade.

The chance of the C-17 getting new engines is zero. Engine technology has slowed dramaitcally. This is not like the KC-135 using first generation engines. Between 1960 and 1990 there was a huge improvement in fuel consumption in that 30 years. From 1990 to 2020 there was a tiny improvement by comparison.


Is that true?

The GTF is something like a 15% improvement in fuel consumption. The GEnX is supposed to be 15% better in fuel consumption than it's predecessor. I sort of thought we were seeing 15% better every 15-20 years or so. Comparing a 1990 CF-6 to a 2021 Trent 1000 should get you a 20% improvement or so give or take. That's not tiny. And a 20% improvement in C-17 range would be nice as we pivot to the Pacific, allowing greater payloads at the longer distances.

I agree it's less than the improvements before. viewtopic.php?f=5&t=1465457
 
RJMAZ
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Re: Engine choices for the future C-17 replacement?

Sun Oct 10, 2021 7:01 am

kitplane01 wrote:
Is that true?

The GTF is something like a 15% improvement in fuel consumption. The GEnX is supposed to be 15% better in fuel consumption than it's predecessor.

Yes.

The TF33-P-3 engine for used on the B-52 burns 0.82lb of fuel for every pound if thrust. The Trent 700 on the A330 burns only 0.562 lb. That is a 0.258lb saving.

Going from the original GE90 (0.545 lb) to current Trent XWB (0.478 lb) has also been around 20 years and it only saves 0.067lb per hour. The improvement is around a third.

From 2020 to 2040 I expect it to continue to slow with maybe a 0.030lb improvement at the best case scenario. While percentage wise there is a fuel burn improvement this does not translate to the real world. Performance gained from new engines is becoming less and less. Take a large transport aircraft using 1960's engines and switch to 1990's engines and it might save 30t in trip fuel burn that can go towards extra cargo. Going from 1990's to 2020 engine tech might save only 10t of trip fuel so there is a smaller gain in cargo.

https://en.m.wikipedia.org/wiki/General_Electric_GE90
https://en.m.wikipedia.org/wiki/Rolls-Royce_Trent
https://en.m.wikipedia.org/wiki/Pratt_%26_Whitney_JT3D


Back to the C-17.
The gains of new engines is becoming smaller, the costs of fitting new engines is increasing. There is no economic reason to upgrade the engines on the C-17. Another big factor in terms of fitting new engines is how much service life the aircraft has remaining.

The C-5B has an original service life of 60,000 hours and still they all had more than 20,000 hours flight hours remaining before getting new engines fitted. This gives plenty of time for the lower maintenance and fuel burn to pay for the costs of fitting new engines. The process was cost effective as it wasn't a full rebuild. Avionics and engines. The C-5B also gains more performance because the original engines are older.

The C-17 on the other hand has a original design service life of only 30,000 hours. In 2030 the 50 oldest aircraft will definitely have less than 5,000 flight hours remaining. If they try to average out the hours by flying the newer jets more then the entire fleet would have under 10,000 hours. The C-17 would need an extremely expensive rebuild to add another 20,000 flight hours to make it worth fitting new engines. The fleet will most likely get a light refurb, inspection to squeeze an additional 10,000 flight hours get the fleet to around 2045 that matches the C-5M retirement. Probably with flight restrictions.
 
GalaxyFlyer
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Re: Engine choices for the future C-17 replacement?

Sun Oct 10, 2021 1:40 pm

I doubt there were any C-5B models with 40,000 hours on them. They were close to the A models in the Reserves at about 22,000 hours when I left in 2005. Maybe 30,000, and be on the high side.

The HUMVEE wasn’t a thing in 1966 when the C-5 was designed but the standard 102” tractor-trailer was. Two fit very close together. The design goal was two rows of 463L pallets which happened to work for lots of other cargo. A Mark V boat fills it up height-wise; a couple of classified loads go right over the catwalks. A tank looks like there’s nothing on board. Munitions are the same, doesn’t look like much, until you taxi out.
 
texl1649
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Re: Engine choices for the future C-17 replacement?

Sun Oct 10, 2021 7:57 pm

RJMAZ wrote:
kitplane01 wrote:
Is that true?

The GTF is something like a 15% improvement in fuel consumption. The GEnX is supposed to be 15% better in fuel consumption than it's predecessor.

Yes.

The TF33-P-3 engine for used on the B-52 burns 0.82lb of fuel for every pound if thrust. The Trent 700 on the A330 burns only 0.562 lb. That is a 0.258lb saving.

Going from the original GE90 (0.545 lb) to current Trent XWB (0.478 lb) has also been around 20 years and it only saves 0.067lb per hour. The improvement is around a third.

From 2020 to 2040 I expect it to continue to slow with maybe a 0.030lb improvement at the best case scenario. While percentage wise there is a fuel burn improvement this does not translate to the real world. Performance gained from new engines is becoming less and less. Take a large transport aircraft using 1960's engines and switch to 1990's engines and it might save 30t in trip fuel burn that can go towards extra cargo. Going from 1990's to 2020 engine tech might save only 10t of trip fuel so there is a smaller gain in cargo.

https://en.m.wikipedia.org/wiki/General_Electric_GE90
https://en.m.wikipedia.org/wiki/Rolls-Royce_Trent
https://en.m.wikipedia.org/wiki/Pratt_%26_Whitney_JT3D


Back to the C-17.
The gains of new engines is becoming smaller, the costs of fitting new engines is increasing. There is no economic reason to upgrade the engines on the C-17. Another big factor in terms of fitting new engines is how much service life the aircraft has remaining.

The C-5B has an original service life of 60,000 hours and still they all had more than 20,000 hours flight hours remaining before getting new engines fitted. This gives plenty of time for the lower maintenance and fuel burn to pay for the costs of fitting new engines. The process was cost effective as it wasn't a full rebuild. Avionics and engines. The C-5B also gains more performance because the original engines are older.

The C-17 on the other hand has a original design service life of only 30,000 hours. In 2030 the 50 oldest aircraft will definitely have less than 5,000 flight hours remaining. If they try to average out the hours by flying the newer jets more then the entire fleet would have under 10,000 hours. The C-17 would need an extremely expensive rebuild to add another 20,000 flight hours to make it worth fitting new engines. The fleet will most likely get a light refurb, inspection to squeeze an additional 10,000 flight hours get the fleet to around 2045 that matches the C-5M retirement. Probably with flight restrictions.


I believe the USAF expects the service life to be extended past 45K hours on the C-17. I agree it makes no sense to re-engine an aircraft with less than (about) 20K hours left.

https://www.globalsecurity.org/military ... 7-life.htm
 
RJMAZ
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Re: Engine choices for the future C-17 replacement?

Mon Oct 11, 2021 8:25 am

I'm very interested in the fuselage size and cross section of the C-17 and C-5M replacement. Vehicles like the Oshkosh L-ATV at 2.5m wide and the Stryker at 2.7m wide make it near impossible to fit two vehicles in the width. It might be worth just letting go of the oversize role and go long and skinny.

I actually think the C-17 is an inefficient cross section. It is like the A310 in the passenger world. Yes it can two 463L pallets if they are put sideways but it is too short and stubby. I think it would have been much better if it had the fuselage cross section say 25% skinnier but 25% longer. Cargo bay length might have been 33% longer due to the reduced nose and tail tapers. This would give a negligible decrease in pallets but a significant increase in vehicles. 6 L-ATV vehicles instead of 4. It would also have plenty of room for all the side seats to be used.

I like the idea of a stretched Kawasaki C-2 with some 787 engines. It is a bit like going from the 747-400 to the 747-8. Boeing stretched the fuselage, increased the MTOW, fitted winglets and put on the latest engines. Fuel efficiency of the 747-8 increased by approximately 15% and it could carry 10% more payload 5% further.

The USAF would need to purchase around 500 aircraft to replace the C-17 and C-5M fleets but it would be superior in my opinion to a new large C-5 sized aircraft. I could see a huge number of C-130J operators buying it as it would have low operating costs and it would be the first strategic airlifter for most countries.
 
mxaxai
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Re: Engine choices for the future C-17 replacement?

Mon Oct 11, 2021 9:09 am

Armored vehicles like the Stryker are so heavy that the C-17 can only carry three to four of them anyway. Only two in the case of some heavier APCs. The cargo hold length is sufficient to load them behind each other.

Only light vehicles can be carried in greater numbers by the C-17.
 
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LyleLanley
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Re: Engine choices for the future C-17 replacement?

Mon Oct 11, 2021 7:18 pm

kitplane01 wrote:
LyleLanley wrote:
De-rated Gen-X


The lowest rated GenX has 70k thrust. You need 40k thrust. That’s not a derate it’s a new engine.


Who says a future C-17 replacement needs exactly the same thrust as the current C-17? Derate to low 60s for life expectancy and you've got a decent engine for this mythical jet. 4 engines = no need to worry about ETOPS and more options.
 
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bikerthai
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Re: Engine choices for the future C-17 replacement?

Mon Oct 11, 2021 9:43 pm

LyleLanley wrote:
4 engines = no need to worry about ETOPS and more options.


ETOPS is a civilian requirement. Not sure if it was ever flowed to the Military side. My sense is that all the extra thrust from the additional engines are for short field performance.

bt
 
GalaxyFlyer
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Re: Engine choices for the future C-17 replacement?

Mon Oct 11, 2021 9:50 pm

bikerthai wrote:
LyleLanley wrote:
4 engines = no need to worry about ETOPS and more options.


ETOPS is a civilian requirement. Not sure if it was ever flowed to the Military side. My sense is that all the extra thrust from the additional engines are for short field performance.

bt


True, but the military does have to abide for safety reasons to diverting once a twin has lost an engine. A quad leaves more options to continue. You can still be under-powered with four engines—C-5 for one instance.
 
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LyleLanley
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Re: Engine choices for the future C-17 replacement?

Tue Oct 12, 2021 12:08 am

bikerthai wrote:
LyleLanley wrote:
4 engines = no need to worry about ETOPS and more options.


ETOPS is a civilian requirement. Not sure if it was ever flowed to the Military side. My sense is that all the extra thrust from the additional engines are for short field performance.

bt


What Galaxy said. But otr, the KC-46 is certified for ETOPS-180 and normally abides by ETOPS rules. When it can't, they'll generally go for a waiver, but it's still a day-to-day requirement.

1 engine on a 2 engine jet= land as soon as possible
2 engines on a 3 engine jet = land as soon as practical
3 engines on a 4 engine jet = land at the nearest divert with the highest per diem
2 engines on a 4 engine turboprop = max endurance in a P-3
 
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bikerthai
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Re: Engine choices for the future C-17 replacement?

Tue Oct 12, 2021 12:24 am

Curious then with the KC-10. Does the diversion scenario differs if the center engine fails as opposed to one of the wing engine?

With the loss of the center you don't have to fight the stabilizer but you have to deal with the pitch imbalance.

bt
 
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kitplane01
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Re: Engine choices for the future C-17 replacement?

Tue Oct 12, 2021 1:14 am

LyleLanley wrote:
kitplane01 wrote:
LyleLanley wrote:
De-rated Gen-X


The lowest rated GenX has 70k thrust. You need 40k thrust. That’s not a derate it’s a new engine.


Who says a future C-17 replacement needs exactly the same thrust as the current C-17? Derate to low 60s for life expectancy and you've got a decent engine for this mythical jet. 4 engines = no need to worry about ETOPS and more options.


If you put 4x60K engines on a C-17, you've got way more thrust than you need. You've also got way more drag and weight and maintenance and cost than you want. It's not even close .. it's 50% too much.
 
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kitplane01
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Re: Engine choices for the future C-17 replacement?

Tue Oct 12, 2021 1:16 am

RJMAZ wrote:

The USAF would need to purchase around 500 aircraft to replace the C-17 and C-5M fleets but it would be superior in my opinion to a new large C-5 sized aircraft. I could see a huge number of C-130J operators buying it as it would have low operating costs and it would be the first strategic airlifter for most countries.


There are 222 C-17s and 52 C-5s in the inventory. I don't see how the USAF is going to afford 500 aircraft of a similar size. Or have I missed something?
And if it's smaller (or a tiltrotor) how does it move an Abrams tank?
 
GalaxyFlyer
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Re: Engine choices for the future C-17 replacement?

Tue Oct 12, 2021 1:42 am

LyleLanley wrote:
bikerthai wrote:
LyleLanley wrote:
4 engines = no need to worry about ETOPS and more options.


ETOPS is a civilian requirement. Not sure if it was ever flowed to the Military side. My sense is that all the extra thrust from the additional engines are for short field performance.

bt


What Galaxy said. But otr, the KC-46 is certified for ETOPS-180 and normally abides by ETOPS rules. When it can't, they'll generally go for a waiver, but it's still a day-to-day requirement.

1 engine on a 2 engine jet= land as soon as possible
2 engines on a 3 engine jet = land as soon as practical
3 engines on a 4 engine jet = land at the nearest divert with the highest per diem
2 engines on a 4 engine turboprop = max endurance in a P-3


Or, when leaving an airbase in Saudi, upon engine loss on climb-out, divert to Ramstein for dinner at the old FireHouse pub.
 
RJMAZ
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Re: Engine choices for the future C-17 replacement?

Tue Oct 12, 2021 1:43 am

kitplane01 wrote:
There are 222 C-17s and 52 C-5s in the inventory. I don't see how the USAF is going to afford 500 aircraft of a similar size. Or have I missed something?
And if it's smaller (or a tiltrotor) how does it move an Abrams tank?

It would be smaller with low running costs and high economy of scale providing a very low unit cost. I estimate the best size is roughly two thirds the size of the C-17. One third of the size of the C-5M.

The stupid requirement to move an Abram tanks by air will of course be dropped as they always get sent by sea. Nearly all of the high end infantry fighting vehicles are under 40t. The Bradley is just under 30t. For a Pacific theatre it needs a solid 4,000nm range with one 30t- 40t vehicle. This cover most bases to Hawaii. Then from Hawaii to Japan or Guam. Then from Guam and Japan it can fly to Taiwan and back without having to refuel in Taiwan.

The Kawasaki C-2 can do 30t to 3,100nm. In 10 years time with a MTOW increase and GenX engines it can do the mission. The Quad tiltrotor lifting 30t+ would have a range below 500nm. So it does the lift to the battlefield.
 
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kitplane01
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Re: Engine choices for the future C-17 replacement?

Tue Oct 12, 2021 1:48 am

RJMAZ wrote:
kitplane01 wrote:
There are 222 C-17s and 52 C-5s in the inventory. I don't see how the USAF is going to afford 500 aircraft of a similar size. Or have I missed something?
And if it's smaller (or a tiltrotor) how does it move an Abrams tank?

It would be smaller with low running costs and high economy of scale providing a very low unit cost. I estimate the best size is roughly two thirds the size of the C-17. One third of the size of the C-5M.

The stupid requirement to move an Abram tanks by air will of course be dropped as they always get sent by sea. Nearly all of the high end infantry fighting vehicles are under 40t. The Bradley is just under 30t. For a Pacific theatre it needs a solid 4,000nm range with one 30t- 40t vehicle. This cover most bases to Hawaii. Then from Hawaii to Japan or Guam. Then from Guam and Japan it can fly to Taiwan and back without having to refuel in Taiwan.

The Kawasaki C-2 can do 30t to 3,100nm. In 10 years time with a MTOW increase and GenX engines it can do the mission. The Quad tiltrotor lifting 30t+ would have a range below 500nm. So it does the lift to the battlefield.


Question: Using more, smaller aircraft adds flexibility, but doesn't it also add cost? Assuming you can fill both aircraft, doesn't a larger aircraft move freight at a lower cost per ton-mile?
 
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LyleLanley
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Re: Engine choices for the future C-17 replacement?

Tue Oct 12, 2021 1:56 am

bikerthai wrote:
Curious then with the KC-10. Does the diversion scenario differs if the center engine fails as opposed to one of the wing engine?

With the loss of the center you don't have to fight the stabilizer but you have to deal with the pitch imbalance.

bt


Nope, not at all. In fact, a two engine go-around is easier if it's a #2 fail than a wing engine, as the thrust is still symmetric. There will probably be some discussion from the Bobs about having to do a #2 engine change vs. a wine engine, but that's not for the crew to decide.

At the end of the day, you trim for the failed engine, whether it's rudder trim for a wing engine, or pitch trim for the center. Either way, pretty benign. Now, if there are hydraulic failures as a result of a catastrophic engine loss, that's an entirely different matter.

kitplane01 wrote:
If you put 4x60K engines on a C-17, you've got way more thrust than you need. You've also got way more drag and weight and maintenance and cost than you want. It's not even close .. it's 50% too much.


Why do you keep saying they'll be put on a C-17? You wrote "C-17 replacement", not "C-17 reengine". And drag and weight? If you're talking about the C-17, probably the draggiest jet in the MAF, you need a better argument: GenX engines cannot possibly make the C-17's fuel burn worse. Besides, using assumed temp for takeoffs and then letting the horses loose for the climbs to altitude would be the smart way to do things. Tactical and tacticool.

GF's diversion criteria is a better method to go by than rational, but incorrect, thoughts about drag, mx costs, etc. You don't want to shoehorn a military airlifter into performance issues: options are good. I've never been to the Firehouse, but the KMCC has solid options. Certainly better than anywhere in AFRICOM or CENTCOM (talking bases, not off-base).
Last edited by LyleLanley on Tue Oct 12, 2021 2:01 am, edited 1 time in total.
 
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kitplane01
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Re: Engine choices for the future C-17 replacement?

Tue Oct 12, 2021 2:01 am

LyleLanley wrote:
bikerthai wrote:
Curious then with the KC-10. Does the diversion scenario differs if the center engine fails as opposed to one of the wing engine?

With the loss of the center you don't have to fight the stabilizer but you have to deal with the pitch imbalance.

bt


Nope, not at all. In fact, a two engine go-around is easier if it's a #2 fail than a wing engine, as the thrust is still symmetric.

At the end of the day, you trim for the failed engine, whether it's rudder trim for a wing engine, or pitch trim for the center. Either way, pretty benign. Now, if there are hydraulic failures as a result of a catastrophic engine loss, that's an entirely different matter.

kitplane01 wrote:
If you put 4x60K engines on a C-17, you've got way more thrust than you need. You've also got way more drag and weight and maintenance and cost than you want. It's not even close .. it's 50% too much.


Why do you keep saying they'll be put on a C-17? You wrote "C-17 replacement", not "C-17 reengine". And drag and weight? If you're talking about the C-17, probably the draggiest jet in the MAF, you need a better argument: GenX engines cannot possibly make the C-17's fuel burn worse. Besides, using assumed temp for takeoffs and then letting the horses loose for the climbs to altitude would be the smart way to do things. Tactical and tacticool.


I'm sorry if I was unclear (but I don't think I was).

If you put 4 GeNXs on any plane similar in size to a C-17, you will have way more thrust, drag, cost, and weight than needed. Like 50% more.
 
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LyleLanley
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Re: Engine choices for the future C-17 replacement?

Tue Oct 12, 2021 2:05 am

kitplane01 wrote:
I'm sorry if I was unclear (but I don't think I was).

If you put 4 GeNXs on any plane similar in size to a C-17, you will have way more thrust, drag, cost, and weight than needed. Like 50% more.


You're good. Your opening post seemed more about a C-17 replacement, which doesn't necessarily mean an airlifter that is in the exact same dimensions, thrust class, etc. as the C-17. Two engines are probably a bad idea (C-2 aside, but it's also not meant for forward-deployed ops), three engines can be problematic depending on the fuselage, but 4 engines is easiest fuselage-flexibility wise.

Derated GenX, using assumed temp, but having power available at the drop of a button, would be a tactical beast. And it's better to have too much thrust than not enough.
 
GalaxyFlyer
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Re: Engine choices for the future C-17 replacement?

Tue Oct 12, 2021 2:15 am

You missed the Alte Feuerwoche, sadly gone. Hil was a butcher and restaurant chef/owner. After the meals were prepared, he’d come out with an accordion and sing old German and American songs. Food was fabulous, the beer, too. Many a crew sleeping off dinner after too many beers. It was on von Richthofen Strasse, down from the Kristine. It was pretty normal to see sergeants and generals having dinner, TDY or PCS bringing their family in. Hil would joke, if the terrorists wanted to kill Americans, they’d bomb his restaurant.

KMCC?
 
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LyleLanley
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Re: Engine choices for the future C-17 replacement?

Tue Oct 12, 2021 2:26 am

Like the Galaxy club of yore, I was born too late. That sounds like the place to go!

KMCC is the Kaiserslautern military community center. Imagine billeting, restaurants, the BX and food court all rolled into one. You can also rent a car there and explore Europe on the government's dime (travel voucher!). Sorta like staying at the Outrigger Waikiki. Lots of options and, if you have to stay on base, it's the place to be.
 
GalaxyFlyer
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Re: Engine choices for the future C-17 replacement?

Tue Oct 12, 2021 2:36 am

I only stayed in Kaiserslautern once, IIRC. Usually somewhere in Ramstein Village or Landstuhl. I did rent cars on “broke” planes—Mosel, Luxembourg, Heidelberg, Bern Kassel. C-5 was good for impromptu vacations. Once had a Sys A pressure line develop a pinhole leak, fogged the cargo box badly. Got back on the ground at Ramstein, MX within an hour says they have to go back to the vendor in California for the part—5 day ETIC, parts plus 1 hour.
 
JayinKitsap
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Re: Engine choices for the future C-17 replacement?

Tue Oct 12, 2021 3:51 am

GalaxyFlyer wrote:
I only stayed in Kaiserslautern once, IIRC. Usually somewhere in Ramstein Village or Landstuhl. I did rent cars on “broke” planes—Mosel, Luxembourg, Heidelberg, Bern Kassel. C-5 was good for impromptu vacations. Once had a Sys A pressure line develop a pinhole leak, fogged the cargo box badly. Got back on the ground at Ramstein, MX within an hour says they have to go back to the vendor in California for the part—5 day ETIC, parts plus 1 hour.


Truly dreadful, how did you handle it :roll:
 
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bikerthai
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Re: Engine choices for the future C-17 replacement?

Tue Oct 12, 2021 5:29 am

kitplane01 wrote:
you will have way more thrust, drag, cost, and weight than needed. Like 50% more.


Well, what would be the consequence of having more thrust with an engine out condition?

For a twin, if you have more thrust, you would have more yaw with an engine out. Thus you need a larger fin/rudder to compensate, at least until you can reduce the thrust of the remaining engine.

With a 4 holder the drop off may not be as much, but the vertical stab is sized for such condition. So adding more thrust may result indirectly needing a larger stab.

bt
 
RJMAZ
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Re: Engine choices for the future C-17 replacement?

Tue Oct 12, 2021 6:24 am

kitplane01 wrote:
Question: Using more, smaller aircraft adds flexibility, but doesn't it also add cost? Assuming you can fill both aircraft, doesn't a larger aircraft move freight at a lower cost per ton-mile?

Yes and no. If all designs are a cleansheet then the larger aircraft is probably cheaper per ton-mile.

But as a design is scaled up the number of airports that it can operate from reduces. Let's set a fixed runway requirement of 2,000m and slightly wet. The larger the aircraft gets the more complex the design needs to be in terms of flaps to reduce landing speed, landing gear to reduce pavement loading and engines to reduce takeoff distance. A civilian A320 could operate from that runway all day long but a large C-17 needs a massive amount of technology to operate from that runway and this puts up the cost per ton-mile. The high lift C-17 wing also reduces the cruising speed below civilian air traffic.

The Kawasaki C-2 is a very simple design. No fancy landing gear, engines or high lift devices. But it can operate from smaller airports due to it being not too big, not too small, just right. So the C-2 size is probably at the point where the cost per ton-mile is the lowest. As you go bigger the design has to get more complex.
 
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N14AZ
Posts: 4249
Joined: Sat Feb 24, 2007 10:19 pm

Re: Engine choices for the future C-17 replacement?

Wed Oct 13, 2021 7:59 am

This might be a little bit too off topic but since we have not yet found the perfect replacement for the C 17 engines it might be acceptable.. just for recreation until the discussion continues… :-)
GalaxyFlyer wrote:
You missed the Alte Feuerwoche, sadly gone. Hil was a butcher and restaurant chef/owner. After the meals were prepared, he’d come out with an accordion and sing old German and American songs. Food was fabulous, the beer, too. Many a crew sleeping off dinner after too many beers. It was on von Richthofen Strasse, down from the Kristine. It was pretty normal to see sergeants and generals having dinner, TDY or PCS bringing their family in. Hil would joke, if the terrorists wanted to kill Americans, they’d bomb his restaurant.

KMCC?

This made me curious. It seems as if the restaurant as such is still existing. But it’s now a pizza parlor (parlour for our British members)… :-(

Tried to find some old pictures but didn’t succeed.
 
GalaxyFlyer
Posts: 8576
Joined: Fri Jan 01, 2016 4:44 am

Re: Engine choices for the future C-17 replacement?

Wed Oct 13, 2021 2:47 pm

N14AZ wrote:
This might be a little bit too off topic but since we have not yet found the perfect replacement for the C 17 engines it might be acceptable.. just for recreation until the discussion continues… :-)
GalaxyFlyer wrote:
You missed the Alte Feuerwoche, sadly gone. Hil was a butcher and restaurant chef/owner. After the meals were prepared, he’d come out with an accordion and sing old German and American songs. Food was fabulous, the beer, too. Many a crew sleeping off dinner after too many beers. It was on von Richthofen Strasse, down from the Kristine. It was pretty normal to see sergeants and generals having dinner, TDY or PCS bringing their family in. Hil would joke, if the terrorists wanted to kill Americans, they’d bomb his restaurant.

KMCC?

This made me curious. It seems as if the restaurant as such is still existing. But it’s now a pizza parlor (parlour for our British members)… :-(

Tried to find some old pictures but didn’t succeed.


That’s the building, alright.

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