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Trimeresurus
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How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Sat Oct 17, 2020 1:36 pm

How are propellers that effective at such thin air of FL300+? What stops something like the Caravan or the King Air(other than pressurization for the people on board) reaching that heights and speeds?

And why do the militaries prefer props over jets, considering how popular C-130 is and the size of the A400M(way bigger than many jetliners). Are they less maintenance intensive in the war time than jets? That sounds counterintuitive since jet engines have less moving parts.
 
GalaxyFlyer
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Sat Oct 17, 2020 3:09 pm

Add power thru advanced engines, better propeller design and no problem getting turboprops up into the low 30s. King Airs do it, too. Caravans weren’t designed to go that high, all choices by the marketing and design folks.

Props are better on short or unprepared surfaces, instant power. A C-130 can start another C-130 by parking in front of it and using prop “wash” to windmill the other Herk.
 
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SheikhDjibouti
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Sat Oct 17, 2020 6:26 pm

Trimeresurus wrote:
How are propellers that effective at such thin air of FL300+? What stops something like the Caravan or the King Air(other than pressurization for the people on board) reaching that heights and speeds.


Height - no problem. Speed is another matter.

The highest recorded interception during WWII was a modified Spitfire HF IX (BF273, standard supercharged Merlin 61 engine + larger wooden (?) propeller) finally catching up with a German Junkers JU-86R (the high altitude version re-engined with double supercharged Jumo 207 DIESEL engines with a side helping of Nitrous Oxide) :o

If you think that's strange, I haven't even started yet; it's gets even weirder...

The pilot was Flt Lt Prince Emanuel Galitzine, a Russian expat flying out of Northolt, famous for several Polish squadrons.
However, he doesn't even get a mention on the "House of Golitsyn" wiki page (except for sharing his grave with Prince George Galitzine)
https://en.wikipedia.org/wiki/House_of_Golitsyn

Nevertheless I have found a photo of him landing in a Spitfire LF IX in Southern France (probably autumn 1944),

ImageThx wiki

Bear with me....
These special Mk IXs were stripped of everything not required for the role of high-level interception, lightening them by 450 lb each.
Various reports talk about removing armor, .303 guns, special lightweight paint (?), and also pairs of a/c, only one of which carried a (heavy) radio, the other climbing higher to perform the actual intercept.

Back to the day in question;
When he eventually caught the JU-86 at around 41,000 feet, he fired 25 rounds (x2) with both cannon until one cannon seized. The remaining (starboard) gun then fired intermittently, possibly one round at a time.
This may have been fortunate, because in the rarified atmosphere the recoil from the (single) operational cannon caused his aircraft to become barely controllable.

The combat itself lasted some 40 minutes (an incredible time for WWII), starting over southern England, and ending uncomfortably close to Cherbourg, with Galitzine probably wondering if he had enough fuel to make it back (to Tangmere; Northolt was totally out of the question)

Luck was absolutely on the side of the bad guys that day, as one of the few rounds that Galitzine fired got embedded in the JU-86's wing, but failed to explode.
https://en.wikipedia.org/wiki/Supermari ... de_bombers
More here, if you can read Russian (convoluted link due to cyrillic script, but it's still wikipedia :bigthumbsup: )
https://ru.wikipedia.org/wiki/%D0%93%D0 ... 0%B8%D1%87

And bless my soul...here is the original combat report from 1942.
Simply amazing!
https://ww2aircraft.net/forum/attachmen ... pg.132125/

And a photo of the Spitfire involved, BS273
Image
thx allspitfirepilots.org

The image is labelled BS273, whilst clearly showing BF273
The usual explanation is that this Spitfire was incorrectly marked as BF273, which should belong to a Bristol Blenheim bomber.

However... my own research reveals that whilst BF273 was allocated to one of 1195 Bristol Blenheim aircraft ordered from A.V. Roe & Co. Ltd, Chadderton, Lancs., to contract B.119994/40, the final 575 airframes were subsequently cancelled, including all those allocated BFxxx.

So yes, we come back to BS273 which along with BS274 (and a third a/c BS271), were high altitude "specials", and all three were erroneously painted BFxxx.

Unfortunately BS273 was lost 4th July 1943 near Cayeux. Flt Sgt C Woodall RIP

BS274 was post war converted to a two seat trainer for the R Neth AF (as "H-98")
Except this isn't it; this is G-CCCA / PV202, painted to represent H-98. :cry2:
Nothing to see here; move along please.
 
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Horstroad
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Sat Oct 17, 2020 6:37 pm

GalaxyFlyer wrote:
A C-130 can start another C-130 by parking in front of it and using prop “wash” to windmill the other Herk.

Wouldn't that be possible with jet engines as well? I assume this is a procedure only trained in the military... but I could imagine this might work with commercial jet powered aircraft as well.
 
GalaxyFlyer
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Sat Oct 17, 2020 7:15 pm

No, it wouldn’t because a propellor very different than a fan stage.
 
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fr8mech
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Sat Oct 17, 2020 8:17 pm

Horstroad wrote:
Wouldn't that be possible with jet engines as well? I assume this is a procedure only trained in the military... but I could imagine this might work with commercial jet powered aircraft as well.


It might be possible on a low bypass engine, but not probable. In a typical jet engine, the fan is not directly connected to the core engine. You can spin the fan all you want, the core will not turn. In fact, there was a procedure on the old JT9D-7XX where you could tie the fan down and run the engine for leak checks. I never saw it done, but it was in our manual, for a while.
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Trimeresurus
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Sat Oct 17, 2020 9:22 pm

SheikhDjibouti wrote:
Height - no problem. Speed is another matter.


But higher an airplane gets, lower the density of the air it'll be in that flight level, so higher the stall speed(TAS) will be. Isn't this the main limitation regarding service ceiling of aircraft? Their cruise speed won't be even enough to generate lift at that altitude so they can't climb further.
 
GalaxyFlyer
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Sat Oct 17, 2020 10:35 pm

And when that happens, they stop climbing. When power required to maintain an IAS equal to stall speed clean, equals the power available, the plane is at its absolute ceiling. Weight is a factor here. Service ceiling is when there is either 100fpm climb or 300 fpm climb capability, it’s at its service ceiling or cruise ceiling. Definitions sometimes vary.
 
Okcflyer
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Sat Oct 17, 2020 11:44 pm

fr8mech wrote:
Horstroad wrote:
Wouldn't that be possible with jet engines as well? I assume this is a procedure only trained in the military... but I could imagine this might work with commercial jet powered aircraft as well.


It might be possible on a low bypass engine, but not probable. In a typical jet engine, the fan is not directly connected to the core engine. You can spin the fan all you want, the core will not turn. In fact, there was a procedure on the old JT9D-7XX where you could tie the fan down and run the engine for leak checks. I never saw it done, but it was in our manual, for a while.


Ground windmilling may be possible on the Allison’s that power the C130 as it uses a single shaft design. Most turbo props are powered by PT6 engines which use a power turbine / two shaft layout. It’s Impossible to windmill start those.
 
RJMAZ
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Sun Oct 18, 2020 5:43 am

I will explain the science behind it.

Thrust is calculated by the combination of both the quantity of the air and the speed of the air.

A Turboprop can push a larger volume of air but at a slower speed.

A Turbojet can push less air but at a much faster speed.

A Turbofan is half way inbetween. All engines types could produce the same thrust level just at different air flow and velocity levels.

Rule one: An aircraft can not fly faster than the air coming out of the engine. That is the main reason why a Turboprop can not fly supersonic. An afterburner in a jet engine gains the extra thrust by speeding up the existing air leaving the exhaust. No extra air is coming out it is just coming out faster. This extra exhaust velocity is why fighter aircraft can easily go supersonic using afterburner.

Rule two: To produce the same thrust level it requires less energy to move a large volume of air slowly than a a small volume of air at slow speed. Take the same aircraft design and the only change was a Turboprop, Turbofan and Turbojet. While flying at the say 600km/h the turboprop will burn much less fuel. This is also why helicopters have such a large main rotor. It will burn less fuel

Rule three: Acceleration from a stand still will be faster if you have an engine that produces a large volume of air at low speed. With an engine of the same weight a turboprop will then accelerate much faster takeoff which is why it is preferable for tactical transport aircraft.

So to answer your question. Newer turboprop designs like the A400m can fly high and fast because they have a higher exhaust velocity. This is done by using a prop with more blades and spinning it faster using a more powerful engine. The C-130J Super Hercules gained 100+km/h extra speed over the C-130H Hercules by going from a 4 blade prop to a 6 blade prop and fitting engines with 30% more power. Extra power was needed to make full use of the 6 bladed prop when pushing through the thick air at sea level.

The latest C-2 Hawkeye has 8 blade props but these only provide an advantage at high altitude cruise the engines would need more thrust to fully take advantage of the prop at the thicker air density during takeoff. That is why the C-130J has not had the 8 blade prop fitted. I do expect an 8 blade prop and more powerful engines to be fitted to the C-130 to reduce takeoff run by 20%, improve range by 20% and increase speed by 10%. It will be the first aircraft to remain in production for 100 years.
 
426Shadow
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Sun Oct 18, 2020 7:06 am

RJMAZ wrote:
I do expect an 8 blade prop and more powerful engines to be fitted to the C-130 to reduce takeoff run by 20%, improve range by 20% and increase speed by 10%. It will be the first aircraft to remain in production for 100 years.



There is no plan to fit the 8 blade props on the J model. There was for the older models though and it was thoroughly tested. We also tested winglet's on the J model but that kind of died out.

Source: I work at LM Marietta.
We are all just fanboys, our opinions don't make or break businesses.
 
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Horstroad
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Sun Oct 18, 2020 10:30 am

fr8mech wrote:
It might be possible on a low bypass engine, but not probable. In a typical jet engine, the fan is not directly connected to the core engine. You can spin the fan all you want, the core will not turn. In fact, there was a procedure on the old JT9D-7XX where you could tie the fan down and run the engine for leak checks. I never saw it done, but it was in our manual, for a while.

I thought it might be possible as starting an engine in flight with windmilling is possible as well. I don't know what airspeed is needed but the 744 produces up to 250mph right at its tail and 200mph 25m behind its tail. With the MD11 you can get 200mph 50m behind the aircraft.
 
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SheikhDjibouti
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Sun Oct 18, 2020 11:04 am

426Shadow wrote:
RJMAZ wrote:
I do expect an 8 blade prop and more powerful engines to be fitted to the C-130 to reduce takeoff run by 20%, improve range by 20% and increase speed by 10%. It will be the first aircraft to remain in production for 100 years.

There is no plan to fit the 8 blade props on the J model. There was for the older models though and it was thoroughly tested. We also tested winglet's on the J model but that kind of died out.

Source: I work at LM Marietta.
I cannot top someone who works at LM, but I can offer the following from two months ago that echoes your point.

I wrote:
The C-130J already has engines with much improved fuel burn, and it already has advanced 6-blade scimitar propellers. Eight blades might seem sexy, but I don't believe they are any more efficient per se

In 2010 a C-130H was fitted with the same Hamilton Sundstrand NP 2000 (8- blade) propellers found on E-2Ds, E-2C Hawkeye 2000s, and even some C-2C Greyhounds. Apart from retrofitting these props to a handful of Antarctic LC-130s, the idea hasn't taken off.

And here is LC-130H 83-0491 showing 4-blades in 2017, and 8-blades in 2018.


Then again, I was put firmly in my place on that thread, so what do I know? :lol:
RJMAZ wrote:
It seems you know little on how props work


viewtopic.php?f=10&t=1449725
Nothing to see here; move along please.
 
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zeke
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Sun Oct 18, 2020 12:04 pm

Trimeresurus wrote:
How are propellers that effective at such thin air of FL300+? What stops something like the Caravan or the King Air(other than pressurization for the people on board) reaching that heights and speeds?


The newer King Airs 200/300/350 are certified to FL350.

I remember seeing a Grob G520 around ADL that would go to FL500 for mapping.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
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zeke
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Sun Oct 18, 2020 12:28 pm

426Shadow wrote:
There is no plan to fit the 8 blade props on the J model. There was for the older models though and it was thoroughly tested. We also tested winglet's on the J model but that kind of died out.

Source: I work at LM Marietta.


Maybe that is C130 specific, the Russians have a rich history in this area.



Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
426Shadow
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Mon Oct 19, 2020 12:00 am

zeke wrote:
426Shadow wrote:
There is no plan to fit the 8 blade props on the J model. There was for the older models though and it was thoroughly tested. We also tested winglet's on the J model but that kind of died out.

Source: I work at LM Marietta.


Maybe that is C130 specific, the Russians have a rich history in this area.





I'm sort of lost as to what 8 blade counter rotating props has to do with the C-130 and A400M. The main reason the Russians to it that way is because they would have issues with ground clearance if they tried a conventional configuration. What I mean is that for some reason a CR prop of 8 blades seems to be inherently smaller in diameter than a conventional 8 bladed prop. I'm sure this has something to do with the increased efficiency of the CR prop in a certain SHP class of engine. Wonder why Airbus didn't do that but instead chose to have 2 different gearboxes for a (first of a kind?) configuration on each wing of one each opposite turning propellers. Of course it helps with torque considerations as well but I think the CR prop might have yielded a higher cruise speed (but probably static thrust which wouldn't help with short takeoffs).
We are all just fanboys, our opinions don't make or break businesses.
 
RJMAZ
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Mon Oct 19, 2020 4:38 am

426Shadow wrote:
There is no plan to fit the 8 blade props on the J model. There was for the older models though and it was thoroughly tested. We also tested winglet's on the J model but that kind of died out.

Source: I work at LM Marietta.

That is not what I have heard.

Around 160 C-130H aircraft will be getting fitted with the 8 blade props along with a major PiP fitted to the engines. More than a dozen aircraft have already been converted. Collins Aerospace own the certification of the props so it would not surprise me Lockheed is being greedy and stubborn.

The RAF were the ones that demanded the C-130J with six blade props. The same thing will happen again as all C-130J operators including Australia know the performance gain of the 8 blade props. Plenty of C-130J aircraft will be needed to be replaced in 10 years time and they will force the issue.

This is getting off topic but many say tilt rotors will replace the C-130 but that will never be the case. It is highly doubtful that a quad tilt rotor will be able to replace the C-130J let alone an improved model. The CN-235 versus the V-22 is the best way to see the weakness of a tilt rotor is. Both aircraft can carry 6000kg of payload approximately 600nm.

Now the bad news. The CN-235 has a MTOW of only 16,100 kg and has two 1,305 kW engines. The V-22 has a MTOW of 27,442 kg and has two 4,590kw engines. To make matters worse the V-22 has only 60% of the cabin size and it is the same size of the 8,000kg MTOW C-212.

The C-130J can carry 15,422 kg of payload 1,800nm with a MTOW of 70t. For a tilt rotor to do this it would have to have a MTOW near the A400M 141,100kg and with engines twice the power of the A400m. That means four 15,000kw engines or six 10,000kw engines. The C-130 will still have a huge market and an improved C-130 will definitely come next decade with an 8 blade prop.
 
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SAAFNAV
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Mon Oct 19, 2020 6:12 am

Horstroad wrote:
GalaxyFlyer wrote:
A C-130 can start another C-130 by parking in front of it and using prop “wash” to windmill the other Herk.

Wouldn't that be possible with jet engines as well? I assume this is a procedure only trained in the military... but I could imagine this might work with commercial jet powered aircraft as well.


It's not only a military procedure. Here is a video of one of my company's aircraft providing a buddy start to an RAF plane. We have also been in the reverse position to receive one.

The FCOM states you can only receive a buddy start from another prop-driven aircraft, but I know at my company we have had a buddy start from either a B727 or an IL-76 (I wasn't there, so not 100% sure on which). When rebels are storming the base, you don't care as much for the FCOM.

There is another procedure called a windmill taxi start - use three engines to accelerate down the runway and do the 'normal' air-start procedure, brake hard, turn back and take off.
Starter turbine or the starter shaft spline has to be removed before that, I believe.

I have no C-130J experience, but I believe those techniques are impossible with the free turbine.

The C-130 _can_ reach F300 or a bit higher, but is really not happy up there. You reach the TIT (turbine inlet temp, akin to the EGT or ITT) and then you have just enough thrust to maintain altitude (absolute ceiling). When you do paradrops, you are limited to 150KIAS for the doors, so it's not like you are even attempting to fly very fast at that alt.

Wrt to the 8-bladed props - I believe it is only legacy models eligible for the NP2000 prop.
It is not only the prop itself, but the mechanical valve-housing (big source of prop related failures) gets replaced with a solid-state version, and the cockpit controls are also swapped.
I can't imagine that the free-turbine is conducive to the same type of system, but I will happily defer to our member from LM on these facts.
CFI/Gr. III, L-382 Loadmaster, ex C-130B Navigator
 
mxaxai
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Mon Oct 19, 2020 7:59 am

426Shadow wrote:
I'm sort of lost as to what 8 blade counter rotating props ... Wonder why Airbus didn't do that ?

Noise and vibration, most likely. The Tu-95 is infamous for its loud props but the An-22 isn't exactly quiet either. Okay for a pure cargo or bomb carrier but not ideal for paratroopers, or troop transport in general.

Btw the TP400 doesn't have two completely different gearboxes, instead one of them has an added "reverse" gear.
 
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SheikhDjibouti
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Mon Oct 19, 2020 2:05 pm

zeke wrote:
426Shadow wrote:
There is no plan to fit the 8 blade props on the J model.


... the Russians have a rich history in this area.


Nice!

But don't forget the Americans and British used contra-rotating props too!.

Most of the American designs only made it as far as prototypes.
I believe the Brits put more aircraft into actual service.

Left to right;
a late model Spitfire (SeaFire) F47, the Avro Shackleton (this one is flying with three engines shut down!), and the ugly duckling is a Gannet AEW3
Nothing to see here; move along please.
 
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zeke
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Mon Oct 19, 2020 4:04 pm

SheikhDjibouti wrote:
the Avro Shackleton (this one is flying with three engines shut down!), and the ugly duckling is a Gannet AEW3


That Shackleton photo is impressive, brings back memories of the Nimrod crash at Toronto. While the Gannet looks ugly, was always impressed by its performance, the ability to stop a prop and shut down a mamba to extend loiter was unique design feature.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
426Shadow
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Mon Oct 19, 2020 6:08 pm

RJMAZ wrote:
426Shadow wrote:
There is no plan to fit the 8 blade props on the J model. There was for the older models though and it was thoroughly tested. We also tested winglet's on the J model but that kind of died out.

Source: I work at LM Marietta.

That is not what I have heard.

Around 160 C-130H aircraft will be getting fitted with the 8 blade props along with a major PiP fitted to the engines. More than a dozen aircraft have already been converted. Collins Aerospace own the certification of the props so it would not surprise me Lockheed is being greedy and stubborn.

The RAF were the ones that demanded the C-130J with six blade props. The same thing will happen again as all C-130J operators including Australia know the performance gain of the 8 blade props. Plenty of C-130J aircraft will be needed to be replaced in 10 years time and they will force the issue.

This is getting off topic but many say tilt rotors will replace the C-130 but that will never be the case. It is highly doubtful that a quad tilt rotor will be able to replace the C-130J let alone an improved model. The CN-235 versus the V-22 is the best way to see the weakness of a tilt rotor is. Both aircraft can carry 6000kg of payload approximately 600nm.

Now the bad news. The CN-235 has a MTOW of only 16,100 kg and has two 1,305 kW engines. The V-22 has a MTOW of 27,442 kg and has two 4,590kw engines. To make matters worse the V-22 has only 60% of the cabin size and it is the same size of the 8,000kg MTOW C-212.

The C-130J can carry 15,422 kg of payload 1,800nm with a MTOW of 70t. For a tilt rotor to do this it would have to have a MTOW near the A400M 141,100kg and with engines twice the power of the A400m. That means four 15,000kw engines or six 10,000kw engines. The C-130 will still have a huge market and an improved C-130 will definitely come next decade with an 8 blade prop.


Read what I wrote and read what you wrote. I said no J models will get 8 blades. I did not say that applied to earlier models.
We are all just fanboys, our opinions don't make or break businesses.
 
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SAAFNAV
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Mon Oct 19, 2020 8:07 pm

Horstroad wrote:
GalaxyFlyer wrote:
A C-130 can start another C-130 by parking in front of it and using prop “wash” to windmill the other Herk.

Wouldn't that be possible with jet engines as well? I assume this is a procedure only trained in the military... but I could imagine this might work with commercial jet powered aircraft as well.


Sorry, the link went AWOL.
Said video of civilian Herc providing a buddy start: https://www.youtube.com/watch?v=bXj0sQzljUw
CFI/Gr. III, L-382 Loadmaster, ex C-130B Navigator
 
RJMAZ
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Tue Oct 20, 2020 10:08 pm

426Shadow wrote:
Read what I wrote and read what you wrote. I said no J models will get 8 blades.

I never said 8 bladed props would get fitted to the J model. Swapping perfectly good 6 blade props to 8 blade props would not be worth the cost of certification.

From the very first post I said a future new build variant. I also said the C-130 would be in production for 100 years meaning another 25 years worth of production to go. It would not be a J model it would have a different letter.

I assume you intentionally mentioned the J model because you are aware of the proposed newer C-130 with 8 blade props and being marketed to current J operators and you can not disclose this? :shhh:

It may have been Pratt trying to find customers for its state of the art NGRT engine.

The C-130J engines are already 25 years old. If the C-130 is coming off the line in 2050 it is very unlikely it will have the current engines and props.
 
mxaxai
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Tue Oct 20, 2020 11:32 pm

RJMAZ wrote:
The C-130J engines are already 25 years old. If the C-130 is coming off the line in 2050 it is very unlikely it will have the current engines and props.

You underestimate how conservative the USAF is. After all, this is the same organization that's fine with operating 50 year old B-52 bombers without an engine upgrade.
 
GalaxyFlyer
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Wed Oct 21, 2020 1:00 am

Not conservative, limited funds for large capital projects
 
RJMAZ
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Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Wed Oct 21, 2020 6:10 am

mxaxai wrote:
RJMAZ wrote:
The C-130J engines are already 25 years old. If the C-130 is coming off the line in 2050 it is very unlikely it will have the current engines and props.

You underestimate how conservative the USAF is. After all, this is the same organization that's fine with operating 50 year old B-52 bombers without an engine upgrade.

Indeed, which is why I doubt the USAF will develop a fancy cleansheet turbofan STOL aircraft for the role. They will just upgrade the C-130 for a tiny fraction of the price or even better get a foreign air force to pay for improvements.

It might not be the USAF that requests new engines. The RAF did request the C-130J to be developed and then the USAF purchased it. The same thing will probably happen again. Some C-130 operators do not have strategic airlifters or heavy lift helicopters. Allowing the C-130 to fly 20% further and operate on runways 20% shorter would provide capability that they could not otherwise afford.

For example a small country might need cargo into fields under 500m and to fly across the Atlantic with 10t. Two types would be needed to be purchased for example a Chinook and A400m combo or a C-27J and C-2 combo. A single fleet of C-130J could not meet the tactical runway requirement or the payload weight across the Atlantic. However an improved C-130 could meet both requirements with a single type. Despite the higher purchase price over the J model it would save a huge amount of money compared to operating two types.

The RAAF for instance now has Chinook, C-27J, C-130J and C-17. Some people (not me) think they should purchase the A400M as the C-17 fleet is getting worked hard. An improved C-130 could replace both the C-27J and C-130J and the longer range will save hours on the C-17 fleet.
 
Okie
Posts: 4177
Joined: Wed Jul 16, 2003 11:30 am

Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Wed Oct 21, 2020 5:45 pm

RJMAZ wrote:
From the very first post I said a future new build variant. I also said the C-130 would be in production for 100 years meaning another 25 years worth of production to go. It would not be a J model it would have a different letter.


I remember looking over one of the first production "J" models on a ramp and a LM rep was blowing and going. Someone asked how long will they keep making the C130?
Comment was when you are riding to work in an autonomous spaceship LM will still be building the C-130.

Looking like he was close.

Okie
 
johns624
Posts: 2868
Joined: Mon Jul 07, 2008 11:09 pm

Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Wed Oct 21, 2020 9:26 pm

RJMAZ wrote:
I also said the C-130 would be in production for 100 years meaning another 25 years worth of production to go. It would not be a J model it would have a different letter.

Maybe 35 years?
 
strfyr51
Posts: 5089
Joined: Tue Apr 10, 2012 5:04 pm

Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Thu Oct 22, 2020 2:11 am

Trimeresurus wrote:
How are propellers that effective at such thin air of FL300+? What stops something like the Caravan or the King Air(other than pressurization for the people on board) reaching that heights and speeds?

And why do the militaries prefer props over jets, considering how popular C-130 is and the size of the A400M(way bigger than many jetliners). Are they less maintenance intensive in the war time than jets? That sounds counterintuitive since jet engines have less moving parts.

SI had about 14000 hours in the P3 and we flew between FL230 and 270 at around 230 KIA We S. which depending on weight was around our Max range fuel Burn. rate. in Transit. for cross country flying. We routnely flew 6-10 hour flights during deployment and flying transcon Conus was about 6 hours westbound depending on the winds ALOFT. We once flew NUQ to ADW in 4:30 but that was with a 130Kt Tailwind at FL270-290. with the C130 having a longer wing and the A4400vhaving an even Longer wing they might fly faster but I doubt they would have the endurance as my longest flight in a P3C was 15.6 hours. with over 7 hours tactical below 5000 ft.
 
426Shadow
Posts: 235
Joined: Tue Sep 11, 2007 8:13 am

Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Thu Oct 22, 2020 6:10 am

RJMAZ wrote:
426Shadow wrote:
Read what I wrote and read what you wrote. I said no J models will get 8 blades.

I never said 8 bladed props would get fitted to the J model. Swapping perfectly good 6 blade props to 8 blade props would not be worth the cost of certification.

From the very first post I said a future new build variant. I also said the C-130 would be in production for 100 years meaning another 25 years worth of production to go. It would not be a J model it would have a different letter.

I assume you intentionally mentioned the J model because you are aware of the proposed newer C-130 with 8 blade props and being marketed to current J operators and you can not disclose this? :shhh:

It may have been Pratt trying to find customers for its state of the art NGRT engine.

The C-130J engines are already 25 years old. If the C-130 is coming off the line in 2050 it is very unlikely it will have the current engines and props.


No. And I can't say much but the replacement C-130 is not going to look anything like any cargo plane you've ever seen.
We are all just fanboys, our opinions don't make or break businesses.
 
GalaxyFlyer
Posts: 6487
Joined: Fri Jan 01, 2016 4:44 am

Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Thu Oct 22, 2020 1:40 pm

If it looks anything like some of the design briefs at the ATA meeting in Nashville about 15 years ago, very true!
 
rlwynn
Posts: 1508
Joined: Fri Dec 15, 2000 3:35 am

Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Thu Oct 22, 2020 7:34 pm

Tje A400 is not exactly quiet. It is by far the loudest plane that flies over here. Only the occasional Antonov is louder but the A400 comes over every day at 32,000ft.
I can drive faster than you
 
mxaxai
Posts: 2058
Joined: Sat Jun 18, 2016 7:29 am

Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Fri Oct 23, 2020 11:38 am

rlwynn wrote:
Tje A400 is not exactly quiet. It is by far the loudest plane that flies over here. Only the occasional Antonov is louder but the A400 comes over every day at 32,000ft.

True, but imagine how loud it would be with counter-rotating props.

The A400M is also fairly quiet at low altitude/low speed but surprisingly loud during cruise. Louder than a GTF on takeoff but not deafening.

I think it's not the overall noise that makes it audible on the ground but rather that much of it is at low frequencies, which propagate further, and that it radiates in all directions whereas jet engines direct that noise to the front and rear. Of course that applies to other props too but the CROR jet engines of the 80s were also cancelled mostly due to noise concerns.
 
Noray
Posts: 151
Joined: Tue Jan 30, 2018 4:28 am

Re: How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Mon Nov 02, 2020 12:35 am

How can turboprops like C-130 and A400M cruise at the same height and speed as jets?

Can they?

While the A400M cruises at the same height and only slightly slower than many jets, the C-130J is clearly slower and can rarely be found at 30,000 feet or above. There are pages listing world records for the C-130J (36,560 feet - 39,052 feet - 40,386 feet), but the typical altitude for real-world C-130Js on long-distance flights I found at adsbexchange.com is 24,000-28,000 ft. A400Ms usually cruise 6,000-8,000 ft higher, often flying ~100 kts faster than C-130s.

I wonder if the slower speed contributes to the C-130s not travelling at the same altitude as jets more often, as they would be obstacles for faster jet traffic.

Trimeresurus wrote:
And why do the militaries prefer props over jets, considering how popular C-130 is and the size of the A400M(way bigger than many jetliners). Are they less maintenance intensive in the war time than jets? That sounds counterintuitive since jet engines have less moving parts.

In addition to what's already been said above, mission profiles of tactical transport aircraft like the C-130 include a higher percentage flown at low altitude than is the case with strategic airlifters (airdrop, low-level flight to evade radar detection, short legs without much time spent at cruise altitude ...) Props are particularly more efficient at low altitude. Passenger comfort doesn't play a large role in military aviation. It's more important to bring as much cargo as possible to a small airfield, be capable of doing steep approaches and climbs to get out of the danger zone fast. The airflow the prop creates over the wings gives additional lift at slow speeds. Jets require larger and more complex flaps in order to reach similar low-speed handling as props.

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