Advanced Medium STOL Transport (AMST) and its predecessors

[dan_inbox]

The C-17 was derived from the YC-15, and Boeing's submission for the C-X competition, the Model 1050, was derived from the YC-14.

as seen at https://www.secretprojects.co.uk/threads/cargo-experimental-c-x-program-designs.2706/

 

[sferrin]

Not sure if this has been answered already, I've read the specs and know they both met Air Force requirements, but is there any evidence they preferred one over the other (YC-14 and YC-15)?

The C-17 evolved from the YC-15, which might be indicative.

Both were McDonnell Douglas products. It would be strange for McDD to develop the C-17 from the YC-14. (Did Boeing have a C-17 competitor?) That said, I could swear I've seen somewhere where the YC-14 was liked more, or showed itself superior, to the YC-15.

The C-17 was derived from the YC-15, and Boeing's submission for the C-X competition, the Model 1050, was derived from the YC-14.

The C-17 requirement was for a longer-legged, higher capacity airplane and I suspect that the YC-15 configuration scaled up better than that of the YC-14. Boeing's C-17 entry was awkward looking and placed a 3rd engine above the tail cargo ramp.

They should have gone with four engines above the wing like this: Maybe there would have been a drag penalty though.

 

[Pioneer]

They should have gone with four engines above the wing like this: Maybe there would have been a drag penalty though.

Agree!

Regards
Pioneer

 

[taildragger]

They should have gone with four engines above the wing like this: Maybe there would have been a drag penalty though.

Agree!

Regards
Pioneer

There must have been some drawback to adding engines outboard of the existing 2 since it's the obvious approach, assuming that an engine of appropriate thrust was available. 3 engines vs 4 brings savings but I wouldn't think that alone would be sufficient to justify placing an engine in the tail above cargo operations. If we discount the MD-11 as a development of the DC-10, it may have been the last clean-sheet big tri-jet design..

 

[sferrin]

They should have gone with four engines above the wing like this: Maybe there would have been a drag penalty though.

Agree!

Regards
Pioneer

There must have been some drawback to adding engines outboard of the existing 2 since it's the obvious approach, assuming that an engine of appropriate thrust was available. 3 engines vs 4 brings savings but I wouldn't think that alone would be sufficient to justify placing an engine in the tail above cargo operations. If we discount the MD-11 as a development of the DC-10, it may have been the last clean-sheet big tri-jet design..

Could have used four F117s, or even just four of the engines the YC-14 used. There were plenty of engine options. It's a head scratcher.

 

[Deleted member 2278]

Tiny snippet of French interest in the YC-15 and the possibility of SNECMA powerplants:

StateDeptcable1976-344441 : Free Download, Borrow, and Streaming : Internet Archive

archive.org

 

[hesham]

From Aviation magazine 1972.

 

[hesham]

From Aviation magazine 1973

 

[hesham]

From Aviation magazine 1974.

 

[hesham]

From Aviation magazine 1975.

 

[Orionblamblam]

D'oh! I just bought the actual original of this Bell AMST concept, a C-130 with four turbojets.

 

[Orionblamblam]

And it has arrived.
https://up-ship.com/blog/?p=49239

 

[td_07]

And it has arrived.
https://up-ship.com/blog/?p=49239

Just to ask, but where did you find these paintings (I also realised you purchase another of an STOL takeoff platform? machine)

Were they from a specific seller on eBay you could recommend? Or were they "scattered" and could only be found after doing some "digging"?

 

[Orionblamblam]

And it has arrived.
https://up-ship.com/blog/?p=49239

Just to ask, but where did you find these paintings

The source for all good things these days: Ebay.

Were they from a specific seller on eBay you could recommend? Or were they "scattered" and could only be found after doing some "digging"?

The AMST and AATS paintings came from one seller, the Hughes hot cycle painting from another, the Lockheed stowed-rotor painting from another. In all cases, they came to my attention almost through sheer dumb luck.

 

[litzj]

is there any design consideration in c17 or amst to prevent fod issue on engine?

 

[Boxman]

is there any design consideration in c17 or amst to prevent fod issue on engine?

At least one measure I am aware of on the C-17A is that its thrust reversers direct flow only upwards and forward, so as to mitigate any additional dust and debris from being kicked up by the reversers and ingested into the engines on rough/unprepared airstrips. Another is the nose gear doors splay open outwards almost (but not quite) horizontally to prevent any dust, gravel, etc., kicked up by the nose gear wheels from being ingested by the engines.

Here's some footage that demonstrates both features nicely.
YouTube: AiirSource Military - "C-17 Globemaster III Reverse Thrust Stunt - Short Field Landing & Backing Up"

 

[Eagle2009]

From my own collection, one of the YC-14 demonstrators at its current residence at the Pima Air & Space Museum.

Picture taken in April 2022.