Allison-powered Brewster Buffalo

[Skyraider3D]

In some Brewster documents there's mention of an Allison-powered Army fighter based on the Buffalo. Has anyone ever seen drawings of this proposal?

 

[hesham]

What is your source Skyraider to can help you ?.

 

[Jemiba]

... Has anyone ever seen drawings of this proposal?

No ! Perhaps an installation similar to the P-40 may have been used ? But the R-1820 radial
was wider, than the Allison, adapting the fuselage to the inline engine probably would have
been no mean task. And the considerable bigger length ahead of the wing quite probably
would have demanded a longer tail.
(spoiled drawings from https://commons.wikimedia.org/wiki/File:Brewster_F2A-1_Buffalo_fighter.svg
and https://commons.wikimedia.org/wiki/File:Curtiss_P-40_3-view.svg)

 

[Skyraider3D]

Ha! That's looking pretty bizarre! Great job

 

[Stargazer]

Neat drawing, Jemiba! Makes me wonder however if that wouldn't have totally upset the center of gravity of the "flying barrel"...

 

[eltf177]

Neat drawing, Jemiba! Makes me wonder however if that wouldn't have totally upset the center of gravity of the "flying barrel"...

\

Looking at that drawing I get the exact same impression...

 

[Jemiba]

Looking at that drawing I get the exact same impression...

Not really sure, as a (very) quick search shows, that the Wright R-1820 engine of the Buffalo had
a weight of 605 kg, the Alison V-1710 of 665 kg. So with regards to engine weight, the difference
wasn't that great, I think.

 

[cluttonfred]

[quote author=Jemiba]Not really sure, as a (very) quick search shows, that the Wright R-1820 engine of the Buffalo had
a weight of 605 kg, the Alison V-1710 of 665 kg. So with regards to engine weight, the difference
wasn't that great, I think.[/quote]

It's not just about weight but also location. A radial engine is relatively short, so the center of gravity of the engine itself is quite close to the firewall. An inline or V engine is much longer, so the center of gravity of the engine is much further from the firewall. 665 kg 12 inches from the firewall is very different than 605 kg 6 inches from the firewall.

 

[Jemiba]

Probably correct, though I have no idea about the weight distribution
With regards to length of an inline engine. It's probably not homogenous.
But exchanging a radial for an inline engine worked quite well in a number
of cases, e.g. for the Fw 190 A to D, Macchi MC.200 to 202 and, mabe as
the most important example, the Curtiss P-36 to the P-40, as here it was a
change from the Wright R-1820 to the Allison V-1710, too.

 

[cluttonfred]

True enough, inline or V to radial swaps were quite common, which is the easier because the radial is usually lighter and always shorter so the right balance can be found by varying the length of the engine mount. Radial to inline or V is harder because either the firewall has to move or the rear fuselage extended to find the right balance.

 

[Stargazer]

I have numerous plans and profiles of the Buffalo from various sources, but somehow none of them seems to have the CG in it!
My intuition is that if a V-1710 engine had been fitted, the whole tail unit would have needed a major redesign, with rear fuselage slightly extended and maybe the cockpit moved a little behind.

 

[Jemiba]

... My intuition is that if a V-1710 engine had been fitted, the whole tail unit would have needed a major redesign, with rear fuselage slightly extended and maybe the cockpit moved a little behind.

Judging several drawings, from the P-36 to the P-40B the tail was more or less unchanged, but the cockpit was
positioned further aft. And the later marks of the P-40 had a considerable longer tail, so we could be on the
right track.

 

[klaud3]

I have numerous plans and profiles of the Buffalo from various sources, but somehow none of them seems to have the CG in it!

I remember from Shavrov book on Soviet aircraft that for fighter of that era CG in some 20-25% of Mean Aerodynamic Chord was the typical range. It could move 2-3% fore and aft as the fuel / ammo was loaded and used up, but crossing 30% was generally considered dangerous. I guess Buffalo was not much different.

 

[Jjr]

Skyraider,
These documents you mention, do they mention in any year of this project?

 

[Manuducati]

Another aircraft to have its radial engine replaced by an in-line one: the North American XAT6E.

 

[Jjr]

interresting, but concerning the Brewster the year of the documents please?

 

[riggerrob]

I have numerous plans and profiles of the Buffalo from various sources, but somehow none of them seems to have the CG in it!

I remember from Shavrov book on Soviet aircraft that for fighter of that era CG in some 20-25% of Mean Aerodynamic Chord was the typical range. It could move 2-3% fore and aft as the fuel / ammo was loaded and used up, but crossing 30% was generally considered dangerous. I guess Buffalo was not much different.

When the center of gravity is aft or more than 30 or 35 percent of the wings' mean aerodynamic chord, you risk deep stalls and unrecoverable spins. This line usually equates to the thickest part of the wing and the center of lift.
When stall and spin testing at aft C. of G. is when many prototypes. Modern test-flying programs use drag chutes or moveable ballast to reduce risks during stalling and spinning.

 

[riggerrob]

I have numerous plans and profiles of the Buffalo from various sources, but somehow none of them seems to have the CG in it!
My intuition is that if a V-1710 engine had been fitted, the whole tail unit would have needed a major redesign, with rear fuselage slightly extended and maybe the cockpit moved a little behind.

When replacing engines, there is a progression of "fixes" to compensate for changes in balance. Just ask the engineers at Soloy or Raisbeck or Texas Turbines.
It starts with lengthening (lighter engine) or shortening (heavier engine) engine mounts ... along with a modified cowling, etc.
The second step requires moving heavy items like batteries or radios into the rear fuselage, etc.
For example, when Conair converted ex-RCN Grumman Trackers to turboprops, the installed the new propellers at the same location as the old, but the new turboprop engines were much lighter. This un-balance the airplane ... too far aft. So Conair removed a whole bunch of heavy naval components that were no longer needed: tail hook, tail bumper, MAD boom, radome, etc. Lastly, Conair extended the nose cone to make space for forward ballast.
Since moving cockpits requires reconfiguring hundreds or thousands of parts, it is only done on new production variants.

 

[riggerrob]

Neat drawing, Jemiba! Makes me wonder however if that wouldn't have totally upset the center of gravity of the "flying barrel"...

Yes.
Consider that radial engines only have one or two throws on their crankshafts, they balance like single or two cylinder in-line engines, with their centers of gravity close to the firewall.

This reminds me of a friend who was building a plywood Chilton DW-1 airplane in his basement. He dismissed the original (1930s vintage) Ford auto engine conversion for producing too few horsepower (40 hp.). He wanted to install a more reliable and more powerful (say 80 horsepower) 4-cylinder, modern engine like a Walter Mikron or Jabiru.
The Walter Mikron engine is a straight, inline with 4 throws on its crankshaft, shifting the engine's center of gravity a long way forward of the firewall. A few Chiltons are flying with Walter Mikron engines, but some need ballast in the aft fuselage.

In comparison, the Jabiru has 4 horizontally-opposed cylinders and a shorter crankshaft. While the Jabiru still has 4 separate throws on its crankshaft, there is considerable overlap between left and right cylinders so the Jabiru crankshaft is shorter and the Jabiru's center of gravity is closer to the firewall.

 

[T. A. Gardner]

Looking at that drawing I get the exact same impression...

Not really sure, as a (very) quick search shows, that the Wright R-1820 engine of the Buffalo had
a weight of 605 kg, the Alison V-1710 of 665 kg. So with regards to engine weight, the difference
wasn't that great, I think.

You have to add in the cooling system for the Allison. That adds several hundred more pounds to the weight. I doubt that it could be managed in a Buffalo. The plane was a tight design as it was.

 

[Nik]

Getting to stage of jacking up throttle quadrant and sliding a new plane underneath...

 

[robunos]

A place to start would be to study what Curtiss did to turn the P-36 into the P-40 . . .

cheers,
Robin.

 

[T. A. Gardner]

Of note here, the Brewster did give some consideration to installing the similar in weight P&W Twin Wasp engine (as was done in the F4F by Grumman) but found that a major redesign would be needed due to the engine being longer and more off-center than the Cyclone.

 

[airman]

I'm trying to find something about it , but sincerely sounds like " what if " . None of the books about Brewster Buffalo speaks about this proposal .

 

[pathology_doc]

In Jemiba's post of April 7 2016, the image given shows something so close to the P-40 that had it been built and flown, Brewster might have been upbraided for trying to reinvent the wheel.

 

[T. A. Gardner]

Most likely, even if Brewster did manage to mate an Allison to their airframe, the question would become Who would the customer be? The USN was pretty much wedded to using air cooled radials on their planes due to limitations on fresh water aboard ships. The US Army already had the P-40, why switch?

 

[Apophenia]

Most likely, even if Brewster did manage to mate an Allison to their airframe, the question would become Who would the customer be? ...

True. One possibility is an export pitch to France. (The French regarded the Allison as a foreign backup to their HS 12Y - hence the Arsenal VG-32 fighter powered by a V-1710C-15.) To put it mildly, such a pitch would have been a long-shot ...

 

[TomcatViP]

What about the in-line engine inside the original cowling, slightly extended, and a plug in the tail forward of the vertical...
Something akin to Brewster D-9

 

[Craig Raahauge]

What about the in-line engine inside the original cowling, slightly extended, and a plug in the tail forward of the vertical...
Something akin to Brewster D-9

... Has anyone ever seen drawings of this proposal?

No ! Perhaps an installation similar to the P-40 may have been used ? But the R-1820 radial
was wider, than the Allison, adapting the fuselage to the inline engine probably would have
been no mean task. And the considerable bigger length ahead of the wing quite probably
would have demanded a longer tail.
(spoiled drawings from https://commons.wikimedia.org/wiki/File:Brewster_F2A-1_Buffalo_fighter.svg
and https://commons.wikimedia.org/wiki/File:Curtiss_P-40_3-view.svg)

The book “ Vee’s for Victory “ ( ISBN: 0-7643-0561-1 ) page 183 refers to Brewster Model P22 proposal to U.S. army of February 1939 as being based on the F2A-1 with Allison V1710-C15 engine of 1150 bhp Being similar in size to a P39. In March 1940 Brewster offered a similar proposal ( Model P-29 - based on the F2A-2 ) to the French Purchasing Commission. Neither proposal went anywhere. Given the use of V1710-C15 engine using epicyclic propeller gearing , it is quite possible that the engine nose profile would have resembled Curtiss early P40B/C rather than later P40 D/E which used later Allison models using spur gears for propeller reduction giving higher thrust line.

 

[tomo pauk]

The book “ Vee’s for Victory “ ( ISBN: 0-7643-0561-1 ) page 183 refers to Brewster Model P22 proposal to U.S. army of February 1939 as being based on the F2A-1 with Allison V1710-C15 engine of 1150 bhp Being similar in size to a P39. In March 1940 Brewster offered a similar proposal ( Model P-29 - based on the F2A-2 ) to the French Purchasing Commission. Neither proposal went anywhere. Given the use of V1710-C15 engine using epicyclic propeller gearing , it is quite possible that the engine nose profile would have resembled Curtiss early P40B/C rather than later P40 D/E which used later Allison models using spur gears for propeller reduction giving higher thrust line.

Thanks for the details wrt. V-1710 on Brewster projects.
Please note that V-1710 C15 used the 'internal spur' reduction gear, not the epicyclic, that is commonly found on radial engines.

 

[riggerrob]

... Has anyone ever seen drawings of this proposal?

No ! Perhaps an installation similar to the P-40 may have been used ? But the R-1820 radial
was wider, than the Allison, adapting the fuselage to the inline engine probably would have
been no mean task. And the considerable bigger length ahead of the wing quite probably
would have demanded a longer tail.
(spoiled drawings from https://commons.wikimedia.org/wiki/File:Brewster_F2A-1_Buffalo_fighter.svg
and https://commons.wikimedia.org/wiki/File:Curtiss_P-40_3-view.svg)

Since you cannot make that fin much bigger, an Allison-powered Buffalo, definitely needs a longer tail to return stability with that huge radiator forward of the center of lateral area.

Alternately, you could relocate radiators farther aft, either under the wings (ala. Spitfire or Me.109) or under the aft fuselage (ala. P-51 Mustang).

 

[tomo pauk]

Alternately, you could relocate radiators farther aft, either under the wings (ala. Spitfire or Me.109) or under the aft fuselage (ala. P-51 Mustang).

Relocating the radiator aft, like it was done on Italian radial->V12 conversions would've probably be the best - there is a lot of volume to play with, drag from radiators might be lower, and there is no messing with airflow around the wings.

But, boy, would it not be one ugly aircraft, the V12 powered Buffalo.

 

[Jemiba]

...

Alternately, you could relocate radiators farther aft, either under the wings (ala. Spitfire or Me.109) or under the aft fuselage (ala. P-51 Mustang).

Just another quick and dirty attempt to visualize such a thing.

But, as we are straying really out of reality in the moment, would it be ok, if we move the discussion to the alternative section ? Actually, I'm surprised, that still yet there wasn't a report demanding that ..

 

[TomcatViP]

Given the front diameter of the radial engine, you probably wouldn't need to streamline the cowling, unless adding a consequent stretched section.

Wouldn't be more realistic to just extend the circular section that it enclosed the full length of the Allison? Something partially conical, with a radial radiator at the end, would be even more cool.

 

[Antonio]

There is an interesting picture composition here

https://www.talkbass.com/threads/for-aircraft-enthusiasts-strange-mutations-of-the-curtiss-p-40-warhawk.1263523/

Brewster should have considered a similar approach of that Curtiss P36 to XP40

 

[riggerrob]

Given the front diameter of the radial engine, you probably wouldn't need to streamline the cowling, unless adding a consequent stretched section.

Wouldn't be more realistic to just extend the circular section that it enclosed the full length of the Allison? Something partially conical, with a radial radiator at the end, would be even more cool.

A radial/annular radiator (ala later Focke Wulf 190) might look "cool" but it would exacerbate problems with balance and yaw control.
Far better to mount the radiator in the aft fuselage to reduce lateral area forward of the center-of-gravity.

Mounting the radiator in the aft fuselage would also help balance the longer inline engine. Inline engines are always going to force the center of engine mass farther forward of the firewall than a radial engine.
This notion comes from a conversation with a friend who was building a modern Chilton DW-1. He was mulling over the choice of engine. Since the original 1930s Ford automobile, water-cooled, straight 4 is almost impossible to find these days, he was trying to decide between modern engines specifically built for light sport aircraft. He narrowed his decision to a Walter Mikron inverted inline 4 cylinder or a Jabiru horizontally opposed engine. The Walter would have produced a more "classic" cowling, but created balance problems because the engine's center-of-gravity is so far forward of the firewall. He eventually chose the Jabiru based upon its shorter overall length.

 

[TomcatViP]

Very true. It wouldn't have been possible without an aft fuselage plug and probably mass balance and rudder enlargement.

Let's think at the C-3605 (which resulted from slightly opposite constraints) :

 

[GTX]

Given the front diameter of the radial engine, you probably wouldn't need to streamline the cowling, unless adding a consequent stretched section.

Wouldn't be more realistic to just extend the circular section that it enclosed the full length of the Allison? Something partially conical, with a radial radiator at the end, would be even more cool.

or perhaps something similar to the arrangement on the AVRO Shackleton?

 

[ZacYates]

Let's think at the C-3605 (which resulted from slightly opposite constraints) :

Personal taste but I'd rather forget it!

 

[riggerrob]

Given the front diameter of the radial engine, you probably wouldn't need to streamline the cowling, unless adding a consequent stretched section.

Wouldn't be more realistic to just extend the circular section that it enclosed the full length of the Allison? Something partially conical, with a radial radiator at the end, would be even more cool.

or perhaps something similar to the arrangement on the AVRO Shackleton?

MEW
Mounting the radiator on the extreme nose will exacerbate balance problems.