"Stretch or not strech" of aircraft designs

[tomo pauk]

Would it have been possible to stretch the Me 109 design like the Fw 190? Lengthening the fuselage to carry more armament and fuel, enlarging the wings to carry the weight. Obviously the undercarriage would have to change to a broad one, too. They would have had to strenghten the structure considerably as the 109 was not nearly as rugged as the 190.

The Me-209 looks the part, with it's enlarged (but still not too big) wing and a much better undercarriage.

Why did they not develop the A6M Zero further to be competitive?

Probably a combination of shortsightedness, overload of Mitsubishi's design department, and Japanese aero industry lagging back vs. West (USA, UK, Ge). Japan was not as rich & developed as the 3 leading Western countries, meaning that best engines went into 2-engined bombers 1st, instead of Anglo-American practice of making 4-engined bombers powered by widely-available engines.

 

[spicmart]

Despite being quite a small (wet area-wise) airframe tomo once said that it was THE fighter airframe of WW2.
Why is that that it was capable of so much stretch, arguably the most if you compare it to other fighters?

 

[tomo pauk]

Despite being quite a small (wet area-wise) airframe tomo once said that it was THE fighter airframe of WW2.
Why is that that it was capable of so much stretch, arguably the most if you compare it to other fighters?

Which one is that?
Among other a few fighters, I'm the admirer of the Fw 190's airframe.

 

[spicmart]

Which one is that?
Among other a few fighters, I'm the admirer of the Fw 190's airframe.

Sorry, I meant the Fw 190.

 

[Shortround6]

Would it have been possible to stretch the Me 109 design like the Fw 190? Lengthening the fuselage to carry more armament and fuel, enlarging the wings to carry the weight. Obviously the undercarriage would have to change to a broad one, too. They would have had to strenghten the structure considerably as the 109 was not nearly as rugged as the 190.

The 109 had also seen considerable "stretch", at least in weight growth if not actual dimensions. Let's remember that it was designed as a two gun (or one cannon) fighter using a 20 liter (600-700hp) engine and weighing under 2000kg. The Jumo engined planes were NOT interim planes while they waited for the DB engine, nearly 1000 Jumo 210 powered planes were built. At some point is not wise/worthwhile to keep 'stretching" an airframe and it is better to start over. On the 209-II they got to a point where only 30% of the airframe was common to the 109G and that is what killed the project, they were looking for a plane that could be put into production with only a small disruption in production and the 209-II had ceased to be that plane once all the desired modifications had been made. It might have been a very good airplane, nobody knows. But Germany could not afford the loss of hundreds of aircraft per month for several months as the production was changed over.

Why did they not develop the A6M Zero further to be competitive?

Lack of engineers and engineering staff. (plus politics?)

The designer of the Zero (and some of the staff) had started on what would be the A7M Reppu in 1940 although project was quickly shelved (no suitable engine) while the staff worked on the A6M3 and the J2M. Project was restarted in April of 1942. Again the staff had to also work on later versions of the A6M, the G4M and the J2M so work was slow.
At any given point in time the priorities between the new fighter/s and the improved model/s of the zero changed back and forth depending on the war situation.
Compounding this was the availability of suitable engines. You had a Mitsubishi airframe powered by a Nakajima engine which Mitsubishi was not happy about. But trying to get the Japanese navy to agree to change to a Mitsubishi engine (the only one with a hope of fitting) doesn't seem to gone well until the very end of the war. The "improved" Nakajima engines never seemed to meet the promised goals?
How much politics played a part in the engine selection I don't know. The larger heavier Mitsubishi engine might have robbed some of the range from the A6M.

 

[spicmart]

I was wondering about the A7M Reppu as the successor to the Zero as it was a very large aircraft.
The trend at the end of the war was towards smaller-sized fighters
(F8F Bearcat).
The power-to-weight ratio would decrease with airplane size and so would flight performance and agility.
But what were the advantages?

 

[Shortround6]

You are confusing the timing. The early to mid war trend was to larger fighters, the F6F and F4U for example.

The F8F was NOT an example of a trend but rather a special used fighter, Grumman already had the F7F in the works for large carriers (of which there were few) but needed a replacement for the F4F/FM2 for small carriers, of which there were many.

 

[spicmart]

Okay. But the Japanese did plan the deployment of the Reppu? Flight wise it would have been hopelessly outclassed by the Bearcat I assume.

 

[Ivan1GFP]

The Jumo 213 weighed less than the BMW 801. I'm not sure if it really lost that much roll rate as the effective increase of inertia would still be at the centerline , so it should not have been to great. But I'm so physicist. But the Dora turned better than the Anton due to better power-to-weight ratio and aerodynamics. It's right hand turn at speed almost matched the Spitfire XIV's.

Hello Spicmart,

I am not so sure that is really a valid conclusion.
The FW 190D-9 weighed about 50 kg less than the FW 190A-8 but the standard armament did not include the outboard wing cannon which would have more than made up the difference. Perhaps the JuMo 213 weighed less than the BMW 801, but one cannot conclude that from the aircraft weights.
There was apparently a slight decrease in roll rate.
The next part is speculation on my part: I believe it might have had something to do with a change in alignment between the center of mass and center of form with the new engine. That might explain why an overall decrease in weight along with a deletion of outboard wing armament did not increase roll rate.

- Ivan.

 

[Shortround6]

Okay. But the Japanese did plan the deployment of the Reppu? Flight wise it would have been hopelessly outclassed by the Bearcat I assume.

You may be right but the Japanese did not have an engine of the same class as the R-2800-C which the Bearcat used.
The C series R-2800 used just about no interchangeable parts with the B series engines used in the F6F-3 or F4U-1s aside from a few nuts, bolts, washers and perhaps the starter dog.
The Japanese also didn't have 115/145 fuel which the post war Bearcats ran on.
Make sure you are using the performance numbers for the early F8F-1 Bearcat.

The A7M was much more of a match for the F6F in concept.

 

[spicmart]

The A7M was much more of a match for the F6F in concept.

That's what I thought seeing the specs.

 

[michael rauls]

Perhaps an oversimplification but I've often thought you could continue to develop just about anything indefinitely(within reason) by lengthening the fuselage to keep the COG after adding the disired aditional fuel, power, etc.
This approach seemed to work pretty well for several types like the p40. Ya, I know, we don't normally think of the p40 as being a stretched/ much improved design but if you consider where it started by the time it got to the p40 f/L it really had come a very long way from the pre p36 origins.

 

[Shortround6]

Perhaps an oversimplification but I've often thought you could continue to develop just about anything indefinitely(within reason) by lengthening the fuselage to keep the COG after adding the disired aditional fuel, power, etc.
This approach seemed to work pretty well for several types like the p40. Ya, I know, we don't normally think of the p40 as being a stretched/ much improved design but if you consider where it started by the time it got to the p40 f/L it really had come a very long way from the pre p36 origins.

The thing with the P-40 is that any additional "length" was to accommodate the V-12 engine and for aerodynamic reasons. There was no real change in fuel capacity, the Hawk75/P-36 could hold about 160 gallons if the overload/ferry tank behind the pilot was filled. The later versions got a longer tail (20 inches) instead of a larger vertical stabilizer. The horizontal stabilizers and elevators stayed in the original position, Only the vertical stabilizer, rudder (and tail wheel?) moved. and it was not for CG reasons.
The P-40 did come a long way from the pre P-36 aircraft but the wing stayed the same size/shape, It got quite few pounds heavier to take the increased loads.
The fuselage guns migrated to the wings (on the CG) so no stretch was required for armament.

 

[michael rauls]

The thing with the P-40 is that any additional "length" was to accommodate the V-12 engine and for aerodynamic reasons. There was no real change in fuel capacity, the Hawk75/P-36 could hold about 160 gallons if the overload/ferry tank behind the pilot was filled. The later versions got a longer tail (20 inches) instead of a larger vertical stabilizer. The horizontal stabilizers and elevators stayed in the original position, Only the vertical stabilizer, rudder (and tail wheel?) moved. and it was not for CG reasons.
The P-40 did come a long way from the pre P-36 aircraft but the wing stayed the same size/shape, It got quite few pounds heavier to take the increased loads.
The fuselage guns migrated to the wings (on the CG) so no stretch was required for armament.

From what I've read even if the tail was not lengthened for COG reasons it did have a positive effect in that regard( if unintentional) as pre-lengthening p40s were apparently quite squirrely and after pretty stable. At least that's the impression I've gotten from pilots quotes so I always assumed it was lengthened for that reason.

 

[Ivan1GFP]

From what I've read even if the tail was not lengthened for COG reasons it did have a positive effect in that regard( if unintentional) as pre-lengthening p40s were apparently quite squirrely and after pretty stable. At least that's the impression I've gotten from pilots quotes so I always assumed it was lengthened for that reason.

Hello Michael Rauls,

I don't know as much about the P-36 as I would like, but from a comparison of drawings, it appears to me that the change to P-40 was a bit more than a simple engine swap. There were a few construction or dimensional changes as well and they can be seen by comparing a drawing of a P-36 and early P-40. From diagrams, it also appears that at least the fuselage fuel tank and tail wheel changed slightly as well.
The early P-40 only had about 1150 HP.
The P-40E and P-40K had engines that could be over boosted to give in the neighborhood of 1550-1600 HP at low altitude and that made them a bit difficult to control at low speeds. The same thing was probably happening with the P-40F with a Merlin engine.
With the P-40K, a few things were tried: A large fillet added to the fin and then just moving the fin and rudder back 20 inches as Shortround6 described. The horizontal tail and tail wheel were unchanged.
The longer tail did improve directional stability and control, but I believe that the lower absolute engine power of the later versions might also have given the impression that the longer tail helped things more than it actually did.
The additional weight at the tail would if anything have made the aircraft LESS stable, but later engines also added extra weight up front and that would have affected the CoG.

- Ivan.

 

[spicmart]

So I see it that virtually any design has stretch. But the potential of "how much" depended on the basic design. Its dimensions, construction properties of wings and fuselage, location of cooling devices, weapons, fuel tanks, landing gear configuration etc.. All these interact and influence the extent to which modifications were possible to push the evolution further.
Planes which become "obsolete" obviously reach a level faster where it would be easier and more feasible to go with a whole new desgin.
A case where it becomes a separate machine was e.g. the Me 209 V5 which incorporated not enough common parts to the Me 109 to warrant production, other than to not offering any advantages to its competitor Fw 190D.

But how would you describe a Yak-3, Bearcat or Sea Fury? Are they "shrinkage" versions of the Yak-9, Hellcat and Tempest?

 

[pinsog]

So I see it that virtually any design has stretch. But the potential of "how much" depended on the basic design. Its dimensions, construction properties of wings and fuselage, location of cooling devices, weapons, fuel tanks, landing gear configuration etc.. All these interact and influence the extent to which modifications were possible to push the evolution further.
Planes which become "obsolete" obviously reach a level faster where it would be easier and more feasible to go with a whole new desgins.
The case where it becomes a separate machine was e.g. the Me 209 V5 which incorporated not enough common parts to the Me 109 to warrant production, other than to not offering any advantages to its competitor Fw 190D.

But how would you describe a Yak-3, Bearcat or Sea Fury? Are they "shrinkage" versions of the Yak-9, Hellcat and Tempest?

I think the bottom 3 would be referred to as clean sheet designs. About all the Bearcat shares with the Hellcat is the engine type and the paint. I believe the same applies to the Sea Fury and Tempest. I know very little about the Soviet aircraft

 

[Ivan1GFP]

I think the bottom 3 would be referred to as clean sheet designs. About all the Bearcat shares with the Hellcat is the engine type and the paint. I believe the same applies to the Sea Fury and Tempest. I know very little about the Soviet aircraft

Hello Pinsog,

I believe Spicmart is more or less correct for two of the three types he listed.
The Yak-3 isn't too different from the Yak-1M and was developed from it.
The Sea Fury actually WAS a more refined and lightened Tempest Mk.II.
The Bearcat didn't even share an engine with any production version of the Hellcat though.

- Ivan.

 

[pinsog]

Hello Pinsog,

I believe Spicmart is more or less correct for two of the three types he listed.
The Yak-3 isn't too different from the Yak-1M and was developed from it.
The Sea Fury actually WAS a more refined and lightened Tempest Mk.II.
The Bearcat didn't even share an engine with any production version of the Hellcat though.

- Ivan.

Interesting.
I knew the Hellcat and Bearcat shared the R2800 and that it wasn't the same model R2800. I should have typed a bit more.

I didn't realize the Tempest and Sea Fury shared much of anything.

 

[pbehn]

In many cases the chance to improve performance was given up simply to get more planes. The planned development of the Spitfire and the actual production were almost strangers to each other.