Improve That Design: How Aircraft Could Have Been Made Better

Shortround6 · Jun 26, 2019

P-39 Expert said:
Thanks for the info. So from about 1941 through the rest of WWII the .50 remained about the same?

For all practical purposes yes, for winning bar bets no.

The US was trying desperately to raise the rate of fire to 1200rpm or so, several different manufacturers involved with many different model guns. US Ordnance was unwilling to relax the reliability standards (number of stoppages and broken parts per 5,000 rounds) By late 1944 they got near to what they wanted and around 8,000 guns were built using a "T" number. this was standardized as the M3 gun but very few saw combat. You could not turn an M2 into an M3 with a parts kit., one of the original requirements. The receiver itself needed to be modified. The M3 did see widespread use in the Korean war.

The US also introduced the M8API round in late 43 or 44 to cut down on the mixed belts of AP and separate incendiary rounds.
What would become the M23 incendiary round was also developed and tried/trialed in combat during WW II but with limited success. The bullet used a much thinner tube (or just used the bullet jacket itself to contain the incendiary mixture) so it carried much more incendiary mixture than other .50 incendiary bullets and the lighter weight allowed higher velocity. However the light jacket may have been the source of premature ignition (sometimes in the gun barrel and all to often right in front of the gun barrels.
Several small redesigns and at least two changes of manufacturer in an attempt to improve quality control saw the M23 round being used in considerable numbers in Korea.

This is from memory so a few details might be off but that is the general story of development from 1941/42 on.

P-39 Expert · Jun 27, 2019

Shortround6 said:
For all practical purposes yes, for winning bar bets no.

The US was trying desperately to raise the rate of fire to 1200rpm or so, several different manufacturers involved with many different model guns. US Ordnance was unwilling to relax the reliability standards (number of stoppages and broken parts per 5,000 rounds) By late 1944 they got near to what they wanted and around 8,000 guns were built using a "T" number. this was standardized as the M3 gun but very few saw combat. You could not turn an M2 into an M3 with a parts kit., one of the original requirements. The receiver itself needed to be modified. The M3 did see widespread use in the Korean war.

The US also introduced the M8API round in late 43 or 44 to cut down on the mixed belts of AP and separate incendiary rounds.
What would become the M23 incendiary round was also developed and tried/trialed in combat during WW II but with limited success. The bullet used a much thinner tube (or just used the bullet jacket itself to contain the incendiary mixture) so it carried much more incendiary mixture than other .50 incendiary bullets and the lighter weight allowed higher velocity. However the light jacket may have been the source of premature ignition (sometimes in the gun barrel and all to often right in front of the gun barrels.
Several small redesigns and at least two changes of manufacturer in an attempt to improve quality control saw the M23 round being used in considerable numbers in Korea.

This is from memory so a few details might be off but that is the general story of development from 1941/42 on.

Thanks.

Thos9 · Jun 27, 2019

Ivan1GFP said:
I believe the Mitsubishi A6M Type 0 would have done quite a bit better if the initial design had gone with the Mitsubishi Kinsei engine instead of the Nakajima Sakae. It may not have had quite the same range and agility, but would have stayed as a viable fighter for much longer.
The Japanese eventually came to the same conclusion when they fitted the Kinsei to the A6M8 but it might have been a whole lot better if it had been done 5 years earlier.

I also believe that the FW 190 series should have gotten an increase in the size of its wing. In the prototype stage, it had already gone from a 160 ft^2 wing to 197 ft^2 wing but weight increased substantially with production models and the size of the wing did not change. It also meant that if not properly flown, it had a tendency to

mush. A wing with increased span may have improved the issue and as seen with the

Ta 152 series, it did not drastically affect the roll rate.

Thoughts?
- Ivan.

The FW190A-6 of early 1943 actually had a new wing of lighter construction but very similar (not identical)dimensions th the A-5. Instead a larger wing should have been adopted as you suggest. The A-10 projected in October 1943 but apparently not built would have had a larger wing of 37'8'' and 220 square feet.

For other A series improvements
- change the supercharger drive to hydraulic constant boost a la DB engines
- fit MW and uprated 801 engines as available (E, TS, F )
- remove all guns and ammunition from the fuselage to the wings
- fit an MW tank in place of the fuselage guns
- extend the forward fuel tank forward to the main spar in place of the inner cannon mags
- extend the aft fuel tank upwards behind the pilot a la Bf 109
- allow for wing radiators and a liquid-cooled engine (DB603 or Jumo 213) in a streamlined nose with better downward vision and sighting
- fit an EZ42 or 45 gyro sight as available
- allow for 4 MG213A guns in 20mm or 24mm versions as available
- fit wing fuel tanks as space allows.

tomo pauk · Jun 27, 2019

Thos9 said:
The FW190A-6 of early 1943 actually had a new wing of lighter construction but very similar (not identical)dimensions th the A-5.
...

A lighter wing on the A-6 - interesting. Care to share some good data/sources on it?

For other A series improvements
- change the supercharger drive to hydraulic constant boost a la DB engines

Why would we do it?

- fit MW and uprated 801 engines as available (E, TS, F )

Yes, the 801E was much improved engine, especially of note being it's supercharger.

- remove all guns and ammunition from the fuselage to the wings
- fit an MW tank in place of the fuselage guns

I'd indeed remove fuselage guns & their ammo. OTOH, cannon ammo between the engine and all of fuselage internals was protected from enemy fire - relocating that ammo to wing warrants armor plating it.
BMW 801 was not in dire need for MW 50 - C3 fuel gave anything needed down low, while there was not much worth of supercharging at high altitudes to matter for MW 50.

- extend the forward fuel tank forward to the main spar in place of the inner cannon mags
- extend the aft fuel tank upwards behind the pilot a la Bf 109
- fit wing fuel tanks as space allows.

All of that likely doubles the internal fuel tankage. All good an well, but a much better engine is now needed to provide performance.

- allow for wing radiators and a liquid-cooled engine (DB603 or Jumo 213) in a streamlined nose with better downward vision and sighting

Just having 603 or 213 instaled as-is by late 1943 improves things by a large margin. Wing radiators will clash with undercarriage legs, and/or with guns/ammo/new fuel tanks?

Zipper730 · Jun 28, 2019

I remember reading about the P-39's carburetor intake having almost no ram-compression benefit: Could some kind of bifurcated layout have worked? I remember it being used on the F4U and it provided decent ram-compression...

Thos9 · Jun 28, 2019

tomo pauk said:
A lighter wing on the A-6 - interesting. Care to share some good data/sources on it?
An article by William Green in Flying Review International in my library which is in NZ and I in France until August - I will look it out then and post.
Why would we do it?

First - hydraulic drive maintains constant boost (and hence steadily increasing performance) up to critical altitude, whereas a mechanical two-speed delivers falling boost and performance up to speed-change altitude. That is why the Grumman F8F-2 used the R2800-30 replacing the -22 and -34 and reached 447mph at 26,000 feet.
Second - the 801D and E both had a critical altitude of 18,700 feet (D 1,440hp, E/TS 1700hp) and the target set operated upwards of 25,000 feet. The DB603E had a critical altitude of 23,000 feet (1,550hp - 1,900 at 18,000 with MW).

Yes, the 801E was much improved engine, especially of note being it's supercharger.

I'd indeed remove fuselage guns & their ammo. OTOH, cannon ammo between the engine and all of fuselage internals was protected from enemy fire - relocating that ammo to wing warrants armor plating it.
Yes - the spar also protects.

BMW 801 was not in dire need for MW 50 - C3 fuel gave anything needed down low, while there was not much worth of supercharging at high altitudes to matter for MW 50.
C3 (96-100 octane) was from mid 1944 up against 150 octane down low. With hydraulic drive the 801 would profit from MW up to 20K or more -its supercharger was of 331mm diameter cf 320 for the 603E.

All of that likely doubles the internal fuel tankage. All good an well, but a much better engine is now needed to provide performance.
See above.

Just having 603 or 213 instaled as-is by late 1943 improves things by a large margin. Wing radiators will clash with undercarriage legs, and/or with guns/ammo/new fuel tanks?

No clash with u/c or guns/ammo. Radiators would displace some potential tankage. An aircooled engine had advantages esp re vulnerability and in Jabo role.

[

P-39 Expert · Jun 28, 2019

Zipper730 said:
I remember reading about the P-39's carburetor intake having almost no ram-compression benefit: Could some kind of bifurcated layout have worked? I remember it being used on the F4U and it provided decent ram-compression...

The P-63 had a more streamlined carb intake with a boundary layer splitter. Should have been easily adapted to a P-39.

Shortround6 · Jun 28, 2019

Guys, see : http://www.wwiiaircraftperformance.org/P-39/P-39D_41-6722_PHQ-M-19-1325-A.pdf

In level flight at over 360mph (plane hit 368mph) the P-39D could hold 1150hp to 13,800ft.
When climbing at about 190mph it could hold 1150hp to 12,400hp.

Allison rated the engine at 1150hp at 12,000ft no RAM so obviously some RAM was being generated in level flight. At a higher angle of attack, like when climbing, perhaps the canopy did mask the intake some what. Or perhaps the P-40 system was better but obviously picking up 1800ft of altitude shows that the claim of "almost no ram-compression benefit " is false.

tomo pauk · Jun 30, 2019

Thos9 said:
An article by William Green in Flying Review International in my library which is in NZ and I in France until August - I will look it out then and post.

Okay, thanks in advance

First - hydraulic drive maintains constant boost (and hence steadily increasing performance) up to critical altitude, whereas a mechanical two-speed delivers falling boost and performance up to speed-change altitude. That is why the Grumman F8F-2 used the R2800-30 replacing the -22 and -34 and reached 447mph at 26,000 feet.

Hydraulic drive also 'steals' power at lower altitudes (not just due to the slip), adds up to oil cooling requirement, and does nothing above the rated altitude. Fw 190 was already excellent under 20000 ft, it needed a much improved altitude power above 20000 ft once P-47s (and especially Merlin Mustangs) came in knocking. Better spend resources to make a better S/C.
The R-2800-30 was an E series engine, vs. -22 and -34 being C series engine - post war vs. wartime. Apart from internals being modified and improved, it also spinned it's (better? bigger? both?) S/C at up to 10.55 times the crankshaft rotation speed, while the -22 and -34 were doing it at max 9.45 times the crankshaft speed. Faster S/C means better altitude power, that usually means greater speed.

Second - the 801D and E both had a critical altitude of 18,700 feet (D 1,440hp, E/TS 1700hp) and the target set operated upwards of 25,000 feet. The DB603E had a critical altitude of 23,000 feet (1,550hp - 1,900 at 18,000 with MW).

The DB 603E can't help in 1943, it was a rare engine even in 1944. It's good altitude power was not a fruit of having a hydraulic drive, but rather of great displacement, good RPM for that displacement, and improved S/C.

C3 (96-100 octane) was from mid 1944 up against 150 octane down low. With hydraulic drive the 801 would profit from MW up to 20K or more -its supercharger was of 331mm diameter cf 320 for the 603E.

C3 in 1944 was more or less equal to the Allied 130 grade fuel. Again, Fw 190 does not need help under 15000 ft, or even under 20000 ft, it was above 20000 ft when it start loosing the war for Germany in the ETO.
Problem with impeller of the S/C on the BMW 801A/C/D was not size, but inefficiency (a problem compounded by the restrictive internal intakes) - the E and S with newly designed S/C gained 15-20% increase of power on same boost.

No clash with u/c or guns/ammo. Radiators would displace some potential tankage. An aircooled engine had advantages esp re vulnerability and in Jabo role.

Wing radiators of the type we see on Spitfires and Bf 109s are inferior to annular radiators.

P-39 Expert · Jul 1, 2019

tomo pauk said:
Okay, thanks in advance

Hydraulic drive also 'steals' power at lower altitudes (not just due to the slip), adds up to oil cooling requirement, and does nothing above the rated altitude. Fw 190 was already excellent under 20000 ft, it needed a much improved altitude power above 20000 ft once P-47s (and especially Merlin Mustangs) came in knocking. Better spend resources to make a better S/C.
The R-2800-30 was an E series engine, vs. -22 and -34 being C series engine - post war vs. wartime. Apart from internals being modified and improved, it also spinned it's (better? bigger? both?) S/C at up to 10.55 times the crankshaft rotation speed, while the -22 and -34 were doing it at max 9.45 times the crankshaft speed. Faster S/C means better altitude power, that usually means greater speed.

The DB 603E can't help in 1943, it was a rare engine even in 1944. It's good altitude power was not a fruit of having a hydraulic drive, but rather of great displacement, good RPM for that displacement, and improved S/C.

C3 in 1944 was more or less equal to the Allied 130 grade fuel. Again, Fw 190 does not need help under 15000 ft, or even under 20000 ft, it was above 20000 ft when it start loosing the war for Germany in the ETO.
Problem with impeller of the S/C on the BMW 801A/C/D was not size, but inefficiency (a problem compounded by the restrictive internal intakes) - the E and S with newly designed S/C gained 15-20% increase of power on same boost.

Wing radiators of the type we see on Spitfires and Bf 109s are inferior to annular radiators.

Why are wing radiators inferior to annular? Just asking.

tomo pauk · Jul 1, 2019

P-39 Expert said:
Why are wing radiators inferior to annular? Just asking.

As designed on Spitfire and Bf 109, they were draggier than annular radiators. Plus, they add more length or tubes, meaning increase of vulnerable area.

swampyankee · Jul 1, 2019

P-39 Expert said:
Why are wing radiators inferior to annular? Just asking.

That would imply a second question: why are annular radiators better than air-cooled radials? I await a reply with actual data.

P-39 Expert · Jul 1, 2019

Shortround6 said:
Guys, see : http://www.wwiiaircraftperformance.org/P-39/P-39D_41-6722_PHQ-M-19-1325-A.pdf

In level flight at over 360mph (plane hit 368mph) the P-39D could hold 1150hp to 13,800ft.
When climbing at about 190mph it could hold 1150hp to 12,400hp.

Allison rated the engine at 1150hp at 12,000ft no RAM so obviously some RAM was being generated in level flight. At a higher angle of attack, like when climbing, perhaps the canopy did mask the intake some what. Or perhaps the P-40 system was better but obviously picking up 1800ft of altitude shows that the claim of "almost no ram-compression benefit " is false.

Difference in critical altitude just the difference in ram air speed 368mph vs. 190mph? Would seem right.

tomo pauk · Jul 1, 2019

swampyankee said:
That would imply a second question: why are annular radiators better than air-cooled radials? I await a reply with actual data.

If by 'better' you mean 'less draggy', the actual data by Focke Wulf noted halving of cooling drag when a state-of-the-art (w.r.t. to streamlining) BMW 801D was replaced by the Jumo 213A engine (has annular radiator). Fuselage drag was also reduced by 10%. FWIW: table (cooling drag is noted as 'Kuehlung' under 'Widerstnadsenteile' - 'Drag breakdown'; fuselage drag is under 'Rumpf +K.A.', along with interfrence drag and ventilation drag).

Zipper730 · Jul 4, 2019

tomo pauk said:
P-38 as a classic twin, with leading-edge radiators . . . . elongated chord of the wing by 20% as suggested by NACA . . . coolers in the new leading edge

Actually, this is a very good idea. I'm not sure when they first started extending the tail, whether this was before they re-powered the wind-tunnel, but by some point in 1942, they modified a P-38E into the Swordfish model, which had an extended tail-cone for the gondola.

The proposals in early 1942 for the radiators in the leading-edge and a redesigned inboard airfoil, would have almost certainly served to both reduce cooling drag, and maximum dive speeds. I'm curious if they planned to keep the intercoolers in the wing-leading edge.

plus all of late improvements that P-38L had need to be introduced earlier (from better cockpit heating on)

Agreed

GrauGeist · Jul 4, 2019

The "swordfish" airframe was purely for testing and didn't go anywhere - much like the XP-58.

Zipper730 · Jul 4, 2019

GrauGeist said:
The "swordfish" airframe was purely for testing and didn't go anywhere - much like the XP-58.

No, I'm aware of that, but it illustrates an interest in reshaping the gondola. Combined with the NACA report, it's surprised they didn't add 20% wing-chord inboard, add the radiators in the leading-edge, and extend the tailcone

pbehn · Jul 4, 2019

swampyankee said:
That would imply a second question: why are annular radiators better than air-cooled radials? I await a reply with actual data.

I would say wing leading edge radiators were the best set up simply because so many late and post war planes ended up with them.

drgondog · Jul 4, 2019

Zipper730 said:
No, I'm aware of that, but it illustrates an interest in reshaping the gondola. Combined with the NACA report, it's surprised they didn't add 20% wing-chord inboard, add the radiators in the leading-edge, and extend the tailcone

Major re-design and re-tool - perhaps a year's delay in production that War Production Board would never approve.

20% increase in chord combined with reduced wing span would increase both parasite drag and induced drag - would not improve dive characteristics unless the airfoil was changed - both represent another huge delay in production.

Last but not least, the chin radiator did not have that much drag over the E through H design.

Ivan1GFP · Jul 4, 2019

tomo pauk said:
..... Plus, they add more length or tubes, meaning increase of vulnerable area.

Hello Tomo Pauk,
This seems like a pretty minor difference for some potentially great reductions in drag: The Mustang and other aircraft with radiators and oil coolers located very far aft on the fuselage all have longer tubes for oil or coolant but the aft radiator location seems to be the optimal setup. Note that this was done even for the oil cooler on the La-7 which had its oil cooler moved quite a bit further aft than on La-5FN.
The P-38 Lightning also had rather long coolant lines back to its radiators.

drgondog said:
Last but not least, the chin radiator did not have that much drag over the E through H design.

Hello drgondog,
I can't recall the source, but I have seen a mention that at the same cruise power settings, the earlier aircraft were noticeably faster so there was a significant difference in drag in the new intercooler setup. The maximum speed of the later aircraft was much increased because they were able to run higher sustained maximum power settings because of the increased efficiency of these same improved intercoolers.

- Ivan.

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