Improve That Design: How Aircraft Could Have Been Made Better (1 Viewer)

[Shortround6]

Why not a turbocharged F4F-3? No magical time line, just using what we already have. Bugs won't get worked out of turbocharger until early 1942, but plane should perform awesome. Wish I could calculate increase in climb.

Original 2 speed 2 stage P&W R-1830-76:
1200 hp for takeoff
1100 hp from SL-2500 feet
1050 hp from 4800-11000 feet
1000 hp from 12200-19000 feet

with a P&W R-1830-47 with a turbocharger (same engine as the P43 Lancer)
1200 hp from SL-25000 feet, still producing 1,000 hp at 30,000 feet.

SL speed increases from 278 to 286
Speed at 5500 goes from 295 to 308
Speed at 13000 goes from 313 to 332
Speed at 19000 goes from 330 to 350
Speed at 22000 goes from 326 to 351

The F4F-3 speed numbers above included 150 pounds of armor and a self sealing fuel tank.

P&W 1830 or Wright 1820 uses lowest geared supercharger so less power to turn supercharger. Turbocharger is only used as air begins to thin out so at low altitude, SL-2500 or so, turbocharger isn't even being used, flap to intercooler remains completely closed. As F4F-3 gains altitude, flap to intercooler is only opened enough as needed, cutting down on drag. Engine needs less power to run supercharger allowing more power to turn prop, meaning less boost from turbocharger, meaning less heat, meaning less use of intercooler, meaning less drag. (At least that is the way it works in my head)

Ir works just fine until you get into the high teens at which point the existing intercoolers are too small.
We have been over this in some thread in just the last few weeks.
On the F4F all the supercharger plumbing/ducts are forward of the wheel wells.

the landing gear works like this.

From VC-27 "The Saints" - Aircraft
On the F4F the intercoolers are just forward of the wheel wells and in fact the used cooling air form the intercoolers is dumped into the wheel wells to find its way out of the plane.

You have the fuel tanks in the center of the plane under the cockpit and behind it.


The P-43 landing gear was in the wing and when retracted left space for the exhaust pipe duct in the bottom of the fuselage. The P-43 also used a fuel tank in each wing which left the fuselage clear.

In the low 20,000ft range you need bigger intercoolers because you are trying to compress the air more (more heat) but the ambient air is thinner (less pounds per cubic ft)) so you need a larger airflow to even cool the same amount of combustion air.

Maybe you can do it. It just isn't going to be simple. TANSTAAFL

 

[pinsog]

Ir works just fine until you get into the high teens at which point the existing intercoolers are too small.
We have been over this in some thread in just the last few weeks.
On the F4F all the supercharger plumbing/ducts are forward of the wheel wells.

the landing gear works like this.
View attachment 540418View attachment 540419
View attachment 540420 From VC-27 "The Saints" - Aircraft
On the F4F the intercoolers are just forward of the wheel wells and in fact the used cooling air form the intercoolers is dumped into the wheel wells to find its way out of the plane.

You have the fuel tanks in the center of the plane under the cockpit and behind it.


The P-43 landing gear was in the wing and when retracted left space for the exhaust pipe duct in the bottom of the fuselage. The P-43 also used a fuel tank in each wing which left the fuselage clear.

In the low 20,000ft range you need bigger intercoolers because you are trying to compress the air more (more heat) but the ambient air is thinner (less pounds per cubic ft)) so you need a larger airflow to even cool the same amount of combustion air.

Maybe you can do it. It just isn't going to be simple. TANSTAAFL

They would have to do it early on. Looks like there is room to slide a couple of (what diameter exhaust pipe? What diameter pipe from turbo to engine? 5 inch? 6 inch?) pipes through there. I don't think the fuel tank would be an issue, after the landing gear the 2 pipes just run along the floor with the bottom of the tank adjusted to let them pass through (easy if done from the beginning of course)

Agree that at upper altitude you would need a larger intercooler, (move intercooler to back near turbo?) but you would not need to use the larger capacity of the larger intercooler until you get to that altitude so you wouldn't be increasing drag, you only open the flap to the intercooler enough to cool the air at the altitude you are at. At low altitude the turbo is not doing anything so the intercooler flap would be completely closed, correct?

How much HP does high gear on a P&W 1830 use? if you are turning a lower gear on the supercharger, you aren't losing that hp to turn the higher gear because of the turbocharger, so the engine is either working less to put the same hp to the prop, or working the same to put more hp to the prop, correct?

 

[Shortround6]

Actual pictures are better than drawings

F4F through the wheel wells.

Grumman F4F-3 Wildcat Museum of Naval Aviation Photo Walk Around Image 08

 

[pinsog]

I would move that intercooler to the back near the turbo and make it larger.

Like I said, they would need to tackle this early on. Love to see a head on pic with the engine removed. I think the landing gear would be the biggest headache. I don't think the fuel tank would be a big issue. Just adjust the bottom of the tank with the pipes installed.

 

[pinsog]

 

[pinsog]

If you have room for windows to look out the bottom of the plane, you might have room for some plumbing to and from a turbocharger. Move the intercoolers to the back by the turbo and then see if you can slip the two pipes from the collector ring through the landing gear. The landing gear looks like it will be a pain. Much easier to do this BEFORE you build the entire plane!

 

[Shortround6]

One problem is the lower photo in post #145 is of an FM-2 which used a 9 cylinder wright R-1820 engine with a single stage supercharger, Firewall/engine compartment details are somewhat off from a F4F-3/4 like the first photo.

Please look at the link, the photos are way too big to post here. There are a number of other things either sticking back into the landing gear bay or routed through it.

Any piping (exhaust or intake air or???) is going have to use radiused bends. Too sharp a bend and you you loose pressure, either pressure in the exhaust or pressure from the turbo to the carb on the engine supercharger.

As far as figuring power goes, General motors put out a booklet during WW II comparing 7 different supercharger systems.

It may be available for download? They used a hypothetical 1000hp engine to illustrate the differences.
GM owned Allison, a coincidence???

In any case turbo superchargers are not "free" HP. If you could supply the theoretical 1000hp engine with sea level air pressure to the carb at 20,000ft the engine would amke about 1080hp due to the reduced back pressure on the exhaust pipes/ports.
You do free up more than 80 hp by eliminating the 2nd gear driven supercharger.

Part of the reason that the P-43 made 1200hp at the higher altitudes is that it was rated at 2700rpm while the 2 stage engine, except for take-off, is rated at 2550rpm. I have never found the reason for this. A pilots manual even has a section that states the two stage engine could use 2800rpm for emergency take-off (shortened the take off run by 60 or 80 ft?) but permission to use that RPM for emergency climb had been rescinded.

Another problem is the propeller. Wildcats used a 9'9" or 10ft prop. the P-43 used an 11ft prop. You can't use a prop designed to transmit 900hp or so at altitude to transmit 1200hp.
The problem comes in when the Wildcat is flying level on the runway or deck. In "static" conditions the Wildcat has 8.75in of clearance for the prop. The 11ft P-43 prop would cut that to 2.75 in and the Wildcat had some of the "spongest" landing gear going. Deflection from the static line upwards could 5 1/4 inches. Overall oleo defection was 12 1/2 inches.
Perhaps you could fit an in between prop and risk the prop strikes (nobody was using broad cord baldes in 1941/42) but your climb and speed might be a bit off the estimates with a less efficient propeller.
If you try computing speeds using the FM-2 it does get some help from exhaust thrust.

 

[pinsog]

Good information Shortround. If they had done this, obviously the intercoolers would be out of the way and they would have to move some of the things around that are right now, bolted to the landing gear mounts, and also agree that the fewer bends the better which is why they would need to do this early on. I also know that there were bugs in the turbocharger controls until early 1942.

On the prop, as you know, it would be a matter of them choosing the best prop that covers the most area they expect to be fighting in with the best average of climb, speed at the altitude they expect to fight at etc with no prop being best at everything. Obviously for a carrier based fighter, 25,000 feet would probably not be very high on the priority list, but top speed from SL-20,000 and climb rate would, i imagine, be what they focus on.

They would have to test several props to see what was best. But, prop doesn't mean much if you don't have the power to turn it.

Just curious, could you get away with the stock intercoolers if you stayed between SL and 20,000 feet? Again, my thinking is, your running the lowest geared supercharger so you don't have the parasitic loss of turning high gear on the 2 speed, the turbocharger then making up the difference. (I know turbochargers aren't totally free power, but they cost a lot less power than spinning a supercharger)

 

[tomo pauk]

To circumvent a bit powerplant-related issues of the F4F - how about Grumman (or anyone capable) makes a fighter where the widest part of fuselage is at engine cylinders, not at half of length? Couple that with a smaller wing (say, 220 sq ft?) that has Fowler flaps installed, and both drag and weight should be a bit trimmed down, for better speed & climb?

Similar for the Japanese - Zero with wing of 200 sq ft (instead of 240 sq ft) with Fowler flaps. Thus even with Sakae it can prove a better match for improved Allied aircraft of late 1942 on. With shorter wing it should also roll better.

 

[pinsog]

To circumvent a bit powerplant-related issues of the F4F - how about Grumman (or anyone capable) makes a fighter where the widest part of fuselage is at engine cylinders, not at half of length? Couple that with a smaller wing (say, 220 sq ft?) that has Fowler flaps installed, and both drag and weight should be a bit trimmed down, for better speed & climb?

Similar for the Japanese - Zero with wing of 200 sq ft (instead of 240 sq ft) with Fowler flaps. Thus even with Sakae it can prove a better match for improved Allied aircraft of late 1942 on. With shorter wing it should also roll better.

Hmmmm. Like maybe a P43 with a skinnier body? (And fuel tanks that don't leak...)

A P43 with the body of a Skyrocket and fuel tanks that don't leak?

I don't think the turbocharged F4F-3 would be difficult to do as long as it is done early in the design. Retrofitting in 1941 after production was started will obviously be much more difficult

Edit: I can read Shortrounds mind right now "if you have a skinny little fuselage and a tiny wing, where does the fuel go? Where do weapons and ammo go? What will the range be? What will climb rate be with a small wing?
(Did I guess right Shortround? Hope so because it's what im thinking as well)

 

[tomo pauk]

Hmmmm. Like maybe a P43 with a skinnier body? (And fuel tanks that don't leak...)

A P43 with the body of a Skyrocket and fuel tanks that don't leak?

I was thinking about something like P-36.

I don't think the turbocharged F4F-3 would be difficult to do as long as it is done early in the design. Retrofitting in 1941 after production was started will obviously be much more difficult

Yes, if the aircraft was designed for turbo from the get-go, then turbo might be a workable solution. The historical F4F might've had one of better radials of 1941, but it was a portly aircraft, with a big wing - meaning a lot of drag and weight.

 

[Shortround6]

To circumvent a bit powerplant-related issues of the F4F - how about Grumman (or anyone capable) makes a fighter where the widest part of fuselage is at engine cylinders, not at half of length? Couple that with a smaller wing (say, 220 sq ft?) that has Fowler flaps installed, and both drag and weight should be a bit trimmed down, for better speed & climb?

Similar for the Japanese - Zero with wing of 200 sq ft (instead of 240 sq ft) with Fowler flaps. Thus even with Sakae it can prove a better match for improved Allied aircraft of late 1942 on. With shorter wing it should also roll better.

Granted they used different wings but the P-36/Hawk 75 had it's greatest fuselage diameter at the engine cowl. You can check performance at the lower altitudes where power was similar to see any difference. While the "fat/wide" fuselage F4F may have been at a disadvantage the "fat/tall" F4F gave bit better view for landing and allowed for a greater angle for deflection shooting over the nose. F4F was also trying to hide the main wheels in the fuselage. Make the fuselage too skinny and the wheels are not going to fit the circumference of the fuselage as well.

Be careful about clipping wings. The aspect ratio affected the efficiency of the wing. A high aspect ratio wing actually gets more "lift" per sq ft of area or perhaps more lift per unit of drag. Perhaps not important for a short range fighter but rather important for a long range fighter like the Zero. Forcing it to cruise faster to get the same "lift" (especially with the smaller wing) may cut the range. Please look at the Spitfire for a good illustration of this. The actual changes to square footage of area were tiny. The extended wing version was 2.6 % bigger and while it did hurt a few aspects of the performance, especially at low altitudes, it helped with others at high altitude. the Clipped wing version was 95.4% as big as the standard wing.
The aspect ratio was a much bigger change.

roll response seems to have something to do with how far the wing extended beyond the end of the Ailerons. In general planes with ailerons that were 'recessed" away from the tips seem to have worse response than ones with ailerons going to the tip (or having the tip cut back to the end of the aileron.) A short wing does not automatically give good roll response unless the aileron is sized in proportion to the wing and has enough deflection (failing of the early Mustangs?) A short wing only has so much trailing edge and you have a conflict going with either large enough flaps to get the landing speed you want or large enough ailerons to get the roll response you want. Drooping ailerons can help but are an added complication.

 

[pinsog]

I like the P36 Tomo. I think it would have gained a lot of speed just from cleaning up the wing by redesigning the landing gear and adding at least a 2 speed engine. But we've done so many "better P36" and when we add a 2 stage engine and X many 50's with ammo it starts getting pretty heavy.

At least with an F4F-3 we have armor, self sealing tanks, 4 50's, 450 rpg, good amount of fuel and a heavier 2 stage engine. All we need to do is exchange the 2 speed 2 stage engine with a turbo and we get 1200 hp from SL-25000 feet (they would have to test it and pick the prop that works best for the job). And add drop tanks.

If you check my numbers on increased performance I think it would be a winner.

 

[Shortround6]

The F4F was also designed to meet pre war limits on landing and take-off speeds/distances on Carriers. relax those standards even 10% and there is a lot you can do. If the standards are not relaxed/waived then you are stuck with the large wing.

 

[pinsog]

Tomo, if you are specifically talking about a carrier fighter, I don't think you can reduce the wing size. Between landing speed, controllability, and lifting off a carrier with a full load of fuel and drop tanks I just don't think you can go any smaller on the wing

 

[Kevin J]

To circumvent a bit powerplant-related issues of the F4F - how about Grumman (or anyone capable) makes a fighter where the widest part of fuselage is at engine cylinders, not at half of length? Couple that with a smaller wing (say, 220 sq ft?) that has Fowler flaps installed, and both drag and weight should be a bit trimmed down, for better speed & climb?

Similar for the Japanese - Zero with wing of 200 sq ft (instead of 240 sq ft) with Fowler flaps. Thus even with Sakae it can prove a better match for improved Allied aircraft of late 1942 on. With shorter wing it should also roll better.

You mean Airacobra sized wing so although it goes faster, its higher stalling speed means that its altitude performance is worse.

 

[tomo pauk]

Tomo, if you are specifically talking about a carrier fighter, I don't think you can reduce the wing size. Between landing speed, controllability, and lifting off a carrier with a full load of fuel and drop tanks I just don't think you can go any smaller on the wing

The F4F was also designed to meet pre war limits on landing and take-off speeds/distances on Carriers. relax those standards even 10% and there is a lot you can do. If the standards are not relaxed/waived then you are stuck with the large wing.

You mean Airacobra sized wing so although it goes faster, its higher stalling speed means that its altitude performance is worse.

I've specified Fowler flaps for both types.

BTW, regarding the post #156 here: Airacobra's altitude performance was a result of the V-1710 making a sub-par power at higher altitudes in 1941-late 1942, combined with customer's requirement that it must carry 900 lbs worth of guns & ammo.

 

[tomo pauk]

...
Well, the Do 215 was rated at just about 500kph. Since the bombs are carried inside it doesn't take the performance hit that strapping bombs to the bottom of the 110 would cause so the actual attack speeds (30 minute rating?) would be a lot closer. Get rid of the "bug-eye" nose and put on something like the night fighter nose. Use DB 601N or E engines (mainly to get the altitude up higher than the DB601A and DB601Aa. You also have a more range than the 110. Possibility of trading bomb bay space for more fuel. Just do something about the idiotic gun array at the rear of the canopy.

It will never equal the Mosquito but since you could have them almost 2 years before the Mosquito shows up in any numbers it doesn't have to be quite as good.
The JU-88 was never going to equal the Mosquito either as by the time you get to the A-4 (very late 1940/early 41) you have plane weighing thousands of pounds more.

To return for a moment to think about the Do 215 and alternatives. If we agree that dive bombing is not required, and that 50 kg bombs are okay, the Ju 88A-1/A-4/A-5 can lose dive brakes and bomb racks - that will give another 15-20 km/h? The A-1's internal bomb racks were carrying 18 x 50 kg bombs in front chamber, plus 10 bombs in aft chamber - that is 28 vs. possible 20 on the Do17/215.

 

[Shortround6]

To return for a moment to think about the Do 215 and alternatives. If we agree that dive bombing is not required, and that 50 kg bombs are okay, the Ju 88A-1/A-4/A-5 can lose dive brakes and bomb racks - that will give another 15-20 km/h? The A-1's internal bomb racks were carrying 18 x 50 kg bombs in front chamber, plus 10 bombs in aft chamber - that is 28 vs. possible 20 on the Do17/215.

True but the Ju-88 A-4 used engines that had 1340hp for take-off and gave 1060hp at 17,000ft (?? old source, open to correction)
while the Do-215 used DB 601Aa engines that gave 1175ps (1 minute) for take off and 1100ps at 12,210ft. (5 minute).
The Do-215 was being phased out before the Ju-99A-4 really entered production due to delays in the Jumo 211J engine.
The Ju-88 carried 369 Imp gallons of fuel without resorting to bomb bay tanks and the Do-215 carried 341 imp gallons in the wing root tanks without resorting to bombay tanks.

AN "improved" DO 215 might well operate at somewhat higher gross weights than the Do-215 (7000-8500kg) and put a bit more fuel in the wings?

The Ju-88A-4 was an "improved" Ju-88A-1 with a bigger. stronger wing, more powerful engines, beefed up landing gear and a few other changes that that raised the empty equipped weight by over 2000kg..

Trying to modify the Do-215 to equal the Ju-88A-4 in load carrying ability is a losing game. You need a whole new airplane. But using the Do-215 as a starting point for a high speed (330mph ?) bomber that could carry four 250kg bombs at a high cruising speed might have promise.
Given the chronic shortage of DB engines it is not realistic and that engine shortage is the main stumbling block.

 

[Shortround6]

Trying to make a better carrier plane than the F4F is going to take a bit of doing.
Using the stock flaps reduces the take-off run by about 25%. At 7921lbs it is supposed to take just under 700ft to take off in zero wind using the flaps.
Stalling speed with 4 guns clean was supposed to be 69 knots power off, Power on reduced that to 63kts. with flaps and gear down the stalling speed dropped about 9 knots or more.
Flaps had one setting (43 degrees)and were vacuum operated, as speed built up over 130knots the flaps "blew up" until about 10 degrees meaning the pilot could pretty much ignore them while taking off (a good thing as he had to crank the landing gear up by hand.)
Using a small wing and trick flaps may not actually get you much.

I would also note that the figures for the P-43 at 6913lbs (about 1000lbs lighter) call for a ground run of 1070ft using 15 degrees of flap.
P-43 at weight has no armor, no self sealing tanks. 145 US gallons and 250.6 pounds of armament ( four .50s with no ammo weigh around 300lbs)
P-36C needed 600ft with 30 degrees of flap at a weight of 5800lbs (another 1000lbs lighter) and held 105 us gallons, 292lbs of guns and ammo, no armor, no self sealing tanks. and had trouble with the wing skin wrinkling or buckling in the area of the landing gear attachments.