Most Overrated aircraft of WWII.....? (1 Viewer)

[XBe02Drvr]

The key here to think of is not g-load but lift. Higher g-loads require more lift, more lift results in a higher AoA, all things being equal. This results in a higher velocity over the top of the wing

Nailed it, Zipper! Nice explanation.

 

[drgondog]

A6M Zero. The aircraft had a lot of shortcomings (fragile structure, no self sealing tanks, engine would quit in a nose over maneuver and more.) Once the US airmen figured out how to fight it, it was done.
Nope, except for lack of self sealing tanks.

I'd also like to add the Spitfire. Was a good airplane during the beginning of the war but was overtaken by a lot of other types and was left only with its glorious reputation and nothing more.

Nope. Refresh my memory - how many 'types' outperformed the Spit XIV? Certainly not any in AAF/USN inventory except in range. The P-51H could trade attribute advantages, ditto F8F and Ta 152 and Fw 190D-13 and P-47M.

 

[drgondog]

Martin certainly had plans for two stage R-2800s. XB-27
Martin actually offered 15 different configurations for their proposal that culminated in the contract award for the B-26. The Army chose the single stage R-2800 version with short wings, because that was the configuration that promised the best performance with the engines available at the time. Other configurations had projected speeds in excess of 400 MPH, but required technology that was not yet available in 1939.

The NAA XB-28 with turbosupercharger was contracted in Feb 1940 for the R-2800-27. Pressurized and aerodynamically sound it was as fast as the Mustang I at 25K. It died eventually because there was no mission other than fast recon (p-38 fine), with medium range and 4K bomb load.

 

[drgondog]

Zipper730 said:


The key here to think of is not g-load but lift. Higher g-loads require more lift, more lift results in a higher AoA, all things being equal. This results in a higher velocity over the top of the wing

Higher AoA results in higher CL. The two conditions are not necessarily analogous to higher G loads - only in fast turns, zoom climb or dive pullout. But cruise at high altitude require high AoA with no attendant G increase, near stall on final approach aren't a high G 'thingy'. Transonic dive at 1G result in higher velocity over the wing and a shock wave - but no increase in G until pullout.

 

[Peter Gunn]

Zipper730 said:


The key here to think of is not g-load but lift. Higher g-loads require more lift, more lift results in a higher AoA, all things being equal. This results in a higher velocity over the top of the wing

Higher AoA results in higher CL. The two conditions are not necessarily analogous to higher G loads - only in fast turns, zoom climb or dive pullout. But cruise at high altitude require high AoA with no attendant G increase, near stall on final approach aren't a high G 'thingy'. Transonic dive at 1G result in higher velocity over the wing and a shock wave - but no increase in G until pullout.

Good Lord, I actually understood that!

Oh man, there's either hope for me yet or it's only a brief moment where my two brain cells are actually rubbing together (in which case I shouldn't get used to that).

 

[Zipper730]

Due to the unusually high speeds at which the Supermarine Spitfire could dive, this problem of aileron reversal became apparent when it was wished to increase the lateral maneuverability (rate of roll) by increasing the aileron area. The aircraft had a wing designed originally for an aileron reversal airspeed of 580 mph, and any attempt to increase the aileron area would have resulted in the wing twisting when the larger ailerons were applied at high speed, the aircraft then rolling in the opposite direction to that intended by the pilot. The problem of increasing the rate of roll was temporarily alleviated with the introduction of "clipped" wing tips (to reduce the aerodynamic load on the tip area, allowing larger ailerons to be used) until a new, stiffer wing could be incorporated. This new wing was introduced in the Mk 21 and had a theoretical aileron reversal speed of 825 mph (1,328 km/h).[2]

Wait, I thought the stiffer wing started on the Mark VII, and that was when the plane theoretically could take a speed of 825 mph (if the prop didn't exist, the fuselage was different, and the tail was redesigned). This was aileron reversal only?

Bollocks.

One of the biggest myths out there.

The fact is that Packard redrew the drawings because they had to change them . . . from 1st angle projection . . . to 3rd angle projection

W-w-w-wait... The drawings were reworked simply to mirror and flip them? I thought there was a problem with the British and US inch being like a tiny fraction of an inch off and that's why there were problems with British aircraft using American V-1650's?

Higher AoA results in higher CL.

Higher coefficient of lift sees a greater pressure differential along the top/bottom of the wings, and a higher velocity over the top?

Transonic dive at 1G result in higher velocity over the wing and a shock wave - but no increase in G until pullout.

That adds up.

 

[Zipper730]

P-47 Drop Tanks in ETO:
- July/Aug 1943: used 200 gal ferry tanks (particularly filled). Not a drop tank but could be released in flight, but more often than not, it failed to jettison.
- 31 Aug 1943: 75 gallon tear drop shape, initially designed for P-39. In 1944, used as underwing tank.
- Sept 1943: 108 gal British designed/ manufactured paper tank. Used as wing tanks Apr 1944
- Feb 1944: 150 gal drop tank. Used as under wing tank 22 May 1944
- Feb 1945: 215 gal belly tank

Honestly, I thought that they carried a small center-tank at first, then a pair of wing-tanks, then a pair of wing-tanks, and a paper-tank in the middle.

These P-47 groups had devised a way to pressurize their tanks using air pressure from the airpump that typically bled off into the exhaust, a certain type of thermostat that was scrounged locally and a glass elbow tube all before August '43.

So, they had a kluge available that effectively pressurized them?

Though I remember the tanks could produce a ferry range of 1800 miles, it was also only at 10000-14000 feet at a relatively low-speeds: How far could those tanks carry the plane if they were doing around at tactical speeds at 25000-30000?

Battle over Germany, January, 1944

P-51B, P-47PreD-25, F4U-1, P-38J, Escort Ability vs. Me-109G and Fw-190A-8
. . . .
I wanted to try to come grasp how these four aircraft would perform in the escort role over Germany against their German opponent. The F4U was thrown in because it was brought up as an aircraft that should have been built instead of the P-47 (and I think the P-51, too).

I never knew that about the F4U-1

First I wanted to define the requirements of an escort fighter for supporting daylight bombing of Berlin by B-17s and B-24s. This is what I determined was needed.

1. Range to fly to Berlin and back
2. Endurance to allow a meaningful combat time under enemy attack.
3. Equal-to or better capability of engaging enemy aircraft in combat at or above 20,000 ft.

That all adds up

The methodology I used to compare these planes were, 1) determine total internal and external fuel available each aircraft, 2) calculate fuel required to transit to target (approx. 600 miles) at 25,000 ft

I'd say that might be on the bottom end of the effective altitude: It'd cover the B-24's without much difficulty, but the B-17's typically flew around 22500'-28000' and, it was generally best for escorts to fly 2000'-3000' to 5000' above that.

3) calculate fuel required to return to base (I used ingress fuel since I am lazy and probably didn't have this data. Still should be okay for comparisons)

I assume fuel burn would be somewhat lower on the way out. You have less airplane to move through the sky, and that's gotta do something. That said, I don't know how to calculate for that either, so...

4) calculate fuel available for combat, 5) calculate combat time at Normal Rated Power (NRP), 6) compare performance at 20,000, 25,000, and 30,000 ft. Since the data available was not all compatible between aircraft (it never is), some alchemy was required to generate fuel consumption at 25,000 ft. It all seems to pass the smell test.

That works out.

Flight profile goes directly to Germany, optimum cruise, engage defenders, fly directly home. Weaving over slower bombers is not calculated but obviously would reduce time in combat.

S-weaving wouldn't be too hard to calculate: Just divide the fighter's tactical speed by the bomber's speed.

That said: The full range you'd compute would largely be unnecessary, as they generally used a relay system whereby multiple sets of fighters would head out, rendezvous with the bombers; then return home once relieved by the next set of fighters.

Looking at the figures you've computed

1. P-38J: I'd almost swear that you'd have to burn down a small amount of fuel in the wings before switching to drop-tanks (I'm not sure if it was based on C/G or g-load limits)
2. F4U-1: with the need to expend drop-tanks at the start of combat means you'd have to hold onto them with the German coast only 90 miles or so off the coast of the UK (that, or you'd land in occupied territory).
3. P-47: It had a lot more range than I'd have expected, even with drop-tanks: That said, the P-38 and P-51 were better candidates for escort.

Additionally: I'd almost swear aircraft in those days had requirements for loitering/diverting, as well as some fuel burned during run-up and taxi (however little).

Performance at 20k ft. (B-24 Altitude)

The F4U-1's climb rate isn't that good at 20000', from what I was reading, 1940-2300 fpm seemed to be the maximum you'd get at that altitude. The speeds seem close enough.

The high altitude mechanical issues were not 'solved' until the Intercooler/turbo re-design, electrical cockpit heating provided by adding a generator.

From my understanding, however little that might be: The P-38J did have a redesigned intercooler over the earlier designs, right? I also didn't know that the powered ailerons and dive-recovery flaps weren't routinely in operation until after D-Day. From what I remember, the P-38J-20/25 were in possession of both by March of 1944...

Not in so many words, but yes. Go Deep, incite reaction - kill 'em in the air and pursue all the way to the deck.

What Doolittle reacted to was one of his commanders stating that the role of the fighter was to 'protect' whereas Doolittle believed the role of fighter aviation was to destroy - and he had just received intelligence reports that LW was building strength in alarming numbers (January, 1944) and posed a serious threat to OVERLORD.

So this is when policy went from defense to offense?

 

[pbehn]

Wait, I thought the stiffer wing started on the Mark VII, and that was when the plane theoretically could take a speed of 825 mph (if the prop didn't exist, the fuselage was different, and the tail was redesigned). This was aileron reversal only?

.

It is a wiki article, there were quite a few mods to strengthen the Spitfires wing, but as far as aileron reversal is concerned the speed is theoretical, problems occur long before that speed is reached.

 

[Zipper730]

It is a wiki article, there were quite a few mods to strengthen the Spitfires wing, but as far as aileron reversal is concerned the speed is theoretical, problems occur long before that speed is reached.

That I'm aware of, as I said: I was under the impression that the wings could maintain adequate airflow over them up to 800, as absurd as that sounded. That said, I know the fuselage and tail couldn't withstand it.

 

[pbehn]

That I'm aware of, as I said: I was under the impression that the wings could maintain adequate airflow over them up to 800, as absurd as that sounded. That said, I know the fuselage and tail couldn't withstand it.

It isn't a question of airflow but forces and rigidity. If you have an aileron reversal speed of 850 MPH then you don't have any problems at 500.

 

[XBe02Drvr]

I was under the impression that the wings could maintain adequate airflow over them up to 800

If you're doing 800, you've got a lot more to worry about than aileron reversal. How about shock waves, center of pressure shift, and mach tuck for starters? Maybe some control surface flutter as well?

 

[pbehn]

If you're doing 800, you've got a lot more to worry about than aileron reversal. How about shock waves, center of pressure shift, and mach tuck for starters? Maybe some control surface flutter as well?

I think that if you are doing 800MPH in a Spitfire you have lost most control surfaces a while ago.

 

[XBe02Drvr]

I think that if you are doing 800MPH in a Spitfire you have lost most control surfaces a while ago.

Roger that! ("Roger" in the R/T sense, not the piratical or Shakespearean)

 

[Reluctant Poster]

Packard was a fairly major player in the aero-engine business for a few years after WW1, but was out of the aircraft engine business by 1940. I suspect that its management felt that the market for aircraft engines didn't promise sufficient ROI.

The US engine designation system is based on two very broad parameters: displacement and general configuration. It's not designed to cause confusion, but the Navy and Army's aviation services were not really concerned with the engines' internal details. Engines with the same configuration, displacement, and technology level will be similar in weight, installed volume, and performance, the parameters that matter to customers.

The Merlin was two generations after the Packard V-1650; the displacement was a coincidence.

According to Development of Aircraft Engines by Schlaifer, Packard dropped out of the gasoline aircraft engine business when the US Army cut their funding in 1928.
Schlaifer also notes "Besides the two Curtiss engines there were the 1500- and 2500-cu. in. 12 cylinder engines designed and built by the Packard Motor . Although they were by no means the equal of the Curtiss engines in general excellence, and showed some very serious faults in operation, still these two engines were very light for their power, and both the Army and Navy had great hopes for their ultimate success."
Packard did continue to attempt to develop a diesel aircraft engine.

Strangely enough the British thought the the ancient Liberty would make an excellent tank engine (probably because Walter Christie used it in his radical tank designs). Nuffield obtained a licence and put it back into production. Fortunately for the Allied cause Rolls Royce developed the Meteor to place it. The Soviets also used a Liberty copy in their early BT tanks

 

[Admiral Beez]

Zero

Agreed, the glass jaw of fighter planes. Can duck and punch better than most, but hit it once and it's done.

 

[Admiral Beez]

To me the most overrated plane. far and away, is the Me 262.

Sure it was the first jet into regular squadron operations, but the effect it had was nothing comarped with the resources expended to develop and deploy it.

The B-17 bomber stream was the SAME whether or not the Me 262 was there, and Me 109s produced in lieu of the 262s would have done more damage to the bombers, if only because so many more Me 109s could have been built using the resources dedicated to Me 262 development and deployment.

It's the same with much of Germany's obsession with Wunderwaffe. Why build Bismarck and Tirpitz to face an enemy with a clear superiority in battleships when those 82,000 tons and 4,000 men could have gone towards 3,200 Panzer IV tanks or 800 U-Boats to attack from Germany's position of advantage?

Skip the Me 262 program, focus on what you can build quickly. But really, if you can't knock the USSR out of thr war before the end of 1942 the war is lost regardless.

 

[Shortround6]

Why build Bismarck and Tirpitz to face an enemy with a clear superiority in battleships when those 82,000 tons and 4,000 men could have gone towards 3,200 Panzer IV tanks or 800 U-Boats to attack from Germany's position of advantage?

In part to tie up an equal amount (at worst) of British ships and men and several times the Germans investment at best.

No Bismarck and Tirpitz?
British don't build 1-2 KGVs, don't plan the Lion class and/or don't build the Vanguard, instead they build 70-100,000 tons of escorts (Hunts/Black Swans, etc) and since the British could out build the Germans and Subs are harder to build than surface ships this doesn't look good for the U-boat strategy.

Similar arguments could be made about the tank production. Tirpitz especially sucked up an inordinate amount of effort from the allies (mostly Britain) with not only the long history of attacks but even such simple stuff as a battleship escort for many Russia bound convoys sucking up thousands of tons of fuel oil per trip.

see: Fleet in being - Wikipedia
for the general concept.

 

[pbehn]

In part to tie up an equal amount (at worst) of British ships and men and several times the Germans investment at best.

No Bismarck and Tirpitz?
British don't build 1-2 KGVs, don't plan the Lion class and/or don't build the Vanguard, instead they build 70-100,000 tons of escorts (Hunts/Black Swans, etc) and since the British could out build the Germans and Subs are harder to build than surface ships this doesn't look good for the U-boat strategy.

Similar arguments could be made about the tank production. Tirpitz especially sucked up an inordinate amount of effort from the allies (mostly Britain) with not only the long history of attacks but even such simple stuff as a battleship escort for many Russia bound convoys sucking up thousands of tons of fuel oil per trip.

see: Fleet in being - Wikipedia
for the general concept.

The Bismarck putting to sea was a headache for the RN, the Tirpitz not putting to sea was an even bigger one.

 

[Zipper730]

It isn't a question of airflow but forces and rigidity. If you have an aileron reversal speed of 850 MPH then you don't have any problems at 500.

That theoretical speed was like 800 TAS right?

If you're doing 800, you've got a lot more to worry about than aileron reversal. How about shock waves, center of pressure shift, and mach tuck for starters?

Mach tuck effects were the thing that had me puzzled too. I figured "good to 800" meant airflow would be good enough to avoid excessive flow separation (some degree is invariable).

I remember talking to a person online awhile back (first we talked on Yahoo IM, then through e-mail and FB, now just e-mail) who sort of toyed with an art-project of a plane with the latest Spitfire Wings (Mk.21), with a redesigned fuselage, an early axial-flow jet-engine (F.2/4 if I recall right), and an all-moving tail. It was half concept and half gag from two people with a warped sense of humor.

While it didn't get very far (in terms of drawings, or art-work),it turns out there's a lot of variables that contribute to the high dive-speed of the Spitfire

• The thin wing: It was one of the thinnest wings used in an operational piston driven aircraft. If I recall the wing was around 13.9% at the root, around 9.4% at the tip.
• The thin fuselage: As I understand it, by being very skinny, it would part the air less abruptly to either side, and that would contribute to less energy drained out of the flow (generally resulting in some degree, however small, of turbulence). This would make the airflow more effective over the tail.
• The large fillets: Helped blend the airflow over the wing/fuselage junction, and reduced interference effects. Might have contributed superior airflow over the tail surfaces.
• Oversized tail-surfaces: The original proposal, as I understand it, had smaller vertical and horizontal surfaces. This is because the airflow over the fuselage would have resulted in good effectiveness. The air-ministry wanted them to enlarge them, but seemed open to haggle a bit, and an arrangement was made somewhere between Supermarine's initial proposal and what the air-ministry initially wanted.

The elliptical wing might have made some contribution, this was a common made by Leidnicer, though I'm not sure about that. The spitfire had some variables that worked against it, admittedly, such as...

• The canopy angle was quite steep
• The bullet proof glass pane was outside the canopy contours (simple adaptation, but a drag producer).
• It had a mirror located outside the canopy that, while it provided superior situational awareness to the rear, it did contribute some drag (interestingly, some P-51's would adopt this later in the war).

I think that if you are doing 800MPH in a Spitfire you have lost most control surfaces a while ago.

Yeah, you'd need an entire reworking of the internal structure.

 

[wuzak]

That theoretical speed was like 800 TAS right?

Supersonic? Really?