The B-24 Goes to War

[earl1937]

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At low AoA a laminar flow wing profile has a better lift/drag ratio than a more conventional WWII wing profile, like that on the La7. This is because of the "brag bucket" effect of the laminar flow wing. However as AoA increases the laminar flow wing quickly starts to fall short of a more conventional wing.


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If the B-24 is able to climb while keeping the AoA within the wing's "drag bucket" it will climb more efficient than with a conventional wing. However the margins are tight; if the pilot lose too much speed and have to increase AoA to keep altitude the laminar flow wing will lose effectiveness abruptly.

As usual from you sir a good post, but I think everyone is forgetting, the best "rate" of climb is dictated by the weight and a number of other things. If all paramour's are equal, load, temp, the B-24, based on performance in this game, will not only climb faster than a 17, its ground speed is higher. The easiest way to compute which wing if more proficient, compute V1, VR, and height above ground, when V2 is reached, based on both weighting 62,000 lbs, 29.92 BP, and 59 degrees F, taking off on a paved runway of 7,000 feet with zero runway gradient.
When putting in the head wind speed of just 10 Knots down the runway, the "Hersey Bar" wing of the 17 will allow it to get airborne quicker, but the 24 with catch and pass it in altitude before reaching  1,000 feet AGL. Those are the real world computations, based on pilot reports of the test pilots of both aircraft.

[GScholz]

It's ground speed is higher because it has a higher wing loading than the B-17, and it needs more speed to climb at a lower AoA where its wing is more efficient. This is typical for all high wing loading aircraft. When that Davis wing gets into the sweet spot "drag bucket" it is much more efficient than the B-17 despite needing more air speed (and thus more parasitic drag) to get the AoA low enough.

 

[earl1937]

It's ground speed is higher because it has a higher wing loading than the B-17, and it needs more speed to climb at a lower AoA where its wing is more efficient. This is typical for all high wing loading aircraft. When that Davis wing gets into the sweet spot "drag bucket" it is much more efficient than the B-17 despite needing more air speed (and thus more parasitic drag) to get the AoA low enough.

 

One once, I think you and I disagree about something! Since that was the day before AOA indicators, we don't really have any good tests to really go by, we are just going on engineering assumptions! (Your graphs not withstanding sir). I believe that, at what ever altitude under 5,000 feet, both aircraft air 100 KIAS, then full power added to both aircraft at the same time, the B-24 will arrive at a stable 900 FPM climb than the 17 and will have cover more distance. What do you think? Just remember, the engineers said the Titanic wouldn't sink either!

[Valkyrie]

Your also talking about vastly different induction systems and power plants. The B-17 was upgraded several time during the war going from 1830plus to 1845 cubic inches, where the B-24 was constant at 1820. Two entirely different designs. The B-24 was the vastly more efficient design, and 7 years ahead of the B-17. As far as range and weight carried the B-24 blows the 17 away. But by my grandfathers estimation much more difficult to fly.

[colmbo]

Your also talking about vastly different induction systems and power plants. The B-17 was upgraded several time during the war going from 1830plus to 1845 cubic inches, where the B-24 was constant at 1820. Two entirely different designs. The B-24 was the vastly more efficient design, and 7 years ahead of the B-17. As far as range and weight carried the B-24 blows the 17 away. But by my grandfathers estimation much more difficult to fly.

You seem to have gotten some bad info regarding the power plants.

The B-24 was equipped with the Pratt and Whitney 1830 (1829 cubic inches), 14 cylinder engine. On the production aircraft this engine was putting out 1200 HP.

The B-17 was equipped with the Wright 1820 (1823 cubic inches), 9 cylinder engine.  On the F and G series Fortress this engine was putting out 1200 HP.  The prototype B-17 flew with an 750HP version of the 1820.  The Y1B-17A used an 850HP version, the production airplanes at first had 1000HP version but by the E model they had settled on a 1200HP version.  The displacement of the engine never changed.  Post war versions of the 1820 put out as much as 1350HP.

Both engines were turbo supercharged having a built in supercharger plus turbochargers (both airplanes used the same model of turbocharger).

In my experience the Wright was the more reliable engine (based on inflight failures and number of engines/cylinders I helped change).

[earl1937]

You seem to have gotten some bad info regarding the power plants.

The B-24 was equipped with the Pratt and Whitney 1830 (1829 cubic inches), 14 cylinder engine. On the production aircraft this engine was putting out 1200 HP.

The B-17 was equipped with the Wright 1820 (1823 cubic inches), 9 cylinder engine.  On the F and G series Fortress this engine was putting out 1200 HP.  The prototype B-17 flew with an 750HP version of the 1820.  The Y1B-17A used an 850HP version, the production airplanes at first had 1000HP version but by the E model they had settled on a 1200HP version.  The displacement of the engine never changed.  Post war versions of the 1820 put out as much as 1350HP.

Both engines were turbo supercharged having a built in supercharger plus turbochargers (both airplanes used the same model of turbocharger).

In my experience the Wright was the more reliable engine (based on inflight failures and number of engines/cylinders I helped change).

I didn't want to burst his bubble! I wonder what improvements in performace both aircraft would have had with the R-2000 installed. I don't think it was developed before production for both aircraft was poured in "concrete" so to speak! The R-2000 was an enlarged version of the Pratt & Whitney R-1830 Twin Wasp, with focus on reducing the manufacturing costs and fuel requirements. The bore was increased to 5.75 inch, while it still retained the 5.5 inch stroke. This brought displacement up to 2,000 in. There were a number of detail changes from the R-1830, such as front-mounted instead of rear-mounted magnetos, plain bearings for the crankshaft rather than roller bearings, and 87 octane fuel (specified because there were fears wartime supplies of 100 octane might fall short, but those fears were groundless). The R-2000 produced 1,300 hp @ 2,700 rpm with 87 octane, 1,350 hp with 100 octane and 1,450 hp @ 2,800 rpm with 100/130-grade fuel.(Figures are from P&W web site)
There really wasn't much weight gain because it was the same basic size engine, but it was developed for the C-54, I think in the early war years like 42 or 43.

[colmbo]

I wonder what improvements in performace both aircraft would have had with the R-2000 installed.

I've never heard a pilot complain of having too much power.   

[earl1937]

I've never heard a pilot complain of having too much power.   

Unless you were the test pilot who first flew the "Bearcat"!