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Lockheed P-38 Lightning: Fork-Tailed Devil

Decent article.

Note: While the P-38 garnered the majority of attention due to the "compressibility" issue, many of the Tier 1 fighters had issues with compressibility.


More...

Several WWII fighters experienced issues with compressibility, including the P-38 Lightning, P-47 Thunderbolt, F4U Corsair, and Typhoon. These aircraft, designed for high-speed dives and maneuvers, encountered "compressibility" where airflow became turbulent and unpredictable as they approached the speed of sound, leading to control problems and structural damage.

P-38 Lightning: The P-38, while known for its high-altitude performance and climbing capabilities, faced significant compressibility issues in dives. Its high-lift wing design, while good for climb, also made it vulnerable to a loss of control and structural failure at high speeds. To mitigate this, dive flaps were introduced to help slow the aircraft and allow for more controlled dives.

P-47 Thunderbolt: The P-47, a heavy fighter known for its powerful engine and high performance, also encountered compressibility issues, particularly during dives. These issues could lead to control difficulties and even structural damage.

F4U Corsair: The Corsair, a powerful naval fighter, also struggled with compressibility problems, though it was more resilient than some other aircraft.

Hawker Typhoon: The Typhoon, an early British fighter, experienced compressibility issues with its thick wings, which limited its performance at high altitudes and speeds. These issues were addressed in later versions of the Typhoon, such as the Tempest, which featured thinner wings with a laminar flow airfoil.

Other Notable Aircraft:
  • Stuka: The Stuka dive bomber, while not a fighter, also experienced compressibility issues due to its high dive speeds, as noted by one forum thread.

  • Mustang: The Mustang, while generally a very capable aircraft, also encountered compressibility issues, see above link.
 
Decent article.

Note: While the P-38 garnered the majority of attention due to the "compressibility" issue, many of the Tier 1 fighters had issues with compressibility.


More...

Several WWII fighters experienced issues with compressibility, including the P-38 Lightning, P-47 Thunderbolt, F4U Corsair, and Typhoon. These aircraft, designed for high-speed dives and maneuvers, encountered "compressibility" where airflow became turbulent and unpredictable as they approached the speed of sound, leading to control problems and structural damage.

P-38 Lightning: The P-38, while known for its high-altitude performance and climbing capabilities, faced significant compressibility issues in dives. Its high-lift wing design, while good for climb, also made it vulnerable to a loss of control and structural failure at high speeds. To mitigate this, dive flaps were introduced to help slow the aircraft and allow for more controlled dives.

P-47 Thunderbolt: The P-47, a heavy fighter known for its powerful engine and high performance, also encountered compressibility issues, particularly during dives. These issues could lead to control difficulties and even structural damage.

F4U Corsair: The Corsair, a powerful naval fighter, also struggled with compressibility problems, though it was more resilient than some other aircraft.

Hawker Typhoon: The Typhoon, an early British fighter, experienced compressibility issues with its thick wings, which limited its performance at high altitudes and speeds. These issues were addressed in later versions of the Typhoon, such as the Tempest, which featured thinner wings with a laminar flow airfoil.

Other Notable Aircraft:
  • Stuka: The Stuka dive bomber, while not a fighter, also experienced compressibility issues due to its high dive speeds, as noted by one forum thread.

  • Mustang: The Mustang, while generally a very capable aircraft, also encountered compressibility issues, see above link.
The pilot I mentioned earlier had that happen during a dogfight. Before that on the same mission he spotted Japanese Zeros so he dropped he external fuel tanks and began engaging the enemy.
Soon both engines cut off. He forgot to switch to his internal fuel tank. He actually scored a Kill while gliding his P-38!
He got the engines running again 👍
 
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Drop tanks were actually a contentious issue especially with the bomber mafia. The P-38 could fly to Berlin yet the bomber mafia remained adamant that bombers could fly unescorted on long range missions. And bomber crews paid the price for their stubborness. Meanwhile, the 5th AF in the Pacific had P-38s flying long range escort missions from the get go. The video will make your blood boil.

 
Drop tanks were actually a contentious issue especially with the bomber mafia. The P-38 could fly to Berlin yet the bomber mafia remained adamant that bombers could fly unescorted on long range missions. And bomber crews paid the price for their stubborness. Meanwhile, the 5th AF in the Pacific had P-38s flying long range escort missions from the get go. The video will make your blood boil.

This chart is biased aginst the P-38 since it also had 165 gal. and 300 gal drop tanks so it could fly as far as the furthest P-51 radius on the chart & beyond that.

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@Cedric

I did some research and discovered that the the J-25 and L's were good for 1,770 miles (2 X 885 mi.) with 2 x 165 tanks, which betters the above chart's P-51 w/2 108 gal DTs radius.

Also found these pics that you might find interesting.

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Plus...

From a Quora thread...

Charles Lindbergh singlehandedly doubled the range of the P-38.

The early models of P-38 didn't carry much internal fuel, and could only manage about 900 miles in a clean configuration.

Long-range cruise control had been a Lindbergh specialty since his solo Paris flight, and he had studied the problem extensively while serving as a technical adviser to Juan Trippe’s Pan American Airways. He instructed the P-38 pilots to operate their engines at low rpm, not high, and at auto-lean, not auto-rich, extend the P-38’s range by at least 400 miles by managing manifold pressure and fuel flow in a technique that he was then asked to teach to other P-38 fighter groups.

Essentially, his recommendations boiled down to moderate Manifold pressure and low engine rpm, combined with lean carb mixtures to let the turbos do all the work of providing manifold pressure and manually setting the propeller pitch.

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His recommendations were based on the strengths of the Allison powerplant used in the plane, that being good fuel economy at lean mixtures. The P-38's Allison engines have a noticeable edge in fuel economy over the P-51’s Merlin engines at low-power cruise settings (35" of mercury and under (how they measured manifold air pressure back then)), but there's a big difference when the MP rises over 40" and the P-51 can stay in auto-lean, whereas the P-38 has to go to auto-rich and its fuel consumption shoots up. At combat power the two are basically equal (the V-1650-7 at 61" and the V-1710 at 60" are both rated at 180 GPH).

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The pilots had previously been flying nearly the worst possible combination; high rpm, low MAP and auto-rich. They didn't like Lindbergh's recommendations because they made the engines run rough, but after Lindbergh flew some demonstration missions they were convinced.

His recommendations were the equivalent of putting a car in top gear at 30mph after fitting extra large tires to it. You aren't going to go fast or have a lot of acceleration, but you will go very far.

Milo Burcham managed 2907 miles with 2 x 330 gallon externals in August of '42. They estimated that more economical flight profile and dropping the tanks when empty would have made 3200 miles reachable.

That isn't a practical combat range, but correctly piloted 80% of that probably was attainable. Regardless, it allowed the P-38 to strike targets completely undefended in the Pacific, simply because the Japanese thought they were unreachable.

More beauty shots...

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Also, the P-38 was chosen for escort duty during D-Day as her unique profile was so recognisable, and combined with the black and white “Invasion Stripes,” would help trigger-happy anti-aircraft gunners from shooting at her.

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Compared to wing-mounted guns.

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The P-38 was one of the very rare fighters to have electric “Dive Flaps,” (the other being the P-47 Thunderbolt). Note: The F8F Bearcat also had them. It was in service but barely missed combat due to VJ Day.

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Above: Dick Bong, America’s Ace of Aces, 40 Japanese victories, checks out the dive flaps.

The heavy, fast, powerful P-38 desperately needed dive flaps to counter the massive compressibility problems it had in the dive, but was only given the flaps all models from June 1944.

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Too bad the "K" model never went into production (but with all the "L" improvements).

P-38K-1-LO

Single airframe. Modified from a P-38G-10-LO (42-13558) by fitting more powerful 1425 hp V-1710-75/77 (V-1710F-15) engines, rated at over 1875 hp war emergency power. This required redesigning the cowlings and making them similar to those used on the P-38J. Propellors with broader-chord were fitted, necessitating the need to increase the diameter of the spinners, which in turn changed the shape of the cowling lines and the interface at the oil cooler/intercooler inlet.

Tests of the P-38K were carried out between February 24 and April 30, 1943. The performance of the P-38K was quite a bit better than that of the production P-38J--in fact its performance was superior to all other American fighters then in production. Maximum speed at 29,600 feet was 432 mph an at 40,000 feet, the P-38K was 40 mph faster than that of the P-38J. It was projected that top speed at war emergency power could be in the 450 mph range. The P-38K's initial rate of climb was 4800 feet per minute, allowing a climb to 20,000 feet in approximately five minutes. Service ceiling was projected to be above 48,000 feet. The aircrafts range was projected to show a 10-15% increase.

While clearly superior to the P-38J in many regards, the intense pace of production meant that the War Production Board was unwilling to allow even a short production suspension in order to retool for the required changes to the engine cowling. As a result, the P-38K remained a singular model.

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