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Advanced Aerodynamics
The P-51 Mustang design featured two groundbreaking features -- a laminar-flow airfoil and a radiator cooling system that
actually increased the airplane's thrust.
Laminar-Flow Wing: This was a concept that had originated at the NACA laboratory but had yet to be incorporated into a
production airplane. Essentially a laminar-flow airfoil features a relatively thin leading edge with the section's thickest point
placed as far back as possible. In theory, this would insure that the boundary layer airflow adhered, or stayed "laminated",
to the wing further aft of the leading edge than with any other airfoil section. This would be especially beneficial in high
speed maneuvering situations, where airflow over conventional airfoils would break up much earlier on the wing surface,
causing drag inducing turbulence. The catch was that a laminar flow airfoil required a perfectly smooth highly finished
surface, which was difficult to achieve in mass production. Seeking ultimate performance in a wartime situation, North
American went all out, devising a method of filling and sanding the front part of the P-51 wing to ensure laminar flow.
Thrust Producing Cooling System: Prior to the P-51, high-speed liquid-cooled fighter aircraft like the P-40, Spitfire, and
Me-109, were loosing 10% or more of their power to cooling system drag. In an ingeniously designed new cooling system
arrangement, the P-51 actually created thrust as the hot air was trapped and supercharged, and then, exited at a greater
velocity than it entered. The net gain was to offset almost all of the drag that the cooling system created. The faster the
airplane flew, the more pronounced the benefit became. At high speed, the Mustang's power loss to cooling system drag
dropped to a mere 3%. This gave it a 20 - 30 mph speed advantage over other fighters with similar horsepower. North
American executive Lee Atwood offered this explanation; "The full-power propeller thrust was about 1,000 lb. and the gross
radiator drag was about 400 lb., but the momentum recovery (of the new system) was some 350 lb. of compensating thrust
- for a net cooling drag of only some three percent of the thrust of the propeller".
A Merlin Engine For The P-51B
While the first Allison-powered Mustang was better than the P-40, the switch to the more powerful Merlin engine (the
Spitfire engine), which was rated 420 hp more than the Allison, made it truly outstanding. Now, the P-51 could reach a
speed of 440 mph at 30,000 feet, and a climb to 20,000 feet required only five minutes and 54 seconds. The P-51B was
approximately 30 mph faster than the Spitfire, with the same engine, and faster at high altitude than any other fighter
airplane of the time. This was a remarkable advance in flight performance!
The addition of a new 85-gallon fuselage tank gave the P-51B a huge internal gasoline tank capacity (around 425 gallons).
This meant its range was 1,080 miles, and it could be extended to 2,600 miles when extra drop-tanks were attached to the
wings -- far more than any other allied or German fighters of the time.
The first P-51Bs began arriving at U.S. 8th Air Force units in England in December 1943. The German Luftwaffe fighters
were about to get a rude awakening!
Turning The Tide
For the bomber crews, the P-51B was a Godsend. The new Mustang gave the Allies a new hope, as it quickly began to
change the outlook of the air war. Now, when the P-47s turned back low on fuel, the Mustangs pulled up to take over
escort, all the way to Berlin! The Luftwaffe could no longer attack unprotected bombers. As one general said about the
slightly less limber P-51; "The Mustang won't do what a Spitfire does, but it does it over Berlin."
The first P-51 ace was Major James H. Howard of the 354th Fighter Group, flying his P-51B named "Ding Hoa". On
January 11, 1944, he shot down five German fighters to become an "ace-in-a-day". He was awarded the Medal of Honor
for this feat. During that same air battle, 49 new P-51B's shot down 15 enemy planes without suffering a single loss.
By April 1944, the P-51B Mustangs had decisively taken control of the skies over Europe. Its superior capabilities
shortened the war immensely. They turned what had been a brutal stalemate into victory for the Allies. Without the P-51B
Mustang, the bombing of Germany would have had to been halted. With the Mustang, the tragic losses suffered by bomber
crews was greatly lessened.
Don Gentile and Saga of "Shangri-La"
One of the most famous P-51B aircraft is "Shangri La", flown by the 4th Fighter Group ace Don Gentile. Gentile totaled 30
kills during the war, breaking Eddie Rickenbacker's WWI record of 26. Incredibly, he scored two-thirds of his kills in a short
6-week period in March and early April of 1944 -- right after he started flying his new P-51B.
Don Gentile was a seasoned veteran by the time the P-51B arrived on the scene. He had originally enlisted in the Royal
Canadian AF before the U.S. entered the war. He was posted to England in 1941, flying the Supermarine Spitfire with the
famed "Eagle Squadron". He claimed 2 kills in his time with the squadron. In September 1942, the Eagle Squadron was