The North American P-51 Mustang
By Chuck Hawks
Many aviation authorities regard the North American P-51 Mustang to be the best American air superiority fighter of the Second World War. Many top aces flew the Mustang, including Colonel Donald Blakeslee (15 victories) and C.O. of the famous 4th Fighter Group (which destroyed over 1,000 German aircraft, more than any other American fighter group in WW II), Captain Don Gentile (35 victories), Captain John Godfrey (31 victories), and General Chuck Yeager (the first man to break the sound barrier). Also Colonel Eagleston (23 victories), commander of the 354th Fighter Group of the Ninth Tactical Air Force, and top ace of the 9th. Also in the 9th was Major James Howard, the only American ace in both theaters of the war (6 victories in China flying P-40's, and 6 victories in Europe flying P-51's).
This glorious airplane came about when the British contacted North American Aviation in 1940, with a request to build fighters for the RAF. North American was willing, and they offered to design and build a new fighter that would meet British requirements, and be easy to mass produce. The British accepted and the rest, as they say, is history.
In only 102 days NAA rolled out the first prototype Mustang. By November 1941, the first of over 600 aircraft produced under British contract were delivered to the RAF.
The streamlined new fighter incorporated some advanced ideas, in particular a laminar flow wing of thin cross section, which allowed the Mustang to avoid most of the "compressibility" dive problems that plagued many other high performance fighters of the time. Two of the first ten Mustangs built were taken to Wright Field, at Dayton Ohio, for testing by the AAF, which designated them XP-51.
The 1,150 hp. Allison F-series V-12 powered the early Mustang models. This resulted in poor high altitude performance, so the RAF used their Mustang I (P-51) and II (P-51A) models for low altitude ground attack and reconnaissance duties. These they performed very well.
The Mustang I had a top speed of 370 m.p.h. at 15,000 ft. Best climb at 11,300 ft. was 1,980 ft/min. An assortment of .30 and .50 caliber machine guns were carried, but the Mustang IA was armed with 4-20mm cannon. Handling and maneuverability were good. Like the FW 190 and Spitfire, the P-51 was a pilot's airplane.
P-51A (Mustang II) production was divided between America and Britain. This model standardized armament as 4-.50 cal MG. (two per wing). There were ground attack versions of the P 51A in U.S. service, designated A-36A, which served the AAF in the North African campaign. There were also specialized photo reconnaissance versions of all major Mustang models, the F-6 series.
The decision was made to mass produce the outstanding Merlin engine under license in the United States. The P-51B and C models (Mustang III in British service), which entered service in December of 1943, were powered by the new Packard-built version of the Merlin V-12, driving a four bladed propeller. At the same time, the airframe was strengthened, the radiator was re-designed, the ailerons were improved, and racks for long range drop tanks or bombs were added under the wings.
This new engine completely changed the character of the Mustang, and resulted in what was probably the best all around piston-engine fighter of WW II. It came at a crucial moment for the AAF daylight bombing campaign. Luftwaffe fighters had taken such a toll of un-escorted heavy bombers that the losses were becoming un-supportable. The great range of the P-51B-7 (which also carried drop tanks), allowed it to escort the heavy bombers all the way to their targets deep inside Germany. In March of 1944, Mustangs went all the way to Berlin. Eighth Air Force bomber losses plummeted, while Luftwaffe fighter losses skyrocketed.
The 1,450 hp. Packard/Merlin engine (1,595 hp. war emergency rating) gave the P-51B-7 a top speed of 445 m.p.h. Best climb was 3,320 ft/min at 10,000 ft. The new Mustang carried 4-.50 caliber MG(two per wing), and up to 1,000 lb.. of external stores. Its range was an astounding 2,200 miles with two 150 gal. drop tanks. Endurance with drop tanks was 8.7 hours.
As 1944 progressed, things continued to get worse for the Axis powers. The improved Republic P-47D model arrived with greatly increased range (2,100 miles with drop tanks), and so did the definitive Lockheed P-38L model, with even greater maximum range than the single engine fighters. Now the Luftwaffe was often outnumbered over its own homeland. For the German fighter force, the end was at hand. On the other side of the world, the Imperial Japanese Army and Navy fighter forces were being decimated by the new Allied fighters.
As Allied fighters gained air superiority in both the European and Pacific theaters of war, the Mustang was increasing tasked with ground attack chores. In this role it was also successful, although the P-51 was at its best as an air superiority fighter. Its single, liquid-cooled engine made it more succeptible to ground fire than the durable P-47 with its air-cooled radial engine or the twin engine P-38. A single bullet through a vulnerable cooling line could bring a Mustang down with a siezed engine.
Later in 1944, the P-51D model arrived. This became the most famous Mustang of them all. It sported a "tear drop" canopy for better all around vision, and a more powerful 1,790 hp. version of the Packard/Merlin engine, along with many detail improvements. Maximum speed was about 437 m.p.h., and the armament was increased to 6-.50 caliber wing MG. All manner of external stores could be carried. Reconnaissance versions were also produced. Recognition of the D model is easy, because of its teardrop canopy and the large fillet fin added in front of the vertical stabilizer. The specifications that follow are for the P-51D.
P-51D's in Europe spearheaded the B-17 and B-24 heavy bomber streams that delivered the final crushing blows to Berlin and the other German industrial centers. In the Pacific they cleared the way for the B-29 formations that did the same thing to Tokyo and Japanese industry, sweeping aside the defending Japanese fighters.
The Japanese Raiden intercepter, designed specifically to engage heavy bombers, initially had some successes against unescorted SuperForts. The USAAF response was to provide Mustangs to escort the heavy bombers. That ended the treat, for the Raiden proved to be no match for the agile P-51. This is how Japanese ace Saburo Sakai described those events in his book Samurai!:
"For a short period of time the fighters broke the B-29's myth of invinciability, and the Raiden's four cannon and flashing speed raised our hopes by blowing several B-29's out of the sky."
"The enemy's answer was to send swarms of Mustangs over Japan during the daylight raids. The swift enemy fighters tore savagely at our planes and slaughtered them. Where the Raiden shone against the B-29, it was helpless before the swifter, more manuverable Mustang."
The final major production version of the Mustang was the P-51H. This re-designed model incorporated major improvements, as extensive in scope as those incorporated into the FW 190D or Spitfire Mk. 22. It was based on the experimental lightweight F and G versions. These were attempts to build extremely long range Mustangs for escort work in the Pacific War.
In the H model, the structure was increased in strength by 10%, to allow higher "g" loads in combat maneuvers. No structural part was left in common with earlier models. The Mustang, already more maneuverable than most of the enemy fighters it faced, could now pull even tighter turns. Also, the canopy was raised for better visibility, the ailerons were altered to improve the roll rate, the wing was re-designed for greater lift and less drag, radiator fairing contours were improved, and the tail was re-designed for greater strength and more surface area. This last change is easily visible, as the size of the vertical stabilizers fin fillet was greatly reduced. Streamlining was improved to increase speed, and stability was increased. A new version of the Packard/Merlin, incorporating water injection, delivered over 2000 hp. All of these changes resulted in the finest American fighter of the war. Speed was 486 m.p.h. at 30,000 ft. best climb rate was 5,350 ft./min. at 5,000 ft. Service ceiling was 41,600 ft.
A total of 15,386 Mustangs were built in the U.S., plus a limited number in other places (Austalia, for example). Unlike most other American piston engine fighters, which were withdrawn from service soon after the end of WW II, the Mustang fought on. It was the sole piston engine fighter retained well into the jet age by the USAF. I have always felt certain that this was primarily a tribute to its success in the air superiority role during WW II.
Unfortunately, the new reality was that piston engine fighters were no longer the arbiters of air superiority; the new jet fighters were to perform that role in future conflicts. Piston engine fighters, such as the Navy's Corsair and the Air Force's Mustang, were now relegated to the close support ground attack role, for which the P-51 was not really the best choice. The durable P-47's and P-38's, both of which could lift more ordinance and had more firepower than the P-51, got the axe while the Mustang served on.
Regardless, the Mustang performed valuable ground support work in the Korean War. And occasionally its pilots found enemy Yak-9's to engage, in a reprise of its WW II air superiority role.
The Mustang was adopted by many other nations, about 50 in all, and remained in service in some countries into the 1960's. Today the appearance of a Mustang performing aerobatics is the highlight of many an air show. And modified Mustangs have won many speed trophies, thrilling spectators at events such as the Reno Air Races.
Copyright 2003 by Chuck Hawks. All rights reserved.