#MERLIN PROJECT UPGRADE SERIAL NUMBER#

The original Allison V-1710 engine weighed in at 1335lbs while the Packard Merlin tipped the scales at 1690lbs. First, the forward fuselage was redesigned and strengthened with new motor mounts. Even though this airframe resembled the lines of its original form as a P-51A, it was vastly different.

#MERLIN PROJECT UPGRADE SERIAL NUMBER#

The test dummy for the new Merlin was a P-51A Mustang conversion carrying the USAAF serial number of 41-37352. This Packard Merlin would be known as the V-1650-7 and would be the go to engine for the Mustang. However, because of this new supercharger gear ratio, the engine had less horsepower above 21,400ft than the “high altitude” Merlin. The impeller controller changed over to the high blower at 14,500ft, compared to 20,000ft for the V-1650-3. Which was right in the wheelhouse of altitudes where a majority of air battles occurred during World War II. This version used different supercharger impeller gear ratios (5.802:1 low ratio and 7.349:1 high ratio) that favored more horsepower at takeoff and through the middle altitudes of 8,500ft through 21,400ft. Packard went back to Rolls-Royce for plans for their “low-level” engine named the Merlin 69. As a result of mission reports from air-to-air engagements building up, the upper echelons stepped in and wanted to tweak the power curve to put higher performance between altitudes where most battles occurred. While the Packard Merlin V-1650-3 put the Mustang at the top of the performance charts for US fighters, it still had more to give. Harker wrote to Rolls-Royce with persuasive words to get their engine in the Mustang and as a result a legend was born. The test was all about the airframe, even with the lower powered Allison, it was still faster than the current Spitfire Mk V already sporting a version of the more powerful Merlin. Luckily, he had the perfect solution with his company’s two stage supercharged Merlin engine. Once Harker took the Alison upwards thought, he hit the limit of the engine. What it could do at lower altitudes of course. On April 30th, 1942, Harker took to the air and after thirty minutes of flight time he was blown away by what the Mustang could do. He called up Ronnie Harker, a Rolls-Royce service liaison pilot, to fly the new Mustang. He knew the numbers, he knew the performance, he knew it was the most aerodynamically perfect plane he had. In 1942, Wing Commander Ian Campbell-Orde, commanding officer of the Air Fighting Development Unit (AFDU) at Duxford Aerodrome in England, was staring out his window at a brand new Allison-powered Mustang (AG422). Luckily, across the pond was an engine that would make the P-51 Mustang one of the most famous fighter aircraft of all time. The downfall of this engine is the drastic decline in performance at higher altitudes and with the bombers flying at 30,000ft the Mustang needed a new power plant. The Allison-powered Mustang was designed to be a low altitude performer and could reach a max speed of 415 mph at 10,400ft with the single-stage, single-speed supercharger. Now, this isn’t a criticism of the 1,120 hp, twelve cylinder, supercharged, Allison V-1710 engine that powered the P-51A and the Royal Air Forces Mustang II version. However, with the progression of the air war and the introduction of high altitude bombing campaigns, the Mustang needed an engine boost to keep up. The Mustang airframe is an aerodynamic masterpiece.

Mustang! Is there a name that better embodies the essence of sleekness and power than a wild stallion? The engineers at North American Aviation (NAA) in Inglewood, California must have been thinking the same thing when they developed the iconic design of the P-51 Mustang. Instagram page opens in new window Pinterest page opens in new window

Merlin project upgrade