And that is the myth. Many old books and new internet articles, you-tube videos say the P-40 was
designed for ground support or low level work.
From an old book by William Green.
"
When the requirements for the P-40 were formulated, no prospects of a high-altitude enemy attack against the U.S.A was envisioned, so that coastal defense and ground attack were the main tasks indicated. Low altitude flying qualities and rugged construction therefore received priority, and, in fact the P-40 was subsequently to to prove itself an excellent ground attack weapon."
This was written or at least published in 1957. It does play rather fast and loose with the requirements for the P-40. The XP-40 was built to compete in the 1939 fighter trials held in Jan 1939. The XP-39 missed. Several modified P-36s and P-35s and a few others showed up. The order for the P-40 for over 500 planes was placed in April of 1939.
Now in the Spring of 1939 nobody, anywhere in the world, had any prospects of conducting high altitude attacks against anybody else.
The idea that a plane armed with a pair of cowl mounted .50 cal guns (the .30s in the wing came later) and no (or a few 20lb bombs) was much use for coastal defense (anti ship) or ground attack is pretty ludicrous.
P-40 was a P-36 with a new engine. From the firewall back it was the same airplane so I guess the P-36 was designed for ground support or low level work?
BTW it took another year and half for armor or protected fuel tanks to show up.
In the next paragraph we find;
"
Unfortunately, the rated altitude of the Allison engine was only some 12,000ft, rendering combat above 15,000ft a completely impractical proposition."
This also plays fast and loose with the timeline and any connection with the original requirements or design goals of 1938-39.
In April 1939 the Allison engine was best high altitude engine the Army was likely to get in quantity in 1940.
The Engine was rated at 1040hp at 14,300ft (?)
at that time. Which is about 2000ft lower than the Merlin III of that time but
better than any other engine in 1939.
Unfortunately things changed. Army wanted 1090hp and the Allison could do it, but only around 1000ft lower, it would still make 1040hp at the original altitude.
The engine used in the P-40E was rated at 1150hp at 12,000ft or just under. However it would still make 1040hp just over 14,000ft.
The next change came with the addition of the .30 cal guns. At first 2 but very soon 4 guns (1/2 the armament of the British fighters but with more ammo) while still keeping the .50 cal guns, which weighed about as much as 6 British .303 guns.
Next change was the addition of armor and protected tanks. This is the fall of 1940.
The P-40 went from 6787lbs with 370lbs of guns/ammo to,
The P-40B at 7326lbs with 600lbs of guns and ammo and 93lbs of armor to,
The P-40E at 8098lbs with 901lbs of guns/ammo and 109lbs of armor.
P-40E lack of performance at altitude in 1942 had nothing to do with the requirements or design criteria of 1938/early 1940.
It had a lot to do with the US army over-loading the plane with guns/ammo/fuel and not being able to change the engine very much.
Add 1300lbs to Hurricane I (Merlin III) and see what would happen to altitude performance
So far nobody has been able to come up with any USAAC directive or memo or requirement that says the P-40 was intended to used at low altitude only.
The army wanted higher altitude planes, but they estimated they couldn't get them until 1941-42 (turbos, etc) and they needed planes in 1940. Then they gave (or traded production space) to the French and British in 1940 so the US didn't even get most of the planes they
originally ordered. Allison was frantically trying to increase production while trying to come up with improved models. No war in Europe in 1939 might mean faster development of higher altitude versions and smaller number of of -33 and -39 engines?
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