March 1937: The USAAC had expressed interest in the streamlining advantages offered
by the liquid-cooled engines and asked for designs built around the new Allison V-1710.
Work began on designing an Allison-powered P-36A. This aircraft was given the Curtiss
designation Model 75I.
1 April 1937: The XP-37 prototype serial No.37-375 was delivered to the USAAC. The
supercharger was extremely unreliable. The cockpit was moved way aft for balancing
the center of gravity. Visibility was obstructed on the ground and in the air.
Engine: Allison V-1710-11 Turbo-supercharged 1,000 hp./20,000 ft.
Test Weight: 6,350 lbs.
Speed: 340 mph./20,000 ft., Climb: 20,000 ft./7.1 minutes., Service Ceiling: 35,000 ft.
Armament: 1 x 0.3 in. + 1 x 0.5 in.
30 July 1937: Curtiss began designing an Allison V-1710-19 powered P-36 that positioned
the radiator location under the fuselage behind the wing. This arrangement kept the center
of gravity similar to the P-36 so the cockpit did not have to move aft. This design was
designated Model 75P.
11 December 1937: The USAAC ordered 13 YP-37 service test versions.
3 March 1938: Curtiss submitted the design Model 75P to the AAC showing that an Allison
powered P-36 could be expected to achieve 350 mph. at 15,000 ft.
26 April 1938: The USAAC approved the XP-40.
14 October 1938: The 1st flight of the H75P (Model 75P) piloted by E. Elliot with Allison V-1710-19
1,160 hp./T.O. 1,090 hp./2,950 rpm./10,000 ft. Armament was 1 x 0.3 in and 1 x 0.5 in machine
guns. Speed was a disappointing 299 mph.
December 1938: The XP-40's radiator is moved forward and the design is refined. The aircraft is
now capable of 342 mph./ 12,200 ft.
25 January 1939: The Army Air Corps holds a fighter competition which includes the XP-40, XP-37,
Model 75R (P-36A with turbo-supercharger), AP-4, XP-38, XP-39 & XP-41.
March 1939: The USAAC asks Curtiss for proof that the P-40 can reach the 360 mph./15,000 ft.
that they promised.
April 1939: The USAAC declares the XP-40 as the winner of the fighter Trials and gives Curtiss a
contract for 524 P-40s.
26 April 1939: US War Department announces the contract for 524 P-40s at a cost of $12,872,898
after Curtiss increased its guaranteed speed to 365 mph.
9 October 1939: The French Purchasing Commission orders 230 Hawk 81A-1 Tomahawk Is.
Combat Weight is 6,250 lbs. with 100 US gallons of fuel. No armor and unprotected fuel cells.
No armor glass in windscreen.
Engine: Allison V-1710-33: 1,040 hp./T.O.
Armament: 2 x 0.5 in. (12.7 mm.) machine guns.
December 1939: The XP-40 is further modified and manages 366 mph./15,000 ft.
11 January 1940: France requests 25 P-40s, buy this is not allowed by the current export laws.
25 March 1940: Lend-Lease goes into effect per President Roosevelt.
4 April 1940: 1st production P-40 is flown by test pilot Lloyed Child. Flight weight was 6,787 lbs.
Speed: 357 mph./15,000 ft. (4275 m.) Initial Climb: 3,080 fpm. Range: 950 mls./250 mph.
May 1940: England orders 560 H87A Kittyhawk Is.
6 June 1940: A French H81A-2 is flown by Lloyed Child.
Spring 1940: Combat reports from Europe made it clear to the USAAC that its fighters were
deficient in regards to pilot and fuel cell protection compared to contemporary British and
17 June 1940: England takes over French H81A orders and increases the order to 1,180 aircraft.
140 P-40s had been produced then the last 90 on the original order were partially modified to
UK standards and designated Tomahawk IA (H81A-1).
June 1940: 1st P-40s are delivered to the 33rd, 35th and 36th Squadrons, 8th Pursuit Group at
Langley Field, Virginia.
1 July - October 1940: 20 P-40s and one P-40G were shipped to Russia.
September 1940: The P-40D (H87A-2) is ordered by the USAAF.
November 1940: Tomahawk II and IIB deliveries began to England.
6 January 1941: 100 H81A-2 Tomahawks are sold to China for use by the AVG.
Armament: 2 x 0.5 in. + 4 x 0.3 in. machine guns.
February 1941: 1st P-40B reaches USAAC Squadrons. Armament: 2 x 0.5 in. + 2 x 0.3 in. machine
April 1941: P-40Bs go to Hawaii. The become part of the 15th and 18th Pursuit Groups.
April 1941: Tomahawks from England began reaching the Gold Coast to be assembled. No.3 Squadron
is the first to be equipped with the Tomahawk IIB.
April 1941: 31 P-40Bs are sent to the Philippienes, 20th Pursuit Group.
30 April 1941: Deliveries of the P-40C to the USAAC began. Armament: 2 x 0.5 in. + 4 x 0.3 in machine
May 1941: 1st P-40D is delivered to the USAAC. Armament: 4 x 0.5 in. machine guns in the wings.
7 May 1941: 420 British Lend-Lease P-40E-1 Kittyhawk IAs are ordered. Armament: 6 x 0.5 in.
machine guns in the wings.
June 1941: 100 H81A-2s arrive in Rangoon, Burma for use by the AVG.
8 June 1941: No.250 squadron score the first Tomahawk victory in North Africa.
20 June 1941: The United States Army Air Corps becomes the United States Army Air Force.
30 June 1941: The First flight of the Rolls Royce Merlin powered Warhawk XP-40F.
July 1941: The British offer 200 Tomahawks to Russia.
23 July 1941: P-40Ds are sent to the 6th AF in the Caribbean.
29 August 1941: 1st P-40E is delivered to the USAAF.
September 1941; P-40E-1 export model began to be delivered. Most went to North Africa.
October 1941: 1st Russian Tomahawks go into combat.
October 1941: Tomahawk IIBs of the South African Air Force went into operation in North Africa.
28 October 1941: The USAAF ordered 600 P-40Ks.
7 December 1941 8:00 a.m.: Japanese attack Pearl Harbor, Hawaii.
8 December 1941 2:30 a.m.: Japanese attack the Philippines
20 December 1941: 1st combat operation in China by the AVG.
22 December 1941: 18 P-40s are delivered to Brisbane Australia. By 4 February 1941 one hundred
thirty-eight P-40s are assembled and comprise forming the 3rd, 13th, 17th, 20th & 33rd Squadrons.
1 January 1942: 1st Combat for Kittyhawk IAs (P-40E-1) in North Africa.
3 January 1942: 1st P-40Fs (Packard built Rolls Royce Merlin V-1650-1) are delivered to the USAAF.
This engine had a single stage two-speed supercharger.
March 1942: 112 Squadron RAF in North Africa began experimenting with Kittyhawks as fighter-
bombers with a 250 lbs. bomb.
Late March 1942: 6 of 30 P-40Es are delivered to the AVG (Flying Tigers) via Africa and India.
May 1942: 1st P-40Ks are delivered to the USAAF.
16 May 1942: RAF No.112 Squadron (H87-4/P-40E-1) becomes the 1st Fighter-Bomber Squadron
in the Desert Air Force, North Africa.
31 July 1942: 1st combat of the P-40F in Palestine, Western Desert Air Force.
9 August 1942: 1st USAAF P-40F victories, North Africa. 2 Bf.109s are destroyed for the loss of one
December 1942: 1st deliveries of the P-40M began to UK.
23 December 1942: P-40Ls arrive in Egypt for the 9th AF, USAAF.
March 1943: 1st deliveries of the P-40N-1. Armament: 4 x 0.5 in.
13 June 1943: 1st flight of the XP-40Q-1 No.42-9987 (P-40K-10 modified) at Curtiss in Buffalo, NY.
Engine air intake positioned above cowling.
Radiator and oil cooler were moved from the chin to the wing center sections.
Engine: Allison V-1710-101: 1,325 hp./T.O. & 1,500 hp./6,000 ft.
Length: 37' 4" (about 2 feet longer than a standard P-40). Wing Span: 35' 4".
1 September 1943: P-40N-5s and P-40Ms become operational at Baker Island. 45th Fighter Squadron.
November 1943: The XP-40Q-1 is modified into the first XP-40Q-2.
Tear drop bubble canopy was installed after cutting down rear fuselage.
Engine coolant radiators position in wings just outboard of the landing gear.
Oil and engine air intake were placed back under the chin now more streamline.
Engine: Allison V-1710-101
January 1944: The XP-40Q-2 was further modified and new engine installed then delivered to Eglin Field.
Wingtips were clipped, span: 35' 3".
Engine: Allison V-1710-121 with water injection: 1,425 hp./T.O. and 1,800 hp./20,000 ft.
Late March 1944: 1st flight of the XP-40Q-2A No.42-45722 (P-40K-1 modified).
Mostly the same as the XP-40Q-2 except slight modification to the canopy and cockpit.
Engine: Allison V-1710-121 with water injection and automatic radiator and oil cooler shutters.
April 1944: The XP-40Q-3 No.43-24571 (P-40N-25 modified) was delivered to the USAAF.
The flat windscreen was longer & more angled and the canopy was slightly smaller.
30 November 1944: P-40N-40 No.44-47964, the last Warhawk, leaves the Buffalo, NY plant.
Control surfaces were metal covered
Engine: Allison V-1710-115 automatic boost and propeller controls.
1949: P-40Ns of the Netherlands East Indies are used against Indonesian rebels. This is the last
combat use of the P-40.
1958: The P-40N is still in service in Brazil.
America's Hundred-Thousand by Francis H. Dean
US Army Air Force Fighters Part 1 by William Green and Gordon Swanborough.
Edited by CORSNING, 15 January 2017 - 12:43 PM.