By the beginning of 1927, the American designers brought a very powerful engine, for those times, the engine - the 600-strong V-1570-1 Convertor, and Curtiss did not slow down to use it. The new engine received two aircraft, upgraded for racing 1927, the P-2, designated the XP-6, and a hybrid of the P-1A glider, XPW-8А wings with winged radiators - this was called the XP-6А. The latter became the winner of the races, overtaking his partner a little. It was on him that the US Army made the main stake, which signed 3 on October 1928 of the year, for military tests of 18 vehicles, which were assigned the P-6 index. These machines received the brand name "model 34Р". By that time, the aircraft designation system had just been introduced for military trials with the letter "Y", and although these 18 machines did not officially carry it, sometimes they were also called YP-6.
The main feature of the P-6 with the engine "Conkveror" was a new cooling system. The P-1 water radiator was replaced with a Preston radiator - with ethylene glycol cooling. Preston was produced by Union Carbide Corporation, and its main advantage was a high boiling point and a very low freezing point. The use of new coolant has reduced the required radiator area by about a third. In addition, less was needed and most coolant. As a result, the installation of "Preston" allowed to reduce the weight of the system on 22 kg.
However, by the time the Conkveror was first installed, a new radiator was not ready on the plane. As a result, the cars that arrived in October 1929, were equipped with a water-cooled V-1570-17 engine with the designation P-6.
The design and appearance of the P-6 was generally similar to the P-1. However, the new fighter received a more voluminous hood under the "Concor", which required a more rounded fuselage. The P-6 was supplied to the Army Air Corps from October 1929 to December 1930.
As soon as the first V-1570-23 Conqueror engines with Preston were ready, they were put on the first nine P-6. The aircraft, after being returned to the army, were renamed P-6A. The weight of the empty fighter dropped to 1085 kg, take-off - to 1440 kg. The maximum flight speed at an altitude of 1500 m was 282 km / h, the initial rate of climb was 9,7 m / s. Ceiling - 8325 m. Armament remains like the P-1.
Two more P-6s resulted from the conversion of two P-11 Curtissas, which, with the same glider as the P-6, originally had new 12-cylinder, V-shaped air-cooled engines Curtiss H-1640, hp 600. The Army ordered three P-11s for testing, but even before they were ready, the unsuitability of the H-1640 engines for installation on the aircraft was found out. As a result, the first two machines were converted into P-6 by mounting Conqueror liquid-cooled engines on them. The last P-11 received the Wright R-1820 Cyclone air-cooled engine with a power of 575 HP. and was renamed YP-20.
During the tests, small changes in the shape of the radiator were required, and some aircraft received a two-bladed, three-bladed screw instead. The designation XP-6А #2 was given to one of the machines, converted into an experimental aircraft for various tests. The name XP-6В was assigned to the last Р-1С, delivered by 18 July 1929 g with the engine V-1570С "Conqueror" with the power 600 hp The plane was intended for long-haul flights from the States to Alaska, especially for Captain Hait, so the car had its own name, “Hite Special”. The fuselage and bonnet lines were modeled on the Р-6. The aircraft was installed tank increased capacity. However, XP-6В managed to fly only to Valemont in British Columbia, where he made an emergency landing. After the repair and installation of an ordinary tank, the aircraft re-entered service, remaining the only XP-6. Its maximum speed at the height of 4500 m was 315 km / h, the ceiling - 9750 m, the initial rate of climb - 8,8 m / s. Empty weight was 1225 kg, takeoff -1581 kg.
The designation of the P-6C modification was originally given to 46 Y1Р-22 (the Y1 prefix was used from 1931 to 1936 year to designate aircraft ordered not by the army air corps itself, but by the "F-1" fund - this was a designation only for financial documents and was not used in technical documentation). Later for these machines instead of P-6С the designation P-6Е was used.
The XP-6D was a new prototype aircraft - an adaptation of the P-6А to the V-1570-С Conquer engine, equipped with a turbocharger mounted on the right side of the fuselage. The ground speed has increased to 275 km / h, and at the height of 4500 m - 315 km / h. Subsequently, the turbocharger was removed, and the aircraft became the standard P-6A.
From March to April 1932, all remaining P-6 and P-6А were equipped with a "Conqueror" with a turbocharger. They were renamed P-6D and were used on Langley Field in Virginia for military trials. Their main difference from the XP-6D was the installation of a three-bladed screw.
History creating the most well-known modification of the Hawk, the P-6E is quite confused and went through numerous refinements and renames. His story began with the third P-6, which, under the designation XP-22, was tested with a new liquid and oil radiator for the new 700-strong version of the "Converter" V-1570-23. In the final version, the XP-22 acquired a completely new nose of the fuselage, and the radiators were placed under the fuselage between the landing gear. The plane received a three-bladed propeller, and the machine guns were mounted on the sides - on all previous modifications the machine guns were actually located in the collapse of the cylinder blocks. In addition, the aircraft was equipped with new, free-standing landing gear with wheel fairing. Later, all these improvements were used on the YP-20, and parts and components were used with the XP-22, which, after dismantling, was turned back into the usual P-6A.
Meanwhile, the third P-11 was converted into an experienced YP-20 aircraft with an air-cooled Wright R-1870-9 Cyclone X-powered HP engine installed instead of an unsuccessful Chieftain engine. The keel and rudder were refined - the rudder balancer increased by half the length of the upper rib of the keel. Installation of the air cooling engine was considered unsuccessful. As a result, the aircraft was equipped with the V-650-1570 "Conqueror" engine with 23 horsepower, a new stabilizer and free-standing landing gear modeled on the XP-700. The tail wheel was replaced with a crutch. After these improvements, the YP-22 was renamed the XP-20E, becoming the prototype of the most well-known version of the Hawks.
8 July 1931 of the year were ordered 46 serial XP-22 under the engine of the V-1570-C (V-1570-23) "Converter". The planes were originally called Y1P-22. But, since these machines did not differ much from the P-6 in construction, they were renamed P-6С, thus simply reducing the clerical work. However, before the delivery of army aircraft, the designation was again replaced, now on P-6. In the meantime, a number of solutions tested on the XP-22 were used to refine the YP-20 to the P-6 level. The YP-20 was later renamed the XP-6, which in fact became the first prototype of the P-6.
Deliveries of the new fighter began in December 1931. The brand name was "model 35". The lightweight design allowed the weight of the empty P-6 to be reduced to 1224 kg, the take-off amounted to 1560 kg. The maximum ground speed reached 311 km / h, the initial rate of climb was 12,5 m / s. The ceiling was 7300 m, and the range - 450 km. The P-6E fighter had a rather aesthetic appearance and became perhaps the most famous army fighter in the period between the two world wars. Compared with the other army fighter - the Boeing R-12, the Curtiss plane was faster, but inferior in maneuverability. The good speed of the P-6E was a kind of compensation for the rather unimportant controllability of the fighter - it rather sluggishly responded to the “cottage” of the rudders. Engine "Conkveror" stood out among the then aircraft engines with its power, but still had a number of shortcomings that should be eliminated.
The P-6E entered service with the 1 and 8 fighter groups in 1932. They were used in 17, 94, and 33 squadrons based on Selfridge, Michigan airfields, and on Langley Field, Virginia. The fighters were in service with these units until the 1937 year. Fairly large chassis fairings, which are generally considered an integral attribute of the P-6E, when used in parts, especially in recent years of service, have been replaced with fairings that are open on both sides. The aircraft's service was marked by a whole series of catastrophes, in which at least 27 from 46 of the first series of machines were lost. P-6E became obsolete rather quickly. Instead of the planned large series, a decision was soon followed to remove these fighters from service. One by one, all the planes that had survived during the operation were taken out of the combat units, but one of them, nevertheless, reached the 1942 year.
The designation XP-6F was given to an aircraft on which a V-1570F engine (V-1570-55) was installed, with an HP 675 horsepower equipped with a turbo-compressor. This car also received a closed cockpit canopy. The take-off weight of the new modification was on the 180 kg more than the standard P-6. The ground speed dropped to 310 km / h, but at the height of 4500 m increased quite impressively - to 360 km / h. To get above this height the plane was not allowed problems with the cooling system. However, the XP-6F tests showed that at speeds above 320 km / h, using a traditional open cockpit is already a problem. Later, the XP-6F was converted into the P-6Р with the installation of the V-1570-55 engine, the HP 775 power.
The XP-6G was a P-6E equipped with a V-1570F engine without a turbocharger. After testing the aircraft, the aircraft was simply renamed to P-6G and eventually it was again converted to P-6Е after installing the standard engine.
The XP-6H designation was given to the first serial P-6E, on which four additional 7,62-mm wing machine guns were installed. Two machine guns were on the upper wing, two - on the bottom, all outside the propeller disk. Synchronous machine guns were saved, and as a result, a fighter, rather heavily armed at that time, appeared. The take-off weight increased to 1750 kg, the maximum speed dropped to 305 km / h. The aircraft was delivered to test 20 April 1933 of the year.
The last P-6E was returned to the factory for conversion to an experienced XP-23 ("63 model"). The aircraft resembled previous versions of the Hawk only with its wings. The fuselage has become all-metal mono kok. Plumage was a different form. The G1V-1570-С "Concor" engine was delivered to the aircraft with a gearbox, a turbo-compressor and a three-blade left-hand screw. The bow of the machine has become more elongated. The plane was ready for testing on 16 on April 1932. The altitude characteristics improved, but the army decided to stop all biplane work, and there was no order. The turbocharger was removed from the aircraft, after which it was renamed YP-23.
The P-6S was an export model of the P-6, equipped with the Whitney-Wasp air-cooled engine with a horsepower 450. Three such fighters in 1930 were sold to Cuba, and one to Japan.
Export aircraft R-6, as well as those sold to private individuals, were also called "Hawk-1". The first such aircraft for demonstration flights was produced in 1930. Since it was flown mainly by the famous pilot James Doolittle, the plane received its own name "Doolittle Hawk". This aircraft was later sold to Jesse Bristow, who participated in numerous aviation show until he fell into the water during the Florida-Cuba air races in January 1940.
Another Hawk-1 for special long-distance demonstration flights was released in April of 1929. It was equipped with the engine "Conkveror" and additional fuel tanks on the sides of the fuselage. After the accident, it was restored as “Hawk-1A” under the Wright Cyclone engine with 575 horsepower. and sold in August 1930 to Alford Williams, the most famous American pilot of the thirties, who participated in air shows. Since Williams had the Gulf Oil Company as a trustee, the aircraft received its own name Gulf Hawk. In August, 1931, Williams put on his plane the engine Bliss "Jupiter" with the power 575 hp, which was an American licensed version of the British Bristol engine. Following the subsequent accident, the aircraft was already restored to the Wright R-1820F-3 Cyclone engine. The side gas tanks were removed, and the fabric covering of the fuselage was replaced with a metal one. In 1958, this aircraft was restored by the efforts of the pilot Frank Talman, having received the Pratt & Whitney "Wasp" engine with the power of 600 hp. He is now on display at the US Marine Corps Museum in Quantico, Virginia. The original P-6E is now on display at the Air Force Museum at Wright-Patterson.
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