There are special requirements for carrier-based aircraft, which can lead to the appearance of unusual designs. A striking example of this is the American project Grumman XF5F Skyrocket, as a result of which the Navy could receive its first twin-engine fighter.
New requirements
In September 1935, the US Navy Bureau of Aeronautics issued requirements for a promising carrier-based fighter. Document SD-24D stipulated the creation of an aircraft with the highest possible flight characteristics, superior to existing samples. Several aircraft manufacturing companies have joined the work. Soon the fleet considered several projects, but none of them satisfied it.
In January 1938, the Bureau formed a new technical task SD112-14, taking into account the experience of previous work and recent progress. In accordance with the new document, the future fighter with a mass of 9 thousand pounds (4.1 t) was supposed to reach speeds of more than 480-500 km / h and show the maximum possible rate of climb. The takeoff distance with a headwind of 25 knots was limited to 60 m. Armament - two 20-mm cannons and two 7, 62-mm machine guns, as well as 90 kg of bombs. The developers were advised to consider a single- and double-engine circuit.
Already in April, Grumman presented its project with the working designation G-34. He proposed the construction of a twin-engine fighter with air-cooled engines and a special airframe layout. According to calculations, the new design made it possible to obtain all the desired flight characteristics.
The next months were spent studying the project, and on July 8, a contract was issued for the completion, construction and testing of a prototype aircraft. The project received the naval designation XF5F, and the future prototype was indexed XF5F-1. The name Skyrocket was also used. Already in October, tests of the model in a wind tunnel began.
Special design
Based on the results of the purges, the final appearance of the future XF5F was formed. The design was based on the traditional architecture of twin-engine aircraft with engine nacelles on the wing, but major changes were made to it. The rearrangement of the power plant, fuselage and empennage made it possible to obtain both general advantages and benefits in the context of operation on aircraft carriers.
The aircraft received a straight wing with two spars, equipped with hinges for folding. On the center section there were two engine nacelles, which were maximally displaced inward. Inside the wing, it was proposed to place sealed fuel tanks with a neutral gas filling system.
Due to the proximity of the engines and propellers, it was necessary to abandon the protruding nose of the fuselage, and its fairing was located directly on the wing. As a result, the fuselage was less elongated, which gave the aircraft a specific appearance. The nose compartment of the fuselage was intended for the installation of weapons; behind it was a single-seat cockpit and an instrument compartment.
The tail unit was built according to the H-shaped scheme. The keels were placed in line with the engines. This improved the airflow to the empennage and increased the efficiency of all rudders.
For some time, the issue of engines was being resolved. The development company insisted on the use of well-developed Pratt & Whitney R-1535-96 engines with a capacity of 750 hp, but the Navy wanted to use Wright XR-1820-40 / 42 products (two versions with different directions of rotation) with a capacity of 1200 hp.with. For obvious reasons, the final version of the project included more powerful engines, which required some alteration of the airframe. XR-1820 engines were equipped with Hamilton Standard three-blade propellers.
The landing gear included two retractable main engine struts and a fixed tail wheel on the fuselage. The tail of the aircraft also contained a hydraulically operated landing hook.
The initial requirements provided for the armament of the aircraft with two cannons and two machine guns. At the turn of 1938-39. 7, 62-mm weapons were required to be replaced with 12, 7-mm systems. It was also proposed to equip the fighter with 40 light anti-aircraft bombs. In the future, their number was reduced. 20 bombs were placed in special containers under the wing. However, the XF5F-1 prototype never received standard armament and was tested without it.
In the last months of 1939, Grumman began building a prototype fighter, and the vehicle was ready early the next year. It had a wingspan of 12.8 m (6.5 m folded), a length of 8.75 m and a parking height of less than 3.5 m. Dry weight did not exceed 3.7 tons, normal takeoff weight was 4.6 tons, maximum - 4, 94 tons. In terms of weight characteristics, the aircraft did not meet the requirements, but the developers managed to negotiate with the Navy and settle this problem.
Testing and debugging
On April 1, 1940, a Grumman test pilot took the prototype XF5F-1 into the air for the first time. The plane performed well, but showed some shortcomings. Over the next several months, specialists were engaged in testing the equipment, determining its characteristics and eliminating the identified deficiencies. The first stage of testing, carried out at the developer's airfield, lasted until the beginning of 1941 and included approx. 70 flights.
During the tests, a maximum speed of 616 km / h was reached. The rate of climb exceeded 1200 m / min - by 50-60 percent. higher than other fighters. The ceiling is more than 10 km, the practical range is 1250 km. Thus, in terms of range or rate of climb, the experienced XF5F-1 surpassed the existing carrier-based aircraft, but lost to them in speed.
The aircraft had good maneuverability, but in some cases excessive loads on the control stick were observed. The special design of the fuselage did not interfere with the forward view. The plane could continue flying with one engine running. However, some time had to be spent on fine-tuning the oil cooling system, hydraulics and other units. In addition, the issue of armaments remained unresolved. Requirements of this kind were constantly changing, and the XF5F-1 remained unarmed until the very end of testing.
After the completion of the refinement, in February 1941, the prototype was handed over to the Navy for further testing. Over the next few months, the XF5F-1 Skyrocket was compared with other promising models.
Trials, training, literature
It quickly became clear that the experienced fighter from Grumman did not have decisive advantages over its competitors and, most likely, would not win the competition. The development company began to lose interest in its own project, although it continued to cooperate with the Navy. Soon the negative forecasts came true. The winner of the program was Vought. In the summer of 1941, she was given an order for 584 F4F-1 fighters.
However, the XF5F-1 was not abandoned. This machine received the status of a flying laboratory, and it was planned to use it in new research in the interests of carrier-based aviation. Flights and tests of various kinds continued over the next several years and provided the necessary data collection. In 1942, there were two accidents, after which the aircraft was restored and returned to service.
In 1942-43. experiments were carried out with a complex of weapons. The installation of various sets of machine guns and cannons was being worked out. One of the consequences of this was the appearance of a new fuselage nose. The enlarged fairing protruded beyond the leading edge of the wing.
The last flight of the XF5F-1 took place on December 11, 1944. Due to a chassis failure, the pilot had to perform a belly landing. The plane was seriously damaged, and it was decided not to restore it. Soon the damaged machine became a kind of simulator for practicing the rescue of pilots. A few years later she was scrapped.
Meanwhile, one of the publishers was releasing a series of Blackhawk comics about the adventures of a fighter squadron. In the fictional world, the F5F Skyrocket fighter has reached series and operation; the main characters used this technique from 1941 to 1949. Obviously, the comic book authors were attracted not by the combination of technical characteristics, but by the unusual and recognizable appearance of the aircraft.
Mixed results
The aim of the XF5F Skyrocket project was to create a promising carrier-based fighter with improved flight performance. This problem was only partially solved. The resulting aircraft had good maneuverability and climb rate, but was inferior in other parameters. Such an ambiguous result did not suit the customer, and the project was abandoned.
In parallel with the carrier-based XF5F, the XP-50 land fighter was developed. He repeated the basic decisions of the basic project - and the result was similar. The XP-50 was unable to compete with other machines and did not go into production.
Despite the abandonment of production, the XF5F-1 proved to be useful in a new capacity. In 1941-44. he was used to gain experience in the operation of twin-engine fighters, and then he helped train rescuers. The US Navy carrier-based aircraft was on the verge of a new era, and soon the existing experience found practical application.
