Hughes Model D-2 (XP-73 / XA-37)

1943 WORLD WAR 2 X-PLANE

• 1 History of the Hughes D-2 (XP-73 / XA-37)
• 2 Hughes Model D-2 (XP-73 / XA-37) Specification
  • 2.1 Basic
  • 2.2 Production
  • 2.3 Roles
  • 2.4 Dimensions
  • 2.5 Weight
  • 2.6 Performance
  • 2.7 Performance
  • 2.8 Armor
  • 2.9 Changes

History of the Hughes D-2 (XP-73 / XA-37)

The Hughes D-2 was created circa 1937 to compete with the United States Army Air Forces (USAAC) for a contract for a two-armed "fast fighter". Government agencies deemed Hughes' submissions too slow for the role, lacking the proper rate of climb to meet their demands, and subsequently awarded the development contract to rival Lockheed and its prototype "XP-38." The XP-38 eventually evolved into the war-winning P-38 Lightning, the famous single-seat, twin-engine, two-armed "Fork Tail Demon" as the Germans know it.

The outcome of the selection certainly reinforced Hughes' already growing suspicion that the U.S. military would never accept a Hughes-designed aircraft into service just because Hughes was involved. Still, as a private company, work continues on the D-2, hoping to eventually sell a "can't-miss" product to the U.S. military.

Development continued into 1938, as Hughes also saw the D-2 as an opportunity to set new flight records and further cement his legacy as a pioneer pilot. At this point, the D-2 was already a twin-engine, dual-arm design with a centralized nacelle containing the cockpit, avionics and fuel depots. The rear of the outriggers houses the vertical tail and an attached horizontal plane -- a design similar to Lockheed's competing XP-38, a configuration that Hughes believes the company stole. However, Hughes' design was for a crew of five (instead of two) and was given a "to the rear" landing gear design (instead of a tricycle) - at least on paper.

Additionally, the aircraft will be built by Duramold, a special plywood process licensed from Hughes - the idea being to use wood in mass production for the military that doesn't require a lot of valuable aluminum - a common material at the time airplane. Under the pressure of a wartime economy, this was logistically sensible.

The Duramold process involves birch, high pressure and high temperature, which will cause the material to form into the various shapes required. The end result is a lightweight rigid structure. Instead, manufacturing the process requires some effort, which can slow down mass production.

To follow the airframe approach, Hughes focused on a pair of high-performance engines in the Wright XR-2160 Tornado, which USAAC allowed Hughes to use. The engine will drive the four-bladed propeller assembly. In 1939, Hughes persuaded USAAC's materials department to purchase a new fighter, and the contract was signed on May 22, 1940.

2 goals.

The original design included a top speed of 300 mph and a bomb load of up to 4,000 pounds, and was considered for the bomb role - hence its multi-person crew. A glassed nose cone would help roll the bomb, and an internal bomb bay would be mounted under the wing assembly main spar at the rear of the cockpit. However, as was the case with the D-2 throughout its life cycle, the design was changed in March 1941 to a two-seat long-range fighter, now with a turbocharged engine, with a range of 2,600 miles, a range of 450 miles per hour, and a 6 x .50 Caliber heavy machine gun. In May of the same year, the design was revised again by USAAC to fulfill the bomber escort role, which required stamina, adequate armament and maneuverability. It is this difficult development that has given the D-2 a variety of official and unofficial designations throughout its existence.

Hughes' official (and original) company name was D-2, and the internal designation for its militarized form was Model D-3. The D-2 was subsequently known as the D-2A, and at one point various experimental modifiers were offered in the XD-2 and DX-2.

At some point, the three-seat light bomber version was also known as the Hughes D-5.

The United States officially entered World War II after the Japanese Navy's surprise attack on Pearl Harbor, Hawaii, in December 1941. On June 30, 1942, Hughes' design was more or less still in play and was given the official experimental military designation "XP-73".

If the vehicle goes into production, it will receive the official production model designation "P-73" as well as a USAAC designation. However, by next month, for some reason the D-2 had been written as "XA-37" in official USAAC documents - presumably for the attack-oriented role of the "A-37".

As the war progressed, USAAC became interested in all types of war materiel. Although the idea of ??Duramold craftsmanship and wooden fighter-bombers was not entirely convinced, it was an interesting alternative to an all-aluminum fighter jet, especially under the resource pressures of war. In fact, the British de Havilland fighter-bomber Mosquito was quite a success, dubbed the "Wooden Wonder" due to the extensive use of wood in its construction.

Although USAAC authorities have tried to gather more information about Hughes' progress on the D-2 model, the company has provided little information - the aircraft was developed under a huge veil of secrecy that led to the D-2 2 being banned from light duty as a viable military platform. Hughes himself didn't help either, and instead funded the sinking project himself, which helped the U.S. military a lot.

When the D-2 program was threatened by a loss of interest in the materials department, Hughes pulled his political element to stay in the game. However, he kept the development of the D-2 firmly under his control through official government support.

Airframe construction continued under Hughes' direction, although delays in the Wright Tornado engines forced Hughes to purchase the lower-rated Pratt & Whitney R-2800-49 series. Another change to the layout was the use of three-bladed propellers instead of the four-bladed propeller originally envisioned. The engine also benefits from a Hughes Aircraft-designed turbocharger for improved performance.

The plane was fully assembled at Harpers Dry Lake in Murroc - again in secret. The design also evolved into a two-seater cockpit with intentional pressurization for working at heights. The trailing undercarriage was dropped in favor of a more forward-looking three-wheeler layout.

In this configuration, the D-2 is expected to have a top speed of 445 mph and a range of more than 1,000 miles at full combat load - although these are estimates.

In the spring of 1943, with the war in full swing, Hughes took over control of his D-2. At this point, the aircraft still lacked internal turbochargers and cabin pressurization, but planning required ground operation of the system, which Hughes himself did. However, the tests revealed military control issues that require serious consideration. The first official flight of the fuselage was recorded on June 20, 1943, and control problems became so apparent that the fuselage required extensive modifications, especially the wings.

Hughes engineers had few options, increasing the span of the main wing assembly, adding flaps in the outboard area and lengthening the trailing edge, but these changes did not completely solve the problem and required a major redesign.

Anyway, the Hughes D-2 was eventually eliminated from all serious action by the end of the war, and its role was filled by a bunch of other competing types. Aside from Hughes' own antics, USAAC didn't really believe in the concept of an all-wood military aircraft in the age of metal planes. Also, there are questions about Hughes' commitment to his own programs and the ability of Hughes facilities to produce the number of aircraft needed for the war.

The design was never completely cleared of its engineering flaws, and the secrecy surrounding the aircraft hindered USAAC's chances of even seeing what was in development. The U.S. Army's interest in the product ended on August 13, 1943.

In the overall development of the D-2, the three-seat D-5 alternatives mentioned above had some military value and took on three different forms, the first being a dedicated light bomber form. The second model is to fulfill the role of escort fighter and has a crew of two. A third model has been added - a two-seat long-range reconnaissance platform without weapons. It was this particular entry that resonated with U.S.

Air Force authorities as they sought such a platform for long-term reconnaissance. This role was eventually shared by a number of modified fighter jet designs with photographic reconnaissance equipment. The basic design of the D-5except for the unarmed reconnaissance versionwas to include a remote-controlled powered turret in the rear of the fuselage nacelle, armed with a heavy 4 x .50 caliber Browning machine gun for defense.

The escort fighter form should be further equipped with a 6 x 20mm cannon in the nose.

With so much work already done on the D-2, Hughes Aircraft continues to develop a long-range reconnaissance platform for the U.S. military along the same lines. This could be especially useful in the battle against the Japanese Empire on the Pacific coast. The unique D-2 prototype was lost in its hangar on November 11, 1943, in what appears to be an accidental "lightning strike". The design was somewhat revived in an upcoming Hughes product - the ill-fated and eventually scrapped "XF-11" reconnaissance platform. The aircraft had a similar dual-arm design, and two prototypes were completed.

In his well-publicized crash, a plane nearly took the life of Hughes himself. XF-11 is described elsewhere on this page.

Hughes Model D-2 (XP-73 / XA-37) Specification

Basic

Production

Roles

Dimensions

Weight

Performance

Performance

Armor

Changes