Apr 142012
 

In our final article in a series on the Bell D188A/Model 2000 (a.k.a. XF-109 / XF3L—both spurious designations invented by the Bell marketing department) supersonic VTOL fighter of the late 1950s, we present a brochure and mock-up inspection guide dating from February 1959. A preview of the brochure is shown to the left; it is remarkable for being entirely focused on the USAF variant of the aircraft with virtually no mention of the Navy, which may have been signalling its intention to drop out of the program by this time. Besides giving an excellent overview of the aircraft as it stood in early 1959, the brochure is also an appealing example of corporate graphic design from the period, with blocks of yellow and blue applied throughout. The following paragraphs are adapted from the introduction to the document.

The brochure was a brief summary of the “XF-109” (D188A) V/STOL Tactical Fighter Weapon System which had been under development by Bell Aircraft Corporation under military contract since early 1957. At the time of writing, the Convair San Diego Division of General Dynamics Corporation had joined Bell to form a team to continue development and management of this weapon system.

The XF-109 Weapon System incorporated the overall mobility necessary for economically and rapidly conducting limited war anywhere in the world. Further, the ability to operate from dispersed sites combined with rear area maintenance bases, with hardened sites, provides greatly reduced vulnerability essential for modern warfare, the XF-109 Weapon System could survive an initial blow to mount an effective retaliatory offensive. Moreover, it could provide the United States with a valuable “show of strength” weapon system capable of deployment to, and operation from, any spot on the globe within 24 hours without extensive base preparation. Thus, this weapon system had a key role in global war, limited war, and cold war concepts.

This advanced, all-weather weapon system consisted of a lightweight, high-performance, supersonic VTOL airplane equipped with a complete integrated electronic subsystem including autopilot, and was capable of carrying a wide variety of armament internally. The STO feature of the XF-109 permitted missions requiring an overload in either fuel or armament or both.

The electronic subsystem performed both air-to-air and air-to-ground warfare functions. Therefore, by only a change in the armament carried and actuation of a mode selector switch in the pilot compartment, this weapon system could operate either as an interceptor or as a fighter-bomber. This versatile electronic gear, combined with the VTOL characteristics, provided the XF-109 with an unusually good takeoff and landing capability during conditions of poor visibility or iced runways.

The aircraft was a conventional configuration with a high straight wing, low horizontal tail, and area-ruled fuselage. VTOL design gross weight was approximately 25,000 pounds, and this included almost five tons of fuel, all carried internally. Basic construction was aluminum alloy with limited use of titanium and stainless steel. Maximum steady-state flight speed was limited by the engines to Mach 2.3; the dive limit was Mach 2.5.

The XF-109 was powered in horizontal flight by six J85 afterburning turbojet engines, two located in each wing tip nacelle and a pair in the rear of the fuselage. For VTOL, the wing tip nacelles were rotated. Afterburning thrust from these engines was supplemented by diversion of thrust from the rear fuselage engines and by a pair of dry J85 lift engines in the forward part of the body.

For short takeoff (STO), the rear fuselage engines and the nacelles were horizontal at the start of the ground run to provide maximum accelerating force on the airplane. Just prior to lift off, nacelles were partially rotated to furnish both lifting and driving thrust components while thrust from the rear fuselage engines was diverted to vertical. Forward fuselage engines provided lifting power as in VTOL operation. Landings were made vertically.

A reaction control system using engine bleed air was incorporated for roll and yaw control during hovering and transition flight, while pitch control was obtained by fuselage engine thrust modulation. Fully powered aerodynamic controls for conventional flight were interconnected with the low-speed control system. Thus, all controls operated from a single stick and set of rudder pedals.

Next up is a small program produced by Bell to accompany the XF-109 Mock-up Inspection, which took place February 17-19, 1959. While it doesn’t contain many illustrations of the aircraft, the program does offer a detailed overview of the inspection process as well as a snapshot of Bell facilities at the close of the 1950s. The following paragraphs reproduce the introduction to the document.

For over twenty years, Bell Aircraft Corporation had pioneered in virtually every known method of flight and propulsion. America’s first jet airplane, the P-59, was a Bell Aircraft product, as was the X-1, the nation’s first rocket-powered aircraft. The Bell X-2 still held the speed and altitude records for manned flight.

The vertical take-off and landing concept was first investigated as far back as 1941 when Bell Aircraft made application for a patent for a VTOL tailsitter utilizing contra-rotating propellers and powered by a reciprocating engine.

In 1952 the Air Force issued a feasibility study contract for a development program leading to the design of a jet-propelled VTOL and a year later, convinced of the need, Bell Aircraft financed the design and a fabrication of the Air Test Vehicle. The first controlled hovering flight was made in 1954, and a year later the ATV accomplished its first in-flight thrust rotation from horizontal to vertical and back to horizontal.

An Air Force contract to develop the X-14 was awarded in 1955 and two years later this vehicle successfully demonstrated the deflected thrust principle.

In 1957, Bell Aircraft won a Navy design competition with the D188A VTOL fighter, and work was begun on the initial Phase I design of the D188A under BuAer contract. The continuation of Phase I had resulted in this mock-up, now designated the XF-109. This had been accomplished under the joint sponsorship of the Air Force and Navy.

In addition to military contracts, and concurrent with them, Bell Aircraft had financed considerable research in the V/STOL field.

Against the growth in size and weight of contemporary supersonic aircraft and the parallel growth of runway length to accommodate them, the military potential of the lightweight supersonic XF-109 V/STOL was indeed impressive.

Bell believed that its extensive experience and proven capability in this field qualified it to successfully carry out the XF-109 program.

To read through the document in depth, please see below. Unfortunately, the author has not found photos of the mock-up inspection referenced in the program; hopefully these will surface in the near future.

Conclusion

While this may be the final entry in our series on the Bell D188A/Model 2000/XF-109, it is not the end of the story. The Navy ultimately dropped out of the program in 1959, sometime after the aforementioned documents were published; this was likely due to skepticism regarding the viability of the supersonic VTOL fighter concept, friction with the Air Force over management of the contract, and budgetary constraints.  Undaunted, the USAF continued funding development of the aircraft, with Bell showing off a revised version of its “XF-109” mock-up on December 5, 1960. The Air Force eventually lost faith in the program and cancelled it in the spring of 1961, with no examples being built, despite the significant amount of time, money and effort expended by Bell on the D188A and its antecedents. Undoubtedly, there remains a large amount of reports and correspondence (especially on the Air Force side) concerning this contract awaiting discovery and publication; hopefully other researchers will undertake the necessary research and help round out the historical picture of this early, ill-fated attempt at developing a supersonic VTOL fighter aircraft.

All images from NARA Archives II, College Park, MD, RG 72

Access to High Resolution Images

Example of high resolution image (click to enlarge)

Readers may purchase a high resolution 72 page PDF reproducing the documents previewed above through our shop on Gumroad.com; an example of a high resolution image is shown to the left.

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