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Avro 707

1949 COLD WAR X-PLANE

History

The classic British "V-bomber" - the Avro Vulcan - features a complex, large-area delta-wing plane design that gives the jet bomber a unique and highly recognizable form. However, to produce a reliable and effective design requires prior evaluation of more controlled designs and technologies to demonstrate that the approach is feasible, which is one form of the delta-wing Avro 707 technology demonstrator.

The platform allows data to be collected and changes to be initiated on a smaller, cheaper scale, rather than in the form of an expensive full-size bomber. Like the Avro 707, the Handley Page HP is part of the Vulcan program. 88 Research aircraft to another V bomber - Handley Page Victor.

Two smaller single-seat aircraft were built, the Model 707 (1/3 scale product) and the Model 710 (half-size version), before a full-size Vulcan prototype was ordered with a crew of 5. Each will meet different program objectives, and the 707 is designed for low speed, low altitude handling and performance. This was followed by two prototypes of the 707, the VX784 and VX790, originally intended for convenience and resource cost control, and constructed primarily of wood. However, this design plan was quickly abandoned in favor of an all-metal plane to better mimic the Vulcan's design.

The official specification - E. 15/48 - was released in October 1948 to formally advance the product, while the specification E. 10/49 appeared in July 1949 and covered the development of an experimental branch of the 707 - the model pairing was designed to be high speed Research is (models WD280 and WZ736).

Overall, the 707 looks like a Vulcan with a delta wing plane shape. The middle of the wing is mounted on either side of the tubular fuselage, and the cockpit is located forward of the root of the wing and aft of the short nose cone assembly. The increased cockpit position provides a relatively good view of the front of the aircraft.

The wing assemblies sweep nicely along their leading edge and straight along their trailing edge, terminating at a sharp point at the tip. The tail consists of a vertical tail, while the delta plane also inherits the function of a typical horizontal tail. The single engine is hidden in the aft fuselage of the aircraft and, interestingly, is drawn in through semicircular split vents located on the fuselage dorsal near the midship. This particular design quality doesn't reflect the final Vulcan shape at all, which places the air intakes on the leading edge of the wing.

A few other design qualities of the 707 were chosen just to expedite its manufacturing process, including the nose wheel assembly and cockpit from the Gloster Meteor F.3 fighter jet, and the main landing gear legs from the Avro Athena trainer.

After completing the necessary roll tests, the first flight of a 707 was recorded on the VX784 on September 4, 1949, and the aircraft was subsequently exhibited at Farnborough in 1949. Unfortunately, the plane took the life of the test pilot during a routine test flight, which crashed to the ground on a low speed/low approach. The crash was caused by deploying air brakes that pressed the plane's tail into the ground.

Engineers then developed a new air brake assembly for future 707 flights.

The VX790 model has a slightly longer fuselage - just over two feet - and an improved nose cone with a new nose cone borrowed from Hawker Sea Hawk. The installation of this leg provides the fuselage with a higher "nose-up" attitude, which helps increase lift during takeoff.

New airbrakes were also implemented on the model, and these changes required a slight revision of the original 707 name to become "707B". The 707B made its maiden flight on September 6, 1950.

Subsequent flights demonstrated the viability of the tailless delta wing design, although a recurring issue was the engine's ability to receive adequate airflow during flight. The study found that the raised cockpit structure in front of the air intakes delayed the flow of air into the slits, which in turn prevented the engine from delivering the required power output. It was decided to add a "hump" along the fuselage spine at the intake structure to better direct airflow over and behind the canopy. This work delayed further testing for a while, and a landing accident on September 21, 1951, raised additional concerns - the plane's nose was damaged and the test pilot was injured but survived.

After repairs, the aircraft was exhibited at Farnborough for a second time in 1952, but its history was marred again by a second landing accident in 1956. With no more flights, the 707B was officially scrapped in 1960.

The high-speed models WD280 and WZ736 already mentioned were developed from 1949 on the basis of their own ideas. These airframes, however, feature an all-new delta-wing design, including forward-facing air intakes like the Vulcan bomber itselflosing the ridged air intakes on the 707B. Collectively known as the 707A, the WD280 and WZ736 were more representative of the ultimate Avro Vulcan bomber form than the unique 707B and its sister aircraft.

The high-speed 707A first flew on June 14, 1951.

However, with the actual airworthy prototype of the Vulcan bomber providing more of the required data during the testing phase, the 707 research aircraft is now all but functional. As a result, the smaller 707 models proved to be of little value, and from 1952 the Vulcan program developed more or less without their help. Testing of these research aircraft continued for some time, with the addition of the two-seat "707C" (WZ744), which had a side-by-side cockpit seating arrangement.

In a final effort, the remaining four 707 program participants flew together during Farnborough in 1953.

After completing four different Avro 707 shapes, each aircraft has slightly different structural dimensions and performance. The original 707 was powered by a Rolls-Royce Derwent 5 turbojet with 3,500 pounds of thrust, while the 707B was powered by a 5-pound equal thrust Derwent. The 707A was equipped with a Derwent 8 turbojet with slightly increased thrust to 3,600 pounds, while the two-seat 707C model had the same engine mount. Gross weight gradually increased from 707 to 707C, from 8,600 lbs to 10,000 lbs.

Those features aside, the plane remains largely true to the original 707.

For a period of time, the WD280 was in service on Australian soil through the Commonwealth Aviation Advisory Research Council (CAARC). It was taken over by HMAS Melbourne. It served there from 1956 to 1960.