Concorde Design Refinements
As the Concorde development program progressed, some design changes with a potential to reduce noise were studied. These included: (a) The use of partial displacement of the thrust reverser buckets to minimize sideline noise; (b) The use of retractable spade silencers to minimize flyover noise; and (c) The development of an engine control system to permit the largest practical nozzle area for the takeoff and landing conditions to minimize exhaust gas velocity.
In March and July 1973, noise flight tests were conducted using a Concorde equipped with these devices. The results were disappointing in that no appreciable in-flight noise reduction was provided by either method (a) or (b). The development of the propulsive nozzle control system, however, was effective both in the reduced power takeoff flyover and, to a greater extent, in the approach flyover. Following these tests, the spade silencers and use of the partial deflection of the thrust reverser buckets were deleted from the production Concorde but the nozzle area control schedule was modified to the operationally acceptable standard and incorporated on the production Concorde.
Airframe changes, such as enlarging the wing tips and improving the lift-to-drag ratio by altering the drooped leading edges along the whole wing span, do not produce significant noise reduction. Replacing the present engine with a turbofan power plant would generally increase the mass airflow and decrease the exhaust gas velocity, which would reduce perceived noise; however, it would also change performance characteristics in relation to the basic aircraft design. In short, replacing the present engine of the aircraft would constitute a major aircraft design change. Additionally, there is no existing engine technology which would provide supersonic flight capability and concurrently reduce noise.
In 1977 and 1978 BAe flight tested modifications to the wing and tail control surfaces designed to reduce drag and fuel consumption. These modifications which consisted of an approximate 0.61 m (2 ft) increase in the fin chord and an approximate 0.05 m (2 in) increase in the chord of the elevons and rudder were designed to reduce fuel consumption by approximately 680 kg (1,500 lb) on a flight of 3,500 n miles (6,485 km; 4,030 miles). Also in 1978, BAe flight tested a new thinner air intake lip. This modification reduced fuel consumption by approximately 1,360 kg (3,000 lb) on a supersonic flight of 3,500 n miles (6,485 km; 4,030 miles).
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