Crescent wing

Crescent wing configuration

The crescent wing is a fixed-wing aircraft configuration in which a swept wing has greater sweep on the inboard section, giving each wing a crescent shape.

As an aircraft enters the transonic region close to the speed of sound, airflow over specific parts can exceed the local critical Mach number and create supersonic shock waves, greatly increasing drag. A swept wing delays the onset of this problem by increasing the critical Mach number. The problem is most severe at the wing root, so increasing the sweep here can further delay the onset and achieve a constant critical Mach number across the whole span.

History

The crescent wing planform was invented by the German aerodynamicist Dipl.-Ing. R.E. Kosin, while working as Chief Aerodynamicist for Arado Flugzeugwerke Gmbh during the Second World War.

A prototype wing was constructed by April 1945, with the intention of fitting it to Arado 234 prototype V16. However before it could be fitted the British Army overran the site and the wing was destroyed.

Kosin's work was not lost. Design staff from the British aircraft manufacturer Handley Page - amongst whose staff was engineer Gustav Lachmann - were sent to Germany, where they were impressed by the work at Arado. They subsequently incorporated the configuration in their proposal for the HP.80 V-bomber, later to be named the Victor.

Handley Page proposed a one-third scale research glider, the HP.87, but soon abandoned it in favour of a powered research aircraft, the HP.88 having a 0.36-scale wing. The HP.88 first flew on 21 June 1951. During its brief career it showed a tendency to pitching oscillations and, on 26 August 1951, this was observed to occur increasingly violently before the aircraft broke up in the air.

By then the Victor design was already well advanced, with the first prototype flying on 24 December 1952 and production examples entering service in April 1958.

Meanwhile in France, Bréguet proposed the Br.978A design for a crescent-winged airliner. The design was not built.

Handley Page Victor

A Victor B.1 showing its crescent wing

Main article: Handley Page Victor

The Victor was the only crescent-wing type to enter production. It served with the Royal Air Force for many years, serving in a variety of roles besides bomber, including as an inflight refuelling tanker during the Falklands War.

The profile and shaping of the crescent wing was subject to considerable fine-tuning and alterations throughout the early development stages, particularly to counter unfavourable pitching behavior in flight.

During the flight tests of the first prototype, the Victor proved its aerodynamic performance, flying up to Mach 0.98 without handling or buffeting problems; there were next to no aerodynamic changes between prototype and production aircraft. Production aircraft featured an automated nose-flap operation to counteract a tendency for the aircraft to pitch upwards during low-to-moderate Mach numbers. One unusual flight characteristic of the early Victor was its self-landing capability; once lined up with the runway, the aircraft would naturally flare as the wing entered into ground effect while the tail continued to sink, giving a cushioned landing without any command or intervention by the pilot.

The Victor had good handling and excellent performance, along with favourable slow speed flight characteristics and has been described as an agile aircraft, atypical for a large bomber aircraft; in 1958, a Victor had performed several loops and a barrel roll during practices for a display flight at Farnborough Airshow.

The Victor was designed for flight at high subsonic speeds, although multiple instances have occurred in which the sound barrier was broken.

References

Bibliography

• Butler, P.; and Buttler, A.; Aerofax: Handley Page Victor. Midland Publishing, 2009. ISBN 1-85780-311-6.
• Green, W.; Warplanes of the Third Reich, Macdonald and Jane's, 1970.
• Hygate, B. British experimental jet aircraft, Argus, 1990; Pages 106-112.