Info via http://vtol.org/news/30th-anniversary-of-g-lynx-flight30th Anniversary of G-LYNX Flight
The Absolute World Helicopter Speed Record
Held for 30 Years and Counting
By Geoff Byham
At the beginning of 1986, the British helicopter manufacturer Westland experienced a crisis brought about by a shortage of orders and needed to attract financial backing. It was felt that a demonstration of the company’s technical capability would attract interest from the business world and allay the savage press comments that had arisen from the situation. The company had achieved significant success in many technical areas, none more so than with its new rotor technology, first flown on August 8, 1985, so it was considered that attempting to take the world speed record would provide a dramatic demonstration of the company’s potential.
The new British Experimental Rotor Programme (BERP), which had been developed by Westland working with the UK Ministry of Defence, had produced a rotor blade, recognizable through its distinctive tip geometry, that had shown all of the predicted advantages to the rotor flight envelope, delaying the retreating blade stall problems by some 35 kt (65 km/h). At practical weights, a Westland Lynx could readily exceed the existing Mil Mi-10 outright helicopter world speed record of 198 kt (367 km/h) using this rotor. So Westland decided that a Lynx had to be configured and cleared to make an attempt on the outright helicopter speed record providing a dramatic demonstration of the company’s capability.
Starting with a basic utility Lynx the main problem areas, not surprisingly, were a need to increase installed power and transmission clearance from the production standard. Solutions to these problems were available from other projects that could furnish more powerful engines (the Rolls-Royce Gem 60 boosted by water-methanol injection), and clearance to run the transmission at one engine inoperative (OEI) contingency power with both engines running. Indeed, the engine power was likely to exceed the transmission capacity by a modest margin on a cool day and the opportunity was taken to fit smaller exhaust pipes to make use of the excess thermodynamic energy that did not get into the gearbox.
The other threat was the high internal load level that the tail rotor would experience at the speed record high torques and advance ratio. With this issue unresolved, the project would not be viable. Again the problem had a largely ready-made solution from a Lynx stablemate, the Westland 30. Its low set, double sided tail-plane with endplate fins angled to lift to starboard would offload the tail rotor. Confidence was such that the company invited all the major suppliers and project partners to hear the plan. There was unanimous support.
The Ministry of Defence loaned the instrumented development components used in the blade flight-test program and Rolls-Royce prioritized the engine clearance program needed for the flight release.
Work commenced in early May with the provision of the disassembled company demonstrator G-LYNX and critical engine testing started in mid-May. It was planned to be ready to fly with all changes in place by August 4th and to make the first record attempt on August 11th, in order to make an impact at the Farnborough airshow. First flight was on August 1st with a hectic week of problem solving as aircraft trim and tailplane loads became obstacles that had to be resolved — the self-sufficient team was able to deal swiftly with routine servicing issues.
And so in the calm hazy evening of August 11, 1986, G-LYNX flew over a measured 15 km (8 nn) course in Somerset and achieved an average speed 400.87 km/h (216.5 kt), setting two Fédération Aéronautique Internationale (FAI) official records that remain unbroken today. Everything worked as planned, leading to lots of publicity at Farnborough. Afterwards G-LYNX and most of the dynamic components went back to routine test flying duties.
The whole exercise was a team effort, not only for those directly involved, but by their colleagues who supported them throughout the company. The whole workforce took pride in the achievement, and this August will celebrate the unbroken records after 30 years.
Note: High-speed compound flights have not been recognized as official FAI records.
About the Author
Geoffrey M. Byham joined Westland in 1968 as a research aerodynamicist, and was closely involved in the BERP rotor development. He was later appointed as chief aerodynamicist, and played key roles in what is now the AW101, serving as chief engineer, chief scientist and finally as head of engineering at Westland Helicopters.