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Technology update
Fast-jet technology transfer
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Pilot's-eye view of TERPROM.
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Systems originally designed for fast jets are finding new applications in helicopters. British Aerospace Systems and Equipment (BASE) and Saab Aero are two European companies working on the extrapolation of established fast-jet technology. BASE revealed at the UK's Helitech 99 exhibition that initial flight trials of the helicopter version of TERPROM, the company's digital terrain system, have been successfully completed. The trial involved a British Army Lynx helicopter. TERPROM is a software-based product that combines aircraft radar altimeter readings with a digital terrain map to provide an autonomous navigation capability. Accurate navigation amid the terrain and knowledge of the terrain around the aircraft allows the generation of predictive ground-proximity warnings. It also alerts the pilot to the proximity of masts and powerlines. Originally developed for low-flying fast jets, TERPROM has been selected for, and is in service on, a wide variety of aircraft, including the F-16, Mirage 2000, Harrier GR7, Tornado, and Eurofighter Typhoon. The transport aircraft variant, TAWS (Terrain Awareness Warn-
ing System), has been selected for the U.S. Air Force's Boeing C-17 fleet.
For the helicopter trial, TERPROM provided dynamic terrain advisory cues combined with a map of the surrounding terrain, enabling the pilot to assess his course of action while remaining at low level. The flight installation combined TERPROM with a BASE/Honeywell LINS 764GT inertial navigation system, a Racal Avionics CDU (control and display unit), and visual output to a Smiths Industries' flat-panel color display in the cockpit. Audio output is via the crew intercom. BASE Navigation Specialist Paul Davies said that an initial problem associated with helicopter use of TERPROM was that the throughput of terrain information is relatively slow. "However, this has been corrected and the flight tests in a Lynx were successful," said Davies. "Having first solved the navigation element, we then looked at how the ground proximity should operate. On the head-up display seen by the pilot, three zones ahead of the aircraft are being monitored, and chevrons mark these. As the terrain becomes more of a 'threat,' the chevrons become larger and eventually, if there is danger to the aircraft from ground proximity, the chevrons come together to form an 'X' and there is an oral 'Pull up!' warning to the pilot.
"There is a lot of interest in ground-proximity-warning systems for helicopters. It has taken time because of the need to solve the problem of slow flight and hover. We believe this is the only ground-proximity-warning system in the world that also incorporates navigation. Ground proximity is becoming increasingly important for helicopters as safety issues receive more prominence. We are working hard both with U.S. and European helicopter prime contractors. Further flight tests are planned in the UK and U.S. TERPROM could be in service on military helicopters within three years."
Saab is also looking to adapt systems developed for its Gripen jet fighter that may meet the requirements of military helicopters within the Nordic Standard Helicopter Program. "These could be weapons systems, com-
munications systems, data link and other technologies," said a spokesman for Saab Aerospace. "Helicopters are moving towards a more and more sophisticated system layout and there is the need to communicate with utility helicopters, fighter aircraft, tanks, and troops." Although Saab said it is too early yet to give details of what specific Gripen-based equipment and systems might be applicable to helicopters, the recently formed Saab Helicopter Team's expertise embraces electronic-warfare systems, displays, reconnaissance systems, IFF (identification friend or foe) systems, plus advanced electronics and mechanics and electromagnetic technology services. Other elements include guided weapons, optronic systems, and defense electronics, together with navigation, guidance and control, infrared, laser and radar, and signal and image processing systems.
Stuart Birch
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