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Home | Update | Latest Issue | Gallery | FR Profile | Datafiles | FR 3/97 HELMET DISPLAYS FOR FIGHTER PILOTS by Karl Schwarz Helmet mounted visors are not new. The US Navy and Marine Corps used Honeywell's Visual Target Acquisition System from 1973 to 1979 in approximately 500 of their Phantom fighters. In the eighties the Russian air forces introduced a relatively simple helmet display into the MiG-29s. The Israelian company Elbit, with its DASH system (available from the end of 1986), has been a pioneer for this concept. Intensive development works for helmet displays of fighter pilots have been accomplished in countries such as France, Great Britain, and the USA since then. The US forces have tested more than two dozens different helmets. However, not one is being used operationally today. This is going to change. The arguments to use helmet mounted displays are stronger than ever. New and highly maneuverable air-to-air missiles are almost demanding that pilots be able to acquire a target with just a quick movement of the head. Furthermore, the presentation of relevant flight data to the pilot, no matter where he is looking, may become a decicive advantage in critical situations. However, to realize the promising possibilities of a helmet display is still not easy, several conditions must be taken into consideration. First, the helmet must not become to heavy from adding the visual system. Two kilograms should not be exceeded. Otherwise the pilot will have difficulties during a turning combat to move his head due to the high g-forces. Also, the center of gravity (CG) should not be to far forward to avoid straining the pilot's neck muscles. An unfavorable CG position would also endanger the pilot during ejection due to dangerous head nodding. Along with this, a safe separation of the data/power lines from the helmet must be ensured for a safe escape from the aircraft. A helmet mounted visor only makes sense if a certain accuracy can be achieved. It should be within one degree. Also, the system must be rigid enough for the day-to-day rigors of flying operation. Companies like Elbit, Kaiser Electronics, Honeywell, GEC-Marconi Avionics and Sextant Avionique are currently working on the realization of these requirements. A relatively similar configuration is evolving from these works. The symbols or sensor data are projected directly on the visor. The problem is to avoid distortions on the spherical area and to minimize the translucent characteristics of the visor. 80 percent is where they stand with the current status of this technology. Concerning the size of the angle of view, the systems can be devided into three categories: Helmet visors which only work as target designators manage with 3,5 to six degrees. The second generation visors which also display flight information data commonly have an angle of view of 20 degrees, with the goal to reach 40 in the future. The display is still monocular. Binocular systems with a field of view of 40 x 40 degrees will probably be the next step of the development. Only these make sense when trying to project infrared pictures for night operations. The symbols in most of the systems are generated by a miniature CRT. Elbit gives a solution of 500 lines for its DASH helmet. LED displays are sufficient for simple visors. This has the advantage that the use of high-voltage current can be omitted. Honeywell is working on miniaturized LCDs as an alternative to the CRTs. The projection of the symbols on to the visor itself is accomplished by precision optics. A weak magnetic field, generated by an electromagnet in the size of a cigarette pack that is mounted to the canopy bow, is used in most systems to measure where the pilot is looking. Several sensors on the helmet measure the changing field strength, allowing to calculate the exact line of vision. Since alone the best helmet display is worthless, a good integration of the system into the aircraft's avionics is most important. The feedback must be as little as possible. Values above 100 to 150 milliseconds can already lead to pilot confusions. If everything works, the pilot has an extremely helpful tool for air combat available. Seekerheads of complex air-to-air missiles can be directed by the move of the pilot's head, increasing the shot probability dramatically. Sensors like radar and IR cameras can be pointed fast and simple. The same applies to air-to-ground operations. Updates of the inertial system are possible with just one look on known positions. At the same time, the helmet display allows the display of information from the aircraft systems, for example the positions of the most threatening opponent or the status of the weapons system. Along with visor functions, the helmet display can show relevant flight data; the pilot can concentrate on the outside and is less dependent on his HUD or cockpit instruments. According to an Elbit study, all of these together can give an advantage of 3:1, assuming that both aircraft are equipped with conventional Sidewinder missiles. In combination with highly maneuverable missiles that can "shoot around the corner" this advantage even increases to 9:1. With these numbers in mind and the system being available for a price that is approximately equal to one air-to-air missile, it is no surprise that Elbit has logged already 500 orders for the newest version of the DASH helmet. The system will be integrated into F-15s, F-16s and F-4 Phantom IIs. Last fall, Elbit won the bid for the Joint Helmet Mounted Cueing System together with Kaiser Electronics. Under the lead of McDonnell Douglas, JHMCS will supposedly be integrated into F-15Cs and F/A-18C beginning in 2001. F-16Cs and F-22s will be next. In Europe, Sextant Avionique is developing the Topsight helmet for use in the Dassault Rafale. It is an entirely new design, featuring an integrated oxygen mask. A version with binocular display and sensor display is also under development. The British company GEC-Marconi Avionics has already developed several helmet displays, ranging from the simple Alpha Sight, Viper I and II to the fully integrated Crusader system. A derivative of this could be used for Eurofighter. The Swedish FFV Aerotech has begun with the development of the ODEN system, a simple helmet visor for possible use with the Gripen. From page 50 of FLUG REVUE 3/97 Home | Update | Latest Issue | Gallery | FR Profile | Datafiles | FR 3/97 Copyright 1997 by Motor-Presse Stuttgart. All rights reserved. Last updated February 13, 1997