at the Flight Simulation Center of National Aerospace Lab. in June 1982 by 4 pilots (two Kawasaki Heavy Industries, Ltd. and two NAL pilots). See Fig.2 The tests were done to develop the HUD's CTOL and STOL symbology and to functionally check each mode. About 400 simulated approaches and landings were made 6)
Fig.3 Pseudo B mode in Queen Air Flight Test
The first flight tests of HUD were done on the NAL B-65(Queen Air) at the Chofu airfield and Sendai Airport in November, 1983. The purpose of the tests was to check the accuracy of the IRU and to evaluate the HUD See Fig.3. In the flight test three major subjects were evaluated. The first was the delay between HUD displayed symbology and real world scene which are caused by the IRU and HUD computer Systems.
The second was an evaluation of the fight path reference symbol (discussed later) which may replace either the Instrument Landing System(ILS) or Visual Approach Slope Indication System(VASIS) for glide slope information during visual conditions. The Last was a pretest of the radar guidance system up-link and the radar System guidance accuracy 7)
The radar guidance mode was added to allow high precision landings to be made in all weather conditions using a three dimensional ground tracking radar and a telemeter Up-Link. A HUD-telemeter interface on board the aircraft included complementary filters to provide precision position and accurate inertial velocities to display a perspective runway and an accurate flight path symbol.
The second flight simulation tests were done at NAL, June, 1984, by 5 pilots (2 Kawasaki Heavy Industries, Ltd. and 3 NAL pilots) 8)
Fig.4 Radar Guidance B Mode in Second Simulator Test
The primary purpose of the tests was to develop the radar guidance mode. About 300 approaches and landings were made for HUD evaluations of the CTOL and STOL configurations in conditions of category II Instrument Meteorological Conditions(l MC). The simulator tests used simulated wind turbulence and radar noise obtained from the flight tests of the Queen Air described previously. Also the inertial system speed drift errors were simulated by a sine wave to model the Schuler oscillations observed in flight tests. See Fig.4.
The flight test of Aska started in October, 1985 and continued through March, 1989. The landing configuration characteristics of Aska made precise approach and landing diffcult. Sluggish flight path response due to low heave damping, large ground effects, and sensitive gust response are some of these characteristics. Ground effect causes a large pitch down moment and a reduction in the sink rate during flare and landing 8)9) Long period longitudinal gust can give large sink rate changes because of the back side characteristics 10). For approach, flare and precise
