angle placed another 400 meters of the apex as shown in Fig.11. This flight path error symbol has the same characteristics as the ghost aircraft symbol of ref.15.
If the pilot flies toward the apex of the Flight Path error symbol by placing the selected Flight-Path Symbol on the triangle apex, the aircraft automatically converges on the selected flight path. The time constant of the convergence will equal the time taken for the aircraft to fly the 400 meters distance or about l0seconds at STOL approach speeds. This symbol is independent of aircraft configuration, airspeed, and aircraft dynamics. The pilot can use it not only for STOL configuration but also for any other configuration. Under an Instrument Meteorological Conditions (IMC), the pilot can approach as precisely using guidance B mode as in Visual Meteorological Conditions (VM C).
Fig.11 Radar Guidance B Mode
HUD Pseudo/Radar Guidance C Mode - The Radar Guidance C Mode is shown in Fig.12. This mode uses flight director needles to indicate flight path and speed errors as commands in pitch, roll and gamma. The C mode has good controllability of the velocity and flight path but because the design point is fixed at the STOL Landing configuration and approach speed, it can not be used at other configurations nor other speeds.
Fig.12 Radar Guidance C Mode
PSEUDO APPROACH AND LANDING - The seudo approach and landing modes consist of the A, B, and C modes described earlier and provide an in-flight simulation capability for the evaluation of the aircraft's handling qualities and performance before committing to an actual landing. Steady state winds at altitude can generates large drift angles which could make evaluation difficult. Consequently, the wind velocity is removed from the inertial velocity for the Pseudo Approach and Landing modes. The wind velocities are passed through a 10 second first order low pass filter in order to determine the steady state winds. These modes all use the perspective runway and the modified flight path symbol as shown in Fig.10. The perspective runway is positioned by integration of the velocity, modified as described above for wind, from an initial position along the reference axis of the pseudo runway. The initial position and the selected flight path angle are provided as constant from the SCAS with the aircraft heading as a runway heading from IRU at mode engaged. When the pilot selects one of the pseudo approach and landing modes, the integrations are started from this initial position.
HUD RADAR GUIDANCE SYSTEM - Fig.13 and 14 present the changes to the HUD configuration shown in Fig. 6 for the addition of the Radar Guidance System. The Radar Guidance System is being developed to achieve high precision landing suitable for category II or Ill. The Radar Guidance System has precision comparable to the Micro Wave Landing Sys-
