A Summary of NASA/FAA Experiments Concerning Helicopter IFR Airworthiness Criteria

Abstract

A sequence of ground-and flight-simulation experiments was conducled at the Ames Research Center as part of a joint NASA/FAA program to investiyate helicopter instrument-flieht-rules (IFR) airworthiness criteria. This paper describes the first six of these experiments and summarizes major results. Five of the experiments were conducled a n large-amplitude motion base simulators at Ames Research Center; the NASA-Army V/STOLAND UH-IH variable-stability helicopter was used in the flight experiment. Among the results shown for instrument operations are a requirement for some level of artificial stability and control, the adequacy of neutral longitudinal control position gradients, a limited advantage of including flight directors in the display, and the necessity for pitch and roll altitude stabilization to achieve ratings of satisfactory for the approach tasks considered.

Ground-simulation investigation of VTOL airworthiness criteria for terminal area operations

“…This result is in fact consistent with the helicopter IFR results discussed in Ref. 5; as with the helicopter experiments, the addition of an attitude-augmented SCAS provided enhanced speed control and reduced excitations from other inputs, so that the ratings moved more toward the satisfactory region. With the 60-to 90-deg nacelleangle part of the conversion performed on the glide slope (profile B), the ratings with the rate SCAS degraded considerably to the point where adequate performance was just attainable.…”

“…In the helicopter instrument-flight-rules (IRF) airworthiness investigations summarized in Ref. 5, it was found that attitude augmentation in pitch and roll was necessary to achieve pilot ratings in the satisfactory category. At least this level of augmentation has also been found necessary for VTOL instrument approaches including a conversion.…”

“…GUIDANCE configuration-specific flying qualities, but the 90-deg/ 60-knot condition was considered to be more typical, and this approach speed corresponds to that used in a previously conducted investigation of helicopter terminal-area operations. 5 On this basis, the three conversion procedures, designated profiles A-C, were selected. In profile A, the entire conversion to a 60-knot speed with the thrust vector vertical (90 deg) was made before acquiring the glide slope.…”