Helicopter Unique Instrument Approaches: Trajectories, Flying Qualities, Controls and Displays

The paper presents an argument for combining the precision of GPS with robust slow speed agility of the helicopter to support the wide implementation of a helicopter precision track GPS (HPT-GPS) instrument approach. The autonomous nature of the approach suggests that it is particularly suited for use at small airports and heliports. This capability is then characterized as providing an affordable way to facilitate the integration of rotorcraft Into the National Airspace System to facilitate commerce and Emergency Medical Service (EMS) to areas that are otherwise poorly served by aviation during poor weather. The paper defines a new minimum approach airspeed (V_MAP) which applies to the last segment of the approach. This segment involves a descent to a Minimum Descent Altitude (MDA) and continued flight to a Helicopter Visual Descent Point (HVDP) which is expected to be located 150 feet or more above or beyond the runway threshold. A series of charts is used to explain the relationship between V_MAP and the current minimum airspeed for instrument flight (v_MlNl). Tne paper concludes with a justification for displaying both ground speed and airspeed and suggests formats for both. This includes a examination of the need to extend the useful range of the airspeed system down to 20 Knots Calibrated Airspeed (KCAS) to facilitate a safe operating margin below a V_MAP of 30 KCAS.