Descents and descending turns are basic flight maneuvers used to reduce altitude while maintaining appropriate airspeed, airplane control, and coordination. Pilots must understand how pitch attitude, power settings, drag, and flight instrument indications affect descent performance. Proper control of these factors helps establish a stable descent and prepare the airplane for the next phase of flight.
When an airplane enters a descent, its attitude changes from level flight to a descending flight path. [Figure 1] During a descent, weight has a component acting along the flight path, contributing to the airplane’s motion. As lift requirements and induced drag decrease, the airplane may accelerate if the power setting and pitch attitude are not adjusted.
To maintain the desired airspeed and descent rate, the pilot must use appropriate pitch and power settings to balance the forces acting on the airplane.
The pilot should know the engine power settings, natural-horizon pitch attitudes, and flight instrument indications that produce the following types of descents:
- Partial-power descent — The normal method of losing altitude is to descend with partial power. This is often termed a cruise or en route descent. The airspeed and power setting recommended by the AFM/POH for a prolonged descent should be used. A target descent rate of 500 feet per minute (fpm) may be used where appropriate. The desired airspeed, pitch attitude, and power combination should be selected and maintained.
- Descent at minimum safe airspeed — This is a nose-high, power-assisted descent condition used principally when clearing obstacles during a landing approach to a short runway. The airspeed for this descent condition should follow the AFM/POH recommendations and is normally no greater than 1.3 VSO. Characteristics of a minimum-safe-airspeed descent include a steeper-than-normal descent angle. Sufficient power may be required to prevent the airplane from mushing or developing an excessive rate of descent at low airspeed.
- Emergency descent — Some airplanes have a specific procedure for rapidly losing altitude. The AFM/POH specifies the appropriate procedure. In general, emergency descents are high-drag, high-airspeed maneuvers requiring a specific airplane configuration, such as power set to idle, the propeller controls positioned as specified, the landing gear extended if required, and the flaps retracted if specified. The procedure also specifies the appropriate emergency descent airspeed. Emergency descent maneuvers often include turns.