[Ref RPL Instruction Kit (502) 8th Edition P. 81-84]

4 Forces in a Desent (Descending Maneuver)

  1. Lift is titled and which should still be perpendicular to the flight path through the CP.
  2. Weight acts vertically downwards toward the earth
  3. Thrust acts forward along the propeller shaft – acts forward and parallel to the flight path
  4. Drag acts to the rear parallel but opposite to the flight path

During initial of a descent, the AOA is decreased momentarily and so the total lift also decrease. With weight now being greater than lift, the aircraft begins to descend.

Concept of steady flight is suitable for descend still!

After the airspeed stabilizes, it is a steady descend, in which the forces of thrust and drag, and lift and weight again become balanced – sum of 4 forces is zero. However, in case descend, airspeed may either increase or same. To descend at the same airspeed, the power must be reduced!


Power-off descend

Power-off descend is called a “glide” – the throttle is close to idle. Or in the event of engine failure, there is no thrust provided by the engine. Glide performance becomes more significant in event of engine failure.

Glide performance

The optimum performance of a plane in a glide could help it achieve maximum glide distance for the amount of altitude lost. To do this, the airspeed should maintain at its V L/D max. Either higher or lower than the “best glide speed”, the plan cannot have its best range.



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