When flying in cruise altitude and then descending, does the plane at first hold its altitude while...........

Question

....... decreasing the speed to descent speed, and then go down, or do they go at the top of descent point immediately down and decrease their speed even while descending?

Answer 1

It all depends on the preferences of the pilot, or the operating characteristics of the aircraft, and the situation.

  I'm going to assume you mean an airliner beginning its descent for an approach.  

The pilot will decrease the throttle setting, to allow the aircraft to slow to a prescibed descent airspeed for that particular aircraft.  Flap, spoiler, etc... settings will be adjusted as well.   When the aircraft reaches the desired airspeed, the pilot will pitch the aircraft to keep that speed constant.  If the airspeed is too slow, the pilot will pitch down to increase it, and vice versa. (Assuming the pilot was actually doing the flying, instead of the Autopilot.)

With experience and predictable performance, some pilots will pitch down to a particular degree of pitch, and decrease the throttle setting at the same time, simply because they know exactly what the end result will be, after the aircraft resumes equilibrium.

Hope that helps!

Answer 2

You obtain the speed you want to descend at before you begin the descent.

1. To do a descent from high level cruise, you usually descend at or near cruise speed. Simply reduce power to achieve the desired rate of descent. Airspeed will remain constant.

2. If you need to descend in preparation to enter a traffic pattern (or have other reasons to reduce speed), the protocol is to reduce power while simultaneously adjusting the attitude of the aircraft (bleeding off speed to maintain altitude) until the desired airspeed is obtained. You then trim the aircraft and allow the descent to begin (stop holding the airplane in level flight), as you continue to reduce power the aircraft will descend.

Answer 3

Decrease power first, and then let the airplane slow down to the correct speed for descent.  On jet airliners in commercial service, the descent speed may not be much slower than cruise speed.

Answer 4

Keep the speed up.

Answer 5

Typically, one reduces power. Contrary to what most people think, reducing the power doesn't usually make the plane slow down. It makes the plane start descending at about the same airspeed it was going before you reduced the power.

The rule I learned while learning to fly is PAT: Power-Attitude-Trim. First reduce the power depending on the descent rate you want. Then adjust the attitude (angle of the plane relative to the airflow) to get the speed you want. Finally adjust the trim so the plane holds that attitude without you having to hold pressure on the stick or yoke.