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Overshooting/Undershoot on final

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Chao created the topic: Overshooting/Undershoot on final

Hi Bob or other experts,

Just wanna ask a question about overshooting and undershooting on final approach.

Recently, I was doing the circuits, which were either too high and too fast on final approach(most time) or too low. The book(Flying Training Manual from Aviation Theory Centre) that i am reading suggests that Undershooting: to correct, add power and raise the noise; Overshooting: to correct, reduce power and lower the noise, or increase flap and lower the noise.

I am starting confused with books and real fly: if undershooting, can i only add power without manually raise the nose? since increasing power will cause the nose pitching up? Same to overshooting, can i only reduce power without manually lower the nose? since reducing power will cause the nose dropping? I mean only change the power and let attitude change itself without actually change it by manual?

Thanks
Chao
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bobtait replied the topic: Overshooting/Undershoot on final

Firstly, you should consult your flying instructor for techniques to use to control the final approach. If your approaches are consistently either too high or too low, you need to have a conversation with him/her. I can, however offer the following for your consideration.

The most important consideration on final is to establish a stable approach. This requires that the final approach commences at a particular height (about 500ft for VFR aircraft) and at a particular place (distance from the threshold) and at a particular power and flap setting (Oh yes - and don't forget wheels down!). Trying to control the descent profile on final with power alone would almost certainly lead to an unstable approach with frequent variations in both airspeed and altitude. There are two methods I have seen used in general aviation.

The first was once almost universally taught but has now been largely replaced by the second.

The first method was to control nose attitude (therefore airspeed) with elevator and control rate of descent (therefore touch-down point) with power. Using this method, if the airspeed was below the required value, the pilot made a small change to a lower nose attitude to restore the airspeed. If it became obvious that the touch-down point was falling short of the runway, the pilot made a small change to power while maintaining the required constant airspeed with nose attitude. This method quickly lead to a stable approach with a fairly steady airspeed (nose attitude) and power setting (touch-down point).

The second method is to establish the aircraft at the commencement of final at the appropriate height, distance from the threshold and configuration. The desired touch-down point is then fixed at a particular point in the wind-screen using elevator. While maintaining that position for the desired touch-down point constant, the airspeed is controlled by the application of power (too fast, reduce power - too slow increase power). This method also leads to a stable approach.
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Chao replied the topic: Overshooting/Undershoot on final

Thank you very much; it’s quite clear to me now.
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