British Young Pilots · Flying Training · Module FT-8.2
Going down in an aeroplane is gentle. You take a little power off, hold the nose a touch lower than level, and the aeroplane slides downhill through the air at the same speed it was flying before. Nothing dramatic happens. Picture a toy plane rolling down a gentle ramp: it does not fall, it just follows the slope.
Try it now: hold your flat hand out like a wing. Tip the fingertips down just a little. That is a descent. Point them at the floor and that is a dive, which is not what pilots do.
Source: Pooleys Vol 1 (15th ed.) p.127–128.
Exercise 8b: control the rate of descent and the flightpath with power, while holding a constant airspeed. What the aeroplane does (its performance) depends on two things together: the power set with the throttle and the attitude held with the control column. To change how steeply you descend without letting the speed wander, you adjust both. That is exactly what happens on every normal approach to land, and in a cruise descent.
The rule to memorise: attitude controls airspeed; power controls rate of descent.
Source: Pooleys Vol 1 (15th ed.) p.127 and p.130.
In a descent each hand has one job. The throttle decides how fast you go down. The control column sets the nose position (the attitude), and that decides how fast you fly forward.
Think of a bike coasting down a hill. A steeper hill is like less power: you go down faster. Leaning is like the nose attitude: it changes your speed. Pilots use the two together: less power for a steeper slope, then the nose a little lower to keep the speed the same.
Source: Pooleys Vol 1 (15th ed.) p.130.
Monitor the rate of descent on the VSI (vertical speed indicator), or on the altimeter with a clock. Then:
A power change brings a pitch and yaw tendency: balance it with rudder and column pressure. Watch the ASI while you set the new attitude.
Source: Pooleys Vol 1 (15th ed.) p.129–130.
Two dials tell you if the descent is right. The VSI shows how fast you are going down: the further its needle drops below the middle, the faster you are descending. The ASI shows how fast you are flying forward.
Class action: left hand is the VSI needle, right hand is the ASI needle. When the instructor says "add power", the left hand rises towards the middle (descending more slowly) and the right hand stays put, because the nose comes up to keep the speed the same.
Source: Pooleys Vol 1 (15th ed.) p.128–130.
Hold a constant nose attitude and find the ground feature that stays fixed in the windscreen: that is your aiming point, where the descent will meet the ground. On the approach, adjust the flightpath with power and attitude until the chosen point on the runway is the one that stays still, and act positively the moment it is not.
The cruise descent saves time at the end of a long cross-country: start down some miles out, reduce power slightly and lower the nose so the airspeed stays at the cruise figure.
STRETCHTwo aeroplanes descend at the same airspeed, one with more power. Which has the higher nose attitude, and which reaches the ground first?
Source: Pooleys Vol 1 (15th ed.) p.128–129.
If the ground is coming up too quickly, do not pull the nose up on its own. Add some power and let the nose come up a little to keep the speed. The slope gets gentler and you reach the ground further ahead. Need to get down sooner? Take some power off and hold the nose a little lower. The slope gets steeper.
Pilots have a trick for knowing where they will land: whatever spot on the ground stays still in the windscreen is where you are heading. Hold a finger on it and watch.
Source: Pooleys Vol 1 (15th ed.) p.128–130.
Even with power on, the setting is lower than normal, so engine icing remains a threat. In a prolonged descent, warm the engine periodically and use carburettor heat as required. Keep an eye on the RPM as you do.
The classic error on approach is not controlling the rate of descent enough. Decide the airspeed and rate of descent you want and take positive action to get them, while keeping a good lookout. Airmanship in this exercise means positively controlling your flightpath and airspeed.
Source: Pooleys Vol 1 (15th ed.) p.128–129.
In a glide, a component of weight acting along the flightpath does the pulling that balances drag. Apply power and the thrust now balances some of that drag, so the weight component along the flightpath does not need to be as large for the same airspeed. A smaller weight component means a shallower flightpath, hence a higher pitch attitude and a lower rate of descent than the glide at the same speed. This is why the pitch attitude for a powered descent is not as low as for the glide.
Source: Pooleys Vol 1 (15th ed.) p.127. The glide itself is module FT-8.1.
Tap a card to flip it.
One statement at a time: is it about POWER (the throttle) or ATTITUDE (the nose, set with the control column)? Tap to sort it.