Theory Lesson Overview

Learning Objectives for this lesson

By the end of this lesson, our aim is to be able to:

• Identify three ancillary controls of the aeroplane such as throttle, flaps and trim
• Describe the purpose and operation of those ancillary controls
• Explain how power and the propeller's slipstream change the effectiveness of each main control

And then later in our actual flight:

• Experiment (safely!) with the controls in the aeroplane — applying trim and flaps to see their effects, as well as testing the effectiveness of the controls at different speeds.

Waypoint 1 — On the Sim with Flap and Trim

On the Sim with Flap and Trim — and ancillary controls

First, settle in and play with the main controls, ensuring that each does what you expect (or not!) to control the aeroplane.

Use the control column and pedals to discover and demonstrate how you can:

• control the elevator to pitch the aeroplane around the lateral axis
• control the ailerons to roll the aeroplane around the longitudinal axis
• control the rudder to yaw the aeroplane around the normal axis

You'll also discover that:

• The controls have a natural sense: Rotating the control column right rolls the aeroplane right — the movement matches the intended result — except when you're taxiing!
• The pedals don't just control the rudder, they also control the nose-wheel, so we'll be using those to control our direction while taxiing on the ground.

Ancillary Controls: Flaps

Purpose: Increase lift at lower speed; also increase drag (changes wing camber)

Full flap adds much more drag than lift — useful for a steeper approach or slowing down when landing, but not for maximising lift.

Ancillary Controls: Flaps — cont.

Key points:

• Flap "up" or "retracted" means flush with the wing — flap does not extend above the wing surface
• Deploying flap typically causes a pitch change — direction depends on aircraft type (high-wing tends nose up; low-wing tends nose down) — re-trim after each change
• White arc on ASI = flap operating range () — do not extend flaps above this speed
• Raising flap suddenly at low speed causes a sink — always retract progressively

Ancillary Controls: Trim

After being shown where the trim wheel is, see if you can spot it moving on the simulator or plane as you manipulate it (it may be harder to spot than the flaps).

Purpose: When flying it relieves control pressure — rather than having to keep pulling or pushing the control column while flying, we can adjust the trim to take away that pressure.

Technique: trim in the direction of the load you are holding. That is:

• if you are having to push the control column forward to maintain level flight, then roll the trim-wheel forward to relieve that pressure.
• if you having to pull the control column back to maintain level flight, then roll the trim-wheel back to relieve that pressure.

Important: the trim will need to be re-set (adjusted) after changing the aeroplane's power or attitude. Don't use the trim to try to change the pitch.

Waypoint 2 — Effects of Power & Slipstream

Slipstream and Power Effects

What is the slipstream?

Question: How does the aeroplane move forward when you apply power?

Slipstream and Power Effects

What is the slipstream?

Question: How does the aeroplane move forward when you apply power?

The propeller pushes the air from in front to behind the plane to move the plane forward.

But in doing so, it creates a Slipstream — a spiral column of air driven back by the propeller.

This slipstream has two noticeable effects. Can you guess from the diagram what they might be?

Effects of the slipstream

The slipstream has two noticeable effects on the aeroplane controls, mainly when using high or full power:

1. The slipstream spirals around the fuselage to "hit" the vertical stabilizer, pushing the tail to the right and causing the aeroplane to yaw to the left. This may need to be corrected by applying right rudder, especially during take-off when the power is at a maximum.
2. The slipstream causes a stronger airflow over the tail of the plane, including the elevator and rudder, but not the ailerons.

Effects of the slipstream

The effectiveness of all the control surfaces increases with the airspeed of the aeroplane, since that means airflow over all controls. But additionally, the rudder and elevator effectiveness increases with high power (even without high airspeed) whereas the aileron doesn't.

Control feel on ailerons does not change with power — as the ailerons sit outside the slipstream. The control effectiveness of the ailerons is affected by airspeed only.

Slipstream and Power Effects — cont.

• Slipstream strikes the left side of the vertical fin → yawing left at high power.
• Adding or removing power (Throttle) affects the pitch of the plane.

Power change effects:

Go-around: Full power + slow speed + nose up = maximum left yaw tendency — anticipate with right rudder.

Waypoint 3 — Recap

Lesson Summary

The Effects of the Aeroplane Controls:

First a re-cap of the main controls and their effects:

And the new learning — Ancillary controls:

• Trim — relieves control pressure; technique: trim in the direction of the load you are holding
• Flaps — increase lift at lower speed; increase drag; cause pitch change; re-trim after each selection

Lesson Summary — cont.

Slipstream and power:

• Ailerons are outside the slipstream — unaffected by power changes
• High power → left yaw tendency → right rudder required
• Go-around: anticipate strong left yaw with right rudder

Inertia: The aircraft has mass — all speed and direction changes are gradual. Anticipate.

Objectives check

At the start of the lesson, we set out to be able to:

• Identify three ancillary controls of the aeroplane
• Explain how power and the propeller's slipstream change the effectiveness of each main control
• Describe the purpose and operation of the ancillary controls — throttle, trim and flaps

Arrival

Questions?

Any further questions that we haven't yet asked or addressed?