Effects of controls – it’s all about situational awareness.
Situation awareness is what was, what is and what will be 

We will be looking at two areas:
What is –  why things are happening now.
And the big one which is:
What will happen – by anticipating stuff you can avoid common mistakes; by avoiding common mistakes you have more time to enjoy your flight

This lesson is all about introducing situational awareness.

It is easy to fly precisely if you know what’s going to happen next

The upshot is this lesson is all about anticipation

If you can avoid problems then you don’t have to waste time fixing them

Objective

To operate the primary control surfaces and to experience the feel and observe the first aerodynamic effect on the aeroplane in flight.

To operate the primary control surfaces and observe the further (or secondary) aerodynamic effects on the aeroplane in flight.

To operate the ancillary controls and to experience the feel and observe the effect on the aeroplane in flight.

Primary Controls

 

• Flight path of aircraft resolved into three planes of movement
  
  • Pitching = lateral axis 
  • Rolling = longitudinal axis 
  • Yawing = normal axis 

Understand how the aeroplane is controlled on the ground (see Taxiing lesson). Speed is controlled by the hand operated throttle and the main wheel-brakes, while direction is controlled by the use of the pedals linked to the steerable nose wheel.

Have an understanding of how to hold the aeroplane’s controls and the concept of dual controls. Identify on your aeroplane which controls are dual, and which are not.

Understand how lift is produced, with reference to Bernoulli, in the simplest possible terms. For example, if the speed of the airflow is increased the pressure will be reduced and the effectiveness increased, and vice-versa.

Grasp the three axes of the aeroplane – lateral, longitudinal and normal (sometimes termed vertical) – and the movement about those axes (use teaching aids).

Learn how deflection of the controls changes the shape and/or angle of attack, affecting lift and producing the first aerodynamic effect. Start with the elevator, as this is the easiest to comprehend. Then cover the ailerons and the rudder. If you have difficulty understanding Bernoulli, angle of attack or pressure, think of it as the movement of the controls deflects the airflow and the tail is pushed up or down as applicable (Newton’s third law)

The effect of moving the elevator is to change the pitch of aeroplane. This changes the position of the aeroplane’s nose in relation to the horizon – the aeroplane’s attitude – and will consequently affect the aeroplane’s speed.

The effect of moving the ailerons is to roll the aeroplane. This banks the aeroplane left or right.

The effect of moving the rudder is to yaw the aeroplane. This moves the aeroplane’s nose left or right.

Slipstream can be described as the spiral column of air being forced back by the propeller and the primary controls. It should be noted that slipstream is present whenever the propeller is rotating, regardless of the aeroplane’s speed. The comparison of standing behind the aeroplane, compared with standing at the wingtip, may help you visualise the effect of this airflow. This highlights that ailerons are unaffected by slipstream; whereas rudder and elevator are. 

The rotational nature of the slipstream and its resultant impact on the tail fin should be understood. As the aeroplane spends most of its time in cruise, the manufacturer offsets the tail fin, or the thrust line, to negate the resultant yawing tendency. Therefore, at any power setting other than normal cruise, and at any time the power changes, the aeroplane will want to yaw, and compensating rudder inputs are required.

Function of the Primary Controls

 Controlled in planes of movement by using control surfaces

• • Elevators = pitch 
  • Ailerons = roll
  • Rudder = yaw 
• Planes of movement fixed relative to aircraft and pilot 

Rolling

Demonstrate using the model that once tilted, vertical component of lift will be reduced. This will cause a resulting slip in the direction of the turn. Air then pushes on the tail plane, yawing the nose into the turn

Yawing

We use the rudder pedals to Yaw the aircraft, this causes the nose to rotate left and right around the normal axis.

When we yaw, due to the inertia of the aircraft we will skid, (drift) which results in shielding on the inner wing, decreasing lift.

Also, the speed of the outer wing will be increased, causing more lift. These effects will cause the aircraft to roll.

Further Effects of Ailerons and Rudder

Further Effects of Ailerons and Rudder 

• Secondary effect of aileron = yaw 
• Secondary effect of rudder = bank 

Effect of Bank

Effect of Bank

• Bank applied -> sideslip towards lower wing 
• Due to sideslip -> sideways pressure of air upon keel surface of fuselage behind centre of gravity -> yaw aircraft into direction of slip 
• Degree of yaw -> angle of slip + relative area of keel surface
• Another effect of yaw -> yaws slightly in opposite direction to that of intended turn = aileron drag 
• Aileron counteracted by having Frise ailerons -> edge of up going aileron protrude more into airflow -> produces more drag 
• Results in equal amount of drag from both up going and down going ailerons 
• Will still have adverse yaw
  
  • Aircraft rolls -> lift on down going wing wing are inclined forward, up going wing inclined backwards 
  • Result of two vectors = yawing moment opposite of direction of turn 

Effect of Yaw

Effect of Yaw 

• Yawed by rudder -> tend to bank 
• Outer wing obtained more lift than inner wing
  
  • Differential in speed of airflow over both wings 
  • Effect of dihedral + methods used for lateral stability -> small increase angle of attack on outer win 
  • Minor masking of the airflow 
• Together these effects are pronounced -> aircraft adopt banking attitude 

Effect of Inertia

Effect of Inertia 

• Like other masses -> aircraft has inertia 
• Tries to continue on original path -> even when controls operated to change the path 
• When controls are moved -> lapse in time, even after attitude change, before flight path changes 
• Lag will vary with size of aircraft
  
  • Negligible in training aircraft -> more pronounced in heavier/faster types 

Airspeed

 

Look at the effect of airspeed on the feel of the controls, the aeroplane response rate, and the amount of movement needed to change the flight path. Commonly, the analogy of holding your hand out the car window and moving it from horizontal to vertical at various speeds is used to describe this effect.

At low airspeeds, typically with a high nose attitude, the controls are easy to move, are less effective and require large movements to bring about a change of flight path. They feel sloppy.

At high airspeeds, typically with a low nose attitude, the controls are harder to move, very effective and require only small movements to bring about a change of flight path. They feel firm.

Effect of Airspeed

Effect of Airspeed 

• Effectiveness of controls -> depends on speed of airflow over control surface 
• Greater airspeed = more effective controls
  
  • Controls tend to be firm + heavy 
• Lower airspeeds = less effective controls 
• Controls tend to be light + sloppy 
• Rudder -> ineffective below the landing speed 

Effect of Slipstream

Effect of Slipstream 

• Increases effective airflow over control surfaces it envelopes -> usually rudder + elevator
  
  • Throttling back -> reduces effectiveness of these controls 
• Ailerons -> outside area of slipstream influence
  
  • Remains unaffected by changes in throttle setting 
  • Most pronounced when entering climb or glide from level flight 
• Spiral path of the slipstream -> creates an angle of attack
  
  • Produces a sideways component -> yaws the tail 
  • This will vary with both RPM and airspeed 
  • Lower airspeed -> tighter coils of slipstream -> reduced directional stability = yaw more pronounced 
  • Higher airspeed -> coils become elongated -> more directional stability = yaw less pronounced 
  • Normal flight operations -> largest yaw effect is in the climb 

Effects of Trimming Controls

Effects of Trimming Controls

• Trimming = designed to relieve pilot of sustained loading of flying controls 
• Correct method is
  
  • Select attitude using primary flying controls 
  • Adjust the trimmer until no pressure is needed on control columns or rudder pedals 
• Changes in trimmer position -> required after changes in
  
  • Power 
  • Speed 
  • Flap setting 
  • Variation in load 
• Trim controls are a great help -> but are sensitive and powerful -> we should be used carefully
  
  • Mishandling -> reduced aircraft performance -> caused undue stress loads on airframe 

Effects of Flaps

Effects of Flaps

• Flaps -> designed to vary lift and/or drag
  
  • Increasing lift -> flaps reduce stalling speed and enable aircraft to fly safer at lower airspeeds 
  • Increasing drag -> flaps make it necessary to glide at a steeper angle to maintain a given speed 
• Initial application of flap -> increase lift without much increase in drag
  
  • Setting reached -> increase of more flap will increase drag with little increase in light 
  • Increase in drag -> proportion to amount of flap lowered 
  • No appreciable increase in lift will occur after flap angles of 60 degrees have been reached 
• Largest change in attitude -> within first 20 degrees of flap
  
  • Nose up or down -> dependent on aircraft type 
• Max speeds of operation of flaps -> given in the Flight Manual
  
  • In modern aircraft -> displayed on air speed indicator as top of the white arc 
  • Imposed to avoid stresses on aircraft and flap operating mechanism 

Power

 

With an increase in power the aeroplane will pitch up and the nose will yaw to the left. This is due to the corkscrewing air being pushed backwards and going over the rudder and elevator controls. Reducing power will result in a pitch down and yaw to the right. 

Therefore, whenever the power is changed, the pitch and yaw must be compensated for in order to maintain the attitude.

Slipstream

The effect of slipstream over the elevators and rudder, in relation to high power and idle power settings, at a constant airspeed should be looked at and understood. 

At high power the slipstream is increased, and the elevator and rudder are more effective; conversely, at idle power they are less effective. 

Because the ailerons are situated outside the slipstream their effectiveness does not change with increasing or decreasing slipstream. On some aeroplanes the elevator may be out of the slipstream because of its height, for example the Piper Tomahawk which has a T tail with a high up elevator. 

 

Operation of the Mixture Control

Operation of the Mixture Control 

• Mixture is used for following basic purposes
  
  • Shut down engine on completion of each flight, and to shut down engine as a specific emergency procedure during flight 
  • Achieve fuel economy during flight 
  • Maintain correct fuel/air ratio when aircraft is climbing above 5000 ft 

Operation of the Carb Heat Control

Operation of the Carb Heat Control

• Purpose of carb heat control -> avoid protection from ice forming in carburetor and to remove ice should it form 
• Heat is applied -> drop in power due to lower density of hot air 
• Hot Air should not be selected when aircraft is on ground -> hot air selected is bypass and dust particles will be ingested into the engine -> causing unnecessary wear to moving parts 

Cabin Heating and Ventilation Controls:

Cabin Heating and Ventilation Controls:

• Heat exchangers which supply heated cabin air -> normally heated by engine exhaust gases
  
  • Any cracks to the heat exchanger or associated pipes -> lead to carbon monoxide fumes entering cabin -> lethal to the pilot 
  • Because of this -> cabin cold air ventilation should be used in conjunction with cabin heating system 

Flap

Flaps (generally located at the inboard and rear section of the wings) are used to lower the minimum speed at which the aircraft can be safely flown, and to also increase the angle of descent for landing, giving you a better forward visibility. 

When flap is lowered, lift and drag are increased, which causes the nose to pitch. The opposite effect will occur when flap is raised. The change in lift can be felt and the changes in drag can be seen as an airspeed change. 

Any change in pitch or flap will require a change in the trim.