AVAT11001: Course Outline

1. Aircraft and Terminology2. Radio Communications3. Structure, Propulsion, Fuel Systems4. Electrical, Hydraulic Systems and Instruments5. Air Law6. Aerodynamics: Basics7. Aerodynamics: Performance8. Human Factors9. Meteorology10.Loading11.Take-off and Landing Performance12.Navigation

Stuff to read

• Required Reading: BAK Chapter 6, pp. 196-228

Questions from the Reading

1. How does a pilot enter a climb?

2. What causes stall?

3. Why must the pilot not use the ailerons during the stall recovery?

4. What is a steep turn?

5. Why is it generally unwise to close the throttle before commencing the landing flare?

Climbing

• If you wish to gain altitude, you should:– Increase power

• A climb at a given airspeed requires more thrust than level flight at the same airspeed

– Increase attitude• When thrust is increased it can have 2 effects: it will increase

airspeed and/or it will increase altitude. You can use the pitch attitude to hold a given airspeed and let the thrust increase altitude

– Trim• Once you are established at the airspeed and climb rate you

desire, you can use the trim controls to relieve the amount of force you need to apply to the control yoke

The Physics of Climbs

• Forces– See Figure 6-61 page 197– During a steady climb, the forces are balanced (they sum to

zero)• Velocity is constant, it just contains an upward component• Potential energy is increasing, this requires power

• Power– See Figure 6-65 page 199– Power is thrust multiplied by velocity– Power can be used to change the energy of the vehicle

• It can be used to increase the kinetic energy (= ½mv2) by increasing velocity

• It can be used to increase the potential energy (= mgh) by increasing altitude

Airspeed

• There are different airspeeds used for climbing• See Figure 6-60 page 196 and Figure 6-65 page

199– Vx, the best climb angle speed

• This speed occurs when you have the most excess thrust.• You get the most altitude gain for the least horizontal

distance covered• If thrust is much greater than weight, you can climb vertically

(no horizontal distanced covered)

– Vy, the best climb rate speed• This speed occurs when you have the most excess power• You get the most altitude gain in the least amount of time

Descent

• If you wish to lose altitude, you should:– Decrease power

• A descent at a given airspeed requires less thrust than level flight at the same airspeed

– Decrease attitude• When thrust is decreased it can have 2 effects: it will

decrease airspeed and/or it will decrease altitude. You can use the pitch attitude to hold a given airspeed and let the thrust decrease altitude

– Trim• Once you are established at the airspeed and descent rate

you desire, you can use the trim controls to relieve the amount of force you need to apply to the control yoke

The Physics of Descents

• Forces– See Figure 6-69 page 201– During a steady descent, the forces are balanced (they sum to

zero)• Velocity is constant, it just contains a downward component• Potential energy is decreasing

• Power– The power required for a descent is less than the power required

for level flight– This is not shown on the power required figure, but you can

understand that it takes no power for a rock to fall from the sky.– As you descend, you must be careful to not let your speed

become too great• The potential energy lost by descending will be converted into

kinetic energy unless you take action to balance the forces

Turns

• To cause an object to turn, a force must be applied perpendicular to the velocity of the object

• Think of a ball on a string– To swing the ball in a circle, the

string needs to apply a force in towards the centre of the circle

• For aircraft, this force is supplied by banking the wings and using a horizontal component of the lift force– See Figure 6-76 page 205

velocity

desiredpath

forcerequiredto turn

velocity

forcerequiredto turn

Steep Turns

• Turns are classified by the amount of bank angle used– Medium level turn: level flight with a 20° to 30° bank angle– Climbing turn: during a steady climb, keep the bank angle 15° or

less to maintain the climb rate– Descending turn: keep the bank angle 30° or less to avoid high

descent rates– Gliding turn: keep the bank angle less than about 30°– Steep turn: a turn of 45° or more– Maximum rate turn: a turn which will change your heading as

quickly as possible. Only used in emergency situations, like collision avoidance

• The greater the bank angle, the more difficult it is to maintain level flight in a turn– See Figure 6-88 page 215

Stalls

• Stalls occur when the angle of attack exceeds the critical stall angle– See Figure 6-21 page 179

• Most aerofoils have the property that the lift coefficient, CL, increases as the angle of attack increases.

• Eventually, the airflow over the top of the aerofoil will separate and lift will be lost.

• This will occur at a specific angle of attack that is a function of the shape of the aerofoil

Stall Speed

• The speed at which a stall will occur is a function of many variables– Weight– Load Factor– Bank Angle– Power– Flap Setting

• When stall speeds are calculated for aircraft operating manuals they often assume the worst case to produce conservative numbers– Often you can fly below the listed stall speed without stalling.

Especially if you have power on and are below the maximum weight

– You may still manage to stall the aircraft above the listed stall speeds. Especially if you have a high load factor (i.e. during a steep level turn)

Spins

• Spins are complex aircraft motions in which all of the following occur:– Rolling– Yawing– Pitching– Slipping– Rapid descent

• They are usually caused when one wing stalls before the other

• To recover from a spin:– Centre the controls– Close the throttle– Apply full rudder opposite to the direction of the yaw– Apply forward pressure until the rotation stops– Recover from the dive (gentle aft pressure on the control yoke)

Spiral Dives

• Spiral dives occur when the aircraft begins to bank. If you bank the aircraft and make no power or pitch changes, you will begin to descend. As the descent begins, the aircraft speeds up and the turn tightens.

• Spiral dives are very different from spins– Spiral dives begin slowly, usually starting from high speeds– Spins begin suddenly, usually starting from slow speeds

• To recover from a spiral dive, roll the wings level– The danger of the spiral dive comes from a pilot noting a high

descent rate and pulling back on the controls. This only tightens the dive and makes things worse if you do not level your wings first.

For next week…

• Required Reading: BAK Chapter 8, pp. 247-284