Block 2

Question 1

Identify the different types of engine.

Answer 1

Piston, Jet (turbojet and turbofan) and Turboprop

Question 2

Describe piston engines

Answer 2

Similar to an internal combustion engine. Engine drives a propeller. Can be air or liquid cooled. Two kinds radial (odd number of pistons) and horizontally opposed (even number of pistons). Disadvantages: many complex parts and greater weight ratio (the engine’s weight as a ratio to the entire weight of the aircraft). Operates efficiently up to around 12,000’.

Question 3

Describe jet engines (turbojets)

Answer 3

Two types: turbojet and turbofan. Turbojets take in air, compress it and force it into the combustion chamber where it is mixed with fuel injected at high pressure. The fuel-air mixture ignites and the expansion of high pressure gases through the turbine nozzles drives the turbine. At lower altitudes higher air density requires more fuel to acheive the correct fuel-to-air ratio. At higher altitudes less power is produced in the thinner air, however the reduced drag makes high altitude operations more economical. Max efficiency around 36,000’. Advantages include few moving and intricate parts, reduced drag (no prop, small frontal area) and good power to weight ratio. Disadvantages: consume excessive fuel at low altitude, slow to respond to application of power. Examples include the DC8, B707, and most military jet fighters.

Question 4

Describe jet engines (turbofans)

Answer 4

Turbofan is an improved version of the turbojet. It uses a fan ahead of the engine to accelerate air. The extra power is available for better take-off, climb and cruise performance, reduced fuel consumption and better payload/range. Operates best between 33000’ and 37000’. Turbofans are more fuel efficient, quieter, have better low altitude performance and lower landing speeds than turbojet engines. Found on most commercial and executive jets eg Airbus 320, C550 (citation two) B767.

Question 5

Describe turboprop engines

Answer 5

Combines the properties of the propeller and jet engines. Turbines constructed to drive propellers. Most of the energy of the heated gas is used by the turbine to drive the propeller with only a small amount creating thrust at the exhaust. About 90-95% of power from propeller, about 5-10% from thrust. Turboprops operate most efficiently between 13,000’ and 25,000’ ( trade off between the prop more efficient at lower altitudes, engine more efficient at higher altitudes. Lower engine-weight ratio than props however cannot operate at as high an altitude as a turbojet. Most common in commuter passenger ( eg DH8B, BE9L) or business aircraft (eg PAY2, MU2)

Question 6

Describe the performance charateristics of the different types of engine: altitudes

Answer 6

Piston: 0’ - 12,000’
Turboprop: 13,000’ - 25,000’
Jet: 25,000’ +

Turbo charged piston craft may reach 25,000’ causing problems as slow moving piston mix with fater jet and turbo-props. Modern turboprop may reach as high as 29,000’, causing problems as they mix with faster jet engines.

Question 7

Describe the performance charateristics of the different types of engine: speed

Answer 7

Piston: <250 KT (modern general aviation eg C172 maintain speeds between 100 and 120 KT)
Turboprop: 200 - 300 KT
Jet: 300 - 500 KT

Question 8

Describe the performance charateristics of the different types of engine: climb rate

Answer 8

Piston: 500 - 1500 FPM
Turboprop: 1500 - 3000 FPM
Jet: 1500 - 6000 FPM

There is a large discrepancy in climb performance of jet engine aircraft. Commercial airliners cannot/will not climb at more than 2000 - 3000 FPM. eg a heavily loaded 747 on a hot day may only climb at 1000 FPM. On the other hand many excecutive jets can climb at 3000 - 6000 FPM. The rate of climb will also vary - the aircraft will normally reach the max rate of climb in the first 5000’ before decreasing to the max altitude.

Question 9

Describe the performance charateristics of the different types of engine: rate of descent

Answer 9

Piston: 500 - 1500 FPM
Turboprop: 1500 - 4000 FPM
Jet: 2000 - 6000 FPM

Descent performance will vary somewhat based on high/lower performance aircraft and with altitude (jet aircraft will descend quicker at high altitudes, slowing their descent as they approach lower altitudes.

Question 10

Describe the performance charateristics of the different types of engine: turns

Answer 10

Piston: Rate 1 (3 deg/s)
Turboprop: Rate 1 (3 deg/s)
Jet: Rate 1/2 (1.5 deg/s)

Turn radius depends on rate of turn and airspeed. ie jet engines have the largest turning radius.

Question 11

Describe the performance charateristics of the different types of engine: run up

Answer 11

Piston: Long (the more engines on the aircraft the longer run-up time. Normally checks are done in the holding bay or taxiway)
Turboprop: Short (checks can usually be carried out with the aircraft is taxiing)
Jet: None (checks can quickly be performed during taxi)

Question 12

Describe the performance charateristics of the different types of engine: acceleration

Answer 12

Piston: No delay
Turboprop: Slight delay
Jet: Long delay

Plan sufficient time for larger aircraft to comply with ATC instructions.

Question 13

Describe the performance charateristics of the different types of engine: economy

Answer 13

Piston: Efficient at low altituded (<12,000’)
Turboprop: Efficient at normal operating altitudes, less efficient at low altitudes
Jet: ineffecient at low altitudes - minimize time spent at low altitudes.

Question 14

Describe the performance charateristics of the different types of engine: FOD (Foreign Object Damage)

Answer 14

Piston: Does not ingest
Turboprop: Does not ingest
Jet: Ingests, warn pilots of potential hazards such as slush, loose stones, birds etc.

Question 15

Describe how propeller pitch affects performance

Answer 15

The pitch is the distance the propeller travels forward in one revolution and is controlled by the angle of attack of the propeller blades. A coarse pitch (steep angle of attack) means the propeller travels a larger distance per revolution than a fine pitch (shallow angle of attack). In the real world this distance is reduced to the effective pitch with the difference being the propeller slip. A coarse pitch provides greater effective distance at a given RPM and is more efficient for cruising. A fine pitch has less drag and rotates faster giving more power for take-off and climb performance but is inefficient for cruising.

Question 16

Describe different propeller types: fixed pitch

Answer 16

Fixed pitch: compromise between coarse and fine pitch. Found on most training aircraft eg Cessna 150

Question 17

Describe different propeller types: variable pitch

Answer 17

Variable pitch: adjustable (blades may be adjusted on the ground) or controllable (may be adjusted in flight). Allows pilot to select best pitch for take-off and cruise performance.

Question 18

Describe different propeller types: constant speed

Answer 18

Constant speed: variable pitch propeller fitted with a governor. The governor alters the blade angle to maintain a constant RPM for all conditions

Question 19

Describe different propeller types: reversible pitch

Answer 19

Reversible pitch: achieved by turning the blades to the full reverse pitch so that a pushing rather than pulling is achieved. For safety this is only possible when the extended nose wheel is in contact with the ground.

Question 20

Describe different propeller types: feathering

Answer 20

Feathering: When necessary to stop an engine it is desirable to feather the engine by turning it to an extreme coarse pitch. This stops the prop from rotating, reducing drag, windmilling and reducing vibration. Used to reduce drag in the even of a lost engine or to prevent wear caused by the propeller rotating in the wind when not in use.

Question 21

Explain the use of thrust reversal by jet aircraft

Answer 21

Used to slow down jet aircraft once they have landed. Two types:

a) mechanical blockage system consists of two clamshells which when stowed are located near the rear of the jet engine. When deployed they deflect the exhaust forward, producing reverse thrust. Older B737 models use this method.
b) aerodynamic blockage system (cold stream reverser) causes the exhaust gases to redirect thrus outward and forward. Are controlled by thrust levers in the cockpit (as are mechanical blockage reversers)

Question 22

Explain the consequences of engine failure on single engine aircraft

Answer 22

The aircraft can only glide. On take-off most will proceed straight ahead for an emergency landing, if terrain is good. Turning back toward the runway is risky as stall speed increases in the turn and the plane is alread losing speed and lift because of the failed engine. Most single engine aircraft have good gliding capabilities. The outcome depends on the altitude and pilot’s abilities.

Question 23

Explain the consequences of engine failure on multi engine aircraft

Answer 23

Multi-engine aircraft can usually stay in the air, but at reduced airspeed.
During and immediately after take-off the loss of thrust reduces the ability to clear obstacles and increases the time to accelerate to climbing speed.
During take-off run the loss of engine will increase the time and distance required to take-off, requiring the pilot to decide whether there is enough runway to complete the take-off (and then clear obstacles) or enough runway remaining to stop safely.
If an engine fails while airborne the aircraft loses 50%, 33%, 25% power (2,3 and 4 engine respectively). 3 and 4 engine aircraft will usually maintain sufficient speed to successfully climb out, provided the aircraft has reached its critical speed (which depends on which engine failed). Twin engine aircraft can have serious problems (a 50% power loss is more like a 75% performance loss).
Rate of climb depends on excess horsepower. Often in a twin engine the 2nd engine provides all the excess power and it’s loss means the aircraft can barely keep the plane in the air. In cruise flight the engine loss will often force the plane to operate at a lower altitude.

Question 24

Explain asymmetrical thrust

Answer 24

The aircraft tends to yaw after losing an engine due to the unbalanced thrust of the working engine and increased drag of the non-working. The asymmetric thrust is greater when the outboard engines fail (on 4 engine aircraft) and when propellor engines fail (than jet engines, because the propeller has greater drag).
Flying on asymmetric power is difficult.
Each engine turning to the right applies forces turning the aircraft to the left. One of these forces is the “P” factor which acts on the right engine side of the prop disk. It is farther from the vertical axis for the right engine than the left. The failure of the left engine produces greater unbalanced moment and is it’s failure is more critical than that of the right engine. (The opposite is when the props turn to the left - then the critical engine is the right engine).
The airspeed at which adequate directional control can be maintained with the critical engine failed but not feathered and with full power on the right is called the critical single engine speed. Adequate directional control is maintained by applying rudder opposite to the engine that has failed. The airplane must be at it’s critical speed for this to be effective. The critical speed varies depending on which engine was lost.

Question 25

Explain pilot procedures for the event of engine failure: during take-off, not airborne

Answer 25

Abort if possible, depending on speed and length of runway remaining.
If gear is still down and enough runway remains, land straight ahead.
If unable to land straight ahead: keep straight by coarse use of rudder, gear up, feather the engine, put flaps up, lower nose to gain speed if necessary, apply additional speed to power good engine(s)

Question 26

Explain pilot procedures for the event of engine failure: while climbing or cruising

Answer 26

Attempt to find trouble (feather right away if obvious mechanical breakdown or fire)
Keep straight and level by use of rudder or putting nose down to maintaine safe speed.
Feather the propeller (if there is one)

Question 27

Explain pilot procedures for the event of engine failure: while landing

Answer 27

If able to maintain altitude: normal circuit, gear down at the last minute. SOME AIRCRAFT MAY ONLY BE ABLE TO TURN TOWARD THE GOOD ENGINE due to asymmetric thrust.
If unable to maintain altitude: adjust the patter to arrive on final with sufficient altitude.
If makes it to the runway the landing roll will be normal except there will be no reverse thrust applied to the good engine (if so equipped)

Question 28

Describe the function of the following aircraft components: Ailerons

Answer 28

Ailerons are moveable control surfaces attached to the trailing edge of the wing. The move opposite to each other and are controlled by turning the control column of the car. They change the roll.

Question 29

Describe the function of the following aircraft components: Elevators

Answer 29

Elevators are moveable control surfaces attached to the horizontal stabilizer. They are controlled by pushing/pulling on the control column. Pulling back makes the nose pitch up, pushing forward makes it pitch down.

Question 30

Describe the function of the following aircraft components: Rudders

Answer 30

The rudder is a moveable control surface on the vertical stabilizer. It controls the yaw. It is controlled by foot pedals. Pushing down on the left foot pedal makes the plane yaw left.

Question 31

Describe the function of the following aircraft components: Trim Tabls

Answer 31

Trim tabs are located on the trailing edge of the ailerons, elevators and rudders. They allow the pilot to maintain a constant attitude without applying constant pressure to the controls. They are usually controlled by turning a control wheel in the cockpit. In light aircraft, often the only trim tab is for the elevators. In large aircraft, all three control surfaces have trim control devices.

Question 32

Describe the function of the following aircraft components: Flaps

Answer 32

Flaps are control surfaces along the trailing edge of the wing and which change the shape of the wing. Their main purpose is to increase lift, improving take-off performance, allowing steeper angles on climb-out and slower speeds during approach.
They are normally divided into 3 typesk: lift (permits steeper climb-out), lift-drag (permits steeper climb and slower approach) and drag (permits slower approach). They can be set to a variety of angles.

Question 33

Describe the function of the following aircraft components: Speed Brakes Dive Breaks

Answer 33

Are found on a few high performance aircraft. They are usually incorporated into the rear of the fuselage and consist of two hinged doors that extend into the airstream to create drag.

Question 34

Describe the function of the following aircraft components: Slots and Slats

Answer 34

Slats are auxiliary airfoils fitted into the leading edge of the wing, which are deployed either manually by the pilot our automatically when the wing reaches a predetermined angle of attack.

Slots are passageways built into the wing often just behind the leading edge. Their purpose is to smooth out the flow of air over the top of the wing at high angles of attack

Question 35

Describe the function of the following aircraft components: Spoilers

Answer 35

Spoilers are fitted into the top of the wing to spoil the airflow, reducing lift. They are usually deployed after touch down during landing but may be partially extended during flight to increase the rate of descent or reduce airspeed.

Question 36

Describe the function of the following aircraft components: Boundary Layer Control Devices

Answer 36

eg Vortex Generators. Control the airflow over the boundary layer to improve wing performance.

Question 37

Describe the function of the following aircraft components: Control Locks

Answer 37

May be attached to ailerons, rudders and elevators while parked to prevent movement and damage by wind gusts. They are brightly coloured with streamers attached and must be removed during pre-flight checklist. ATS personnel must notify taxiing aircraft if they see streamers still attached.

Question 38

Describe the following types of landing gear: Conventional

Answer 38

Also called a “tail dragger” or “tail wheel”. Main carriage located ahead of the centre of gravity, and a tail wheel or skid is located at the rear. The nose of the aircraft blocks or partially blocks forward visibility during taxi. Advantage: can operate on rough strips where prop clearance is a factor. eg DHC2, PA18, C180, C185

Question 39

Describe the following types of landing gear: Tricycle

Answer 39

Main lading gear located behind the centre of gravity and the aircraft has a nose wheel. Most popular arrangement. Better visibility and ground handling. Aircraft without a retractable gear may have wheel fairings (like an aerodynamic sleeve over the wheel).

Question 40

Describe the following types of landing gear: Bicycle

Answer 40

The main landing gear is located under both the forward and rear portions of the airplane with outriggers usually located near the wing tips. Uncommon, but is used eg on the U-2, Harrier, B52. Also on many gliders and sailplanes

Question 41

Describe the following types of landing gear: Retractable

Answer 41

Landing gear configurations may be retractable to reduce drag. Most higher performance aircraft have a retractable gear.

Question 42

Describe the following types of landing gear: Skis

Answer 42

Skis can be fitted to tail wheel and tricycle fixed gear aircraft such as the C185 and DHC6. Can be either straight skis or wheels skis. When an aircraft fitted with wheel skis prepares to land other than on snow the ski is retracted so the wheel makes contact.

Question 43

Describe the following types of landing gear: floats

Answer 43

Floats can be straight floats (water only) or wheel floats (water/runway) and allow landing on water.

Question 44

Describe the following types of landing gear: Amphibious

Answer 44

Made to take off and land on both water or land. The body of the aircraft supports the aircraft on water, while a retractable gear allows the use of land based aerodromes.

Question 45

Explain the principle of operation of pressure instruments.

Answer 45

Pressure instruments detect and measure differences or changes in air pressure. These instruments are connected to a pitot and/or static vent that supplies dynamic/static air pressure.

Question 46

Describe Static Pressure

Answer 46

Static pressure is the pressure of the surrounding air at flight altitude. It tends decreases with altitude.

Question 47

Describe Dynamic Pressure

Answer 47

Air resistance increases the force on a plane in motion. The additional force is defined as dynamic pressure. It increases with the speed of the body and the density of air the body moves through. The source of this pressure is obtained from the open end of the pitot-tube which projects into the air flow.

Question 48

Describe Pitot Pressure

Answer 48

Pitot pressure is defined as the sum of static and dynamic pressure acting on a body.

Question 49

Describe possible errors of the pressure instruments.

Answer 49

Blocked openings of the pitot tube or clogged vents can cause erratic or erroneous airspeed indications. Electrically heated pitot-heads have helped overcome ice or water blocking the tube. The pitot-head may be covered while parked to prevent buildup of dust and moisture. The canvas cover must be removed before flight and if observed by ATC advise the pilot. Many aircraft have an alternative source of static pressure. They have a switch to change from the normal source to the alternative source.