Aircraft Flashcards
Why do controllers need to know about ACFT performance?
Because it is essential for the provision of a safe and efficient air traffic control service. The quality of service provided is dependent on other controllers knowledge of ACFT performance
The knowledge is used to:
- Provide separation
- Decide the allocation of cruising levels
- Create approach/departure sequences
- Use speed control
- Provide wake turbulence separation
- Use other ATC techniques
REFER TO EXAMPLES IN UK ACFTB 01 BOOKLET
What is the Climb Gradient and how is it calculated?
The ratio of height gained to distance travelled expressed as a percentage.
tan(angle)=height/distance
Why is the Minimum Climb Gradient specified on Instrument Departure Procedures?
It is required to overfly the obstacles in the departure area at a safe altitude defined as Minimum Obstacle Clearance.
What is Rate of Climb?
The vertical component of the ACFTs velocity.
Rate of Turn (ROT) is constant if ____ and ____ remain constant
- ) Speed
2. ) Bank
What is the ICAO standard turn and what is it used for?
- 3 degrees per second but MAX 25 degrees of bank.
- It is used for Instrument flight procedures e.g. holding
- Required angle of bank can be calculated by (TAS/10) +7
What is an ICAO ACFT type designator?
- A unique designator assigned by ICAO to each type/series of ACFT.
- MAX of 4 alphanumeric characters.
- Intended to be used in flight plans and ATS Messages.
- E.g. Airbus A320 = A320 and Boeing 737-300 = B733
- ICAO Doc 8643
What is an ICAO ACFT type descriptor?
- 3 character code which describes an ACFT.
- 1st character represents ACFT category.
- 2nd represents No. of engines.
- 3rd represents type of engines.
- ICAO Doc 8643
What are the 2 broad categories of ACFT?
Heavier than air and lighter than air
What are the 2 further ACFT categories within heavier than air category ?
Powered and non-powered
What are the 2 further ACFT categories within powered category?
Aeroplanes and Rotorcraft
What are the 3 further ACFT distinctions within aeroplanes category?
Land planes, Sea planes and Amphibians
What are the Wake Turbulence Categories (WTC)?
- Light - 7000kg or less
- Medium - 7000-136,000kg
- Heavy - 136,000kg or more
- For A380, the word super can be added to Heavy. Higher minima.
What are the 5 ICAO Approach categories?
1.3 times stall speed in landing config at MAX certified landing mass
A: < 91kt IAS B: 91kt ≤ IAS 121kt C: 121kt ≤ IAS < 141kt D: 141kt ≤ IAS < 166kt E: 166kt ≤ IAS < 211kt H: Helicopters (May use category A)
What are the main structural components of a fixed wing ACFT?
- Fuselage
- Empennage (tail section)
- Wings
- Powerplant (engines)
- Landing gear (undercarriage) and nose wheel
What are the main structural components of a rotorcraft?
- Fuselage
- Tail section
- Power plant
- Rotor
- Undercarriage
What are the 4 major forces acting on an ACFT?
- WEIGHT - Downward acting force which acts through the centre of gravity.
- LIFT - Upward force which must overcome the weight of the ACFT in order for it to climb.
- THRUST - Produced by the engines resulting in the ACFT moving forward either by horizontal lift (Propellers) or expanding gases pushed backwards (Jet).
- DRAG - retarding force caused by disruption of air flow by various parts of the ACFT as it moves through the air.
What happens with the 4 major forces during straight and level flight?
Weight is balanced by lift and drag is balanced by thrust.
What is the Centre of Gravity?
The point of balance, the position of which depends upon the load, mass of the ACFT and position of the individual parts of the ACFT.
What is static pressure?
Pressure measured with a gauge which is motionless with respect to the air. It acts equally in all directions and decreases with altitude.
What is dynamic pressure?
Pressure exerted as a result of the airs motion acting in the direction of the movement only. Proportional to the density of the air and the square of the speed of the air.
What is air density?
The mass per unit volume of the atmosphere. Proportional to static pressure and inversely proportional to temperature.
What is total pressure?
The sum of static and dynamic pressure.
What is an aerofoil?
A shape capable of producing lift as it passes through the air.
What is the chord line?
An imaginary line drawn from the extremity of the leading edge to the extremity of the trailing edge.
What is the angle of attack?
The angle between the chord line of an aerofoil and the remote relative airflow. Lift increases with angle of attack until the critical AoA (Just under 16 degrees) is reached where lift then diminishes and drag increases.
How is lift generated?
The velocity of the air will increase over the upper part of the aerofoil due to the increased camber resulting in a lower static pressure and higher dynamic pressure.
Vice versa on the lower part of the aerofoil.
The pressure differential between the upper and lower parts of the aerofoil creates the total reaction force which can be considered as acting through the centre of pressure.
The highest amount of lift is generated on the upper part of the aerofoil as the decrease in static pressure is larger compared with the slight increase of static pressure on the lower part of the aerofoil.
What is total drag?
The sum of parasitic and induced drag.
What is parasitic drag?
Drag experienced by an object moving through the air. It consists of skin friction drag, form drag and interference drag. It varies proportionally to the frontal area presented to the airflow. It increases with the square of the airspeed and is lowest at stalling speed and highest at MAX speed.
What is skin friction drag?
A form of parasitic drag resulting from the friction between an object and the air through which it is moving. The magnitude depends on the surface area of the ACFT and the surface condition (how rough/smooth it is). Transition from laminar to turbulent airflow may occur immediately at a rough point.
What is form drag?
A form of parasitic drag resulting from the shape of the aerofoil/ACFT. It can be reduced by streamlining (e.g wheel fairings)
What is interference drag?
A form of parasitic drag resulting from the mixing of airflow streamlines between airframe components such as the wings and fuselage.
What is induced drag?
An undesirable by-product of lift (horizontal component) which decreases with the square of airspeed. As air flows rearwards, some air with higher static pressure will leak around the wingtip to the low static pressure area a sheet of vortices forms being the ACFT - the strongest of which are at the wingtips.
How is a Wake Turbulence formed, and what factors affect its intensity? What hazards might be caused to following aircraft?
The difference in pressure between the high pressure below the wing and the low pressure above causes air to be ‘sucked’ over the outer edge of the wing.
This air forms a circular vortex trailing from each wing tip, which remains distinct in the case of larger aircraft but can join behind smaller aircraft to create an area of extreme turbulence.
The effect can be observed up to 900ft below and behind the aircraft.
The severity of the vortices is directly affected by the angle of attack of the wing: more angle= greater turbulence. Therefore the vortices are much stronger at slower speeds, such as when the plane is landing.
Adding winglets to the wing tips can greatly reduce the formation of wake vortex by creating a barrier between the high and low pressure air.
Hazards to following aircraft uncontrolled roll and spin, loss of height and climb rate and engine flameout.
Helicopters create relatively large wake turbulence for their size, and downwash also becomes an issue- especially near the ground, eg. Air taxiing.
What is aspect ratio?
Wingspan/Mean Aerodynamic Chord length. Wings with a higher aspect ratio will produce less induced drag.
What are winglets?
Wing tip devices which increase aspect ratio of the wing (with apparent extension of the wingspan) resulting in less induced drag.
What are slats?
Devices on the leading edge of wings which when deployed allow an ACFT to operate at a higher angle of attack and therefore increase lift.
Air passes through the slat on the lower part of the wing and reenergises the air on the upper part, maintaining laminar flow.
Allow ACFT to fly at slower speeds and TKOF and land in shorter distances. Usually retracted during the cruise to minimise drag.
What are flaps?
Lift devices at the trailing edge of the wing. Used in the TKOF to increase lift and shorten TKOF run, during approach and for landing to reduce excess speed before touchdown. Also used as air brakes to shorten the landing run.
Types include plain flaps, slotted flaps, fowler flaps and slotted fowler flaps.
What are spoilers?
Moveable panels situated on the upper part of the wing. When deployed they spoil the flow of air and destroy lift. They increase drag so they are used as airbrakes. Can also be used in flight to reduce speed, increase rate of descent and to assist ailerons in roll control.
What are the 4 types of devices which modify lift and drag?
Winglets, slats, flaps and spoilers
What is the flight envelope of an ACFT?
The limits of altitude, airspeed and load factor within which normal flight manoeuvres can be flown safely.
With an increase in weight, how does the minimum speed of an ACFT change?
Increases
Define service ceiling and absolute ceiling of an ACFT
Service ceiling - the maximum level at which an ACFT can sustain a climb rate of 100 fpm or 0.5 m/s.
Absolute ceiling - Level when the maximum climb rate approaches 0
Define True Air Speed (TAS)
The speed of an ACFT relative to the air mass in which it is flying
Define Mach Number
TAS/Speed of sound
What is the critical mach number
The lower mach number at which the airflow over a part of the ACFT reaches the speed of sound but does not exceed it.
What are the speed ranges for subsonic, transonic, supersonic and hypersonic speeds?
Subsonic - between 0KTAS and M1.0 (Mcrit)
Transonic - between Mcrit and M1.3
Supersonic - between M1.3 and M5
Hypersonic - exceeding M5
Define minimum operating speed
The slowest speed at which an ACFT can maintain level flight. Lift is still created on the upper surface of the aerofoil.
Define stalling speed
The lowest speed an ACFT can fly. Angle of attack is at its maximum
Define maximum operating speed
A speed that may not be deliberately exceeded in any regime of flight.
Define manoeuvre speed
The maximum speed at which full application of available aileron, rudder or elevator will not over stress the aeroplane.
Which 2 factors determine the maximum operating altitude of an ACFT?
Maximum possible differential pressure for pressurised cabins.
Time and oxygen reserves for passengers to descend ACFT from the maximum operating altitude to an altitude where no oxygen is required.
What does the human machine interface extension of an ACFT do?
Prevents the pilot from making control commands that would cause an ACFT to exceed its maximum structural and aerodynamic operating limits.
What are the different types of wing profile?
Dihedral wing- V shape, roll stability, commercial aeroplanes.
Anhedral wing- inverted V shape, high roll rate, military aircraft.
Delta wing- Triangular wing plan, high speed, military and Concorde.
How is a fixed wing ACFT controlled?
Rudder- used for directional control, causes aircraft to manoeuvre in yawing plane, about vertical axis. NB not used to turn aircraft!
Elevators- used for longitudinal control, aircraft manoeuvres in the pitching plane. Used for climb/descent.
Ailerons- used for lateral control, causes aircraft to manoeuvre in the rolling plane. Enables pilot to roll about the longitudinal axis.
Trim tabs- auxiliary flight control surfaces, enable pilot to make adjustments in flight to correct an unbalanced condition.
Flaps and Slats- used during take off and landing to keep lift high at lower speeds. Extending flaps increases camber to increase lift, pivoting flap downwards increases lift and also increase drag which slows aircraft for landing. Slats keep airflow laminar for longer, permitting an increase in attitude of aircraft (angle of flare). Can only be used within a restricted airspeed range.
Power- application of power increases aircraft speed and has secondary effect of climb. (And vice versa).
What happens to the load factor if angle of bank is increased?
It will increase exponentially
What are the 3 axis’s of an ACFT?
Vertical axis - rotation around which is called yaw
Lateral axis - rotation around which is called pitch
Longitudinal axis - rotation around which is called roll
What are the 3 primary flight control surfaces?
Aileron, rudder and elevator
What is the purpose of trim tabs?
To relieve the pilot of constant pressure from the controls in order to maintain steady flight. Adjusted by trim wheels in the cockpit.
What is static stability?
The tendency of an ACFT to return to a steady state of flight without any input from the pilot after being disturbed by an external force.
What is the main source of stability in yaw?
The fin and dorsal. Yaw damper is used on some ACFT.
What is the main source of stability in pitch?
The tailplane
What is the main source of stability in roll?
The design and position of wings and the fuselage. The following techniques can be used individually or in combination:
- High wing relative to the centre of gravity
- Dihedral wings
- Sweptback wings
- High keel surface
How is a fixed wing aircraft controlled?
Rudder- used for directional control, causes aircraft to manoeuvre in yawning plane, about vertical axis. NB not used to turn aircraft!
Elevators- used for longitudinal control, aircraft manoeuvres in the pitching plane. Used for climb/descent.
Ailerons- used for lateral control, causes aircraft to manoeuvre in the rolling plane. Enables pilot to roll about the longitudinal axis.
Trim tabs- auxiliary flight control surfaces, enable pilot to make adjustments in flight to correct an unbalanced condition.
Flaps and Slats- used during take off and landing to keep lift high at lower speeds. Extending flaps increases camber to increase lift, pivoting flap downwards increases drag which slows aircraft for landing. Slats keep airflow laminar for longer, permitting an increase in attitude of aircraft (angle of flare).
Power- application of power increases aircraft speed and has secondary effect of climb. (And vice versa).
What is the ICAO definition of a rotorcraft?
A power driven, heavier than air ACFT supported in flight by the reaction of air on one or more rotors.
Name 4 types of rotorcraft and how lift and thrust generated for each.
Helicopter - Lift: Engine driven rotor, Thrust: Tilted rotor
Autogyro - Lift: Air driven rotor, Thrust: Engine driven propeller
Gyrodyne - Lift: Engine driven rotor and wings, Thrust: Engine driven propeller
Convertiplane - Lift: Engine driven rotor and wings, Thrust: Engine driven rotor, tilted to overcome drag.
What is hovering?
Remaining motionless over a point above the ground. Tip path plane is parallel to the ground. Thrust of the rotor is equal to the weight.
What is an anti torque device on a helicopter used for?
To counteract unwanted rotation of the rotorcraft caused by the rotation of the main rotor.
Give 4 examples of anti torque devices used on rotorcraft
Tail rotor - Small rotor in vertical plane mounted at the end of the tail section
Fenestron - a shrouded tail rotor. Housing is integral with the ACFTs skin.
NOTAR - No tail rotor. Developed as tail rotor failure is highly dangerous.
2 main rotors - One spinning clockwise and the other spinning anti clockwise - e.g. Chinook.
How are Rotary Wing helicopter controlled?
Cyclic control - Controls attitude, therefore pitch and bank. Changes pitch of rotor blades cyclically (pitch of a given blade different depending on position of rotation). Tilts rotor, causing movement in that direction.
Collective- Changes pitch of all rotors at same time, results in helicopter climbing or descending.
Rudder/anti- torque pedals- control direction in which nose of helicopter faces, by changing pitch of tail rotor blades to increase or decrease thrust. Nose yaws in direction of applied pedal.
What are the 3 barometric instruments in the cockpit?
Altimeter, Air Speed Indicator (ASI) and Vertical Speed Indicator (VSI)
What does the pitot-static system consist of?
A pitot tube, a static port and the 3 barometric instruments.
ASI uses the dynamic pressure which is calculated by subtracting measured static pressure from the total pressure measured in the pitot tube.
VSI and Altimeter both use static pressure only.
What will blocking or contamination of the pitot tube and static ports cause?
Pitot tube: Will lead to incorrect IAS read out.
Static port: Will affect all barometric instruments.
Can be very dangerous.
What is an air speed indicator (ASI)?
A barometric instrument which displays the IAS usually in knots (horizontal airspeed of the ACFT in reference to the surrounding air))
What is the difference between the following speeds? IAS, CAS, EAS, TAS and GS.
IAS - Indicated airspeed shown in the cockpit.
CAS - Calibrated airspeed corrected for ACFT installation error - values can be found in the POH.
EAS - Equivalent airspeed. CAS corrected for compressibility effect
TAS - True airspeed. EAS after applying density correction.
GS - Groundspeed. TAS corrected for wind.
What is an altimeter?
A barometric instrument which indicates vertical distance usually in feet above certain pressure reference (in hPA) which is set by the pilot on the sub scale).
What kinds of errors are altimeters subject to?
Meteorological error - In case of change of atmospheric conditions (pressure and/or temperature).
Instrument error:
- Mechanical - manufacturing imperfection including friction
- Position error due to incorrect sensing of static pressure.
- Static port blocked - altimeter will remain constant.
- Incorrect altimeter sub scale setting.
What does a radio/radar altimeter display
Actual height above terrain.
What is a vertical speed indicator (VSI)?
A barometric instrument which displays information about the vertical speed of an aircraft. Can show rate of climb or descent in feet per minute. Subject to same errors as altimeter.
What is a gyroscope and the 2 properties they have?
A fairly massive rotor, usually a wheel, mounted in light supporting rings called gimbals with nearly frictionless bearings. They can spin about an axis in any direction.
2 properties:
Rigidity - Proportional to the RPM of the gyro, mass of rotor and its radius. The rigidity of the gyro can be increased by increasing one or more of these factors.
Precession - If an external force is applied to the gyroscope to change the direction of the rotor axis, the gyro resists the angular movement and moves in plane at a right angle to that of the applied force
What are the 3 gyroscopic instruments in the cockpit?
Turn and bank indicator, Directional Gyro Indicator and artificial horizon
What are the 2 types of gyro drive?
Electrically driven: 4000-4500 rpm
Pneumatically driven by suction and pressure: 8500-12000 rpm
What is the turn and bank coordinator?
Gyroscopic instrument that indicates movement of the ACFT around the vertical and longitudinal axis.
Senses both turning and banking motion (Turn and slip coordinator only senses rate of turn and not rate of bank)
The slip indicator element consists of a heavy ball in a slightly curved closed tube of liquid. The ball reacts to gravity, centripetal and centrifugal force and shows if the ACFT is in balance. If in balance, the ball will remain in the centre
What can cause errors and abnormal indications in a turn and bank coordinator?
Lower gyroscope speed - Lowers rigidity and therefore instrument will under read rate of turn causing the ACFT to turn faster than expected.
Higher gyroscope speed - Increases rigidity and therefore instrument will over read rate of turn causing the ACFT to turn more slower than expected
What is the artificial horizon?
Gyroscopic instrument which indicates the attitude of the ACFT both in pitch and roll. Enables pilot to fly without external visual reference
What can cause errors and abnormal indications in an artificial horizon?
Acceleration error - caused by relatively large mass of the gyroscope. When ACFT accelerates in level flight (during TKOF), false nose up and right turn indication occurs while deceleration will cause the opposite to happen.
Turning error - During turns, centripetal force cause the artificial horizon to over read or under read bank angle by around 2 degrees
What is the directional gyro indicator?
Gyroscopic instrument which provides more stable directional reference for maintaining accurate headings and turns. It has no magnetic element and therefore must be synced with the magnetic compass
What can cause errors and abnormal indications in a directional gyro indicator?
Instrument error - Due to imperfection and friction, gyroscopic precession will misalign the gyroscope over time.
Apparent error due to Earths rotation - Gyro remains in space while Earth rotates beneath it. Error rate depends on latitude, 0 at the Equator and 15° per hour at the poles.
Apparent error due to transport - Even if above error is corrected, as the ACFT flies (especially if changing latitude) the DI must be corrected again.
Lower gyroscope speed - Lowers rigidity causing instrument readings become erratic and therefore unreliable
What is a magnetic compass and associated errors?
An instrument which shows the direction of the ACFT in relation to the Earths magnetic field.
Causes of errors:
Variation - Due to magnetic north pole being in a different location to the true north pole. Results in magnetic heading being different from the true heading.
Deviation - Caused by local magnetic effects.
Compensation magnets minimises deviation. After compensation the remaining deviations are shown on the compass deviation card to enable correction by the pilot
Turbulence - Causes irregular and fluctuating readings
Inclination - Limits use of the compass to lower latitude
What is a gyrosyn compass?
A heading indicator which combines the advantages of the magnetic compass and directional gyro.
What are the types of radio navigation indications in the cockpit?
ADF - Automatic direction finder on board ACFT. Used in conjunction with NDB and indicates relative bearing of the station tuned and/or its QDM/QDR. Components are antennas, ADF receiver and indicator (relative bearing indicator, moving dial indicator or radio magnetic indicator
VOR and TACAN - On board equipment used in conjunction with VOR stations on the ground consisting of an antenna, receiver and indicator. TACAN is military equivalent of VOR/DME. Civl ACFT can use the DME part but not the VOR part.
DME - Distance Measuring Equipment - Shows slant range in NM to the DME station. Can also display groundspeed and time to station in minutes.
ILS - Instrument Landing System - A precision RWY approach aid which gives guidance in both the horizontal and vertical planes. Localiser, glide path and markers.
MLS - Microwave Landing System - Was designed to replace ILS but unlikely to replace it in the near future
What are the types of area navigation systems?
INS - Inertial Navigation System - Self contained system which provide a huge amount of information to pilots without communication with any external reference. Inertial Reference System (IRS) is the next generation of INS using laser gyros instead of gimbals, bearings and motors and powerful microprocessors.
FMS - Flight Management System - Designed to improve navigation and fuel efficiency and reduce pilot workload. It collects date from different systems and enables the ACFT to fly complex routes, use lateral guidance (LNAV) and vertical guidance (VNAV), calculate the optimum cruising altitude and best combination of of auto throttle and speed during climb and descent. Autopilot.
GPS - Global Positioning System - Satellite guidance.
What is an EFIS?
Electronic Flight Information System
- Found in cockpit of modern ACFT.
- Typically contains Primary Flight Display (PFD), Navigation Display (ND) and Multi Function Display (MFD)
What is the ADC and its function?
Air Data Computer
- Receives data from specific pitot, static and temperature probes which is then processed into the following information: Mach number, calibrated airspeed, altitude, vertical speed and true air speed.
- Info is then displayed on various EFIS screens.
- Captains instruments, F/Os instruments and standby instruments
What is the purpose of the Primary Flight Display (PFD)?
- Replaces some of the primary instruments, integrating their information into a single digital screen located directly in front of the pilot set out in such a way that it reduces the pilots workload.
- Info displayed: Airspeed Mach number Attitude Heading Altitude Vertical Autopilot modi
What is the purpose of the Multi Function Display?
Displays:
- Engine performance parameters.
- Checklists
- Data on ACFT systems in a colour coded way (hydraulics, electrical, fuel consumption, landing gear etc)
- Analogue engine instrument indicators completely replaced by MFD.
What are the 2 principal MFD systems?
Engine Indicating and Crew Alerting System (EICAS) used by Boeing
Electronic Centralised ACFT Monitoring (ECAM) used by Boeing.
What is an autopilot system?
A system used to guide an ACFT without assistance of a human being.
What is a Flight Director (FD)
A navigational aid that shows the pilot the attitude required to follow a certain trajectory overlaid onto the artificial horizon.
What is a HUD?
Head Up Display:
- A display projected onto a glass panel placed in front of pilots vision.
- Enables then to read instruments without moving head from normal look out position
- Often used to help pilot land in poor visibility
How is weather radar displayed in the cockpit?
Either on the ND or a dedicated unit.
It is colour coded as follows: Black - Nil or very light precipitation Green - Light precipitation Yellow - Moderate precipitation Red - Heavy precipitation Magenta - Turbulence or wind shear
Which variables indicate the initial conditions of entering an area of wind shear?
GS, airspeed, barometric height, RoD and radio altitude
What is wind shear?
Change in wind velocity along an ACFTs flight path which occurs significantly faster than the ACFT can accelerate or decelerate. Especially dangerous at low levels.
What is GPWS and EGPWS?
(Enhanced) Ground Proximity Warning System:
- Gives oral and graphical warnings at predetermined levels depending on the phase of flight. Operates between 50-2450ft actual height.
- Enhanced version incorporates an electronic world map which have terrain elevations. Advantage is that it can give an earlier warning of terrain proximity.
What is TCAS?
Traffic Alert and Collision Avoidance System
- An ACFT equipment that is an implantation of Airborne Collision Avoidance System (ACAS)
- Uses transponder replies of other ACFT to warn pilot of risk of impending collision.
What makes up an ACFTs Communication System?
VHF COMs - To communicate verbally with controllers
Transponder - On board transmitter/receiver which provides ATC services with information about the identity (Mode A) and altitude (Mode C) of an ACFT.
Datalink - To communicate electronically. ACARS
What types of failure can VHF COMs suffer from?
- COM 1 or COM 2 u/s
- COM 1 and COM2 u/s
- Stuck mic
- Finger trouble
What do the following transponder codes mean? 7000, 7500, 7600 and 7700
7000 - VFR flight
7500 - Hijacking
7600 - Communication failure
7700 - Emergency
What types of failure can a transponder suffer from?
Mode C failure
Transponder u/s
What is ACFT Communication Addressing and Reporting System (ACARS) used for?
Pre DEP clearance, Departure clearance request, CPDLC, automatic dependent surveillance, maintenance reports, met reports/en route wind updates, load sheet, NOTOC, operational flight plan uplink, TELEX
What types of systems does an ACFT have?
EFIS, communications, electrical, hydraulic, fuel, air conditioning, pressurisation, etc
What are the main components of an electrical system?
- Batteries - Convert chemical energy to electrical energy resulting in DC. Normal batteries can be used for engine start if ACFT has no APU or no GPU is available. Emergency batteries ensure power in case of loss of power.
- Generators - Convert mechanical energy to electrical energy resulting in AC. Many ACFT are equipped with starter generators
- Inverter - Converts DC to AC
- AC and DC buses - distribution and collection point for AC/DC power supply
What is a GPU?
Ground Power Unit
- Can be connected to AC and/or DC system through ground connection.
Why is an electrical failure particularly dangerous?
Because most systems onboard an ACFT depend on electricity.
What is the purpose of a hydraulic system?
To enhance human muscular power and to transfer human controlling inputs over a certain distance. Hydraulic fluid is used as a medium.
Used for: Brakes Landing gear/Nose wheel steering Flaps/Slats/Spoilers Rudder/Ailerons
What are the advantages and disadvantages of a hydraulic system?
Advantages:
- Simple generation of great force and torque.
- High accuracy selecting settings.
- Variable propulsion settings over a wide range.
- Easy reversal of direction of travel.
Disadvantages:
- Danger of leakage.
- Temperature susceptibility of hydraulic fluids (Change in viscosity at higher temperatures).
- Higher demands on filtering system.
What are the dangers of hydraulic system problems?
- Complete or partial failure of flight controls.
- Failure of gear extension, brakes, flaps or nose wheel steering.
- Fuel dumping.
- Relatively high speed meaning an increased landing distance is needed.
What is the purpose of the fuel system?
- To ensure engines are provided with fuel under all circumstances.
- Information provided to pilot to monitor fuel system function and show remaining range/endurance.
- Fuel weight information is crucial to determine cruising level.
- Most fuel is stored in the wings due to structural reasons.
What is the purpose of an pressurisation system?
To pressurise the cabin and create a safe environment where humans can breath normally. External air from air inlets and engines can be used to support this pressurisation.
What are the main components of the pressurisation system?
Control panel
Inwards relief valve - To prevent negative differential pressure.
Outflow valve - Helps maintain desired pressure
Safety valve - Relieves over pressure in cabin or negative pressure
Dump valve - Used in an emergency to reduce cabin pressure to 0.
Ditching mode - All outflow/safety valves closed in the event of ditching to prevent water intake.
Emergency pressurisation - Uses bleed air to increase air flow in the event of a pressure leak.
What are the dangers of failure of the pressurisation system?
Over pressurisation, slow or rapid loss of cabin pressure, resulting in an emergency descent
What is the purpose of the air conditioning system?
- To ensure cabin air is safe to breathe.
- Cools down bleed air from the engines.
- Removes ozone (toxic to humans) and converts it to oxygen.
- Recycles cabin air completely every 5 minutes to reduce need for bleed air (reduces fuel consumption). Contaminants and pathogens are removed through a filter.
- Cabin air is very dry so moisture is added to maintain a comfortable humidity (10-15%).
What is the pitch angle of a propeller?
The angle between the propellers plane of rotation and the chord line of the blade.
What are the advantages and disadvantages of a fixed pitch propeller?
Advantages:
- Less maintenance.
- Less prone to malfunction.
- Low cost
Disadvantages:
- Inefficient use of the propulsion system.
- High amount of drag in case of engine failure.
- Risk of engine damage due to overspin in a nose dive.
What are the advantages and disadvantages of a variable pitch propeller?
Advantages:
- Efficient use of propulsion system in every phase of flight
- Feather in case of engine failure.
Disadvantages:
- More prone to malfunction due to a more complicated system.
- High cost
What are 2 possible ways a propeller could malfunction?
- Ground contact
- Runaway prop
What are the advantages and disadvantages of propellers in general?
Advantages:
- Power changes are almost instantaneous (Important if go around required)
- Cost effective for small ACFT - economical low levels and low airspeeds.
Disadvantages:
- Performance reduces as altitude increases (Turbo charging can help).
- MAX 250kts TAS due to propeller limitations.
- High maintenance.
- Power to weight ratio is low.
- Vibrations.
- Considerable drag.
What are the 2 main types of aviation fuel?
AVGAS 100LL (Low lead):
- Most common fuel for piston engines.
- Gas turbines can run on it but not used by choice.
- Dyed blue.
Jet A and Jet A-1:
- Designed for gas turbine engines.
- Similar to kerosene and has a much higher flash point than AVGAS - an important safety feature - much lower is of fire.
What are the 4 stages of a piston engine?
- Induction:
Air/fuel mixture enter cylinder via inlet valve. Piston moves down. - Compression:
Air/fuel mixture compressed until piston is in its top position. - Power/ Combustion:
Air/fuel mixture is ignited and burns progressively. Hot gases in combustion chamber force the piston downwards. - Exhaust:
Exhaust valve opens and piston moves upwards, pushing out exhaust gases.
Where in a piston engine is air mixed with fuel?
Induction system - carburettor
How does a carburettor work?
- The inside of the carburettor is a Venturi tube. As air passes through the Venturi.
- Its velocity increases and static pressure and temperature decrease which creates a vacuum that draws fuel from the carburettors fuel bowl through a tiny orifice called a fuel jet.
- Adjusting the throttle increases or decreases amount of fuel mixed with the air using a valve.
Other than the carburettor, name another system that mixes fuel with air.
Fuel injection system.
What are the components of an aircraft ignition system?
- 2 independent (from the electrical system)ignition systems.
- Magnetos
- Spark plugs
- High tension leads
- Ignition switch
What is the purpose of a lubrication system?
- Reduce friction and wear between engine parts.
- Cools the engine.
- Cleaning and sealing.
- Fights corrosion and rust in the engine.
What are the conditions for carburettor icing?
Temperatures below 20°C and relative humidity above 80%.
Why does carburettor icing occur and what are the dangers of it?
- Due to carburettor Venturi, as air velocity increases, the static pressure decreases which causes rapid cooling of the air in the carburettor throat (approximately 22°C drop)
- If relative humidity is high (above 80%) then cooling process may be sufficient to cause ice to form.
- Carburettor icing reduces and eventually prevents air intake in the engine which would lead to engine failure.
How can we overcome the problem of carburettor icing?
Using a pilot operated carburettor heat system at certain times.
What are the causes and dangers of problems with the engine lubrication system?
- In most cases due to a leak in components like oil coolers, hoses or pipes.
- Significant leaks will most likely result in engine failure after a short time depending on the size of the leak.
- Pilot should shut down engine without delay if a major drop in oil pressure and rise of oil temperature occurs.
