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).