Aeroplane Performance Flashcards
Certification Specifications
EU Regulation 2018/1139 requires EASA to issue certification specifications. Certification specifications set out how aeroplanes must be designed, and the margins of safety they must be capable of achieving. there are two sets of certification specification (CS) - CS-25 for large turbine aeroplanes and CS-23 for smaller aeroplane types
CS-25
CS-25 covers turbine-powered large aeroplanes (Performance Class A). A ‘large aeroplane’ means an aeroplane of more than 5700kg (12 500lbs) maximum certified take-off weight
CS-23
CS-23 covers aeroplanes in what is called the ‘Normal’ category. This includes aeroplanes with a passenger seating configuration of 19 or less and a maximum certified take-off mass of 8618kg (19 000lbs) or less
Performance Class A
These aeroplanes have the most demanding airworthiness requirements and, therefore, the least stringent operating regulations. Class A aeroplanes are allowed to operate in poor weather conditions and use contaminated runways
Single-engine Class B
These aeroplanes have the least stringent airworthiness requirements and therefore the most stringent operating requirements. This prohibits them from CAT operations at night or in IMC
What is the impact of CAT safety levels on dispatch weight
The aeroplane performance required for CAT may limit the weight of a dispatched aeroplane in order to achieve a sufficient level of safety
Performance Class A
Are multi-engined aeroplanes powered by turbo propeller engines with an MOPSC of more than 9 or an MTOM exceeding 5700kg, and all multi-engined turbo-jet powered aeroplanes
Performance Category B
Aeroplanes powered by propeller engines with an MOPSC of 9 or less and a MTOM of 5700kg or less
Performance Category C
Aeroplanes powered by reciprocating edgings with an MOPSC or more than 9 or a MTOM exceeding 5700kg
How are safety levels for CAT achieved
The minimum level of safety required for CAT operations is ensured through the combination of airworthiness requirements and operational limitations
Measured Performance
Is the average for the aeroplane achieved by experienced and highly skilled test pilots. Measured data is collected for distances, climb gradient, rates of climb and rates of descent for all configurations of flap, slats and landing gear - with all engines working and, if applicable, with one engine inoperative (OEI)
Gross performance
Is the average performance that a fleet of aeroplanes can be expected to achieve, when satisfactorily maintained and flown in accordance with the techniques described in the flight manual
Net performance
is the Gross Performance diminished by a safety factor (margin), laid down by the appropriate authority
What is the size of the safety factor?
The size of the safety factor depends on the likelihood of the measured performance data, the greater the probability of an event (greater than 1:1m), the larger the safety factor required
How does the range of performance data impact the applied safety factor?
The size of the safety factor is also affected by the range of the performance data. eg. the safety factor for landing (67% for a jet) is much larger than for the all-engine take-off (15%). This is due to the much wider range of landing distances, compared to the established range of take-off distances
What is the relationship between Net and Gross distances
Net distances are longer than Gross distances (for take-off and landing) to cater for the possibility for a 1:1m bad day. for the same reason, Net climb gradients are smaller than Gross climb gradients. Net descent gradients are greater than Gross descent gradients
Clearway
Is an area that may be provided at the end of the TORA, in the direction of take-off, which is free fin ab obstacles that would cause a hazard to aeroplanes in flight. It extends at least 75m either side of the extended runway centreline. Lengthwise, it extends to the first non-frangible obstacle. If there are no obstacles, the clearway’s length is restricted to a maximum of 50% of TORA
Take-off Run Available (TORA)
Is the distance between the point on the surface of the aerodrome at which an aeroplane can begin its take-off run to the nearest point, in the direction of take-off, at which the surface of the aerodrome is incapable of bearing the weight of the aeroplane under normal operating conditions
The TORA often (but not always) corresponds to the physical length of the prepared and maintained runway pavement
Take-off Distance Available (TODA)
Is normally the runway plus the clearway. The TODA is the lesser of: TORA+clearway or 1.5x TORA
Acceleration Stop Distance Available (ASDA)
Is the distance from the point on the surface of the aerodrome at which an aeroplane begins its take-off roll to the nearest point in the direction of the take-off at which it cannot roll over the surface of the aerodrome and be brought to a stop in an emergency without risk of accident. ASDA equals TORA plus Stopway
Landing Distance Available (LDA)
Is the length of the runway from the threshold to thresshold
Can you get LDA, ASDA, TODA, TORA information from Jeppesen aerodrome or AIP charts?
No
At what speed is a continuous descent flown?
It is flown as close as possible to VMD in the clean configuration with engines at flight idle throughout. This reduces fuel consumption to the absolute minimum
Kinetic, chemical and potential energy in flight
All potential energy and kinetic energy acquired by an aeroplane is ultimately derived from the chemical energy stored in the fuel. Balancing the requirement for kinetic energy (forward airspeed) with the fuel savings stemming from flight at high altitude (acquiring potential energy) is the key to minimising the fuel burn
What are the most likely causes of arriving high and fast at the bottom of the descent?
1) Failing to enter into the FMC accurate winds for each flight level in descent
2) Failing to closely monitor the predicted bottom of descent position
3) Failing to calculate your height versus track miles to go
If you spot the problem early you may be able to add drag using spoiler and early stages of flap. If you spot the problem late and drag devices are already deployed, then you must increase the track miles to your descent point. This usually involves obtaining permission from ATC
What is the impact of a hot and high approach
Arriving hot and high at the start of the approach is potentially very dangerous because you can’t deviate from the flight path or make significant modifications to the aeroplane’s configuration or thrust setting. Go around and set up for the approach again
Aerodrome Classification Numbers
ACNs give the relative load rating of the aerodrome on pavements for certain specified sub-grade strengths. The PCN for a pavement is the highest acceptable ACN for aeroplanes operating on the surface. You can only operate on a surface if your ACN is less than or equal to the PCN
What happens to the potential energy acquired by an aeroplane?
All potential energy acquired by an aeroplane in flight is lost to drag, heat and friction
What is total drag?
The total drag acting on an aeroplane in flight is the sum of parasite drag and induced drag
How do the forces relate to each other in steady, unaccelerated, straight and level flight?
In steady, unaccelerated, straight and level flight : L=W and T=DI
How do the forces relate to each other in a steady climb
In a steady climb Wcosθ is perpendicular to the flight path, Wsinθ is parallel to the flight path
How do the forces act win a constant CAS climb
Climbing at constant CAS, the angle of attack and coefficient of lift remain constant. However the progressive reduction in air density (and therefore thrust) requires the pitch and flight path angles to decrease
How does a constant CAS climb alter the RoC
Climbing at constant CAS results in a decreasing rate of climb
In a constant M climb how do climb gradient, RoC and TAS change
Climb gradient, RoC and TAS reduce when climbing at a constant Mach
How does the isothermal layer above the tropopause impact TAS in a constant M climb?
Because of the usually isothermal layer just above the tropopause, TAS reduces less rapidly when climbing at a constant Mach
How do CAS, AoA, CL, AoD and pitch angle change in a constant M descent?
Even in an isothermal layer at a constant Mach, in descent:
-CAS increases
-AoA and CL decreases
-Angle of Descent increases
-Pitch angle decreases
How do CAS, AoA, CL, AoD and pitch angle change in a constant CAS descent?
- CAS, AoA and CL remain constant
-Pitch and descent angles remain constant
