Aeroplane Performance

Question 1

Certification Specifications

Answer 1

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

Question 2

CS-25

Answer 2

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

Question 3

CS-23

Answer 3

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

Question 4

Performance Class A

Answer 4

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

Question 5

Single-engine Class B

Answer 5

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

Question 6

What is the impact of CAT safety levels on dispatch weight

Answer 6

The aeroplane performance required for CAT may limit the weight of a dispatched aeroplane in order to achieve a sufficient level of safety

Question 7

Performance Class A

Answer 7

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

Question 8

Performance Category B

Answer 8

Aeroplanes powered by propeller engines with an MOPSC of 9 or less and a MTOM of 5700kg or less

Question 9

Performance Category C

Answer 9

Aeroplanes powered by reciprocating edgings with an MOPSC or more than 9 or a MTOM exceeding 5700kg

Question 10

How are safety levels for CAT achieved

Answer 10

The minimum level of safety required for CAT operations is ensured through the combination of airworthiness requirements and operational limitations

Question 11

Measured Performance

Answer 11

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)

Question 12

Gross performance

Answer 12

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

Question 13

Net performance

Answer 13

is the Gross Performance diminished by a safety factor (margin), laid down by the appropriate authority

Question 14

What is the size of the safety factor?

Answer 14

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

Question 15

How does the range of performance data impact the applied safety factor?

Answer 15

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

Question 16

What is the relationship between Net and Gross distances

Answer 16

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

Question 17

Clearway

Answer 17

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

Question 18

Take-off Run Available (TORA)

Answer 18

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

Question 19

Take-off Distance Available (TODA)

Answer 19

Is normally the runway plus the clearway. The TODA is the lesser of: TORA+clearway or 1.5x TORA

Question 20

Acceleration Stop Distance Available (ASDA)

Answer 20

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

Question 21

Landing Distance Available (LDA)

Answer 21

Is the length of the runway from the threshold to thresshold

Question 22

Can you get LDA, ASDA, TODA, TORA information from Jeppesen aerodrome or AIP charts?

Answer 22

No

Question 23

At what speed is a continuous descent flown?

Answer 23

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

Question 24

Kinetic, chemical and potential energy in flight

Answer 24

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

Question 25

What are the most likely causes of arriving high and fast at the bottom of the descent?

Answer 25

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

Question 26

What is the impact of a hot and high approach

Answer 26

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

Question 27

Aerodrome Classification Numbers

Answer 27

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

Question 28

What happens to the potential energy acquired by an aeroplane?

Answer 28

All potential energy acquired by an aeroplane in flight is lost to drag, heat and friction

Question 29

What is total drag?

Answer 29

The total drag acting on an aeroplane in flight is the sum of parasite drag and induced drag

Question 30

How do the forces relate to each other in steady, unaccelerated, straight and level flight?

Answer 30

In steady, unaccelerated, straight and level flight : L=W and T=DI

Question 31

How do the forces relate to each other in a steady climb

Answer 31

In a steady climb Wcosθ is perpendicular to the flight path, Wsinθ is parallel to the flight path

Question 32

How do the forces act win a constant CAS climb

Answer 32

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

Question 33

How does a constant CAS climb alter the RoC

Answer 33

Climbing at constant CAS results in a decreasing rate of climb

Question 34

In a constant M climb how do climb gradient, RoC and TAS change

Answer 34

Climb gradient, RoC and TAS reduce when climbing at a constant Mach

Question 35

How does the isothermal layer above the tropopause impact TAS in a constant M climb?

Answer 35

Because of the usually isothermal layer just above the tropopause, TAS reduces less rapidly when climbing at a constant Mach

Question 36

How do CAS, AoA, CL, AoD and pitch angle change in a constant M descent?

Answer 36

Even in an isothermal layer at a constant Mach, in descent:
-CAS increases
-AoA and CL decreases
-Angle of Descent increases
-Pitch angle decreases

Question 37

How do CAS, AoA, CL, AoD and pitch angle change in a constant CAS descent?

Answer 37

• CAS, AoA and CL remain constant
  -Pitch and descent angles remain constant