Performance

Question 1

Clearway requirements
- shape
- width
- max slope
- obstacles

Answer 1

Rectangular
>500ft wide
Upward slope <= 1.25%
No protruding object or terrain, except lights if 26in or less above the runway and to each side of it.

Question 2

Balanced field

Answer 2

TODA = ASDA
(i.e. stopway = clearway)

Question 3

Balanced field take off
- description
- effect of added clearway/stopway

Answer 3

TODR = ASDR [note: required]

Maximises mass by using choosing a V1 that balances ASD and TOD requirements.
Extra clearway allows lower V1 (longer at OEI speed) to increase mass.
Extra stopway allows higher V1 (longer stopping distance) to increase mass.

Question 4

Amendments to TODA

Answer 4

Max TODA = 1.5 x TORA

So clearway over 50% of runway length can’t be fully used.

Question 5

Flight path angle designations

Answer 5

We assume wing chord in line with longitudinal axis.

Question 6

Correction for density altitude from pressure altitude

Answer 6

120ft per degree C (difference to ISA)

Question 7

Jet power

Answer 7

Jet power = thrust x TAS

Generally thrust is constant so get a straight line relationship with TAS.

Question 8

Speeds in 1/2 rho V^2

Answer 8

V is TAS
However the total dynamic pressure element of 1/2 rho V^2 relates to CAS/EAS.

Question 9

Which speed is used to asses power required, V(MP) etc?

Answer 9

TAS
This is because power is defined as thrust x TAS.

Question 10

V(R)
V(LOF)
V(2)

Answer 10

V(R) = Speed at which you rotate
V(LOF) = Lift off speed, slightly higher than V(R)
V(2) = Speed at the screen height (end of TOD) which will be higher still [aka Take off safety speed]

Question 11

Using headwind and tailwind in take off distance calculations

Answer 11

Use 150% of tailwind and 50% of headwind for margin of safety.

Question 12

V(stop) and V(go)

Answer 12

V(stop) is the speed above which the aircraft can’t be stopped within the ASDA.
V(go) is the speed below which (based on engine failure) rotation at V(R) and reaching V(2) at 35ft screen height is not possible.

Both vary with mass and are probabilistic lines (i.e. 50:50 chance of making it).

Question 13

V(stop) and V(go) plotted against mass

Answer 13

Question 14

One Engine Inoperative
Field Length Limited
Take Off Mass
(OEI FLL TOM)

Answer 14

OEI FLL TOM is where V(go) = V(stop) = V(1) - called the decision speed
i.e. highest mass at which there is no “die” portion of the V(stop) & V(go) chart!

Question 15

V(EF)

Answer 15

Speed at which an engine failure is assumed to occur. CS25 allows a minimum 1 second delay between V(EF) and V(1) to account for startle effect.
Referred to as “recognise and REACT” in exam, although react doesn’t include starting braking.

Question 16

Changes for wet runway takeoff

Answer 16

V(EF) is reduced by 10kt, with correspondingly lower V(1) speed.
We are further from V(R) at this point so TOD will increase. Therefore screen height is reduced to 15ft (for OEI only!), with V(2) only required at the eventual 35ft point.

Question 17

TO performance calculations for wet runways - process

Answer 17

Need to calculate for wet and dry and use worst case scenario.
TODA: Wet runway with 15ft screen (and slower V(1)) may or may not be more limiting than dry with 35ft.
ASDA: Calculate for wet and dry (with respective V(1wet) and V(1dry)) and also for all engines & engine out. Use the most limiting length.

Question 18

Reverse thrust and ASD required (ASDR)

Answer 18

Reverse thrust can only be factored in for wet runway stopping, not dry runways

Question 19

Other restrictions on V(1)

Answer 19

V(MBE) - V(1) must be less than V(MBE) otherwise brakes can’t cope with the rejection.
V(1) must be above V(MCG) to ensure control can be maintained for any continuation above V(1).

Question 20

All Engine Operating
Field Length Limited
Take Off Mass
(AEO FLL TOM)

Answer 20

This is the TOM restriction based on all engine calculations (with 1.15 safety factor, as it is a likely event).
In typical case this is a vertical line on the V(stop)/V(go) chart which will be higher than the OEI FLL TOM intersection with V1.
If lower (e.g. 4 engine) it will be to the left of the V1 intersection. V1 still valid but that TOM can’t be achieved.

Question 21

TORA vs TODA limitations

Answer 21

Need to get to half of the screen height by end of TORA.
With no clearway TODA will be the limitation, but as clearway increases TORR becomes a limiting factor.

Question 22

TORR

Answer 22

The longest of:
OEI dry: TOR + half distance to 35ft
[OEI wet: TOR + distance to 15ft, if wet!]
AEO: 1.15 x (TOR + half distance to 35ft)

Question 23

V(2) minimums

Answer 23

Max of
- 1.1 x V(MC)
- 1.13 x V(SR)

Question 24

Take off climb limit
- relevant config
- required gradients

Answer 24

There is a minimum requirement for AIR climb gradient, based on gear up and OEI.
2 engines: 2.4%
Combined with altitude & temp data this produces a mass limitation, to be considered along with field length take off mass limits.

Question 25

Cost Index

Answer 25

Operating Cost / Fuel Cost

Question 26

Effect of cost index on climb

Answer 26

High cost index implies low fuel cost. This would mean adopting fast speeds in general (subject to limits, e.g. 250kt

Question 27

Buffet boundary limit

Answer 27

Restricted on slow side by stall speed and high side by mach limit. As altitude increases these close in together, creating "coffin corner". Increased mass brings both in (mostly the stall speed), thus reducing maximum altitude.

Question 28

Buffet boundary limit - Load factor

Answer 28

Increased load above 1g (e.g. due to turbulence) brings in the two limits. Thus buffet boundary charts usually based on 1.3g to give some margin for safety. Need awareness that increased turbulence could take you outside safe operating conditions.

Question 29

Missed approach climb gradients: OEI AEO

Answer 29

OEI: 2.1% AEO: 2.5% AEO (landing climb): 3.2%

Question 30

V(REF) - description - value (class A)

Answer 30

Landing reference speed. This is your speed at screen height. Will usually be V(REF) + 10kt on approach, V(REF) - 10kt at touchdown. V(REF) = 1.23 x V(SRO) class A Not less than V(MCL)

Question 31

Impact of failure on LDR - anti skid brakes - reverse thrust

Answer 31

Anti-skid: +50% Reverse Thrust: +10% [Much higher for prop aircraft]

Question 32

Runway landing distance factors if Wet

Answer 32

1.15

Question 33

Landing distance safety margin

Answer 33

Jet: Land within 60% of LDA

Question 34

Obstacle clearance - Class A Net Take Off Flight Path (NTOFP)

Answer 34

For performance calculation purposes we consider engine failure at V(EF). i) End of TODR (35ft) to gear up point, flown at V(2) ii) From gear up to level flap retraction (c. 400ft), also V(2) with take off thrust iii) [Level] segment for flap retraction, ends when in clean config. Accelerate to final segment climbing speed and reduce thrust on remaining engine to max continuous (MCT) iv) Climb to at least 1500ft, at a climb speed (eg V(X)).

Question 35

Obstacle clearance - En-route obstacle clearance (Class A)

Answer 35

1000ft above terrain within 5nm of route while maintaining height 2000ft during driftdown stage This is about dealing with engine loss in flight. You would generally use MCT for as long as possible to maintain altitude and diagnose, before driftdown to a level where height can be maintained. Can assume fuel dumping to help with driftdown.

Question 36

Flex take off

Answer 36

If TOW is less than MTOW, can use an assumed OAT (greater than actual) in FMS. FMS will use a lower fuel rate based on the higher assumed ambient temperature, reducing thrust and OEI limitations will just be achieved.

Question 37

V(MCG) and V(MCA) for flex take-off

Answer 37

Because full thrust is available even on flex take-off, V(MCG) and V(MCA) must be calculated based on full thrust. Otherwise there is a risk of failure to control aircraft if full thrust is applied.

Question 38

Conditions when flex take off is not allowed

Answer 38

- Icy (or very slippery) runways - Contaminated runways - Anti-skid unserviceable - Reverse thrust unserviceable - Increased V(2) procedure - Power Management Computer off (MRJT1)

Question 39

Conditions when flex take off MAY not be allowed

Answer 39

Wet runways require suitable performance accountability (which in practice is the case for most operators). So wet runways ARE allowed. Not recommended if windshear expected after takeoff.

Question 40

Derated thrust take-off - description - possible on contaminated runways?

Answer 40

AFM must contain a complete set of performance calculations based on a limited thrust setting for the engines. This derated thrust setting can then be selected in FMS. Unlike flex take-off this is considered to be a "normal" take-off, so no restrictions for contaminated runways (etc.)

Question 41

V(MCG) and V(MCA) for derated thrust take-offs

Answer 41

For derated take-offs they will be reduced based on the lower available thrust. This does however mean that TOGA thrust CANNOT be selected during derated thrust take-off. Likely to be restricted until flaps fully retracted.

Question 42

Dynamic hydroplaning speed calc

Answer 42

9 x sqrt(psi) 7.7 for static wheel, but this is likely to be viscous not dynamic hydroplaning

Question 43

Viscous hydroplaning - description - speed calc

Answer 43

When a thin film of liquid prevents the tyre contacting the runway, LIKELY AT RUNWAY THRESHOLDS. Speed = 7.7 x sqrt(psi)

Question 44

Reverted rubber hydroplaning

Answer 44

Can happen after a skid where high temperature in tyre boils and turn layer of water and vaporised rubber to steam.

Question 45

Regulated vs structural vs performance mass limits

Answer 45

Structural are calculated from aircraft weight limits (MZFM etc.). Performance are based on the runway calculations, V(1), V(2) etc. Regulated mass limit is the lower of the two.