Take-off & landing

032 PerformanceChapter 2

Take-off distance required

Key fact

TODR splits into ground roll plus airborne distance to screen height. TODR = v² ÷ 2a (mass directly affects TODR). LDR = VREF² ÷ 2a (measured screen height to full stop; splits into flare and ground run).

Formula — Factors increasing TODR

Mass ↑ · Pressure altitude ↑ · Temperature ↑ · Tailwind ↑ · Upslope ↑ · Contamination ↑ · Thrust ↓ (altitude/temp/bleeds)

Key fact

Speed ↑ = thrust ↓ (jets: initial RAM effect may decrease then increase thrust). Altitude ↑ = thrust ↓. Temperature ↑ = thrust ↓ (flat-rated engines give constant thrust up to a limit temperature).

V1 and balanced field

Key fact

Clearway but no stopway: TOD greater than ASD → V1 must be lower. Stopway but no clearway: TOD less than ASD → V1 will be higher. Balanced field: single V1 value (TODA = ASDA when stopway = clearway length).

Exam trap

Above V1, you must take off. RTO initiated at or before V1. First action on RTO: reduce thrust. 2 second delay between VEF and V1 for recognition.

V1 changes

Key fact

V1 increases when: pressure altitude ↑, temperature ↑, TOM ↑, flap deflection ↓, headwind ↑, runway upslope. VR follows the same factors except wind and slope. V2 decreases when: PA ↑, temperature ↑, TOM ↓, flap deflection ↑. VMCG/VMCA not affected by mass or flaps.

Landing distance

Key fact

LDR increases when: mass ↑ (VREF ↑), air density ↓ (TAS ↑), tailwind ↑, runway downslope, less flaps. Technique: positive touchdown, full reverse, brakes ASAP.

Key fact

Friction reduces as lift increases. Runway contamination increases impingement and displacement drag. Reverse thrust inoperative increases ASDR on wet runways.

Class B regulatory factors (CAP SEP 2.1.1)

Situation	Factor
No stopway/clearway	TORR = TODR (gross) × 1.25
With stopway/clearway	TORR = TODR (gross) × 1.0
With stopway/clearway	ASDR = TODR (gross) × 1.3
With stopway/clearway	TODR = TODR (gross) × 1.15
Dry grass	× 1.2
Wet grass	× 1.3
1% upslope (take-off)	× 1.05
Landing LDR (regulatory)	LDR (gross) × 1.43
Grass landing	× 1.15
Wet landing	× 1.15
1% downslope (landing)	× 1.05

Exam trap

Mnemonic for stopway/clearway: ASS 1.3, TOD 1.15, TOR 1.0. If the question asks for distance required, expect the net value.

Class B take-off speeds

Key fact

VR must be higher than VS1. Speed at 50 ft (VREF take-off context): safe speed, ≥ 1.2 VS1. Minimum 4% climb gradient at take-off power, flaps in take-off position. VREF ≤ 1.3 VSO for landing. Minimum 3.3% climb gradient with flaps in landing position at VREF.

Contaminated runway

Key fact

Contaminated when greater than 0.3 mm covering greater than 25% of runway. Increases all required distances except compact snow and ice (ASDR only). Decreases max mass, V1 and VR. Standing water, slush, wet/dry snow increase impingement drag — V1 reduction smaller as contamination thickens.

Improved climb / increased V2

Key fact

Also called Improved Climb Procedure. Used when excess field length available (ASD not limiting). Higher screen height along runway; increases TODR and climb gradient for given TOM; V1 decreases; obstacle clearance near runway reduced. Limited by FLLTOM and tyre speed limit.

Assumed temperature & derated thrust

Key fact

Assumed temperature take-off reduces operating costs, noise, engine life — may be overridden with TOGA. Derated thrust cannot be overridden. Not used if windshear reported. ASDR decreases but TODR increases. Thrust increases as OAT decreases.

Brake release to screen — friction

Key fact

VMBE — maximum brake energy speed. On contaminated runways drag increases then decreases during ground roll. Use factored winds: 50% headwind, 150% tailwind for take-off calculations.