V-speeds & definitions

032 PerformanceChapter 1

Regulatory framework

Key fact

CS-25 — large aircraft requirements. CS-23 — small aircraft requirements. Performance data is published as measured (test pilots), gross (fleet average, line pilots), and net (gross degraded by safety factors).

Aircraft classes

Definition — Class A

All turbo-jet aircraft, plus any multi-engine aircraft that is turbo-propeller driven with MOPSC greater than 9 or MTOW greater than 5700 kg.

Definition — Class B

Propeller aircraft with MOPSC 9 or less and MTOW 5700 kg or less (CAP MEP 1.2). Turboprops meeting these limits are Class B; reciprocating engines above the limits are Class C.

Exam trap

Turboprops are Class A when MOPSC exceeds 9 or MTOW exceeds 5700 kg. Pistons/reciprocating above those limits are Class C, not Class A.

Runway definitions

Definition — TORA

Take-Off Run Available — length suitable for the take-off ground run.

Definition — ASDA

Accelerate-Stop Distance Available — TORA plus stopway. Stopway is on the centre-line, at least as wide as the runway, supports an aircraft in an RTO but cannot permanently withstand the aircraft.

Definition — TODA

Take-Off Distance Available — TORA plus clearway. Clearway is beyond the runway where the aircraft may fly at below screen height; minimum 75 m either side of centre-line; slope not exceeding 1.25%; maximum 50% of TORA.

Definition — LDA

Landing Distance Available — length suitable for the landing ground run.

Key fact

When stopway and clearway are equal length, TODA = ASDA. Items in the clearway must be frangible (break on impact, minimal hazard).

Flight phases & screen heights

Phase	Definition
Take-off	Brake release to screen height
T/O climb	Screen height to 1500 ft AGL
En-route	1500 ft AGL to 1000 ft AGL
Approach	1000 ft AGL to screen height
Landing	Screen height to full stop

Key fact

Screen height: 50 ft for Class B or Class A (dry take-off or normal landings, AoB ≤15° at take-off). 35 ft for Class A dry take-off or steep approach. 15 ft for Class A wet take-off.

Climb speeds — jets vs props

Speed	Jet	Propeller
Best endurance	VMD	VMP
Best angle (VX)	VMD	VMP
Best rate (VY)	greater than VMD (≈ 1.32 VMD)	VMD
Best specific range	1.32 VMD	VMD

Formula — Speed order (memory aid)

VS  →  VMP  →  VX(P)  →  VY(P)  →  VMD/VX(J)  →  VY(J)  →  1.32 VMD

Mnemonic: Eat Chicken Tikka Masala — Long Range Cruise ≈ 4% faster than max range.

Key fact

VX — best/max angle of climb; max obstacle clearance; max excess thrust. VY — best rate of climb; max excess power (PA − PR). VY is always ≥ VX.

Key fact

With altitude (IAS): VX constant, VY decreases. Both increase as TAS. Both increase with mass and decrease with drag.

Stall and reference speeds

Definition — VS

Stall speed — minimum steady flight speed at which the aircraft is controllable.

Definition — VSR

Reference stall speed — approximately 6% higher than VS.

Definition — VSO

Stall speed in landing configuration.

Take-off V-speeds (general)

Definition — VMCG

Minimum control speed on the ground — determined without nose-wheel steering, no crosswind; engine thrust and rudder deflection are key. VMCG ≤ VEF ≤ V1.

Definition — VMCA

Minimum control speed in the air — maintain straight flight with 5° AoB; ≤ 1.2 VS1.

Definition — V1

Decision speed — at V1 the pilot decides to continue or abort (last resort). Limited by VMCG, VR, and VMBE. Min = VMCG, max = VR. Must not exceed VMBE.

Definition — VR

Rotation speed — initiation of rotation to lift-off angle. Must be ≥ V1 and ≥ 1.05 VMCA (Class A). Not affected by wind or slope.

Definition — V2

Take-off safety speed at screen height (35 ft Class A dry). ≥ V2(MIN); ≥ VR + speed attained to screen height.

Definition — VMBE

Maximum brake energy speed — must not be exceeded by V1. If TOM is VMBE-limited, uphill runway reduces brake energy and may allow increased mass.

Definition — VEF

Speed at which the critical engine is assumed to fail — 2 seconds recognition delay before V1.

Exam trap

Higher V1 with constant VR → ASDR increases, TODR decreases. V1 exceeds correct value → ASD exceeds ASDA. Anti-skid inoperative → lower V1 (manual braking needs earlier decision).

Landing speeds

Definition — VREF

Landing reference speed at screen height. Class B: ≥ 1.3 VSO (greater of VMCL or 1.3 VSO). Class A: ≥ 1.23 VSR0 (≈6% faster than VSO). VREF is regulatory and does not change for turbulence.

Definition — VMCL

Minimum control speed for landing.

Mass terminology

Key fact

MCTOM — Maximum Certified Take-Off Mass. FLTOM — field limited (TODA). CLTOM — climb limited. PLTOM = lowest of FLTOM and CLTOM. FLLTOM reduced by high PA, bleeds on, upslope, high temperature, contamination, tailwind; increased by flaps (field limit only).