Take-off speeds and stall

The take-off roll

V stands for velocity. A V-speed is a speed with a job: below it or above it, something is allowed or not.

Speeds in this chapter are calibrated airspeeds: near enough what the pilot reads on the airspeed indicator. A twin can lose an engine at the worst moment, and every rule here is written for that day.

One take-off, brakes to 35 ft. Six speeds, always in the same order. The exam keeps asking which comes first and which may not pass which.

The aeroplane is drawn larger than the runway here, so you can see it.

VMCG: minimum control speed on the ground. Below it, an engine failure would pull the aeroplane off the runway. Above it, the rudder can hold it straight.

VEF: the speed at which the critical engine is assumed to fail. Never below VMCG.

V1: the decision speed. About a second after VEF, because that is how long a pilot takes to notice. Before V1: stop. From V1 on: go.

V1 is the last moment to start stopping, and the first from which you can go on.

VR: rotation. The pilot starts to raise the nose. The wheels are still on the ground.

VLOF: lift-off. The main wheels leave the ground.

V2: take-off safety speed, reached by the screen, 35 ft up. If an engine has failed, this is the speed you climb at.

Four look-alikes

Four speeds that sound the same. Ask where the aeroplane is and the name gives itself away.

Ground, air, nose up, brakes.

VMCG: on the ground. An engine quits, take-off thrust on the other, and only the rudder and ailerons may keep it straight. No nose-wheel steering.

Not more than 30 ft from the centre line, with no more than 667 N on the rudder pedal.

Put your hand out of a car window. At walking pace you feel nothing; at speed it pushes hard. A rudder is the same, which is why there is a minimum speed.

It depends on thrust: more thrust from the good engine, more swing. So a cold, low airfield gives a higher VMCG. Hot and high gives a lower one.

VMCA: in the air. Same failure, but flying. Full rudder, and up to 5° of bank towards the good engine.

Highest with the CG aft, because the rudder’s arm is shorter. Falls with altitude, as thrust falls.

VMU: nose in the air. Minimum unstick speed: the slowest it can lift off and keep flying, tail almost dragging.

Found by test pilots. Never used in daily flying.

VMBE: the brakes. Maximum brake energy speed: the fastest you can stop from before the brakes cannot absorb any more.

Stopping turns speed into heat. Heavier means more heat, so more mass lowers VMBE.

Stop or go

This lesson is part of the Navigation plan. See plans

VR and V2 rules

This lesson is part of the Navigation plan. See plans

Stall speed

This lesson is part of the Navigation plan. See plans

The other names

This lesson is part of the Navigation plan. See plans