Multi-Engine AC Airspeeds and Definitions

Question 1

What is Vmc speed?

Answer 1

Minimum Control Speed

The minimum speed at which it is possible, with maximum rudder deflection and no more than 5o angel of bank, to maintain control of the AC and maintain straight flight, following sudden failure of the critical engine

Question 2

If one engine fails, what is the AC going to do?

Answer 2

At speeds below Vmc the AC will yaw and roll towards the engine that has failed (due to the functioning engine still creating thrust and the dead one obviously creating none. The good engine is basically dragging the plane forward by that side)

Question 3

After losing one engine, what is the only way you will be able to maintain control of the AC?

Answer 3

By reducing the power of the good engine and/or by increasing the airspeed by a change in pitch in order to get above the Vmc speed (you try not to be below that speed in the first place)

Question 4

What is a ‘critical engine’?

Answer 4

If an AC has two engines that are rotating in the same direction, one will be the ‘critical’ engine.

Becasue of P Factor (a propeller’s downgoing blade creates more thrust that the reciprocal upgoing blade), one engine will cause the AC to yaw a lot more if the other engine quits.

So the critical engine is the one that will cause the least yawing/rolling if it quits (if one has to quit, you’d rather it not be the critical one)

Question 5

What are the factors that affect Vmc?

Answer 5

All POH Vmc numbers are based on the following conditions:

• All engines developping max rated power at the time of the critical engine failing
• The AC is at a minimum practical test weight with a rearmost C of G. (If the weight distribution changes, so will the Vmc. And a heavier AC will have a lower Vmc)
• Landing gear retracted, flaps at T/O. and prop on the failed critical engine windmilling

Question 6

Why does a rearward C of G cause your Vmc to go up and a forward one cause it to go down?

Answer 6

Has to do with weight and balance.

Question 7

What is V1?

Answer 7

Decision Speed

Speed beyond which the AC is committed to fly and cannot stop on the remaining runway.

• If an engine fails before V1, abort takeoff
• If an engine fails after V1, you’re taking off whether you want to or not

It it fails after V1/takeoff, you would then use your Vyse or V2 speed to climb

Question 8

What is Vr?

Answer 8

Rotation speed (speed at which we start to raise the nose)

Question 9

What is V2?

Answer 9

The speed at which the AC can safely be flown on one engine

(This speed does not apply to light piston AC. In that case you would have a Vyse speed to use

Question 10

What are Vf and Vfe?

Answer 10

Vf: Max speed at which wing flaps may be extended
Vfe: Max speed permissible with the wing flaps in a prescribed extended position (applies to AC that has different speeds for different flap settings - like the diamond and most multi-engine planes)

Question 11

What is Vsse?

Answer 11

The speed you use when intentionally failing an engine (for training?)

This speed is higher than both Vmc and Vs.

Question 12

Whta is Vle?

Answer 12

Max speed permissible with landing gear extended

Question 13

What is Vyse?

Answer 13

Speed that provides the maximum altitude gain for the shortest time (Vy + Single Engine)

Sometimes is a blue line on the ASI.

Question 14

What is Vxse?

Answer 14

Most altitude over the least distance with a failed engine

Question 15

What is Vs and Vso?

Answer 15

Vs: Stalling speed with a clean config (gear and flaps up)
Vso: Stall speed in landing config