Asymmetric Flight

Question 1

Explain the consideration involved in coping with asymmetric thrust/drag and reduced power.

Answer 1

The immediate concern is to control the yaw and any roll that results from the asymmetric thrust.

Question 2

Explain the factors affecting yawing and rolling moments. (Yawing moment, thrust from live engine, distance of thrust-line from CoG, directional stability, rate of thrust decay, drag of failed engine, propellor torque reaction, asymmetric blade effect)

Answer 2

The strength of the yawing moment due to the asymmetry of thrust and drag about the CofG is proportional

The thrust from the live engine​:
Higher the thrust, greater the yawing moment.

Distance of the thrust-line from the CofG​:
Increased distance increases the arm through which the live engine acts and therefore increases the yawing moment.

Directional stability​:
To obtain directional stability, the aircraft is constructed with the greater proportion of the wing and rudder surface area behind the CoG than ahead.

The weathercocking effect from a high directional stability (greater proportion of the fin and rudder surface area behind the CofG than ahead of it) acts to keep the fuselage aligned with the direction of flight as the weathercocking moment resists the asymmetric thrust yawing moment.

The rate of thrust decay​:
If the engine failure is gradual, the onset of the yawing moment will also be gradual.

Drag of the failed engine​:
The greater the increase in drag on the dead engine side, the stronger the yawing moment toward that side.

Rolling moment: ​
develops through the further effect of yaw and the loss of slipstream over the wing, resulting in a loss of lift on the side of the failed
engine.

Propeller torque reaction: ​
The action of the engine in rotating the propeller produced a reaction that rolls the aircraft in the opposite direction around the engine.

Asymmetric Blade effect​:
In the normal cruise the thrust line can be taken to coincide with the direction of flight.

Question 3

Recall immediate actions and techniques for identifying the failed engine. (9)

Answer 3

1. Control - Stay in control
2. Speed
3. Maximise power (Rich, pitch, power)
4. Minimise drag (flap up, u/c up)
5. Identify (dead leg = dead engine)
6. Verify (Gauges, look at engine (fire?) propeller stopped)
7. Terrain critical? (Trouble checks?) (immediate feather 2000AGL)
8. Verify prop lever (dead engine nothing should happen)
9. Feather the prop (smoothly and quickly)

Question 4

Define Vmca and Vmcg.

Answer 4

VMCA​:

the minimum control speed following a sudden engine failure of the critical engine after take-off at which the average pilot will be able to maintain directional control of the aircraft with full rudder and no more than 5 degrees of bankapplied.

VMCG​:
the minimum control speed at which, after a failure of the critical engine during the take-off run, it’s possible to maintain directional control with rudder control alone.

Speed assumes the take-off will be continued. It is not applicable to light twin aircraft.