Asymmetric Flight

Question 1

What is asymmetric flight?

Answer 1

• Where one engine produces less thrust than the other
• Total thrust line of the aircraft shifts toward the live engine
• Causes aircraft to yaw towards the failed engine

Question 2

Factors affecting the magnitude of the yawing moment

Answer 2

• Thrust from the live engine - the more thrust, the greater the yawing moment towards the failed engine. Strongest on take off and climb where the power setting is high
• Drag from the failed engine - the greater the drag the stronger the yaw. Significant when the propeller is windmilling and reduced when it is feathered.
• Distance of the thrust line from the CoG - the greater the distance, the stronger the yawing moment
• Directional stability - The more directional stability the aircraft has, the less yawing moment it experiences.
• Rate of thrust decay - If the engine failure occurs gradually, the yawing moment will be gradual as well.

Question 3

Factors affecting the rolling moment

Answer 3

• Secondary effect of yaw - will roll the aircraft towards the failed engine.
• Loss of slipstream - reduced lift on one wing causing the aircraft to roll.
• Torque reaction

Question 4

Critical engine

Answer 4

• Yawing moment is larger when the left engine fails
• Due to greater moment arm on the right engine
• The engine with the smallest moment arm is referred to as the ‘critical engine’.

Question 5

Immediate actions after an engine failure in a multi-engine

Answer 5

• Control yaw with the rudder
• Control the roll with the ailerons

Question 6

Identifying the failed engine

Answer 6

• The direction of the aircraft yaw
• Aircraft will yaw towards the failed engine

Working leg, working engine. Dead leg, dead engine

Question 7

Methods of constant-heading asymmetric flight

Answer 7

• All rudder - Using substantial rudder input to counteract yawing moment. Not commonly used because of the extra drag produced.
• All bank - Only uses aileron input, no rudder. Can cause slip, and the increased banking leads to a lot of drag
• Rudder and bank combined - Initial rudder to counteract yawing moment, then a slight bank towards the live engine.

Question 8

Vmca

Answer 8

• Minimum control speed airborne
• The minimum airspeed after take-off at which multi-engine aircraft can be controlled safely with one engine inoperative and the live engine at full power
• Airspeeds below Vmca may not have sufficient directional authority control to counteract yawing moment asymmetric thrust produced by the live engine.
• Vmca should not be greater than Vs x 1.13
• Indicated by a redline on the airspeed indicator

Question 9

Vmcg

Answer 9

• Minimum control speed ground
• Minimum speed during take-off run at which the pilot can maintain directional control of a multi-engine aircraft with the critical engine inoperative and the live engine at full power, using only rudder.