In the described scenario, the critical engine failure would produce what relative yawing effect?

• A. Greater yawing moment
• B. Lesser yawing moment
• C. No yawing moment
• D. Variable yawing moment depending on weight

Answer: (A)

When an engine fails on a twin, the airplane becomes asymmetric in thrust, which creates a yawing moment about the vertical axis toward the side of the failed engine. The critical engine is defined as the engine whose failure would produce the greatest yaw moment and thus the greatest challenge to directional control. The configuration of the engines and propeller rotation means that losing that particular engine leaves a larger yaw tendency than losing the other one. So, in this scenario, the engine that is most “critical” would cause a greater yawing moment if it fails. Weight can affect handling and rudder effectiveness, but the concept of which engine is critical is about the relative yaw impact of the failure itself, not a change with weight.