Certified Flight Instructor - Flight Instructor Airplane Practice Exam

In a multiengine airplane with clockwise-rotating engines, the concept of the critical engine relates to the impact of engine failure on the aircraft's performance and control. When an engine fails, the remaining engine produces a yawing moment toward the failed engine due to the differences in thrust vector and drag. The critical engine is the one that, if lost, would have the most negative effect on the aircraft's performance and controllability.

In this scenario, the left engine is identified as the critical engine because the right engine's center of thrust is farther away from the aircraft's centerline. This distance creates a larger yawing moment toward the left side when the right engine fails. Therefore, losing the left engine (the one closer to the centerline) would result in a significantly greater yawing moment toward the left side, which could lead to uncontrollability if not managed properly.

This understanding is essential for pilots, as it informs their approach to safety procedures, engine-out training, and decision-making in the event of an engine failure. Recognizing which engine is critical helps in understanding how to counteract the adverse yaw and maintain control of the airplane during such situations.