Multi-Engine Aerodynamics

Saturday, May 06, 2023 at 07:43 PM ET

Verified

Why Twins Are Trickier Than Singles Studying the image above should provide some insights into the fundamental physics and aerodynamics of conventional twin-engine airplanes. Obviously, when one engine is turning and the other is “burning,” asymmetric thrust is one result. (Others include losing 50 percent of the airplane’s power, and something like 80 percent of its performance.) Maintaining heading, if not climb performance, requires finding a pitch, yaw and roll attitude presenting the least drag and offering the most thrust. I liken it to balancing the airplane on the head of a pin. — J.B.

Key Takeaways:

Pilots should consistently practice "chair flying" and mental rehearsal of emergency procedures, especially for complex multi-engine maneuvers like engine failures on takeoff.
The crucial "Identify. Verify. Feather." sequence is a core procedure for effectively managing engine failures in multi-engine aircraft, reducing yaw and maintaining control.
Understanding the aerodynamics of yaw and respecting the Minimum Control Speed (V_MC) are vital to prevent dangerous V_MC rollovers, which can be catastrophic at low altitudes.
Continuous practice and maintaining proficiency, even beyond regulatory requirements, are essential for safe multi-engine operations, as mistakes can have severe consequences.

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I’m a big believer in “chair flying.” The best chair is the pilot’s seat of the aircraft you’re learning, with the engine or engines stopped and external electrical power. As a helicopter student, I spent many happy hours sitting in the hangared Robinson, practicing autorotations, a maneuver I found really difficult. Hold your hand like this. Look here. Now look here. Move your hand here. That kind of thing. The maneuver got a lot easier after chair-flying it.

Developing those motor skills and hand/eye coordination doesn’t have to be done while the engines are running, however. Even professional baseball players use tees to practice hitting balls pitched to certain locations.