Definition
A multiengine flight condition, following the failure of one engine, in which the airplane is flown with no lateral airflow across the fuselage. It is achieved by establishing a small bank angle of approximately 2 to 3 degrees toward the operating engine, combined with sufficient rudder to keep the ball of the inclinometer slightly deflected toward the operating engine. This configuration produces the lowest total drag and the best single-engine climb performance.
Plain English
After one engine quits on a twin, you don't fly with the wings perfectly level. You bank a tiny bit toward the working engine and use rudder to keep the airplane slicing cleanly through the air. Done right, the airplane isn't slipping sideways at all, and that gives you the best chance of climbing.
Context Anchor
Seen in multiengine airplane training, especially when discussing one-engine-inoperative climb performance after an engine failure.
Derivation
Sideslip' describes air flowing across the side of the fuselage rather than straight along it. 'Zero sideslip' means that sideways flow has been eliminated. The term tells you exactly what the pilot is trying to achieve: no sideways component to the relative wind.
Why Pilots Care
This configuration produces the highest possible climb performance and lowest drag when an engine fails, directly affecting whether the aircraft can clear obstacles or reach a suitable landing site.
Grounding Statement
With one engine failed, the airplane wants to yaw and drag sideways unless the pilot banks and uses rudder to line it up cleanly with the airflow.
Intuition Check
Do not assume “zero sideslip” means wings level or the ball perfectly centered. In engine-out flight, zero sideslip usually requires a slight bank toward the operating engine, and the ball may not be exactly centered.
Example Sentence 1
After the right engine failed, the pilot banked two degrees left and adjusted rudder to establish zero sideslip flight before turning back to the airport.
Example Sentence 2
In zero sideslip engine-out flight the inclinometer ball is slightly displaced toward the good engine, confirming the fuselage is aligned with the relative wind.