Definition
A point in a turbine engine's operating range, or in an aircraft's flight envelope, where one condition or control authority transitions to another. In a turbine engine, the crossover point is the airspeed or power setting at which thrust output transitions from one regime to another (for example, from being primarily limited by temperature to being primarily limited by RPM). In propeller-driven aircraft, the crossover airspeed is the speed at which rudder authority can no longer counteract the asymmetric thrust of a failed engine on a multi-engine airplane.
Plain English
The point where one thing takes over from another. In aviation it usually marks the speed or setting at which control or performance shifts from being governed by one factor to being governed by a different one.
Context Anchor
Seen in aircraft maintenance descriptions of engine exhaust systems and other system plumbing.
Derivation
From 'cross' (to pass from one side to another) plus 'over.' The word marks the moment when something passes from one state, side, or condition to another — exactly what's happening at the crossover point.
Why Pilots Care
Knowing crossover prevents loss of directional control in engine-failure scenarios by dictating when full rudder and aileron must be used together.
Intuition Check
Crossover does not mean a flight maneuver here. In this maintenance sense, it means a connecting pipe or passage that carries flow across from one side of a system to another.
Example Sentence 1
During engine-out training, the instructor emphasized staying above the crossover airspeed so full rudder could keep the airplane tracking straight.
Example Sentence 2
During simulator training the pilot practiced maintaining wings level at speeds near crossover following an engine failure.