FAA Powerplant Written Practice Test

What is the role of cascade vanes in a thrust reversing system?

1. To direct the exhaust gases outward

2. To turn the fan airstream in a forward direction

3. To increase thrust in reverse

4. To reduce airflow during takeoff

The correct answer is: To turn the fan airstream in a forward direction

Cascade vanes play a crucial role in thrust reversing systems, particularly in turbojet and turbofan engines. Their primary function is to redirect the exhaust gases produced by the engine. When the thrust reversing system is activated, cascade vanes change the direction of the exhaust flow, typically from a straight-out position to a position that directs the exhaust gases forward. This redirection effectively counteracts the forward thrust generated during flight, allowing the aircraft to decelerate more efficiently during landing. By turning the exhaust gases in a forward direction, these vanes significantly contribute to the braking process, enhancing the overall effectiveness of the thrust reversal. This mechanism is particularly important for safety during landing, as it allows for shorter stopping distances, especially on runways that may not be long enough for certain aircraft.