Page 169 - The Jet Engine

15: Thrust reversal

Contents Page

Introduction 159
Principles of operation 160

Clamshell door system
Bucket target system
Cold stream reverser system
Turbo-propeller reverse pitch system
Construction and materials 166

INTRODUCTION using engine power as a deceleration force. Thrust
reversal has been used to reduce airspeed in flight
1. Modern aircraft brakes are very efficient but on but it is not commonly used on modern aircraft. The
wet, icy or snow covered runways this efficiency may difference in landing distances between an aircraft
be reduced by the loss of adhesion between the without reverse thrust and one using reverse thrust is
aircraft tyre and the runway thus creating a need for illustrated in fig. 15-1.
an additional method of bringing the aircraft to rest
within the required distance. 3. On high by-pass ratio (fan) engines, reverse
thrust action is achieved by reversing the fan (cold
2. A simple and effective way to reduce the aircraft stream) airflow. It is not necessary to reverse the
landing run on both dry and slippery runways is to exhaust gas flow (hot stream) as the majority of the
reverse the direction of the exhaust gas stream, thus engine thrust is derived from the fan.

159