Reverse Thrust
Having a reverse thrust capability has improved aircraft handling to the point that landing a modern aircraft on a wet/dry or icy runway is straight forward.
the diagram shows the stopping distances when landing an aircraft, with and without the using the reversal thrust system. The usual method of operating the reverse thrust system is to select it immediately the weight of the aircraft is firmly on the main wheels. There are three basic thrust revsersal systems
1) Clamshell Doors 2) Bucket Doors (external doors) 3) Plucket Door The Reversing system reverse the direction of the gas flow, thereby reversing the thrust. |
Clamshell
The clamshell door system uses high pressure compressor air as its power source. Pneaumtic rams move the reverser doors from their stowed position (forward thrust) to their deployed postion (reverse thrust) In stowed Position, the clamshell doors cover cascade vanes, which are shown when the doors move to the deployed state. while deployed, the clamshell doors, shut of the normal exhaust gas exit, forcing the gas to through the cascade vanes in a forward direction, so that the forward motion of the aircraft is opposed by the reverse thus generated. the lower cascade vanes are aiming the exhaust mainly in forward direction, but they are angled so that the exhaust also has an outboard angular component which minimises the chances of debris and hot gases being-ingested into the engine intake durin the use of reversal thrust. Bucket Doors (External)
the bucket system is normally hydraulically operated The rear portion of the engine exhaust pipe is shaped like two halves of a bottomless bucket, hinged to enable them to swing rearwards, when selected, deflecting the exhaust gas forward. |
Cold Stream Reverser
is used only on high by pass ratio fan jet engines. The blocker system blocks and diverts the cold by-pass air stream only. Operation of all these systems is initiated by movement of reverse thrust levers in the cockpit. Each engine with a reverse thrust capability has a reverse thrust lever. So in the blocker system, the speed and direction of an 'air motor' is determined by operation of the reverse thrust lever. |
Indication and Safety Systems
so that the pilot has information about the position of reverser doors, some form of warning is fitted. the warning can be amber lights positioned somewhere on the forward instrument array or shown aircraft monitoring system.
The warnings will be shown whenever the reverse doors are unlocked and away from stowed position.
Restrictions of Use
To prevent catastrophic outcomes on the engine, the standard operating procedure on some aircraft is to reduce the position of the reverse thrust lever to the reverse idle position at around 60-80 Knots. When the reverse system is in use, engine indications must be closely monitored, in particular for excessive EGT. Care must be in thought when increasing R.P.M. with reverse thrust selected, that the engines responds symmetrically, as adverse yaw can be induced if they aren't.
so that the pilot has information about the position of reverser doors, some form of warning is fitted. the warning can be amber lights positioned somewhere on the forward instrument array or shown aircraft monitoring system.
The warnings will be shown whenever the reverse doors are unlocked and away from stowed position.
Restrictions of Use
To prevent catastrophic outcomes on the engine, the standard operating procedure on some aircraft is to reduce the position of the reverse thrust lever to the reverse idle position at around 60-80 Knots. When the reverse system is in use, engine indications must be closely monitored, in particular for excessive EGT. Care must be in thought when increasing R.P.M. with reverse thrust selected, that the engines responds symmetrically, as adverse yaw can be induced if they aren't.