WHAT IS THRUST REVERSAL?

The term thrust is define as the   which actspropulsive force which acts against the air movement and propels the aircraft in forward direction.
NOW! WHAT ARE THE AIRCRAFT COMPONENT USED AFTER  LANDING, TO STOP THE   AIRCRAFT AT CORRECT POSITION?

• Brakes
• Spoilers
• Thrust reversing.

So in this post i will mainly concentrate on thrust reversing concept .
Thrust reversing doesn't mean that reversing the aircraft engine ,rather changing the air movement .
During normal operations, air enters via the front of the engine, gets accelerated and expelled through the engine’s nozzle. This generates thrust that pushes an aircraft forwards.

During normal operations, air enters via the front of the engine, gets accelerated and expelled through the engine’s nozzle. This generates thrust that pushes an aircraft forwards.

Types of thrust reversal :

• The cold_stream system.
• The target -type system. 

• THE COLD_STREAM SYSTEM:

The cold stream system is applied exclusively to high bypass ratio turbofan engine(like GEnX engine), where there is a much higher quantity of bypass  airflow compared to the engine core airflow.

• operation:

when reverse thrust is actuated(through lever) ,the aft(the tail part of engine)nacelle slides rearwards,bringing the blocker doors into the action ,such that obstructing the bypass air which is cold (which has not gone through combustion reaction) without affecting the hot exhaust(with combustion reaction).at the same time revealing  cascade vents(which are the openings that allow the deflected air to escape). this vents are at an particular (say 135deg) so as to aim the cold exhaust in the forward direction .thus this mechanism help the aircraft to slow down .with the use of reverse thrust.

this thrust reversal are employed for modern airliners like boeing -747  , A300.

operation of cold stream system.

  

  

• THE TARGET TYPE REVERSE THRUST:

In this type the thrust reversal system redirects both bypass air and hot exhaust forwards.

• operation :

 it has two hinged doors are mounted on the aft section of the engine .when they are in state of inactive,they are kept at top-off of the engine ,creating a smooth aerodynamic surface.

when this doors are actuated ,they block the exhaust portion of engine ,thereby deflecting the air forward.such that the airplane speed can be decreased and made halt at a required position .

NOTE: Thrust reversal actuated only when weather,wind, or in icy condition of runway .

Thrust reversal operation at icy condition.

with the use thrust reversal concept power back operation  can done .it rarely done because safety is concern and fuel  need to be conserve.

• ACCIDENT RELATED TO THRUST REVERSAL:

On 11 February 1978  pacific western airlines flight 314, Boeing 737-200 ,crashed executing a rejected landing at cranbrook airport. The left thrust reverser had not properly stowed; it deployed during the climbout, causing the aircraft to roll to the left and strike the ground. Out of 5 crew members and 44 passengers, only 6 passengers and a flight attendant survived.

• Conclusion:

The purpose of using thrust reversal is reduce the stress /wear on the brakes.

Operation of thrust reversal produces noisy sound. 

Thank you.