I didn't want to contaminate the ignorance thread
so I'll post it here so that everyone can be ed-u-ma-cated.
I used to be a jet engine mechanic so I know exactly what the engines do when landing.
This is the basic way typical commercial planes work.
When the plane is coming in for a landing the landing gear is down and the flaps are down. the flaps add lift so that the plane can fly slower but stay in the air. Those two together make a lot of noise but you are still in the air.
When you hit the ground the pilot applies the brakes on the wheels, like a car, and pulls the throttles back. When the throttles pass "idle" the engines go into "reverse" and the further back the throttle is pulled the more the engine revs up and the more reverse thrust you have.
Thrust reversers typically work one of two ways, either "clamshell doors" or "cascading vanes and blocker doors". The engines still run the the same direction, in fact the engine doesn't "know" it is in reverse, it is done through routing air so that it goes out and forward instead of out the back.
Clamshell doors block the exhaust and route it out and forward. they are very common on smaller jet engines.
a couple of videos
http://www.youtube.com/watch?v=9Y6GAILFuew
http://www.youtube.com/watch?v=MqUJbpaTD6Y&feature=related
Cascading vane thrust reversers block the bypass air from the "fan" and route it forward, it is much more streamlined and cleaner then the clamshell design. (doesn't blast exhaust everywhere) the blocker doors block the airflow from the fan and force it out of the cascading vanes.
videos
These are the vanes
http://www.youtube.com/watch?v=dZ-wh8Kuh1M&feature=related
these are the blocker doors
http://www.youtube.com/watch?v=fGnrvHEvf4M&feature=related
turboprop engines change the angle of the propeller blades so that they are pushing air forward.
Thrust reversers can provide enough thrust for the aircraft to "back up"
http://www.youtube.com/watch?v=eSpazcmLc-Y
http://www.youtube.com/watch?v=MRcbJvy_blo
a few military aircraft can apply "reverse" in the air, but commercial planes have this locked out for safety reasons.
hope that helps
so I'll post it here so that everyone can be ed-u-ma-cated.
I used to be a jet engine mechanic so I know exactly what the engines do when landing.
This is the basic way typical commercial planes work.
When the plane is coming in for a landing the landing gear is down and the flaps are down. the flaps add lift so that the plane can fly slower but stay in the air. Those two together make a lot of noise but you are still in the air.
When you hit the ground the pilot applies the brakes on the wheels, like a car, and pulls the throttles back. When the throttles pass "idle" the engines go into "reverse" and the further back the throttle is pulled the more the engine revs up and the more reverse thrust you have.
Thrust reversers typically work one of two ways, either "clamshell doors" or "cascading vanes and blocker doors". The engines still run the the same direction, in fact the engine doesn't "know" it is in reverse, it is done through routing air so that it goes out and forward instead of out the back.
Clamshell doors block the exhaust and route it out and forward. they are very common on smaller jet engines.
a couple of videos
http://www.youtube.com/watch?v=9Y6GAILFuew
http://www.youtube.com/watch?v=MqUJbpaTD6Y&feature=related
Cascading vane thrust reversers block the bypass air from the "fan" and route it forward, it is much more streamlined and cleaner then the clamshell design. (doesn't blast exhaust everywhere) the blocker doors block the airflow from the fan and force it out of the cascading vanes.
videos
These are the vanes
http://www.youtube.com/watch?v=dZ-wh8Kuh1M&feature=related
these are the blocker doors
http://www.youtube.com/watch?v=fGnrvHEvf4M&feature=related
turboprop engines change the angle of the propeller blades so that they are pushing air forward.
Thrust reversers can provide enough thrust for the aircraft to "back up"
http://www.youtube.com/watch?v=eSpazcmLc-Y
http://www.youtube.com/watch?v=MRcbJvy_blo
a few military aircraft can apply "reverse" in the air, but commercial planes have this locked out for safety reasons.
hope that helps
