On a Boeing 737, why does a cover open and then close on the engine after landing?

Question

I fly on 737s regularly and I've noticed that just after the plane has landed a cover opens on the side of the engine for about 10 seconds then slides shut again before the plane has reached the end of the runway. The cover is a meter or so in length and underneath it looks to me like there is an air filter of some description. Any pilots, aviation engineers or plane buffs explain what this is and why it happens?

Answer 1

Its the reverse thrust coming into action, there are different types of thrust reversers on engines: bucket type(like on older 737's), clamshell(like on A340-200/300's) and translating cowl reversers like on the 737 you mentioned. In the translating cowl type reversers like the 737 you saw, the aft part of the engines cowl slides backwards to redirect thrust sideways instead of forward, thus helping to slow the plane down.

Answer 2

Jeesh! Please don't answer questions you don't know the answers to! They are thrust reversers to help slow down the plane when landing, it has nothing to do with "cooling the engine", in fact, it make the engines HOTTER!!!

Answer 3

To cool down the engine.

Answer 4

Too cool off the engine

Answer 5

The side of the wing opens because the engine is very hot after landing, Take off, they need to cool it down for awhile so while taxing or such other they open it

Answer 6

reverse thrusters choose the best answer of that answer of a commercial pilot well explained all i know that it aids in/or prevents the air intake in the engine, thus, making the aircraft decrease its speed

Answer 7

Cool off the engine..lol, that's funny!!  They are thrust reversers.  It has nothing to do with cooling, in fact, it makes them hotter.  Why do people answer things that they know nothing about?

Answer 8

Those are called thrust reversers, and they are like reverse gear in you car except a plane automatically deploys them while the airplane touches down to slow it down, airplane engine only uses 30% of air that is sucked in for combustion the rest goes around the engine for cooling purposes. When the reversers open the air is rushed forward to slow down the aircraft and the guide vanes actually guide the air forward, and the cool thing is the are Carbon Fiber. They are usually activated by a teleflex cable located on the right hand main gear, it also activates the panels on wings called "spoilers" that go up to aid in slowing down the aircraft.

Answer 9

Reverse thrust.

The engine nacelle ( cover) slides back and angles fins internally to push the  bypass air ( the air inside the engine propelling the aircraft forward) to a slightly forward-facing angle. the "air filter" is probably the fins to vent this air in the right direction.

Image of 737 reverse thrusters : http://upload.wikimedia.org/wikipedia/co...

Sometimes the reverse thruster is a simple scoop which deploys from the exhaust that just forces the airflow to move, depends on engine type.

Answer 10

I wish people who don't know anything about it would stop posting wild guesses on here where answers belong.

What you are seeing is the thrust reversers deploying and then closing.  The engines are at normal temperatures and do not need special cooling appliances.

Answer 11

Air exchanger

Answer 12

Do the engines seem to get louder as the cover opens? If so you are probably looking at the reverse thrust doors opening that re-direct the air coming out of the engine forward to help slow down the airplane. That's the only door I can think of that opens on the engine after landing.

Here is a video of a reverse thrust door opening on a 737-300 a 737-200 is a little different and towards the back end of the engine

http://www.youtube.com/watch?v=IMHR1eFWp...