Reverse Thrust air?

Question

Is the engine re-directing fan air or bypass air or both when re-directing the exhaust?

Answer 1

Some aircraft have a Fan reverser this makes use of the front fan on a large turbofan jet engine and some re-direct exhaust with large blocker doors which is is located on the aft part of the aircraft , as mentioned in another answer.

Answer 2

Bypass air is air drawn in by the front fan of the engine and blown directly out the back, without passing through the engine core.  Most modern high-bypass jet engines produce the majority of their thrust in this way.

Core air is air drawn in by the front fan and pulled into the engine itself, where it is compressed further, mixed with fuel, and burned to produce thrust.  The thrust turns turbines that turn the rest of the engine (including the front fan and compressors), and then it rushes out the back of the engine, adding to overall engine thrust.

Whether bypass air or core exhaust enter into thrust reversal depends on the design of the the reverse thrust mechanism.  Ideally it would all be directed backwards, but this isn't necessarily always the case.  Some early thrust reversers were notoriously inefficient and just produced a lot of wind and noise without helping to slow down the airplane very much.

Some modern aircraft skip reverse thrust.  The A380 has thrust reversers on only two of four engines, and only then because the FAA insisted on it.  Airbus engineers claim that the brakes alone are sufficient and that reverse thrust isn't unnecessary.  Airbus engineers seem to have a lot of self-confidence.

Answer 3

As others have noted, it depends on the age and/or type of engine.

The aircraft with which I am most familiar is the DC9 and its variants (MD 80, etc).  They use a clamshell type reverser that redirects all of the exhaust.  They work well.

While modern brakes alone are sufficient (as Airbus believes), why not shorten your landing roll and reduce wear and heat by using reverse thrust?  

I can't believe somebody may have had a problem with THIS question.  It seems quite valid.

Answer 4

This is a suitable question, and should not be reported.

Thrust reversers re-direct the whole exhaust of the engine, including both bypass air and core exhaust.

Answer 5

It depends on the type of engine, but most have what are called blocker plates that come out when the TR transitions to the aft (deployed) position. It sends the thrust through the diffuser grid from the bypass area of the engine. The only ones that I can think of that actually use core thrust are clamshell type TR's that close together at the aft of the engine redirecting actual thrust.

Answer 6

Aviophag was right , both because both make exhaust , and the cowling moves and completely changes the direction of exhaust.

Answer 7

both fan and core air is redirected, the holes I am referring is not cascading vanes but deflector vanes (don't have to look for my training notes just to answer) but like I said before T/R lever handle cannot be pull to deploy unless the throttle levers are at idle. Yet in the engine itself the main engine control (fuel pump+fuel heat echanger+fuel servo control), a solenoid is actuated giveng full power as you full deploy the T/R.