Reverse thrust deployment and why can't you take off again?

[discountinvestigator]

On the old straight pipe jets with clam shell reverse buckets, then there was a basic statement that you could not take-off again after touching down and deploying the buckets. This was said to be because you could risk excessive yaw if the buckets did not restow.

On modern fans, where only the cold section is deflected, then what is the reason for not being allowed to go-around? Is it that the engine power may not allow the doors to reclose? Is the deflected cold stream lift destruction over the wing excessive? Is the deflected cold stream still going to give a greater forward thrust than the hot section full power out of the back and thus induce a beyond design case yaw?

My point of discussion is the commitment to landing of the A320 series once you have touched down because the procedures indicate that reverse should be selected immediately. Did Airbus ever try a baulked landing under these conditions? I just want to understand why you cannot go-around from this point as I have a couple of Airbus family overruns I am dealing with.

Many thanks,

Discount

[411A]

First of all, having actually flown some of the old straight-pipe 4-engine aeroplanes (B707 long body series), reverse didn't really do all that much 'reversing'...just made lots of noise...to the disgust of airport neighbors, no doubt.

The real problem with these old engines was the excessively long spool-up time, so pouring on the coals for a balked landing once reverse was selected was a very bad idea.

Secondly, on newer types, fan blocker doors may well become jammed in the open (deployed) position, and this would not be good for enhanced takeoffs, on short notice.

[Rainboe]

On the large fan/high bypass engines, reverser operation is more fragile than with older engines. They are more prone to jamming, especially the widebody engine types. Once you have even idle reverse, you cannot assume it can be just cancelled and away you go. Translation from reverse to forward can also take varying time. You just don't have the time available to cancel reverse power, wait for low thrust, translate to forward idle then apply power. Once you select even idle reverse, you are committed to stop, whatever happens.

[Checkboard]

Nothing to do with the revesers not stowing, it is simply a recognition that it takes less runway to stop after reverse is selected, than it takes to stow the reversers and then accelerate to lift off speed.

The advice is for pilots that may see a runway blockage, or the end of the runway comming up, and think that they have a chance of avoiding an accident by getting back into the air. Taking this option will merely increase the speed that you crash at.

[Dream Land]

A bit off course :}, does anyone have company SOP for stowing the T/R's on the A320?

[Brian Abraham]

Is the deflected cold stream still going to give a greater forward thrust than the hot section full power

Don't know what the respective vectors are when in reverse but in normal operation the fan (cold stream) provides typically 75% or so of the thrust.

[Dream Land]

Nice post.

[ratarsedagain]

Its sop in our company not to attempt a go around once reverse selected.
However, on a recent sim (a320), our instructor got us to attempt a baulked landing [I]after[I] selecting FULL reverse just show that if you were really in the sh1t for whatever reason and had to get airborne again, the aircraft could do it (runway length permitting).
Not ideal, not recommended, but possible.

[Night-flyer]

that's was really a nice post, I wasnìt aware of this limitation after the reverse trhust deployed.

I'm not holding any type at the moment but I was thinking was possible to performed.

Never finished to learn :}

[Hand Solo]

On the 747 part of the leading edge flaps stow when reverse is selected, so not only could you be attempting a go around with one or more engines stuck in reverse but you'd also have less flap to do it with.

[Dani]

It's pretty easy: When you have started braking already, chances are higher to brake completly. The same is correct for a TO problem: You have started to accellerate already, chances are higher to continue the take off (close to V1).

I would never say never but probabilities are on your side.

Safe flying!
Dani

[Short_Circuit]

My guestimation is that since the T/R (RR & GE) will take twice as long to retract as deploy say 3 seconds and until then no thrust can be commanded, then add spool up time of 5 seconds add decision & response time of the PF, that is some 10 to 15 seconds of little accel or decal screaming down the strip into what ever you are trying to avoid. Now there is a matter of speed brakes & autobrakes to resolve, some flaps etc… this is if all goes to plan.:{

Hit the anchors and rudder around it (keep the eyes open).:eek: