3
$\begingroup$

I have noticed that sometimes when you suddenly close reverse thrust you get an increase in airspeed or a 'forward push'. How does it happen? Is it more common on some aircraft types than the others? What type of reverse thrust (clamshell, target type, cold stream) are more prone to this problem? Is this necessarily dangerous?

$\endgroup$
4
  • 1
    $\begingroup$ How much thrust is the engine still producing when the reversers are suddenly closed? $\endgroup$
    – Jim
    Feb 20, 2022 at 3:18
  • $\begingroup$ Are you basing this on data, or the experience as a passenger? $\endgroup$
    – Ron Beyer
    Feb 20, 2022 at 3:48
  • $\begingroup$ I have played flight sims and noticed that, also this has happened in real life. So i want to know why $\endgroup$ Feb 20, 2022 at 5:12
  • 4
    $\begingroup$ There could be 2 (or more) explanations for this... first is that the stowing of the thrust reverser is faster than the spool-down of the engine. The other that I can think of is that you aren't feeling an acceleration, just not as much deceleration, just like in a car if you brake hard then let off. $\endgroup$
    – Ron Beyer
    Feb 20, 2022 at 5:50

1 Answer 1

10
$\begingroup$

I've done that in CRJs when I was just freshly type rated until I learned to modulate the reversers during the landing (I don't remember the effect happening, or being noticeable at least, in the sim during training).

When you deploy the reversers you have a range where you can modulate the thrust between idle and max, just like in forward, but just using the reverser levers. At the bottom of the range, there is a reverse idle setting just above fully stowed. So you can unlatch and pull the levers up a bit where you are at reverse idle (usually there is a positive detent to tell you you are in idle reverse), then you can move them farther up and thrust will increase until they are all the way and you are at max reverse thrust. You can go back down and modulate the thrust the other way, down to idle reverse, with the reversers still deployed with the engines at idle, until you push them all the way back down to the stow position.

Technique wise, when you go to max reverse and you want to remove reverse thrust, you should ease the levers to idle reverse first, let the engines spool down, then move them to stow.

A lot of pilots will just go straight from max reverse directly to the stow position in one action, not pausing at idle reverse, because they may be a little busy with the landing, or just inexperienced. The result is the engine's fan is still driving significant air, as it's spooling down, while the reverser doors or clamshells have stowed, resulting in a residual forward thrust kick from the fan's inertia that lasts a second or two.

It feels like you let off the brakes a bit then put them back on.

$\endgroup$

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .