4
$\begingroup$

When an A330/40 is in alternate law1 and approaching a stall, it has a stall warning composed entirely of a cricket chirp and a voice saying "stall, stall". Most other aircraft, in contrast, have a stickshaker, which vibrates the stick when the aircraft approaches a stall.

Pilots are, as demonstrated by numerous crashes, very (very very) good at tuning out aural warnings, whereas a stickshaker provides a powerful tactile cue that is very difficult to ignore; so why doesn't the A330/40 have a stickshaker?

1: In normal law, the A330/40 has no stall warning, as its automatic angle-of-attack protections supposedly make it impossible to stall the aircraft by pulling on the stick.

$\endgroup$
6
  • 1
    $\begingroup$ Stall warning operates independently from the high-AOA protection and does sound in normal law. This would happen in highly dynamic situation where alpha/speed variations are large, especially when operating close to maximum weight. $\endgroup$
    – busdriver
    Apr 20, 2019 at 4:09
  • 4
    $\begingroup$ Without any knowledge about certification of the sidestick controller, I would speculate that shaking the controller would hamper the controllability and disturb the movements on the sidestick. The range of motion on the sidestick is much smaller than on conventional yoke and required deflections are often so small that shaker would actually prevent accurate flying in the critical moment. $\endgroup$
    – busdriver
    Apr 20, 2019 at 4:32
  • 1
    $\begingroup$ @user40476: I said tuning out, not turning off. $\endgroup$
    – Vikki
    May 29, 2019 at 0:56
  • 1
    $\begingroup$ Sorry, thank you, but you can’t ignore the STALL aural alarm it’s so loudly. Further the stick displacement is very narrow compared to a yoke, a stick shaker will produce oscillating inputs to the stick transducers. $\endgroup$
    – user40476
    May 30, 2019 at 10:13
  • 5
    $\begingroup$ @user40476: You'd be surprised at what pilots can ignore. $\endgroup$
    – Vikki
    Nov 14, 2019 at 22:35

1 Answer 1

6
$\begingroup$

Having flown the 737 (with a stick shaker) and A320 (without a stick shaker) for several years, two things come to mind:

  1. The aural warning is VERY loud and distinct. I can hardly imagine that anyone would miss it.
  2. In your type training, and sometimes in your recurrent trainings, you practice stall recoveries, and this sound seems to be stuck and hard-wired to your brain after a few times.
  3. If the sidestick would vibrate, it would be very hard to control the aircraft properly. The stick is very sensitive to even small deflections, whereas in conventional aircraft, or generally speaking aircraft with yoke-type controls, have much larger deflections to steer the aircraft. There, a shaking yoke does not interfere with your controls as much.

To sum it up: it is not necessary and would do more harm than good.

$\endgroup$
2
  • $\begingroup$ Would some sort of haptic-feedback system (like those built into most video-game controllers) be able to provide the pilot with a tactile stall warning without generating spurious flight-control inputs? $\endgroup$
    – Vikki
    Mar 16, 2023 at 22:37
  • 1
    $\begingroup$ That's difficult to tell. It would have to be strong enough to be noticeable, but not too strong as to not interfere with the stick movements. My guess is that you will probably not be able to satisfy both requirements. The aircraft is really sensitive to stick inputs, especially in alternate law or abnormal attitude law. $\endgroup$
    – Flo
    Mar 19, 2023 at 11:25

You must log in to answer this question.

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