Recently I was flying a 500ft circuit, when in the downwind leg I felt a buffeting, when I looked at my ASI, to my horror, I was at stall speed.

I recovered without incident, (recover might be an exaggeration, I don't think the stall developed), but it got me wondering, is there any app available (or can you add to SkyDemon) a stall warning alarm? Obviously the tablet can't detect AoA, so it would just be based on your speed vs stall speed, which you would need to set.

If not, what other options are there? This is in a C42.

To clarify, the Ikarus C42 does not have a stall warning horn

  • $\begingroup$ Did I read that right? There's no stall warning horn in a C42? $\endgroup$
    – Jamiec
    Commented Jul 14, 2023 at 16:00
  • $\begingroup$ @Jamiec Some aircraft use the aerodynamic buffet as the stall warning. See my answer for more info. $\endgroup$
    – 1nf
    Commented Jul 14, 2023 at 22:04
  • $\begingroup$ @1nf Yep, I am aware, perhaps mandela effect, but I was sure id heard a stall horn in a C42. $\endgroup$
    – Jamiec
    Commented Jul 17, 2023 at 6:53
  • $\begingroup$ Hey @Jamiec no horn, or any other warning in a C42 $\endgroup$
    – Cloud
    Commented Jul 17, 2023 at 10:15

1 Answer 1


Your tablet will not be able to gather your IAS without an interface to your aircraft's sensors. Your "speed" would be ground speed from the GPS receiver in your tablet, so any sort of winds would throw off your stall warning and make it useless. I don't think what you are looking for is possible without an avionics interface. To add to this as you correctly laid out in your question what really matters for determining a stall is AOA. Stalls can occur at any airspeed, so even if you had your IAS on your iPad it wouldn't be truly accurate.

23.207 declares that an audible or visual indication is not required anyway as long as the aircraft exhibits a "warning" 5 knots before the stall. In the C42's case I imagine this is the buffet, so that is the warning that you are about to develop a stall and provides the same functionality as a stall horn in another aircraft type. A stall alarm is not necessary.

  • $\begingroup$ There isn't a horn on a C42? $\endgroup$
    – CGCampbell
    Commented Jul 14, 2023 at 14:37
  • $\begingroup$ @CGCampbell In a quick video I watched I didn't hear one, and I'm not sure why Cloud would have this issue if it did have one. $\endgroup$
    – 1nf
    Commented Jul 14, 2023 at 14:45
  • 2
    $\begingroup$ +1, the buffet seemingly IS the warning. Pilot made a mistake, the aircraft alerted him to it, the pilot landed safely. The system worked as designed. $\endgroup$
    – Ben
    Commented Jul 14, 2023 at 21:08
  • $\begingroup$ buffeting : "irregular oscillation of part of an aircraft, caused by turbulence." - how do you know if it's stalling or just hitting some turbulence? $\endgroup$
    – Mazura
    Commented Jul 15, 2023 at 0:36
  • $\begingroup$ @Mazura good question, and I think it's one worth asking as it's own question so more people can see it and answer. I don't have a good answer, I would say that in turbulence my guts feel it whereas buffeting is just affecting the aircraft. But I encourage you to ask it separately to get a better answer! $\endgroup$
    – Ben
    Commented Jul 17, 2023 at 5:35

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