7 ms·

Not a pilot, but my interpretation is that the pilot probably tried to slow down to make the jump easier. That got him closer to the stall speed. Having one en

Not a pilot, but my interpretation is that the pilot probably tried to slow down to make the jump easier. That got him closer to the stall speed. Having one engine with less thrust is something twin engine pilots train a lot for (engine out scenario) but also something that puts you closer to stall speeds. The rudder is the primary way to control airplane direction when you are close to stall speeds because you lose aileron controls around that time (they don't do much when you stall). It's also what you use during engine out and what can trigger a spin during a stall. Now having the center of gravity change would be dangerous under those circumstances. Stall recovery is also something pilots train for as that is highly dangerous during takeoffs and landings. A landing is basically a controlled stall. Spin recovery is less commonly trained for because it basically means you messed up the stall recovery, which should not happen. Sounds like the pilot did the correct thing (eliminate async trust and nose down). So, not a good incident but it happened at an altitude where there was plenty of time to recover.

zeusk 5y ago
Landing is definitely not a controlled stall. A stall during flare can damage airframe.
- VBprogrammer 5y ago
  At some point during landing the wing has to stall. Certainly a 3 point landing in a taildragger is taught as an uncontrolled crash from 2 inches above the ground. The reality is more complex as different parts of the wing will be experiencing different conditions and different wing features (flaps, steps, bugs, dings etc).
  - zeusk 5y ago
    Controlled descent and touch down does not require stall. Not sure where you’re getting that but in my type (sr22), touch down is at speeds considerably above stall speed in landing configuration. Ref Approach (100% flap) -> 85-90kt Stall (100% flap) - 59kt And documented stall speeds are when the wingtips and ailerons start losing effectiveness - the wing still generates plenty of lift.
    - krisoft 5y ago
      This might be a different schools of thought then? The way my flight instructor explained to me (Cessna 150) that you can land very smoothly without stalling, but if your airplane has the energy you are still flying. Just you are doing it 0 inches above the runway. If any outside disturbances increase your energy or redirect you (such as a gust of wind, or a bump on the grass field) you become airborne again and the chances of messing things up increases from there. (bunny hopping etc...) So he expected this stall from 4 inches from me, and told me off if he couldn't hear the stall warning whistle come on at the last moment just before touchdown. That being said I also heard that this is absolutely not how one should land an airliner. This type of landing would cause a tail strike there. So who knows. Maybe my trainer was old school. Maybe what is correct on a Cessna 150 on a grass field is not correct on your type or airfield.
      - mannykannot 5y ago
        This may be a matter of loose terminology - in the flare (and when slowing down in level flight generally), once you have reached the angle of attack giving the maximum coefficient of lift, you will descend (and therefore, in the flare, touch down.) Though there will be some flow separation at this point (and before) it is still a couple of degrees from a full-blown stall.
      - avereveard 5y ago
        Stall is about airflow separation, not lift force. You can most definitely not have enough lift for flight, but not at enough angle of attack to be in a stall.
      - jaywalk 5y ago
        The stall warning sounds before the airplane actually stalls, by definition. You were not actually stalling the plane.
    - mannykannot 5y ago
      In addition, the ground effect will lower the stalling speed for any given weight and configuration, as compared to at altitude.
  - NikolaeVarius 5y ago
    No it doesn't, Velocity landing should be above stall speed, albeit slightly. No one wants the airframe to crash/slam into the ground. Source: Aeronautical in a previous life
  - lazide 5y ago
    A stall is fundamentally a loss of lift from the airflow leaving a lift producing configuration. Some people might use it as a ‘stall from 2”’ to describe landing, but it’s fundamentally undesirable in controlled flight (which includes getting wheels on the ground). You don’t actually stall at 2”, and if you were that is a very bad idea as a gust of wind can mean you’ll randomly stall at 20ft next time and crash.
caconym_ 5y ago
Also not a pilot but my understanding is that spins in multiengine aircraft are generally considered extremely dangerous, to the extent that they aren't even spun in testing/certification. From here^[1]: > No multiengine airplane is approved for spins, and their spin recovery characteristics are generally very poor. It is therefore necessary to practice spin avoidance and maintain a high awareness of situations that can result in an inadvertent spin. In something like a Caravan this might not be such a big deal (though I don't know about their stall-spin characteristics) but deliberately courting stall-spin in a big twin like a King Air by using asymmetrical thrust so close to stall seems extraordinarily dangerous bordering on reckless, even if you aren't counting the presence of skydivers near the out-of-control aircraft. The fact that it's established practice doesn't mean it's safe; it can just as easily be a "normalization of deviance" sort of thing. As other commenters have mentioned, I think bringing both engines back to low power or idle, and accepting a moderate sink rate during the jump, would be much safer. That way, even if you do stall, you at least aren't doing it in an asymmetrical thrust condition. ^[1] https://www.flightliteracy.com/stalls-in-multiengine-aircraft/ https://www.flightliteracy.com/stalls-in-multiengine-aircraf...
- lazide 5y ago
  If there is a sizable sink rate, or higher speeds, the odds of a jumper hitting the elevator or other parts of the plane are higher. We used to have to watch out even on little Cessna 182s - in the right conditions someone could easily hit it and rip it off, then everyone is in a world of hurt.
  - caconym_ 5y ago
    Regarding higher airspeed, I'm not suggesting that they go any faster—only that they burn altitude to maintain airspeed instead of flying level on asymmetrical thrust. Regarding sink rate, in the absence of a definitive source I don't really buy that a moderate sink rate (again, with the same low airspeed) is going to significantly increase the risk of somebody hitting the tailplane. In the absurd extreme of a vertical dive, I guess a skydiver would probably be outpaced by the aircraft due to their different terminal velocities, but a shallow dive is a very different picture.
mleonhard 5y ago
> A landing is basically a controlled stall. A stall is when the wing stops producing lift due to reduced air speed. Plane wings do not stall during landing. They produce lift all through the landing process. The plane uses flaps [0] to reduce the stall speed of the wings so they continue producing lift as the plane slows down. In the final stage of landing, the plane uses ground effect to produce lift at even slower speeds. [0] https://en.wikipedia.org/wiki/Flap_(aeronautics) https://en.wikipedia.org/wiki/Flap_(aeronautics) [1] https://en.wikipedia.org/wiki/Ground_effect_(aerodynamics) https://en.wikipedia.org/wiki/Ground_effect_(aerodynamics)

zeusk 5y ago

Landing is definitely not a controlled stall. A stall during flare can damage airframe.

VBprogrammer 5y ago
At some point during landing the wing has to stall. Certainly a 3 point landing in a taildragger is taught as an uncontrolled crash from 2 inches above the ground. The reality is more complex as different parts of the wing will be experiencing different conditions and different wing features (flaps, steps, bugs, dings etc).
- zeusk 5y ago
  Controlled descent and touch down does not require stall. Not sure where you’re getting that but in my type (sr22), touch down is at speeds considerably above stall speed in landing configuration. Ref Approach (100% flap) -> 85-90kt Stall (100% flap) - 59kt And documented stall speeds are when the wingtips and ailerons start losing effectiveness - the wing still generates plenty of lift.
  - krisoft 5y ago
    This might be a different schools of thought then? The way my flight instructor explained to me (Cessna 150) that you can land very smoothly without stalling, but if your airplane has the energy you are still flying. Just you are doing it 0 inches above the runway. If any outside disturbances increase your energy or redirect you (such as a gust of wind, or a bump on the grass field) you become airborne again and the chances of messing things up increases from there. (bunny hopping etc...) So he expected this stall from 4 inches from me, and told me off if he couldn't hear the stall warning whistle come on at the last moment just before touchdown. That being said I also heard that this is absolutely not how one should land an airliner. This type of landing would cause a tail strike there. So who knows. Maybe my trainer was old school. Maybe what is correct on a Cessna 150 on a grass field is not correct on your type or airfield.
    - mannykannot 5y ago
      This may be a matter of loose terminology - in the flare (and when slowing down in level flight generally), once you have reached the angle of attack giving the maximum coefficient of lift, you will descend (and therefore, in the flare, touch down.) Though there will be some flow separation at this point (and before) it is still a couple of degrees from a full-blown stall.
    - avereveard 5y ago
      Stall is about airflow separation, not lift force. You can most definitely not have enough lift for flight, but not at enough angle of attack to be in a stall.
    - jaywalk 5y ago
      The stall warning sounds before the airplane actually stalls, by definition. You were not actually stalling the plane.
  - mannykannot 5y ago
    In addition, the ground effect will lower the stalling speed for any given weight and configuration, as compared to at altitude.
- NikolaeVarius 5y ago
  No it doesn't, Velocity landing should be above stall speed, albeit slightly. No one wants the airframe to crash/slam into the ground. Source: Aeronautical in a previous life
- lazide 5y ago
  A stall is fundamentally a loss of lift from the airflow leaving a lift producing configuration. Some people might use it as a ‘stall from 2”’ to describe landing, but it’s fundamentally undesirable in controlled flight (which includes getting wheels on the ground). You don’t actually stall at 2”, and if you were that is a very bad idea as a gust of wind can mean you’ll randomly stall at 20ft next time and crash.

caconym_ 5y ago

Also not a pilot but my understanding is that spins in multiengine aircraft are generally considered extremely dangerous, to the extent that they aren't even spun in testing/certification. From here^[1]: > No multiengine airplane is approved for spins, and their spin recovery characteristics are generally very poor. It is therefore necessary to practice spin avoidance and maintain a high awareness of situations that can result in an inadvertent spin. In something like a Caravan this might not be such a big deal (though I don't know about their stall-spin characteristics) but deliberately courting stall-spin in a big twin like a King Air by using asymmetrical thrust so close to stall seems extraordinarily dangerous bordering on reckless, even if you aren't counting the presence of skydivers near the out-of-control aircraft. The fact that it's established practice doesn't mean it's safe; it can just as easily be a "normalization of deviance" sort of thing. As other commenters have mentioned, I think bringing both engines back to low power or idle, and accepting a moderate sink rate during the jump, would be much safer. That way, even if you do stall, you at least aren't doing it in an asymmetrical thrust condition. ^[1] https://www.flightliteracy.com/stalls-in-multiengine-aircraft/ https://www.flightliteracy.com/stalls-in-multiengine-aircraf...

lazide 5y ago
If there is a sizable sink rate, or higher speeds, the odds of a jumper hitting the elevator or other parts of the plane are higher. We used to have to watch out even on little Cessna 182s - in the right conditions someone could easily hit it and rip it off, then everyone is in a world of hurt.
- caconym_ 5y ago
  Regarding higher airspeed, I'm not suggesting that they go any faster—only that they burn altitude to maintain airspeed instead of flying level on asymmetrical thrust. Regarding sink rate, in the absence of a definitive source I don't really buy that a moderate sink rate (again, with the same low airspeed) is going to significantly increase the risk of somebody hitting the tailplane. In the absurd extreme of a vertical dive, I guess a skydiver would probably be outpaced by the aircraft due to their different terminal velocities, but a shallow dive is a very different picture.

mleonhard 5y ago

> A landing is basically a controlled stall. A stall is when the wing stops producing lift due to reduced air speed. Plane wings do not stall during landing. They produce lift all through the landing process. The plane uses flaps [0] to reduce the stall speed of the wings so they continue producing lift as the plane slows down. In the final stage of landing, the plane uses ground effect to produce lift at even slower speeds. [0] https://en.wikipedia.org/wiki/Flap_(aeronautics) https://en.wikipedia.org/wiki/Flap_(aeronautics) [1] https://en.wikipedia.org/wiki/Ground_effect_(aerodynamics) https://en.wikipedia.org/wiki/Ground_effect_(aerodynamics)