Stall warning

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AKar
A2A Master Mechanic
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Joined: 26 May 2013, 05:03

Re: Stall warning

Post by AKar »

DHenriquesA2A wrote:The way I've always explained this to students entering the landing phase is that the purpose of touching down at the stall indication is to make the touchdown at the lowest possible airspeed. What's indicative here is imparting the mindset to the student that it is entire possible to land the airplane at a speed higher than the stall speed. Once this concept sinks in the student begins to associate the flare into what it should be; that being the slowing down of the aircraft to reach touchdown at the slowest speed which of course will occur as the wing transitions through it's max CL at the stall point.
What happens if the student DOESN'T understand this concept usually results in touchdowns somewhere before the wing reaches its max CL while in sink at some airspeed above stall but beneath the lift needed to cancel out the sink rate.
Out of topic maybe, but when flying gliders, with wing-loadings especially low, and the approach speeds as well in comparison to the wind speeds, I found the difficulty gets exponentially higher with gusting winds. Somehow, my not-approved-technique eventually ended up to be to bring the airplane over the beginning of the threshold, maybe a few feet high; but with reasonably positive airspeed margin... then slowly full airbrake and smooth back stick up to full. I knew the plane settled rather well, if I were low enough, and touched down smoothly via tail wheel. I knew any uplift would mean I just stall and sink through; should any significant forward gust come, I just punch the airbrakes down and re-calculate the touchdown.

The main difficulty, as I felt, was that I had a handful - or footful! - in keeping the nose aligned; in gliders that takes some modest pedal work even in 10 kts gusting. It is very easy to loose the track of your actual energy state when you are just pushing your feet against the springs..not once or twice, but more I sank through to a hard landing while concentrating on something not as important as the energy of the airplane.

-Esa

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DHenriques_
A2A Chief Pilot
Posts: 5711
Joined: 27 Mar 2009, 08:31
Location: East Coast United States

Re: Stall warning

Post by DHenriques_ »

AKar wrote:
DHenriquesA2A wrote:The way I've always explained this to students entering the landing phase is that the purpose of touching down at the stall indication is to make the touchdown at the lowest possible airspeed. What's indicative here is imparting the mindset to the student that it is entire possible to land the airplane at a speed higher than the stall speed. Once this concept sinks in the student begins to associate the flare into what it should be; that being the slowing down of the aircraft to reach touchdown at the slowest speed which of course will occur as the wing transitions through it's max CL at the stall point.
What happens if the student DOESN'T understand this concept usually results in touchdowns somewhere before the wing reaches its max CL while in sink at some airspeed above stall but beneath the lift needed to cancel out the sink rate.
Out of topic maybe, but when flying gliders, with wing-loadings especially low, and the approach speeds as well in comparison to the wind speeds, I found the difficulty gets exponentially higher with gusting winds. Somehow, my not-approved-technique eventually ended up to be to bring the airplane over the beginning of the threshold, maybe a few feet high; but with reasonably positive airspeed margin... then slowly full airbrake and smooth back stick up to full. I knew the plane settled rather well, if I were low enough, and touched down smoothly via tail wheel. I knew any uplift would mean I just stall and sink through; should any significant forward gust come, I just punch the airbrakes down and re-calculate the touchdown.

The main difficulty, as I felt, was that I had a handful - or footful! - in keeping the nose aligned; in gliders that takes some modest pedal work even in 10 kts gusting. It is very easy to loose the track of your actual energy state when you are just pushing your feet against the springs..not once or twice, but more I sank through to a hard landing while concentrating on something not as important as the energy of the airplane.

-Esa
The glider landing of course carries the extra benefit of spoilers. This technology was used as well on the F14 Tomcat for example. The 14 used DLC devices that if deployed could alter a final approach without the need for an alpha change.
VERY handy !
DH

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Piper_EEWL
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Re: Stall warning

Post by Piper_EEWL »

guillaume78150 wrote:Vielen Dank.
Gern geschehen :wink:
B377&COTS, J3 Cub, B-17G, Spitfire, P-40, P-51D, C172, C182, Pa28, Pa24, T-6 Texan, L-049&COTS, Bonanza V35B

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