Stalls in turbulence

[Steve Jeff]

As you climb to the higher air mass, you will stop climbing but should not lose altitude. Your airspeed in relation to the lower air mass will not drop. Stall is in relation to the air mass around you.

Not necessary climbing, let's assume I'm flying straight and level at 150 ft AGL when the 15kts headwind suddenly changes its direction 180 degrees. My airspeed will drop 15kts or 30kts?

Va decreases as weight decreases yes, but your attempted example is flawed for that very reason. If the airplanes have the same wings but are flying with different weights, they must have different Va's.

As for momentary gusts, you are trying to suggest that when a wing has a gust exceed its critical angle of attack for a second, total control of the aircraft is lost. That does not happen due to inertia. As you slow towards the stall speed, turbulence causes more AoA excursions and you will provide more and larger control inputs to correct in between the "gusts". As you slow, there will be a speed where the time that the wing is having AoA problems exceeds the time that the wing is flying. Somewhere around that time you will effectively lose control of the aircraft. That is why you fly the landing pattern at a higher speed on turbulent days.

Few knots added gives just a small G margin in addition. What I thought was that when the critical angle of attack of one wing or both will be exceeded, the airplane will stall and possible to have also a wingdrop and considering we are talking about flying at a higher airspeed than 1G stall, the stall induced by a un upward gust will have a much greater effect, that's whi I thought it might induce a spin. The differential lift between the two wings will be really high assuming that only one wing stalled.

Each aircraft has what is called a V-N diagram that charts the airspeed vs G caused by pilot maneuvering or "gusts". The V-N diagram has an outline drawn on it that shows whether a particular G at a specific air speed results in the wing stalling (exceeding its critical AoA) or the airplane actually breaking. But to effectively use the V-N diagram you need to have a G meter installed in addition to your airspeed indicator. My observation is that the majority of pilots grossly over-estimate the G's that they think they have experienced. Anyway, look at your V-N diagram, look at the airspeed that you fly final on a bumpy day, and see how large or small your speed and G margin is. That will answer the question that you seem to be asking.

I guess it's not very large, that margin.

Yes, an updraft would + load the airplane, for a second.

Why that one second is not enough to induce a stall (with wing drop if it's stalled just one wing)?