Classic Bad Stalling Advice


If one of your wings dip sharply during a stall, use opposite rudder
to correct. Using aileron only can aggravate the situation.

I spotted this advice on the internet the other night from an American flying instructor. It’s always disappointing to see this type of advice given by a flying instructor as an instructor should be able to explain any part of the syllabus with unambiguous plain language, lets see how we can improve that and why.

If a wing drops at the stall or the aircraft yaws this is likely to produce further yaw and wing drop. The problem with correcting wing drop with aileron (which is the natural reaction) is that the outboard section of the wing may already be stalled so any further increase in angle of attack (caused by aileron deflection) may cause a deeper stall at the tips. This snowball effect, left uncorrected, may build up to an incipient spin and it may be likely that the aircraft will enter a fully developed autorotative state, commonly known as spinning, if corrective action is not taken immediately. However aircraft designers were well aware of the problem and have used devices or designs to reduce the chances of tip stalling.

WASHOUT –  If you look at the trailing edge of the Cessna 150/152/172/182 etc series you will see that the there is a change of incidence towards the tip and this includes the ailerons. This change of incidence means that when the wing root stalls the wing tip with the ailerons may remain unstalled and hence the ailerons will function normally.

LEADING EDGE SPOILERS – If you look at the leading edge of the Grumman AA1 and AA5 you wil see a small strip of metal on the wing root leading edge. In normal flight and low Aof A this has no effect but at highs A of As it produces turbulence over the wing which will cause the roots to stall before the tips. Interestingly this type of spoiler can be bought as a retro fit kit for Cessna high wing models.

LEADING EDGE SLATS-If you look at the Rally Club or Commodore you will see leading edge slats which spring out automatically at high angles of attack(they are fully extended on the ground) smoothing the airflow over the wing and reducing the possibility of one wing stalling before the other.

ADVERSE AILERON YAW

Adverse aileron yaw is an OUT OF TURN YAW and its presence at the stall can leading the aircraft to drop a wing unexpectedly in the opposite direction. Two methods have been used by designers to prevent adverse aileron yaw

FRISE AILERONS
The Frise aileron is pivoted at about its 25 to 30% chord line and near its bottom surface. When the aileron is deflected up (to make its wing go down), the leading edge of the aileron dips into the airflow beneath the wing.  The down-moving aileron also adds energy to the boundary layer by the airflow from the under-side of the wing that scoops air by the edge of the aileron that follows the upper surface of the aileron and creates a lifting force on the upper surface of the aileron aiding the lift of the wing. That reduces the needed deflection angle of the aileron. If the leading edge of the aileron is sharp or bluntly rounded, that adds significant drag to that wing and help the aircraft to yaw (turn) in the desired direction, but adds some unpleasant or potentially dangerous aerodynamic vibration (flutter).


DIFFERNTIAL AILERONS

The  the up going aileron is made to deflect more than the down aileron  This also helps reduce the likelihood of  wing tip stalling. The DH Tiger Moth was one of the earliest aircraft, to use differential ailerons.

If one of your wings dip sharply during a stall, use opposite rudder
to correct. Using aileron only can aggravate the situation.

So going back to te original statement this is how I would have written it

If one of your wings drops shaply at or around the point of aerodynamic stall use opposite rudder TO PREVENT ANY FURTHER YAW- DO NOT PICK UP THE WING WITH RUDDER.

So stop any further wing drop by using rudder (and this needs practice) recover in the banked attitude and when the wing is unstalled and you have flying speed THEN level the wings. Aileron may well not aggravate the situation and most certainly in some configurations in a slow decelerative stall( standard weights, c of g, loading) in the high wing Cessna aircraft you can pick up the wing at the stall no problem at all-BUT ITS A BAD HABIT TO GET INTO because some aircraft will bite you very hard if you use aileron at the point of stall!

Happy flying!

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