This is where an "angle of attack" meter saves the day, since the plane will stall at the same angle of attack no matter what the flight conditions.
+++++++++++++++++++++++++ Larry F has referenced a brilliant source of definitions (and a whole lot more) - well worth a read. Over years I have tried to express AofA in the simplest (least confusing) manner - it is an important term in the life of an aviator. In the simplest of terms - A of A is the angular diff between where the airplane is pointing and where it is going - think about it. Then think about the deck angle during a power off stall vs. the deck angle that can be attained by going on the back of the power curve - assuming that the aircraft is moving horizontally in both cases, just at the moment of stall. I am not sure what value A of A will have in alerting a pilot to stalling CONDITIONS. Many pilots fly cross-controls as an approach technique in cross winds. Cross controls is also good for stalling one wing (that is how we get a tardy aerobatic bird to crisp up the snap rolls). The un-alerted pilot may well be drawn into large cross-control deflections during a cross wind approach, thus pretty dangerous conditions at a modest AofA - nothing like the high nose I see during regular stalls with similar flap setting. The actual topic however is "stall warning" This has saved my bacon more than once by alerting me under conditions during which I was not expecting (ready for) a stall. I hope it will do so for many more pilots, many more times. There are times (on approach) that we are tuned in to the speed and very aware of the stalling numbers. There are other times that we are busy with other things and least expecting a stall - that is when the buzzer or light earns its keep. I recall two occasions that the red light on my Cherokee Six started talking to me immediately after take off - only in retrospect did I realize that the conditions on the day (runway length, DA and MAUW) gave rise to marginal conditions that required very careful handling for the first few seconds after leaving ground effect. The red light however put me on full alert - one eye on the ASI, ball dead centre, easy on the stick and no turns. I do not recall the deck angle (fair indication of AofA) being anywhere close to what I would see when practicing stalls. Who knows what.....? The variations of stall alerts that I have experienced: a) the Piper /Beech type vane on the LE and b) the early Cessna "flute" type. Both physically detect when the airflow is getting close to breaking up at the LE - and that is the approach of an actual stall (no matter what else) and that is the warning I want. Both devices report ACTUAL airflow conditions in "their" area - the area just before the known stalling (break-away) point. The vane or flute is telling you that their "local" conditions are stall conditions - and if you allow these local conditions to move another half inch father north, you will stall (that wing?) - irrespective of anything else, air speed, AofA, price of beer. Maybe it is possible to extrapolate these conditions from AofA, but will AofA take into consideration the slip (or skid), gusts etc? Think of the slats on a Tiger Moth - same principle, they move (are sucked) out when conditions approach the stall. A clear indication of the effectiveness (sensitivity) of this action is demonstrated by the fact that one slat will often pop out (and back in) without the other side moving at all - maybe due to a gust or maybe the driver did not have the ball in the centre. Never thought about it before, but it would be constructive to go out and fly steep turns in both directions with a bird that has stall warning. Is there a bias in the SW reporting with a device on one side only? Maybe first prize would be a stall sensor (slat or flute) on both sides. There is no doubt that installing one on a KR will require fiddling, Adjusting, calibrating - that can be done deliberately and safely at altitude. Once it is set up - the builder /pilot will know exactly what it is telling him (how much lee-way etc.) Have a great week Steve J
