The SkyStar Series 5 pilot reported that while on short final about 20 feet above the ground at the airport in Green River, Utah, he noticed the “attitude was a little flat.”
He added the airplane lost altitude “so fast, he didn’t have time to react or even think to put the nose down or add power.”
The plane hit terrain, which resulted in substantial damage to the left wing.
The pilot reported that his conclusion as to why the accident occurred was that the airplane “flat” stalled about 15 to 20 feet above the ground because he was “so focused on hitting the front of the runway” and didn’t keep the airspeed “up.”
Probable cause: The pilot’s failure to maintain pitch attitude, which resulted in the airplane exceeding its critical angle of attack and a subsequent aerodynamic stall/spin.
NTSB Identification: GAA15CA257
This September 2015 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
One of the questions on my pilot exam test was: “An airplane can stall at any air speed”, true or false. Of course the correct answer being “true.” I remember my flight instructor telling me an airplane can stall at mach 2.
Inadvertent stalls happen most often at low air speed because a pilot may increase angle of attack to maintain altitude rather than add power and subsequent air speed. In this case, the pilot admitted he was trying to reach a point on the ground.
After critical angle of attack is passed (around 16 degrees) lift collapses due to airflow separation, causing a stall.
The reason some think airflow is the culprit in a stall is due to the separation element. But that separation only occurs when the wing exceeds critical AOA.
Neither of the two previous responders has ever had the wing’s lift pulled out from under them just above the ground. I learned to fly at San Carlos airport just south of SFO. It is a rare day when there is not a cross wind, sometimes good and strong. Also, the buildings and slough right at the approach end of 30 makes for a very likely abrupt burble just before the threshold.
I was lucky to have learned to fly there, every approach is a go around until proven otherwise, and sometimes proof is later than you think.
I have had the lift of the wing pulled out from underneath me. Just like a rug. I was lucky enough to react quickly enough and yanked the nose up for the mains to touch first. My instructor was in the right seat. I was not slow on the approach. We guessed it was a drop from a bit less than 10 feet.
If you are 10 kts above stall, in a 15 kt head wind and the wind shifts and you instantly have a 4 kt headwind component, you will stall. Bob and Bart need a little more experience.
As I said, I was lucky to learn at SQL.
Plenty of experience here. What you experienced wasn’t a stall it was wind shear. Completely different conditions and yes more speed does mitigate that. But as you said it’s a unique situation at some airports or any airport on some days. You don’t fly expecting wind shear on every landing.
What Glenn described is wind shear causing a stall. If wind shear causes you to suddenly go from 10 kts above stall speed to 1 kt below stall speed, you get a stall.
NO YOU DO NOT! Stall isn’t caused by speed its caused by high AOA. Wind shear will cause the airplane to lose, or gain, altitude and it will affect the amount of lift the wing makes, which is related to AOA, but it is NOT A STALL. If the wind speed changes dramatically to more headwind the airplane will gain altitude at the same IAS and AOA. If the wind shear is a tailwind the wing will lose lift at the same IAS and AOA but its not stalled. Wind shear is a momentary condition you experience frequently at altitude but the only time its hazardous is at low altitude. Again, more speed is the way you address wind shear not a stall. The wing will stall ONLY at high AOA and it will do so at any speed and in any attitude. By the way, just to add fuel to this OWT about stall speed, the wing will not stall in ground affect. So if you’re a wing span or less AGL and the airplane falls out from under you it isn’t the result of a stall but simply a high drag, high rate of descent condition you didn’t catch soon enough.
I put my comment out there for other people to learn from. The fine line of definition between stall and shear at landing means very little to me, personally.
In the mean time I will move on, now 20+ years later, knowing I didn’t stall that night at SQL. I sheared. Much better than shredded.
I haven’t been there, but it looks like the topology around U34 could give some squirrly winds on approach as well.
Glenn, learning from other pilots is why most of us comment on these threads so kudos to you for doing so. On the other hand if you don’t learn from the experience of others its kind of pointless don’t you think? There isn’t “a fine line definition between stall and shear”, they are completly different conditions and require different applications of power and control. It’s apprarent you’re still stuck in the OWT about airspeed and stall prevention, that’s a shame because the day may come when the difference between the two may manifest itself with a less than optimum outcome.
a shame the day may come …. A lot of arrogance there pal.
Completely different conditions. … So you have not experienced it yourself
Don’t learn for the experience of others …. there goes that kettle again
Getting this one of my chest now, I have run into people like you in aviation. I won’t have anything to do with them.
Sorry Glenn, I didn’t mean to push your buttons. I have experienced what you did, many times, as I fly a lot in West Texas and Colorado where wind shear is a constant reality. That doesn’t alter the fact that I know the difference between wind shear and a stall and the fact that you respond to each in a different way.
Ive run into guys In aviation who know what they know even when it isnt’ true and they are essentially untrainable beyond the very basics of controlled flight. Like you I avoid them.
I know what you mean. It’s pointless to argue with people who are characteristically untrainable, don’t you agree?
There is only one way to stall an aircraft.
Stall occurs when attaining the critical angle of attack!
The only way a positive stable aircraft can pitch to that angle is by the pilot pulling and holding it to that attitude…”The Pilot Stalls the Aircraft!!!”…every time, no other way it can happen.
And once again we promote the myth that stall is related to airspeed! The wing stalls because of AOA not airspeed. You hold the AOA control in your hand, pull back and increase AOA release back pressure and AOA decreases, simple and nothing to do with airspeed. Doesn’t matter if you’re at 5000 ft or 50 ft AGL, doesn’t matter if wings level or 60 degree bank, airspeed has nothing to do with stalling the wing. We perpetuate this myth by training and practicing wings level, power off “stalls” and devise a “stall speed” based on that configuration alone then beat that number into the heads of student pilots until they’re terrified of the low end of the ASI then wonder why they keep stalling out of turns on base to final and need 3000 feet of runway to land a 172.