There is ONE fatal mistake that pilots make, again and again. I sincerely hope that reading this article will ensure you are NEVER ONE OF THESE PILOTS!
The mistake is a rookie error, and is fatal with an insufficiency:
Not enough AIRSPEED
Height is your friend in flight. Height allows you TIME to fix an error. The problem is that those who make fatal airspeed errors usually do so at low altitude, when they have to act VERY QUICKLY and CORRECTLY or they have NO CHANCE to correct the error before they hit the edges of the sky, (more commonly referred to as the ground). Stopping very suddenly from high speed is an efficient way to eliminate breathing permanently.
Another fatal student accident on 8 October 2018 at Grand Central, Gauteng, happened when a solo student, in the circuit, at the same point in her training as the above student, was asked to orbit on downwind, for traffic spacing. She ended up in a spiral dive, corrected that, but neglected to climb back to circuit altitude. She flew so low that, when approaching a tree in someone's yard, she pulled up suddenly, stalled, and the starboard wingtip dropped. She crashed into the garden of the house next door, killing herself, and the gardener, who died a bit later at the scene of the accident.
Another accident fatality 24 Oct 2020 in KZN, still under investigation at the time of this writing, so it will be kept anonymous, was a light sport pilot, taking off from a short, well maintained grass strip on the edge of a gorge.
The cause of ALL these fatal accidents is because of ONE main factor.... the wingtip stalled.
The recipe to stall a wingtip is a gentle bank, (slowing your airspeed) and with your ball out of balance in a climb or descent.
When a wingtip stalls, and your wing drops suddenly this is called an incipient spin. It is the very first phase of a spin. It is easy to lose up to 500ft recovering from a wingtip stall.
You correct this by INSTANTLY doing something counter-intuitive.
You LOWER the aircraft nose to the glide attitude and apply the rudder opposite to the dropped wing very sharply while keeping the ailerons neutral.
If you have power on, close the power immediately to avoid racing to the ground faster when your wing tip un-stalls in the recovery. Adding power before un-stalling the wingtip raises you aircraft nose, and can put you into a secondary stall. If already in a spin, adding power will put you in a flat spin and prevent recovery from the spin.
Lowering the aircraft nose to the glide attitude decreases the angle of attack, breaking the stall and allowing the wing tip to once again generate lift. Applying opposite rudder uses the further effect of the rudder to lift the wing - primary effect - YAW, further effect - ROLL. This further effect brings your wings level. Keeping the ailerons neutral prevents the aileron on the stalled wing from increasing the angle of attack on the stalled wing, which would deepen the stall and speed up rotation in the spin.
You will easily lose 500ft in this recovery. Instinct will tell you to pull back and use the ailerons to turn opposite to the dropped wing. This instinct will cause the stall to deepen and the spin to develop faster.
The girl in the first accident should have been somewhere between 800ft and 1000ft minimum on the turn. Quick correct action could have saved her life. Nose forward, opposite rudder, regain speed, add power and level off or climb. The second and third accidents were from much lower. They did not stand a chance once the wing dropped.
YOUR AIRCRAFT CANNOT FLY WITH AIRSPEED IT DOES NOT HAVE
Stalls are related to airspeed because airspeed is related to attitude. Exceeding the critical angle of attack on the wing tip, (stalling that outer portion), will cause that wing tip to drop like a stone. Your stall speed will vary depending on many factors, aircraft weight, wind, density altitude, pilot inputs, (sudden changes), power setting, bank angle, rudder position in the bank. You can stall at both a high and low speed. Your aircraft does not stall at a particular speed, it stalls when the critical angle of attack is exceeded, causing the airflow to break away from the aerofoil, which results in an instant loss of lift.
Although stalls happen when the critical angle of attack is exceeded, we can stay far away from a stall if we keep flying at a safe speed, and make smooth, co-ordinated control inputs. None of these accidents would have happened if the pilots kept enough air flowing over their wings. An accident like this is EASY TO AVOID.
In a descending turn, the speed tends to bleed off, so ALWAYS lower your nose attitude when you turn while descending. When you straighten up, check back again. This ensures you are on the safe side. The amount you check forward and back depends on your bank angle. Medium turns, the motion is slight. Steep turns you need to get into a more dramatic nose down position when you turn in the descent.
“Learn from the mistakes of others. You won’t live long enough to make all of them yourself.”
Here are the mistakes each pilot made:
The Wonderboom accident
She was flying a Piper Cherokee 180. The Cherokee has a wing dihedral. In a descending turn, the lower wing is at a greater angle of attack. The dihedral amplifies this effect towards the wing tip. Your wing root or wing tip will ALWAYS stall when you exceed the critical angle of attack. This is a guarantee. The exact airspeed this will happen at varies based on many factors including your aircraft weight, your power setting, and your aircraft attitude.
Although the official report is not out at the time of writing this, an educated guess is the young pilot, turning base, and focusing on finding the runway, did not notice she was pulling back the control column in her turn on base, and in so doing, was slowing down her airspeed in the turn. She possibly also had her rudder out of balance, most likely port rudder, skidding out of the turn - pressing too hard on the port (left) rudder and pushing the ball past the center. (It was her third SOLO circuit session).
How could she have survived? First... pay attention to airspeed and the balance ball. Failing that, the only action that could have saved her was check forward, opposite rudder... neutralize rudder, stabilize level and apply power. Climb. She had very little time to take this action.
The Grand Central accident
It would appear her situational awareness was not quite up to par. Her training reports also stated she had a tendency to freeze on the controls. After recovering from a spiral dive on downwind when she was supposed to be orbiting, she leveled out low. Flying at approximately 90° away from the runway towards a suburb, she pulled back abruptly to avoid a tree, exceeding the critical angle of attack with the sudden change in direction. Because of inertia, the airplane does not change direction as quickly with a sudden input, especially if you have a crosswind or tailwind. This alone could have caused her to exceed the critical angle of attack. It was a training aircraft, so the rigging was probably not 100%, and in the stall that followed her starboard wing dropped. Most training aircraft have a tendency to drop a particular wing in the stall. She did not have enough height to correct the stall.
The KZN accident
The pilot took off downwind, and did not use all the runway. Witnesses say the aircraft engine quit, (it appears it was not an engine fault), and the pilot tried to turn left back to the airfield. His port wing dropped suddenly and the aircraft descended nose down, leaning over backwards slightly and it was all over in a few seconds. He did not have enough height to correct the stalled wingtip. He could have glided down the gorge and landed in a field below, maintaining his take-off direction. They might still have been hurt, might not have, but stood a better chance of survival if this action had been taken. The wait for recovery would have been inconvenient.
Have you ever heard your Flight Instructor say :"NEVER turn back to the airfield on your take-off leg?" That's because it usually ends badly.
Stall speed INCREASES in the turn
In the video that follows, the pilot made the same mistake as our KZN pilot, although this was not after take-off. Here he does a low pass, zoom climbs, which slows his speed. Then he turns to come back to the river, most likely intending to do another low fly-by. His speed would still be fairly slow. You can see where he steepens his bank angle in the turn, one would surmise to line up before the men in the boat. This is where the wingtip stalls and the wing drops suddenly as the spin begins. He did not have enough height to recover. If he had dropped his aircraft nose as he tightened the turn, to increase his airspeed, he might have got away with this maneuver, but alas, he did not. Dipping the nose here would make one drop towards the ground quickly.
A safer option for him would have been to give himself more space for the turn. Your stall speed INCREASES in the turn, i.e. you stall at a faster speed.
Your GO-TO Correction
- Slow Speed with sudden wing drop (this is an incipient spin)
Correction - Check FORWARD (not much), & apply OPPOSITE RUDDER to dropped wing, power off, then get your wings level, ball in the middle and bring your aircraft level while applying power.
Incipient spins can happen when your nose is high, full power (or partial, or none), usually in a slight bank, and often with rudder slightly unbalanced. They can happen in a descending turn too. They can happen in a steep turn at slow speed. Remember, your aircraft stalls at a HIGHER airspeed when in a turn!
Any time when your critical angle of attack at the wing tip is exceeded, this wingtip will stall. It will then drop suddenly giving you a heck of a fright. Your natural reaction, to pull back on the stick and use the ailerons to lift you out of the turn will have the opposite effect, your stall will deepen and your turn will tighten. Without height, from below 1000ft, you have 2 - 6 seconds before you hit the ground.
“Good judgment comes from experience. Unfortunately, the experience usually comes from bad judgment.”