I previously discussed the symptoms and indications of a stall, leading to my opinion that in respect to stalling, prevention is better than the cure. However, recognition of these symptoms in the real world is not always that easy.
A student pilot may one day find themselves in an aeroplane that is no longer generating lift – it has stalled. The symptoms (high nose attitude, sloppy controls, low and decreasing airspeed, stall horn and light buffet) have given way to heavy buffet, nose and/or wing drop, and an increasing rate of descent. Your aircraft has stalled.
I cannot emphasise enough – in real stall situations where the stall is unintended, pilot distraction due to high workload or aircraft malfunctions will mean stall indications are easier to overlook or misinterpret. For example, at high level even a highly automated aircraft has the ability to confuse a pilot. Loss of airspeed indications may result in both over-speed and stall warnings at the same time, while pre-stall light buffet can be confused with high speed buffet, and all airframe buffet may be masked by turbulence. It is situations such as this that the incipient stall recovery I discussed last week must be applied – set and hold a known attitude for performance and set climb power or a known power (depending upon where your are encountering the incipient stall) to give a required speed. The aircraft will continue to fly at a known attitude and power – and thus you avoid the fully developed stall. But if you do stall what must be done?
In stall practice situations, the student pilot on recognition of entry into a fully developed stall (nose and/or wing drop, heavy buffet and high rate of descent) applies the standard stall recovery. Simultaneously the pilot lowers the nose to unstall the wings and applies maximum power, countering the yaw due to power application with rudder. Once unstalled, level the wings with aileron, adopt the climb attitude and once stable and safe, complete the post loss of control checks.
What are you aiming for in a stall recovery? While initially the instructor may use an aircraft attitude as an end point for the student to achieve when lowering the nose to unstall the wing, this is misleading in some respects. The aim is to unstall the wing, not simply lower the attitude. If your instructor simply gets you to look out the front and achieve an attitude in order to get out of the stall, and does not discuss unstalling the wing and what that feels like through the controls and its effect on the aeroplane, he/she is not doing their job properly. The stall buffet must stop. Often I have seen students lower the nose to a given attitude, and once there they have assumed the aircraft is unstalled, completely missing the fact that we are still in light buffet and the wings are stilled stalled. Any increase in the angle of attack and guess what, back into a fully developed stall – leading to more height loss.
So, unstall the wing, whatever the aircraft attitude or angle of bank is. The stall buffet must stop. This can be demonstrated by an instructor who keeps the aircraft at the point of stall by lowering and raising the nose, exiting and re-entering the fully developed stall in a controlled way. The student is then able to feel what unstalling the wing is like and this can be done over and over again in order to re-emphasise the point at which the wing is not longer stalled.
Another important aspect to the fully developed stall recovery is the application of aileron to prevent further wing drop. Some aircraft tend to drop a wing in the stall. The AP3C Orion stalled wings level beautifully – unless the skidball was not balanced. Enter a stall unbalanced and wing drops of 90º were not uncommon. In most aircraft counteracting this wing drop with the application of aileron, while it seems logical to do, is wrong. Think about it – to recover a wing that has dropped the application of aileron increases the angle of attack of that portion of wing affected by the aileron. Most aeroplanes stall from the wing roots out to the tips. This is, amongst other things, in order to have aileron effectiveness right up to the point of stall. However, a rapid application of aileron IN the stall may simply increase the angle of attack of the down-going wing, bringing the wing into a deeper stall, increasing the rate of roll.
Therefore, if a wing drops during a stall, while simultaneously lowering the nose to unstall the wings and applying maximum power, use rudder to prevent the nose slicing too far below the horizon due to the angle of bank. Leave those ailerons and the angle of bank where they are! This is hard but get an instructor to show you it actually works. Once the wings are unstalled use aileron the achieve wings level and then adopt the climb attitude.
Stalling and stall recovery is a skill every pilot, from a Cessna to an Airbus driver, needs. However, recognition that your aeroplane may be about to enter a stall is equally as important. Get out there with an instructor and stall. One day your life and the lives of your passengers may depend upon it.