Stalls

Lastly there was the AirAsia flight QZ8501, an Airbus A320 that crashed into the Java Sea on December 28, 2014.

The last accident is still under investigation but there is a common thread to all four. Stalling.

One has to note that as in most air accidents there is a series of events that led up to accident – the socalled Swiss cheese effect with all the holes lining up to allow the path to the final outcome.

Now the stuff of this column is not normally airline flying but the fact that commercial pilots have to start somewhere and instructors teach students who eventually go on to fly airline aircraft makes comment relevant.

In the case of Air Midwest the accident was decreed asbeing a stall after takeoff due to overloading and maintenance error.

The aircraft had previously taken off from another airport to get to Charlotte but on the accident departure the centre of gravity was beyond the aft limit and this coupled with an over gross MTOW and a maintenance issue that reduced the down elevator angle all led up to a low-level stall.

The Colgan Air accident was said to have been caused by the aircraft stalling due to ‘inappropriate inputs’ coupled with possible fatigue.

The crew had been waiting at the departure airport overnight and all day before the 9. 18 pm departure.

The Air France Airbus A330 entered a high altitude stall from which it did not recover and it impacted the ocean.

The investigation of the AirAsia A320 accident is continuing, but from information so far released it would appear that the machine had climbed at an abnormal rate and at a speed that ultimately led it to stall and possible spin before it impacted the Java Sea in the Karimata Strait.

A pilot must be able to recognise the stall

Certainly there were a series of compounding factors in each event that led to the final outcome. But in all four events there were indications of the impending stall that went unrecognised and uncorrected in time to recover the situation.

All the pilots were qualified andperiodically checked and yet all the aircraft stalled and crashed with the loss of life of passengers and crew.

One has to wonder how this came to happen.

The stall manoeuvre as taught at flight school is one that most students are uncomfortable with. They typically have the motto ‘stall, spin, crash and burn’ fixed into their brain by various external sources. The end result is that they approach the stall exercise with a degree of apprehension and the thought of how quickly can they get this over with. If those students go on to become flight instructors then they will carry that thought with them and so their students will have less than the desired exposure to stalls.

Now the stall is just one part of that flight exercise. In an ideal world the student will be exposed to slow flight and the approach to the stall. Then recognition of the impending stall and the actual stall itself followed by the recovery.

Exposure to slow flight is needed to allow the student to becomecomfortable with and aware that the aircraft is not flying at its optimum performance. The student needs to be aware of the issues of slow flight and how to recover and resume normal straight and level flight. If the slow flight is followed by moving towards the stall then the student needs to be aware of the symptoms of an impending stall. Typically these are a decreasing airspeed, sloppy ailerons, heavy elevator, quiet cockpit, reduced power, the stall warning device, a high nose attitude and with low-wing aircraft, buffeting from the broken air stream flowing from the wings and passing over the tailplane (albeit some do not apply to an airliner).

Then there is recognising the actual stall itself, usually a dropping of the aircraft nose often accompanied by a wing drop, an incipient spin. The pilot then needs to take corrective action and recover with minimum height loss.

Simple! But not seen that way by some students and even licensed pilots. It is not unusual for students practising stalls to bring up their lunch as a result of the level of apprehension. Pass the flight test they may but they still carry that fear of the stall and all that it embraces with them. So when put into a situation of an inadvertent stall they are slow to recover and, as has happened, to actually worsen the situation by misidentification with resultant incorrect control inputs.

Being able to recognise a stall and recover with minimum height loss is an essential part of a pilot’s basic flight education.

As flight instructors we need to pass our level of confidence and knowledge to our students so that they take that away with them.

We need to ensure that the pilots we train are able to cope with slow flight and stalls as the pilots who we train today are the airline pilots of tomorrow.

Stall type accidents we do not need.