document.write(" serif">Today's News
NTSB Chairwoman Deborah Hersman continues to impress. Quoted today in the San Francisco Chronicle, she says: “What I'm telling you is that from 500 feet to 100 feet, there is no mention of speed.” That's on page A10. On page A12 there are two articles, Do pilots have adequate skills? by airline pilot James F. Atkinson, and When will FAA require alerts? by lawyer Robert A. Clifford. (I am not including links to these articles because you would have to be a Chronicle subscriber to read them.)
Atkinson rightly addresses basic flying skills and airmanship, pointing out that today's automated systems actually undermine skills. Clifford calls for mandatory low airspeed alerts, missing the point that this would make the pilots even dumber. (It is worth analyzing the terrific save by the captain of the Quantas A380 that had the uncontained engine failure. There was so much damage and so many (hundreds) of ECAM alerts that he finally said, Stop ECAM. Lets go backwards and just see what we've got left. That critical decision was the key to saving the airplane.)
Analysis of the Last Minute
At 1000 feet, 54 seconds before impact, someone says, Sink Rate. The throttles are at idle. The training captain tells the trainee, who is flying the airplane, to pull back. This is exactly the wrong thing to do. We will explore why that is so in greater detail in another post, but for now we'll say that they were at idle, on the back side of the drag curve, so total drag is increasing with angle of attack. As any pilot knows (see Stick and Rudder, 1944), instead of correcting the sink rate, pulling back on the control column actually increases the rate of descent and causes the speed to decay faster and faster.
At 200 feet, 18 seconds before impact, the training captain realizes they are too slow and moves to engage the autothrottle. After saying pull back he does nothing for 36 seconds while the airplane descends at over 1300 feet per minute. The target for any approach is 700 feet per minute. The engines are still at idle. They are well below approach speed.
Could they have done a missed approach that point? I will leave that for formal analysis, and point out only that these aircraft are designed to be able to do a baulked landing from any point before touchdown, but only if the engines are already spooled up and the speed is at approach speed, about 1.3 times the stall speed.
Ten seconds later, it was already game over. Perhaps the autothrottle had been armed, but most likely it had not actually been engaged, so thrust lever movement happened only now, at about 100 feet and 8 seconds before impact. And it will be another 5-7 seconds before the engines develop any useful power. So we see the slowest speed at 3 seconds before impact, at perhaps 40 feet above the water. This is where the passengers behind the wings see the plumes of water as the engines start to spool up. Meanwhile the stick shaker is going, indicating impending stall. Despite pulling back and belatedly adding power, they are still descending at 750 feet per minute, by my calculations. This is the first time anyone in the cockpit calls for a go-around. Of course it is too late. Way too late.
What the training captain should have done, back at 1000 feet and 54 seconds, is push the power up. Manually. With the thrust levers. The problem is that he would probably not been able to stabilize the approach from the idle thrust, slow (148 knots) and 1300 feet per minute sink rate descent. It would have been a neat parlor trick if he could have put on go-around thrust, pushed to counter the nose-up moment of the added thrust and bring the speed back up to bug (the approach speed), and then quickly brought the power back to approach power and held the speed. At 1000 feet he had room to fart around a bit, at least in theory. But airline Standard Operating Procedures (SOP's), his own airline's included, say that the approach must be stabilized by 1000 feet and remain stabilized, or else a go-around shall be performed.
So what the training captain really should have done is to say:
I have control.
That's it. That's the last time the training captain, the Pilot in Command, had any say in the matter. That's when the pilots, the crew, gave up having any influence over the outcome.
It is sad, but true. It must be said. The pilots were incompetent.
Next: aerodynamics they should have understood . . .