[http://upload.wikimedia.org/wikipedia/commons/b/bf/1985-06-10_VT-EFO_Air_India_EGLL.jpg] 30th September 2012
Air India 855 exemplifies how a sensory human factor can contribute to an accident. It was a scheduled service offered by Air India between Bombay (Mumbai) and Dubai (UAE).
Sequence of Events
On January 1st 1978 Air India Flight 855 departed at 20:40 from Chatrapati Shivaji International Airport. The aircraft was put into a right climbing turn. When Capt. Kukar rolled wings level his Attitude Indicator had become frozen indicating right bank. The captain mentioned out loud ambiguity with his A.I however the first officer did not think much of it and said that his A.I was fine and had toppled but had not settled yet3. Thinking the aircraft was still in a right turn Kukar corrected by banking to the left when actually the aircraft was flying level. In doing so he had unknowingly put the aircraft into a left turn which kept increasing as he kept correcting. In climbing turns a combination of increasing angle of bank and decreasing airspeed will, if not corrected, lead to a stall. The aircraft bank increased to the point where it stalled and crashed4.
The situational factors at the time included a critical stage of flight at night under instruments. Sensory human factors were the primary cause of the accident because instrument flying requires pilots to trust their instruments as there is no visual horizon. Since there was no horizon for the pilots to use and their main source of a horizon was faulty, the sensory information received had caused the captain to lose situational awareness of the aircraft’s attitude. The captain could have used his turn coordinator and airspeed indicator to see if the aircraft was actually in a turn or not while the co pilots A.I settled or he could have checked with the third spare A.I4.
The cause of the accident was determined to be the captain losing situational awareness after the A.I had failed and the subsequent irrational inputs on the controls. This along with the crews inability to recover lead to the aircraft stalling in a turn and losing height that could not be recovered.
Prevention of future occurrences
Prevention would include implementing cockpit procedures where one can speak up without the fear of repercussion from the captain. Especially in countries where cultural etiquette makes its way into the cockpit1. There are always more than one attitude indicator in an aircraft, rules can be put into place so that if an instrument has failed, the backup should be used. Also there are always other instruments that can be used to judge the aircraft's attitude such as the airspeed indicator, if the air speed is decreasing then that would suggest that the aircraft is in a climb, looking at the Vertical Speed Indicator would also aid in understanding what the aircraft is doing. The turn coordinator and balance ball can be used to judge whether the aircraft is in a turn. Had the captain not reacted straight away and looked at other options then perhaps the outcome could have been different.
1. Ewing, R.L. (2003) Aviation medicine and other human factors for pilots. (5th ed). Christchurch: Old Sausage Publications.
2. Reason, J.T. (1990). Human error. Cambridge, England: Cambridge University Press.
3. Wikipedia (2012). Air India 855. Retrieved September 30, 2012 from http://en.wikipedia.org/wiki/Air_India_Flight_855
4. Aviation Safety Network. Air India Flight 855. (n.d.). Retrieved September 27 , 2012, from http://aviation-safety.net/database/record.php?id=19780101-1
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