Did airline's bar on hard landings force a pilot 'error'?

Mumbai: Air crash investigators worldwide share a belief__that the initial reports on the probable cause of an aircrash usually turn out to be untrue.
The Air India Express top brass would do well to hope that this bit of industry wisdom holds true in the Mangalore aircrash case too since initial reports from aviation circles point at pilot error arising out of the management's highly controversial policies.
According to sources, the AI Express Boeing 737-800 aircraft touched down deep on runway 24 of Mangalore airport, much beyond the stipulated touchdown zone. Why would a senior commander miss the touchdown zone and hit the runway? Here's where the airline management's involvement comes in. There is a diktat for Air India Express pilots which bars hard landings. A circular issued by the airline about a year ago says that landings should not exceed 1.65G.
What is a 1.65G landing? When the undercarriage of a plane touches down on the runway, the sink rate goes from say 200 feet per minute to zero feet per minute in a few seconds. So for a higher sink rate, the impact on touchdown is greater and vice versa. A hard landing typically occurs when the sink rate is high and the aircraft touches down on the runway with a thud instead of doing a smooth transition onto ground.
The hard or smooth quotient of a landing is expressed in a term called "touchdown G". A 1G landing means the force which acted on aircraft tyres at the instant of touchdown is equivalent to the weight of the aircraft (1 x aircraft weight). A 2G landing would mean the force is two times the weight of the aircraft. Higher the value of G, harder the landing. The AI Express circular limits landings to 1.65G, though according to the aircraft manufacturer Boeing's specifications the aircraft can safely handle up to 2.5G landings.
"Every time a landing exceeds 1.65G, the pilot gets hauled up by the air safety department. Two hard landings and the pilot is sent for a training session. Passengers also complain about hard landings and so the airline is particular about smooth landings which are achieved with lower touchdown G values," said a source. Now, one of the ways to achieve a smooth touchdown is to come over the runway at a higher speed and float for some distance before letting the landing gear touch down on the runway. This reduces the G force on impact. "Pilots often land a few feet ahead of the touchdown zone when they float over the runway to make a smooth landing," said a source. "The AI Express commander too seems to have employed these tactics. His aircraft missed the touchdown point," the source added. What the commander executed was a late, smooth touchdown at high speed. "‘It is indeed pilot error, but it is an error that was forced by the management policy for smooth landings. A hard landing may be an uncomfortable landing, but sometimes it is a safer landing than a smooth landing," the source said.
23/05/10 Manju V/Times of India

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