Did airline's bar on hard landings force a pilot 'error'?
timesofindia.indiatimes.com
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.
Capt Z Glusica was popular among his first officers as he allowed them to do landings under his supervision. "Any commander with the kind of experience that Capt Glusica had can safely allow a first officer to land. But the AI Express air safety department is set against it. If a first officer never learns to land under the supervision of an experienced commander, how will he handle a situation if for instance the commander gets incapacitated?" asked the source. "Even if we assume that it was the first officer who touched down late then all that the commander had to do was do a go-around (i.e., take off again and come around for a second attempt at landing) and the aircraft would have landed safely," the official said.
A B737 aircraft can safely do a go-around after touchdown. But it cannot do a safe go-around if the decision to do a go-around is taken late or if it is taken after the reverse thrusters have been deployed (thrust in the opposite direction so as decelerate the aircraft). A go-around after thrust reversal selection is prohibited. "The airline policy is such that pilots try to avoid go-arounds as they have to explain it to the air safety department. A go-around infact is a highly recommended safety procedure when the touchdown is deep. But due to the airline diktat, the commander must have had a few microseconds of indecision after the aircraft touched down. So he seems to have either opted for the go-around late or he did it after deploying reverse thrusters. Since the go-around attempt failed, this is a plausible explanation," said the source.
There are unconfirmed reports that the plane's nose wheel burst after touchdown. It is difficult to bring an aircraft to a halt near the end of a runway as this portion bears aircraft skid marks and rubber desposits which affects braking action. When the plane attempted to lift off again the aircraft's wing hit the localiser (a T-shaped frangible antenna positioned perpendicular to the runway central line and located about 150 feet from the end of the runway) and then plunged into the valley. "Since the wreckage was well off the runway one can say that there seemed to have been an attempt to do a go around. Only investigations will reveal why did the attempt go wrong," says the source.
The pilots also brought in the fatigue angle to explain the wrong decisions taken by the pilot. "It does not matter how many days rest he got prior to these flights that he operated. He took off from Calicut on Friday night for Dubai and then came to Mangalore. The entire operation was done at night, during circadian low. His alertness level at the end of that 9-10 hour night duty surely would not have been very high," the pilot added. For the last three years, pilots of Air India, Indian Airlines and Jet Airways have been pushing for better pilot rest rules in India. Currently, the rest rules followed are the ones formulated in 1992.