Southwest Landing Gear Collapse At LGA

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July 27, 2013

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Clearly landing gear are not supposed to collapse on landing.  While this is an unusual event, it is not unheard of, even in airline operations.  So what could cause the nose landing gear to collapse as apparently happened to the Southwest Airlines Boeing 737 on landing at LaGuardia Airport yesterday afternoon?

Let’s review for a moment how the landing gear is extended on approach.   As everyone who has ever flown in an airplane knows, the landing gear is extended by the flight crew well before touchdown on the runway.   The noise associated with the lowering of the landing gear is well-known to most flyers.  Airplanes have warning systems which will advise pilots whether or not the landing gear has rotated to the down position and is in fact locked in place. These systems have proven to be extremely reliable.

So while a malfunction in the warning system could occur, it would be a rare event.  If the landing gear is not down and locked, warning lights would illuminate in the cockpit, advising the crew there was a problem.  In that case, the crews would advise air traffic control of the problem.  Despite confusing initial reports, it now appears that the crew did not advise ATC of any problems which would indicate to me that no warning lights illuminated in the cockpit to warn of a landing gear problem.

On landing, the main landing gear – the two legs in the rear – touchdown first and those legs are designed and manufactured to take the tremendous stress of the weight and speed of the aircraft making contact with the ground.  The full weight of an aircraft – which for a 737 could be over 100,000 pounds -has to be supported by those legs.  After the main landing gear is in firm contact with the runway, the flight crew lowers the nose and the nose gear contacts the runway.  This occurs at the same time – or about the same time – as the brakes are applied.  This is usually felt by passengers in the cabin as rapid deceleration, pushing passengers forward in their seats.  This same forward motion applies to the nose gear as a downward pressure causing even more stress on the nose landing gear.

Based on news reports and photos of the aircraft, it seems to me that the most likely explanation for what occurred at this point is that the linkages that allow the nose landing gear to retract up into the aircraft after take-off failed under the landing load.  The reason for their failure – if that is in fact what occurred – will require detailed analysis.

This article originally appeared on Forbes Logistics


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