Sunday, March 21, 2010

My opinion about displaced thresholds and landing

Most of my friends who are pilots will not touch down prior to a displaced threshold.  Even if it means leaving more than 3,000 feet of runway behind them.  Runway 31 left at JFK is a good example.

 I recall my very first flight instructor repeating the axiom of the three things a pilot cannot use.  They are the altitude above you, the gasoline in the gas pit and the runway behind you.
There is no regulation that prohibits landing touch down prior to the displaced threshold. Most pilots apparently believe there is one.  I personally, have touched down prior to many displaced thresholds at many different airports in the USA.

My opinion about touching down prior to a displaced threshold had its beginnings many years ago.  I was awaiting departure on runway 31 left at JFK when I watched a British Airways Lockheed L-1011 take off.  Shortly after lift off, he announced he had an engine failure and declared an emergency.  The weather at the time was 5,000 feet overcast with light drizzle.

He proceeded to fly a left down wind leg to runway 31L which has a marked displaced threshold 3,324 feet from the end of runway 31L.  He touched down well beyond the displaced threshold at about point I estimated to be 5,000 feet from the end of the runway.  I watched as he applied the brakes and smoke began to emanate from them early in the landing roll.  Apparently he was landing at a weight in excess of maximum landing weight.

He was successful in stopping just before he reached the end of the runway and turned off to go to the gate.  I thought sure I was going to be witness to an over run and possibly an accident and was much relieved as a result.  That incident started me to wondering why an airline pilot would leave so much good runway behind him in this situation?

After much discussion with my fellow pilots and thought, I concluded he was conditioned to landing beyond the displaced threshold without giving any serious thought about doing it.  This conditioning occurred as a result of observing so many pilots doing that every day.  If you go out to JFK today and runway 31L is the active landing runway you will get a chance to watch pilot after pilot doing the same thing.

One of my first considerations was to ask the question "Why is the runway 31L threshold displaced for landing?  The answer is for noise abatement reasons.  Isn't noise abatement supposed to take a back seat to safety? Of course it is.  I also discovered in my research the present displaced threshold was put in place many years ago prior to the present much quieter jet aircraft being placed into operations.

See Part II above.

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