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On commercial airliners, the FCOM (Flight Crew Operating Manual) sometimes gives instructions to the pilots to land sooner than planned, following various in-flight failures or emergencies. For instance, for serious emergencies (e.g. in-flight fire), the pilots would be instructed to LAND ASAP (as soon as possible), as there is a real danger to the aircraft and its occupants if they stay in the air any longer.

For less severe situations, the pilots would be instructed to LAND ANSA (at nearest suitable airport), which gives them more leeway in deciding where to land.

My question is: other than the fact that LAND ASAP is obviously more urgent than LAND ANSA, could anyone go into more details as to how a pilot would interpret these instructions, and how they differ? (for instance, does LAND ASAP mean "land on the nearest reasonably smooth surface", or is it less extreme than that? Are there guidelines on approximately how long you should keep flying after receiving a LAND ANSA instruction?)

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    $\begingroup$ In the planes I fly, ASAP means pick the open field in your vicinity which is least likely to kill you and land there. Don't know this applies to airliners though. :) $\endgroup$ – falstro Jun 19 '14 at 8:28
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I would interpret them as:

ASAP means the plane is going to kill you. Soon. So land before that happens. Short runways, military airports, abandoned airfields, a decent highway, dry lakes (e.g. Edwards AFB), calm bodies of water (e.g. the Hudson River) are all possibilities. Do not concern yourself with operational issues like taking off again, and bureaucratic formalities like immigration will be summarily ignored. Obviously if you are near the Hudson you would try very, very hard to reach JFK, Teterboro or Newark, but sometimes that doesn't work out.

ANSA means try for a real airport considering immediate operational and bureaucratic requirements, but not beyond immediate. this could include turning around and landing at Goose Bay. Basically I'm going to punch "Nearest" on the Nav panel and make an educated choice. Most Nav sets will only show open airfields that can accommodate your aircraft. For example, Gimli would not have appeared for Air Canada flight 143, assuming they had a suitable unit back then and the power hadn't gone out.

The terms are deliberately unclear to give the pilot some flexibility - you can't predict and write a procedure for everything.

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    $\begingroup$ Land ASAP means a controlled landing, dont confuse this with a forced landing. In other words, the pilot still has a choice of where and when, and will always choose a suitable runway over the Hudson river. Downvoted for this. $\endgroup$ – Michael Hall Oct 27 at 22:27
  • $\begingroup$ @MichaelHall: A forced landing is a controlled landing. An uncontrolled "landing" is known as a "crash". $\endgroup$ – Sean Oct 28 at 1:00
  • $\begingroup$ Good point Sean, I just meant that the airplane can fly to a suitable airfield. I.e., it isn't a glider as it is in a forced landing. $\endgroup$ – Michael Hall Oct 28 at 1:22
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LAND IMMEDIATELY Continued Flight may be more hazardous than Ditching or Forced Landing

LASAP Land as soon as possible at which a safe landing can be made or is assured

ANSA Land at nearest suitable approved airport

Land as soon as Practical Extended flight not recommended. Landing airfield and duration of flight are at the discretion of the pilot. Extended flight beyond approved landing airport is not recommended

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    $\begingroup$ I don't see how this answers the question, so much as providing more terms which may (in some unknown context) be synonymous with the terms in the OP, or which may be more gradations between extreme and slight urgency. $\endgroup$ – Ralph J Oct 27 at 16:58
  • $\begingroup$ You may add an introduction sentence to explain how it answers the question (something like "it depends on how such ans such criteria. Moreover other terms exists") $\endgroup$ – Manu H Oct 28 at 9:35

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