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In another SE Aviation question about the preferred approach for commercial aviation (Visual vs ILS) there's the following useful explanation:

In most ATC facilities, the Tower decides what runway to use, and the approach control calls the type of approach generally on offer(this can vary depending on facilities and how they agree to run things). A pilot can always request a different approach... they might be delayed, sometimes significantly if they insist on something way out of the loop

I'm curious what would be examples of a pilot insisting on "something way out of the loop"?

What's the preferred approach for a passenger jet?

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  • $\begingroup$ Interest only: Here is an only slightly out of the loop real world event - Jean Batten International aka Auckland Airport in NZ has an over-land or over water approach with the former usually being used due to prevailing wind. When the US President visited NZ "some while ago" they used the "over water" approach for Airforce 1 - presumably to minimise the opportunities for the bad guys to do something undesirable. I don't know which direction was used on departure. $\endgroup$ – Russell McMahon Jan 11 '16 at 12:31
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    $\begingroup$ Great Barrier Airlines serves Islands in the Hauraki Gulf. Some years ago their fleet included 4 x 3-engined STOL capable Britten-Norman Trislanders. I noted on a number of occasions at Jean Batter airport that these used to take off towards their destination (towards landward) regardless of what everyone else was doing on a given day, and would alter course soon after takeoff when all "normal" airliners were still climbing out. Britten-Norman Trislander $\endgroup$ – Russell McMahon Jan 11 '16 at 12:42
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For currency, airline pilots have to do various approaches every so often to remain current or for the plane to be current (RNAV/ILS Cat II/III approaches). So, every now and then when coming to another airport they could request to shoot that approach instead of the one being used. Sometimes it's a non event (no traffic, or the few other aircraft either fit well before or behind them); other times, it could hinder the flow of operations if they're allowed to do full or certain procedures (various circling to land procedures).

Another very common request that falls in this category is to land or depart in the opposite direction of what's being advertised. This in recent years has become more cumbersome for controllers (due to more and new rules implemented), so it's being used less often.

Sometimes when there's little traffic it's fairly easy to accomplish this kind of arrival or departure. Other times, it becomes a nightmare, and unless it's operationally mandated the pilot will be told, unable opposite direction, due to traffic. When it's operationally needed, then it will be told to hold somewhere to wait until there's space to get them out for departure; or vectored around or put in holding if needing to land opposite direction, and they can be accommodated.

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  • $\begingroup$ another example is when the pilot requests to fly the full approach, rather than vectors-to-final $\endgroup$ – rbp Jan 10 '16 at 20:52
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    $\begingroup$ Here is what happens when the crew does not ask for Cat II/III and tries to do it anyway. $\endgroup$ – Jan Hudec Jan 11 '16 at 6:49
  • $\begingroup$ @JanHudec I tried reading that accident report a couple of times & there's even a very nice Youtube Video of the incident but I'm still not getting what exactly went wrong there. Could someone elaborate? $\endgroup$ – curious_cat Jan 11 '16 at 17:26
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    $\begingroup$ @curious_cat Basically, when Cat II/III procedures are in effect the runway and critical areas are more protected, to prevent signal disruption from aircraft or vehicles blocking the signal when doing an auto-land approach. When you want to do an autoland for currency, you often won't get those areas protect, so you have to be more vigilant or willing to turn off the auto-pilot or go around if you notice the signal is getting weird. $\endgroup$ – slookabill Jan 12 '16 at 2:34
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    $\begingroup$ @curious_cat, specifically in this case it was apparently the departing plane that was in the air, but still over the runway (because visual environment allows less separation) that disrupted the localizer signal and confused the autopilot during roll-out. $\endgroup$ – Jan Hudec Jan 12 '16 at 8:26
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At times ATC wants arrivals to land even though the runway-in-use has a tailwind component. This may occur e.g. during a weather front passage. However, some aircraft types may not be certified for more than a minor tailwind. Also company procedures or pilot's personal minimums may apply. If the runway is wet, snow-covered or of the shorter variety even less tailwind is acceptable. I once listened to an ATC conversation where ATC wanted an airliner to land in a 10-15 knots tailwind. The pilot in command refused, referring to company policy.

For smaller aircraft, strong crosswind may be the triggering factor which prompts the pilot to request a different runway. Especially if he flies a taildragger aircraft.

Modern airliners typically can handle quite strong crosswinds, but not if the runway is wet or otherwise slippery. In those cases a request for a different runway may also be the right choice.

Requesting a different kind of approach may occur because the pilot wants to maintain his proficiency to fly that particular type of approach. Sometimes the reason is to save time, such as when requesting a close-in visual approach instead of adhering to the default ILS approach.

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