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As a new VFR pilot, I was wondering why anyone would fly (or be assigned) an ILS (or other) approach in clear weather?

I ask this because I watched Vienna - Tokyo (Narita) on PilotsEye.tv where the F.O. flew the approach looking at the display all the way until the flare. The visibility was good. Runway 34R.

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There are actually quite a few reasons to fly an instrument approach, especially one with vertical guidance (like an ILS), even if the weather doesn't require it:

  • It serves as a backup to the visual approach. There are various visual illusions that can cause a pilot to fly an approach too high or too low and monitoring the vertical guidance can help to mitigate those.
  • It helps to ensure that you land on the correct runway, and even at the correct airport. (Unlike this airplane.)
  • ATC uses it when pilots do not have the airport or runway in sight. This happens quite frequently at large airports where they have to line many aircraft up on final. The last guy is a long distance from the airport so may not be able to see it but can fly the approach.
  • It can be useful if it is hazy or the sun is making it hard for the pilots to find the airport.
  • Some parallel runways are approved for simultaneous approaches (as is the case at Narita for runways 34L & 34R) so ATC will clear two airplanes for the respective ILS's. This keeps them tracking the centerline of the approach instead of maneuvering visually where they might drift over into the way of the other airplane.
  • Flying the approach on the autopilot leaves more time for the pilot to focus on other things and possibly catch something that might have been missed while hand flying a visual approach.
  • Sometimes instrument approaches are used for noise abatement reasons.

If I had to guess about the particular approach that you mention, I would say that it is probably company SOP (Standard Operating Procedures) to fly the ILS whenever possible for the safety benefits, and that Narita allows simultaneous parallel landings to the two runways so ATC would require it as well.

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    $\begingroup$ I was wondering if it might have to do with how short Narita's 34R is. Your answer seems to say that could be a factor. $\endgroup$
    – greener
    Apr 23, 2014 at 17:11
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    $\begingroup$ @greener I would say that they are all factors. I also added one more paragraph which would apply at this specific airport (which I noticed after I reviewed the approach plates). $\endgroup$
    – Lnafziger
    Apr 23, 2014 at 17:46
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There are three reasons I can think of:

  1. Noise abatement
    I know that it is not allowed to fly visual approaches at many european airports due to noise abatement. They prohibit it to avoid aircraft flying over residential areas left and right of the approach path

  2. Traffic flow
    At many international airports (e.g. Tokyo) they have to use every second to manage the huge amount of traffic. Lining up the aircraft on an ILS with an assigned speed is the most efficient way.

  3. Practice / Safety
    There are many airlines which tell their pilots not to do visual approaches. This should enhance safety (stabilized approaches) and keep the pilots well prepared for low visibility operations. Sometimes you even practice autoland in VMC to keep current.

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    $\begingroup$ Noise Abatement is an interesting one -- at my home field the instrument approaches are actually discouraged for reasons of noise abatement (the nice long straight line toward the runway takes you directly over people's houses). #3 strikes me as a double-edged sword (Asiana 214 as an example). $\endgroup$
    – voretaq7
    Apr 23, 2014 at 17:35
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    $\begingroup$ @voretaq7 I too have seen instrument approaches (and more often instrument departure procedures) used for noise abatement reasons. It depends on the area surrounding each airport. #3 is very valid, but it can be taken too far. Just ask the crew of Asiana 214.... The FAA issued an InFO awhile ago about making sure that pilots practice visual approaches from time to time instead of relying on the automation. $\endgroup$
    – Lnafziger
    Apr 23, 2014 at 17:48
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    $\begingroup$ @voretaq7 I myself live below the straight-in approach of a bussy airport. Even though our national AIP prohibits visual approaches for aircraft heavier than 5.7 tonns at this particular airport. This is obviosly done to avoid the majority of residantial areas. I also see a huge difference, between european and american procedures. My poits are honestly based on the other european point of view. Airports fulfill many noise abatement regulations and the straight in approaches meet those restrictions very well. $\endgroup$
    – Falk
    Apr 23, 2014 at 20:17
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    $\begingroup$ @Falk We have instrument procedures (frequently Departure Procedures like Lnafziger mentioned) which take noise abatement into account in the US too - the procedures in the New York area generally seem to be less concerned with that though (probably because no matter where we send the plane it's still going to fly over someone's house, so there will still be complaints :) $\endgroup$
    – voretaq7
    Apr 23, 2014 at 20:56
  • $\begingroup$ How is flying the ILS more efficient than a visual approach? A visual approach has much less separation distance than an ILS approach. $\endgroup$
    – Steve Kuo
    Apr 28, 2014 at 16:05
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In addition to serving as a good cross-check for the visual procedure (which is probably the case here - one pilot looks down, one pilot looks out) there's at least one other reason I can think of for a pilot to request & fly an instrument approach:
In order to maintain currency to act as pilot in command under instrument flight rules a pilot must log a certain number of instrument approaches within a given calendar period (in the USA it's 6 approaches in the last 6 months, plus "holding patterns; and Intercepting and tracking courses through the use of navigation systems.", except for gliders which have a different requirement).

All other things being equal, if your currency is about to lapse you might request to fly an instrument approach (including one turn in a holding pattern) on a VMC day (with a view limiting hood and a safety pilot on board) to maintain currency on.

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    $\begingroup$ Umm, if it is VMC you can't log an instrument approach for currency purposes unless you use a view limiting device (which is usually prohibited by the airlines). See What are the weather requirements to log an instrument approach? for more details. Also, most airline pilots visit the simulator on a regular basis so instrument currency isn't normally an issue. $\endgroup$
    – Lnafziger
    Apr 23, 2014 at 17:44
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    $\begingroup$ @Lnafziger True - airline folks have other ways of maintaining currency. For us flibs you usually buy your (rated) friend a burger in exchange for sitting in the right seat while you're under the hood - I'll update to clarify that :-) $\endgroup$
    – voretaq7
    Apr 23, 2014 at 18:43
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$0.02 to add to all that. The question can be extended a little and one could ask 'why fly ifr on beautiful clear day'. Added safety. For a new instrument pilot it would still be a good practice to operate in the ifr system even if you can't log the flight for currency purposes.

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