Holding Timing

[Shaka Zulu]

Having some brain troubles here guys, in me old cessna i seem to remember doing 1 min holds.

Are we doing 1min15 holds in commercial airliners beneath 14000'?

If so why the difference, is it speed related?

[G-ANDY]

SZ,

I'm pleased that I might be able to help here - my Air Law ATPL theory exam is just two weeks away and that is a question:

1 minute for FL140 and below.
1 minute 30 when above FL140

I do 1 minute holds in my Warrior too, but not sure for the reasoning for longer holds at altitude.

Apparently the ATPL Air Law theory exam was written by an air traffic controller and is full of these questions, if s/he's reading maybe they can shine some light on the reasoning!!!

Andy

[AerocatS2A]

If you are asking the question because you were in an aircraft that seemed to be doing a 1:15 holding pattern, there may be a few reaons.

a. The inbound turn in the holding pattern was a DME limit rather than a time limit.

b. There was a strong headwind on the outbound leg and the crew were adding 15secs to allow for it.

c. It was a two minute pattern (somtimes you get these for specific holds below FL140) and the crew had been given a shortened outbound leg by ATC to facilitate sequencing for the approach.

d. The crew forgot to commence timing abeam the aid.

e. The aircraft had attained the outbound heading 15secs prior to passing abeam the aid (when timing is commenced) so the leg seemed longer.

[BOAC]

I would venture to suggest that in this 21st century very few 'commercial airliners' fly procedural holds with LNAV available? The timing, therefore, would depend on when the computer decides to turn, since it flies a ground track (on the 737).

[Shaka Zulu]

I appreciate that fact about LNAV, my 73NG does the same thing. But I'm getting confused when there is no DME distance specified to start the turn.
Would it be different in terms of timings between CAT A/B/C/D aircraft below 14000'?

[BOAC]

The latest I can find is this which includes some info I did not know!!

"The holding timing procedures may vary from country to country. Generally, under no wind condition, the inbound and the outbound legs are flown for one minute ( a minute and one half when above 14,000 feet). "Although both legs are timed, only one of the legs is used to determine the protected airspace. In the US the one minute inbound leg determines the airspace while most of the other countries use the recommendation of the International Civil Aviation Organization (ICAO). Under this recommendation the outbound leg is used to determine the protected airspace. "

I'm not sure what your question refers to - did you time ONE leg of a hold somewhere at 1:15, were both legs 1:15 or what? If the hold was LNAV as you know the 'timing' will depend on what is in the FMC, ie leg time or distance. Crew can request extended legs for fuel economy or weather. ATC can 'impose' non-standard.

[MrBernoulli]

BOAC

I think that you will find that your 737 will fly a 1 minute hold in LNAV if that is what that particular hold, from the FMS database, is coded to do. On most holds below 14000 ft, if you look at your HOLD page in the FMS, you will see the standard hold is 1 minute. On the 777, and others I guess, there is the option to change that time or substitiute a ground distance e.g. 20 nm.

The computer only flies what it is programmed to fly, not "when the computer decides to turn". I doubt very much that it flies a strict ground track. Whilst you can change the leg to a distance, as mentioned above, the radius of the turns probably depends on your TAS with a bit of Angle-of-Bank-limit influence?

[Shaka Zulu]

Maybe my confusion stems from the fact that for CAT C procedural turns the "standard" leg time (i have seen this vary) is normally 1:15.
So I came to some oddball conclusion that for CAT C aircraft an unprescribed hold, a timing of 1:15 would be required.

Now I only remember real hold timings from my old IR times and it was to time abeam the beacon for 1:00.

LNAV does use a groundtrack, it simply follows whatever you say the line is, it doesnt actively track a radial like Bernoulli suggesting.