ETA Crossing time limits

[blueloo]

Anyone know where (if any) there is a reference to fix crossing times...

ie Cross Boree at 0518 -- the rule of thumb most people use seems to be +/-1 minute

but I cant find a reference to this. The only reference appears to be regarding clock time reference +/- 30s.

[capt_akun]

ENR1.1 - 21.1.5

When a pilot becomes aware that a previously notified position estimated is more than two minutes in error, the pilot must report and, where necessary, broadcast a corrected estimate.

[Tempo]

There is also a reference in the AIP (don't have it with me) stating when given a crossing time you can cross up to 1 min early but not later.

[blueloo]

Yeah - I had the impression that this is a bit vague - maybe Tempos thoughts are closest to the mark.... had heard that too, but can't find the reference.

I think the 2 mins revised estimate is a bit different, as that is just when you are waffling along at your own pace, and havent been given a specific requirement to be at a point at a time.

[Icarus53]

Sorry I can't provide a proper answer to the question at hand, but you might be interested in some of the comments in this thread dealing with FMC timings etc. One or two good comments from our ATC brethren.

http://http://www.pprune.org/forums/showthread.php?t=319266&highlight=FMS+GPS+Inaccurate

[max1]

Blueloo,
As an ATC I expect where your confusion is that, when given the Boree time that the controller has told you that they get a 1 minute either side of the time as play room. On MAESTRO (our flow computer into SY/ML/BN) we are given a time that SY expect you to put the aircraft over a feeder fix point Boree, Marln etc.
We are given 1 minute either side of this time as 'wriggle' room to allow for aircraft slow/quick turner, controller late or early turning etc etc. I have had aircraft report that they will be a minute late or early at the feeder fix and have told them No problem we have a minute to play with either side of the crossing time I specified.
Having said that it makes our life and Approach's life easier if we get it right.
Hope this helps.

[Jimothy]

I've heard the 1 minute early quoted to me on numerous occasions. However no one has been able to provide a reference except, they think it is in AIP somewhere. I have looked and never found it, anyone able to provide a reference? I don't believe the leaving the Holding Pattern one minute early reference covers it.

[Driscoll]

In a tight sequence I think early is better than late, track miles can nearly always be added. If late it pushes everyone behind you back. On time and we're all happy. Best thing to do is if you can't make it either way tell the controller as early as possible.