FMC ETA times changing dramatically

[Guest Gordius]

I have noticed that when flying East from, say Kabul to Anchorage that ETA time at destination keeps changing to a time many hours later than the ETA given on the ground. Example ETA at start and actual time of arrival about 0800Z but ETA on FMS varies between that and at times as last as 1700Z.Seems to happen soon after Japan passes by. ETA on ground is fine when I start out. I will fly a leg soon to some details and a flightplan you can see but I thought I would mention it now in the hope of someome else having same thing.Andrew BrownAssociation of Crazy Pilots and Controllershttp://www.crazypilots.pwp.blueyonder.co.uk/

[Guest RobertK]

I had exactly the same problem when flying west over the Atlantic into the Caribbean.It seems however, the solution can be found here:http://forums.avsim.net/dcboard.php?az=sho...ing_type=searchI'll test that myself on the return leg.Regards,Robert

[Guest NormanB]

I have only seen this happen when you change the step size from ICAO to something else.It is to be addressed in the patch.

[Guest Gordius]

>I have only seen this happen when you change the step size>from ICAO to something else.>>It is to be addressed in the patch.On both occasions step size was ICAO. As I said I will get specific data for you so tonight I will go for a Japan to Anchorage flight as a test. The following flight I will try same flight this time with no steps (leave FMC at ICAO and stay at one altitude). You can have as have as much data as you like so I will get a pile of stuff and supply you with a download link to pick up a zip file (I imagine email must be full of attachments for you).Not having a moan but I guess that if something needs patching you need as much info as you can get.Andrew Brownhttp://www.crazypilots.pwp.blueyonder.co.uk/

[Guest Gordius]

A thought. Exactly what data are you interested in?Andrew Brown

[Guest RobertK]

>I have only seen this happen when you change the step size>from ICAO to something else.Here it is the other way around actually.Over the course of the last days, I did two long-hauls with the 777-200LR.One from Gatwick to Antigua, and the return leg.On the first flight, I never changed anything about the step size (thus it remained set to "ICAO"), and had the problem with the ETAs up to the last step climb.On the second flight, I set the step size to "0", and had no trouble at all, the ETA remained with very little variation during the whole flight.(Note: I did actual steps on both flights)Regards,Robert

[SierraDelta 1,337]

Based on earlier posts shortly after release of the 777, I have been using a step size of 0, which has almost eliminated the "crazy ETAs" problem. Sure, you've got to keep an eye on things to do the steps at the optimum time yourself, but that's not exactly rocket science. However, yesterday I flew EGLL-KORD and when I did my final step from FL380 to FL400 somewhere over Canada the ETAs were all over the place and never recovered. It has to be said that: 1) I stepped too early, OPT FL was 388, and2) I was only about 750 miles from KORDNevertheless, if this helps spot the solution....Cheers,S

[Guest Gordius]

Hi S

[SierraDelta 1,337]

I was flying offline, with ActiveSky Enhanced wx. I'm right now on the next leg, KORD-KIAH and I have reproduced it again. Climbed initially to FL380 (with STEP SIZE 0), the ETAs were looking fine. When OPT FL was 389 I climbed to FL400 and the ETAs started drifting.At the moment OPT FL is FL391, I've tried switching the STEP SIZE between 0 and 2000 (which would be the correct value), but no improvement.All this aside, if I remember well, this problem as well as the proper solution (Norman?) has already been identified, so don't waste your time on too much research... ;-)Cheers,S

[Guest Gordius]

Hi again S