View Full Version : B777 Drift on gnd?
SuperRanger
19th Feb 2004, 17:08
Have any of you ever notice there is a slight drift (1-2deg) when on the ground in about 50% of the time? Couldn't for the life of me figure this one out! Could variation have any thing to do with it?
SR
Virginia Plane
19th Feb 2004, 17:46
IRS position wandering?
SuperRanger
23rd Feb 2004, 20:14
i apologise for not being specific enough. what i mean by drift is there is 1-2deg difference between the TRK and HDG? as far as i understand it, this should happen when there is a drift i.e crosswind. but this is when the acft is on the ground?!
ideas?
SR
alexban
26th Feb 2004, 23:38
just an ideea:
I saw the 737's from behind when taxiing.They are not alligned with the taxi line,they seem to deviate a little to the right,I think(due to gear design). If this is the case,the HDG will differ from the TRK with 1-2 degrees.Maybe it's the same with 777
alex:ok:
fruitloop
27th Feb 2004, 02:02
Sounds like the main gear shimmy dampers need bleeding !!
SuperRanger
27th Feb 2004, 13:45
solved!
the reason is due to different Magnetic Variation Tables being loaded into the FMC and ADIRU. The FMC has 1995 MagVar Tables while the ADIRU has 2005 MagVar Tables. TRK comes from FMC while HDG comes from ADIRU.
SR
alexban
29th Feb 2004, 05:17
Gee, how do you know all that? Just kidding. But you said this apeeared only 50% of the time? How did you solve that ?:confused:
SuperRanger
29th Feb 2004, 20:37
it was explained in one of boeing's bulletin! :O