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[jetjackel]

Hi Gentlemen,

Have a friend "stuck sitting" on a C Check for a MD-83 in a country with inadequate maintenance.

Aircaft is full EFIS but the Mode Selector does not have PLAN MODE.  FMS/GPS is a Marconi 900.

On a Ground Check the RMI's match / Mode's ARC & ROSE also match the RMI's.

When NAV, LOADED WITH A ROUTE, is selected, the HEADING STAYS AT NORTH, even when taxing on different headings.  All EFIS (VERT GYRO etc) is perfect.  The NAV MODE SETTING RETAINS A HEADING OF NORTH.

THE MARCONI DATA BASE IS OUT OF DATE BY 24 MONTHS. Could this cause the problem due to the Marconi not accepting an out of date data base?  Or is the problem with the AHRS?
Appreciate any imput.

[flyhappy]

  Jackal, if the Data base is out of date, it shouldn't affect the NAV mode.
No reason for the NAV data to be out of date either.

[Jor]

It happened to me once, but the MAP mode showed the track diamond pointing north with the aircraft still, the heading white triangle was pointing the correct heading but I couldn´t see it because it was out of view. When the aircraft started to move, the track and heading synchronized in the correct way.
For example, the airplane was heading 270°, the MAP mode pointed track 360°, so the heading triangle was out of the rose scale.
good luck!

[flyhappy]

  Jackal, If the Headings are ok in the ARC and the ROSE mode it is not a problem of the AHRS. They must check out the NAV mode. It might be the data base out of date or the unit it self.

[jetjackel]

That's what I was thinking. 

thanks for the info. 

I'll pass it on.

[flyhappy]

  Jackal did they sort out the problem?