View Full Version : Q regarding mag. var. calc in a Universal 1K FMS

Flap Sup
20th Mar 2011, 23:43
Haven' t spoken to the engineer yet, so a quick question for you experts:

How does a Universal UNS 1K FMS know the mag variation? Is it taken from a nav database or calculated from gps with input from the flux gate?

The reason I'm asking is, that the FMS now tells us that the local variation is 9deg higher than shown in the charts, resulting in wrong MT and WV.

It is possible to manually input the mag variation in the data pages, but I would prefer to have the problem solved.

Any inputs?

21st Mar 2011, 00:54
It is taken from the database. There should be two databases loaded so you could activate the other and see if the variation changes.

Is it a constant 9 difference?

Flap Sup
21st Mar 2011, 01:29
The variation varies from 7 deg to 11 deg more than it ought to be.

Ill try to load the other databas to see if it helps, although I think its for another region.


21st Mar 2011, 07:24
A 1 K FMS database? Are you sure about that?

On the A320 I think the smallest database memory available is 190K and that doesn;t come close to covering all of N/Amer.

I believe the the A320 mag var tables are in the IRS, not the FMS.

21st Mar 2011, 13:09
The UNS-1K FMS does not require an IRS to function. All it needs is a heading input. The navigation computer database has a 32 megabyte capacity.