View Full Version : IRS – magnetic variation tables
Danil
13th Mar 2007, 15:35
For P-RNAV certification there is a requirement to have the” Magnetic Variation Tables “updated. Does anyone know what all is about?
FE Hoppy
13th Mar 2007, 17:22
Heading is derived from the IRS on modern AC. No magnetic compass system.
IRS aligns to true north then adds local variation to display mag heading. The local variation is stored in the IRS memory somewhere and as it changes with time the variation table or map must also be updated.
reynoldsno1
13th Mar 2007, 19:40
ISTR the WMM (World Magnetic Model) is used - latest update was 2005 and it is valid for 5 years (I Think)
ICT_SLB
14th Mar 2007, 04:29
Mr. Reynolds is correct. We've just got a new software update to verify in a Northrop-Grumman (Litton) LTN-101 with 2005 Mag model. This is on the CRJ but it's the same unit & SW for majority of Airbus' AFAIK.
Inertial input is required for "coasting" (when no valid GPS solution available) for AC90-101 SAAAR ops.