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-   -   CRJ900 IRS high drift rate (https://www.pprune.org/tech-log/613655-crj900-irs-high-drift-rate.html)

dcoded 23rd September 2018 09:48
CRJ900 IRS high drift rate
 
Hi

we are experiencing problems on both IRS units on one particular aircraft individual in our fleet.
aircraft is around 2 years old and the IRS is drifting between 4-8NM per hour flying north/south I in the northern hemisphere.
last days we have started our journeys from around N54, and needed to do full alignment on the turnarounds due to IRS FMS disagree.

any takes on this?
what baffles me is that both IRS drift quite a lot.
imminent failure approaching?

vickers vanguard 23rd September 2018 16:30
Originally Posted by dcoded (Post 10256084)
Hi

we are experiencing problems on both IRS units on one particular aircraft individual in our fleet.
aircraft is around 2 years old and the IRS is drifting between 4-8NM per hour flying north/south I in the northern hemisphere.
last days we have started our journeys from around N54, and needed to do full alignment on the turnarounds due to IRS FMS disagree.

any takes on this?
what baffles me is that both IRS drift quite a lot.
imminent failure approaching?

wayyyyy too much drift for a 2 years old airplane. The RC FMS 4200 or the 6000 series will usually post an FMS-IRS disagree when you have 2.5 nm of drift in the first 30 mins of flight, and there after, if the drift is more than 2.5nm per hour of flight...those are typical numbers.

Eric Janson 24th September 2018 16:36
Originally Posted by dcoded (Post 10256084)
Hi

we are experiencing problems on both IRS units on one particular aircraft individual in our fleet.
aircraft is around 2 years old and the IRS is drifting between 4-8NM per hour flying north/south I in the northern hemisphere.
last days we have started our journeys from around N54, and needed to do full alignment on the turnarounds due to IRS FMS disagree.

any takes on this?
what baffles me is that both IRS drift quite a lot.
imminent failure approaching?
I've experienced a large drift on 1 IRS on a different Type.
An investigation found this IRS had a different part number and shouldn't have been installed in that airframe.

This should be the first thing to check.


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