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Airbus IRS initial alignment position check

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Airbus IRS initial alignment position check

Old 27th Sep 2023, 09:24
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Airbus IRS initial alignment position check

Hello all,
I'd like to know if Airbus SOPs still have the requirement to check A/C position after initial IRS alignment. Particularly, after the Airbus service bulletin SB 34-3287 Enhanced ADIRU alignment on GPS position. My company's SOPs does, it will be interesting to know what others do.

Any thoughts or reasoning welcome.

Thank you.
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Old 27th Sep 2023, 23:33
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Our SOP requires the aircraft position to be verified in ROSE-NAV or ARC mode for consistency with the position of the airport, the SID, and the surrounding NAVAIDs regardless of whether or not that particular aircraft has ADIRU alignment on GPS position.
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Old 28th Sep 2023, 00:13
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Hi ahramin, thanks for your reply.

My company also has the position verification check in ROSE-NAV / ARC mode. In addition, there is a requirement for LAT/LONG check on the POSITION MONITOR page. Which, in my opinion, is superfluous.

Thanks.
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Old 28th Sep 2023, 09:34
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I once accidentally transposed two digits of the ramp Lat and Long during my flight prep, without realising, and PM did not spot my mistake as I did so, (SOP was for us both to check the figures as PF put them in), and we took off, only to receive a Navigation position uncertain caution, (A321).

This resulted in us stopping climb and reverting to navigating direct to a VOR, old school raw data, and landing back at the original airport, for the engineers to check the aircraft.

Red faces all round and a 2 hour delay, but we still had to fly the whole duty, 4.5 hours each way.

So perhaps the new SOP is a good idea?
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Old 28th Sep 2023, 12:07
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Uplinker,
was not there a way to avoid returning to base?
In yr case there was discrepancy between IRS posn and GPS posn which resulted in corrupted FM posn but could not you correct the FM posn by overflying a navaid and then use "update at" function of the FMGC....
I am not sure if the above solution is correct.
How the Airbus plane navigates (FM, GPS, IRS...) Creates headache for me....
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Old 28th Sep 2023, 23:34
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Yes, we could have flown over a VOR to update position, and did consider that, but at the time we were not sure what the navigation problem was and we were in the London TMA at a busy time.

So rather than mess about, and potentially cause problems to others, we turned back.

Back on the stand we realised the mistake. The aircraft had been wrongly told it was 40nm or so further south, so all the DME and VORs it could see were in the "wrong" place.

I can't remember now why GPS did not override my input or at least flag it up, but not all our aircraft had GPS supplemental originally, back in the day.
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