E145 AHRS AH-800 LATITUDE limitations.
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Joined: Jan 2012
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From: Luxembourg
E145 AHRS AH-800 LATITUDE limitations.
Operating the E135 with AHRS AH-900, I found system limitations,
concerning LATITUDE and LONGITUDE restrictions in AFM section 2-24 and AOM 1-01-56.
The E145 has a different (older) AHRS AH-800 installed for which I could not find the same restrictions in AFM and AOM.
Question Embraer on the issue, they responded that the AHRS AH-800 uses flux valves (which is true) but I think they ignore the fact that the AHU is working with gyros (wich are slaved to the flux valve).
It may be that the limitation was omitted in the Primus 1000 guide, and therefor in the Embraer AFM and AOM.
I tried to get more info in the Honeywell Primus 1000 pliot guide, but this one does not present a limitation for the AHRS AH-800 either (it does for the AH-900). It contains a reference to a dedicated AHRS pilot guide, Honeywell publication number M28-3335-001. I phoned Honeywell to obtain this guide, but this seems to be difficult.
Could someone confirm me with certitude that there is indeed no limitation for the AHRS AH-800, or provide me with an (electronic) copy of the related guide or the limitation section of it?
Thank you all and best regards.
Mark
concerning LATITUDE and LONGITUDE restrictions in AFM section 2-24 and AOM 1-01-56.
The E145 has a different (older) AHRS AH-800 installed for which I could not find the same restrictions in AFM and AOM.
Question Embraer on the issue, they responded that the AHRS AH-800 uses flux valves (which is true) but I think they ignore the fact that the AHU is working with gyros (wich are slaved to the flux valve).
It may be that the limitation was omitted in the Primus 1000 guide, and therefor in the Embraer AFM and AOM.
I tried to get more info in the Honeywell Primus 1000 pliot guide, but this one does not present a limitation for the AHRS AH-800 either (it does for the AH-900). It contains a reference to a dedicated AHRS pilot guide, Honeywell publication number M28-3335-001. I phoned Honeywell to obtain this guide, but this seems to be difficult.
Could someone confirm me with certitude that there is indeed no limitation for the AHRS AH-800, or provide me with an (electronic) copy of the related guide or the limitation section of it?
Thank you all and best regards.
Mark
Joined: Aug 2009
Aviation Qualifications: ATPL
Posts: 616
Likes: 57
From: GPS L INVALID
As far as I have read in my 5' google research the AH-900 is a system designed to work together with an IRU package, while the previous system on the ERJ145 is a strange AHRU which requires external heading input from flux valves and magnetometers. I suspect the limitations you mention are exclusion zones both around the true as well as the magnetic poles, and this limitation makes sense for both kinds. Even the new "Super-AHRS" with IRU inputs from the four 'Laseref' IRUs has trouble there since it will not be able to perform alignment above a certain latitude since the measured earth rate will be too small to accurately determine true north. Likewise, since the airplane probably has no possibility of working with or even displaying true north there will be an exclusion zone around the magnetic poles as well. The classic attitude plus flux gate system requires a useful magnetic reference, and in these places the variation is too high to be used effectively anyway.
