Shenanigan Posted April 6, 2013 Report Share Posted April 6, 2013 I'm a UH-60 pilot. I'm wondering has anyone noticed the AHRS system failing or being off on both sides more often than it should be? On several occasions now I've had both VSI's reading incorrectly in the same way. The left and right side are supposed to be completely independent and when one is off the other should not fail at the same time in the same way. I do not get a failure, they just read incorrectly. I know that for an IFR certified aircraft these must operate independently and the likelihood of this event should be extremely rare but I'm beginning to think there may be something inherently wrong with the AHRS system in a 60. On one occasion I had both attitude indicators reading 30 degrees off in roll 50 degrees in pitch, the turn and slip indicators off and the HSI about 100 degrees off on both sides with no failure. On another occasion both attitude indicators were about 5 degrees off in roll. Anybody seen something similar? Quote Link to comment Share on other sites More sharing options...
Velocity173 Posted April 6, 2013 Report Share Posted April 6, 2013 Nope, never on both sides. On rare ocassions I've had one side be off a few degrees but we just slaved off the good one. One time I had the annunciator say "Fogs Fail" and I believe the copilots VSI went haywire. Generally had way better reliability with AHARS over the old gyros. They didn't do well in the freezing mornings in Germany. Quote Link to comment Share on other sites More sharing options...
d10 Posted April 6, 2013 Report Share Posted April 6, 2013 I've had a situation where a FOGS failure turned both compass cards about 30 degrees off. It was feeding bad ground track data to our 128D as well. All of our instruments except the standby compass said we were flying 360 back to Bagram. The only thing we could see outside was the lights of Kabul. Eventually we realized it was strange to see them out the right front when they should be straight ahead and figured out the problem before we plowed into the 14-15k peaks we were heading towards. 1 Quote Link to comment Share on other sites More sharing options...
Velocity173 Posted April 6, 2013 Report Share Posted April 6, 2013 Yeah it's strange how that stuff affects the 128. Had a situation once in the right seat where my VSI went bad. I went to ALT on the VERT GYRO and my ground speed on the 128 was changing by like 50 kts! I would press it and release and ground speed was going up and down. Never seen seen anything like it. MTP said something like "well all that stuff is connected so it affects one another." Really? A vertical gyro affecting ground speed on a GPS. Hilarious. I had a 360 track heading back to Lowe once as well. I can't remember what AHARS indications I had but it was showing 360 on the GPS track but I was coming in SW cooridor heading east.I wanna say my heading indicator was accurate though. It was 5 yrs ago so I can't remember all the indications. Only time I ever had a bad track on the GPS though. Quote Link to comment Share on other sites More sharing options...
CharyouTree Posted April 6, 2013 Report Share Posted April 6, 2013 I think there's an ASAM, or AMAM, or something about this? I know at Rucker there was a phase before I left of writing up ANY issues with the AHRS and reporting to ACLC. If I recall, part of the problem was bad grounding, and they received authorization to install another ground. It's completely possible that I'm mixing things up, though... Quote Link to comment Share on other sites More sharing options...
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