AHRS Failure

PhilosopherPilot

PhilosopherPilot

Well-Known Member
Hi All,

I had my most interesting round trip so far the other day. I won't go into details on here, but we had an AHRS 1 failure on takeoff yesterday on the way to ATL from IND. It was the Captain's leg, so I was a little surprised to take the controls on climbout. We were never in any danger, and were in VMC.

The AHRS is the attitude heading reference system (for those that don't know), so the captain lost his attitude, airspeed, altitude, and heading indicators... Also, we lost Yaw Damper 1 and Stab Trim 1. The system would reset, then trip off again after a few seconds. Unfortunately, this meant that the autopilot would engage on my side, but even with the Captain side on my AHRS, the autopilot tripped off each time.

So that means that a brand spanking new FO like me got to hand fly back to ATL. The Captain said it was part of "paying my dues"...lol We did actually remember to not go into RVSM airspace.

Anyway, it was an interesting experience. I enjoyed it, even if it did zap my energy.

G
 
Nice! That's happened to me once, but in the ERJ the autopilot will stay on if the FD is coupled to the side with the good AHRS.

So how does she handle?
 
PhilosopherPilot said:
The AHRS is the attitude heading reference system (for those that don't know), so the captain lost his attitude, airspeed, altitude, and heading indicators...

We did actually remember to not go into RVSM airspace.
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not to nitpick, but your airspeed and altitude are coming from your ADC (airspeed, altitude, vertical speed), not AHRS (heading, pitch, bank). You can also ask to go up into rvsm while "negative rvsm". If the controller can provide you the extra spacing he needs, he can approve you up there.

nice handling of the situation :)
 
casey said:
not to nitpick, but your airspeed and altitude are coming from your ADC (airspeed, altitude, vertical speed), not AHRS (heading, pitch, bank). You can also ask to go up into rvsm while "negative rvsm". If the controller can provide you the extra spacing he needs, he can approve you up there.

nice handling of the situation :)
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Yeah, I thought of that after I posted, but it seemed to me that those indications went blank as well. It wasn't on my side though, so I can't remember. As far as RVSM goes, captain said tell the controller unable RVSM, so I did. :)

As far as the AP is concerned, I thought it would stay on if coupled to my side too, but for some reason it wouldn't. I think it was because every time the AHRS blipped, the yaw damper would trip off, which killed the AP. Any ideas??? We even left the YD1 off to see if it would still trip the AP off, and it did...

G
 
Not sure of why, but on the CRJ the YD1 is linked to the ADC on the left side. I guess the AHRS dieing was too much for the ADC1 to handle and it was tripping the YD1 (which kicks the AP off). Got to love the system overlap on the CRJ.
 
I feel for you... Fresh out of IOE I get a plane with the Autopilot MEL'd and we did a EWR-DCA turn! It was like a friggin' PC with an instructor form he!!. :)

"Jetlink 1234, Turn 20 right for vectors into DCA and decend and maintain fl230, slow to 270 knots."
"Jetlink 1234, heading 180, descend fl170, slow to 250 knots, altimeter 29.96, traffic 10 o'clock 1000' ft below, heading 090, an MD80."
"Jetlink 1234, turn 30 degrees left for vectors ILS RWY XX, slow to 210, upon slowing to 210 decend and maintain 8000, traffic a CRJ 11 o'clock and 8 miles, advise traffic in sight."
ETC...

LOL! It seemed every call was like that... Never once just a simple "decend and maintain" or "slow to" call. Fun stuff... ;)

Bob
 
I've seen the avionics/AP do some weird stuff on the CRJ. It's like the Windows 2000 of systems. Good job on the return!

My sim partner during 700 differences was a captain and he lost his PFD below 80 knots. I didn't see it (now I know to look at both PFD's when I'm PNF) he kept going and gave me the controls at V1. Now I'm not so lax when I'm the PNF.
 
PhilosopherPilot said:
As far as the AP is concerned, I thought it would stay on if coupled to my side too, but for some reason it wouldn't.
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On the Primus 2000 system in our aircraft, autopilot operations are prohibited with an inop AHRS/IRS. It is an aircraft limitation.

EDUC8-or said:
My sim partner ...captain ...lost his PFD below 80 knots. ...he kept going and gave me the controls at V1.
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I hope that display of how not to do something was in the sim! I further hope the sim instructor had some...creative...suggestions for future failures.
 
BobDDuck said:
Not sure of why, but on the CRJ the YD1 is linked to the ADC on the left side. I guess the AHRS dieing was too much for the ADC1 to handle and it was tripping the YD1 (which kicks the AP off). Got to love the system overlap on the CRJ.
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That might explain why the airspeed and alt info was going away as well. It is possible that the problem was more than the AHRS though. We didn't talk to Mx afterwards to follow up with the problem. I would like to know what was going on, just for future reference.

G
 
Captain_Bob said:
I feel for you... Fresh out of IOE I get a plane with the Autopilot MEL'd and we did a EWR-DCA turn! It was like a friggin' PC with an instructor form he!!. :)

"Jetlink 1234, Turn 20 right for vectors into DCA and decend and maintain fl230, slow to 270 knots."
"Jetlink 1234, heading 180, descend fl170, slow to 250 knots, altimeter 29.96, traffic 10 o'clock 1000' ft below, heading 090, an MD80."
"Jetlink 1234, turn 30 degrees left for vectors ILS RWY XX, slow to 210, upon slowing to 210 decend and maintain 8000, traffic a CRJ 11 o'clock and 8 miles, advise traffic in sight."
ETC...

LOL! It seemed every call was like that... Never once just a simple "decend and maintain" or "slow to" call. Fun stuff... ;)

Bob
Click to expand...

Same thing here. We were coming into ATL, right about the time that 27L lost lighting, and all a/c were landing on 26R. We got more vectors and speed changes than I've ever had coming to ATL...

G
 
NJA_Capt said:
I hope that display of how not to do something was in the sim! I further hope the sim instructor had some...creative...suggestions for future failures.
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The captain was buying that night. He got chewed OUT!
 
Threads like this remind me why I hand fly so much. On short legs I'll sometimes hand fly the entire leg, except to reach behind and pull out my charts for the arrival airport. I've had so many guys ask, "You're not on autopilot yet? Geez, you're motivated!" Just have to watch the autopilot fail once after months of its use to see the need to keep your scan and handflying skills sharp!

I'm with NJA_Capt, surprised with the failure of the CA's PFT in your post EDUC-8r that he (the CA) didn't call for an abort.
 
My dad does mostly Europe flying, so the A/P goes on for the crossings. However on the SNN-DUB legs most guys hand fly it for the 30 minute flight or so.

A crew at his airline had an autopilot not engage coming out of FCO, and they hand flew it the entire way back to the States. Now that is a long way without an A/P. At least it was a 3 crew flight with a relief pilot so they could take a break.
 
"A crew at his airline had an autopilot not engage coming out of FCO, and they hand flew it the entire way back to the States."

Man....I think I'd start asking for volunteers from the back of the plane to come up and help me out.
 
Good grief. SAN-SLC without an autopilot whipped my butt. I'm surprised they dispatched with an inop autopilot.
 
P.Pilot, good job on handling the situation, I'm sure it was good experience. That is a long flight for hand flying.

I'm still not sure what's worse....MEL'd Autopilot or MEL'd FMS. With all the functionaitlity we get out of the FMS, (Weight and Balance, Performance Initialization, ACARS in range calls, not to mention RNAV), I'd rather give up the autopilot if the flight is shorter than 2 hours enroute. We did CLE-IAD a few months ago with no FMS. It was interesting, especially since ATC gave us some weird airway re-routes, but manageable.

I've handflown the EMB up to FL370 a few times for kicks....nothing too demanding about it, just takes concentration like any other phase of flight, although it gets a little pitch-sensitive in the 30's. I'm almost surprised you guys were able to stay out of RVSM on IND-ATL without taking a fuel hit, but I guess it's only 400 NM or so.

Of course we have some guys around here that do this kind of masochistic stuff for fun, they call themselves Beech Drivers. You know you're flying with an Ex Beech driver when he's always backing you up in cruise with Green Needles on your legs, and on his legs disengages the autopilot and turns the flight guidance off below 10.
 
PhilosopherPilot said:
Hi All,

I had my most interesting round trip so far the other day. I won't go into details on here, but we had an AHRS 1 failure on takeoff yesterday on the way to ATL from IND.
Click to expand...

Good job on handling the situation.

I had similar situation in the Saab but we had to abort the takeoff. Both AHRS rolled inverted due a severe vibration caused by a nosewheel throwing a weight off prior to V1.
 
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