Narrative:

While cruising at FL270 in the vicinity of szw VOR; the following aircraft system cas messages appeared all at the same time: yaw damper fail; autoplt fail; and stick pusher fail cas. The yaw damper inoperative required a descent to below FL200 and we promptly requested FL190. We were cleared to FL240 and to expect FL190 but we descended below that because FL190 had been selected by the PF in the altitude select. Center caught it when we were descending out of FL230 and they had us level at FL220. My function on this flight was to mentor a newly rated pilot. The cause of this deviation was the distraction of trying to complete 3 non normal procedures while descending and communicating with ATC and I did not catch the fact that 190 had been set in the altitude select. If I had to do this one over I would have advised ATC the reason for the lower altitude request and that might have triggered additional awareness on all of our parts. Supplemental information from acn 777654: while cruising at FL270 in the vicinity of szw VOR the following aircraft system cas messages appeared at the same time: yaw damper fail; autoplt fail; and stick pusher fail. The yaw damper inoperative required a descent to below FL200 and we immediately requested FL190. I was hand-flying the plane and only heard the cleared to FL190 and missed the FL240 and expect FL190 and selected FL190 in the altitude selection function. Center caught our descent below FL240 when we passed FL230 and asked us to level at FL220. On this flight I was receiving instruction from my mentor pilot. I believe contributing factors were distrs from completing non normal procedures while communicating with ATC and headset noise level during ATC's transmission. In the future I will advise ATC of the problem requiring the need for the altitude change to enhance awareness of the situation.

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Original NASA ASRS Text

Title: EA50 FLT CREW HAS ALT EXCURSION FOLLOWING YAW DAMPER FAILURE WHICH REQUIRES A DESCENT BELOW FL200.

Narrative: WHILE CRUISING AT FL270 IN THE VICINITY OF SZW VOR; THE FOLLOWING ACFT SYS CAS MESSAGES APPEARED ALL AT THE SAME TIME: YAW DAMPER FAIL; AUTOPLT FAIL; AND STICK PUSHER FAIL CAS. THE YAW DAMPER INOP REQUIRED A DSCNT TO BELOW FL200 AND WE PROMPTLY REQUESTED FL190. WE WERE CLRED TO FL240 AND TO EXPECT FL190 BUT WE DSNDED BELOW THAT BECAUSE FL190 HAD BEEN SELECTED BY THE PF IN THE ALT SELECT. CTR CAUGHT IT WHEN WE WERE DSNDING OUT OF FL230 AND THEY HAD US LEVEL AT FL220. MY FUNCTION ON THIS FLT WAS TO MENTOR A NEWLY RATED PLT. THE CAUSE OF THIS DEV WAS THE DISTR OF TRYING TO COMPLETE 3 NON NORMAL PROCS WHILE DSNDING AND COMMUNICATING WITH ATC AND I DID NOT CATCH THE FACT THAT 190 HAD BEEN SET IN THE ALT SELECT. IF I HAD TO DO THIS ONE OVER I WOULD HAVE ADVISED ATC THE REASON FOR THE LOWER ALT REQUEST AND THAT MIGHT HAVE TRIGGERED ADDITIONAL AWARENESS ON ALL OF OUR PARTS. SUPPLEMENTAL INFO FROM ACN 777654: WHILE CRUISING AT FL270 IN THE VICINITY OF SZW VOR THE FOLLOWING ACFT SYS CAS MESSAGES APPEARED AT THE SAME TIME: YAW DAMPER FAIL; AUTOPLT FAIL; AND STICK PUSHER FAIL. THE YAW DAMPER INOP REQUIRED A DSCNT TO BELOW FL200 AND WE IMMEDIATELY REQUESTED FL190. I WAS HAND-FLYING THE PLANE AND ONLY HEARD THE CLRED TO FL190 AND MISSED THE FL240 AND EXPECT FL190 AND SELECTED FL190 IN THE ALT SELECTION FUNCTION. CTR CAUGHT OUR DSCNT BELOW FL240 WHEN WE PASSED FL230 AND ASKED US TO LEVEL AT FL220. ON THIS FLT I WAS RECEIVING INSTRUCTION FROM MY MENTOR PLT. I BELIEVE CONTRIBUTING FACTORS WERE DISTRS FROM COMPLETING NON NORMAL PROCS WHILE COMMUNICATING WITH ATC AND HEADSET NOISE LEVEL DURING ATC'S XMISSION. IN THE FUTURE I WILL ADVISE ATC OF THE PROB REQUIRING THE NEED FOR THE ALT CHANGE TO ENHANCE AWARENESS OF THE SITUATION.

Data retrieved from NASA's ASRS site as of May 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.