Narrative:

IFR flight conducted in clear weather. ATC provided vectors for climb to FL200 and then via direct. Cleared to descend at pilot's discretion to 16;000. During descent the autopilot warning horn sounded in the cockpit followed by loss of all autopilot functions and warning flags in the EFIS instruments; including attitude and heading indicators; and RMI. It took a few moments to ascertain that the back-up attitude indicator and co-pilot instruments were providing correct attitude and heading information and there was no loss of altitude instrumentation. During this period; I was hand flying with a partial panel; and lost focus on my continuing descent. I am not certain if I reset the altimeter from 29.92 to local setting of 28.77 provided by ATC with the clearance. First awareness of the issue was a traffic alert. Looking out of the cockpit; I immediately noticed oncoming aircraft slightly lower passing on the left at 11:00 going to 10:00 and called ATC. Just after making the call; I noticed my altitude was indicating 15;600 and I climbed back to my clearance of 16;000. Evasive action was not needed to avoid collision. ATC called to confirm that I was level at 16;000 and I reset my altimeter a couple of times to see the difference between indicated altitude at the two settings and concurred. During the remainder of the flight (in VMC); a few brief lateral deviations from course occurred as I was hand flying while attempting to reset the gyro instruments and isolate the problem. The loss of all gyro instruments and autopilot; even in excellent VMC; is a highly distracting event. While I am quite comfortable hand flying and have practiced partial-panel flying on many occasions; this was a novel failure configuration for me. Because it was VMC at a comfortable hight above ground; I focused a lot of attention on trying to isolate the problem to particular system; at the expense of attention to my descent clearance. For example; during this time I was examining each of the many error messages flagged in the EFIS system; the moving map; and comparing the pilot and co-pilot instruments. In addition; I cycled off the four gyro switches together and sequentially. (At no time were the radios off.) a contributor was loss of the altitude alert in my altitude pre-select; use of which is an important part of my IFR routine. As soon as I receive a new clearance; I dial in the cleared altitude and it was set to 16;000 in this case. Even when the autopilot is disengaged; this system normally provides an alert tone 1000 feet prior to the indicated altitude and an alert tone when 200' past the indicated altitude. Neither of these alerts sounded in this failure condition. Factors that could have prevented the altitude deviation and subsequent loss of separation:1. My attention to flying the airplane as a priority over diagnosis of the problem.2. Stopping the descent and letting ATC know that I was experiencing significant avionics issues as soon as they occurred. (I considered declaring an emergency; but did not as I had sufficient navigation information to complete the flight safely).3. Traffic call from ATC to inform me that opposite direction traffic would be passing just 1000 ft below my cleared altitude (not to deflect responsibility; but these calls are common and often helpful: I always read back my cleared altitude when I get these calls).

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Original NASA ASRS Text

Title: During descent in VMC to 16000 feet a TBM7 pilot experiences loss of all autopilot functions and warning flags in the EFIS instruments; including attitude and heading indicators; and RMI. During trouble shooting descent continues below 16000 feet and a TCAS TA alerts the reporter to his continued descent.

Narrative: IFR flight conducted in clear weather. ATC provided vectors for climb to FL200 and then via direct. Cleared to descend at Pilot's Discretion to 16;000. During descent the autopilot warning horn sounded in the cockpit followed by loss of all autopilot functions and warning flags in the EFIS instruments; including attitude and heading indicators; and RMI. It took a few moments to ascertain that the back-up attitude indicator and co-pilot instruments were providing correct attitude and heading information and there was no loss of altitude instrumentation. During this period; I was hand flying with a partial panel; and lost focus on my continuing descent. I am not certain if I reset the altimeter from 29.92 to local setting of 28.77 provided by ATC with the clearance. First awareness of the issue was a traffic alert. Looking out of the cockpit; I immediately noticed oncoming aircraft slightly lower passing on the left at 11:00 going to 10:00 and called ATC. Just after making the call; I noticed my altitude was indicating 15;600 and I climbed back to my clearance of 16;000. Evasive action was not needed to avoid collision. ATC called to confirm that I was level at 16;000 and I reset my altimeter a couple of times to see the difference between indicated altitude at the two settings and concurred. During the remainder of the flight (in VMC); a few brief lateral deviations from course occurred as I was hand flying while attempting to reset the gyro instruments and isolate the problem. The loss of all gyro instruments and autopilot; even in excellent VMC; is a highly distracting event. While I am quite comfortable hand flying and have practiced partial-panel flying on many occasions; this was a novel failure configuration for me. Because it was VMC at a comfortable hight above ground; I focused a lot of attention on trying to isolate the problem to particular system; at the expense of attention to my descent clearance. For example; during this time I was examining each of the many error messages flagged in the EFIS system; the moving map; and comparing the pilot and co-pilot instruments. In addition; I cycled off the four gyro switches together and sequentially. (At no time were the radios off.) A contributor was loss of the altitude alert in my altitude pre-select; use of which is an important part of my IFR routine. As soon as I receive a new clearance; I dial in the cleared altitude and it was set to 16;000 in this case. Even when the autopilot is disengaged; this system normally provides an alert tone 1000 feet prior to the indicated altitude and an alert tone when 200' past the indicated altitude. Neither of these alerts sounded in this failure condition. Factors that could have prevented the altitude deviation and subsequent loss of separation:1. My attention to flying the airplane as a priority over diagnosis of the problem.2. Stopping the descent and letting ATC know that I was experiencing significant avionics issues as soon as they occurred. (I considered declaring an emergency; but did not as I had sufficient navigation information to complete the flight safely).3. Traffic call from ATC to inform me that opposite direction traffic would be passing just 1000 ft below my cleared altitude (not to deflect responsibility; but these calls are common and often helpful: I always read back my cleared altitude when I get these calls).

Data retrieved from NASA's ASRS site as of April 2012 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.