Narrative:

I believe the most important part of this narrative may be the significance of the equipment in use at the time of the incident so will start with that. The incident involves the failure of GPS and possibly autoplt while on an instrument flight plan in IMC over the mountains of northern idaho. I am the PIC and my husband was flying this leg, the first in a trip to california and texas. Both of us are instrument rated private pilots. We fly a beech A36TC and equipped it in june of last yr with a complete new panel including a garmin 155 tso, century 2000 autoplt and morrow 5000 moving map. On sep/xx/96, we took off from libby, mt, at XA00 pm mdt (S59) en route to davis, ca, (0o5). We filed an instrument flight plan to be picked up at about 9000 ft MSL as we climbed out. (Communication with ZLC is usually available at about that altitude). We climbed out, contacted center and ended up on top but shortly thereafter entered IMC. Everything was performing flawlessly. We were on the autoplt and GPS direct to davis. About 30 mins into the flight I was checking charts and monitoring the GPS. My husband glanced out the window to check the wings as we had some concerns about possible icing. We were level at 11000 ft. At that moment I was checking GPS ete to determine about what time we would get to davis. Everything was normal estimating 3 hours 45 mins. Suddenly the ete display began counting upwards rapidly and erratically, 8 hours, 11, 15, etc. I had never seen that before and immediately called my husband's attention to it. We were baffled and spent precious seconds trying to figure out what was going on as the rest of the display appeared normal. A glance back to the instrument panel showed the gauges scrambled. We were in a diving steep left turn and picking up speed horrifyingly fast (over 2000 FPM). My husband hit the autoplt disengage button on the yoke, leveled the wings, pulled back the power, dropped the gear and flaps and finally was able to get the plane under control. We broke out at about 7000 ft MSL and far too close to terrain for comfort still without having an idea what was going on and how much control we had left. In the meantime I had called center to let them know we had a problem and simply said we had 'lost everything' because at the moment we thought we had. We didn't know what we could trust since we already knew that at least the GPS and possibly autoplt had apparently failed and we didn't know what else was damaged or wrong. As we were able to get things under control center offered vectors to a nearby strip and we found we were almost over it. We also had used the emergency option on the moving map which also located that strip (magee, identification, a fire service strip). At that point we had the airplane stabilized and elected to circle while we evaluated the problem. Finally we decided the plane was ok mechanically and the basic instruments were working. We elected to go VFR to spokane, wa, (geg), a field we know well, where we could take a hard look at everything and decide whether we should continue. We were able to stay low and under the clouds to spokane with no problem and center was most helpful. In spokane we contacted company in billings, mt, which sold and installed the system. The man there was unable to offer much help as he had never heard of the problem before. He suggested we try reseating the chip. Perhaps I should mention that we have received at least 1 faulty chip from commercial company which we had to return but there had been no indication of a problem when we put this one in the day before the trip and checked it out. After thorough evaluation and with the knowledge that we had no more instrument WX along our route we decided to go on and cautiously evaluate both the autoplt and GPS as we went. We had a good flight with no more problems and are as much in the dark now after hours of discussion as we were at the moment it happened. Our best guess is a failure in the link between the autoplt and GPS, or hiccup in the satellite connection. We naturally want to know whether anyone else has experienced this problem. Evaluation: in the past yr and a half we havebecome quite comfortable with and confident of the system although we are not yet comfortable enough to do GPS approachs in IMC. We use GPS to the area then fly standard approachs. We have been impressed with the accuracy and ease of our practice GPS approachs. The weird part was that never at any time was there any sensation of turning or falling, no alarms, horns, nothing to indicate a problem despite the sudden onset but the gauges. It was totally unlike unusual attitudes as practiced in biannuals, instrument instruction, etc. As to personal performance, etc, we allowed ourselves to become fixated on the GPS problem and did not check immediately on the basic flight instruments. We probably have become somewhat complacent with the excellent performance of the GPS and autoplt and did not immediately consider the possibility of a problem of this sort since we had never heard of such a thing.

Related reports:

Google
 

Original NASA ASRS Text

Title: FLC OF A BEECH ACFT, IN CRUISE FLT AT 11000 FT MSL IN IMC ENCOUNTERED A MALFUNCTIONING GPS AND AUTOPLT. IN THE EVENT, THE FLC LOST CTL OF THE ACFT OVER MOUNTAINOUS TERRAIN. FLC REGAINED CTL AT 7000 FT MSL AND DIVERTED TO GEG VFR.

Narrative: I BELIEVE THE MOST IMPORTANT PART OF THIS NARRATIVE MAY BE THE SIGNIFICANCE OF THE EQUIP IN USE AT THE TIME OF THE INCIDENT SO WILL START WITH THAT. THE INCIDENT INVOLVES THE FAILURE OF GPS AND POSSIBLY AUTOPLT WHILE ON AN INST FLT PLAN IN IMC OVER THE MOUNTAINS OF NORTHERN IDAHO. I AM THE PIC AND MY HUSBAND WAS FLYING THIS LEG, THE FIRST IN A TRIP TO CALIFORNIA AND TEXAS. BOTH OF US ARE INST RATED PVT PLTS. WE FLY A BEECH A36TC AND EQUIPPED IT IN JUNE OF LAST YR WITH A COMPLETE NEW PANEL INCLUDING A GARMIN 155 TSO, CENTURY 2000 AUTOPLT AND MORROW 5000 MOVING MAP. ON SEP/XX/96, WE TOOK OFF FROM LIBBY, MT, AT XA00 PM MDT (S59) ENRTE TO DAVIS, CA, (0O5). WE FILED AN INST FLT PLAN TO BE PICKED UP AT ABOUT 9000 FT MSL AS WE CLBED OUT. (COM WITH ZLC IS USUALLY AVAILABLE AT ABOUT THAT ALT). WE CLBED OUT, CONTACTED CTR AND ENDED UP ON TOP BUT SHORTLY THEREAFTER ENTERED IMC. EVERYTHING WAS PERFORMING FLAWLESSLY. WE WERE ON THE AUTOPLT AND GPS DIRECT TO DAVIS. ABOUT 30 MINS INTO THE FLT I WAS CHKING CHARTS AND MONITORING THE GPS. MY HUSBAND GLANCED OUT THE WINDOW TO CHK THE WINGS AS WE HAD SOME CONCERNS ABOUT POSSIBLE ICING. WE WERE LEVEL AT 11000 FT. AT THAT MOMENT I WAS CHKING GPS ETE TO DETERMINE ABOUT WHAT TIME WE WOULD GET TO DAVIS. EVERYTHING WAS NORMAL ESTIMATING 3 HRS 45 MINS. SUDDENLY THE ETE DISPLAY BEGAN COUNTING UPWARDS RAPIDLY AND ERRATICALLY, 8 HRS, 11, 15, ETC. I HAD NEVER SEEN THAT BEFORE AND IMMEDIATELY CALLED MY HUSBAND'S ATTN TO IT. WE WERE BAFFLED AND SPENT PRECIOUS SECONDS TRYING TO FIGURE OUT WHAT WAS GOING ON AS THE REST OF THE DISPLAY APPEARED NORMAL. A GLANCE BACK TO THE INST PANEL SHOWED THE GAUGES SCRAMBLED. WE WERE IN A DIVING STEEP L TURN AND PICKING UP SPD HORRIFYINGLY FAST (OVER 2000 FPM). MY HUSBAND HIT THE AUTOPLT DISENGAGE BUTTON ON THE YOKE, LEVELED THE WINGS, PULLED BACK THE PWR, DROPPED THE GEAR AND FLAPS AND FINALLY WAS ABLE TO GET THE PLANE UNDER CTL. WE BROKE OUT AT ABOUT 7000 FT MSL AND FAR TOO CLOSE TO TERRAIN FOR COMFORT STILL WITHOUT HAVING AN IDEA WHAT WAS GOING ON AND HOW MUCH CTL WE HAD LEFT. IN THE MEANTIME I HAD CALLED CTR TO LET THEM KNOW WE HAD A PROB AND SIMPLY SAID WE HAD 'LOST EVERYTHING' BECAUSE AT THE MOMENT WE THOUGHT WE HAD. WE DIDN'T KNOW WHAT WE COULD TRUST SINCE WE ALREADY KNEW THAT AT LEAST THE GPS AND POSSIBLY AUTOPLT HAD APPARENTLY FAILED AND WE DIDN'T KNOW WHAT ELSE WAS DAMAGED OR WRONG. AS WE WERE ABLE TO GET THINGS UNDER CTL CTR OFFERED VECTORS TO A NEARBY STRIP AND WE FOUND WE WERE ALMOST OVER IT. WE ALSO HAD USED THE EMER OPTION ON THE MOVING MAP WHICH ALSO LOCATED THAT STRIP (MAGEE, ID, A FIRE SVC STRIP). AT THAT POINT WE HAD THE AIRPLANE STABILIZED AND ELECTED TO CIRCLE WHILE WE EVALUATED THE PROB. FINALLY WE DECIDED THE PLANE WAS OK MECHANICALLY AND THE BASIC INSTS WERE WORKING. WE ELECTED TO GO VFR TO SPOKANE, WA, (GEG), A FIELD WE KNOW WELL, WHERE WE COULD TAKE A HARD LOOK AT EVERYTHING AND DECIDE WHETHER WE SHOULD CONTINUE. WE WERE ABLE TO STAY LOW AND UNDER THE CLOUDS TO SPOKANE WITH NO PROB AND CTR WAS MOST HELPFUL. IN SPOKANE WE CONTACTED COMPANY IN BILLINGS, MT, WHICH SOLD AND INSTALLED THE SYS. THE MAN THERE WAS UNABLE TO OFFER MUCH HELP AS HE HAD NEVER HEARD OF THE PROB BEFORE. HE SUGGESTED WE TRY RESEATING THE CHIP. PERHAPS I SHOULD MENTION THAT WE HAVE RECEIVED AT LEAST 1 FAULTY CHIP FROM COMMERCIAL COMPANY WHICH WE HAD TO RETURN BUT THERE HAD BEEN NO INDICATION OF A PROB WHEN WE PUT THIS ONE IN THE DAY BEFORE THE TRIP AND CHKED IT OUT. AFTER THOROUGH EVALUATION AND WITH THE KNOWLEDGE THAT WE HAD NO MORE INST WX ALONG OUR RTE WE DECIDED TO GO ON AND CAUTIOUSLY EVALUATE BOTH THE AUTOPLT AND GPS AS WE WENT. WE HAD A GOOD FLT WITH NO MORE PROBS AND ARE AS MUCH IN THE DARK NOW AFTER HRS OF DISCUSSION AS WE WERE AT THE MOMENT IT HAPPENED. OUR BEST GUESS IS A FAILURE IN THE LINK BTWN THE AUTOPLT AND GPS, OR HICCUP IN THE SATELLITE CONNECTION. WE NATURALLY WANT TO KNOW WHETHER ANYONE ELSE HAS EXPERIENCED THIS PROB. EVALUATION: IN THE PAST YR AND A HALF WE HAVEBECOME QUITE COMFORTABLE WITH AND CONFIDENT OF THE SYS ALTHOUGH WE ARE NOT YET COMFORTABLE ENOUGH TO DO GPS APCHS IN IMC. WE USE GPS TO THE AREA THEN FLY STANDARD APCHS. WE HAVE BEEN IMPRESSED WITH THE ACCURACY AND EASE OF OUR PRACTICE GPS APCHS. THE WEIRD PART WAS THAT NEVER AT ANY TIME WAS THERE ANY SENSATION OF TURNING OR FALLING, NO ALARMS, HORNS, NOTHING TO INDICATE A PROB DESPITE THE SUDDEN ONSET BUT THE GAUGES. IT WAS TOTALLY UNLIKE UNUSUAL ATTITUDES AS PRACTICED IN BIANNUALS, INST INSTRUCTION, ETC. AS TO PERSONAL PERFORMANCE, ETC, WE ALLOWED OURSELVES TO BECOME FIXATED ON THE GPS PROB AND DID NOT CHK IMMEDIATELY ON THE BASIC FLT INSTS. WE PROBABLY HAVE BECOME SOMEWHAT COMPLACENT WITH THE EXCELLENT PERFORMANCE OF THE GPS AND AUTOPLT AND DID NOT IMMEDIATELY CONSIDER THE POSSIBILITY OF A PROB OF THIS SORT SINCE WE HAD NEVER HEARD OF SUCH A THING.

Data retrieved from NASA's ASRS site as of July 2007 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.