A lear 35 had a partial flight instrument failure in solid IMC. The first officer suspected that the captain was flying poorly, then the first officer realized that both attitude instruments were faulty. The auxiliary gyroscope saved the day and both main attitude instruments later came back on line.

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Attributes
ACN	362252
Time
Date	199703
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : aml
State Reference	VA
Altitude	msl bound lower : 6500 msl bound upper : 9000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc
Operator	general aviation : corporate
Make Model Name	Learjet 35
Operating Under FAR Part	Part 91
Flight Phase	climbout : intermediate altitude cruise other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 95 flight time total : 2600 flight time type : 600
ASRS Report	362252
Person 2
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude conflict : airborne less severe inflight encounter : weather other anomaly other other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	flight crew : became reoriented flight crew : overcame equipment problem flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

On climb out, ATC advised us to climb to 9000 ft and turn to a 360 degree heading. The PF completed his climb and turn and, as he began to rollout on the assigned heading, I heard him say 'what the heck!' at that time I noticed the aircraft began to lose altitude, I called his name and said 'altitude' when I noticed a loss of 300 ft. The aircraft then began a rapid descent out of 9000 ft. We were IMC at the time. I took control of the aircraft when the loss of altitude was beyond 1000 ft. I initiated a recovery, but then realized my gyroscope was inoperative and we had now lost over 2500 ft. I then voiced my concern that I had no artificial horizon and the original PF took over and initiated a recovery with the peanut gyroscope. Soon after, his gyroscope returned to operation and my gyroscope began working 15 mins later. This instrument failure nearly killed us and our passenger. Callback conversation with reporter revealed the following information: the work on this aircraft is not yet complete, but the first officer's gyroscope has been replaced. This may have corrected the problem as the reporter believes that there was an interconnected problem from side to side. Nothing yet has been found wrong on the left side.

Original NASA ASRS Text

Title: A LEAR 35 HAD A PARTIAL FLT INST FAILURE IN SOLID IMC. THE FO SUSPECTED THAT THE CAPT WAS FLYING POORLY, THEN THE FO REALIZED THAT BOTH ATTITUDE INSTS WERE FAULTY. THE AUX GYROSCOPE SAVED THE DAY AND BOTH MAIN ATTITUDE INSTS LATER CAME BACK ON LINE.

Narrative: ON CLBOUT, ATC ADVISED US TO CLB TO 9000 FT AND TURN TO A 360 DEG HDG. THE PF COMPLETED HIS CLB AND TURN AND, AS HE BEGAN TO ROLLOUT ON THE ASSIGNED HEADING, I HEARD HIM SAY 'WHAT THE HECK!' AT THAT TIME I NOTICED THE ACFT BEGAN TO LOSE ALT, I CALLED HIS NAME AND SAID 'ALT' WHEN I NOTICED A LOSS OF 300 FT. THE ACFT THEN BEGAN A RAPID DSCNT OUT OF 9000 FT. WE WERE IMC AT THE TIME. I TOOK CTL OF THE ACFT WHEN THE LOSS OF ALT WAS BEYOND 1000 FT. I INITIATED A RECOVERY, BUT THEN REALIZED MY GYROSCOPE WAS INOP AND WE HAD NOW LOST OVER 2500 FT. I THEN VOICED MY CONCERN THAT I HAD NO ARTIFICIAL HORIZON AND THE ORIGINAL PF TOOK OVER AND INITIATED A RECOVERY WITH THE PEANUT GYROSCOPE. SOON AFTER, HIS GYROSCOPE RETURNED TO OP AND MY GYROSCOPE BEGAN WORKING 15 MINS LATER. THIS INST FAILURE NEARLY KILLED US AND OUR PAX. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE WORK ON THIS ACFT IS NOT YET COMPLETE, BUT THE FO'S GYROSCOPE HAS BEEN REPLACED. THIS MAY HAVE CORRECTED THE PROB AS THE RPTR BELIEVES THAT THERE WAS AN INTERCONNECTED PROB FROM SIDE TO SIDE. NOTHING YET HAS BEEN FOUND WRONG ON THE L SIDE.

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.