AJ25. First officer lost control when afcs tripped off without first officer's knowledge.

Attributes
ACN	409355
Time
Date	199807
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : ilc
State Reference	NV
Altitude	msl bound lower : 36000 msl bound upper : 38000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zlc
Operator	general aviation : corporate
Make Model Name	IAI1125 (Astra)
Operating Under FAR Part	Part 91
Navigation In Use	Other Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : atp
Experience	flight time last 90 days : 50 flight time total : 9500 flight time type : 300
ASRS Report	409355
Person 2
Affiliation	Other
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : returned to intended course or assigned course flight crew : regained aircraft control
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Aircraft was being ferried to ags for a pre-buy inspection. No passenger onboard. After setting aircraft in cruise confign at FL370 I turned the aircraft over to the right seat pilot so that I could get the breakfast in the cabin's galley. While there I decided to check out the lavatory light that was continually on in the cockpit. Unable to easily find the cause of the light, I returned to eat my breakfast. About 5 mins into the meal, the aircraft suddenly began a rapid descending right turn. Entering the cockpit I found the first officer fighting to restore the aircraft attitude and return to FL370. In his effort to do so he overcorrected the controls to allow the aircraft to climb to FL380. Straight and level flight at FL370 was then resumed without further incident. ATC did not question the excursions of our altitude (from FL370 to FL360 to FL380 back to FL370). When the aircraft was back to normal flight I questioned the copilot for the reason. His response was that the autoplt had tripped off without him hearing it. His attention was on his chart reviewing our route of flight and did not notice that the aircraft was entering a spiral to the right until the altitude alerter went off. By that time the descent and bank had rapidly increased to where control was difficult without overstressing the plane. Fortunately there weren't any other aircraft in the immediate vicinity and no conflicts occurred. This occurrence could have been avoided if the pilot at the controls maintains a continuous monitoring of the autoplt and flight conditions while the other pilot is not at their station.

Original NASA ASRS Text

Title: AJ25. FO LOST CTL WHEN AFCS TRIPPED OFF WITHOUT FO'S KNOWLEDGE.

Narrative: ACFT WAS BEING FERRIED TO AGS FOR A PRE-BUY INSPECTION. NO PAX ONBOARD. AFTER SETTING ACFT IN CRUISE CONFIGN AT FL370 I TURNED THE ACFT OVER TO THE R SEAT PLT SO THAT I COULD GET THE BREAKFAST IN THE CABIN'S GALLEY. WHILE THERE I DECIDED TO CHK OUT THE LAVATORY LIGHT THAT WAS CONTINUALLY ON IN THE COCKPIT. UNABLE TO EASILY FIND THE CAUSE OF THE LIGHT, I RETURNED TO EAT MY BREAKFAST. ABOUT 5 MINS INTO THE MEAL, THE ACFT SUDDENLY BEGAN A RAPID DSNDING R TURN. ENTERING THE COCKPIT I FOUND THE FO FIGHTING TO RESTORE THE ACFT ATTITUDE AND RETURN TO FL370. IN HIS EFFORT TO DO SO HE OVERCORRECTED THE CTLS TO ALLOW THE ACFT TO CLB TO FL380. STRAIGHT AND LEVEL FLT AT FL370 WAS THEN RESUMED WITHOUT FURTHER INCIDENT. ATC DID NOT QUESTION THE EXCURSIONS OF OUR ALT (FROM FL370 TO FL360 TO FL380 BACK TO FL370). WHEN THE ACFT WAS BACK TO NORMAL FLT I QUESTIONED THE COPLT FOR THE REASON. HIS RESPONSE WAS THAT THE AUTOPLT HAD TRIPPED OFF WITHOUT HIM HEARING IT. HIS ATTN WAS ON HIS CHART REVIEWING OUR RTE OF FLT AND DID NOT NOTICE THAT THE ACFT WAS ENTERING A SPIRAL TO THE R UNTIL THE ALT ALERTER WENT OFF. BY THAT TIME THE DSCNT AND BANK HAD RAPIDLY INCREASED TO WHERE CTL WAS DIFFICULT WITHOUT OVERSTRESSING THE PLANE. FORTUNATELY THERE WEREN'T ANY OTHER ACFT IN THE IMMEDIATE VICINITY AND NO CONFLICTS OCCURRED. THIS OCCURRENCE COULD HAVE BEEN AVOIDED IF THE PLT AT THE CTLS MAINTAINS A CONTINUOUS MONITORING OF THE AUTOPLT AND FLT CONDITIONS WHILE THE OTHER PLT IS NOT AT THEIR STATION.

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.