Jetstar first officer experienced an unnoticed autopilot disconnect at FL360 with the captain in the...

Attributes
ACN	1284082
Time
Date	201507
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Jetstar 1329 (C140)
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Autopilot
Person 1
Function	First Officer Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 15 Flight Crew Total 20000 Flight Crew Type 2000
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Track / Heading All Types Inflight Event / Encounter Loss Of Aircraft Control

Narrative:

The captain leaves flight station to go the lavatory. First officer flying. For unknown reason; autopilot disconnects when captain is in the back of the cabin. First officer does recover from unusual attitude when he receives airplane attitude nose low and left bank 45 degrees. Captain back to flight station; first officer calls center and advises of situation. Airplane is then hand-flown to resume altitude and route. Ap is checked and reengaged and monitored closely until the end of the flight. No other discrepancies or autopilot problem were encountered thereafter. Aircraft lost approximately 3;000 feet in the process. During and prior to the event; the captain had left the flight deck and first officer was flying (monitoring autopilot coupled flight at FL360) and programming the FMS when the autopilot disconnected and the aircraft rolled off into a diving left banked descend; losing 3;000 feet before the first officer could recover. In retrospect; first officer should have delayed diverting attention to the FMS until both pilots were at the flight station. A normal recovery from the unusual attitude was made and reported to ATC.

Original NASA ASRS Text

Title: Jetstar First Officer experienced an unnoticed autopilot disconnect at FL360 with the Captain in the lavatory. The aircraft is recovered from a 45 degree bank at FL330 and ATC is advised. The autopilot is reengaged and functions normally for the remainder of the flight.

Narrative: The Captain leaves flight station to go the lavatory. FO flying. For unknown reason; autopilot disconnects when captain is in the back of the cabin. FO does recover from unusual attitude when he receives airplane attitude nose low and left bank 45 degrees. Captain back to flight station; FO calls Center and advises of situation. Airplane is then hand-flown to resume altitude and route. AP is checked and reengaged and monitored closely until the end of the flight. No other discrepancies or autopilot problem were encountered thereafter. Aircraft lost approximately 3;000 feet in the process. During and prior to the event; the Captain had left the flight deck and FO was flying (monitoring Autopilot coupled flight at FL360) and programming the FMS when the autopilot disconnected and the aircraft rolled off into a diving left banked descend; losing 3;000 feet before the FO could recover. In retrospect; FO should have delayed diverting attention to the FMS until both pilots were at the flight station. A normal recovery from the unusual attitude was made and reported to ATC.

Data retrieved from NASA's ASRS site 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.

Jetstar first officer experienced an unnoticed autopilot disconnect at FL360 with the captain in the lavatory. The aircraft is recovered from a 45 degree bank at FL330 and ATC is advised. The autopilot is reengaged and functions normally for the remainder of the flight.