Narrative:

West of ZZZ at FL330; approximately 2000 ft below maximum habitable altitude; left throttle closed and engine went to deep idle. Airspeed deteriorated rapidly to 244 KTS. Captain initiated stall recovery technique as I coordination immediate descent with ATC and checked single engine drift down altitude (FL200). Prior to event we had been picking our way through numerous thunderstorms. I was operating radar while captain was checking paper map for deviation plan. The aircraft (1982 vintage) has no GPS map display and has old style center radar display. Engine and airfoil anti-ice was on as well as engine ignition. Engine sync was off (EPR sync mode). Tri was still in climb mode. We were; at that moment; in the clear and had; at no time during the entire flight encountered any visible ice on the ice detector ring. Automatic throttle was on with mach .75 selected. The cockpit was dark so the throttles were not visible. The aircraft began to slowly pitch up and the trim activation alert sounded. At that point we looked to the EPR gauges and saw the left EPR gauge pegged at the bottom. The right EPR was at the climb power bug. The captain immediately disengaged the autoplt and forced the nose down as he grabbed the throttles. I called ATC for the descent and stated that we had an apparent engine failure. When the captain manually moved the left throttle up; engine thrust returned and the engine operated normally. The descent was stopped at FL270 and the flight continued with constant monitoring of the left throttle and engine. Later in the flight the left throttle would move quickly fore and aft approximately one inch in each direction and then cease movement. It would also show EPR higher than right engine in spike of engine syn off (EPR sync mode). Questions: 1) why did automatic throttle move throttle past low limit into deep idle? 2) why did automatic throttle continue to function in mach on right throttle? 3) it was only the captain's quick response that prevented a stall. Is it possible that some of the MD80 stall events involved a similar scenario that was not noticed during stall recovery? Callback conversation with reporter revealed the following information: reporter is in the process of compiling a complete analysis and suggestion package regarding this incident. He believes that a mix of aircraft components from a previously purchased air carrier is not compatible with the existing fleet and allowing this to happen. Reportedly this is not the first such incident. The reporter stated if a pilot's seat is adjusted correctly (white and red balls aligned) then he cannot see the oil quantity gauges; adding if he leans forward; the oil quantity gauges are visible but the EPR gauges are not. In this case at night; the first officer stated he was examining the WX radar because they were picking their way through cells while the captain was looking at his airways chart. The reporter did not see the throttles move (lt to idle; rt to maximum climb;) and the first indication was the trim wheel moving; which can happen intermittently as fuel burns off. The reporter did not see the throttles move because they were out of both pilots' views and there is no engine sound in the flight station. Reportedly the FAA and air carrier have placed the onus on the pilots to prevent future maximum cruise altitude stalls. But without an indication; pilots have no warning of impending stall. Reporter's suggestion is to put something on the throttles to better highlight their position; even something as simple as painting them white. This pilot felt that he and the captain had performed as they should have given the circumstances. The captain reportedly demanded that the flight recorder be pulled upon arrival at their destination. It was discovered that a number of mins elapsed between throttle closure and recovery. The reporter indicated any more of these events and this air carrier will be banned from the rvsm airspace at a huge fuel cost. Another reported issue with this aircraft is performance. This system optimizes aircraft climb; cruise; and descent performance. The reporter stated that performance will; by design; allow altitude 'wandering in order to increase performance.' unfortunately the wandering will also violate rvsm limits.

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Original NASA ASRS Text

Title: AN MD80 NEARLY STALLED WHEN THE L THROTTLE AUTONOMOUSLY CLOSED; UNDETECTED BY THE CREW AT NIGHT IN WX AT MAX CRUISE ALT.

Narrative: W OF ZZZ AT FL330; APPROX 2000 FT BELOW MAX HABITABLE ALT; L THROTTLE CLOSED AND ENGINE WENT TO DEEP IDLE. AIRSPEED DETERIORATED RAPIDLY TO 244 KTS. CAPT INITIATED STALL RECOVERY TECHNIQUE AS I COORD IMMEDIATE DSCNT WITH ATC AND CHKED SINGLE ENGINE DRIFT DOWN ALT (FL200). PRIOR TO EVENT WE HAD BEEN PICKING OUR WAY THROUGH NUMEROUS THUNDERSTORMS. I WAS OPERATING RADAR WHILE CAPT WAS CHKING PAPER MAP FOR DEV PLAN. THE ACFT (1982 VINTAGE) HAS NO GPS MAP DISPLAY AND HAS OLD STYLE CTR RADAR DISPLAY. ENGINE AND AIRFOIL ANTI-ICE WAS ON AS WELL AS ENGINE IGNITION. ENGINE SYNC WAS OFF (EPR SYNC MODE). TRI WAS STILL IN CLB MODE. WE WERE; AT THAT MOMENT; IN THE CLR AND HAD; AT NO TIME DURING THE ENTIRE FLT ENCOUNTERED ANY VISIBLE ICE ON THE ICE DETECTOR RING. AUTO THROTTLE WAS ON WITH MACH .75 SELECTED. THE COCKPIT WAS DARK SO THE THROTTLES WERE NOT VISIBLE. THE ACFT BEGAN TO SLOWLY PITCH UP AND THE TRIM ACTIVATION ALERT SOUNDED. AT THAT POINT WE LOOKED TO THE EPR GAUGES AND SAW THE L EPR GAUGE PEGGED AT THE BOTTOM. THE R EPR WAS AT THE CLB POWER BUG. THE CAPT IMMEDIATELY DISENGAGED THE AUTOPLT AND FORCED THE NOSE DOWN AS HE GRABBED THE THROTTLES. I CALLED ATC FOR THE DSCNT AND STATED THAT WE HAD AN APPARENT ENGINE FAILURE. WHEN THE CAPT MANUALLY MOVED THE L THROTTLE UP; ENGINE THRUST RETURNED AND THE ENGINE OPERATED NORMALLY. THE DSCNT WAS STOPPED AT FL270 AND THE FLT CONTINUED WITH CONSTANT MONITORING OF THE L THROTTLE AND ENGINE. LATER IN THE FLT THE L THROTTLE WOULD MOVE QUICKLY FORE AND AFT APPROX ONE INCH IN EACH DIRECTION AND THEN CEASE MOVEMENT. IT WOULD ALSO SHOW EPR HIGHER THAN R ENGINE IN SPIKE OF ENG SYN OFF (EPR SYNC MODE). QUESTIONS: 1) WHY DID AUTO THROTTLE MOVE THROTTLE PAST LOW LIMIT INTO DEEP IDLE? 2) WHY DID AUTO THROTTLE CONTINUE TO FUNCTION IN MACH ON R THROTTLE? 3) IT WAS ONLY THE CAPT'S QUICK RESPONSE THAT PREVENTED A STALL. IS IT POSSIBLE THAT SOME OF THE MD80 STALL EVENTS INVOLVED A SIMILAR SCENARIO THAT WAS NOT NOTICED DURING STALL RECOVERY? CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR IS IN THE PROCESS OF COMPILING A COMPLETE ANALYSIS AND SUGGESTION PACKAGE REGARDING THIS INCIDENT. HE BELIEVES THAT A MIX OF ACFT COMPONENTS FROM A PREVIOUSLY PURCHASED ACR IS NOT COMPATIBLE WITH THE EXISTING FLEET AND ALLOWING THIS TO HAPPEN. REPORTEDLY THIS IS NOT THE FIRST SUCH INCIDENT. THE RPTR STATED IF A PLT'S SEAT IS ADJUSTED CORRECTLY (WHITE AND RED BALLS ALIGNED) THEN HE CANNOT SEE THE OIL QUANTITY GAUGES; ADDING IF HE LEANS FORWARD; THE OIL QUANTITY GAUGES ARE VISIBLE BUT THE EPR GAUGES ARE NOT. IN THIS CASE AT NIGHT; THE FO STATED HE WAS EXAMINING THE WX RADAR BECAUSE THEY WERE PICKING THEIR WAY THROUGH CELLS WHILE THE CAPT WAS LOOKING AT HIS AIRWAYS CHART. THE RPTR DID NOT SEE THE THROTTLES MOVE (LT TO IDLE; RT TO MAX CLB;) AND THE FIRST INDICATION WAS THE TRIM WHEEL MOVING; WHICH CAN HAPPEN INTERMITTENTLY AS FUEL BURNS OFF. THE RPTR DID NOT SEE THE THROTTLES MOVE BECAUSE THEY WERE OUT OF BOTH PLTS' VIEWS AND THERE IS NO ENGINE SOUND IN THE FLT STATION. REPORTEDLY THE FAA AND ACR HAVE PLACED THE ONUS ON THE PLTS TO PREVENT FUTURE MAX CRUISE ALT STALLS. BUT WITHOUT AN INDICATION; PLTS HAVE NO WARNING OF IMPENDING STALL. RPTR'S SUGGESTION IS TO PUT SOMETHING ON THE THROTTLES TO BETTER HIGHLIGHT THEIR POS; EVEN SOMETHING AS SIMPLE AS PAINTING THEM WHITE. THIS PLT FELT THAT HE AND THE CAPT HAD PERFORMED AS THEY SHOULD HAVE GIVEN THE CIRCUMSTANCES. THE CAPT REPORTEDLY DEMANDED THAT THE FLT RECORDER BE PULLED UPON ARR AT THEIR DEST. IT WAS DISCOVERED THAT A NUMBER OF MINS ELAPSED BETWEEN THROTTLE CLOSURE AND RECOVERY. THE RPTR INDICATED ANY MORE OF THESE EVENTS AND THIS ACR WILL BE BANNED FROM THE RVSM AIRSPACE AT A HUGE FUEL COST. ANOTHER RPTED ISSUE WITH THIS ACFT IS PERFORMANCE. THIS SYS OPTIMIZES ACFT CLB; CRUISE; AND DSCNT PERFORMANCE. THE RPTR STATED THAT PERFORMANCE WILL; BY DESIGN; ALLOW ALT 'WANDERING IN ORDER TO INCREASE PERFORMANCE.' UNFORTUNATELY THE WANDERING WILL ALSO VIOLATE RVSM LIMITS.

Data retrieved from NASA's ASRS site as of January 2009 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.