Narrative:

A descent clearance was received to FL240 and slow to 250 KTS. The descent was made in flight level change with idle thrust. Upon level off abnormal indications were observed. The right engine eec and elc light came on with a autothrottle disconnect. The level off had just been accomplished so the thrust levers may have been at idle or just advancing to the mid-position. Our involvement with the checklist and dependency on autothrottles had allowed the airspeed to reduce to approximately 210 KTS. The thrust levers were advanced with no engine response. I further advanced the power to establish our assigned speed and observed very slow acceleration. Not satisfied with thrust response and slow airspeed increase I promptly pushed the thrust levers forward and experienced a notable compressor stall from the right engine. Engine instrument indications were normal. The passenger cabin was filled with an acrid odor and trace of smoke. We informed ATC of our problem and continued the arrival to runway 25R. After several vectors we were now cleared for the approach to runway 24R. At the final fix we were instructed to go around because of slow traffic. Upon application of thrust the acrid odor was again entering the cabin. We declared an emergency to expedite our approach and landing. I consider the decision to declare an emergency prudent because the status of the aircraft and system was unknown, the workload was high and fuel was approaching 8500 pounds. We were immediately vectored back and made a normal landing. The fire department inspected the engine and we proceeded to the gate. In discussion with maintenance rolls royce has issued an airworthiness directive termed 'run down.' this is a fuel control problem that results from descent with idle thrust resulting in a near flameout condition with slow thrust response. Emphasize less dependency on automation (autothrottles). Gain more knowledge concerning 'run down' and operating procedures or corrective maintenance to avoid this anomaly.

Google
 

Original NASA ASRS Text

Title: ACFT EQUIP PROB. R ENG ELECTRONIC ENG CTL, EEC, AND ENG LIMITER CTL, ELC, LIGHTS CAME ON DURING DSCNT WITH ACCOMPANYING AUTOTHROTTLE DISCONNECT. AIRSPD GOT SLOW WHEN AUTOTHROTTLES DIDN'T ADVANCE AT LEVEL OFF. THRUST LEVERS PUSHED UP MANUALLY WITH RESULTANT COMPRESSOR STALL AND CAUSING ACRID SMOKE TO ENTER ACFT CABIN. EMER DECLARED AFTER A GAR FOR SLOW TFC ON FINAL.

Narrative: A DSCNT CLRNC WAS RECEIVED TO FL240 AND SLOW TO 250 KTS. THE DSCNT WAS MADE IN FLT LEVEL CHANGE WITH IDLE THRUST. UPON LEVEL OFF ABNORMAL INDICATIONS WERE OBSERVED. THE R ENG EEC AND ELC LIGHT CAME ON WITH A AUTOTHROTTLE DISCONNECT. THE LEVEL OFF HAD JUST BEEN ACCOMPLISHED SO THE THRUST LEVERS MAY HAVE BEEN AT IDLE OR JUST ADVANCING TO THE MID-POS. OUR INVOLVEMENT WITH THE CHKLIST AND DEPENDENCY ON AUTOTHROTTLES HAD ALLOWED THE AIRSPD TO REDUCE TO APPROX 210 KTS. THE THRUST LEVERS WERE ADVANCED WITH NO ENG RESPONSE. I FURTHER ADVANCED THE PWR TO ESTABLISH OUR ASSIGNED SPD AND OBSERVED VERY SLOW ACCELERATION. NOT SATISFIED WITH THRUST RESPONSE AND SLOW AIRSPD INCREASE I PROMPTLY PUSHED THE THRUST LEVERS FORWARD AND EXPERIENCED A NOTABLE COMPRESSOR STALL FROM THE R ENG. ENG INST INDICATIONS WERE NORMAL. THE PAX CABIN WAS FILLED WITH AN ACRID ODOR AND TRACE OF SMOKE. WE INFORMED ATC OF OUR PROB AND CONTINUED THE ARR TO RWY 25R. AFTER SEVERAL VECTORS WE WERE NOW CLRED FOR THE APCH TO RWY 24R. AT THE FINAL FIX WE WERE INSTRUCTED TO GAR BECAUSE OF SLOW TFC. UPON APPLICATION OF THRUST THE ACRID ODOR WAS AGAIN ENTERING THE CABIN. WE DECLARED AN EMER TO EXPEDITE OUR APCH AND LNDG. I CONSIDER THE DECISION TO DECLARE AN EMER PRUDENT BECAUSE THE STATUS OF THE ACFT AND SYS WAS UNKNOWN, THE WORKLOAD WAS HIGH AND FUEL WAS APCHING 8500 LBS. WE WERE IMMEDIATELY VECTORED BACK AND MADE A NORMAL LNDG. THE FIRE DEPT INSPECTED THE ENG AND WE PROCEEDED TO THE GATE. IN DISCUSSION WITH MAINT ROLLS ROYCE HAS ISSUED AN AIRWORTHINESS DIRECTIVE TERMED 'RUN DOWN.' THIS IS A FUEL CTL PROB THAT RESULTS FROM DSCNT WITH IDLE THRUST RESULTING IN A NEAR FLAMEOUT CONDITION WITH SLOW THRUST RESPONSE. EMPHASIZE LESS DEPENDENCY ON AUTOMATION (AUTOTHROTTLES). GAIN MORE KNOWLEDGE CONCERNING 'RUN DOWN' AND OPERATING PROCS OR CORRECTIVE MAINT TO AVOID THIS ANOMALY.

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.