Narrative:

Control column pitch oscillation noted at FL290, IMC conditions. Control column pitch oscillation checklist followed, maximum duration 30-45 seconds +/- 1 inch yolk oscillation. Engine rollback, unable to restart #1 engine. #1 engine shut down for approximately 25 mins. #2 engine shut down approximately 5-10 mins. #2, #3, and #4 engines recovered and landed without incident. Ice detector failed to indicate icing conditions. Aircraft diverted to dsm. Callback conversation with reporter revealed the following information: the rptrs fly the BAE146 in the mountains near den. At the time of the incident, they were flying at FL260, about 25 mi from any thunderstorm. There were several thunderstorms in the area and icing. The control oscillation bucked the aircraft so much, 'I thought we might go on our back!' the checklist requires the aircraft to be slowed by opening the speed brakes. The reporter did this and closed the throttles as well. The oscillation came under control, but the engines went to 'sub idle' with no thrust output. Both generators and hydraulic system went off line. There were electrical power spikes which may have compounded the problem. The aircraft was on battery power only. The reporter shut down #2 engine, then was able to relight it at 10000 ft. Engines #3 and #4 regained power at 10000 ft by themselves. #1 engine was never regained. The flight crew never used the word 'emergency' as they 'were fighting for their lives.' they got the message across to ZAU, who gave them assistance to dsm. The crew flew a simulator with an FAA inspector to show that they 'knew how to declare an emergency.' this was an exercise 'just to fill a square.' the reporter conferred with the FAA, NTSB and engine manufacturer. The aircraft is now 'restr to FL260, right in the middle of the thunderstorms and ice.' a modification is being made to the engines to add heat further aft to heat the fuel controllers. The reporter has heard of another incident where the engines could not be restarted until 1000 ft over the ocean. The engine and tail anti-ice were on at all times before and during the reporter's incident. Supplemental information from acn 336755: as oscillation was subsiding, we noted all 4 engines had rolled back to sub-idle and would not respond to thrust lever input. Declared emergency.

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Original NASA ASRS Text

Title: AN ACR BAE146 HAD AN ACFT EQUIP PROB ICE DETECTION MALFUNCTION. THIS LED TO CTL OSCILLATION AND ALL 4 ENGS ROLLING BACK TO LESS THAN IDLE THRUST.

Narrative: CTL COLUMN PITCH OSCILLATION NOTED AT FL290, IMC CONDITIONS. CTL COLUMN PITCH OSCILLATION CHKLIST FOLLOWED, MAX DURATION 30-45 SECONDS +/- 1 INCH YOLK OSCILLATION. ENG ROLLBACK, UNABLE TO RESTART #1 ENG. #1 ENG SHUT DOWN FOR APPROX 25 MINS. #2 ENG SHUT DOWN APPROX 5-10 MINS. #2, #3, AND #4 ENGS RECOVERED AND LANDED WITHOUT INCIDENT. ICE DETECTOR FAILED TO INDICATE ICING CONDITIONS. ACFT DIVERTED TO DSM. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTRS FLY THE BAE146 IN THE MOUNTAINS NEAR DEN. AT THE TIME OF THE INCIDENT, THEY WERE FLYING AT FL260, ABOUT 25 MI FROM ANY TSTM. THERE WERE SEVERAL TSTMS IN THE AREA AND ICING. THE CTL OSCILLATION BUCKED THE ACFT SO MUCH, 'I THOUGHT WE MIGHT GO ON OUR BACK!' THE CHKLIST REQUIRES THE ACFT TO BE SLOWED BY OPENING THE SPD BRAKES. THE RPTR DID THIS AND CLOSED THE THROTTLES AS WELL. THE OSCILLATION CAME UNDER CTL, BUT THE ENGS WENT TO 'SUB IDLE' WITH NO THRUST OUTPUT. BOTH GENERATORS AND HYD SYS WENT OFF LINE. THERE WERE ELECTRICAL PWR SPIKES WHICH MAY HAVE COMPOUNDED THE PROB. THE ACFT WAS ON BATTERY PWR ONLY. THE RPTR SHUT DOWN #2 ENG, THEN WAS ABLE TO RELIGHT IT AT 10000 FT. ENGS #3 AND #4 REGAINED PWR AT 10000 FT BY THEMSELVES. #1 ENG WAS NEVER REGAINED. THE FLC NEVER USED THE WORD 'EMER' AS THEY 'WERE FIGHTING FOR THEIR LIVES.' THEY GOT THE MESSAGE ACROSS TO ZAU, WHO GAVE THEM ASSISTANCE TO DSM. THE CREW FLEW A SIMULATOR WITH AN FAA INSPECTOR TO SHOW THAT THEY 'KNEW HOW TO DECLARE AN EMER.' THIS WAS AN EXERCISE 'JUST TO FILL A SQUARE.' THE RPTR CONFERRED WITH THE FAA, NTSB AND ENG MANUFACTURER. THE ACFT IS NOW 'RESTR TO FL260, RIGHT IN THE MIDDLE OF THE TSTMS AND ICE.' A MODIFICATION IS BEING MADE TO THE ENGS TO ADD HEAT FURTHER AFT TO HEAT THE FUEL CTLRS. THE RPTR HAS HEARD OF ANOTHER INCIDENT WHERE THE ENGS COULD NOT BE RESTARTED UNTIL 1000 FT OVER THE OCEAN. THE ENG AND TAIL ANTI-ICE WERE ON AT ALL TIMES BEFORE AND DURING THE RPTR'S INCIDENT. SUPPLEMENTAL INFO FROM ACN 336755: AS OSCILLATION WAS SUBSIDING, WE NOTED ALL 4 ENGS HAD ROLLED BACK TO SUB-IDLE AND WOULD NOT RESPOND TO THRUST LEVER INPUT. DECLARED EMER.

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.