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At the beginning of a G4 autothrottle VNAV descent, a vibration was felt throughout the aircraft, and the left engine turbine gas temperature was climbing. The flight crew shut down the engine and the flight was diverted. Maintenance inspection found a faulty engine air control actuator.
| Attributes | |
| ACN | 324647 |
| Time | |
| Date | 199512 |
| Day | Tue |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : mke |
| State Reference | WI |
| Altitude | msl bound lower : 39000 msl bound upper : 39000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Operator | general aviation : corporate |
| Make Model Name | Gulfstream IV |
| Operating Under FAR Part | Part 91 |
| Navigation In Use | Other Other |
| Flight Phase | descent other |
| Route In Use | arrival other arrival star : star enroute airway : zax |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | Other |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 60 flight time total : 14000 flight time type : 15 |
| ASRS Report | 324647 |
| Person 2 | |
| Affiliation | Other |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | aircraft equipment problem : critical |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : declared emergency other |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
Narrative:
After starting an autothrottle VNAV descent on a STAR into dtw from oma, a vibration was felt throughout the aircraft. The left engine turbine gas temperature (tgt) was climbing toward 700 degrees and the fuel flow were all at normal VNAV reading. The left throttle was taken off autothrottles and reduced to idle. The tgt stayed high. The engine was shut down. A coordinated change of destination was done through ATC to make a single-engine (uneventful) landing at mke. The fault was found to be a bad engine air control actuator. ATC and mke approach and tower coordination was professional and flawless. Callback conversation with reporter revealed the following information: reporter states that a faulty engine air control actuator on the rolls- royce TAY611-8 turbofan engine caused improper positioning of the guide vanes. Poor engine air regulation basically compressor stalled the engine, which became visible as a high tgt. An emergency was not declared.
Original NASA ASRS Text
Title: AT THE BEGINNING OF A G4 AUTOTHROTTLE VNAV DSCNT, A VIBRATION WAS FELT THROUGHOUT THE ACFT, AND THE L ENG TURBINE GAS TEMP WAS CLBING. THE FLC SHUT DOWN THE ENG AND THE FLT WAS DIVERTED. MAINT INSPECTION FOUND A FAULTY ENG AIR CTL ACTUATOR.
Narrative: AFTER STARTING AN AUTOTHROTTLE VNAV DSCNT ON A STAR INTO DTW FROM OMA, A VIBRATION WAS FELT THROUGHOUT THE ACFT. THE L ENG TURBINE GAS TEMP (TGT) WAS CLBING TOWARD 700 DEGS AND THE FUEL FLOW WERE ALL AT NORMAL VNAV READING. THE L THROTTLE WAS TAKEN OFF AUTOTHROTTLES AND REDUCED TO IDLE. THE TGT STAYED HIGH. THE ENG WAS SHUT DOWN. A COORDINATED CHANGE OF DEST WAS DONE THROUGH ATC TO MAKE A SINGLE-ENG (UNEVENTFUL) LNDG AT MKE. THE FAULT WAS FOUND TO BE A BAD ENG AIR CTL ACTUATOR. ATC AND MKE APCH AND TWR COORD WAS PROFESSIONAL AND FLAWLESS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THAT A FAULTY ENG AIR CTL ACTUATOR ON THE ROLLS- ROYCE TAY611-8 TURBOFAN ENG CAUSED IMPROPER POSITIONING OF THE GUIDE VANES. POOR ENG AIR REGULATION BASICALLY COMPRESSOR STALLED THE ENG, WHICH BECAME VISIBLE AS A HIGH TGT. AN EMER WAS NOT DECLARED.
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.