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Corporate flight crew forgets to power both AC inverters, discovers error while at cruise. The captain, intending to rectify the situation shut off the 1 inveter on-line, resulting in critical INS failure.
| Attributes | |
| ACN | 134927 |
| Time | |
| Date | 199001 |
| Day | Thu |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : boi |
| State Reference | ID |
| Altitude | msl bound lower : 30600 msl bound upper : 31000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Dusk |
| Aircraft 1 | |
| Controlling Facilities | artcc : zlc |
| Operator | general aviation : corporate |
| Make Model Name | Light Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other Other |
| Flight Phase | cruise other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | Other |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : flight engineer pilot : atp pilot : cfi |
| Experience | flight time last 90 days : 200 flight time total : 8400 flight time type : 700 |
| ASRS Report | 134927 |
| Person 2 | |
| Affiliation | Other |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : returned to intended course or assigned course |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
During cruise flight at FL310 with the aircraft on autoplt, the captain noticed that only 1 inverter was pwring the AC bus (the other inverter was off the line, inadvertently missed on taxi-out checklist). The captain reached up to the overhead panel to turn on the other inverter, but inadvertently shut off the good inverter, thus all aircraft power to the aircraft was lost, including the autoplt gyro INS, altimeters, air data computer, etc. The inverters were both brought on-line quickly, with complete recovery of all systems. However, unfortunately the captain allowed the aircraft to descent approximately 350' before all systems were recovered. Also this descent caused an overspd condition, further complicating the recovery to altitude. The controller asked our altitude just as we were releveling at FL310, so we replied 'level at 310.' no further comment was received from ATC. Contributing factors were: the PF answered the challenge during the taxi-out list, west/O actually checking the AC system; and the PF didn't continue to fly the aircraft with reference to the standby attitude indicator after AC power was lost. Corrective actions would include better adherence to checklist discipline and including in the briefing who flies the aircraft and who deals with the emergency procedure. In this case, the emergency was completely manmade.
Original NASA ASRS Text
Title: CORPORATE FLT CREW FORGETS TO POWER BOTH AC INVERTERS, DISCOVERS ERROR WHILE AT CRUISE. THE CAPT, INTENDING TO RECTIFY THE SITUATION SHUT OFF THE 1 INVETER ON-LINE, RESULTING IN CRITICAL INS FAILURE.
Narrative: DURING CRUISE FLT AT FL310 WITH THE ACFT ON AUTOPLT, THE CAPT NOTICED THAT ONLY 1 INVERTER WAS PWRING THE AC BUS (THE OTHER INVERTER WAS OFF THE LINE, INADVERTENTLY MISSED ON TAXI-OUT CHKLIST). THE CAPT REACHED UP TO THE OVERHEAD PANEL TO TURN ON THE OTHER INVERTER, BUT INADVERTENTLY SHUT OFF THE GOOD INVERTER, THUS ALL ACFT PWR TO THE ACFT WAS LOST, INCLUDING THE AUTOPLT GYRO INS, ALTIMETERS, AIR DATA COMPUTER, ETC. THE INVERTERS WERE BOTH BROUGHT ON-LINE QUICKLY, WITH COMPLETE RECOVERY OF ALL SYSTEMS. HOWEVER, UNFORTUNATELY THE CAPT ALLOWED THE ACFT TO DSCNT APPROX 350' BEFORE ALL SYSTEMS WERE RECOVERED. ALSO THIS DSCNT CAUSED AN OVERSPD CONDITION, FURTHER COMPLICATING THE RECOVERY TO ALT. THE CTLR ASKED OUR ALT JUST AS WE WERE RELEVELING AT FL310, SO WE REPLIED 'LEVEL AT 310.' NO FURTHER COMMENT WAS RECEIVED FROM ATC. CONTRIBUTING FACTORS WERE: THE PF ANSWERED THE CHALLENGE DURING THE TAXI-OUT LIST, W/O ACTUALLY CHKING THE AC SYS; AND THE PF DIDN'T CONTINUE TO FLY THE ACFT WITH REF TO THE STANDBY ATTITUDE INDICATOR AFTER AC PWR WAS LOST. CORRECTIVE ACTIONS WOULD INCLUDE BETTER ADHERENCE TO CHKLIST DISCIPLINE AND INCLUDING IN THE BRIEFING WHO FLIES THE ACFT AND WHO DEALS WITH THE EMER PROC. IN THIS CASE, THE EMER WAS COMPLETELY MANMADE.
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.