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DEN90FA017

1989-10-31 · LARAMIE, Wyoming, United States · Fatal · 1 aircraft · Status: Completed

Airport LAR

Aircraft involved

Probable cause & findings

THE LOSS OF CONTROL OF THE AIRPLANE IN INSTRUMENT METEOROLOGICAL CONDITIONS AFTER THE PILOT BECAME SPATIALLY DISORIENTED. CONTRIBUTING TO THE ACCIDENT WAS THE FAILURE OF THE VACUUM SYSTEM WHICH RENDERED THE VACUUM/GYRO INSTRUMENTS INOPERATIVE. ALSO CONTRIBUTING TO THIS FAILURE WAS THE IMPROPER INSTALLATION OF THE VACUUM PUMP BY UNKNOWN PERSON(S).

Factual narrative

THE PLT RECEIVED A WEATHER BRIEFING FOR A VFR FLT. THE BRIEFING INDICATED IFR WEATHER ALONG THE INTENDED ROUTE OF FLIGHT. THE PLT STATED HE WAS CONDUCTING THE FLT VFR BECAUSE HE 'DID NOT TRUST HIS INSTRUMENTS.' APPROXIMATELY ONE HOUR AFTER DEPARTURE FROM LARAMIE, WY, THE PLT REQUESTED THE LARAMIE WEATHER IN AN ATTEMPT TO RETURN. THE PLT RADIOED HE LOST HIS GYROS AND DECLARED AN EMERGENCY. THE FSS RECEIVED A SPECIAL VFR CLEARANCE DUE TO BELOW VFR MINIMUM WEATHER, BUT WAS UNABLE TO ISSUE IT DUE TO LOST RADIO COMMUNICATIONS. POST-ACCIDENT INVESTIGATION REVEALED THE VACUUM PUMP HAD BEEN INSTALLED WITHOUT THE SHEAR SHAFT COUPLING. THE AIRFRAME AND ENGINE LOGBOOKS DID NOT IDENTIFY PREVIOUS WORK PERFORMED OR PERSON(S) WHO MAY HAVE WORKED ON THE PUMP. Source: NTSB Aviation Accident Database (Pre-2008 Archive) Retrieved: 2026-02-12

Verbatim from NTSB's published report. Source file NTSB_1989_DEN90FA017.txt. Findings + structured fields enriched from FAA avall.mdb. Full investigation docket on data.ntsb.gov ↗.

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