Skip to content

CHI91MA260

1991-08-12 · ST LOUIS, Missouri, United States · None · 1 aircraft · Status: Completed

Airport STL

Aircraft involved

Probable cause & findings

FAILURE OF THE PILOT(S) TO FOLLOW THE CORRECT EMERGENCY PROCEDURE. FACTORS RELATED TO THIS ACCIDENT WERE: INADEQUATE SYSTEM DESIGN BY THE MANUFACTURER, WHICH ALLOWED HYDRAULIC LINE VIBRATION, FATIGUE FAILURE OF THE LINE, AND LOSS OF FLUID FROM THE NORMAL HYDRAULIC SYSTEM.

Factual narrative

DRG FLT, A HYDR LINE (PN 137311D1443) IN THE MAIN HYDR SYS FAILED. THE CAPT & 1ST OFFICER MADE NUMEROUS ATMTS TO EXTD THE LNDG GEAR BY USING THE EMERG CHECKLIST & ACFT FLT MANUAL. TWO OF 3 LNDG GEAR LEGS WERE EXTDD, BUT THE PLTS WERE UNABLE TO EXTD THE LEFT MAIN LNDG GEAR. SUBSEQENTLY, THE ACFT WAS DMGD DRG LNDG. THE HYDR LINE WAS CURVED & MEASURED ABT 15' FM END TO END. IT HAD FAILED AT THE BASE OF A FLARED FITTING. THIS ALLOWED HYDR FLUID IN THE MAIN SYS RESERVOIR TO BE PUMPED OVERBOARD. THE EMERG HYDR SYS HAD A 3 PSN SLCTR: NORMAL, FLAPS DOWN, GEAR DOWN. TESTS OF THE GEAR EXTN SYS REVEALED IT WORKED PROPERLY PER INSTRNS FM THE EMERG CHECKLIST, BUT WITH THE SLCTR IN THE NORMAL PSN, THE LINE FAILURE ALLOWED FLUID TO BE PUMPED FM THE EMERG RESERVOIR TO THE MAIN SYS. A METALLURGICAL EXAM REVEALED THE HYDR LINE HAD FAILED FM MULTIPLE FATIGUE ORIGINS ON THE OUTSIDE DIAMETER OF THE TUBE & ON DIAMETRICALLY OPPOSITE SIDES. LATER, BRITISH AEROSPACE ISSUED A SVC BULLETIN (23-JM-8170) TO REINFORCE THE HYDR LINE. Source: NTSB Aviation Accident Database (Pre-2008 Archive) Retrieved: 2026-02-12

Verbatim from NTSB's published report. Source file NTSB_1991_CHI91MA260.txt. Findings + structured fields enriched from FAA avall.mdb. Full investigation docket on data.ntsb.gov ↗.

Search this event elsewhere

External sources are reported, not agency: signal that something happened, not fact about what happened.