NTSB Identification: CHI91MA260.
The docket is stored on NTSB microfiche number 45555.
Scheduled 14 CFR
Accident occurred Monday, August 12, 1991 in ST LOUIS, MO
Probable Cause Approval Date: 03/02/1993
Aircraft: BRITISH AEROSPACE 3201, registration: N339TE
Injuries: 7 Uninjured.

NTSB investigators traveled in support of this investigation and used data obtained from various sources to prepare this aircraft accident report.

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.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

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.

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