NTSB Identification: ATL87IA067.
The docket is stored on NTSB microfiche number 33425.
Incident occurred Saturday, January 31, 1987 in WILLIAMSON, GA
Aircraft: BURKHART GROB G103 TWIN ASTIR, registration: N429BG
Injuries: 1 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

AS THE GLIDER PLT WAS APCHG THE ENTRY POINT FOR LANDING, HE CHECKED THE SPOILERS FOR OPERATION. THE SPOILERS EXTENDED, BUT WOULD NOT RETRACT. THERE WAS A SIGNIFICANT INCREASE IN THE SINK RATE & THE PLT REALIZED HE WOULD BE UNABLE TO REACH THE ARPT. SUBSEQUENTLY, HE LANDED THE GLIDER (SAILPLANE) APRX 1/4 MI NORTH OF THE ARPT. AN INVESTIGATION REVEALED THAT ABELLCRANK (PN 103B-4433) IN THE SPOILER CONTROL SYSTEM HAD FAILED AT TWO LOCATIONS ON THE CENTER BEARING HOUSING. A METALLURGICAL EXAM REVEALED THE BELLCRANK HAD FAILED FROM HIGH CYCLE, LOW STRESS FATIGUE. THE FAILURES OCCURRED AT THE EDGE OF FILLET-WELDS IN RELATIVELY SOFT, HEAT AFFECTED ZONES (HAZ). THE BELLCRANK HAD NOT BEEN SUBJECTED TO POST WELD HEAT TREATMENT. TESTS VERIFIED A SIGNIFICANT LOSS OF HARDNESS IN THE HAZ. THE GLIDER HAD A TOTAL FLT TIME OF 318 HRS WHEN THE BELLCRANK FAILED.

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

FLT CONTROL SYST,WING SPOILER SYSTEM..FATIGUE

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

ACFT/EQUIP,INADEQUATE AIRCRAFT COMPONENT..PRODUCTION/DESIGN PERSONNEL

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

INADEQUATE QUALITY CONTROL..MANUFACTURER

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

FLT CONTROL SYST,WING SPOILER SYSTEM..FAILURE,TOTAL


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