# NTSB ATL87IA067: Burkhart Grob G103 Twin Astir, N429BG, Williamson, GA, January 31, 1987

- Type: NTSB incident investigation
- Classification: Incident · No injuries · Incident investigation · Final report
- Date: January 31, 1987, 12:25 local (17:25 UTC)
- Place: Williamson, GA
- Coordinates: 33.179519, -84.35968 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=33.1795&lon=-84.3597&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed
- Report: Approved by Office Director
- Safety recommendations: Yes
- NTSB case key (mKey): 7330
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ATL87IA067
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/7330/pdf
- Page: https://openairdocs.org/ntsb/ATL87IA067

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, approach
  - flt control syst,wing spoiler system - fatigue (cause)
  - acft/equip,inadequate aircraft component, production/design personnel (cause)
  - inadequate quality control, manufacturer (cause)
  - flt control syst,wing spoiler system - failure,total (cause)
  - spoiler retraction - not possible
- Forced landing, maneuvering - turn to landing area (emergency)
  - planned approach - not possible

## Analysis

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.

## Aircraft

- Registration: [N429BG](https://openairdocs.org/aircraft/N429BG), registered now, S/N 3737, built 1982 (OpenAirDocs)
- Reported make and model: BURKHART GROB G103 TWIN ASTIR (G103 TWIN)
- Registry model: [Burkhart Grob Flugzeugbau G103 TWIN ASTIR](https://openairdocs.org/model/burkhart-grob-flugzeugbau-g103-twin-astir) (registry code 1660202) (OpenAirDocs)
- Registry engine: [NONE](https://openairdocs.org/engine/none) (registry code 00000, none) (OpenAirDocs)
- Category: Glider
- Serial number: 3737
- Airframe hours: 1341
- Engines: unknown UNK unknown
- Damage: Minor damage
- Flight: Instructional, Part 91
- Operator: Atlanta Soaring Club
- Registered owner: Astro Tec Air, Inc.
- Airworthiness certificate: Standard, Utility
- Airport: 3GA7, Peach State Gliderport, runway 31, 3,300 × 100 ft, grass/turf

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 33; airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--w/ waivers/lim; seat: front; flight hours: 4,965 total, 6 in this make and model, 4,780 as pilot in command, 164 in the last 90 days, 2 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 330° at 13 knots
- Visibility: 15 statute miles
- Lowest ceiling: none
- Temperature: 46 °F, dew point 19 °F
- Altimeter: 30.00 inHg
- Observed at: ATL, 15 nm away

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Incident 19870131004089I](https://openairdocs.org/incident/19870131004089I), Jan 31, 1987: Grob G103TWNASTIR, Williamson, GA. Forced landing due to deployed atr brakes.

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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