# NTSB ATL91IA134: de Havilland DHC-8-102, N922HA, Savannah, GA, July 17, 1991

- Type: NTSB incident investigation
- Classification: Incident · No injuries · Incident investigation · Final report
- Date: July 16, 1991, 20:25 local (Jul 17, 1991, 00:25 UTC)
- Place: Savannah, GA
- Coordinates: 32.120975, -81.180801 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=32.1210&lon=-81.1808&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 5 uninjured
- Status: Completed, report March 9, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 8346
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ATL91IA134
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/8346/pdf
- Page: https://openairdocs.org/ntsb/ATL91IA134

## Probable cause

THE INADEQUATE INSPECTION PROCEDURES WHICH ALLOWED THE LOSS OF TORQUE ON THE TOP RETRACTION FITTING ATTACHMENT BOLT WHICH SUBSEQUENTLY FAILED IN FATIGUE. FACTORS WERE THE LOSS OF  HYDRAULIC FLUID THROUGH A SEVERED LINE, AND THE CORROSION OF A HYDRAULIC QUANTITY LIMITING VALVE.

## Sequence of events

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

- Airframe/component/system failure/malfunction, climb - to cruise
  - landing gear,normal retraction/extension assembly - loose (cause)
  - maintenance,inspection - inadequate (cause)
  - procedure inadequate, manufacturer
  - landing gear,normal retraction/extension assembly - fatigue (cause)
  - hydraulic system,line - sheared
  - fluid,hydraulic - loss,total (contributing factor)
  - hydraulic system,shutoff valve - failure,total (contributing factor)
  - hydraulic system,shutoff valve - corroded (contributing factor)
  - landing gear,normal retraction/extension assembly - fractured
  - miscellaneous equipment - inadequate, manufacturer
  - inadequate quality control, manufacturer

## Analysis

AFTER FLT 4317 TOOK OFF, THE MAIN LNDG GEAR DID NOT RETRACT. THE FLT CREW ACCOMPLISHED THE EMERG CHECKLIST, EXTDD THE LNDG GEAR & MADE AN UNEVENTFUL LNDG. AN EXAM OF THE ACFT DISCLOSED THAT THE RGT LNDG GEAR RETRACTION FITTING HAD FAILED & A HYDRAULIC LINE WAS SEVERED. ALSO, THE QUANTITY LIMITING VALVE(S) WERE CORRODED & THE RESPECTIVE PISTON MOVEMENT WAS RESTRICTED. SUBSEQUENTLY, BOTH HYDRAULIC SYSTEMS WERE DRAIN OF FLUID. AN EXAM OF THE FITTING ATTACHMENT BOLTS REVEALED THE TOP BOLT LOST TORQUE & THE BOLT FAILED IN FATIGUE; THE BOTTOM BOLTS FAILED IN OVERLOAD. ADNLY, THE FITTING SPIGOT FAILED DUE TO HYDROGEN EMBRITTLEMENT; AN IMPROVED FITTING HAS BEEN PRODUCED TO CORRECT HYDROGEN EMBRITTLEMENT PROBLEMS. THE OPER CONDUCTED A FLEET CAMPAIGN & FND 13 LOOSE BOLTS IN OTHER 100 SERIES ACFT. SVRL AIRWORTHINESS DIRECTIVES WERE ISSUED TO CORRECT THE LOSS OF TORQUE ON ATTACHMENT BOLTS, WHICH INCLUDED CHECKING THE TORQUE AT THE 300 HR LNDG GEAR INSPN.

## Aircraft

- Registration: [N922HA](https://openairdocs.org/deregistered/N922HA-2002-10-31), registration cancelled 2002-10-31, S/N 094 (OpenAirDocs)
- Reported make and model: de Havilland DHC-8-102
- Registry model: [Dehavilland DHC-8-102](https://openairdocs.org/model/dehavilland-dhc-8-102) (registry code 2809003) (OpenAirDocs)
- Registry engine: [Pratt & Whitney Canada PW120](https://openairdocs.org/engine/pratt-whitney-canada-pw120) (registry code 52114, turbo-prop) (OpenAirDocs)
- Category: Airplane
- Serial number: 094
- Airframe hours: 9081
- Engines: P&W 120A 2000 horsepower turbo prop
- Damage: Minor damage
- Flight: Part 121
- Operator: Henson Airlines
- Registered owner: Westinghouse Credit Corp
- Airworthiness certificate: Standard, Transport
- Last inspection: Continuous airworthiness, July 12, 1991, 25 hours before
- Departed: 49J, HILTON HEAD ISL, SC
- Destination: JAX, JACKSONVILLE, FL
- Flight plan: IFR
- Airport: SAV, Savannah, runway 27, 9,003 × 150 ft, asphalt

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 32; commercial, airline transport, flight instructor; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--w/ waivers/lim; seat: left; flight hours: 8,671 total, 2,359 in this make and model, 5,375 as pilot in command, 6 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Dusk
- Wind: 270° at 6 knots
- Visibility: 8 statute miles
- Lowest ceiling: 1,100 ft broken
- Temperature: 77 °F, dew point 75 °F
- Altimeter: 29.00 inHg
- Observed at: SAV, 1 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 19910716033829I](https://openairdocs.org/incident/19910716033829I), Jul 16, 1991: Dhav DHC8102, Savannah, GA. Aircraft lost hydraulic fluid when gear retracted. Landed safely. Right gear retraction actuator loose. Cut lines.

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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