# NTSB LAX95LA138: Bell 47, N6569H, Harmon Field, March 17, 1995 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: March 17, 1995 - Place: Harmon Field - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report September 24, 1995 - Report: Approved by Office Director - NTSB case key (mKey): 29058 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX95LA138 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/29058/pdf - Page: https://openairdocs.org/ntsb/LAX95LA138 ## Probable cause an engine failure due to oil exhaustion from a missing oil pressure relief valve as the result of an improper maintenance inspection. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(total) - nonmechanical, approach - vfr pattern - downwind - lubricating system,oil regulator - missing (cause) - maintenance,installation - improper, company maintenance personnel (cause) - Forced landing, emergency descent/landing - terrain condition - high vegetation - In flight collision with object, emergency descent/landing - object - tree(s) - terrain condition - none suitable ## Analysis THE PILOT WAS PROCEEDING TO A LANDING AREA AT 400 FEET AGL WHEN HE EXPERIENCED A LOSS OF ENGINE POWER. HE AUTOROTATED INTO DENSE JUNGLE TERRAIN. EXAMINATION OF THE ENGINE REVEALED THAT THE OIL PRESSURE RELIEF VALVE WAS MISSING. THIS WAS THE FIRST FLIGHT SINCE A 100-HOUR INSPECTION WAS MADE THE DAY BEFORE. THE INSPECTION OF THE SAFETY WIRE SECURING THE VALVE IS NOT A PREFLIGHT ITEM FOR THE PILOT, NOR IS IT REQUIRED TO BE INSPECTED PRIOR TO FLIGHT. ## Factual narrative On March 17, 1995, at 1520 hours Guam standard time, a Bell 47 helicopter, N6569H, crashed after a loss of engine power near Harmon Field, Guam. Visual meteorological conditions existed at the time of the local maintenance test flight. The helicopter sustained substantial damage and the two occupants were not injured. The investigation revealed that the engine lost oil pressure shortly after departure from Harmon Field. The pilot made a downwind landing into dense jungle. The tail boom separated from the aircraft during the crash sequence. The aircraft had a 100-hour inspection on March 16, 1995, and this was the first flight since the inspection. A Federal Aviation Administrator (FAA) inspector was on the island at the time on other business. This inspector interviewed the operator and the pilot a few days afterwards. The pilot was flying to an open field area at 400 feet above ground level when he noticed a change in the engine rpm and a loss of engine power. Due to obstacles, a 15 to 20 knot tailwind, and a loss of hydraulic power, the pilot was unable to make the open field and autorotated into the jungle. An examination of the aircraft, after it was removed from the accident site, revealed that the oil pressure relief valve was missing. According to the FAA inspector, the valve vibrated out within a short period of time after takeoff with a corresponding loss of engine oil. The operator told the FAA inspector that the valve was probably loose prior to takeoff. When asked if the valve was a normal preflight item, he stated that it should be at least checked to see if the safety wire securing the valve was broken. The operator does not have a published preflight procedures and/or preflight checklist nor is it a requirement under FAR Part 91 operations. ## Aircraft - Registration: [N6569H](https://openairdocs.org/deregistered/N6569H-2015-08-04), registration cancelled 2015-08-04, S/N 3683, built 1968 (OpenAirDocs) - Reported make and model: BELL 47 - Registry model: [Bell TH-13T](https://openairdocs.org/model/bell-th-13t) (registry code 1180813) (OpenAirDocs) - Registry engine: [Lycoming VO-435 series](https://openairdocs.org/engine/lycoming-vo-435-series) (registry code 41525, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 3683 - Airframe hours: 8132 - Engines: LYCOMING VO-435-A/F 220 horsepower reciprocating - Damage: Substantial damage - Flight: Business, Part 91 - Registered owner: Hansen Helicopters, Inc. - Airworthiness certificate: Standard, Normal - Last inspection: Annual, March 16, 1995, 1 hours before ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 31; commercial; airplane ratings: single-engine land; instrument ratings: helicopter; medical: class 2, valid medical--no waivers/lim.; seat: left; flight hours: 1,045 total, 70 in this make and model, 1,000 as pilot in command ## Weather - Conditions: Visual (VMC), Day - Wind: 60° at 15 knots, gusting 20 - Visibility: 20 statute miles - Lowest ceiling: none - Temperature: 90 °F, dew point 84 °F - Altimeter: 29.00 inHg - Observed at: NGM, 5 nm away ## Other investigations on N6569H (1) 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. - [NTSB LAX96LA111](https://openairdocs.org/ntsb/LAX96LA111), Jan 29, 1996: Bell 47G-2A1 (N6569H), Honiara, Solomon Islands, destroyed, 1 fatal. Probable cause: the pilot and the ship crew's failure to assure the tie down strap was removed prior to liftoff. 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. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.