# NTSB ANC97IA035: Piper PA-31-350, N3542H, Kotzebue, AK, March 15, 1997 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: March 15, 1997, 19:57 local (23:57 UTC) - Place: Kotzebue, AK - Coordinates: 67.239646, -161.190124 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=67.2396&lon=-161.1901&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 3 uninjured - Status: Completed, report June 26, 1998 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - Safety recommendations: Yes - ADs cited in the narratives: [AD 80-25-05](https://openairdocs.org/ad/80-25-05) (OpenAirDocs) - NTSB case key (mKey): 2946 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC97IA035 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/2946/pdf - Page: https://openairdocs.org/ntsb/ANC97IA035 ## Probable cause the jammed main landing gear which was caused by a binding main landing gear door with a broken hinge. The fractured, inadequate main landing gear door hinge was also causal. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, cruise - door,landing gear - binding(mechanical) (cause) - landing gear,main gear - jammed (cause) - acft/equip,inadequate aircraft component, manufacturer (cause) - Wheels up landing, landing - wheels up landing - intentional, pilot in command ## Analysis The airplane was landed with the landing gear retracted because the pilot was unable to lower the left main landing gear, although the nose gear and the right main landing gear would extend and lock properly. Postaccident inspection disclosed a fractured left main landing gear door hinge. The door hinge was the new, improved, version of an older hinge which had a history of cracking in the radius of the hinge. The hinge on the incident airplane was a replacement hinge mandated by an airworthiness directive. The replacement hinge also fractured in the radius. A review of Service Difficulty Reports disclosed at least eight other instances of cracks in the new hinge. ## Factual narrative On March 15, 1997, about 1957 Alaska Standard Time, a wheel equipped Piper PA-31-350 airplane, N3542H, received minor damage during a gear up landing at the Ralph Wien Memorial Airport, Kotzebue, Alaska. The airline transport certificated pilot and two passengers aboard reported no injuries. The 14 CFR Part 135 scheduled commuter flight was operated by Cape Smythe Air Service as Flight 270. The airplane last departed Kivalina, Alaska, about 1822, and operated in visual meteorological conditions. A VFR flight plan was filed. According to company personnel, the pilot reported he encountered turbulence while en route from Kivalina. Shortly after the turbulence encounter, the pilot said the main landing gear unsafe light illuminated. He recycled the gear (lowered and retracted), but the light remained illuminated. A subsequent low pass at Kotzebue allowed confirmation from personnel on the ground that the left main landing gear was not completely retracted, and that it would not move from the wheel well when the landing gear handle was selected down. The nose gear and the right main landing gear would extend properly to the down position. The pilot elected to make a gear up landing on the snow and ice covered runway. Postlanding inspection of the left main landing gear disclosed a broken, inboard main gear door hinge. According to company maintenance personnel, the broken hinge occurred prior to the landing, and kept the left main gear from extending. The left, inboard main landing gear door hinge, Piper ID number 46652-2, was sent to the NTSB metallurgical laboratory in Washington, D.C., for inspection. The metallurgist who inspected the hinge noted the hinge material met the manufacturing specifications for composition, hardness, and dimensions. He discovered a fatigue crack which emanated from multiple origins at the tip of a forging flash adjacent to the inside radius of the hinge (see attached metallurgical report). The metallurgical report says, in part: "Most of the fatigue crack region exhibited mud crack features and scale which is characteristic of a severely oxidized surface of aluminum alloy." Piper Service Bulletin (SB) 982, dated July 24, 1980, and Airworthiness Directive (AD)80-25-05, addresses cracking of the main landing gear door hinge. The SB notes three types of hinge assemblies are made for the Piper PA-31 airplane. One type is the hinge mentioned above. The other two hinges are made from 0.25 inch thick aluminum plates or steel. The SB requires inspections of the curved portion of the hinge for cracking at the next 100 hours of operation, or the next scheduled inspection, whichever occurs first, and every 100 hours thereafter, unless/until an acceptable replacement part is installed. No inspection is required for a steel door hinge assembly. A door hinge that has a crack, is to be replaced with the newer, thicker, version (0.44 inch) door hinge, Piper Part number 46652-2. The incident airplane had been retrofitted with the new, thicker, version of the door hinge. This hinge failed in the same curved portion as was noted in the older, thinner version of the hinges, and which was the subject of the above SB/AD. Maintenance information supplied by the Operator disclosed the new type landing gear door hinge was installed on the incident airplane in 1988. The airplane had operated approximately 9,938 hours with the new hinge until the hinge failed. A review of Service Difficulty Reports from 1980 through February 1998, disclosed eight instances of cracking or failures of the new, thicker, hinge, which had been installed to resolve cracking problems with the old version of the hinge. ## Aircraft - Registration: [N3542H](https://openairdocs.org/deregistered/N3542H-2001-09-19), registration cancelled 2001-09-19, S/N 31-7952233 (OpenAirDocs) - Reported make and model: Piper PA-31-350 - Registry model: [Piper PA-31-350](https://openairdocs.org/model/piper-pa-31-350) (registry code 7103110) (OpenAirDocs) - Category: Airplane - Serial number: 31-7952233 - Airframe hours: 13988 - Engines: Lycoming TIO-540-J2BD 350 horsepower reciprocating - Damage: Minor damage - Flight: Part 135 - Registered owner: Cape Smythe Air - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, January 31, 1997, 81 hours before - Departed: IAN, KIANA, AK - Destination: OTZ - Flight plan: VFR - Airport: PAOT, Ralph Wien Memorial, runway 35, 3,896 × 50 ft, gravel ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 32; airline transport, flight instructor; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 7,900 total, 700 in this make and model, 7,750 as pilot in command, 270 in the last 90 days, 100 in the last 30 days, 8 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 310° at 14 knots - Visibility: 35 statute miles - Lowest ceiling: none - Temperature: 14 °F, dew point 5 °F - Altimeter: 30.00 inHg - Observed at: OTZ ## Other investigations on N3542H (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 ANC99LA014](https://openairdocs.org/ntsb/ANC99LA014), Dec 3, 1998: Piper PA-31 (N3542H), Point Lay, AK, substantial damage. Probable cause: Failure of the pilot to maintain a proper glidepath. Factors associated with this accident were the airport not having a VASI system installed, and the lack of visual perception for the pilot. 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.