# NTSB SEA94LA171: Robinson R-22M, N42WC, Portland, OR, July 7, 1994 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: July 7, 1994, 11:25 local (18:25 UTC) - Place: Portland, OR - Coordinates: 45.400089, -122.789215 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=45.4001&lon=-122.7892&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report December 2, 1994 - Report: Approved by Office Director - NTSB case key (mKey): 41968 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA94LA171 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/41968/pdf - Page: https://openairdocs.org/ntsb/SEA94LA171 ## Probable cause TAIL ROTOR GEARBOX FAILURE DUE TO INADEQUATE ASSEMBLY AND INSPECTION PROCEDURES BY THE MANUFACTURER. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of control - in flight, maneuvering - rotor drive system,tail rotor gearbox(90 deg) - failure,total (cause) - acft/equip,inadequate aircraft component, manufacturer (cause) - Forced landing, descent - emergency - On ground/water encounter with terrain/water, landing ## Analysis THE PILOT ATTEMPTED AN AUTOROTATION AFTER LOSS OF TAIL ROTOR EFFECTIVENESS. THE TAIL BOOM AND ROTOR STRUCK THE SURFACE WHEN THE FLOAT EQUIPPED HELICOPTER LANDED IN THE RIVER. INVESTIGATION REVEALED THAT THE TAIL ROTOR GEARBOX OUTPUT SHAFT PINION RETAINING KEY HAD NOT BEEN INSTALLED DURING ASSEMBLY. THE TAIL ROTOR HUB AND BLADE ASSEMBLY WERE FREE TO TURN ON THE SHAFT AT THE TIME OF INVESTIGATION. ## Factual narrative On July 7, 1994, at 1125 Pacific daylight time, a Robinson R-22M, N42WC, sustained substantial damage during an autorotational forced landing to Ross Island beach, Portland, Oregon. The student pilot and certified flight instructor sustained minor injuries. No flight plan was filed for the instructional flight, which had departed Hillsboro, Oregon about 1105. The pilot stated that he had lost tail rotor effectivness and attempted an autorototation from about 75 feet AGL. The pilot stated that the aircraft continued turning through two or three rotations before toching down. The aircraft landed near shoreline, with the tail rotor and boom striking the water. Inspection revealed that the tail rotor gearbox (P/N A021-1) output shaft pinion (A545-1) retaining key (A114-2) was not installed at the time of factory assembly, allowing the tail rotor hub and blade to become disengaged. ## Aircraft - Registration: [N42WC](https://openairdocs.org/aircraft/N42WC), registered now, S/N 1531M, built 1990 (OpenAirDocs) - Reported make and model: ROBINSON R-22M - Registry model: [Robinson Helicopter R22 MARINER](https://openairdocs.org/model/robinson-helicopter-r22-mariner) (registry code 7640115) (OpenAirDocs) - Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 1531M - Airframe hours: 460 - Engines: LYCOMING O-320-B2C 131 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Operator: Hillsboro Helicopters, Inc. - Registered owner: West Coast Building Fasteners - Airworthiness certificate: Standard, Normal - Last inspection: Annual, January 28, 1994, 22 hours before - Departed: HIO, HILLSBORO, OR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 38; private, flight instructor, commercial; airplane ratings: single-engine land; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 1,822 total, 1,475 in this make and model, 257 in the last 90 days, 101 in the last 30 days, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 330° at 8 knots - Visibility: 30 statute miles - Lowest ceiling: none - Temperature: 81 °F, dew point 57 °F - Altimeter: 30.00 inHg - Observed at: HIO ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 19940707017769A](https://openairdocs.org/incident/19940707017769A), Jul 7, 1994: Robsin R22MARINER, Portland, OR, Substantial damage. Lost tail rotor effectivness. Autorotated to a beach. Tail rotor shaft disconnected. Key not installed at factory. ## Other investigations on N42WC (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 ERA22LA340](https://openairdocs.org/ntsb/ERA22LA340), Jul 27, 2022: Robinson Helicopter R22 Mariner (N42WC), Hollywood, FL, substantial damage. Probable cause: Inadequate maintenance of the helicopter’s tail rotor blades, which resulted in a failure of the tail rotor drive system, and an inflight loss of yaw control from which the flight instructor was… 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.