# NTSB ANC98LA109: Enstrom F-28F, N8622U, Skwentna, AK, July 25, 1998 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: July 25, 1998, 14:00 local (22:00 UTC) - Place: Skwentna, AK - Coordinates: 61.929916, -151.729507 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=61.9299&lon=-151.7295&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report March 30, 2000 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - NTSB case key (mKey): 45644 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC98LA109 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/45644/pdf - Page: https://openairdocs.org/ntsb/ANC98LA109 ## Probable cause A loss of engine power due to a fractured number three cylinder intake manifold flange, and the pilot's inability to maintain the proper rate of descent during the autorotation flare. A contributing factor associated with the accident was the downwind (tailwind) landing condition. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(partial) - mech failure/malf, hover - engine assembly,cylinder - induction air control,intake manifold - fractured (cause) - Hard landing, emergency landing - weather condition - tailwind (contributing factor) - proper descent rate - not possible, pilot in command (cause) - terrain condition - none suitable ## Analysis The certificated commercial helicopter pilot was conducting a salmon survey for the State of Alaska, Department of Fish & Game. This operation required him to hover the helicopter over the stream while the passenger, a wildlife biologist employed by the State of Alaska, noted the number of fish. The pilot stated that while in a hover above the stream, he felt a slight vibration followed by a partial loss of engine power. He said that while hover taxiing the helicopter to a suitable landing area, the engine continued to lose power, and he was forced to make a downwind autorotation. He said that as the helicopter touched down, the main rotor blades flexed downward, and struck the tail boom. The helicopter's tail boom, and tail rotor gearbox sustained substantial damage. The operator reported that during a postaccident inspection of the engine, a fractured intake manifold flange was discovered on the number three cylinder assembly. ## Factual narrative On July 25, 1998, about 1400 Alaska daylight time, a skid equipped Enstrom F-28F helicopter, N8622U, sustained substantial damage during a forced landing about 30 miles south of Skwentna, Alaska. The helicopter is owned by Mark E. Miller, dba Talaheim Lodge and Air Service, of Skwentna. The helicopter was being operated as a visual flight rules (VFR) on-demand air taxi flight under Title 14, CFR Part 135, when the accident occurred. The certificated commercial helicopter pilot, and the one passenger aboard were not injured. Visual meteorological conditions prevailed, and company flight following procedures were in effect. The flight originated about 1330, at the operator's remote fishing lodge located about 5 miles south of the accident site. During a telephone conversation with the National Transportation Safety Board investigator-in-charge, on July 25, the pilot reported that he was conducting a salmon survey for the State of Alaska, Department of Fish & Game. This operation required him to hover the helicopter over the stream while the passenger, a wildlife biologist employed by the State of Alaska, noted the number of fish. The pilot stated that while in a hover above the stream, he felt a slight vibration followed by a partial loss of engine power. He said that while hover taxiing the helicopter to a suitable landing area, the engine continued to lose power, and he was forced to make a downwind autorotation. He said that as the helicopter touched down, the main rotor blades flexed downward, and struck the tail boom. The helicopter's tail boom, and tail rotor gearbox sustained substantial damage. The operator reported that during a postaccident inspection of the engine, a fractured intake manifold flange was discovered on the number three cylinder assembly. ## Aircraft - Registration: [N8622U](https://openairdocs.org/aircraft/N8622U), registered now, S/N 721, built 1982 (OpenAirDocs) - Reported make and model: Enstrom F-28F - Registry model: [Enstrom F-28F](https://openairdocs.org/model/enstrom-f-28f) (registry code 3300412) (OpenAirDocs) - Registry engine: [Lycoming HIO-360 series](https://openairdocs.org/engine/lycoming-hio-360-series) (registry code 41524, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 721 - Airframe hours: 1280 - Engines: Lycoming HIO 360 225 horsepower reciprocating - Damage: Substantial damage - Flight: Part 135 - Registered owner: Mark E. Miller - Airworthiness certificate: Standard, Normal - Last inspection: Annual, February 28, 1998, 74 hours before - Departed: SKW, AK - Flight plan: Company VFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 48; commercial; airplane ratings: single-engine sea, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; flight hours: 11,000 total, 1,200 in this make and model, 11,000 as pilot in command, 200 in the last 90 days, 80 in the last 30 days, 4 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 120° at 10 knots, gusting 15 - Visibility: 7 statute miles - Lowest ceiling: 1,500 ft overcast - Temperature: 55 °F ## 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 19980725017549A](https://openairdocs.org/incident/19980725017549A), Jul 25, 1998: Enstrm F28F, Skwentna, AK, Substantial damage. Crashed en route, anchoragae, AK. (-23) on July 25, 1998, at approximately 1400, Alaska daylight time, an Enstrom F28F, N8622U helicopter landed hard after… ## Other investigations on N8622U (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 SEA84LA021](https://openairdocs.org/ntsb/SEA84LA021), Nov 15, 1983: Enstrom F28F (N8622U), Hillsboro, OR, substantial damage 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.