# NTSB ANC09LA110: Hughes 369A (OH-6A), N501SU, Palmer, AK, September 29, 2009 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: September 28, 2009, 17:00 local (Sep 29, 2009, 01:00 UTC) - Place: Palmer, AK - Coordinates: 61.633335, -149.288604 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=61.6333&lon=-149.2886&mi=10 - Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping) - Defining event: [Takeoff: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report August 12, 2010 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - Parties: Federal Aviation Administration (Airworthiness), Rolls-Royce Corporation - NTSB case key (mKey): 74824 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC09LA110 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/74824/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=74824 - Page: https://openairdocs.org/ntsb/ANC09LA110 ## Probable cause A partial loss of engine power after take off for an undetermined reason, which resulted in a hard landing. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Hughes 369A (OH-6A), 1 case](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=4470506), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md) - [Power plant](https://openairdocs.org/ntsb-findings/01057100): Aircraft › Aircraft power plant · Not specified; cases with it: [Hughes 369A (OH-6A), 1 case](https://openairdocs.org/ntsb-findings/01057100/cases.md?model=4470506), [All aircraft, 198 cases](https://openairdocs.org/ntsb-findings/01057100/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Takeoff: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [Hughes 369A (OH-6A), 1 case](https://openairdocs.org/ntsb-events/342/sequence.md?model=4470506), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) - [Autorotation: Hard landing](https://openairdocs.org/ntsb-events/092); cases with it: [Hughes 369A (OH-6A), 1 case](https://openairdocs.org/ntsb-events/092/sequence.md?model=4470506), [All aircraft, 2,102 cases](https://openairdocs.org/ntsb-events/092/sequence.md) ## Analysis The pilot was departing on a local flight in a turbine-powered helicopter. During the initial climb, about 35 feet above the ground, the engine lost power. The pilot entered an autorotation and attempted to cushion the landing, but the helicopter landed hard and the main rotor blades struck the tail boom, severing it from the helicopter. After the accident the engine continued to run, but at low power, requiring the pilot to close the engine throttle and shutdown the engine. A Federal Aviation Administration (FAA) postaccident examination revealed no preaccident mechanical anomalies with the engine or helicopter. The engine was removed from the helicopter, shipped to an engine service center, and placed in an engine test cell. At the direction of an FAA airworthiness inspector, and assisted by an air safety investigator from the engine manufacturer, the engine produced power that was within the manufacturer's performance standards. ## Factual narrative On September 28, 2009, about 1700 Alaska daylight time, a Hughes 369A [OH-6A] helicopter, N501SU, sustained substantial damage following a loss of engine power and subsequent emergency landing after takeoff from the Wolf Lake Airport, Wasilla, Alaska. The helicopter was being operated as a visual flight rules (VFR) personal flight, under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91, when the accident occurred. The private pilot and one passenger were not injured. Visual meteorological conditions prevailed, and no flight plan was filed. The accident flight originated at the Wolf Lake Airport. During a telephone conversation with the National Transportation Safety Board investigator-in-charge on September 29, the pilot reported that during takeoff, as the helicopter climbed to about 35 feet agl, it suddenly yawed to the right, the red engine out annunciator light illuminated, and the low rotor warning horn sounded. The pilot entered an emergency autorotation and attempted to cushion the landing, but the helicopter landed hard and the main rotor blades struck the tail boom, severing it from the helicopter. The pilot noted that after the accident the engine continued to run, but at a low power setting, requiring him to close the engine throttle and shutdown the engine. The helicopter sustained substantial damage to the tail boom, fuselage, and main rotor system. A witness to the accident reported seeing a puff of white smoke and sparks coming from the helicopter’s engine exhaust just before the helicopter landed. The helicopter was equipped with an Allison [Rolls-Royce] 250-C10D turbine engine. A Federal Aviation Administration (FAA) airworthiness inspector from the Anchorage Flight Standards District Office (FSDO), traveled to the accident airport on October 1, and examined the helicopter at the owner’s hangar. He reported that no preaccident mechanical anomalies were discovered during his examination. The engine was removed from the helicopter and shipped to a Rolls-Royce service center in Oakland, California for examination. On January 12, 2010, under the supervision of an airworthiness inspector from the Oakland FSDO, the engine was examined externally, which revealed no preaccident mechanical anomalies. The engine was then placed in an engine test cell, started, and it produced its full range of rated rpm. An air safety investigator from Rolls-Royce reported that the engine operated at a slightly lower power setting, but still within acceptable Rolls-Royce performance standards. ## Aircraft - Registration: [N501SU](https://openairdocs.org/deregistered/N501SU-2020-06-17), registration cancelled 2020-06-17, S/N 480435, built 1967 (OpenAirDocs) - Reported make and model: HUGHES 369A (OH-6A) - Registry model: [Hughes 369A (OH-6A)](https://openairdocs.org/model/hughes-369a-oh-6a) (registry code 4470506) (OpenAirDocs) - Registry engine: [Allison 250-C10D](https://openairdocs.org/engine/allison-250-c10d) (registry code 03035, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 480435 - Engines: Allison 250-C10D 317 horsepower turbo shaft - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: Compass Rose LLC - Airworthiness certificate: Standard, Normal - Departed: 4AK6, Wasilla, AK - Destination: 4AK6, Wasilla, AK - Airport: 4AK6, Wolf Lake Airport, runway 06, 3,800 × 70 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 52; injuries: none; private; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 3, without waivers/limitations; seat: left; flight hours: 2,499 total, 105 in this make and model, 10 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 45 °F, dew point 34 °F - Altimeter: 29.97 inHg - Observed at: PAAQ, 6 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). - [Accident 20090928049869A](https://openairdocs.org/incident/20090928049869A), Sep 28, 2009: Hughes 369A (OH-6A, Wasilla, AK, Substantial damage. The pilot and owner of the helicopter told investigators that during climb from a hover the aircraft experienced a sudden loss of power at approximately 25… ## Docket (1 files) The files NTSB released with the investigation on July 7, 2010, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=74824. 453 KB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 453 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40332566&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF 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.