# NTSB SEA01TA143: Boeing Helicopters Div. H500D, N8964T, Union Gap, WA, July 24, 2001 - Type: NTSB accident investigation - Classification: Accident · No injuries · Final report - Date: July 24, 2001, 16:00 local (23:00 UTC) - Place: Union Gap, WA - Coordinates: 46.71902, -120.410049 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=46.7190&lon=-120.4100&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 3, 2002 - Report: Approved by Office Director - Parties: FAA FSDO, U.S. Department of Justice - NTSB case key (mKey): 52819 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA01TA143 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/52819/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=52819 - Page: https://openairdocs.org/ntsb/SEA01TA143 ## Probable cause The complete loss of engine power at cruise for undetermined reasons. Factors include a landing area that was restricted/confined due to adjacent trees, and an intentional abrupt flare resulting in a hard landing. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power, cruise - reason for occurrence undetermined (cause) - weather condition - turbulence - Forced landing, descent - emergency - Hard landing, emergency descent/landing - flare - abrupt, pilot in command (contributing factor) - airport facilities,runway/landing area condition - congested/confined area (contributing factor) - object - tree(s) (contributing factor) ## Analysis While cruising at 1,000 feet above the ground, the helicopter encountered an area of strong updrafts and downdrafts. As it passed through one particularly strong downdraft, the aircraft experienced a complete loss of power. The pilot then initiated an autorotation to the only available landing area. Because the area was small and surrounded by trees, the pilot found it necessary to execute an abrupt flare in order to arrest the forward movement of the helicopter prior to colliding with the trees ahead. The abrupt flare resulted in a hard landing, and the main rotor blades flexed downward far enough to sever the tail boom. Post-accident inspections of the engine and aircraft systems did not reveal any malfunctions or anomalies that would have been expected to contribute to a loss of power. Although the flight manual warned of possible fuel starvation associated with large side slip angles of uncoordinated flight with less than 35 pounds of fuel remaining, approximately 115 pounds of fuel were drained from the helicopter's main fuel bladder. ## Factual narrative On July 24, 2001, approximately 1600 Pacific daylight time, the tail boom of a Boeing H500D helicopter, N8964T, separated during a power-out autorotational landing about three miles south of Union Gap, Washington. The pilot and his two passengers were not injured, but the aircraft, which is owned and operated by Omega Air, sustained substantial damage. The local Public Use flight, which departed Yakima Air Terminal about 1320, was being operated in visual meteorological conditions. No flight plan had been filed. There was no report of an ELT activation. According to the pilot, as he passed through Union Gap while returning to Yakima at 1,000 feet above ground level (AGL), at an indicated airspeed of 80 knots, the aircraft encountered a series of strong updrafts and downdrafts. As it flew through one particularly strong downdraft, the helicopter pitched nose down and the engine stopped producing power. Because he was crossing the Yakima River at the time of the occurrence, the pilot immediately initiated an autorotational descent to an island in the middle of the river channel. The only landing area available was small and tightly ringed by trees. During the power-off landing, after clearing the trees and entering the landing area, the pilot found it necessary to flare abruptly in order to arrest the forward movement of the aircraft prior to impacting the trees ahead. As a result of the abrupt flare, the helicopter touched down hard, and the main rotor blades flexed downward to an extent that allowed them to sever the tail boom. Post accident inspections of the airframe, engine, and aircraft systems did not reveal any malfunctions or anomalies that would have been expected to contribute to a loss of engine power. Although the 500D flight manual warns that fuel starvation can occur if large slip angles and uncoordinated maneuvers are performed with less than 35 pounds of fuel remaining, after the accident, approximately 15 gallons of fuel was drained from the main fuel tank of the aircraft. ## Aircraft - Registration: [N8964T](https://openairdocs.org/deregistered/N8964T-2019-05-07), registration cancelled 2019-05-07, S/N 811038D (OpenAirDocs) - Reported make and model: Boeing Helicopters Div. H500D - Registry model: [Hughes Helicopters HUGHES 369D](https://openairdocs.org/model/hughes-helicopters-hughes-369d) (registry code 4470706) (OpenAirDocs) - Category: Helicopter - Serial number: 1038D - Airframe hours: 3369 - Engines: Allison 250C20B 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Public aircraft, Public use - Registered owner: Omega Air - Airworthiness certificate: Standard, Normal - Last inspection: Annual, June 15, 2001, 39 hours before - Departed: YKM, Yakima Air Term, WA ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 52; injuries: none; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: helicopter, airplane; medical: class 1, valid medical--w/ waivers/lim; last flight review May 7, 2001; seat: left; flight hours: 6,199 total, 1,045 in this make and model, 5,742 as pilot in command, 152 in the last 90 days, 87 in the last 30 days, 10 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Visibility: 20 statute miles - Lowest ceiling: none - Temperature: 95 °F, dew point 64 °F - Altimeter: 29.89 inHg ## 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 20010724022399A](https://openairdocs.org/incident/20010724022399A), Jul 24, 2001: Hughes 369D, Yakima, WA, No damage. (-23) Public use, dea government owned aircraft. The pilot was returning to ykm for fuel when he lost power and auto-rotated into a hard landing chopping off… ## Docket (1 files) The files NTSB released with the investigation on May 10, 2002, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=52819. 322 KB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 322 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40387780&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.