# NTSB WPR09LA048: Hughes 369HS, N9154F, Fillmore, UT, November 25, 2008 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: November 25, 2008, 12:45 local (19:45 UTC) - Place: Fillmore, UT - Coordinates: 38.958057, -112.363052 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=38.9581&lon=-112.3631&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report June 11, 2009 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Rolls-Royce, Boeing, Federal Aviation Administration - NTSB case key (mKey): 69505 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR09LA048 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/69505/pdf - Page: https://openairdocs.org/ntsb/WPR09LA048 ## Probable cause The loss of engine power due to fuel starvation as a result of a loose fuel filter upper drain cap, which was not properly secured by maintenance personnel. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Maintenance](https://openairdocs.org/ntsb-findings/02062000): Personnel issues › Task performance · Maintenance personnel (probable cause) - [Fuel system: fuel filter-strainer](https://openairdocs.org/ntsb-findings/01022821): Aircraft › Aircraft systems · Incorrect service/maintenance (probable cause) - [Terrain: mountainous/hilly terrain](https://openairdocs.org/ntsb-findings/03021010): Environmental issues › Physical environment · Contributed to outcome ## Analysis According to the pilot, during cruise flight the helicopter's engine lost power and it entered an autorotation. The helicopter was over mountainous/hilly terrain and there was no open place to land. The pilot selected a spot on a steep hill covered with 20- to 30-foot-tall oak trees. Upon touchdown, the helicopter began to roll, but was stopped by the vegetation. The tailboom incurred structural damage during the landing. Postaccident examination of the helicopter revealed that the fuel pump filter bowl's upper drain plug had been replaced with a non-standard threaded nipple fitting and cap. This cap was found with zero torque (loose) and partially backed off of its seat. Less than two threads retained the cap on its fitting. In standard configuration, the upper and lower drain plugs are lock-wired to each other, thus ensuring both fittings remain properly torqued. On the accident engine, the lower drain plug was lock-wired to the upper drain's threaded nipple fitting. However, the cap was not lockwired. The fuel spray nozzle's fuel supply line was found to be devoid of any residual fuel. (This line would typically have about 1 to 1.5 teaspoons of fuel following a normal engine shutdown.) The engine was removed from the airframe and shipped to the facilities of the engine manufacturer for a test run. The suspect loose cap was gently tightened with a wrench. The engine was then run and met all test cell parameters for new engine production. Since the fuel pump filter bowl operates at a negative pressure during operation, a compromise at this point in the fuel system would not result in a fuel leak, but would rather result in an air induction into the fuel system, interrupting the supply of fuel to the fuel spray nozzle. ## Factual narrative On November 25, 2008, about 1245 mountain standard time, a Hughes 369HS helicopter, N9154F, sustained substantial damage during a forced landing following a loss of engine power in cruise flight near Fillmore, Utah. The commercial pilot, the sole occupant, was not injured. Skyhawk Helicopter Service, Inc., Spanish Fork, Utah, was the registered owner and operator of the helicopter. Visual meteorological conditions prevailed, and no flight plan was filed for the cross-country flight conducted under 14 Code of Federal Regulations Part 91. The helicopter departed Richfield, Utah, about 1230, and was en route to Spanish Fork. According to the pilot, during cruise flight, the engine started to surge, then lost power, and within seconds regained power. The engine again started to surge and lost power. The pilot entered an autorotation. The helicopter was over mountainous/hilly terrain and there was no open place to land. The pilot selected a spot on a steep hill covered with 20- to 30-foot-tall oak trees. Upon touchdown, the helicopter began to roll, but was stopped by the vegetation. The tailboom incurred structural damage during the landing. A post-accident examination of the helicopter was conducted under the supervision of a Federal Aviation Administration (FAA) inspector by representatives from the airframe and engine manufacturers. During this examination, it was noted that the fuel pump filter bowl's upper drain plug had been replaced with a non-standard fitting and cap. This cap was found with zero torque (loose) and partially backed off its seat. Less than two threads retained the cap on its fitting. According to the pump manufacturer's (Sundstrand Corporation) Overhaul and Maintenance Manual (IPL Appendix C, pgs 4-5), both the upper and lower drain ports on the fuel pump filter bowl should be sealed with identical AN814-4DL plugs and MS29512-04 O-rings. On the subject engine, the upper drain plug had been replaced with a threaded nipple fitting with a threaded cap. The loose cap and its respective fitting had broken torque paint that was white in color and appeared weathered and dirty. Other fittings on the engine had torque paint that was blue or orange and was clean and bright in color. In standard configuration, the upper and lower drain plugs are lock-wired to each other, thus ensuring both fittings remain properly torqued. On the accident engine, the lower drain plug was lock-wired to the upper drain's threaded nipple fitting. However, the cap on this fitting was not lockwired. It was this cap that was found loose. The fuel spray nozzle's fuel supply line was disconnected to measure the amount of fuel remaining. The line was found to be devoid of any residual fuel. (This line would typically have about 1 to 1.5 teaspoons of fuel following a normal engine shutdown.) No preimpact discrepancies, other than the loose cap, were noted to the airframe or engine. The engine was removed from the airframe and shipped to the facilities of theengine manufacturer in Indianapolis, Indiana, for a test run. On January 15, 2009, FAA and Rolls-Royce representatives gathered at the Rolls-Royce facility in Indianapolis to test run the subject engine. Since the test cell uses a positive-pressure fuel system (unlike the helicopter's fuel system), the suspect loose cap was gently tightened with a wrench in order to prevent a fuel leak inside the test cell. The engine was then run in the test cell and met all test cell parameters for new engine production. According to Rolls-Royce personnel, since the fuel pump filter bowl operates at a negative pressure during operation, a compromise at this point in the fuel system would not result in a fuel leak, but would rather result in an air induction into the fuel system. Induction of air into the fuel system interupts fuel to the fuel spray nozzle. The lack of fuel in the fuel supply line to the fuel spray nozzle is consistent with fuel starvation. ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Prior to flight: Aircraft maintenance event](https://openairdocs.org/ntsb-events/040) - [Enroute-cruise: Fuel starvation](https://openairdocs.org/ntsb-events/191) - [Enroute-cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event) - [Autorotation: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470) ## Aircraft - Registration: N9154F (not matched to a registry record) - Reported make and model: HUGHES 369HS - Category: Helicopter - Serial number: 930517S - Airframe hours: 21496 - Engines: ALLISON 250 SER 400HP 400 horsepower turbo shaft - Damage: Substantial damage - Flight: Business, Part 91 - Operator: Skyhawk Helicopter Service, Inc. - Registered owner: Skyhawk Helicopter Service, Inc. - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, November 18, 2008, 34 hours before - Departed: RIF, Richfield, UT - Destination: U77, Spanish Fork, UT ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 33; injuries: none; commercial, flight instructor; airplane ratings: single-engine land; medical: class 2, without waivers/limitations; last flight review June 30, 2008; seat: left; flight hours: 5,749 total, 895 in this make and model, 5,619 as pilot in command, 70 in the last 90 days, 43 in the last 30 days, 4 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 210° at 10 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 61 °F, dew point 21 °F - Altimeter: 30.00 inHg - Observed at: MLF, 45 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 20081125852239A](https://openairdocs.org/incident/20081125852239A), Nov 25, 2008: Hughes 369HS, Fillmore, UT, Substantial damage. (-23) While in cruise flight the aircraft experienced a loss of power and subsequent flameout of the engine. Pilot initiated an auto rotation into a canyon.… 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.