# NTSB LAX08LA195: Arrow Falcon Exporters OH-58C, N912HP, Fresno, CA, June 23, 2008 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: June 23, 2008, 07:00 local (14:00 UTC) - Place: Fresno, CA - Coordinates: 36.776111, -119.718055 - Nearby events: https://openairdocs.org/map.md?lat=36.7761&lon=-119.7181&mi=10 - Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping) - Defining event: [Takeoff: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report January 29, 2009 - Report: Approved by Office Director - Parties: Rolls Royce, Federal Aviation Administration - NTSB case key (mKey): 68316 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX08LA195 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/68316/pdf - Page: https://openairdocs.org/ntsb/LAX08LA195 ## Probable cause The loss of engine power due to fatigue failure of a second stage compressor blade. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine (turbine/turboprop): compressor section](https://openairdocs.org/ntsb-findings/01057230): Aircraft › Aircraft power plant · Fatigue/wear/corrosion (probable cause); cases with it: [All aircraft, 53 cases](https://openairdocs.org/ntsb-findings/01057230/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Takeoff: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) (defining event); cases with it: [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) - [Takeoff: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341); cases with it: [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Emergency descent: Landing area undershoot](https://openairdocs.org/ntsb-events/370); cases with it: [All aircraft, 201 cases](https://openairdocs.org/ntsb-events/370/sequence.md) ## Analysis The pilot reported that he had filled the spray tanks with water and had lifted off from a platform on the back of a truck when he heard three loud noises followed by a loss of engine power. The pilot initiated a hovering autorotation to the landing platform; however, was only able to maneuver the forward portion of the helicopter over the platform. Subsequently, the helicopter slid off the platform and impacted the ground tail boom first, resulting in structural damage to the tail boom and fuselage. Examination of the engine revealed that 15 third stage compressor vanes were fractured near the root and had separated. The majority of the separated vanes were located in the lower compressor case half. The remaining attached vanes were bent over in the direction of engine rotation. A single second stage compressor vane located in the lower case halve was fractured near the root and had liberated. Multiple third and fourth stage compressor blades had leading edge damage. One second stage vane airfoil was separated and the area of separation was found consistent with high cycle fatigue (HCF). An additional second stage vane airfoil exhibited a crack, consistent with HCF near the root, but it did not separate. A Semi-quantitative x-ray energy dispersive analysis (XEDA) revealed deposits at the suction side vane root were consistent with oxidized braze alloy, indicating the braze alloy was exposed during engine operation. It was also found that the chemistry, microstructure and hardness of the second stage vanes were consistent with component specifications. ## Factual narrative On June 23, 2008, about 0700 Pacific daylight time, an Arrow Falcon Exporters, Inc., OH-58C helicopter, N912HP, was substantially damaged during an emergency landing following a reported loss off engine power while hovering west of Fresno, California. The helicopter was registered to Del Rio Aviation, Inc., Paso Robles, California, and operated by Double Tree Helicopters, Turlock, California, under the provisions of 14 Code of Federal Regulations Part 137. The commercial pilot, sole occupant of the helicopter, was not injured. Visual meteorological conditions prevailed, and no flight plan had been filed for the local aerial application flight that was originating at the time of the accident. The pilot reported that he had filled the spray tanks with water and had lifted off from the back of a truck platform when he heard three loud noises followed by a loss of engine power. The pilot initiated a hovering autorotation to the landing platform, however, was only able to maneuver the forward portion of the helicopter over the platform. Subsequently, the helicopter slid off the platform and impacted the ground tail boom first, resulting in structural damage to the tail boom and fuselage. On June 23, 2008, the Allison T63-A720 engine was examined by a representative from Rolls Royce under the supervision of a Federal Aviation Administration (FAA) inspector. The examination revealed that all fuel, lube and pneumatic lines, "B" nuts and their associated fittings were secure. Several black "carbon-like" particles lay loose in the base of the exhaust collector. Inspection of the inlet plenum chamber did not reveal any evidence of foreign material or missing hardware. Inspection of the compressor inlet revealed dirt deposits on the inlet guide vanes as well as a small ferrous type material adjacent to the inlet guide vane at the six o'clock position. A single first stage compressor blade contained a small nick to the leading edge of the blade near the tip. The engine was then removed from the airframe and the compressor was partially disassembled. The compressor module was removed from the accessory gearbox and the compressor case halves were removed for further inspection. Inspection revealed that 15 third stage compressor vanes were fractured near the root and were separated. The majority of the separated vanes were located in the lower compressor case halve. The remaining attached vanes were bent over in the direction of engine rotation. One second stage compressor vane located in the lower case halve was fractured near the root and was separated. Multiple third stage and fourth stage compressor blades were damaged at the leading edge. Compressor case lining material was missing from both compressor case halves. During removal and disassembly of the compressor, oil was evident at the number one bearing supply and scavenge fittings. The compressor bleed valve was dirty but moved freely from full open to full close. No radial play of the poppet valve wasnoted. The outer combustion case and combustion liner were removed. The fuel nozzle inlet screen was clean. Visual inspection of the first stage nozzle shield and first stage nozzle vane exhibited metal spray fused to the surface of the pressure side. The compressor was sent to the facilities of Rolls Royce for further metallurgical examination under the supervision of an FAA inspector. The examination of the compressor section revealed that the compressor case lining material was partially missing and eroded from both compressor case halves with the highest level of erosion on the top half, downstream of the first stage vane band. One second stage vane airfoil was separated. The area of separation was found consistent with high cycle fatigue (HCF). An additional second stage vane airfoil exhibited a crack, consistent with HCF near the root, but did not separate. A semi-quantitative x-ray energy dispersive analysis (XEDA) revealed deposits at the suction side vane root were consistent with oxidized braze alloy, indicating the braze alloy was exposed during engine operation. It was also found that the chemistry, microstructure and hardness of the second stage vanes were consistent with properly processed AMS 5604 (17-4 PH steel). ## Aircraft - Registration: N912HP (not matched to a registry record) - Reported make and model: Arrow Falcon Exporters, Inc. OH-58C - Category: Helicopter - Serial number: 71-20679 - Airframe hours: 5047.3 - Engines: Allison T63-A720 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Double Tree Helicopters - Registered owner: Del Rio Aviation - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, January 17, 2008, 20.5 hours before - Departed: Fresno, CA ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 29; injuries: none; commercial; airplane ratings: single-engine land; medical: class 2, without waivers/limitations; last flight review February 18, 2008; seat: right; flight hours: 1,823 total, 1,606 in this make and model, 1,823 as pilot in command, 121 in the last 90 days, 31 in the last 30 days, 6 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 280° at 3 knots - Visibility: 5 statute miles - Lowest ceiling: none - Temperature: 79 °F, dew point 36 °F - Altimeter: 29.95 inHg - Observed at: KFAT ## 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 20080623857679A](https://openairdocs.org/incident/20080623857679A), Jun 23, 2008: Arrowf OH58C, Firebaugh, CA, No damage. During agricultual operations N912HP was attempting to land on the service trailer with fresh water in the hopper tanks for cleaning. A pop was heard from the… 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.