Additional Participating Entities:
Federal Aviation Administration / Flight Standards District Office; Sacramento, California
Honeywell Aerospace; Phoenix, Arizona
Aviation Accident Factual Report - National Transportation Safety Board: https://app.ntsb.gov/pdf
Investigation Docket - National Transportation Safety Board: https://dms.ntsb.gov/pubdms
http://registry.faa.gov/N486SA
Location: Maxwell, CA
Accident Number: WPR16LA104
Date & Time: 05/06/2016, 1700 PDT
Registration: N486SA
Aircraft: BELL UH 1B
Aircraft Damage: Substantial
Defining Event: Loss of engine power (partial)
Injuries: 1 None
Flight Conducted Under: Part 137: Agricultural
On May 6, 2016, about 1700 Pacific daylight time, a Bell UH-1B helicopter, N486SA, was substantially damaged during a forced landing following a loss of main rotor RPM near Maxwell, California. The commercial pilot was not injured. The helicopter was privately owned and operated by Jones Flying Service, Biggs, California, as a Title 14 Code of Federal Regulations Part 137 agricultural flight. Visual meteorological conditions prevailed, and no flight plan was filed. The flight was originating at the time of the accident.
The pilot reported that after loading 300 gallons of chemical, he conducted a pre-takeoff checklist, noting that all instruments displayed normal indications. A takeoff was initiated from the loading truck platform, and as it climbed over the tree canopy, the rotor and engine RPM began to rapidly decay. The pilot initiated a right turn to gain airspeed and recover the rotor RPM, however, the attempt was unsuccessful and he initiated a landing within an almond orchard. The helicopter landed hard and came to rest upright.
The pilot further reported that at the time of the accident, the helicopter weighed 7,854 pounds, which was 1,646 pounds under its maximum gross weight of 9,500 pounds.
Postaccident examination of the helicopter by a Federal Aviation Administration (FAA) inspector revealed that the fuselage and tailboom were substantially damaged.
Following a visual examination of the engine, it was mounted on a test stand and run for approximately 30 minutes. During the engine run, the engine was advanced to 75% of normal rated power followed by an acceleration to the maximum exhaust gas temperature (EGT) limit of 1,140° F. The engine was unable to reach full rated power before the temperature limit was reached.
Inspection of the engine revealed that hot air was being discharged from the engine air inlet anti-ice overboard/vent port. Energizing and de-energizing of the hot air valve solenoid, which supplies compressor discharge air to the engine inlet for de-icing, had no effect on the engine operation or monitored parameters. The engine was shut down and a pressure gauge was added to the engine air inlet anti-ice overboard/vent port to confirm that pressurized air was escaping from this port. The engine was restarted and accelerated to the same performance levels as before. The pressure gauge confirmed that pressurized air was escaping from the anti-ice overboard/vent even though the valve was being commanded closed. Further examination of the engine revealed that when cycling on and off the hot air valve solenoid, a clicking noise could be heard, and when felt by hand during the operation, a slight vibration was detected. The hot air valve and solenoid were removed and found in a partially open position. The engine's bleed air port, where the hot air valve was removed, was blocked using a blanking plate and the engine was run. During the run, it was noted that the engine obtained full rated power prior to reaching the EGT limitations. A representative from the Honeywell manufacture stated that initially the engine was producing approximately 80% of its rated power prior to removal of the hot air valve.
Disassembly of the hot air valve revealed that the main body of the valve appeared to be undamaged. The forward surface of the valve appeared to have deposits/corrosion present, and the solenoid body appeared to be discolored with most of the protective plating missing from the unit. Debris, similar to adhesive/sealant, was found within the valve after disassembly of two body halves. The top surface of the piston, as well as the retaining nut displayed evidence of a buildup of foreign material, consistent with corrosion. The edges of the piston also displayed evidence of corrosion.
The valve's pistons shaft displayed evidence of corrosion and wear. The valve's spring and piston cavity displayed evidence of corrosion. The inside piston to cavity surface displayed evidence of corrosion and linear scoring. A buildup of debris and corrosion were displayed on the surface of the piston shaft guide bore. A microscopic examination of the hot air valve revealed that little to no molybdenum-disulfide coating was present on the flow surfaces of the valve in the areas where sliding contact is made.
According to a Honeywell representative, during manufacture of the hot air valve, a dry film lubricant coating is applied to the flow surfaces of the valve. Once applied, the thickness of the coating is between 0.00015 to 0.0005 inch. Molybdenum-disulfide is a constituent of the dry film lubricant which reduces friction between the sliding elements allowing for smooth, unimpeded motion of the valve. The representative further stated that the lack of lubricant coating in these areas would increase the sliding friction such that the closing spring would be unable to overcome the friction forces thus causing the valve to remain open even when commanded closed.
It could not be determined when the hot air valve had become stuck in the open position.
Per the T5311 Overhaul Manual (75-10-1), an inspection of the hot air valve should occur with an overhaul of the engine.
Review of the engine logbooks revealed that the engine was overhauled on December 29, 2006. No logbook entries pertaining to the inspection of the hot air valve were observed. At the time of the accident, the engine had accumulated a total of 598.2 hours since overhaul.
Pilot Information
Certificate: Commercial
Age: 42, Male
Airplane Rating(s): None
Seat Occupied: Right
Other Aircraft Rating(s): Helicopter
Restraint Used: 4-point
Instrument Rating(s): Helicopter
Second Pilot Present: No
Instructor Rating(s): Helicopter
Toxicology Performed: No
Medical Certification: Class 2 Without Waivers/Limitations
Last FAA Medical Exam: 04/15/2016
Occupational Pilot: Yes
Last Flight Review or Equivalent:
Flight Time: 1906 hours (Total, all aircraft), 213 hours (Total, this make and model), 1829.3 hours (Pilot In Command, all aircraft), 203 hours (Last 90 days, all aircraft), 44.3 hours (Last 30 days, all aircraft)
Aircraft and Owner/Operator Information
Aircraft Make: BELL
Registration: N486SA
Model/Series: UH 1B NO SERIES
Aircraft Category: Helicopter
Year of Manufacture: 1962
Amateur Built: No
Airworthiness Certificate: Restricted
Serial Number: 62-4583
Landing Gear Type: Skid;
Seats:
Date/Type of Last Inspection: 07/15/2015, Annual
Certified Max Gross Wt.: 9500 lbs
Time Since Last Inspection: 106 Hours
Engines: 1 Turbo Shaft
Airframe Total Time: 9132 Hours at time of accident
Engine Manufacturer: LYCOMING
ELT:
Engine Model/Series: T-53-11B
Registered Owner: SPYRES PETER J
Rated Power: 1150 hp
Operator: Jones Flying Service
Operating Certificate(s) Held: Agricultural Aircraft (137)
Meteorological Information and Flight Plan
Conditions at Accident Site: Visual Conditions
Condition of Light: Day
Observation Facility, Elevation: KMYV, 62 ft msl
Distance from Accident Site: 34 Nautical Miles
Observation Time: 2353 UTC
Direction from Accident Site: 110°
Lowest Cloud Condition: Few / 3000 ft agl
Visibility: 10 Miles
Lowest Ceiling: Broken / 5000 ft agl
Visibility (RVR):
Wind Speed/Gusts: 6 knots /
Turbulence Type Forecast/Actual: /
Wind Direction: 170°
Turbulence Severity Forecast/Actual: /
Altimeter Setting: 29.85 inches Hg
Temperature/Dew Point: 20°C / 12°C
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: Maxwell, CA
Type of Flight Plan Filed: None
Destination: Maxwell, CA
Type of Clearance: None
Departure Time: 1700 PDT
Type of Airspace: Class G
Wreckage and Impact Information
Crew Injuries: 1 None
Aircraft Damage: Substantial
Passenger Injuries: N/A
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 1 None
Latitude, Longitude: 39.293611, -122.251389
14 CFR Part 137: Agricultural
Accident occurred Friday, May 06, 2016 in Maxwell, CA
Aircraft: BELL UH 1B, registration: N486SA
Injuries: 1 Uninjured.
This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
On May 6, 2016, about 1700 Pacific daylight time, a Bell UH-1B, N486SA, was substantially damaged during a forced landing following a loss of main rotor and engine RPM during takeoff from a private staging area near Maxwell, California. The helicopter was registered to a private individual and operated by Jones Flying Service, Biggs, California, under the provisions of Title 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 was filed for the local aerial application flight which was originating at the time of the accident.
The pilot reported that after loading 300 gallons of chemical within the hopper, he conducted a pre takeoff checklist, noting all instruments indicated normally. The pilot initiated takeoff from the truck, and as it climbed over the tree canopy, the rotor and engine RPM began to decay rapidly. The pilot initiated a right turn and attempted to gain airspeed and recover the rotor RPM, however, was unsuccessful, and initiated a landing within an almond orchard. Subsequently the helicopter landed hard and came to rest upright.
Examination of the helicopter by a Federal Aviation Administration (FAA) inspector revealed that the fuselage and tailboom were structurally damaged. The wreckage was recovered to a secure location for further examination.
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