Sunday, May 06, 2018

Robinson R44 II, N247DB: Accident occurred August 12, 2016 in Gunnison, Sanpete County, Utah

The National Transportation Safety Board did not travel to the scene of this accident.

Additional Participating Entity:
Federal Aviation Administration / Flight Standards District Office; Salt Lake City, Utah

Aviation Accident Factual Report - National Transportation Safety Board:

Investigation Docket - National Transportation Safety Board:

Aviation Accident Factual Report - National Transportation Safety Board

Location: Gunnison, UT
Accident Number: WPR16LA165
Date & Time: 08/12/2016, 1225 MDT
Registration: N247DB
Aircraft Damage: Substantial
Defining Event: Loss of engine power (total)
Injuries:  1 None
Flight Conducted Under: Part 137: Agricultural 

On August 12, 2016, about 1225 mountain daylight time, a Robinson R44 II helicopter, N247DB, experienced a loss of engine power during a spray run. The pilot subsequently initiated an off airport forced landing near Gunnison, Utah. The commercial pilot was not injured. The helicopter's tailboom was substantially damaged during the hard landing. The helicopter was registered to and operated by a private individual as a Title 14 Code of Federal Regulations Part 137 agricultural application flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan had been filed. The local flight originated from an off-airport site near Gunnison about 0900.

The pilot reported that he had accomplished one spray load and returned to the loading spot for another load. After fill-up, he returned to the field. During the second pass over the field, the pilot heard a "pop", as well as, a "thump" that resonated through the helicopter about the same time that he was turning off the spray system. The pilot glanced out the right-side door and saw chemical spewing in the air, and along the pilot side of the helicopter. He immediately went to kill the pump by using the kill push button located on the cyclic, by the spray on/off switch. As he was doing so, the engine and rotor rpm began to drop. The pilot reported that it sounded like the engine was "sputtering for air" or being "choked out." The pilot lowered the collective and rolled on throttle to re-establish the rpm to try and revive the engine. As he was performing this procedure, the engine lost total power. The helicopter was about 50-75 feet above ground level, and there was not time to try an engine restart. The helicopter subsequently landed hard and remained upright. During the hard landing, the main rotor blade(s) severed the tailboom.

The pilot reported that a new Simplex Spray System had been installed on the helicopter about 16 hours prior to the accident. The spray system pump is mounted on the pilot (right) side skid. The engine air filter compartment is located above and behind the spray pump.

A review of the accident site photos did not reveal any evidence of chemical residue on the side of the fuselage between the pump and the engine intake manifold.

A postaccident examination of the spray system revealed that a plastic pipe nipple on the spray system fractured. The close nipple and the engine air intake were sent to the National Transportation Safety Board Material Laboratory, Washington D.C. for examination. The materials laboratory specialist reported that the close nipple broke in a two-step sequence. An initial progressive crack was noted through the wall (length: about 1/8 inch of the circumference). The region along the aft side of the close nipple fracture surface revealed fractographic features consistent with a slow crack growth, a progressive fracture mode in polymers. The balance of the fracture exhibited fractographic features consistent with overstress fracture and a region of final fracture. The lower close nipple piece removed from the pump outlet was examined and revealed the slow crack growth region, with the initiation region and a representative area of crazing identified. The fractography generally revealed mechanical damage in the fracture surface immediately adjacent to the thread root. The threat root exhibited features consistent with mold under-fill. Also evident was step features consistent with multiple crack initiation sites typically found in craze cracking in rigid thermoplastics. The inside surface of the close nipple piece removed from the pump outlet, and in the roots of the aft facing thread root revealed secondary cracks. The initiating regions revealed features consistent with mold under-fill.

Examination of the internal and external surfaces of the engine intake filter revealed no cake deposits.

The entire Material Laboratory Factual Report is included in the public docket for this case.

The engine examination revealed that the crankshaft rotated freely, and the valves moved approximately the same amount of lift in firing order. Thumb compression was obtained in all cylinders. The spark plug center electrodes were circular and clean with no mechanical deformation. The spark plug electrodes were gray, with normal operating signatures consistent to the Champion Aviation Check-A-Plug AV-27 Chart. The fuel nozzles were free of contaminants. The magnetos were removed from the engine and installed on another engine. No anomalies were detected with the magnetos during the engine run. The air intake scat hose displayed a light coating of dark colored dust that was greasy to the touch. The number two-cylinder intake tube was disconnected, and no residue was detected.

The engine was subsequently test run in a test cell. The engine ran with no anomalies noted.

Pilot Information

Certificate: Flight Instructor; Commercial
Age: 28, Male
Airplane Rating(s): None
Seat Occupied: Front
Other Aircraft Rating(s): Helicopter
Restraint Used: 3-point
Instrument Rating(s): Helicopter
Second Pilot Present: No
Instructor Rating(s): Helicopter
Toxicology Performed: No
Medical Certification: Class 1 With Waivers/Limitations
Last FAA Medical Exam: 02/05/2016
Occupational Pilot: Yes
Last Flight Review or Equivalent: 07/28/2016
Flight Time:  (Estimated) 1534 hours (Total, all aircraft), 973 hours (Total, this make and model), 1325 hours (Pilot In Command, all aircraft), 345 hours (Last 90 days, all aircraft), 125 hours (Last 30 days, all aircraft) 

Aircraft and Owner/Operator Information

Registration: N247DB
Model/Series: R44 II
Aircraft Category: Helicopter
Year of Manufacture: 2003
Amateur Built: No
Airworthiness Certificate: Normal
Serial Number: 10086
Landing Gear Type: Skid;
Seats: 4
Date/Type of Last Inspection: 05/02/2016, Annual
Certified Max Gross Wt.: 2500 lbs
Time Since Last Inspection: 25 Hours
Engines: 1 Reciprocating
Airframe Total Time: 46.27 Hours at time of accident
Engine Manufacturer: LYCOMING
ELT: Not installed
Engine Model/Series: IO-540-AE1A5
Registered Owner: On file
Rated Power: 260 hp
Operator: On file
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: KDTA, 4755 ft msl
Observation Time: 1835 MDT
Distance from Accident Site: 37 Nautical Miles
Direction from Accident Site: 303°
Lowest Cloud Condition: Clear
Temperature/Dew Point: 29°C / -1°C
Lowest Ceiling: None
Visibility: 10 Miles
Wind Speed/Gusts, Direction: 7 knots, 50°
Visibility (RVR):
Altimeter Setting: 30.23 inches Hg
Visibility (RVV):
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: Gunnison, UT
Type of Flight Plan Filed: None
Destination: Gunnison, UT
Type of Clearance: Unknown
Departure Time: 1215 MDT
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:  39.051111, -111.856111 (est)

NTSB Identification: WPR16LA165
14 CFR Part 137: Agricultural
Accident occurred Friday, August 12, 2016 in Gunnison, UT
Aircraft: ROBINSON HELICOPTER COMPANY R44 II, registration: N247DB
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 August 12, 2016, about 1230 mountain daylight time, a Robinson R44 II, N247DB, sustained substantial damage following a forced landing near Gunnison, Utah. The pilot was operating the helicopter under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91. The commercial pilot was not injured. The local aerial application flight departed about 1200. Visual instrument meteorological conditions prevailed, and no flight plan had been filed.

The pilot stated that a new spray system had been installed on the helicopter about 25 hours prior to the accident. He reported that a plastic piece of the newly installed system fractured in flight which resulted in spray chemicals entering the engine's induction system. The engine subsequently lost power.

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