Monday, November 11, 2019

Loss of Engine Power (Total): Robinson R44 II, N744AK; accident occurred July 29, 2018 at Bettles Airport (PABT), Alaska

Accident helicopter after recovery with the engine installed. 

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

Aviation Accident Factual Report - National Transportation Safety Board:

Investigation Docket - National Transportation Safety Board:

Accident helicopter’s engine after removal from the helicopter. 

Location: Bettles, AK
Accident Number: ANC18LA058
Date & Time: 07/29/2018, 0912 AKD
Registration: N744AK
Aircraft: Robinson R44
Aircraft Damage: Substantial
Defining Event: Loss of engine power (total)
Injuries: 3 None
Flight Conducted Under: Public Aircraft

On July 29, 2018, at about 0912 Alaska daylight time, N744AK, a Robinson R44 II helicopter, sustained substantial damage during a forced landing following a total loss of engine power shortly after takeoff from the Bettles Airport (PABT), Bettles, Alaska. The commercial pilot and two passengers were not injured. The helicopter was registered to and operated by Quicksilver Air Inc., under the provisions of 14 Code of Federal Regulations Part 91 as a public-use flight. Visual meteorological conditions prevailed and company flight following procedures were in effect. The flight departed PABT about 0908.

According to the pilot, he had computed the weight and balance and performed a preflight inspection prior to departure. After the passengers boarded the helicopter, the engine was started, and all ground run-up checks of the engine were satisfactory. He stated that about 4 minutes after liftoff the helicopter lost all engine power. He entered an emergency autorotation and landed the helicopter in a bog. During the emergency landing, the tips of the helicopter's skids broke though the vegetative matt on the bog's surface and the main rotor blades impacted the tailboom. The helicopter sustained substantial damage to the fuselage and tailboom.

Examination of the recovered Lycoming IO-540-AE1A5 engine revealed that it remained attached to the airframe via all its mounts. All fuel lines, throttle, and mixture control cables were intact and remained attached to the engine. The bottom spark plugs were removed and remained free of mechanical damage. The bottom spark plugs exhibited coloration consistent with normal operation. The cooling fan nut was rotated in the direction of normal rotation. No movement of the intake and exhaust rocker arms was observed. The oil suction screen was removed and found to contain metallic fragments. The engine was removed from the airframe for further examination.

The left and right magneto, vacuum pump, oil filter and rear accessory housing was removed from the engine. The crankshaft idler gear and gear shaft was observed loose from their mount. Both the bolt and stud were separated from the crankcase and their respective bores were elongated. Heavy fretting, gouging, and smearing was observed around the mounting surface for the crankshaft idler gear shaft. Fragmented remains of the safety wire, stud, nut and bolt were located in the oil sump. Examination of images of the components by the National Transportation Safety Board (NTSB) Materials Laboratory revealed impact wear and deformation around both crankcase mounting holes and the shaft flange mounting face, was consistent with the partial or complete loss of bolt and stud clamping force of the shaft flange to the crankcase. The NTSB's Materials Laboratory Factual Report is available in the public docket for this accident.

Review of the helicopter's maintenance records revealed that the overhauled engine was installed on the accident helicopter on July 10, 2015 at a total time in service of 6,600.0 hours. The last logged maintenance activity in which the fasteners could have been manipulated was performed at the engine overhaul, about 3 years prior to the accident. The engine had accumulated about 727 operating hours since that time. The most recent 100-hour inspection was conducted 18.1 hrs before the accident on July 21, 2018, at an engine total time in service of 7,309.3 hrs, and 709.3 hrs since major overhaul. No logbook entries were observed concerning the idler gear shaft mounting stud and fasteners.

The oil filter element which had been cut and examined at the most recent 100-hr inspection was located and reexamined and found to contain greater than 60 small pieces of shiny flake like metallic material with some of those flakes estimated to be greater than 1/16 inch in diameter.

According to the operator, the mechanic who completed the most recent 100-hr inspection examined the oil filter with the aid of a magnet and found no ferrous material and did not observe any significant amount of non-ferrous particles. In addition, the oil screen was examined, and no metallic material was found.

Rear view of the helicopter’s engine after removal of the rear accessory housing. 

Lycoming Mandatory Service Bulletin No. 480F, Oil Servicing, Metallic Solids Identification After Oil Servicing, and Associated Corrective Action, states in part:

Oil Filter Element Inspection

1. Cut open the removed oil filter element with an approved tool (e.g., for full-flow filters, use Champion Tool CT-470) per the tool manufacturer's instructions.

2. Remove the paper element from the oil filter.

3. Carefully unfold the paper element to prevent loss of collected particles which can compromise the integrity of this inspection.

4. Examine the material trapped in the filter. Look for shiny metallic particles/residue, shavings or flakes. Refer to the sections: "Identification of Metallic Solids After Oil Servicing" and "Visual Inspection of the Oil Filter Element, Oil Pressure Screen, and Oil Suction Screen" in this Service Bulletin.

5. Record all inspection findings and any corrective action in the engine logbook.

Table 3

Guidelines for Particle Quantity and Size on Oil Filter, Oil Pressure Screen, or Oil Suction Screen

Recommended Corrective Action Options

Table 4

Recommended Corrective Action Options

(Refer to the applicable Lycoming Engine manual for procedures)

The closest weather reporting facility is Bettles Airport (PABT). At 0853, an METAR from PABT was reporting in part: wind, calm; visibility, 10 statute miles; sky condition, few clouds 11,000 feet; temperature, 66° F; dew point 55° F; and an altimeter setting of 30.11 inches of mercury. 

Crankcase shaft flange mounting face and mounting holes. 

Pilot Information

Certificate: Commercial
Age: 48, Male
Airplane Rating(s): None
Seat Occupied: Right
Other Aircraft Rating(s): None
Restraint Used:
Instrument Rating(s): Helicopter
Second Pilot Present: No
Instructor Rating(s): Helicopter; Instrument Helicopter
Toxicology Performed: No
Medical Certification: Class 2 With Waivers/Limitations
Last FAA Medical Exam: 01/03/2018
Occupational Pilot: Yes
Last Flight Review or Equivalent: 05/20/2018
Flight Time:  2791 hours (Total, all aircraft), 1566 hours (Total, this make and model), 2656 hours (Pilot In Command, all aircraft), 98 hours (Last 90 days, all aircraft), 18 hours (Last 30 days, all aircraft), 3 hours (Last 24 hours, all aircraft)

Image of idler gear, idler gear shaft and flange, mounting bolt pieces, and mounting stud pieces with nut. 

Aircraft and Owner/Operator Information

Aircraft Make: Robinson
Registration: N744AK
Model/Series: R44 II
Aircraft Category: Helicopter
Year of Manufacture:2003
Amateur Built: No
Airworthiness Certificate: Normal
Serial Number: 10001
Landing Gear Type: High Skid;
Date/Type of Last Inspection: 07/21/2018, 100 Hour
Certified Max Gross Wt.: 2500 lbs
Time Since Last Inspection:
Engines: 1 Reciprocating
Airframe Total Time: 7327.4 Hours at time of accident
Engine Manufacturer: Lycoming
ELT: C91 installed, not activated
Engine Model/Series: IO-540 SER
Registered Owner: Quicksilver Air Inc
Rated Power: 245 hp
Operator: Quicksilver Air Inc
Operating Certificate(s) Held: On-demand Air Taxi (135)

Oil filter element with shiny flake like metal material from previous 100 hour, 18.1 hours prior to the accident. 

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual Conditions
Condition of Light: Day
Observation Facility, Elevation: PABT
Distance from Accident Site:
Observation Time: 1753 UTC
Direction from Accident Site:
Lowest Cloud Condition: Few / 11000 ft agl
Visibility:  10 Miles
Lowest Ceiling: None
Visibility (RVR):
Wind Speed/Gusts: Calm /
Turbulence Type Forecast/Actual:
Wind Direction:
Turbulence Severity Forecast/Actual:
Altimeter Setting: 30.11 inches Hg
Temperature/Dew Point: 19°C / 13°C
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: Bettles, AK
Type of Flight Plan Filed: Company VFR
Destination: Bettles, AK
Type of Clearance: None
Departure Time:  AKD
Type of Airspace: Class G

Oil filter element with shiny flake like metal material from previous 100-hour inspection, with some flakes estimated to be greater than 1/16 of an inch. 

Wreckage and Impact Information

Crew Injuries: 1 None
Aircraft Damage: Substantial
Passenger Injuries: 2 None
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 3 None
Latitude, Longitude: 66.860556, -151.645278 (est)

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