N255VS is a 2014 Robinson Helicopter R44 II. It is a rotorcraft with 4 seats, powered by a Lycoming IO-540-AE1A5 rated at 260 horsepower. The registration is active, with the registrant based in Valdez, AK. Its standard airworthiness certificate was issued in Apr 2014. It has been registered to its current owner since Apr 2014. This page also carries 1 NTSB event.
- 12 years old
2014
That's everything on file so far — TailWiki checks the FAA registry daily and adds new entries as N255VS's record changes.
On December 16, 2015, about 0942 Alaska standard time, N255VS, a Robinson R44 II helicopter, sustained substantial damage during a forced landing following a total loss of engine power during takeoff from the Valdez Airport, Valdez, Alaska. The commercial pilot and two passengers were not injured. The helicopter was registered to and operated by Vertical Solutions, LLC, under the provisions of 14 Code of Federal Regulations Part 91 as a power line patrol flight. Visual meteorological conditions prevailed and an FAA flight plan had been filed. The flight departed Valdez Airport about 0938.
During an on-scene interview with the National Transportation Safety Board (NTSB) Investigator-in-Charge (IIC) on December 18, 2015 the pilot stated that he had computed the weight and balance, and performed a preflight inspection prior to pushing the helicopter out of the hangar. After the passengers boarded the helicopter, and the passenger safety briefing was completed, the engine was started and allowed to warm up for about 5 minutes, and all ground run-up checks of the engine were satisfactory. He stated that after liftoff he hovered the helicopter about 10 feet above ground level (AGL), before commencing a left turn, accelerating to about 25 knots and initiating a climb. As the helicopter climbed through about 20 feet AGL all engine power was lost. He entered an autorotation but the helicopter landed hard, sustaining substantial damage to the fuselage, skids and tail boom.
The helicopter was equipped with a reciprocating Lycoming IO-540-AE1A5 series engine, equipped with a AVStar RSA-10-AD1 fuel injection servo.
On December 18, 2015, an engine examination was performed by the NTSB IIC. No anomalies, contamination, or evidence of malfunction was found in any of the engine accessories, but the fuel injection servo was removed for further examination and testing. The cylinders, pistons, valve train, crankshaft, and other internal components were all without evidence of anomaly or malfunction.
Both magnetos were removed from the engine and the coupling was rotated. When the coupling was rotated, strong blue spark was produced from each terminal, in rotational order.
A review of the helicopter's maintenance records revealed that the fuel injection servo had been repaired on December 9, 2015 by Alaskan Aircraft Engines Inc., Anchorage, Alaska, and had been reinstalled on the helicopter about 2.1 hours prior to the accident flight.
On January 14, an NTSB investigator and a representative from AVStar Fuel Systems, Inc. examined the fuel injection servo at the facilities of AVStar Fuel Systems, Inc. in Jupiter, Florida. The fuel servo was placed on the test bench, and all test points were within serviceable limits using AVStar Service Bulletin AFS-AB12 "Service Limits for AVStar Fuel Servos" with the exception of the adjusted idle flow with adjustment wheel centered. The adjusted idle flow with fuel wheel centered should be between 14 – 15 pounds per hour (lb/hr), and was found to be at 16.4 lb/hr, but this is considered a field adjustment.
Disassembly inspection revealed a very small amount of white contamination ranging in size from small specs to about 0.10 of an inch. The contamination was present on the fuel diaphragm, the fuel area adjacent to the regulator valve seat, mixture control valve, mixture control plate, and the bore of the valve train opening. In addition, the interior of the mixture control assembly adjacent to the mixture control stem bushing exhibited evidence of lubricant material consistent with DuPont Krytox.
On January 19, the NTSB IIC along with another NTSB investigator, and two FAA aviation safety inspectors visited the facilities of Alaskan Aircraft Engines Inc. in Anchorage, and disassembled a recently overhauled fuel injection servo. The inspection revealed excessive amounts of a white grease like substance throughout the fuel injection servo, consistent with the white contamination noted in the servo removed from the accident helicopter. A representative from Alaskan Aircraft Engines stated that about 6 months prior they had switched assembly lubricants to Dupont Krytox, an approved lubricant, but due to the investigation, realized it was being used in excess and in locations not approved per the maintenance manual.
Dupont describes Krytox 240 series greases in part: "As white, buttery greases based on perfluoropolyether (PFPE) oils. These synthetic fluorinated lubricants are used in extreme conditions such as continuous high temperatures up to 300°C (572°F) and higher temperatures for shorter periods, depending on product grade limits. Chemically inert and safe for use around hazardous chemicals, these lubricants are nonflammable and are safe for use in oxygen service."
A review of the AVStar Servo Fuel Injector Overhaul and Repair Manual for the RSA-10-AD1 fuel injection servo assembly lists four places where DuPont Krytox is to be used during assembly states, in part:
"LAPPING THE VALVE-LOWER IDLE, SHAFT-IDLE VALVE, AND THE PLATE-MIXTURE CONTROL
Before reassembly with mating parts, very lightly apply DuPont Krytox to one mating surface.
CAUTION! Do not allow any amount of Krytox to enter a hole, a slot or reach any edge of the part to which it has been applied.
Carefully remove any Krytox.
Apply DuPont Krytox to the lever assembly-mixture control. Apply carefully to the space between the lever stop and the packing-preformed.
NOTE! Remove excess Krytox with P-D-680, Acetone or MEK, as needed.
Apply DuPont Krutox grease to the idle valve shaft outboard of the packing-preformed.
NOTE! Remove excess Krytox with P-D-680, Acetone or MEK, as needed.
Apply a light coat of Krytox on the concave side of seal-servo. Place the seal-servo stem over the bullet with the concave side up. Press seal down on diaphragm stem. Remove all traces of lubricant from the bullet and the stem."
On January 19, 2016 Alaskan Aircraft Engines issued a Service Advisory that stated, in part: "Beginning in June of 2015 Alaskan Aircraft Engines purchased and began use of an approved assembly lube it had not used previously. This lube was used in excess and in locations not required by the manufacturer's service manual. We believe this has the potential to cause a fuel distribution problem." A complete copy of the Service Advisory is included in the public docket for this accident.
The closest weather reporting facility is Valdez Airport. At 0936, an aviation routine weather report (METAR) at Valdez, Alaska, reported in part: wind, calm; visibility, 10 statute miles; sky condition, broken clouds 7,000 feet, overcast 8,000 feet; temperature, 21 degrees F; dew point 21 degrees F; altimeter, 29.97 inHG.
Additional Information
Before this accident investigation was completed (and before the results of the component examinations were known) another Robinson R44 II helicopter experienced a similar event involving a fuel injection servo overhauled by the same repair facility that resulted in a total loss of engine power. See NTSB ANC16IA013 for more information about that incident.
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