Colorado Aviation Accidents & Incidents

HISTORY OF FLIGHT

On January 26, 2015, about 1202 mountain standard time (MST), an Enstrom 280FX, N86235, was destroyed when it impacted terrain during final approach for landing at Erie Municipal Airport (EIK), Erie, Colorado. Both the instructor pilot and student pilot were fatally injured. The helicopter was registered to New Course Aviation Company and operated by Mountain One Helicopters as a 14 Code of Federal Regulations Part 91 instructional flight. Visual meteorological conditions prevailed for the local flight, which operated without a flight plan.

According to a witness interview, the helicopter was on final approach to land on the runway at what seemed like a steep angle of descent. As the helicopter descended, she heard a loud "pop." After the pop, the helicopter began to rotate and then the main rotor (MR) blades separated from the top of the helicopter. The remainder of the helicopter descended to ground impact and then "exploded."

All three MR blades were found during the on-scene investigation and were identified as blades #1 through #3. The #2 MR blade was found separated from the MR head, which still contained MR blades #1 and #3. Post accident examination revealed that the #2 MR blade had separated due to a fractured spindle.

PERSONNEL INFORMATION

AIRCRAFT INFORMATION

The helicopter, an Enstrom 280FX, was a three-seat, single-engine helicopter (serial number 2002) manufactured in 1985. The three-bladed MR system was powered by a turbo-charged Lycoming HIO-360-F1AD engine rated at 225 horsepower at 3050 rpm.

The inboard end of each main rotor blade is attached to its respective grip and drag link. Each rotor blade is attached to the outboard side of its respective grip via a retention bolt. At the inboard side of each grip, a pitch arm and drag link are attached to the leading and trailing sides, respectively, of the grip. Two feather bearings, which accommodate rotor blade pitch change motion, a bearing spacer, and a spindle are installed within the grip. A Lamiflex bearing, a spindle retention nut, and a cover are installed at the threaded outboard end of the spindle. Two flanges at the inboard end of the spindle attach to a universal block, the latter of which is attached to the main rotor hub, that accommodate rotor blade flapping and lead-lag motions. See figure 1.



Figure 1: Enstrom spindle and grip assembly

According to the maintenance records, the most recent 100-hour inspection was completed on March 17, 2014, at an airframe total time of 9,167 hours. During this annual inspection, all three Lamiflex bearings were replaced. Additionally, all three MR grip assemblies were removed to "purge and clean" the flapping hinge bearings, then were reassembled and preloaded per the Enstrom Maintenance Manual. Lastly, the leading-edge tape was replaced on one of the MR blades; the helicopter was then flight tested and subsequently adjusted for proper track and balance. No other maintenance to the MR grips or blades wa