Accident Summary
On September 3, 2016, at 1830 eastern daylight time, an experimental light sport CGS Aviation Hawk Aero II airplane, registration N4513S, collided with power lines and terrain during an en route climb following takeoff from Park Township Airport (HLM) in Holland, Michigan. The airplane was destroyed. The pilot sustained serious injuries. The airplane was registered to and operated by the pilot under 14 Code of Federal Regulations Part 91 as a personal flight not operating on a flight plan. Day visual meteorological conditions prevailed. The local flight was originating at the time of the accident. A National Transportation Safety Board Pilot/Operator Accident/Incident Report was not received from the pilot.
Pilot Report
The pilot, who was also the airplane owner, stated in a telephone conversation with the NTSB Investigator-In-Charge that the engine never stopped running and was not running at a high engine speed. During the climbout after takeoff, the engine started to sputter about 80-100 feet above ground level. The airplane "started stalling," so he pushed the nose down to increase airspeed to recover from the aerodynamic stall. He said that if the airplane had not hit the power lines, he would not have been involved in an accident.
Post-Accident Examination
Post-accident examination of the airplane and an engine run were performed at the pilot's hangar by a representative from the engine manufacturer and by the Federal Aviation Administration Coordinator for the accident. The engine was a Rotax 582 MOD 99, serial number 543 7309. The examination revealed that all spark plugs were NGK BR8ES with removable resistor caps, not in accordance with the engine manufacturer's maintenance manual. Spark plug gaps were 0.29-0.30 inch, while the manual specifies 0.020 inch. All spark plug electrodes exhibited a color consistent with a rich fuel mixture. The number 4-cylinder spark plug on the magneto side was loose and did not meet torque specification. Both carburetors had larger main jets (190 size instead of the original 165 size), resulting in richer mixtures. Carburetor chokes were blocked off and removed. Jet needles were in the number 4 position instead of number 3 as specified. No fuel filters were installed between fuel pumps and carburetors. The pneumatic fuel pump was installed with its small drain hole positioned horizontally, contrary to the manual's instruction to install it with the hole toward the bottom. The gascolator had industrial-style brass plumbing fittings and a shut-off valve, with plumber's thread seal tape on fuel line threads. No fire sleeve was present on fuel lines. The fuel header tank was a white plastic container consistent with a water jug, with a quick-release connector that leaked a substantial amount of air into the fuel system. The engine manufacturer's maintenance manual states: "Quick release type connectors can cause air leaks and produce fuel flow restrictions and possible blockage sites" and "the tiniest flaw in any joint will cause air to be sucked into the fuel system, considerably reducing the capacity of the fuel pump. Air leaks are much more dangerous when the fuel tank is mounted below the fuel pump and carburetors."
Engine Run
The engine was run for several minutes with multiple throttle inputs during which no anomalies in engine power occurred. Following the accident, the engine manufacturer issued a publication, "Two-Stroke Safety Issues," which in part discussed fuel system air leaks and the use of quick release connectors in the fuel system.