History of Flight
On May 23, 2008, at 1428 mountain daylight time, a Maule MX-7-235, registration N5657Y, impacted high-tension power transmission lines near Boulder, Montana. The owner/pilot operated the airplane under 14 CFR Part 91. The cross-country personal flight departed Skypark Airport (BTF) in Bountiful, Utah, at 1129, with a planned destination of Helena, Montana. Before departure, the pilot received a weather briefing that advised VFR flight was not recommended along the intended route. The pilot had filed and opened a VFR flight plan. The pilot attempted to transit a mountain pass located about 20 miles south of Helena airport. The airplane struck a high-tension wire with its left wing. Emergency personnel at the scene reported that fog, low clouds, snow, and rain were present before and after the accident. A passenger told rescue personnel that the engine experienced no mechanical failures or malfunctions during the flight.
Personnel
The 71-year-old pilot held an airline transport pilot certificate with ratings for airplane single-engine land and multiengine land. He had previously held a certified flight instructor certificate that expired May 31, 1967. The pilot also held a flight engineer certificate (issued 1972) with turbojet and turboprop ratings, and an airframe and powerplant mechanic certificate (issued 1965). His second-class medical certificate, issued March 8, 2007, required corrective lenses. He completed a biennial flight review on May 9, 2007. According to his medical application, he had accumulated more than 20,000 total flight hours, with 50 hours in the preceding six months.
Aircraft
The airplane was a Maule MX-7-235, serial number 10001C. At the last annual inspection on April 9, 2008, the airframe had 1,409.2 hours. The engine was a Lycoming IO-540 SER, serial number L22343-48A, which also had 1,409.2 hours at that inspection. The airplane was last fueled on May 23, 2008, at 1101, with 41.7 gallons of 100LL aviation fuel at BTF. Review of maintenance and flight records revealed no unresolved discrepancies before departure.
Meteorological
The closest official weather observation station was Butte, Montana (BTM), 30 nautical miles southwest of the accident site at an elevation of 5,550 feet. A METAR issued at 1453 reported wind from 230 degrees at 3 knots, visibility 10 miles, 2,000-foot overcast ceiling, temperature 7°C, dew point 3°C, and altimeter 29.73 inHg.
Wreckage and Impact
The wreckage came to rest in trees approximately 130 yards northwest of the power lines. A section of the left wing was found about 50 feet west of a broken power line interphase spacer. The left wing was burned and appeared sheared off just inboard of the wing strut attach point; the forward spar exhibited severe aft bending. A three-foot section of the interphase spacer found 30 inches outboard of the left wing root matched the contour of the unburned leading edge damage. The top left wing panel aligned with that damage. Baggage recovered from the wreckage was weighed by the FAA.
Medical and Pathological
The Jefferson County Coroner performed an autopsy and ruled the pilot's death a result of blunt force injuries. Toxicological testing by the FAA Bioaeronautical Sciences Research Laboratory found no carbon monoxide, cyanide, volatiles, or tested drugs.
Tests and Research
A handheld Garmin GPS unit (model 396) was recovered and its data were downloaded and overlaid on Google Earth. The data indicated the airplane followed Interstate 15 until impact. The last data point, recorded at 1428:36 MDT, showed a speed of 103.3 mph. The FAA inspector estimated the airplane's weight at 2,502 pounds, considering empty weight, minimum fuel, pilot and passenger, 374 pounds of luggage, and two dogs. The maximum gross weight was 2,500 pounds.