Accident Overview
On May 15, 2015, at about 0840 central daylight time, a Cessna T206H airplane, registration N164CS, overran the end of the runway at Piggott Municipal Airport (7M7) in Piggott, Arkansas, following a rejected takeoff. The airline transport rated pilot received minor injuries, and the airplane was substantially damaged. The aircraft was registered to and operated by Mid Continent Aircraft Corporation of Hayti, Missouri, under 14 CFR Part 91 as a cross-country flight. Visual meteorological conditions prevailed at the time. The flight was originating from 7M7 and destined for Walnut Ridge Regional Airport (KARG) in Walnut Ridge, Arkansas.
Pilot Report and Sequence of Events
The pilot stated he planned to depart from runway 18 with the airplane configured for a no-flap takeoff. After about 1,000 feet down the runway, he rotated the airplane. When the airplane reached an altitude of approximately 20-30 feet, the engine "surged" and then lost power. The airplane subsequently settled back onto the runway but was traveling too fast to stop on the remaining runway. The airplane came to rest in an irrigation ditch near the runway. The pilot's airbag deployed during the accident.
Aircraft Damage and Recovery
Initial examination revealed substantial damage to the left wing and fuselage. The airplane was recovered from the ditch, but it sustained extensive damage during the recovery, including separation of the empennage from the fuselage.
Aircraft and Engine Details
The airplane was a 2014 Cessna turbo Stationair (T206H) powered by a Lycoming TIO-540-AJ1A six-cylinder reciprocating engine rated at 310 hp. The hobbs meter read 113.6 total flight hours. The aircraft was equipped with a Garmin G1000 avionics suite; engine monitoring data was downloaded from the unit. Maintenance records indicated the most recent manufacturer's inspection was completed on March 30, 2015, at a hobbs time of 96.1 flight hours.
Investigation and Examinations
The NTSB Investigator in Charge (IIC), an FAA Inspector, and technical representatives from the airframe and engine manufacturers examined the airplane at a salvage yard in Clinton, Arkansas. A visual engine examination found no anomalies, so an engine run was planned, but damage to the engine mount and propeller limited the test to low power settings. During the test run, a malfunctioning left magneto was discovered. Records showed the left magneto had been replaced at a hobbs time of 98.0 hours.
The engine was separated and shipped to Lycoming's facility in Williamsport, Pennsylvania. The left magneto was replaced with a factory test unit, and an engine test run was conducted with no abnormalities noted.
The fuel injection servo unit was removed and sent to Precision Airmotive, LLC, where it was bench tested and found satisfactory, with no performance abnormalities. Disassembly revealed two separation areas on the fuel diaphragm that did not appear during the bench test.
Both the original and replacement left magnetos were examined at Champion Aerospace in Liberty, South Carolina. The original magneto appeared operational on the bench test. The replacement magneto (on the engine at the time of the accident) initially displayed normal ignition spark, but as rpm increased, the spark became erratic and failed to produce spark on all six terminals at times.
Disassembly of the failed magneto revealed small bits of plastic-like material consistent with the magneto's rotor. The rotor arm attached to the plastic rotor was out of position and could turn independent of the rotor. The contact points inside the magneto cap showed abnormal wear. Among the pieces found inside the magneto was a section of a drill bit about 3/8 inch long. During maintenance, a timing pin (Slick T-118 Magneto Locking pin) is used to time the magneto; the section of drill bit approximated the diameter of the timing pin.
Engine Monitor Data
Review of the accident data from the engine monitor showed three areas of exhaust gas temperature (EGT) spikes. Two spikes before the takeoff roll were attributed to the pilot conducting magneto checks. The third spike occurred during takeoff just before a reduction in engine rpm. The data is consistent with the left magneto failing during the takeoff.