KENAI, AK, USA
N91056
CESSNA T207
THE AIRPLANE'S ENGINE FAILED SHORTLY AFTER THE FLIGHT'S DEPARTURE FROM THE AIRPORT. THE POST ACCIDENT INSPECTION OF THE ENGINE REVEALED A SURFACE ORIGINATED FATIGUE CRACK IN THE CRANKSHAFT AT THE NUMBER TWO CRANKCHEEK. AT THE TIME OF THE MISHAP, THE ENGINE HAD ACCRUED A TOTAL OF 86 HOURS SINCE OVERHAUL BY THE OPERATOR. THE PILOT COMMENTED TO ALASKA STATE POLICE PERSONNEL THAT HE HAD SUFFICIENT ALTITUDE TO LAND THE AIRPLANE ON THE AIRSTRIP.
On July 8, 1994, at 1715 Alaska daylight time, a wheel equipped Cessna T (turbo) 207 airplane, N91056, operated and maintained by South Central Air of Kenai, Alaska, experienced a total loss of engine power and collided with terrain near the Arness Lake landing strip located about 6 miles northwest of Kenai, Alaska. The airline transport certificated pilot-in-command, the sole occupant, was seriously injured and the airplane sustained substantial damage. The flight last departed the Kenai Airport at approximately 1710 and the intended destination was Trading Bay, Alaska. The all cargo flight was being conducted under the on demand rules contained in 14 CFR Part 135. A company VFR flight plan was in effect and visual meteorological conditions prevailed. The pilot was transported from the scene of the accident to Providence Hospital in Anchorage, Alaska on the evening of July 8, 1994. The NTSB investigator-in-charge interviewed the pilot by telephone on the morning of July 9, 1994, with the approval of the attending nurse and physician. The pilot said that shortly after establishing the engine climb power settings of somewhere between 28 inches and 30 inches of manifold pressure and RPM to the bottom of the yellow arc, he noticed a fluctuation in either fuel flow and/or fuel pressure and that the engine power began to fluctuate. The other engine pressure/temperature indications appeared normal. The fuel flow fluctuated between 18 gallons per hour (GPH) and 14 GPH. The engine seized up within 10 seconds of the onset of the power interruption. There was no metallic or grinding nose associated with the engine stoppage. He advised the Kenai Airport traffic control tower that he was going to attempt an emergency landing at the Arness Road Airstrip. He maneuvered the airplane for a south approach/landing. He attributed a stronger than anticipated headwind for placing him at the approach end of the strip at a an altitude that was too high to maneuver for a safe landing on the strip. The airplane touched down beyond the end of the strip. The pilot reported that he had plenty of fuel on board the airplane but that he did not drain the engine or wing tip fuel sumps prior to departing Kenai. He said that this was normally done during the first flight of the day. During the airplane preflight, he determined that the engine oil sump contained 12 quarts. The failed engine was a Teledyne Continental Motors model TSIO-520-CCG, having serial number 140794-9-C. The engine's maintenance log revealed that at the time of the accident, it had accrued a total of 86 hours since being overhauled by South Central Air. The engine was last inspected at 50 hours on June 29, 1994. There were no recent entries in the engine log pertaining to mechanical problems. A post accident inspection of the engine revealed that the crankshaft had failed. The major mechanical portions of the engine were subsequently shipped to Teledyne's maintenance facility in Mobile, Alabama for a more detailed examination under the scrutiny of Mr. John V. Moeller, a Federal Aviation Safety Inspector/Manufacturing. The report by Mr. Moeller, (copy enclosed) revealed that the crankshaft had failed through the number two crankcheek. A second fracture was present at the trailing number one connecting rod counterweight blade. The crankshaft was examined by the TCM Metallurgist who indicated the failure was the result of a surface origin fatigue initiating at the forward fillet of the number one connecting rod journal. The number one connecting rod had contacted the fillet resulting in heat cracks and fatigue initiation. The fracture progressed into the trailing counterweight pin bushing hole resulting in an overload failure of the corner of the counterweight hanger blade on the crankshaft. Federal Aviation Administration and Alaska State Trooper (AST) personnel who visited the scene of the mishap reported that the airplane touched down about 200 feet from the departure end of the south runway and continued several hundred feet into the swamp. The pilot reported to the AST on scene that, "I had sufficient altitude to land". Two witnesses reported that the airplane initially touched down near the south end of the airstrip then bounced over some trees and landed in the swamp.
THE FAILURE OF THE ENGINE CRANKSHAFT. FACTORS IN THE ACCIDENT WERE THE PILOT'S INADEQUATE COMPENSATION FOR THE WIND CONDITIONS AND NOT ATTAINING THE PROPER TOUCHDOWN POINT AT THE SUITABLE LANDING STRIP.
Source: NTSB Aviation Accident Database
Aviation Accidents App
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