NYC95FA188

The pilot departed at night and initiated a climb to cruise altitude. A witness heard the engine(s) operating normally, and then silence. The witness then observed the airplane, descending and rotating in a nose down attitude. The airplane descended through trees, in a left spin, and impacted the ground. An examination revealed that both propellers were feathered, and the landing gear was retracted. The inspection of the left engine disclosed that the number six and number five connecting rods had failed, and the number four connecting rod had evidence of overheating. There was evidence that the number six rod had failed first, allowing for oil starvation and subsequent failure of the number five connecting rod.

History of flight

On August 13, 1995, about 2135 eastern daylight time, a Beech 58, N168CG, struck trees in Mapleton, Maine. The airplane was destroyed, and the private pilot was fatally injured. The business flight had departed Caribou, Maine, about 2125. Visual meteorological conditions prevailed, and no flight plan had been filed for the flight which was conducted under 14 CFR Part 91.

The airplane arrived in Caribou, earlier in the evening, and was serviced with 118.8 gallons of 100 LL aviation gasoline. One witness, who had observed the pilot and airplane depart on other flights, reported the engine run-up was longer than usual, and the engines did not sound right to him; however he did not observe or hear anything unusual during the takeoff.

Destined for Pease, New Hampshire, the pilot contacted Bangor Approach Control at 2129, where he was issued the current altimeter, and assigned a transponder code. No further communications were received from the pilot.

A witness, in Mapleton, reported that he heard the engine(s) operating normally, and then stop abruptly. He looked up and saw the lights of the airplane which were, "nose down, rotating like a corkscrew." As the lights disappeared from view, he heard a thud, and then silence.

The accident occurred during the hours of darkness at location 46 degrees, 40 minutes north and 68 degrees, 10 minutes west.

Personnel information

The pilot possessed a Private Pilot Certificate with limitations for airplane single and multi-engine land, and instrument airplane. He was last issued an FAA Airman 3rd Class Airman Medical Certificate, with no limitations, on August 1, 1993.

A review of the last 2 years of the pilot's log book revealed that the pilot averaged 40 hours a month. Other than a biennial flight review on June 21, 1994, the last recorded multi- engine training was conducted in June, 1990.

Aircraft information

The airplane had been modified with the addition of vortex generators. According to the Supplemental Type Certificate, the minimum control speed (Vmc) was lowered from 84 knots IAS, to 74 knots IAS.

According to log book records, the left engine was overhauled on July 18, 1994, at a tach/total time of 1737.75 hours. On August 4, 1995, at a tach/total time of 2294.1 hours, the engine received a 100 hour inspection, during which the numbers one, two, four, five, and six cylinders were changed.

Wreckage and impact information

The airplane was examined on August 14, and 15, 1995. The airplane had descended through trees about 50 feet tall, and impacted level ground. The surrounding area showed no broken branches, other than directly above the airplane.

Both propellers were found feathered and separated from their engines, with no evidence of propeller rotation at ground impact.

The right wing was attached, and the left wing was separated 3 feet outboard of the left engine. The empennage had separated from the aft fuselage, bending to the right, and was still attached by control cables. A crush line was observed on the left side of the fuselage, in line with the instrument panel, which was angled at 45 degrees. Crushing was more visible on the left side of the fuselage. Flight control continuity was established with all primary flight controls.

Overlapping folds of metal were found on the bottom of both engine cowlings. On the left, they were bent forward, and on the right, they were bent aft.

Fuel was found in the lines leading to both engines. The propeller governors were found in the feathered position. Both fuel pump shear shafts were intact.

On the right engine, valve train continuity was confirmed. Compression was found in all cylinders, and spark was produced from both magnetos. The engine oil filter was clean.

On the left engine, a hole was found in the engine cowling and engine case, over the number six connecting rod journal. The metal on the engine cowling was bent outward, and the hole in the engine case measured 7 inches wide and 4 inches long. The oil pattern on the top of the engine cowling sprayed both forward and aft.

The number six piston wrist pin was found on the right side of the left engine cowling. The connecting rod was found 40 feet in front of the left engine. In addition, the number five connecting rod was found detached from the crankshaft, but still inside the engine case. The oil pan on the bottom of the engine was crushed, and punctured. Bearing material, and ferrous material was found in the engine oil filter. The magnetos produced spark when rotated by hand.

Medical and pathological information

An autopsy was conducted by Kristen Sweeney, M.D., Deputy Chief Medical Examiner for the State of Maine, on August 14, 1995.

Toxicological testing was conducted by the FAA Civil Aeromedical Institute, in Oklahoma City, Oklahoma. No drugs of abuse were found, and no alcohol was found in blood or virtreous fluid.

Tests and research

The left engine was examined at Teledyne Continental Motors, in Mobil, Alabama, on November 16, 1995, under the supervision of the NTSB Investigator-In-Charge.

The engine oil pump was found to be operative. A check of the oil galleys and passageways on the crankcase and crankshaft found no evidence of blockage.

The oil flow through the engine was from the rear to the front.

The number one (rear of engine), two, and three, connecting rods remained attached to their respective crankshaft journals. They rotated smoothly and freely.

The crankshaft journals were discolored with number one being the least, and number 3 the most.

The number four connecting rod was intact and attached. The bearing inserts were worn and partially extruded from the rod cap and yoke. The crankshaft journal was discolored black, and not smooth to touch.

The number five connecting rod had failed in the beam above the yoke. A portion of one bolt with nut attached and portions of the rod cap and yoke were identified. The crankshaft journal was discolored black, and not smooth to touch.

The number six connecting rod (front of engine) was separated from the crankshaft and piston. The connecting rod cap, one connecting rod bolt, one connecting rod nut, and one connecting rod bearing inset were not identified in the engine debris. The connecting rod bolt was bent and the threads were bent. The connecting rod nut had metal impacted in the threads.

The number six crankshaft rod bearing journal had no evidence of heat distress, and was smooth to touch. The bearing inset was flattened, and had no evidence of heat distress.

There was no evidence of seizure between the number six piston and cylinder.

On the IO-550-C engine, there were no provisions for external locking of the connecting rod nut to the connecting rod bolt.

The recovered bearing surfaces along with the connecting rod bolt found in the debris were forwarded to NTSB Laboratory in Washington, D.C. for examination. According to their report:

...No evidence of heat discoloration was noted on any of the [bearing] insets, including the insert from the No. 6 crankpin.

The connecting rod cap bolt was bent, but was not broken or cracked. The threads on the bolt contained multiple severe impact marks. In addition, the thread crowns appeared to have been rolled over, consistent with forcible removal of a nut over the threads. A portion of one thread near the end of the bolt was stripped (sheared).

Additional information

Following are excerpts from the Beech 58 Pilot's Operating Handbook:

Section X Safety Information

Spins

...In any twin engine airplane, fundamental aerodynamics dictate that if the airplane is