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On March 31, 2003, at 1600 central standard time, a Piper PA-32-300 single-engine airplane, N70NZ, was destroyed when it impacted terrain following a loss of control near Broken Arrow, Oklahoma. The airplane was registered to Tire Barn Inc. of Bixby, Oklahoma, and was operated by the pilot. The private pilot and his two passengers sustained fatal injuries. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 personal flight. The round-robin cross-country flight originated from the Richard Lloyd Jones Jr. Airport (RVS), Tulsa, Oklahoma at 1430.
According to acquaintances of the pilot, the pilot took the passengers out to observe some hunting property. On the return leg of the flight, the pilot contacted Tulsa's terminal radar approach control (TUL TRACON) at 1547, and received a vector to enter a midfield left downwind to runway 19L. At 1549, the pilot advised controllers that his oil pressure was very low and there was some engine noise. The controller advised the pilot that the Harvey Young Airport (1H6) was 3.5 miles to his right and asked the pilot if he wanted to continue to RVS. The pilot indicated that he wanted to continue to RVS.
At 1550, the pilot informed the controller that he had lost engine power and was "going down." The controller asked the pilot if he could make it to 1H6, which was three miles north of his position, to which the pilot indicated he would try. The pilot informed the controllers that there were three persons on board, the engine was on fire, and there were 94 gallons of fuel on board. The pilot informed the controller that he was attempting to make a field to the east of his position. There were no further transmissions from the pilot.
Radar data depicted the aircraft's mode C returns in a steady descent from 3,000 feet when the pilot initially called inbound for landing at RVS. The final three radar returns depicted the airplane in a right turn, with the last return depicting the airplane at 2,200 feet msl (approximately 1,500 feet agl).
With the assistance of the local department of public safety personnel, the NTSB was able to gather 22 witness statements. All but two witnesses reported observing smoke emanating from the engine area (depending on the witness, the smoke color ranged from white, gray, brown, and blue; most reports indicate white or blue). A number of witnesses reported hearing a rough running engine before it went silent. All of the witnesses described observing the airplane roll to the right followed by the nose dropping to a near vertical pitch attitude (five witnesses indicated the airplane stalled and rolled to the right). All of the witnesses indicated that the airplane exploded upon impact with the ground in a near vertical descent attitude.
One witness was an on-duty trooper for the Oklahoma Highway Patrol. The trooper was also a certified pilot. He heard a loud aircraft engine and noted the accident airplane flying overhead. He observed the airplane trailing a "very long" "blue/white smoke trail." The trooper called his dispatch office and asked them to notify air traffic controllers of the smoke coming from the airplane. As the trooper observed the airplane, he noted the smoke getting thicker. The trooper eventually lost sight of the airplane and did not observe the accident. The trooper called the dispatch office at 1541.
The pilot was issued a private pilot certificate on November 15, 2001, with a rating for single-engine land airplanes. On July 16, 2001, the pilot was issued a third-class medical certificate with no waivers or limitations. The pilot's previous instructor reported that the pilot had accumulated a total of 150 hours of flight time, of which approximately 90 hours were accumulated in the accident airplane. The pilot's logbook was not recovered during the investigation and it is assumed to have been destroyed.
The 1979-model airplane (serial number 32-7940073) was registered to the pilot's corporation on November 28, 2001. The airplane was equipped with a Lycoming IO-540-K1G5 engine (serial number L-19129-48A) and a two-bladed variable pitch Hartzell propeller. The airplane was registered, maintained, and operated in Australia until May 2001, at which time it was shipped to the U.S. On July 17, 2001, at an aircraft total time of 3,947.14 hours, the aircraft was recertified in the U.S. by a designated airworthiness representative. On August 22, 2002, the last annual inspection was performed. At that time, the airframe had accumulated a total of 4060.2 hours. At the time of the last annual inspection, the propeller was removed and reinstalled for compliance with airworthiness directive (AD) 01-23-08.
The IO-540-K1G5 produces 300-horsepower and is a 6-cylinder, air-cooled, fuel-injected, normally aspirated engine.
Review of the maintenance records revealed the engine was overhauled in Australia on July 15, 1999. Following that overhaul, the engine was test run 2 hours and 15 minutes with no anomalies noted. On July 9, 2001, (approximately 132 hours after the overhaul) a compression check was conducted on the accident engine with the following results: #1 74, #2 74, #3 75, #4 74, #5 76, #6 70. During the August 2002 annual inspection, the engine had accumulated a total time of 4,060.3 hours and a total time since major overhaul of 245.1 hours.
At 1353, the weather observation facility at the Tulsa International Airport, Tulsa, Oklahoma (located nine miles north of the accident site), reported the following weather conditions: wind from 210 degrees at 11 knots, visibility 10 statue miles, a few clouds at 13,000 feet, temperature 77 degrees Fahrenheit, dew point 43 degrees Fahrenheit, and an altimeter setting of 30.02 inches of mercury.
WRECKAGE AND IMPACT INFORMATION
The airplane wreckage was located at 36 degrees 05.896 minutes north latitude and 95 degrees 48.641 minutes west longitude. The airplane came to rest in a soft dirt field, which was situated adjacent to a residential area and a golf course. The entire aircraft was destroyed by impact and fire damage; however, the all of its components were accounted for at the main impact crater. Both wing leading edges were compressed aft to their main spar. The engine and propeller were embedded in the ground approximately six feet and were later excavated for examination. There were no ground scars noted with the exception of that noted directly below the wreckage. No cockpit instruments, gauges or switch positions could be verified due to impact damage.
Removal of the engine and propeller revealed the propeller remained attached to the engine and neither propeller blade exhibited leading edge damage or face polishing. The propeller blades were bent aft around the engine. Examination of the engine revealed that the engine-driven and electric fuel pumps were separated from their respective mounts and were destroyed. The vacuum pump was separated from its mount and was also destroyed. The right hand oil cooler lower hose was impact separated at the B-nut. The oil line from the left oil cooler to the upper connection of the accessory housing was also separated at the accessory housing end. The oil line from the right oil cooler to the lower accessory housing fitting was separated at the cooler B-nut.
The engine displayed a large hole adjacent to the #6 cylinder. Another puncture was noted above the #4 cylinder near the camshaft position.
The engine was crated and shipped to the manufacturer's facility for further examination.
TESTS AND RESEARCH
On July 15, 2003, the engine was examined at the manufacturer's facility under the supervision of an NTSB investigator. The #6 cylinder exhaust port displayed a black colored build-up on its interior. The #6 piston displayed a burn-through hole on the outer edge (near the exhaust side of the piston). The piston head displayed erosion along its crown on the exhaust side and down the skirt toward the piston pin. The burn-through hole was situated in the oil scraper ring area. The compression and oil control rings were burnt through in this same vicinity. The piston ring gaps were located on the burnt side of the piston. All three rings were eroded at the burn-through location across a 1.5 inch diameter area. Due to the area of concentrated erosion, it was not possible to determine the exact locations of the piston ring gaps. The #6 connecting rod was fractured at the rod cap end and displayed a dark black discoloration and metallic deformation.
All of the crankshaft bearings exhibited evidence of oil starvation and extensive thermal damage. The oil pump was found intact but metallic deposits were noted within the pump gears. The oil sump contained metallic debris and residual oil, which was black in color.
All of the cylinder barrels were nitrided and displayed heavy rust and corrosion deposits (from first responder fire fighting and storage time). The #2 and #3 cylinder oil return lines were separated. No damage was noted to the rocker arms, valves, and valve springs.
Examination of the fuel nozzles revealed the #1 nozzle was blocked, the #2 was partially blocked, the #3 was clear, the #4 was clear, the #5 was blocked, and the #6 was clear.
MEDICAL AND PATHOLOGICAL INFORMATION
An autopsy was performed by the Office of the Chief Medical Examiner for Oklahoma. According to the autopsy report, the pilot died as a result of blunt force trauma. Toxicological testing, performed by the FAA's Civil Aeromedical Institute of Oklahoma City, Oklahoma, was negative for ethanol or drugs.
According to publications regarding engine performance (7th edition Aircraft Powerplants by Kroes & Wild and Lycoming's Induced Engine Damage publication) there are a number of situations that can manifest themselves to a burn-through (blow-by) condition. Some of the most common situations noted are as follows:
¢ Excessively worn piston rings
¢ Piston ring gap alignment or condition
¢ Piston damage from detonation/pre-ignition
The accident engine was overhauled 245 hours prior to the accident and the remaining piston ring segments did not reveal evidence of excessive wear (with the exception of the blow-by area). The gap placements were found in the same vicinity of the blow-by damage; however, their relative position to each other prior to the blow-by erosion is unknown. Due to the extent of the blow-by erosion of the piston rings, their pre-event gap setting is also unknown.
It is recommended in Aircraft Powerplants that the "joints of the piston rings must be staggered around the circumference of the piston in which they are installed at the time that the piston is installed in the cylinder. This staggering is done to reduce blow-by - that is, to reduce the flow of gases from the combustion chamber past the pistons and into the crankcase. Blow-by is evidenced by the emission of oil vapor and blue smoke from the engine breather."
A pre-ignition situation can be initiated from a number of events, some of which are listed below:
¢ Excessive leaning
¢ Improper fuel octane
¢ Carbon deposits
¢ Improper spark plugs
¢ Sharp edges in combustion chamber
¢ Excessive valve guide clearance resulting in overheated valves
¢ Improper ignition timing (advanced)
It is unknown as to what mixture setting the pilot was utilizing at the time of the event. There was no evidence of improper fuel octane, carbon deposits, improper spark plugs, sharp edges in the combustion chamber, or excessive valve guide clearance. The magnetos were destroyed and the engine-to-magneto timing could not be determined due to the extent of the damage.
Lycoming's publication regarding Induced Engine Damage cited a situation where engine oil has blown by the piston rings (either due to wear or gap alignment), which resulted in a detonation situation due to the octane reduction from the fuel/oil mixture.
In either situation (blow-by from piston ring gap orientation or pre-ignition damage resulting in blow-by), a loss of engine power prior to the total engine failure would have occurred.
It should be noted that in either blow-by situation, the crankcase would have been pressurized resulting in oil being forced out of the breather tube (Aircraft Powerplants). The oil would also have been burned in the #6 cylinder prior to the connecting rod failure.
The airplane was released to the owner's representative on May 22, 2003.