SALINAS, CA, USA
N8158M
Cessna 182P
During a night-time flight in marginal VFR conditions, the pilot radioed approach control that his aircraft's engine had begun running rough, losing power, and he was having difficulty maintaining altitude. Approach control vectored the pilot 14 miles back to the airport where he had previously completed an instrument approach. The pilot reported the runway in sight, however, the aircraft crashed on final approach 2 miles from the runway. A witness reported hearing the aircraft's engine as it approached, followed by 5 seconds of silence, and then the sound of impact. An annual inspection was completed on the aircraft about 2 weeks before the accident and this was believed to be the owner's first flight after the inspection. During the inspection, the Nos. 1, 3, and 4 cylinders were removed from the engine and repaired. Postaccident examination of the engine revealed that one of the two valve keepers had not been reinstalled on the No. 3 cylinder exhaust valve resulting in asymmetric loading of the remaining keeper. When that keeper fractured, the exhaust valve was released and entered the combustion chamber of the No. 3 cylinder where it contacted the piston. The consequential damage fractured the Nos. 3 and 4 pistons, the Nos. 3 and 4 connecting rods, and the crankcase.
HISTORY OF FLIGHT On January 9, 1998, at 1756 hours Pacific standard time, a Cessna 182P, N8158M, impacted a power transmission pole and a greenhouse 2 miles southeast of the Salinas, California, airport during a night emergency landing approach. The aircraft was destroyed and the private pilot was fatally injured. Visual meteorological conditions prevailed for the personal flight, which was operated by the owner under the provisions of 14 CFR Part 91. The flight departed from San Carlos, California, about 1730, on an instrument flight plan; however, the pilot had canceled the flight plan before the accident. According to the Federal Aviation Administration (FAA) Western Region Quality Assurance Office, the pilot completed an instrument approach to Salinas without landing and departed the Class D airspace under special VFR flight rules, destined for the Chalone Vineyard private airport 21 miles east. When 14 miles southeast of Salinas, the pilot contacted Monterey TRACON and reported that the aircraft's engine was running rough, losing power, and he was having difficulty maintaining altitude. The pilot was being radar vectored back to Salinas at the time of the accident and he had reported the airport in sight. On-scene examination of the aircraft's engine revealed a hole in the top of the crankcase and internal damage to the Nos. 3 and 4 pistons and connecting rods. There was additional damage in the No. 3 cylinder rocker box cover. A witness who observed the accident from the second story bedroom of his home, which is approximately 200 feet east of the accident site, reported that he saw the aircraft briefly before the initial impact. He saw a white and a green light that were unusually low for aircraft approaching the airport. As he watched there was a flash, then a trail of fire on the ground, and then an explosion and large fire in the far end of an adjacent greenhouse. Another witness, who resides in a mobile home immediately adjacent to the power transmission pole that the aircraft first struck, reported that he heard the engine of the aircraft as it approached. There was silence for about 5 seconds, then he heard the initial impact with the pole outside his home. He said that it was very dark under cloudy skies outside his house, and that the only lights in the area were those inside his home and another nearby residence. The owner of the property where the accident occurred reported that he and several of his employees rushed to the accident scene and used approximately 10 portable fire extinguishers to put out the largest fire which was in the cabin area of the aircraft. They essentially had the fire extinguished when the fire department arrived. He said that it was very dark outside because the lights inside the greenhouses do not come on until 10:00 PM. PERSONNEL INFORMATION The pilot's logbook was not located after the accident. On an insurance application dated March 11, 1996, the pilot reported total flying time of 4,000 hours with 250 hours in the previous 12 months and 60 hours in the previous 90 days. The application reported that the pilot had 2,000 hours in the Cessna 182 make and model aircraft. On his medical examination application, dated 02/20/97, the pilot reported 4,500 total flying hours, and 100 hours in the prior 6 months. AIRCRAFT INFORMATION According to the pilot's brother, the aircraft logbooks were carried in a seat pouch in the aircraft. The seats, except for the frames, were consumed by fire and the logbooks were not located. FAA inspectors located records of a recent annual inspection performed on the aircraft by an area repair station. Among the records was shop work order 11074 dated November 19, 1997. The work order shows aircraft hours of 1,377.4 and includes, among other service items, an annual inspection and the removal, repair, and reinstallation of the Nos. 1, 3, and 4 cylinders due to low compression. An "Invoice for Services" for work order number 11074 shows that the work was completed on January 6, 1998. Representatives of the repair station, Victor Aviation Services, Inc. of Palo Alto, California, stated however, that the January 6 date was the date the invoice was prepared and that the work had been completed in mid-December. The repair station produced a copy of a logbook page showing the work performed during the inspection and repair and an approval for return to service (signoff) dated December 12, 1997. Following the annual inspection and engine repair, the aircraft was flown twice by Victor Aviation personnel; once for a maintenance check flight, and a second time to return the aircraft to the owner at San Carlos. The pilot's brother thought that the accident flight was the first flight of the aircraft by the owner since completion of the annual inspection. WRECKAGE AND IMPACT INFORMATION The aircraft impacted the perimeter of a complex of greenhouses in a level agricultural area. The wreckage was distributed along an approximate 135-foot-long path oriented approximately 300 degrees (magnetic). In the area to the left (southwest) of the wreckage path was an open, uncultivated field, and to the right (northeast) was the complex of several large greenhouses. The wreckage path was in line with a row of electrical power transmission lines, which supplied electrical power to the greenhouses. The poles supporting the lines are approximately 12 inches in diameter and 30 feet tall, and the open span between poles is approximately 120 feet. The accident site is at latitude 36 degrees 37.812 minutes north, and longitude 121 degrees 34.152 minutes west (GPS). From the accident site, the bearing and distance to the Salinas airport are 303 degrees magnetic and 2.68 miles (GPS). Adjacent to a mobile home at the southeast end of the wreckage path, there were burn marks and freshly exposed wood approximately 20 feet above ground level on a power transmission pole. Several power transmission lines were on the ground on both sides of this pole. Near the base of this pole was the root portion of the right-hand wing, the right-hand flap (separated at midspan) and the right-hand wing strut. The fuel cell in the inboard wing section was ruptured and the adjacent skins exhibited black sooting. To the left of the wreckage path in the next 50 feet was an area of widely scattered pieces from the right-hand main landing gear wheel fairing. Approximately 90 feet past the first power pole, the outboard section of the right wing hung suspended from the one remaining power transmission line, approximately 15 above the ground. The aileron was suspended from the power line by an aileron cable. In the upper skin of the wing was a spanwise tear in the skin which ran from the root to the area where the aileron cable exited. The white paint of the wing exhibited black sooting. Approximately 30 feet further along the wreckage path was the next power pole in the row which had freshly exposed wood approximately 4 feet above ground level. Beyond (northwest) the second power pole, approximately 15 feet and 10 feet right of the wreckage path centerline, was the fuselage with the empennage tail surfaces and the left wing. The left wing was on the ground oriented with the root end to the northwest and the tip to the southeast. The fuselage was on top of the left wing and was inverted. The fuselage was oriented with the engine and propeller to the northwest and the empennage to the southeast. The cabin section of the fuselage was destroyed by fire, as was a portion of the empennage. The engine, propeller, and nose landing gear were not involved in the fire. The cockpit instruments and switches were destroyed by fire. The engine tachometer and manifold pressure gauges were identified with their respective needles resting against the stops at the low end of their scales. The operating hour recording drums of the tachometer instrument were destroyed by fire and were unreadable. The throttle, propeller, and mixture controls were in the full forward position. The flight control cables were severed to the right and left wing and were continuous to the empennage control surfaces. The engine control continuity was verified. The fuel selector valve was damaged by fire and rotated freely. The valve was opened and there was no visible restriction to flow. The propeller blades were bent aft approximately 45 degrees with long, smooth bends. There was no leading edge damage and no chordwise striations. When the engine was uncowled and lifted (inverted) there was a hole approximately 6 inches in diameter in the upper crankcase inboard of the No. 4 cylinder base. A broken connecting rod and piston pin fell out of the hole. The rod was intact at the piston pin end but the rod cap at the crankshaft journal end was absent. In the connecting rod, one cap bolt was absent and the other exhibited bending near where it broke. Viewed inside the crankcase through the hole, the Nos. 3 and 4 connecting rods were absent from their respective crankshaft journals. The journals were bright and shiny. The valve cover of the No. 3 cylinder was broken open creating a 2-inch diameter hole and the exhaust valve spring retainer/rotocoil and rocker arm were visible at the opening. The intake manifold coupling serving the left-hand bank of cylinders (2,4,6) was separated at the rear of the No. 2 cylinder where it connects to the lateral manifold tube. The engine was disassembled by the Safety Board at the facilities of Teledyne Continental Motors in Mobile, Alabama on January 29, 1998. When the rocker box cover was removed from the No. 3 cylinder, the rocker arms, pushrods, and the stem end of the intake valve were intact. The No. 3 exhaust valve and valve guide were absent and pieces of the exhaust valve guide were present in the cover. Approximately the bottom 1/3 of one exhaust valve retainer key/keeper was also present in the cover. The exhaust valve spring retainer/rotocoil was found lodged over the valve end of the exhaust valve rocker arm and the exhaust valve springs were in the spring recess. When removed from the rocker arm, the spring retainer/rotocoil inner race was cracked and there was a corresponding scar on the lower surface of the rocker arm where the retainer/rotocoil had been found. The springs had assumed a permanent curved shape of approximately 15 degrees. Pieces of the exhaust valve guide from within the cylinder head that were present in the rocker box cover did not exhibit any longitudinal striations on the external surfaces. The exhaust valve stem, minus the valve head, was found in the No. 3 cylinder exhaust port and was bent approximately 90 degrees. Viewed from the side, the stem tip exhibited a mushroomed appearance. The keeper recess lands on the stem exhibited impact marks over approximately 1/2 the circumference of the recess and the lower land of the recess was rounded over the entire circumference. The stem tip exhibited multiple impact marks. The fragment of the exhaust valve retainer key/keeper found in the rocker box cover, when compared to an exemplar retainer key, was dimensionally similar to the portion of the retainer key that extends below the spring retainer/rotocoil collar, and also exhibited a wear shoulder on the exterior surface that was not present on the exemplar part. The head of the exhaust valve, separated from the stem on the backside of the head, was found embedded into the inside wall of the crankcase at the base of the No. 4 cylinder at the 3 o'clock position. The interior surface of the No. 3 cylinder combustion chamber exhibited a hammered appearance and approximately 1/3 of the intake valve head was broken off. The broken segment of the intake valve was found in the exhaust port of the No. 5 cylinder. The No. 3 piston was absent and was found at various locations in the engine, mostly the engine sump, typically in 1-inch size pieces. A portion of the No. 4 piston was present in the bore of the No. 4 cylinder. The piston was separated at the piston pin and the skirt of the piston was absent. The Nos. 3 and 4 connecting rods were separated from the crankshaft and the rods and their associated piston pins were loose in the crankcase. The piston pinhole and bushing in both connecting rods were intact, although both rods exhibited hammering damage. The rod caps were separated from both rods. The No. 3 rod was bent and twisted and was broken in the strap area. One cap bolt hole was round, the other cap hole was elongated, and the cap was flattened. The No. 4 rod was straight and the cap was not located. One rod bolt, severed at the parting surface, was peened into position on the rod. The other hole was open and elongated. The interior of the crankcase in the area of the Nos. 3 and 4 rod journals exhibited hammering. The hydraulic lifter housing area of the No. 3 cylinder was broken out, as was the top of the crankcase above the base of the No. 4 cylinder. The crankshaft main bearings and rod bearings on the undamaged journals exhibited a uniform gray appearance and were unscored. The Nos. 1, 2, 5 and 6 cylinders, connecting rods, and crankshaft throws were mechanically continuous, as were the accessory case gears. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was performed on the pilot by the Monterey County Sheriff-Coroner, and a toxicological analysis was performed by the FAA Civil Aeromedical Institute, Oklahoma City, Oklahoma. The results were negative for alcohol and all screened drug substances with the exception of Tetrahydrocannabinol Carboxylic Acid (Marihuana), which was present in the blood at a level of 0.002 ug/mL, and in the urine at a level of 0.013 ug/mL. TESTS AND RESEARCH On May 15, 1998, Teledyne Continental Motors (TCM) issued a "TCM Critical Service Bulletin CSB98-1" notifying operators and service organizations that some exhaust valves had been manufactured between January 1, 1996 and March 31, 1998, which, in service, exhibited signatures indicative of improper heat treatment of the stem tip during manufacture. The bulletin was revised to CSB98-1B on June 1, 1998. In conversations with the repair station (Victor Aviation) which repaired the Nos. 1, 3, and 4 cylinders in December 1997, it was determined that the exhaust valves installed at that time were among those effected by the service bulletin. According to TCM, the specification for the exhaust valve requires that, during manufacture, the stem tip be induction hardened to a depth of 0.06 inches at a minimum value of 50 on the Rockwell "C" scale. On December 14, 1998, the Safety Board tested two exhaust valves from the accident engine at the facilities of Seal Laboratories, El Segundo, California. The two valves were the (undamaged) No. 1 valve, and the No. 3 valve. The laboratory found that the mean hardness of the No. 1 valve stem tip was 57.3 on the "C" scale, while the mean hardness of the No. 3 valve was 33.9. The Seal Laboratory report is attached. The Safety Board's Materials Laboratory in Washington, D.C. examined the two valves following the testing at Seal Laboratories. The Safety Board Laboratory's factual report is also attached. ADDITIONAL INFORMATION The aircraft wreckage was released to U.S. Aviation Underwriters on February 12, 1998.
A loss of engine power due to a missing valve keeper. Also causal was the failure by engine maintenance personnel during engine top overhaul to install the second valve keeper in the No. 3 cylinder exhaust valve and the failure of inspection personnel to detect the improper assembly.
Source: NTSB Aviation Accident Database
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