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On May 18, 2012, about 1620 eastern daylight time, a Cessna 195A, N9859A, was substantially damaged during landing rollout, following a precautionary landing after a loss of oil pressure, in Tipton, Pennsylvania. The flight departed Old Bridge Airport (3N6), Old Bridge, New Jersey destined for Zelienople Municipal Airport (PJC), Zelienople, Pennsylvania. The certificated commercial rated pilot was uninjured. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight conducted under 14 Code of Federal Regulations Part 91.
According to the pilot, during cruise flight enroute to PJC, at 6,500 feet above mean sea level, the pilot noticed that the engine rpm (revolutions per minute) began fluctuating by approximately 100 rpm, followed about 20 seconds later by a drop in rpm from the cruise setting of 2,000 rpm to 1,700 rpm
The pilot immediately looked at the oil pressure gauge and observed that it was "reading zero". He then declared an emergency with air traffic control and was informed that the nearest airport was 15 miles to the south of his location.
To try and keep the engine from seizing he brought the engine back to idle, in case he would need power later to avoid terrain and set the propeller to low rpm.
The terrain in the area was primarily mountain ridges with hills and narrow valleys and the pilot realized that there were few safe landing areas and he doubted that he could make it to the nearest airport.
He kept looking for a suitable landing area and finally saw an industrial park in a valley between ridge lines which looked like an airport and had minimal automobile traffic.
He later discovered that it had been Peterson Memorial Airport and it had closed in 1974 however, half of the old runway still remained as a road (Park Avenue) that was oriented in a 090 and 270 degree configuration.
He elected to land into the wind which was coming from an easterly direction. The approach was steep due to the surrounding terrain and he extended the wing flaps and entered a forward slip to lose altitude. Once the airplane touched down on the road he applied maximum braking after the tail wheel was on the pavement and stayed on the centerline of the road. During the landing rollout, the airplane's left wing struck a standpipe, but the airplane continued to roll until nosing over and coming to rest at an approximate 60 degree nose down angle, 75 feet beyond the east end of the road.
According to Federal Aviation Administration (FAA) and pilot records, the pilot held a commercial pilot certificate with ratings for airplane single-engine land and instrument airplane. His most recent FAA second-class medical certificate was issued on August 10, 2011. He reported 1495.9 total hours of flight experience with 77.3 total hours in the accident airplane make and model.
The accident aircraft was a high wing, four place, single engine, fixed gear, tail wheel equipped airplane of conventional metal construction. It was powered by a 275 horsepower, Jacobs R-755-B2, 7- cylinder radial engine.
According to FAA and airplane maintenance records, the airplane was manufactured in 1950. The airplane's most recent annual inspection was completed on April 18, 2012. At the time of the inspection, the airplane had accrued approximately 4,524 total hours of operation, and the engine had accrued approximately 370 total hours of operation since major overhaul.
The 2053 recorded weather observation at Altoona-Blair County Airport (AOO), Altoona, Pennsylvania, located 8 nautical miles southwest of the accident site, included wind variable 6 knots, 10 miles visibility, clear, temperature 23 C, dew point 5 C, and an altimeter setting of 30.15 inches of mercury.
WRECKAGE AND IMPACT INFORMATION
Post accident examination of the airplane by a Federal Aviation Administration inspector revealed that the airplane had incurred substantial damage to the left wing, left main landing gear and left horizontal stabilizer. Further examination revealed that a 1/2 inch metal oil line was fractured.
TESTS AND RESEARCH
The Jacobs R-755-B2 engine in the airplane featured a magnesium alloy crankcase, steel cylinders, aluminum cylinder heads, aluminum pistons, and sodium –filled exhaust valves.
The oil system which fed lubricating oil to the engine consisted of a 5-gallon cylindrical oil supply tank, oil shut off valve oil strainer, pressure oil pump, scavenger oil pump, oil cooler, oil pressure gauge, and oil temperature gauge.
Oil would flow from the oil supply tank through the shut off valve and oil strainer to the oil pressure pump where it was forced through the engine. Oil would then return to the oil supply tank through the oil cooler by the scavenger oil pump.
Examination of the Fractured Metal Tube
Examination of the fractured metal tube revealed that it was the rocker scavenge oil tube, part number 4426A, which was located at the lowest point of the engine's valve lubrication system between cylinders No. 4 and No. 5 and acted as a return (scavenge) tube for oil that drained from the rocker assemblies. Further examination revealed that it had failed in fatigue in the manufactured bend adjacent to the coupling sleeve and nut. It was made of type "N" copper tubing that became available in 1943 and which by 1979 was no longer commercially available, indicating that the tubing was at least 34 years old and had probably been re-used many times, not necessarily on the original engine.
The oil tube assembly displayed a distinctive bend and compression at the bead end and a slight bend at the nut end that were not specified on the manufacturer's drawings, consistent with the oil tube assembly being significantly bent to fit on the engine. The manufactured bends displayed an oval cross-section, also not specified or noted in the drawings which may have been produced by the original manufacturing process or by bending at each re-use which would initiate bending fatigue. Cracks propagated from the fracture face at the centerline of the tube, which was also the larger dimension of the oval cross-section.
Grooves found on the straight section of tubing adjacent to the end also indicated that the tubing had been rubbing on an adjacent component and would have eventually worn through.
Hardness testing also revealed that the tubing at the fractured bend was slightly harder than a sample of tubing that had not been subjected to any bending, and it exceeded the specified maximum hardness. The increased hardness of the tubing in the bend may have been produced by the original manufacturing process and/or any subsequent manipulation (work hardening) which would have increased the fatigue strength of the tube.
Copper Fuel and Oil Tubing Failure
Work hardening, also known as strain hardening, or cold working, is the strengthening of a metal such as copper by plastic deformation. This strengthening occurs because of dislocation movements and dislocation generation within the crystal structure of the material.
On February 19, 2008, the Civil Aviation Safety Authority of Australia (CASA), released an air worthiness bulletin (AWB 28-007) regarding fatigue failures of copper alloy fuel and oil pipes which was prompted by eight service difficulty reports on various airplane models which had been received by CASA. The bulletin stated in part that work hardening of parts could be caused by normal engine vibration over extended periods of time, maintenance mishandling damage, including kinking and re-bending of pipes during maintenance, as well as over tightening during installation.
Review of information provided by the International Cessna 195 club also revealed 11 instances of copper tubing failures.
Research into copper fuel and oil tube failures indicated that, in order to alleviate work hardening, common practice at one time was to anneal copper tubing, by heating it to a prescribed temperature, and then holding the tubing at that specified temperature for a specified length of time, and then cooling it back to room temperature to relieve internal stresses, soften the copper, make it more ductile, and refine the grain structure, before re-installation.
Research also revealed that the United States Air Force had published a Technical Order (01-125CAA-21) which required copper oil scavenge lines to be replaced with stainless steel lines on LC-126A, B, and C, airplanes (military versions of the Cessna 195) to minimize the use of copper tubing on the airplane.
Review of FAA Advisory Circular (AC) 43.13-1B, Acceptable Methods, Techniques, and Practices-Aircraft Inspection and Repair revealed that guidance regarding annealing of copper tubing was not included. Review of FAA-H-8083, Aviation Maintenance Technician Handbook also revealed that it discussed the concept of annealing of materials but, it did not specify a procedure for annealing copper tubing.
As a result of this investigation, in order to improve safety, the type certificate holder for the Jacobs Engine took the following actions:
1. Recommended that within the next 25 hours of operation, to inspect the copper oil drain lines for signs of leakage, cracks, or other damage, and replace as necessary with new FAA approved replacement parts available from the type certificate holder.
2. Recommended that each line be inspected for signs of chafing, deformation of cross-section, or other unacceptable condition, and to pay close attention to tubing bend areas and the beaded end of the tube.
3. Recommended thereafter to inspect annually or every 100 hours, whichever occurs first until factory new replacement parts are installed and that field fabricated replacement tubes should be replaced with factory new FAA approved replacement parts.
4. Recommended that any drain line be replaced when time in service cannot be verified and that the life of FAA approved replacement parts shall be the same as the overhaul interval for the specific engine model but shall not exceed 1,400 hours under any circumstances, and that drain lines should not be repaired.
5. Forwarded their recommendations to the FAA Aircraft Certification Office (ACO) responsible for Jacobs Engines, for review and approval by the ACO, for inclusion in a Service Bulletin on inspection and replacement of high time copper vent and scavenge lines.