ALTOONA, PA, USA
N2640L
Cessna 310R
While flying at night, about 10,000 feet msl, the flight reported an engine problem, declared an emergency, and requested vectors to the nearest airport for landing. When queried, the pilot stated, '...we got a fire in the right engine.' While diverting, the pilot was unable to maintain altitude (level flight) until the airplane descended to about 1700 feet. The tops of ridges in the area were about 2500 to 2800 feet. Subsequently, about 15 miles from the alternate airport, the airplane hit trees during darkness at an elevation of about 1720 feet and crashed. Examination of the right engine revealed that the last 8 to 12 inches of the right overboard tube had separated circumferentially from the exhaust system. A metallurgical examination of the exhaust stack revealed evidence of fatigue; there were numerous hot gas corrosion cracks that had originated at the interior surface and had propagated through the wall thickness of the stack. There was evidence that a breach of the right exhaust stack allowed hot, high velocity gases to escape and initiate a fire. The Altoon weather was in part: 8,000' scattered, 3 miles visibility with fog and haze.
HISTORY OF FLIGHT On August 16, 1995, about 0148 eastern daylight time, a Cessna 310R, N2640L, registered to Bastille Corporation, was destroyed during a forced landing, near Altoona, Pennsylvania. The airline transport pilot and the commercial pilot were fatally injured. Visual meteorological conditions prevailed. An IFR flight plan had been filed for the flight, which departed Carlisle, Pennsylvania, about 0130. The on demand air taxi flight was being conducted in accordance with Title 14 CFR Part 135. While in cruise flight, en route to Detroit, Michigan, the pilot was in contact with the Cleveland Air Route Control Center, Morgantown Radar Position (MGW-R). The pilot informed the controller at Cleveland that he had an engine problem, declared an emergency and requested a landing at the nearest airport. At 0139:12, the pilot of N2640L (N40L), made initial contact with the MGW-R controller, and reported that he was at an altitude of 10,000 feet mean sea level (msl). The controller acknowledged the transmission, and issued the altimeter setting. The pilot told the MGW-R controller, at 0141:14, that he had to look "at one engine" and was requesting a "lower altitude in a slow descent...back to six thousand...." The controller approved the pilot's request. At 0145:44, the pilot of N40L radioed, "...center two six four zero lima declaring emergency vectors to nearest airport." The controller replied by telling the pilot to "fly heading of 230, [this will] be vectors to Altoona...maintain [altitude] four thousand six hundred." The controller continued to vector the pilot to Altoona; however due to the high terrain, and the low altitude of the airplane, radar contact with the airplane was lost at an altitude of 2400 feet mean sea level (MSL). The controller had to repeat the clearance several more times before the pilot acknowledged. At 0146:57, the controller asked the pilot if he could turn "left" to heading of 200 degrees, and advised him that he was about 15 miles from the Altoona Airport. Fifteen seconds later the controller asked, "...can you maintain altitude," and the pilot answered "that's negative." The controller asked the pilot to "say your altitude" and the pilot replied, at 0148:00, "...we're at uh one point seven [1700] we're maintaining altitude now." The pilot repeated "we need vectors to the nearest airport...." The controller answered that the heading was 210 degrees and that the airport, "...should be twelve o'clock and about twelve miles." The pilot asked the controller "how do you get the lights on there." The controller answered, that they were going through the Flight Service Station (FSS), and "they're going to take care of that for you." The controller asked the pilot the nature of the emergency, and the pilot answered at 0148:53, "...we got a fire in the right engine." There was no further communications with the airplane. At 0152:18, the MGW-D controller, contacted the FSS specialist at Altoona, and said, "we lost him on radar we're not talking to him, we have no idea what happened to him...." The controller further stated that the airplane's last position was about 12 miles north of the airport, and asked that the State Police be notified, and a search started. A search was made by ground and an air, and at approximately 2000 on August 16, 1995, the airplane was found, in a hilly, wooded area. The accident occurred during the hours of darkness approximately 40 degrees, 30 minutes north, and 78 degrees, 20 minutes west. PERSONNEL INFORMATION Information on the pilots is contained in page 3 and Supplement "E" of this report, under First and Second Pilot Information. AIRCRAFT INFORMATION At the time of the accident the maintenance records showed that an annual inspection was completed on July 15, 1995. There was 70 hour of flight time since the annual inspection, and a total airframe time of about 3202. A check of the maintenance records that were supplied by the owner, indicated that Airworthiness Directive (AD) 69-12-03, that requires the installation of a bracket to assure clearance is maintained between the fuel line and other aircraft structure, was not written up as being complied with, at the time of the accident. AD 75-23-08, reference to Cessna turbo-charger exhaust systems, was last complied with on August 4, 1995, at tachometer time 3182.3, 20 hours before the accident (see copy of airframe logbook attached to this report). METEOROLOGICAL INFORMATION The nearest recorded weather station to the accident site was Altoona (AOO), about 12 nautical miles southwest. The AOO weather observation at 0150 was; measured ceiling 8000 scattered, visibility 3 miles, fog and haze, temperature 73, dew point 71, winds calm, altimeter 30.02 inches Hg. MEDICAL AND PATHOLOGICAL INFORMATION Autopsies was performed on both pilots, on August 16, 1995, at the Mercy Hospital, in Altoona, Pennsylvania, by Dr. Harold Cottle. Toxicological tests on both pilots were conducted at the Armed Forces Institute of Pathology, Washington, DC, and revealed, "no drugs or alcohol." WRECKAGE AND IMPACT INFORMATION The airplane impacted in a wooded area approximately 10 miles north of the Altoona Airport, at an elevation of 1720 feet MSL. The tops of the ridges in the area of the accident site were 2500 to 2800 feet. The first impact mark was observed near the top of a tree about 75 to 80 feet above the ground, and in the same vicinity, a section of the right wing was lodged in a tree. The wreckage path extended in a westerly direction for about 345 feet. The airplane was destroyed by impact and fire damage, which rendered all the instruments, and switches unreadable. Impact and fire damage, also prevented the confirmation of flight control continuity. The landing gear actuator was found in the up position, however the right main gear had fallen. The wing flaps were destroyed. The rudder tab was found 15 degrees tab right, the elevator tab was found 11 degrees tab up, and the aileron tab was in the neutral position. Examination of the wreckage revealed that a fuel line, part number 5200106-8, was breached at wing station 85, on the right wing. This location was near the outboard corner of the right engine nacelle, forward of the leading edge wing spar. At the location of the breach, the line was a crossfeed line. There was evidence of fire damage observed near and below the breached area. The fire consumed paint at this location, but not the skin of the airplane. The fuel line was removed from the airplane and shipped to the NTSB Materials Laboratory, Washington, DC, for additional examination. Examination of the engines, at the crash site, revealed that the left engine was separated from the nacelle, and was located about 120 feet southwest of the main wreckage. The engine's nacelle was located with the main wreckage in an area that showed intense ground fire damage. The case mounted alternator, at the right front of the engine was separated from it's mounts. Impact damage was observed on the right hand bank of cylinders, No.1, No.3 and No.5. The propeller had separated from the flange. The propeller governor was about 90% full forward travel. The right engine had also separated from the nacelle, and was found approximately 20 feet northwest of the main wreckage. The alternator had detached from it's mounts. The left hand bank of cylinders No.2, No.4, and No.6 displayed impact damage. The propeller had separated from the flange. TEST AND RESEARCH The engines and propellers were removed from the crash site, and taken to the Altoona Airport for examination. Disassembly and examination of the left engine, fuel manifold, revealed fuel in the unit, and no discrepancies were noted. The engine was hoisted and rotated by hand. Compression was noted on all 6 cylinders, and both magnetos produced a spark through the ignition leads when the engine was rotated. The engine driven fuel pump had sustained impact damage and was destroyed. The fuel pump's drive shaft had sheared, and one piece was observed, the other pieces was missing. The fuel control unit (mixture control) had separated from the engine, and had been recovered separately. The unit displayed fire damage. The screen was removed and was observed to be burnt, but otherwise clean. Examination of the left engine revealed no discrepancies. Disassembly and examination of the right engine, fuel manifold, revealed fuel in the unit and no discrepancies were noted. The screen was found clean. Both magnetos were found detached from their respective mounts. Both magnetos were rotated by hand. The right hand magneto produced spark when rotated, and the left hand magneto did not generate a spark. The engine was hoisted and rotated by hand, compression was noted on all 6 cylinders. The engine driven fuel pump was removed and rotated by hand. No discrepancies were observed. Examination of the right engine revealed no discrepancies. The lower part of the right engine nacelle was retrieved from the crash site and examined. The right hand engine nacelle did not display evidence of an in-flight fire. The left engine turbocharger displayed fire damage, and had been found at the crash site in the area of most intense ground fire. The waste gate was closed and the heat damage restricted rotation. The right turbocharger waste gate was 75 percent closed and rotated freely by hand. Examination of the propellers revealed that the left propeller's blades were lose in the hub. The spinner was observed to be crushed in a clockwise direction. The right propellers blades were loose in the hub, and their position, as related to feather, could not be determined. The spinner did not display any impact damage. Two fuel lines, P/N 5200106-8, from the outboard right wing, and the clamps, were shipped to the NTSB Materials Laboratory in Washington, DC, for further examination. The examination revealed, a separation in the line that brings fuel from the left main tip tank to the right fuel selector. The separation in the fuel line was adjacent to a clamp position. The rubber material between the clamp and the line was not present, and was missing when the part was examined at the crash site. There were 2 clamps holding the fuel line. One clamp had the rubber material, and held line tight at one end of the separation. The weight of the line caused the separation to gape open as the melting range was reached. The clamp with the missing rubber, did not hold the fuel line tight and it was free to move within the clamp. When the line was opened there was no way to stop the fuel from flowing out of the line. According to the NTSB Materials Laboratory's factual report, the separation was in the form of a "Z" shaped crack, with a "1.5 inch longitudinal portion and shorter (0.4 inch to 0.5 inch) circumferential legs on each end of the longitudinal portion." The axis of the fuel line on one side of the split was parallel to, but offset from the axis on the other side of the split. The offset was consistent with the deformation in the line in the area of separation. The surface of the line adjacent to the separation was blistered and wrinkled. According to the NTSB Materials Laboratory's factual report, the blistering and wrinkling was "...as if the material in this area had been exposed to temperatures at or near the melting range of the aluminum alloy of the line...bubbles of previously molten aluminum were noted adjacent to the longitudinal portion of the separation." Visual examination of the separation surfaces revealed a "bright irregular surface." There was no evidence found of any "preexisting fracture areas," and "no portion" of the separation appeared "discolored". In addition, there was no ballooning deformation found to the line in the area of the separation, and no indication that there was any pressure in the area of separation. On December 28, 1995, the wreckage was reviewed at Alphine Aviation, Hagerstown, Maryland, under the supervision of the FAA. It was determined that the right engine, turbocharger overboard exhaust stacks displayed several welded areas on the left exhaust duct. The complete exhaust tube was attached to the turbocharger. The last 8 to 12 inches of the right overboard tube was missing. Smoke and heat damage was observed in the right wing battery box area. The left and right engine exhaust stacks were taken to the NTSB Materials Laboratory in Washington, DC, for further examination. Both the left and right overboard exhaust stacks were examined at the NTSB Materials Laboratory, and the Metallurgist's Factual Report is enclosed with this report. According to the factual report, the left exhaust stack was sent for comparison purposes and contained several weld-repair patches. The right stack was examined in more detail and showed that it had separated circumferentially, and was cut off from the remaining portion of the stack to facilitate further examination. Examination revealed that the interior surface of the right stack was covered with dark scale, light loose deposits, and was slightly rough. Areas on the inside surface of the right stack had a "crazed pattern" of cracks. Many of these cracks had penetrated the wall thickness and were visible on the outside surface of the stack. Portions of the fracture had propagated along the toe of the weld. According to the Metallurgist's Factual Report, the weld appeared to be an "original assembly weld" as it extended for the entire length of the submitted section of the right stack and had no visible evidence of repair. Both fractures were covered with heavy accumulation of corrosion products and/or high temperature oxides. Magnified examination revealed areas of relatively flat fractures containing ratchet marks (steps on the fracture surface created by fatigue cracks) "typical of fatigue." The fatigue features "emanated" from numerous origins located at the interior surface of the stack. The areas of the fracture adjacent to the exterior surface of the stack contained a shear lip "typical of an overstress separation." Examination under a scanning electron microscope (SEM) revealed that after extensive cleaning, the fracture feature in many areas were still obscured by deposits. The fatigue cracking initiated from numerous origin areas located at the exterior surface of the stack and propagated a short distance through the wall thickness. Examination at higher SEM magnifications revealed fine fatigue striations in the fatigue fracture region. Metallographic examination reveled "severe" grain boundary corrosion and/or oxidation at the interior surfaces of the stack, in the area located at and adjacent to the weld heat affected zone. Some evidence of intergranular corrosion/oxidation was also noted at the exterior surface of the sack. The cracks initiated at the interior surface of the stack, were wide opened and filled with oxides and corrosion products. The stack material adjacent to the crack faces were also subject to corrosion/oxidation. As a result of the laboratory examination it was determined that the right exhausts stack contained numerous hot gas corrosion cracks that originated at the interior surface, and propagated all the way through the wall thickness of the stack. The breach of the right exhaust stack allowed hot, high velocity gases to escape, and initiate a fire. ADDITIONAL INFORMATION The airplane was released to Mr. John Cooley, representing the owner's insurance company, on August 18, 1995. The crossfeed fuel line was returned to Mr. Cooley, after completion of the laboratory examination on or about November 1, 1995. The exhaust stacks were returned to Mr. Cooley on January 21, 1997.
propagation of corrosion cracks in the right engine overboard exhaust stack and fatigue failure of the exhaust stack, which resulted in escape of hot/high velocity gases, in-flight fire, emergency descent, and subsequent collision with trees during an approach for a forced landing. Darkness and mountainous/hilly terrain were related factors.
Source: NTSB Aviation Accident Database
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