Ada, OK, USA
N1971W
Cessna 310Q
The 1,500-hour airline transport rated pilot had just departed a 6,305-foot-long runway when, based on a viewing of security camera footage, a puff of white smoke exiting the back of the right engine shortly after the airplane became airborne. The airplane then began a right turn and flew on a westerly heading at a low altitude before it disappeared behind a tree line. A witness saw the airplane as it was in a right turn toward the north. He thought the airplane was going to land on a closed highway, but the nose of the airplane dropped and the airplane cartwheeled on the grass median west of the road. Examination of the right engine revealed that the crankshaft gear had failed due to a fatigue fracture in one of the teeth. The fatigue emanated from the pressure face of the tooth and intersected another crack emanating from the non-pressure face of the tooth, thereby producing separation of the tooth from the rim. Near the origin, post-fracture damage prevented the ability to determine if the crack initiated in fatigue or if a crack propagated in overstress through the case and then continued propagating through the core in fatigue. Upon completion of the materials examination it was evident that the microstructure of the gear was inadequate and more research into the manufacturing process was required. A review of manufacturing records indicated that approximately 2,400 crankshaft gears were made from the same batch of material as the accident gears, and were heat-treated in two groups. A review of the heat treatment records confirmed that furnace temperatures during the hardening step in each heat-treating process were not high enough to fully austenitize the material. Furthermore, the quantity and orientation of gears loaded in the furnace were greater when compared to other jobs completed for TCM. In addition, initial data from a test load similar to that used in the heat-treating process from the accident serial number gear, indicated that under these conditions, the gears might not have been fully equilibrated at temperature during the hardening step. As a result, TCM manufactured several other gears at different hardnesses and conducted failure testing to see if they could reproduce a similar failure. Even though some of the hardness levels were well below TCM standards, they were unable to produce a similar failure. In addition, there was evidence to suggest that the gear teeth may have been exposed to an excessive load at some point during its operation. The cause of the gear tooth failure could not be determined.
HISTORY OF FLIGHT On July 24, 2005, at 1752 central daylight time, a twin-engine Cessna 310Q airplane, N1971W, was destroyed when it collided with terrain shortly after takeoff from Runway 17 at the Ada Municipal Airport (ADA) near Ada, Oklahoma. The airline transport pilot, the two passengers, and a dog, were fatally injured. The airplane was registered to Stoneair Charter Services, LLC, of Centrahoma, Oklahoma, and was being operated by the pilot. No flight plan was filed for the flight destined for the Cushing Municipal Airport (CUH), near Cushing, Oklahoma. Visual meteorological conditions prevailed for the personal flight conducted under 14 Code of Federal Regulations Part 91. Security cameras were installed and operational at various locations around the Ada Municipal Airport. A review of the images obtained by these cameras revealed that the movement of the airplane was captured during the following phases of flight: preflight, engine starts, taxi toward the runway, take off, and impact. The airplane's engine run-up (if conducted) and take off roll were not captured on video. Between 1751:25 and 1751:30, the airplane appeared on video traveling from left to right just as it began its initial take off climb from Runway 17 (a 6,203-foot-long and 100-foot-wide asphalt runway). The airplane's altitude appeared to be just below the level of the tops of the trees that were located east of the runway. It was during this time that a sudden burst of white-colored smoke was observed coming from behind the right engine. The airplane is then observed entering a right hand turn toward the west with the landing gear extended. Between 1751:30 and 1751:34, the airplane's movement was not recorded by any of the cameras. At 1751:34 to 1751:42, another camera captured the airplane as it flew toward the west at an altitude just above the airport hangars with the landing gear retracted. The airplane then flew out of camera range for approximately 10 seconds. Between 1751:52 and 1752:47, the airplane was then recorded by another camera as it flew toward a tree line located west of the airport before it disappeared behind the trees. Shortly after, a pillar of dark smoke began to appear above the tree line where the airplane was last observed. A witness was standing just to the west of Highway 377, which was under construction and approximately 1 mile west of the Ada Municipal Airport. According to the witness, he did not hear the airplane approaching until it was almost right over him. The airplane was "extremely low," about 60-70 feet above the ground, with the landing gear retracted, in a shallow right turn towards the north. As the airplane crossed over the highway, it made a sharp right turn to the north and the witness thought the pilot was trying to land on the highway. However, as the airplane banked to the right, the nose of the airplane dropped, and the airplane rapidly descended toward the grass median located to the west of the highway. The right wing contacted the ground and the airplane cart wheeled before it came to rest on an embankment and caught on fire. The witness added that he did not see any fire or smoke trailing the airplane while in flight, but he did hear a "miss in the engine." He described the "miss" as a "pop," but not as loud as the sound of a backfire. The witness added that the airplane did not sound as loud as other airplanes do when they depart, and he felt that it was not making the power it needed to maintain altitude. The accident occurred during the hours of daylight approximately 34 degrees, 47 minutes north latitude, and 96 degrees, 41 minutes west longitude. PERSONNEL INFORMATION The pilot held an airline transport pilot certificate with a rating for multi-engine land; a commercial certificate with ratings for airplane single-engine land, multi-engine land and rotorcraft-helicopter; and, a private certificate for airplane single-engine sea. He also held a flight instructor certificate for airplane single-engine land, multi-engine land, instrument airplane, and rotorcraft-helicopter. The pilot's last Federal Aviation Administration (FAA) second-class medical was issued on August 5, 2004. At that time, he reported a total of 1,500 flight hours. The pilot's personal logbook was never located. AIRCRAFT INFORMATION The airplane's last annual inspection was conducted on November 18, 2004, at a total aircraft time of 3,944.7 hours. At that time, the right engine was removed and a factory new engine was installed. The last entry in the airframe logbook was entered on June 28, 2005. At that time, the oil was changed on both engines. The right engine had accrued approximately 175.3 hours since new and the left engine had accrued 510.8 hours since major overhaul. The pilot purchased 20 gallons of 100 LL aviation fuel prior to departure. According to the individual that fueled the airplane, he serviced each main tank with 10 gallons, which filled the tanks to approximately half- to 3/4-full. METEOROLOGICAL INFORMATION Weather reported at Ada Municipal Airport at 1752 was reported as wind from 160 degrees at 10 knots gusting to 18 knots, visibility 10 statue miles, clouds scattered at 6,000 feet, temperature 97 degrees Fahrenheit, dewpoint 66 degrees Fahrenheit, and a barometric pressure setting of 29.97 inches of Mercury. The calculated density altitude was 3,700 feet. WRECKAGE AND IMPACT INFORMATION An on-scene examination of the airplane wreckage was conducted on July 25, 2005. All major components of the airplane were accounted for at the scene. The main wreckage, which included the left wing, left engine, fuselage, tail section, and the inboard portion of the right wing, came to rest upright on a magnetic heading of 280 degrees at a field elevation of approximately 1,016 feet mean sea level (msl). The initial impact was a series of ground scars that began approximately 170 feet south of where the main wreckage came to rest and were aligned on a magnetic heading of 355 degrees. The scars included three sequential impact craters that were approximately 6-7 feet apart. Imbedded in the first impact crater were pieces of engine cowling. In the second crater were sections of Plexiglas, and the left propeller was buried in the third impact crater. Also found scattered beyond these initial scars and along the wreckage path were sections of the right wing, both main (tip) fuel tanks, and the right propeller. The right engine came to rest approximately 20-feet forward of the main wreckage. A post-impact fire consumed the cockpit and fuselage. However, flight control continuity was established for all flight control surfaces to the cockpit. The landing gear was found in the extended position, and the flaps were extended 20 degrees. In addition, the aileron trim was found to be 15 degrees tab down, the elevator trim was 5 degrees tab down, and the rudder trim was extended beyond its normal range. Both fuel selector handles were destroyed in the fire. Both of the left and right fuel selectors were found extended just beyond the "off" position. Both engines were examined on August 17, 2005, at the manufacturing facilities of Teledyne Continental Motors, in Mobile, Alabama, under the supervision of the Safety Board. Examination of the right engine revealed it sustained impact damage. When the accessories were removed from the rear of engine, metal particles were found in the oil located on the interior walls of the accessory portals. It was also noted that several camshaft gear teeth were broken, ground down, and/or missing. This was also true for the crankshaft gears and to some of the associated accessory gears. Due to the damaged gears, the engine was not rotated so timing and continuity could not be verified. Examination of the crankshaft gear revealed that 7 teeth were completely sheared, followed by partial shearing of approximately 14 teeth. The other teeth remained intact. Six of the 7 missing teeth were located; and several partially ground teeth were located in the oil sump; as well as numerous other pieces of metal shavings and flecks. The idler gear teeth and the camshaft exhibited rounding of the teeth, and the damage appeared to be secondary. The number 1, 3, 4, 5, and 6 exhaust push rods were fractured at the spring, but none of the intakes exhibited similar damage. The top of each piston-exhibited uniform impact marks from the intake and exhaust valves. The spark plugs were removed. The top plugs were dry and appeared light gray in color. The bottom plugs (no. 1,3,5) were oil soaked and some of them contained pieces of metal shavings. Bottom plugs (no. 2,4,6), were dry and appeared light gray in color. The left and right magnetos were placed on a test bench and spark was produced at all leads. The vacuum pump remained attached to engine, but the cover plate had separated and some of the vanes had broken and were missing. The fuel pump was removed and the coupling was intact. The fuel/air unit sustained impact damage and the throttle linkage had to be replaced for the unit to be bench tested. The fuel manifold valve was intact, but lines were twisted. The inlet fitting on the number 1 nozzle line was missing. Examination of the left engine revealed it sustained impact and fire damage. Engine and valve train continuity was established via manual rotation of the propeller flange. The spark plugs were removed and appeared light gray in color. The number 1, 3, 5, bottom plugs were oil soaked, and the number 5 top plug was oil soaked. Both magnetos were bench tested and spark was produced at all ignition leads. The vacuum pump was intact, but could not be rotated due to heat damage. The fuel pump, fuel manifold, lines and ends were intact. No mechanical deficiencies were noted. Both propellers were examined at McCauley Propeller Systems facilities, near Wichita, Kansas, on October 18-19, 2005, under the supervision of the Safety Board. Examination of the left propeller revealed that the left blade retention nut top surfaces contained impact marks, which were consistent with the propeller blades being at or near low pitch angle at the time of impact. Additionally, the pitch change mechanism was found at or near the low pitch-to-latch position. Both blades exhibited minimal damage, which was consistent with impact at low power. Examination of the right propeller revealed that is was feathered at the time of impact. Damage to the propeller blades was limited to decreased pitch twisting on the no. 2 blade. The blade exhibited scratches and paint burnishing near the tip of the blade that was not consistent with rotation. The no. 1 blade was undamaged. MEDICAL AND PATHOLOGICAL INFORMATION The Office of the Chief Medical Examiner, Oklahoma City, Oklahoma, performed an autopsy on the pilot on July 25, 2005. The cause of death was determined as "multiple injuries." The FAA Toxicological Research Laboratory, of Oklahoma City, Oklahoma, conducted toxicological testing on the pilot. The tests were negative for alcohol, cyanide, carbon monoxide and illegal drugs. TESTS AND RESEARCH Examination of the right engine revealed that several gear teeth had separated from the crankshaft gear. The crankshaft gear and separated teeth were examined at the Safety Board's Materials Laboratory, in Washington, DC. Examination of the components revealed the crankshaft gear failed due to a fatigue fracture in one of the teeth. The fatigue emanated from the pressure face of the tooth and intersected another crack emanating from the non-pressure face of the tooth, thereby producing separation of the tooth from the rim. Near the origin, post-fracture damage prevented the ability to determine if the crack initiated in fatigue or if a crack propagated in overstress through the case and then continued propagating through the core in fatigue. Upon completion of the materials examination it was evident that the microstructure of the gear was inadequate and more research into the manufacturing process was required. A review of manufacturing records indicated that approximately 2,400 crankshaft gears were made from the same batch of material as the accident gears, and were heat-treated in two groups. A review of the heat treatment records confirmed that furnace temperatures during the hardening step in each heat-treating process were not high enough to fully austenitize the material. Furthermore, the quantity and orientation of gears loaded in the furnace were greater when compared to other outsourced jobs completed for TCM. In addition, initial data from a test load similar to that used in the heat-treating process from the accident serial number gear, indicated that under these conditions, the gears might not have been fully equilibrated at temperature during the hardening step. As a result, TCM manufactured several other gears at different hardnesses and conducted failure testing to see if they could reproduce a similar failure. Even though some of the hardness levels were well below TCM standards, they were unable to produce a similar failure. The cause of the gear teeth failure could not be determined. ADDITIONAL INFORMATION A handheld Garmin GPSmap 295 receiver was found in the wreckage and sent to the manufacturer for examination; however, the unit sustained extensive thermal damage and data could not be retrieved. Emergency Procedures According to the Cessna 310Q Owner's Manual, pages 3-1 to 3-2, Engine Inoperative Procedures, it stated: Engine Failure During Takeoff-Speed below 105 MPH IAS with sufficient runway remaining, the procedures were: (1) Throttles- CLOSE immediately (2) Brakes- AS REQUIRED Engine Failure After Takeoff -Speed above 105 MPH IAS (Without Sufficient Runway Ahead) (1) Mixture-AS REQUIRED for altitude (2) Propellers- FULL FORWARD (3) Throttles-FULL FORWARD (4) Landing gear-UP (5) Determine inoperative engine (idle engine same side as idle foot). (6) Inoperative Engine: a. Throttle-Close b. Mixture-IDLE CUT-OFF c. Propeller-FEATHER (7) Establish Bank-5 degrees toward operative engine (8) Climb to Clear Obstacle- 105 MPH IAS (9) Climb at Best Single-Engine Climb Speed-116 IAS (10) Wings Flaps-UP (if extended) in small increments (11) 'Trim Tabs-Adjust 5 degrees toward operative engine (12) Inoperative Engine-SECURE a. Fuel Selector-OFF b. Auxiliary Fuel Pump-OFF c. Magneto Switches-OFF d. Alternator Switch-OFF (13) As soon as Practical- LAND In addition, the manual stated, "The most critical time for an engine-out condition in a multi-engine aircraft is during a two or three second period late in the takeoff run while the aircraft is accelerating to a safe engine-failure speed." "MINIMUM SINGLE ENGINE CONTROL SPEED. The twin-engine aircraft must reach the minimum control speed (86 MPH IAS) before full control deflections can counteract the adverse rolling and yawing tendencies associated with one engine inoperative and full power operation on the other engine. This speed is indicated by a Red radial line on the airspeed indicator." RECOMMENDED SAFE SINGLE ENGINE SPEED. Although the aircraft is controllable at the minimum control speed, the aircraft performance is so far below optimum that continued flight near the ground is improbable. A more suitable recommended safe single-engine speed is 105 MPH IAS since at this speed, altitude can be maintained more easily while the landing gear is being retracted and the propeller is being feathered. Performance Data A review of published performance data revealed that the airplane would have required approximately 3,400 feet of runway distance to clear a 50-foot-tall obstacle with only one engine operating. The single-engine climb performance would have been approximately 250 feet per minute. This data was based on meteorological conditions that were similar to the conditions that existed on the day of the accident (1,000 foot elevation, temperature 100 degrees Fahrenheit, and a gross weight of 4,900 pounds). Wreckage Release The airplane wreckage was released to a representative of the owner's insurance company on September 12, 2006.
The loss of engine power as a result of a fatigue fracture in one of the crankshaft gear teeth for undetermined reasons. Also causal was the pilot's failure to maintain control of the twin-engine airplane after the power loss, which resulted in an inadvertent stall and subsequent collision with terrain.
Source: NTSB Aviation Accident Database
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