Smyrna, TN, USA
N310JR
CESSNA 310R
Shortly after departure, the airplane entered a rapid, full-power, near-vertical descent from about 2,700 feet above ground level to ground impact. The elevator trim actuator was found in the full tab-up or airplane nose-down position after the accident. The flight was the second flight of the day and was the fourth in a series of maintenance acceptance flights after the installation of a new avionics suite and a new autopilot system. Before the accident flight, all of the features of the autopilot system tested satisfactorily on the ground but did not yet function as designed in flight, as the airplane demonstrated a pitch-porpoise tendency when the altitude hold feature was engaged. According to the technician who performed the installation and troubleshooting work on the airplane, he had accompanied the pilot on the first flight that day and had spoken to an autopilot manufacturing representative upon their return. Another troubleshooting procedure was performed, the technician left for lunch, and the pilot departed alone on the accident flight. When describing a previous test flight, the technician stated that the pilot worked the yoke against the autopilot, and, in response, the autopilot ran the elevator trim to the full nose-down position. The pilot responded by swiping both panel-mounted master switches to the off position (autopilot on/off switch and the trim on/off switch) then attempting to trim the airplane with the electric trim that he had just disabled. According to the technician, the pilot yelled at him to turn the system off, and the technician responded that it was off. He said that the pilot’s actions scared him and demonstrated to him that the pilot really didn't have control of the airplane. He noted that, "After the flight, I told [the pilot] he needed to go back and get in the books and learn to operate the system. He seemed very disoriented with the new technology on this flight and previous flights." Based on the available evidence, it is likely that, after autopilot engagement, the airplane pitched down as a first action of the pitch porpoise, which may have still existed as a discrepancy in the autopilot operation. In response to the downward movement of the airplane, the pilot likely pulled back on the yoke in an effort to arrest the airplane's descent. As a result, the autopilot would have commanded the trim further toward the nose-down position. Such a scenario would require a greater and ever-increasing physical effort by the pilot to overcome the growing aerodynamic force that would result from the nose-down pitch and increasing speed of the airplane. The pilot may have removed one hand from the yoke to again reach for the panel-mounted trim and/or autopilot master switches. With that action, discounting any physical problem, he may have lost his single-handed grip on the control yoke, and the airplane descended in an unrecoverable nose-down attitude.
HISTORY OF FLIGHT On March 11, 2011, about 1343 central standard time, a Cessna 310R, N310JR, was substantially damaged during a collision with flat terrain following an uncontrolled descent after takeoff from Symrna/Rutherford County Airport (MQY), Symrna, Tennessee. The certificated commercial pilot was fatally injured. Visual meteorological conditions prevailed and no flight plan was filed for the test flight which was conducted under the provisions of 14 Code of Federal Regulations Part 91. A review of radar data provided by the Federal Aviation Administration (FAA) revealed that the radar target identified as the accident airplane was tracked for about two minutes of flight. The airplane departed MQY on a southerly heading and climbed to an altitude of 3,200 feet mean sea level (msl). The radar track showed two targets at 3,200 feet, a target at 3,100 feet, and then a target displayed at 2,700 feet. After that, no further targets were displayed. The targets were displayed at 6-second intervals, and the last few targets were almost directly over the crash site. Several witnesses provided written statements, and all described a nose-down, vertical descent to ground contact. Witnesses described the engine sound as "Full throttle," "wide open," "really loud," and "never let up on [the] throttle." Others said the engine was "puttering" or "quit" before the descent. One said he thought the airplane was a "meteorite." According to the airplane's owner, the flight was one in a series of maintenance acceptance flights after the installation of a new avionics suite and a new autopilot system. All of the features of the system tested satisfactorily on the ground, but did not yet function as designed in flight. According to the technician who performed the installation and troubleshooting work on the airplane, the accident flight was the second flight of the day, and the fourth in the series. He accompanied the pilot on the first flight that day, and had spoken to an autopilot manufacturing representative upon their return. Another troubleshooting procedure was performed, the technician left for lunch, and the pilot departed on his own. PERSONNEL INFORMATION According to FAA records, the pilot held a commercial pilot certificate with ratings for airplane single-engine land, multiengine land and instrument airplane. The pilot's most recent FAA second-class medical certificate was issued on January 12, 2011, with the limitation "must wear corrective lenses." He reported 13,000 total hours of flight experience on that date. The pilot's logbooks were not recovered; therefore, the entire scope of his experience could not be determined. AIRCRAFT INFORMATION According to FAA records, an airworthiness certificate was issued for the airplane in 1994. According to recent maintenance records, the airplane had accrued 5,515.5 total aircraft hours. The most recent annual inspection was completed June 19, 2010, at 5,439.1 total aircraft hours. In an interview, the avionics technician who had worked on the accident airplane said that he had completed an avionics installation, including “glass panel” flight instruments and a digital autopilot, on January 25, 2011. After the installation, a test flight was conducted by the accident pilot and the airplane was observed to "porpoise" when the altitude hold or vertical speed modes were engaged. Troubleshooting was conducted which included the installation of a new autopilot computer, as well as a second test flight on March 3, 2011. Ground testing of the unit produced satisfactory results prior to the test flight. During the March 3, 2011 test flight, after engaging the altitude hold mode the airplane descended and the accident pilot pulled back on the yoke. At that time, the pilot turned off the autopilot and electric trim using the master switches installed on the instrument panel. The pilot instructed the avionics technician who had accompanied the pilot on the flight to turn the autopilot off because he could no longer maintain altitude. The technician informed the pilot that he, the pilot, had already disabled both the autopilot and the electric trim. The pilot then manually trimmed the airplane and the flight returned to the airport. At the end of the test flight the technician requested the accident pilot read the manuals provided with the equipment before any more flights were conducted. The altitude hold feature of the autopilot was placarded as "INOP" and the airplane was released to the owner. According to the owner, later that day, he and the accident pilot flew the airplane from Tupelo, Mississippi, to Jackson, Mississippi. He said, "We were flying, heading and NAV modes worked fine, but when altitude hold was engaged, the nose pitched down and the rate of descent was aggressive and about 1,000 feet per minute." When the airplane nosed over, the pilot disengaged "something" but the owner could not recall what feature was disengaged. Additional maintenance was conducted and on the morning of the accident, the accident pilot and technician again performed an unsuccessful test flight. After landing, the technician contacted the autopilot manufacturer who instructed him to disconnect the flap compensation potentiometer (Flap Position Sensor) which he did. The autopilot manufacturer also shipped a pressure transducer (a component used by the autopilot for altitude functions) the day of the accident. The technician informed the accident pilot of this information and stated he wanted to wait until the pressure transducer arrived and was installed before conducting another flight. The accident pilot said he wanted to fly the airplane. The technician then went to lunch and the pilot departed on the accident flight. When asked specifically about the March 3, 2011 test flight, the technician stated, "We took off, climbed to 3,000 feet, engaged the altitude hold, and he wanted to work the yoke back and forth, and he had run the trim all the way nose down. We started in a decline, and instead of hitting the disconnect, he hit the two master switches down, auto-pilot on/off switch and the trim on/off switch. When he did that, he disabled the trim button, and while we were descending, he was trying to trim the airplane with the [button] disabled. The pilot yelled at me, 'turn [the system] off' and I told him, 'It is off.' It just said to me, and scared me, that he really didn't have control of the airplane. Once he realized the configuration of the airplane, he trimmed the airplane manually. He was not supposed to hit those switches; he was supposed to hit the autopilot disconnect button. Had he done that, the trim switches still would have functioned properly. After the flight, I told him he needed to go back and get in the books, and learn to operate the system. He seemed very disoriented with the new technology on this flight and previous flights. " An FAA airworthiness inspector (Avionics) reviewed the Pilot's Operation Handbook (POH), the Service Manual, and spoke with a field service engineer at the autopilot manufacturer with regards to the autopilot installed in the accident airplane. The POH described four ways to disable the autopilot system in the event of a failure or emergency. The POH also outlined two ways to disable the elevator trim. A pilot familiar with the POH would have the ability to disconnect, disable or interrupt the autopilot system using one of the four methods outlined, and still operate the elevator trim electronically. Review of the service manual and discussion with the field service engineer also revealed that a disconnected Flap Position Sensor would not create any operational anomaly and should not have created an uncontrollable condition for the autopilot. The service engineer concurred that if, in-flight, the pilot was to pull back on the yoke with the autopilot engaged, the trim would run toward the nose down direction, which would only add to the control effort required to overcome a pitch down condition. Based on industry standard for trim speed (approximately 20 seconds from a full down position to a full up position), about 12 seconds would elapse as the trim ran from a climb position to a full nose-down position. Previous Damage On or about October 10, 2010, the pilot taxied the airplane through a drainage ditch, which resulted in a left propeller strike and sudden stoppage of the left engine. The damage was reported as minor at the time, and therefore the Safety Board did not conduct an investigation into the event. A review of maintenance records revealed extensive repairs to the airframe and various lifting surfaces, as well as removal and inspection of the left engine and propeller assemblies. METEOROLOGICAL INFORMATION At 1356, the weather reported at MQY, 4 nautical miles to the north of the accident site, included clear skies, and 10 miles visibility. The wind was from 290 degrees at 9 knots, the temperature was 14 degrees C, the dew point was -3 degrees C and the altimeter setting was 30.18 inches of mercury. WRECKAGE AND IMPACT INFORMATION The wreckage was examined at the accident site on March 12, 2011. There was a strong odor of fuel, and all major components were accounted for at the scene. The airplane struck the ground 90 degrees nose down, on a level field of mowed grass, and was almost entirely contained inside the initial impact crater. Only fragments of sheet metal, plexiglass, and individual instruments and radios were found outside the crater. The impact crater was limited to the outline of the airplane, and was consistent with a vertical descent. The airplane was excavated from the impact crater with two backhoe earth-moving machines. During extraction, control cable continuity was established from the flight control surfaces, to their respective cable breaks, and ultimately to the cockpit area. All cable, pulley, and bellcrank separations were consistent with overload. The elevator trim tab actuator was measured, and the measurement was consistent with a full "tab up" position or aircraft nose down. The cockpit and cabin areas were completely destroyed by impact, and only the dual tachometer and the fuel gauge were readable, as they were ejected from the instrument panel. The flap setting could not be determined, and the landing gear was in the up and locked position. The left engine was recovered from 7 feet below the surface, and the right engine was recovered from about 10 feet below the surface. The propeller blades from the two 3-bladed systems were recovered, and all 6 blades displayed similar twisting, bending, leading-edge gouging and chordwise scratching. Two propeller blades from the right engine were broken. One was broken at the tip, and the other was broken outboard of the blade root. The fractures were consistent with overload. Several gallons of fuel poured from each wing as they were extracted from the crater. Examination of the engines revealed that they were both significantly damaged by impact, and that neither could be rotated at the crankshaft or through the accessory section. The oil pump housing covers from each engine were removed, and examination revealed rotational scoring on each cover. The fuel pumps were partially separated from their mounts, and their driveshafts were fractured. The fractures were consistent with overload. Both pumps contained fuel, and were absent of water and debris. All four magnetos were separated from their mounts, and were destroyed by impact. MEDICAL AND PATHOLOGICAL INFORMATION The Office of the Medical Examiner for the State of Tennessee performed the autopsy on the pilot. The cause of death was attributed to multiple blunt force injuries. Toxicological testing for the pilot was performed by the FAA’s Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma. Test results were negative for drugs or alcohol.
The pilot's improper response to a known autopilot pitch divergence anomaly. Contributing to the accident was the pilot's decision to perform a test flight on a system for which he lacked a complete working knowledge.
Source: NTSB Aviation Accident Database
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