Gasport, NY, USA
N508CT
FLIGHT DESIGN GMBH CT-SW 2006
The private pilot was taking off in the light sport airplane for a local flight. Witnesses reported seeing the pilot begin the takeoff. During the rotation, the airplane appeared to pitch up higher than normal, followed by up-and-down pitch oscillations and left bank oscillations; it climbed no higher than about 75 ft. The airplane began a slow left bank, which was not consistent with a normal takeoff procedure, before impacting trees south of the runway in a left-wing-low attitude. The pilot indicated to his son before he died that the airplane experienced flight control issues related to the autopilot. Postaccident examination of the airplane revealed that the flaps were symmetrically extended 15 degrees, and there was no evidence of preimpact failure or malfunction of the flight controls for roll, pitch, or yaw. According to an airplane performance study, the pilot was operating the airplane about 4 knots above its stall speed during the left turn; however, the location of the main wreckage with respect to the airplane's last GPS data point indicated that the bank angle likely increased and exceeded the airplane's critical angle-of-attack, which resulted in an aerodynamic stall. Data from the engine's recording device indicated that, during the beginning portion of the takeoff sequence while the airplane was over the runway, the engine rpm decreased about 50 rpm and then increased nearly 900 rpm about the point and time when the airplane banked left and hit the trees. Postaccident operational testing of the engine revealed that it produced full-rated power with no evidence of preimpact failure or malfunction. The reason for the reduced power setting at takeoff could not be determined. Although the pilot reported that the pitch-and-roll oscillations during takeoff were related to the autopilot, it could not be determined during examination of the autopilot whether the autopilot was engaged during the accident flight. Postaccident testing of the autopilot controller and roll servo revealed no evidence of preimpact failure or malfunction; the override torque value of the roll servo was within limits. The autopilot controller minimum airspeed was found set to a value of 0, which would have disabled the minimum airspeed alert if the autopilot were engaged. The pitch servo was found inoperative due to a failed voltage regulator; however, this condition would not have caused any increased torque or servo runaway. Following replacement of the failed component, the pitch servo tested satisfactorily, and the override value was within limits. Therefore, if the autopilot had been engaged and an autopilot malfunction had occurred, the pilot would have been able to override any pitch and yaw servo commands. Further, if the autopilot had been engaged and the controller minimum airspeed had been set to an appropriate value, it is likely that a stall alert would have occurred that provided the pilot with adequate time to respond to and avert an aerodynamic stall.
HISTORY OF FLIGHT On July 5, 2014, about 1104 eastern daylight time, a Flight Design GMBH CT-SW 2006, N508CT, collided with trees then the ground shortly after takeoff from Royalton Airport, Gasport, New York. The private rated pilot, the sole occupant was fatally injured, and the airplane was substantially damaged. The airplane was registered to and operated by a private individual under the provisions of 14 Code of Federal Regulations (CFR) Part 91 as a personal, local flight. Visual meteorological conditions prevailed at the time and no flight plan was filed. The flight was originating at the time of the occurrence. According to Federal Aviation Administration (FAA) personnel, witnesses reported the pilot performed an engine run-up at the approach end of runway 7, then back taxied down the runway where he turned around and initiated takeoff from runway 25. At rotation the airplane appeared to pitch up higher than normal followed by up and down pitch oscillations and left bank oscillations, climbing no higher than approximately 75 feet. The airplane also began a slow bank to the left, before impacting trees south of the runway in a left wing low attitude. The airplane came to rest nearly inverted on an easterly heading in a heavily wooded area. Witnesses called 911 to report the accident and the pilot was rescued and transported to a hospital, where he died on July 16, 2014. PERSONNEL INFORMATION The pilot, age 78, held an airline transport pilot certificate with rating(s) airplane multi-engine land; at the airline transport pilot level he held type ratings in B727 and DC-9. He held a commercial pilot certificate with rotorcraft helicopter, and instrument helicopter ratings; at the commercial level he was type rated in a SK-58. He also held a private pilot certificate with airplane single engine land rating, and held flight engineer certificate with turbojet and turboprop ratings. He held a third class medical certificate with a limitation to have available glasses for near vision on May 24, 2011. On the application for the last medical certificate he listed a total time of 30,225 hours, and his weight was listed as 222 pounds. There were no records of previous accidents or incidents or FAA enforcement actions. A review of the pilot's pilot logbook from September 12, 2012, to the last entry dated May 21, 2014, revealed he logged 20 flights in the airplane totaling 34.5 hours. The first flight of September 17, 2012, was associated with the date he purchased the airplane and was logged as dual received and also as pilot-in-command (PIC). The remainder of the flights were only logged as PIC. AIRCRAFT INFORMATION The airplane was manufactured in 2006 by Flight Design GmbH, as model CT-SW 2006, and was designated serial number 06-10-06. It was powered by a Rotax 912 ULS carbureted engine rated for 5 minutes maximum at 100 horsepower at 5,800 rpm, or 95 horsepower maximum continuous performance at 5,500 rpm. It was equipped with a fixed pitch propeller. Review of the maintenance records revealed the airplane was last inspected in accordance with an annual inspection that was signed off on June 24, 2014. The airframe logbook entry indicated in part that the autopilot computer was overhauled at the factory, and an invoice provided by the pilot's son indicated the inoperative roll servo was removed and a loaner roll servo was installed and rigged. The airplane total time at that time was reported to be 317.1 hours. Excerpts from the airframe maintenance records are contained in the NTSB public docket. According to the mechanic who performed the last annual inspection, following installation of the overhauled autopilot computer and loaner roll servo, he test flew the airplane twice totaling about 1.2 hours. During both flights he operated the autopilot later reporting no discrepancies with the system including the loaner roll servo. METEOROLOGICAL INFORMATION A surface observation weather report taken at Buffalo Niagara International Airport (BUF), Buffalo, New York, at 1054, or approximately 10 minutes before the accident indicates the wind was from 260 degrees at 8 knots, the visibility was 10 statute miles, and few clouds existed at 25,000 feet. The temperature and dew point were 22 and 09 degrees Celsius respectively, and the altimeter setting was 30.25 inches of Mercury (inHg). The accident site was located about 16 nautical miles and 28 degrees from BUF. AIRPORT INFORMATION The Royalton Airport is a public-use airplane equipped with a single runway designated 7/25; the airport elevation is 628 feet. The asphalt runway is 2,530 feet long and 35 feet wide. FLIGHT RECORDERS The airplane was equipped with a Rotax Flydat engine recording device that recorded and retained engine data associated with time, exhaust gas temperature, pressure, engine rpm, water temperature and oil temperature. The airplane was also equipped with a Garmin 396 GPS. Both devices were removed from the airplane and sent to the NTSB Vehicle Recorder Laboratory located in Washington, D.C. The Flydat was subsequently hand carried by a NTSB investigator to Rotax's facility in British Columbia, for readout. The data was provided to a NTSB specialist in Washington, D.C. The GPS was read-out by the NTSB specialist located in Washington, DC. According to the NTSB specialist's factual report, correlation of the data recorded by the FLYdat and the GPS data was performed which resulted in an error of plus or minus 3 seconds. Based on the GPS data, the groundspeed began to increase between 1104:02, and 1104:10. The airplane accelerated to 32 knots groundspeed while maintaining runway heading at 1104:19. The next data point 1 second later, while over the runway, indicates the airplane had accelerated to 39 knots groundspeed, the altitude was 6 feet higher, and the heading had changed over 5 degrees to the left. Five seconds later, or at 1104:25, the airplane was over trees south of the runway, had attained the maximum recorded groundspeed value of 41 knots, the altitude was recorded to be 679 feet, and the heading was recorded to be 207.5 degrees. Plotting on a map of GPS data and correlation of the FLYdat and GPS data revealed that during the takeoff while over the runway, the engine rpm increased to 3,230 rpm, and remained at that value for about 5 seconds. The rpm dropped about 50 rpm, then increased to the maximum recorded value of 4,590 rpm at 1104:32, which was the last FLYdat data point. The last valid in-flight data point from the GPS was determined to be at 1104:25. Review of FLYdat data for the previous flight revealed that during takeoff, the engine rpm sharply increased to about 5,000, and remained at the value until being reduced. A report from the NTSB specialist regarding the FLYdat and GPS, and the data downloaded from the FLYdat and GPS are contained in the NTSB public docket. WRECKAGE AND IMPACT INFORMATION The airplane crashed in a heavily wooded area south of the runway and came to rest nearly inverted on a nearly due east heading at 43 degrees 10.87 minutes North latitude and 078 degrees 33.41 minutes West longitude. That location when plotted was located about 180 feet south of the southern edge of the runway, and 242 feet and 133 degrees from the last GPS in-flight target. Following recovery of the airplane, it was inspected by representatives of the FAA along with a representative of the airframe manufacturer. The examination determined that the flaps were symmetrically extended 15 degrees, which equated to the flap selector. The ballistic parachute was not deployed, and inspection of the flight controls for roll, pitch, and yaw revealed no evidence of preimpact failure or malfunction. Examination of the cockpit revealed the choke was off, the throttle was full forward, and the brake was off. The ballistic parachute activation safety pin remained in place in the activation handle. The airspeed indicator was near 0. The on-board FLYdat engine monitor and Garmin 396 GPS receiver were retained and sent to the NTSB Vehicle Recorder Division for read-out. Following recovery of the airplane, examination of the engine was performed by a representative of the engine manufacturer with FAA oversight. The inspection revealed crankshaft, camshaft and valve train continuity was confirmed; compression was noted in all cylinders. During hand rotation of the engine, no unusual sounds were noted coming from the gearbox. Impact damage was noted to the radiator, but coolant was noted in the expansion tank. The carburetor bowls were removed and corrosion was noted inside. The engine was shipped to a facility for an attempted engine run. Operational testing of the engine was performed with FAA oversight; a calibrated test club propeller pitched for 5,600 rpm was installed. In preparation for the engine run, the oil tank was replaced in order to avoid possible contamination and the muffler was replaced because it was crushed. The engine was placed on a test stand with no additional work performed, and the oil system was then purged of air in advance of the attempted engine run. While priming the fuel system, a slight fuel leak was noted in a location between the fuel pump and carburetor. The engine was started and operated to 5,600 rpm remaining at that setting for about 2 minutes. The magnetos checked good and the engine was operated using the ignition system components installed at the time of the accident. During the engine run the oil pressure and oil temperature were within limits and no discrepancies were noted. The engine was secured, and then operated a 2nd time with no discrepancies noted. A copy of the report from the engine manufacturer representative is contained in the NTSB public docket. Examination of the three bladed propeller revealed all blades were fractured at varying lengths. MEDICAL AND PATHOLOGICAL INFORMATION The pilot was reported by his son to be in good health on the day of the accident; the pilot died while hospitalized on July 16, 2014, or 11 days after the accident; therefore, a postmortem examination was not performed. Approximately 6cc's of blood taken upon hospital admittance was obtained from the hospital by the medical examiner and that sample was sent to the FAA Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma. The toxicology report stated that testing for carbon monoxide and cyanide was not performed, and the results were negative for volatiles and tested drugs. TESTS AND RESEARCH Examination of the autopilot system components consisting of the computer, pitch and roll servos was performed at the manufacturer's facility with FAA oversight. According to the report, it was not possible to determine whether the autopilot system was engaged at the time of the accident. The autopilot controller which is also a flight instrument was inspected and the display was centered and correct, which indicates that either it was unpowered during the accident, or the autopilot remained powered and functional after the accident. The manufacturer reported the display would have required less than 30 seconds of power for the display to re-zero. After power application the settings were consistent with what would be expected for the accident airplane. It was noted that the minimum airspeed was set to a value of zero, which disabled an alert of a low airspeed situation. The autopilot was tested to the standards of a new unit and no issues were noted. Further examination of the autopilot system components consisting of the roll servo revealed the safety shear pin which by design will shear in the event of motor corrosion or gear jam was determined to have been properly installed and not sheared. The motor was tested and capable of 34.5 inch pounds of torque. The torque enhancer was impact damaged and could not be tested. The gears were inspected and were free of foreign objects or foreign object damage (FOD). Upon connection to the test equipment, the servo operated correctly, and the output torque and override torque values were within specification. Inspection of the pitch servo revealed the safety shear pin which by design will shear in the event of motor corrosion or gear jam was determined to have been properly installed and not sheared. The motor is capable of approximately 45 inch pounds of torque. Attempts to operationally test the pitch servo revealed it was not operational; this was attributed to be from a failed voltage regulator. The manufacturer reported it could not be determined if the failed voltage regulator was pre-accident or the result of the accident sequence. The manufacturer also indicated the failure of the voltage regulator could not cause any increased torque or servo runaway. The safety shear which by design will shear in the event of motor corrosion or gear jam was determined to have been properly installed and not sheared. The failed voltage regulator was replaced, and the pitch servo was tested and found to operate correctly and was capable of 40 inch pounds of torque. The output torque and override torque values were within specification. The gears were inspected and were free of foreign objects or foreign object damage (FOD). A copy of the report from the manufacturer and FAA concurring statement are contained in the NTSB public docket. ADDITIONAL INFORMATION/DATA Pilot's Account The pilot's son reported in writing that during one visit with his father 3 days after the accident following removal of the breathing tube, he asked his father if he was aware what had occurred and he said yes, he had crashed. The son asked his father if he wanted to talk about it and he nodded his head yes. Aware that witnesses had observed the airplane roll to the left three times, corrected, and then pitch up and roll to the left, he asked his father if there was a flight control issue. His father said yes and nodded his head up and down strongly. He then asked his father if he thought the flight control issue was related to the autopilot and he said yes and again nodded his head up and down strongly. A statement from the son is contained in the NTSB public docket. Weight and Balance Weight and balance calculations were performed using the empty weight of the airplane (715 pounds), and the weight of the pilot per his last medical examination (222 pounds). Since the fuel load at the time of the accident could not be determined, for calculation purposes the fuel tank in each wing was considered to be full, resulting in a total usable fuel capacity of 33.0 gallons. Based on a fuel weight of approximately 6 pounds per gallon, the fuel weight was calculated to be 198 pounds. The empty weight at the moment of engine start was calculated to be 1,135 pounds, which was approximately 188 pounds less than the specified maximum takeoff weight (MTOW) of 1323 pounds. Performance Information According to the NTSB Performance Study, the aircraft's true airspeed (TAS) for the last GPS points was approximately 46 knots. Assuming that the aircraft's flight path between the last three GPS points was part of a smooth coordinated turn, the radius of that turn was calculated to be 368 feet. Based on the aircraft's TAS of 46 knots and radius of 368 feet, the necessary bank was calculated to be about 27 degrees for the lift to balance the centripedal force of the turn and keep the airplane aloft. Additionally, the study indicates that the near 30 degrees of bank needed to maneuver between the last GPS points correlates to the airplane flying about 4 knots above the stall speed. Based on the wreckage being located on an easterly track 230 feet from the final GPS location, assuming a single banked turn, the aircraft's bank angle would have had to increase beyond the 27 degrees and the aircraft's stall speed would have continued to increase. A copy of the Performance Study and information from the airplane manufacturer regarding stall speeds are contained in the NTSB public docket.
The pilot's failure to maintain adequate airspeed following a left turn during takeoff, which led to the airplane exceeding its critical angle-of-attack and experiencing an aerodynamic stall.
Source: NTSB Aviation Accident Database
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