Fletcher, NC, USA
N661PF
RANS S6
The commercial pilot and flight instructor were conducting a flight review. The flight departed from a private grass field airport and maneuvered in the local area for about 20 minutes and then returned to the airport. They then departed again, and shortly after takeoff the airplane's climb rate rapidly increased, airspeed rapidly deteriorated, which was subsequently followed by a descent into terrain. Multiple witnesses described the airplane entering an aerodynamic stall and a subsequent fully developed spin, where the airplane impacted the ground in a nose low attitude. Examination revealed no anomalies with the airframe or engine that would have precluded normal operation, and damage signatures and a witness account indicated that the engine was producing power at the time of the accident. Fuel observed in the carburetor bowls indicated that the engine was receiving fuel normally at the time of impact. The investigation could not determine why airplane control was lost or who was the pilot flying during the flight's final takeoff and climb. Both pilots were certificated flight instructors, and each had logged several thousands of hours of flight time, however, the flight instructor had never flown the accident airplane, and the commercial pilot had logged under 5 hours of flight time in the accident airplane. It is likely that both pilot's inexperience in the accident airplane contributed to the loss of control at low altitude. Although both pilots were at increased risk for a sudden cardiac event, there was no evidence on autopsy of such an event, therefore, it is unlikely either pilot’s cardiovascular disease was a factor in the accident.
HISTORY OF FLIGHTHISTORY OF FLIGHT On June 26, 2019, about 1030 eastern daylight time, an experimental amateur-built Rans S-6S airplane, N661PF, was destroyed when it was involved in an accident near Six Oaks Airport (NC67), Fletcher, North Carolina. The commercial pilot and the flight instructor were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. According to the accident airplane’s owner, the commercial pilot had asked to use the airplane for a flight review. The owner reported that the commercial pilot had flown the airplane the day before the accident and did not report any issues with the airplane. The owner also reported that the airplane was topped off with nonethanol automobile gas the day before the accident. A Garmin 496 GPS device was found at the accident site. Data from the accident flight containing flight track, GPS altitude, time, heading, and ground speed were extracted from the unit. The recorded data began at 0955:25. About 1004, ground speed and GPS altitude data consistent with a takeoff from runway 6 at NC67 were recorded. The flight track then showed the airplane flying about 7 miles northeast of NC67, performing maneuvers, and navigating back to NC67. The flight track showed the airplane completing a series of spiral descending turns, entering the left downwind leg of the traffic pattern, and landing on runway 24 about 1025. At 1026:08, data consistent with another takeoff on runway 6 were recorded. The data revealed that the airplane gained about 500 ft in altitude, climbing northeast, about 57-65 kts ground speed. At 1027:57, the ground speed decreased to 49 kts and then, 7 seconds later, to 10 kts; subsequently, the GPS altitude decreased rapidly. The last data point recorded was at 10:28:38, about 10 ft from the main wreckage site. Figures 1 and 2 depict the airplane's flight track and associated ground speed and altitude during the last takeoff of the flight, respectively. Figure 1: Flight track of the final takeoff during the accident flight Figure 2: Chart of ground speed and altitude for the final takeoff during the accident flight A private pilot-rated witness who was in his truck at a gas station about 1/2 mile from the accident site reported that he observed the airplane “flying erratic[ly].” He subsequently observed the airplane enter two "cascading [aerodynamic] stalls," and the airplane banked right and then left. He stated that the airplane then entered a "classic spin" and completed one-and-a-half turns in the spin before it descended out of his view. A second witness who was jogging along a road located about 550 ft from the accident site reported that the airplane was flying away from the airport, "wavered slightly in midair," descended, and impacted the ground at a "steep angle." He reported that it "sounded like a normal airplane." PERSONNEL INFORMATIONReview of the logbook of the commercial pilot, who also held a flight instructor certificate, revealed that his most recent flight review was completed on June 6, 2017, with a different flight instructor. He had logged a total of 3.3 hours in the accident airplane. Review of the flight instructor's logbooks dating back to the accident airplane's manufacture date (2007) revealed that he had not logged any flights in the airplane. The flight instructor's spouse reported that she believed that the two pilots had not flown together before. METEOROLOGICAL INFORMATIONThe witness in his truck about 1/2 mile from the accident site reported that the wind was from the south, about 7-8 kts, skies were clear, and visibility was unrestricted. The second witness who was jogging closer to the accident site reported that the weather was clear and sunny, with few clouds and no wind. WRECKAGE AND IMPACT INFORMATIONThe initial impact point was located in a flat open pasture about 65 ft from the main wreckage, and the wreckage path was oriented on a 070° heading about 0.72 nautical mile from the runway 24 threshold at NC67. Fragments of propeller and engine cowling were co-located with the initial impact point. The airplane sustained extensive impact damage and came to rest upright on a heading of 245°, partially laying on its right side, with a portion of the left wing elevated above the fuselage. There was no evidence of fire. All major airplane components were accounted for at the accident site. Flight control continuity was established from all flight control surfaces to the cockpit area. The left flap was found retracted, and the right flap was found partially extended. The left-wing fuel tank was found empty, the tank was not breached, and the left fuel cap remained installed tight. When low pressure air was blown through the forward and aft fuel ports, air flowed freely. The right-wing fuel tank was full and the fuel cap was found installed tight. When the forward and aft right tank fuel ports were cut by recovery personnel, fuel flowed freely. A sample of fuel from the right tank appeared unremarkable with no debris observed and tested negative for water. The cockpit section sustained significant impact damage. The two seats remained attached to the airframe. The seatbelts and shoulder harnesses had been cut by first responders. The flap handle was found in the "first notch" (first position from retracted), and the airspeed indicated 0 knots. The g-meter instrument had three indicator needles. The first needle indicated 3/4 positive Gs. The second needle indicated negative 2.5 Gs, and the third needle indicated negative 4 Gs. The throttle lever was found full forward, and the engine choke lever was stowed. All circuit breakers were found in. The trim indicator needle was found in the takeoff position. The ignition switches were both found in the on position by the first responders and were moved to off during their activities. The on/off fuel shutoff valve was found on and was moved to off by the first responders. Low pressure air was blown through the fuel shutoff valve with the valve open, and air flowed freely. The engine remained attached to the firewall and sustained impact damage. During an engine examination, all spark plugs were removed and displayed normal operating and combustion signatures. The left and right carburetors remained intact, and fuel was observed inside their bowls, with no debris observed. The propeller hub contained fragment splinters, as the majority of the two-bladed propeller had splintered off from the propeller hub. The engine started and operated normally during a postaccident engine test run. ADDITIONAL INFORMATIONAccording to the Rans S-6S Coyote II Pilot Operating Handbook (POH), the best angle of climb speed (Vx) was 55 mph indicated airspeed (IAS), and the best rate of climb speed (Vy) was 75 mph IAS. Table 1 is a stall speed chart based on information provided in the POH. Table 1: Aerodynamic stall speeds, with power off, as stated in the POH The POH further stated, in part, that the maximum altitude loss during stall recovery is about 75 ft and noted the following stall characteristics: STALLS: Stalls have a warning buffet due [to] the turbulent air from the wing root flowing over the elevator. The stall occurs with a definite break. Rudder may be needed to hold the wings level. Recovery is quick with the release of back pressure. Turning, accelerated power on and power off stalls all demonstrate the slight buffet and quick recovery. An approved maneuver listed was "Spins up to 3 turns at idle power settings and without flaps only." MEDICAL AND PATHOLOGICAL INFORMATIONCommercial Pilot According to the autopsy report from the Buncombe County (North Carolina) Medical Examiner, Winston-Salem, North Carolina, the commercial pilot’s cause of death was multiple blunt force injuries. The medical examiner reported moderate to severe two-vessel coronary artery atherosclerosis. No other significant natural disease was identified. Toxicology testing performed on the commercial pilot at the Federal Aviation Administration (FAA) Forensic Science Laboratory was negative for carbon monoxide, volatiles, and drugs. Flight Instructor According to the autopsy report from the Buncombe County Medical Examiner, Winston-Salem, North Carolina, the flight instructor’s cause of death was multiple blunt force injuries. The medical examiner reported the flight instructor had cardiomegaly, severe atherosclerosis in the left anterior descending coronary artery, moderate atherosclerosis in his left circumflex coronary artery and right coronary artery, patent three vessel grafts, a 26-centimeter-long sternotomy scar, and a fibrotic scar in his left ventricle indicating a remote heart attack. Toxicology testing performed on the flight instructor at the FAA Forensic Science Laboratory detected the high cholesterol medication rosuvastatin, the high blood pressure medication metoprolol, the heartburn medication famotidine (commonly marketed as Pepcid), and the diabetes medication sitagliptin. All were considered nonimpairing, and sitagliptin taken alone or in combination with metformin is considered acceptable to the FAA because these diabetes medications are not likely to cause low blood sugar. The toxicology test was negative for carbon monoxide.
The exceedance of the airplane's critical angle of attack during climb, which resulted in an aerodynamic stall and spin at low altitude. Contributing was the lack of experience both pilots possessed in the accident airplane.
Source: NTSB Aviation Accident Database
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