N13372North American AT-6C · 1956

On June 4, 2014, about 1530 Pacific daylight time, a North American AT-6C, N13372, was substantially damaged when it impacted trees and terrain following a loss of engine power near South Prairie Airport (02WA), Buckley, Washington. The airplane was registered to and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. The airline transport rated pilot, who was seated in the front seat, and the airline transport pilot rated passenger who was seated in the aft seat, were fatally injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight. The flight originated from 02WA about 2 minutes prior to the accident.

Family members of both the pilot and passenger reported to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) that the airplane had recently been sold to the pilot by the passenger, and the flight was part of a local checkout flight. Family members further reported that the pilot and passenger had conducted a local flight earlier in the day of the accident, which lasted about 1 to 1.5 hours before they had returned for lunch.

Multiple witnesses located in the vicinity of the departure airport and accident site reported observing the airplane takeoff from runway 34, and the engine sounded normal. About 15 to 30 seconds after the airplane had passed the departure end of the runway, witnesses heard the engine begin to "sputter." Witnesses stated that they continued to observe the airplane initiate a right turn to an easterly heading followed by a left 270-degree turn while ascending and descending erratically. Witnesses further stated that throughout the turn, the engine seemed to have been powering up and losing power shortly thereafter. As the airplane completed the turn to a southerly heading towards the departure airport, the engine lost complete power, and the airplane descended into trees.

Review of a 24-second recorded video provided by a witness was reviewed by the NTSB IIC. The video showed the accident airplane depart runway 34, and continued in an ascent until the video ended as the airplane passed over the departure end of the runway. Throughout the entire video, the airplane appeared to be operating normally with no evidence of smoke originating from the engine or any engine abnormalities.

It was not determined which one of the two pilots, an airline transport rated pilot seated in the front seat, or an airline transport rated pilot seated in the aft seat, was manipulating the flight controls when the accident occurred.

Front Seat Pilot / New Owner

The pilot, age 62, held an airline transport pilot certificate with airplane multiengine land and airplane single-engine land ratings. The pilot also held a flight instructor certificate with single-engine and multiengine ratings. A first-class airman medical certificate was issued to the pilot on August 10, 2012, with the limitations stated "must wear corrective lenses." The pilot reported on his most recent medical certificate application that he had accumulated 26,250 total hours of flight time. Review of the pilot's logbooks revealed that the most recent logbook entry was dated June 4, 2014, which was for 0.7 hours in the accident airplane. Further review revealed that the pilot had logged 19.1 hours within the previous 90 days and 8.3 hours within the previous 30 days.

Rear Seat Pilot / Former Owner

The rear seat pilot, age 72, held an airline transport pilot certificate with airplane multiengine land and airplane single-engine land, and rotorcraft helicopter ratings. A third-class airman medical certificate was issued to the rear seat pilot on July 23, 2013, with the limitations stated "must wear corrective lenses, not valid for any class after." The rear seat pilot reported on his most recent medical certificate application that he had accumulated 24,660 total hours of flight time. Review of the pilot's logbooks revealed no entries since his most recent biennial flight review dated April 25, 2013.

The two-seat, low-wing, retractable-gear tailwheel equipped airplane, serial number (S/N) 88-13372, was powered by a Pratt & Whitney R-1340-AN engine, serial number ZP-101599, rated at 550 horsepower. The airplane was also equipped with a Hamilton Standard variable pitch propeller. The airplane was equipped with dual flight controls, which allowed for persons in either the forward or aft seats to fly the airplane. However, the airplane is typically flown from the front seat due to the landing gear position handle location. The airplane featured two 55.2 gallon fuel tanks, located on both sides of the wing center section. The left fuel tank was equipped with two different fuel delivery ports, which allows for two fuel selector positions, left main, placarded at 35.2 gallons, and the reserve position, placarded at 20 gallons.

Review of the Flight Operation Instruction Chart revealed that an hourly fuel burn varies from 26 gallons per hour at sea level with power settings of 1,600 rpm and 26 inches of manifold pressure and the mixture in a lean setting to 65 gallons per hour at a power setting of 2,250 rpm and 36 inches of manifold pressure and the mixture in a rich setting. Maximum continuous power settings of 2,200 rpm, 32.5 inches of manifold pressure, and the mixture in a rich position result in a fuel burn of about 51 gallons per hour.

The family of the former owner reported that the airplane had 30 to 35 gallons of fuel per side and 31 gallons of fuel was added the day prior to the accident according to fuel logs.

Information provided by a family member of the former owner, revealed that about 1 to 1.5 years prior to the accident, a new fuel selector valve was installed by a mechanic, and since then, the airplane had not flown much. The family member further stated that initially there were two fuel selector valves replaced, as the initial replacement did not operate as expected. In addition, they reported that the airplane did not fly much since the fuel selector valve replacement; however, numerous ground runs were conducted.

Review of the airframe, engine, and propeller logbooks revealed that the most recent annual inspection was conducted on November 12, 2013, at a HOBBS time of 976.7 hours. A fuel selector valve was installed on August 31, 2012, at HOBBS time of 975.4 hours. At the time of the accident, the airplane had accumulated 2 hours since the annual inspection and 3.3 hours since the fuel selector valve was replaced.

A review of recorded data from the Joint base Lewis-McChord Airport, Tacoma, Washington, automated weather observation station, located about 16 miles west of the accident site, revealed at 1523 conditions were wind from 270 at 8 knots, visibility 10 statute miles, scattered clouds at 2,300 feet, temperature 18 degrees Celsius, dew point 11 degrees Celsius, and an altimeter setting of 30.13 inches of mercury.

The two-seat, low-wing, retractable-gear tailwheel equipped airplane, serial number (S/N) 88-13372, was powered by a Pratt & Whitney R-1340-AN engine, serial number ZP-101599, rated at 550 horsepower. The airplane was also equipped with a Hamilton Standard variable pitch propeller. The airplane was equipped with dual flight controls, which allowed for persons in either the forward or aft seats to fly the airplane. However, the airplane is typically flown from the front seat due to the landing gear position handle location. The airplane featured two 55.2 gallon fuel tanks, located on both sides of the wing center section. The left fuel tank was equipped with two different fuel delivery ports, which allows for two fuel selector positions, left main, placarded at 35.2 gallons, and the reserve position, placarded at 20 gallons.

Review of the Flight Operation Instruction Chart revealed that an hourly fuel burn varies from 26 gallons per hour at sea level with power settings of 1,600 rpm and 26 inches of manifold pressure and the mixture in a lean setting to 65 gallons per hour at a power setting of 2,250 rpm and 36 inches of manifold pressure and the mixture in a rich setting. Maximum continuous power settings of 2,200 rpm, 32.5 inches of manifold pressure, and the mixture in a rich position result in a fuel burn of about 51 gallons per hour.

The family of the former owner reported that the airplane had 30 to 35 gallons of fuel per side and 31 gallons of fuel was added the day prior to the accident according to fuel logs.

Information provided by a family member of the former owner, revealed that about 1 to 1.5 years prior to the accident, a new fuel selector valve was installed by a mechanic, and since then, the airplane had not flown much. The family member further stated that initially there were two fuel selector valves replaced, as the initial replacement did not operate as expected. In addition, they reported that the airplane did not fly much since the fuel selector valve replacement; however, numerous ground runs were conducted.

Review of the airframe, engine, and propeller logbooks revealed that the most recent annual inspection was conducted on November 12, 2013, at a HOBBS time of 976.7 hours. A fuel selector valve was installed on August 31, 2012, at HOBBS time of 975.4 hours. At the time of the accident, the airplane had accumulated 2 hours since the annual inspection and 3.3 hours since the fuel selector valve was replaced.

Examination of the accident site by the NTSB IIC revealed that the airplane impacted trees and terrain about 1.25 miles northeast of 02WA within a heavily wooded area. An initial point of contact with trees, about 70-feet in height, was observed. The wreckage debris path was oriented on a heading of about 147 degrees magnetic and was about 238 feet in length. All major structure components of the airplane were located within the wreckage debris path. The fuselage came to rest on its right side, partially inverted. The tailwheel was observed in an extended position. The engine remained partially attached to the fuselage and displaced downward into terrain.

The wing center section, which included the inboard portion of the left wing, was located just beyond the fuselage, and was found in an upright, leading edge high attitude, with both the left and right main landing gear extended. The right wing was separated at the center section attach point. The left fuel tank was visually inspected, and fuel was observed up to the area of the fuel quantity indicator, which was separated. The right fuel cap was removed, and no fuel was observed within the right fuel tank.

The wreckage was recovered to a secure location for further examination.

Examination of the recovered wreckage revealed that the fuselage was bent and buckled throughout. The canopy structure was separated, and the roll bar was partially displaced. The left and right wings and center section were separated from the airframe. The inboard 5 feet of the right wing was separated from the center section. The outboard portion of the right wing was separated. The right flap and aileron remained attached. The left wing outboard 5 feet was separated from the wing. A circular impression was observed on the outboard left wing tip. The left aileron separated, and the left flap remained attached. Both the left and right main landing gear were found in the extended position. The right elevator and horizontal stabilizer were separated at the root. The left elevator and horizontal stabilizer, vertical stabilizer, and rudder remained attached and intact.

Flight control continuity was established from the cockpit flight controls to all primary flight control surfaces. Multiple separations were noted on the elevator and aileron control cables. All areas of separation were consistent with tension overload.

The left wing fuel tank was breached where the fuel quantity gauge was separated. The right wing fuel tank was intact. The right main, left main, and left reserve fuel screens were removed, and found to be free of debris.

The fuel selector handles in the forward and aft seats were intact, and remained attached to the fuel control junction, which was separated from the fuel selector valve. Both the forward and aft fuel selector handle position indicator plates moved freely around the fuel selector valve handle shaft. Both screws that secure either plate to the handle assembly were in place.

The fuel selector valve assembly located in the wing center section was intact, and appeared to be undamaged. All fuel lines were intact and secure to the fuel selector valve. The right wing fuel line was found connected to the fuel selector valve outlet port. The engine fuel supply line was found connected to the right fuel tank position of the fuel selector valve. The fuel selector valve was removed and disassembled. The valve was observed in the left tank position, slightly away from the detent. The internal cork was intact and undamaged. The fuel selector valve gasket was intact. It was noted that if the right wing fuel tank line and the engine supply fuel line were installed as noted above, when the fuel selector valve was positioned to either the left main or left reserve positions, no fuel would be able to flow from the left fuel tank to the engine; however, fuel would flow from the left fuel tank to the right fuel tank. If the selector valve was positioned in the right fuel tank position, fuel would flow to the engine supply line. The left and right fuel vent lines were free of debris.

Residual fuel was removed from the left and right fuel tanks. The fuel was free of debris, and blue in color.

Throttle, mixture, propeller, and wobble pump control continuity was established from the cockpit controls to the firewall. The forward seat primer was in the full in position, however, it was unlocked. It was not determined when or how the primer became unlocked.

Examination of the Pratt & Whitney R-1340-AN engine, serial number ZP-101599, revealed that it was partially attached to the fuselage via its engine mounts and controls. All accessories remained attached to the engine. The forward spark plugs were removed, and rotational continuity was established throughout the engine and valve train. Thumb compression was obtained on all nine cylinders. The carburetor was removed from the engine, and exhibited impact damage to the float bowl. The throttle plates were observed in the "open" position. The engine driven fuel pump was removed from the engine, and the drive shaft rotated freely by hand.

The induction and exhaust system was impact damaged. No evidence of sooting was observed within the exhaust.

The propeller remained attached to the crankshaft. One blade was bent aft about 90 degrees from the blade root. The outboard tip of the propeller blade was bent outward. The opposing blade was bent aft, and slightly twisted from midspan.

On August 4, 2014, the left and right magnetos were further examined and installed on a test bench. Both magnetos produced spark on all posts, and were unremarkable.

On December 19, 2014, the carburetor was further examined and partially disassembled by the NTSB IIC. The carburetor exhibited impact damage, with one of the two float bowl housings breached. One of the two metal carburetor floats was separated and crushed, consistent with impact damage. The other metal float remained intact and undamaged; however, it contained an unmeasured amount of liquid internally. No visible evidence of leakage from the float was observed. The venturies and the throttle plates were found intact. The fuel screen was free of debris.

Front Seat Pilot

The Pierce County Coroner conducted an autopsy on the front seat pilot on June 5, 2014. The medical examiner determined that the cause of death was "multiple blunt force injuries."

The cardiovascular exam identified a 450-gram heart; the average weight for heart of a man his weight is 362 grams (range 275-478 grams). The report identifies multifocal calcified atherosclerosis ranging between 30-50 percent in each of the three main coronary vessels.

The FAA's Civil Aeromedical Institute (CAMI) in Oklahoma City, Oklahoma, performed toxicology tests on the front seat pilot. According to CAMI's report, carbon monoxide, cyanide, volatiles, and drugs were tested, and had positive results for 13 ug/ml acetaminophen detected in urine, and unspecified amounts of rosuvastatin detected in urine and liver.

According to FAA records, the airline transport pilot reported using lisinopril, rosuvastatin, and ezetimibe. Lisinopril is a blood pressure medication marked under a number of names including Zestril. Rosuvastatin and ezetimibe are cholesterol lowering medications marketed as Crestor and Zetia respectively. The pilot reported high blood pressure and elevated lipids treated with the aforementioned medications. Acetaminophen is a pain reliever marked under many names including Tylenol.

Rear Seat Pilot

The Pierce County Coroner conducted an autopsy on the rear seat pilot on June 5, 2014. The medical examiner determined that the cause of death was "multiple blunt force injuries."

CAMI, performed toxicology tests on the rear seat pilot. According to CAMI's report, carbon monoxide, cyanide, volatiles, and drugs were tested, and had positive results for unspecified amounts of desmethylsertraline detected in urine and blood (heart), unspecified amounts of salicylate detected in urine, 0.203 ug/ml sertraline detected in blood (heart), and unspecified amounts of sertraline detected in urine.

Review of FAA records, the airline transport pilot rated passenger reported using simvastatin, a cholesterol lowering medications marketed as Zocor. He reported a history of a retained kidney stone that was reported to be non-operative and stable. According to an interview with the pilot's wife by the NTSB IIC, the passenger had started taking an antidepressant about 2 months prior to the accident, and on the day of the accident he appeared "pretty happy."

According to the Pierce County Medical Examiner autopsy report, the cardiovascular exam identified a 310-gram heart; the average weight for the heart of a man his weight is 317 grams (range 240-419 grams). The report identifies multifocal calcified atherosclerosis greater than 50 percent in each of the three main coronary vessels, with 80 percent occlusion middle aspect of the left anterior descending artery. The report noted that the heart muscle was without evidence of a new or old infarct.

Salicylate is the primary metabolite of aspirin, a pain reliever also used to prevent heart attacks in people who have had a heart attack in the past. Sertraline is an antidepressant also marketed as Zoloft.