WPR16FA064

The pilot’s failure to maintain airplane control while performing an acrobatic maneuver and his subsequent failure to recover from an inadvertent spin due to insufficient altitude.

The commercial pilot and pilot-rated passenger took off during the morning for a personal flight to perform aerobatic maneuvers in the World War II fighter airplane. Witnesses reported seeing the airplane performing acrobatic maneuvers. The airplane was last observed by the witnesses descending in a nose-down spiral until it impacted the ground, where a postimpact fire ensued. All the witnesses that commented about the airplane's engine stated that they heard the engine running during the nose-down spiraling descent, and some of the witnesses stated that they heard a change indicating that the engine was going from full power to a lower power setting. Postaccident examination of the airplane revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. A performance study based on radar data indicated that the airplane climbed rapidly from 5,700 to 7,700 ft mean sea level (msl), which required a significant nose-up attitude and a climb rate of over 8,000 ft per minute. It is likely that the airplane's airspeed slowed at the top of the climb and that the airplane experienced an accelerated stall and entered a spin. According to the airplane flight manual (AFM), power-on spins should never be intentionally performed in this airplane and recovery from a power-on spin required that the pilot close the throttle completely and apply controls for recovery. The manual stated that "after the rudder is applied for recovery, between 9,000 to 10,000 ft of altitude is lost." However, the maximum radar recorded altitude of 7,700 ft msl was about 6,426 ft above ground level; therefore, there was insufficient altitude available to recover the airplane from a spin. Further, the change in engine sound heard by some of the witnesses was consistent with the closing of the airplane's throttle during a power-on spin recovery as called for by the AFM. Although ethanol was detected in the pilot's tissue samples, the levels detected were not consistent with levels expected from ingestion, which suggests that the ethanol may have been from postmortem production. Further, the level detected in the liver was below that generally considered impairing. Therefore, given the low levels of ethanol detected, some or all which may have resulted from postmortem production, it is unlikely the ethanol detected impaired the pilot at the time of the accident. The pilot's medical records indicated that he had a history of atrial fibrillation that resulted in an embolic stroke about 4 years before the accident. The neurological deficits from the stoke had resolved, and his heart disease had been effectively treated with no evidence of recurrence. Therefore, there was no evidence that the pilot's medical condition contributed to the accident.

The F-51D Aircraft Flight Manual states that "no intentional power-on spins or snap rolls are permitted, as it is impossible to do a good snap roll and most attempts end up in a power spin." The manual further states that "no intentional power-off spins are permitted below 12,000 ft." The manual also states that "power-on spins should never be intentionally performed in this airplane. In a power-on spin, the nose of the airplane remains 10 to 20 degrees above the horizon, and recovery control has no effect upon the airplane until the throttle is completely retarded." In the "Power-On Spin Recovery" section, the manual states if you should ever get into a power spin: "close the throttle completely and apply controls as for the power-off spin recovery…As many as 5 or 6 turns are made after the rudder is applied for recovery, and 9,000 to 10,000 ft of altitude is lost." Additionally, the manual warns that "power-on spins are extremely dangerous in this airplane." Subtracting the accident site elevation from the airplane's highest altitude recorded (7,700 ft msl), would allow for about 6,426 ft of altitude for a spin recovery. According to the manual, the airplane's estimated stall speeds at a gross weight of 9,000 lbs, with gear and flaps up, are 101 mph level, 109 mph at 30° of bank, and 121 mph at 45° of bank. At a gross weight of 10,000 lbs, with gear and flaps up, the stall speeds are 106 mph level, 115 mph at 30° of bank, and 128 mph at 45° of bank. The Pima County, Office of Medical Examiner, conducted an autopsy on the pilot. The medical examiner determined that the cause of death was "multiple blunt force injuries." The FAA's Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicological testing on the pilot. Testing was negative for carbon monoxide, cyanide, volatiles, and tested-for drugs. Ethanol was detected in the muscle and liver. Ethanol is primarily a central nervous system depressant commonly found in beer, wine, and liquor. After ingestion and absorption, ethanol is quickly distributed uniformly throughout the body's tissues and fluids. Ethanol is also produced after death by microbial activity. Review of the pilot's FAA medical records found that they included multiple cardiology evaluations performed as part of special issue requirements because of the pilot's history of an arrhythmia and stroke. The pilot suffered a cardioembolic stroke in March 2012, because of a blood clot that resulted from atrial fibrillation. The atrial fibrillation was successful ablated in June 2012. At the time of his last FAA medical exam, he reported using rivaroxaban, a blood thinner use to decrease the risk of clots commonly marked as Xarelto. The most recent cardiology evaluation in the pilot's FAA records, dated February 2015, found no evidence of recurrent atrial fibrillation and no significant cardiovascular abnormalities. Additionally, the pilot's FAA records included multiple neurological evaluations, the most recent of which was from August 2013, which found no significant motor or cognitive impairment. The pilot's cardiology records from his treating cardiologist for the period from January 2014 to February 2016, were also reviewed. The most recent visit was dated February 5, 2016, the day of the accident. The visit was to follow up on the pilot's annual Holter monitor study (a 24-hour ambulatory electrocardiogram [EKG]). The physician documented that the pilot had done very well in the past year and had not sustained palpitations to indicate atrial fibrillation. The examination documented a normal cardiovascular examination and a normal EKG. The 24-hour monitor showed no evidence of atrial fibrillation. The cardiologist stated that from a cardiovascular standpoint, the pilot was fit for a third-class medical certificate. A review of recorded data from the Casa Grande Municipal Airport, Case Grande, Arizona, automated weather observation station, located about 21 miles east of the accident site, revealed that at 1155 conditions were wind from 010° at 6 knots, visibility 10 statute miles, clear sky, temperature 15° C, dew point -7° C, and an altimeter setting of 30.36 inches of mercury. The pilot held a commercial pilot certificate with airplane multi-engine land and single-engine land, rotorcraft-helicopter, and instrument airplane and helicopter ratings. He also held a flight instructor certificate with airplane single-engine and helicopter ratings. The pilot was issued a third-class airman medical certificate on March 10, 2015, with the limitation that it was not valid for any class after March 31, 2016. The pilot reported on his most recent medical certificate application that he had accumulated 6,700 total flight hours, and had flown 105 hours in the last 6 months. Examination of the accident site by the National Transportation Safety Board (NTSB) investigator-in-charge revealed that the airplane impacted terrain at an elevation of about 1,274 ft. All major components of the airplane were contained within the main wreckage site. Wreckage debris of mostly broken canopy pieces and small metal fragments was scattered about 150 ft in front of the main wreckage. The first identified point of contact was a large area of disturbed dirt, about 4 ft by 3 ft in size and 6 inches deep, located about 5 ft aft of the wreckage. The airplane was partially buried in dirt, and two of the four propellers blades were completely buried in the dirt. The two propellers blades that were visible, had about 1/3 of their blades in the ground. The airplane came to rest perpendicular to the edge of a road and partially buried in a crater. Across the road, an area of light vegetation of about 25 ft by 150 ft was scorched by the post-impact fire. A majority of the fuselage structure and wings were consumed by fire. The power lines located adjacent to the main wreckage were not damaged. The fuselage came to rest upright on a heading of about 180° magnetic. The wings remained partially attached to the main fuselage. The empennage was partially attached to the main fuselage. Flight control continuity was established from the individual flight controls to the center portion of the cabin. The wings sustained thermal damage, and leading-edge compression damage was observed on both wings. The left aileron was attached at all its respective mounts. The left aileron's trim tab was located behind the main wreckage. The left flap was separated but located near its normal position, in the main wreckage. The right aileron was attached at all its respective mounts and sustained thermal damage. The right flap and portions of the right aileron trim tab were separated and were located near the main wreckage. The empennage was crushed and sustained thermal damage. The vertical stabilizer was attached to all its respective attachment points, and its leading edge was crushed aft throughout its entire vertical span. The rudder was separated, and portions of it were located on top of the engine and on the right wing. The horizontal stabilizers and right elevator remained attached to all their respective attachment points. The left elevator was separated but located near its normal position behind the left horizontal stabilizer. The damage sustained to the left elevator was consistent with impact damage. Both elevator trim tabs were intact and remained attached at all their respective attach points. The instrument control panel and cabin area were mostly consumed by the post-impact fire. The mounts to a video recording system were found in the wreckage but the recording devices were located, at a later date, in the airplane's hanger. Following the on scene examination, the airplane wreckage was recovered to a secure facility for further examination. The dual-seat, low-wing, retractable gear, tail wheel airplane, serial number 44-85634, was manufactured in 1944. The airplane was a type of American fighter us