And just as I stated from day one, there was no stall of any kind, but rather controlled flight into the ground.CEN13FA274HISTORY OF FLIGHTOn June 22, 2013, at 1247 eastern daylight time, a Boeing IB75A, N450JW, impacted terrain at the Dayton International Airport (KDAY), Dayton, Ohio. The commercial pilot and wing walker were both fatally injured. The airplane was destroyed. The airplane was registered to a private individual and operated by Jane Wicker Airshows under the provisions of 14 Code of Federal Regulations Part 91 as an airshow performance. Visual meteorological conditions prevailed for the flight, which operated without a flight plan. The local flight originated from KDAY about 1235.The flight was performing for the 2013 Vectren Dayton Air Show, which was located at KDAY. The performance was the fourth act scheduled on June 22. Video and photos submitted by spectators, who witnessed the accident, captured the airplane during the performance. The evidence showed the airplane completed a left "tear drop" style turn as the wing walker positioned herself on the lower left wing. The airplane then rolled left to fly inverted. While flying from the southwest to the northeast in front of the spectators, the airplane's nose pitched slightly above the horizon. The airplane then abruptly rolled to the right and impacted terrain in a left wing low attitude. A post impact fire ensued and consumed a majority of the right wing and forward portion of the fuselage.Statements gathered by the NTSB and Federal Aviation Administration (FAA) indicated that the pilot and wing walker had practiced the performance the day prior to the accident. Following the practice, neither the pilot nor the pilot-rated wing walker, reported any mechanical anomalies with the airplane to the air show crew.PERSONNEL INFORMATIONPilotThe pilot, age 64, held a commercial pilot certificate with ratings for airplane single engine land, airplane single engine sea, and glider. On August 30, 2012, he was issued a second class medical certificate with the restriction that he must wear corrective lenses. The pilot reported his use of Lisinopril and Triamterene to control hypertension with no reported side effects. On September 16, 2012, the pilot was issued a statement of acrobatic competency. He was authorized to perform solo aerobatics, fly wing walker maneuvers, and "circle the jumper." His altitude limitation was level 1 restricted and he was authorized to perform these events in all variants of the Extra 300, Boeing Stearman, and Pitts Special. A review of the pilot's log book revealed that the pilot had 1,190 hours, 95 hours in make and model, and about 11 hours in N450JW. The pilot did not log any flights from October 20, 2012, until April 13, 2013, which could be attributed to the air show off season. From April 13, 2013, he logged 16 hours of total time, 4.5 hours in make and model and about 1.5 hours in N450JW. The last airshow that the pilot performed with the accident wing walker was August 21, 2012.The pilot practiced the aerial routine the day prior without incident. Members of the airshow crew ate dinner with the pilot the night prior, between 1900-2100. The pilot consumed about 1.5 beers with his meal. The pilot and crew went back to their hotel. They met the following morning from 0745-0830 the crew ate breakfast and the pilot ate a bagel with cream cheese. At 1100 the pilot ate lunch. Throughout the day the crew recalled that the pilot stayed out of the sun and was drinking water. Prior to flight, the pilot sat in an air conditioned truck for at least 10 minutes. Interactions with him where uneventful and his behavior was described as normal.Wing walkerThe wing walker, age 45, held a commercial pilot certificate for airplane single engine land, airplane multi-engine land, and instrument airplane. The wing walker had about 6 years of experience and had been performing the planned routine for the previous 3 years. The wing walker was also the owner of the accident airplane.AIRCRAFT INFORMATIONThe Boeing-Stearman IB75A, serial number 75-789 was manufactured in 1941 as a model A75N1. In 1950, modifications were made to the airplane and the model type changed to IB75A. A 450-horsepower Pratt & Whitney R-985-AN-1 fuel-injected engine drove a two bladed, metal, Hamilton Standard 2D30 propeller. On December 8, 2009, the pilot purchased the airplane and on May 3, 2010, the airplane was registered with the FAA under the experimental exhibition category. On September 26, 2011, the airplane was last registered under the restricted category for the purpose of wing walking. The airplane was modified with an inverted fuel and oil system, and a four aileron system.A combined 100 hour and annual inspection were accomplished on April 23, 2013, at a tachometer time of 260.7 hours, and 597.5 hours since the engine's last major overhaul.METEROLOGICAL INFORMATIONWeather at the time of the accident was wind from 220 degrees at 10 knots, visibility 9 miles, a broken ceiling at 3,500 feet, temperature 86° Fahrenheit (F), dew point 72° F, and a barometric pressure of 30.18 inches of mercury.AIRPORT INFORMATIONThe air show airspace was orientated along runway 6L/24R. The scheduled wing walking performance was flown by the accident pilot with events being performed by the wing walker. The designated airshow area was 12,000 feet long and 2,700 feet wide. The accident airplane was assigned to the Category III performance area which provided a 500 foot airspace buffer between the performance and the spectators. The wreckage came to rest over 500 feet from the fence line of the spectator area within the assigned performance area. A document depicting the airshow's layout is included in this report's docket.The airport's elevation is 1,009 feet. Utilizing the barometric pressure, the pilot would have set about 29.09, in order to achieve "QFE" or a reading of 0 feet on the airplane's altimeter.WRECKAGE AND IMPACT INFORMATIONThe crash site was a grass area south of the intersection of taxiway R and taxiway Z. The debris field followed a 050° heading and was about 145 feet long. The first ground scars were two parallel scars consistent with the left wing's impact. About 40 feet from the beginning of the ground scars was the impact crater. The crater was 11 feet long, 6 feet wide, and at least 13 inches deep. The main wreckage came to rest 105 feet from the impact crater.A postaccident examination of the airplane was conducted by the NTSB and FAA. Rudder and elevator control continuity was established from the rudder to the aft seat rudder pedals and the elevator to the control stick. The ailerons controls were broken and torn in multiple locations. The breaks and tear patterns were identified on each opposite surface. Thermal damage was sustained to the right aileron's connecting rod from the inboard connector to the outboard hinge. However, each of the rod ends remained attached and secured in their respective hinges.The cockpit instrumentation sustained minor damage. The following readings, in part, displayed:Altimeter: 300 feetKollmans window: 29.09Manifold pressure: 30 inchesTachometer hour: 284.9The two metal propeller blades were labelled A and B for documentation purposes only. Blade A displayed leading edge polishing, nick and gouges, and chord wise scratches. From the blade's mid-span to the blade tip, the blade was curled rearward. Blade B displayed leading edge polishing, nicks and gouges, and chordwise scratches. The blade displayed an S-bend along its entire length. Cylinders number 2, 3, and 4 were found separated from the engine. No preimpact anomalies were detected with the airframe or engine.MEDICAL AND PATHOLOGICAL INFORMATIONAn autopsy was performed on the pilot by the Montgomery County Coroner's Office. The coroner ruled the cause of death as the result of multiple trauma. The manner of death was ruled an accident.Forensic toxicology was performed on specimens from the pilot by the FAA Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma. Testing was negative for presence of carbon monoxide and ethanol. Triamterene was detected in urine and blood. The pilot's use of triamterene was previously reported to the FAA.TESTS AND RESEARCHAccident sequenceSeveral videos and photographs were taken of the accident sequence by the airshow spectators. The description of the deflection of the flight controls are described using the airplane's upright orientation and the direction is not reversed when describing the flight control position when the airplane is inverted.The accident maneuver began with the pilot climbing up and away from the crowd in order to allow the wing walker to position herself under the right lower wing. During the maneuver, the airplane is turned and aligned parallel to and behind the Category III show line. The accident sequence climb out was gradual as the airplane completed the teardrop maneuver and turned to position along the show line. At 8 seconds prior to impact, the airplane pitched nose up and began a left roll. As the airplane rolled left through 45°, the pilot applied right rudder and the rudder would remain deflected right throughout the accident sequence. At 6 seconds prior to impact, the airplane rolled through 90°, the airplane's elevator is near neutral with a slight deflection downward toward the "nose-down" position, and the rudder deflected right. The airplane did not reach a completely inverted positions and stops turning about 150°. At 2 seconds prior to impact and nearly inverted, the ailerons deflect to command a right roll and the elevator deflects upward, trailing edge up relative to the fuselage. The airplane pitched toward the ground and begins a descending right roll. The control inputs continued as the airplane collided with terrain.Video studyA study of videos submitted to the NTSB was conducted in order to better under the airplane's flight parameters prior to the accident. Of the numerous videos submitted, five were selected for the study based on their location, duration, and image quality. The accident maneuver began with the airplane flying away from the crowd to the west in a climbing teardrop turn to align itself with show line parallel to runway 6L. As the airplane turned toward the crowd it began descending. The wing walker was hanging inverted by her legs from the leading edge of the lower left wing. About 9 seconds prior to the accident the airplane pitched up and rolled left. The airplane passed through 90° of roll about 6 seconds prior to the accident; a still image captured the airplane with a slightly trailing edge down elevator position. The airplane continued its roll until it was nearly inverted, but stopped at 156°or 24° short of fully inverted flight. The wing walker remained seated on the leading edge of the lower right wing. About 1.86 seconds prior to the accident, an extracted frame from a video showed the elevator was in a neutral position and the rudder was deflected trailing edge right. The airplane's flightpath prior to the right roll was toward hangers and in the proximity of a parked Boeing 757. About 1.40 seconds prior to the accident with the airplane still nearly inverted, the elevator deflected trailing edge up with the rudder still deflected trailing edge right. The airplane then pitched toward the ground at an estimated rate of 55° per second. About 0.10 second later, the aileron on the lower left wing was deflected trailing edge down and the airplane rolled to the right as it pitched toward the ground. The positions of the other ailerons were not visible in the frame. During the final 2 seconds, the airplane's groundspeed reduced from about 106 knots to 84 knots.Airspeed CalculationsThe video study indicated that the ground speed during the final maneuver slowed from 106 knots to 84 knots. Correcting for the prevailing wind, the true airspeed decreased from about 96 to 74 knots and the calibrated airspeed decreased from about 92 knots to 71 knots (106 mph to 82 mph). Of note, the maneuver's target airspeed is reported to be 110 mph.ADDITIONAL INFORMATIONPlanned "On Top of the World" maneuverThe wing walker's ex-husband was one of her regular pilots and was very familiar with the accident routine. He estimated that he flew the maneuver with the wing walker between 300-350 times. He stated the accident maneuver flown follows a maneuver where the wing walker is suspended by her ankles at the end strut. At the end of the pass she repositions herself on the wing for the next maneuver. The pilot flies a 270° re-positioning turn. The re-positioning turn has two purposes: position to perform in front of the crowd's field of view and gain altitude to aid in picking up speed for the maneuver's entry. During the turn the airspeed is reduced between 70-80 mph indicated airspeed to reduce the airflow against her body as she moves along the wings. After completing the turn and the wing walker sitting in position, the pilot notifies the wing walker that he is beginning the maneuver. The pilot adds engine power, dives the airplane down, and the wing walker extends her body beneath the wing. The airplane's is dived to reach a minimum of 100 mph before the pilot pitches the nose of the airplane between 25-30° nose high and rolls inverted. The airplane should stabilize inverted, wings level at 110 mph and 150 feet AGL. Engine power is reduced to about 1/3 throttle setting, which maintains the 110 mph and allows a margin of power sufficient to climb inverted if needed. To exit the maneuver, the pilot pushes the stick forward to get the airplane's nose above the horizon and the airplane is rolled to the left. The left roll ensures that the wing walker's body remains in a positive G condition, and therefore in contact with the wing throughout the maneuver.Review of the accident maneuverThe ex-husband/regular pilot was not in attendance at the airshow, and was provided video to review the accident sequence. When asked about to review the maneuver flown on the day of the accident, he stated that he has never seen the accident pilot fly that way and had never seen the planned maneuver flown in that manner. He described the re-position turn as shallow with little climb. In addition, the airplane didn't appear to gain much airspeed. When repositioned for the maneuver, the airplane was not dived at a steep angle to gain airspeed and the wing walker began extending later than normal. The airplane pitch up was lower than normal and as the pilot rolled towards the inverted position, the airplane never got inverted. The airplane's roll toward inverted was stopped short of expected and appeared to stop with bank taking the airplane towards the crowd line. The airplane seems to have a predominant sink rate throughout the maneuver and the pilot likely pushed forward stick to arrest the sink rate, but this would have altered the flight path more towards the crowd line. During the maneuver, there was a moment when the regular pilot perceived that the airplane's descent was arrested and the airplane was tracked level. He described this condition as key to an aerobatic pilot since the airplane is in a stable condition. To exit the inverted maneuver, a pilot should apply power and either perform a climb away from the ground, or allow for enough energy for a coordinate turn. He described the pilot's next action as a reversed right turn which appeared to be a quick, "knee-jerk" reaction. He theorized that the pilot may have been "spooked" perhaps by a potential collision conflict with a parked airplane on the ramp or other obstruction. The pilot rolled right and pulled back on the stick to perform a "dish out" maneuver, but performed this maneuver into the ground.Perceived collision potentialOn the day of the accident, there was a parked Boeing 757-200 on runway 36/18 adjacent to the intersection of taxiway C and taxiway V, over 700 feet behind the spectator line. The height to the top of the fuselage is 20 feet, 7 inches and the height to the top of the vertical stabilizer is 44 feet, 6 inches. The 757 was parked about 0.3 miles east-southeast of the accident site. In addition, about a 1/2 east-southeast to south of the accident site, there were several aircraft hangers and buildings ranging in heights from 35-50 feet.Crew prebriefDuring the morning prebrief, a crew member overheard the wing walker talking with the pilot. She commented that the pilot did not reduce power enough prior to her getting into positions around the wings. The crew member commented that the pilot listened closely and appeared to be deep in thought after the conversation.Emergency ResponseDue to a prior accident in 2007, aircraft rescue and firefighting (ARFF) vehicles were prepositioned for a quick response to an emergency. On the day of the accident, two ARFF vehicles were prepositioned, one at taxiway M near the terminal apron (vehicle 22) and one at the intersection of taxiway V and C (vehicle 23). About 1 minutes and 5 seconds after the accident, vehicle 23 arrived on scene and began firefighting efforts. The main fire was extinguished within 20 seconds. Vehicle 22 arrived on scene 1.5 minutes later to provide assistance.The National Transportation Safety Board determines the probable cause(s) of this accident as follows:The pilot's controlled flight into terrain. Contributing to the accident was the pilot's modified airshow maneuver, which placed the airplane at low altitude and airspeed and out of position within the performance area.