History of Flight
On September 16, 2012, about 1515 central daylight time, a Yakovlev Yak-52, N2207X, operated by an individual, was substantially damaged when it impacted terrain after a loss of control at Moontown Airport (3M5), Brownsboro, Alabama. The pilot and the student pilot rated passenger were fatally injured. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight under 14 CFR Part 91.
The accident occurred on the last day of the Moontown Airport Annual Grass Strip Fly In, organized by the Experimental Aircraft Association, Chapter 190, and the airport. Several witnesses observed three Yak-52 airplanes flying from west to east in trailing formation, each slightly lower than the one in front. When southeast of the airport, the lead airplane performed a barrel roll, followed by the second airplane. The third airplane then entered a barrel roll, but the nose dropped into an extremely low attitude as it came through the inverted arc. The roll stopped, and the airplane was almost full nose down in a vertical descent. It immediately began pitching up to about 45 degrees nose low, then began to oscillate rapidly about the roll and pitch axes. A few seconds later, the heading changed approximately 180 degrees while the airplane continued descending at a 30 to 45 degree nose low attitude, oscillating until it was lost from sight behind trees. The sound of impact was heard, and smoke was observed.
Personnel Information
According to FAA records, the pilot held a private pilot certificate with ratings for airplane single-engine land and instrument airplane. His most recent second-class medical was issued on February 29, 2012. He had accrued 6,150 total hours of flight experience.
The student pilot rated passenger held a student pilot certificate with a third-class medical issued on November 21, 2011. At the time of the examination, he reported 12 total hours of flight experience.
Aircraft Information
The accident aircraft was a low-wing, two-seat monoplane of conventional metal construction, equipped with retractable landing gear and wing flaps. It was powered by a 9-cylinder, 360-horsepower radial engine with a two-bladed, counter-clockwise rotating, variable-pitch wood and fiberglass laminated propeller. The airplane was capable of performing aerobatic maneuvers up to +7 G and -5 G. It was manufactured in 1982 and issued a special airworthiness certificate in the exhibition category on November 19, 1999. The most recent conditional inspection was completed on August 31, 2012, at which time the airframe had accrued about 1,575.7 total hours. The engine had 1,008.1 total hours and 384.4 hours since its last major overhaul on April 11, 2006.
Meteorological Information
The recorded weather at Madison County Executive Airport (MDQ), about 8 nautical miles northwest, at 1415 included: winds calm, visibility 10 miles, broken clouds at 4,900 feet, temperature 28°C, dew point 17°C, and altimeter 30.03 inches of mercury.
Wreckage and Impact Information
Examination of the accident site and wreckage revealed no evidence of any preimpact malfunctions or failures that would have precluded normal operation. The airplane's energy path was on an approximate 90-degree heading. Initial impact was at an elevation of 686 feet mean sea level, marked by a 3-foot-diameter crater about 2 feet deep. One wooden propeller blade was imbedded there. The engine and cowling separated and came to rest about 50 feet along the path. The left outboard wing section was found about 90 feet from the crater, and the main wreckage came to rest about 150 feet from the crater on a 290-degree heading. Wreckage distribution included flight control surfaces, engine parts, landing gear, and canopy debris. The engine firewall to rear cockpit area sustained thermal damage from a post-impact fire. The front-to-rear seat flight control connecting tube was fractured at rivet holes, with fractures at a 45-degree angle consistent with overstress separation.
Engine examination revealed no preimpact failures. The engine was intact but the drivetrain could not be rotated due to impact; continuity was established from the propeller hub to the back of the engine. Spark plugs appeared normal, intake and exhaust valves were normal, and the carburetor and magnetos were attached and showed no anomalies.
Additional Information
According to the co-owner of the airplane, the accident pilot was an experienced aerobatic pilot who sometimes became rusty after periods of inactivity. A few weeks before the accident, the pilot mentioned wanting to brush up on barrel rolls, noting a tendency to "dish out." The co-owner considered a dish-out not normally dangerous with sufficient altitude. On the accident day, the pilot had flown several formation sorties. The formation consisted of four aircraft: three Yak-52s and one Nanchang CJ-6. All pilots were experienced in formation flight and were members of the Red Star Pilots Association Formation and Safety Team (FAST). The co-owner observed from the ground as the three Yak-52s performed lazy eights and barrel rolls. The accident pilot's last roll dished out very badly, resulting in an extremely nose-low attitude. The co-owner felt recovery might have been possible with careful control, but then observed an accelerated stall.
Barrel Roll Maneuver
According to the International Aerobatic Club, a barrel roll combines a loop and a roll, resulting in a horizontal cork-screw flight path. Positive Gs range from about 0.5 to 2.5-3 Gs. Examination of the maneuver showed that failure to raise the nose sufficiently during the first 45 degrees could lead to a nose-low attitude and high airspeed. Insufficient back pressure could cause a dish-out during the inverted portion. Inadequate roll rate could cause overshoot of the recovery heading, and excessive roll rate could cause undershoot. Rudder input errors produce similar effects.
Regulatory Considerations
No aerobatic practice area or contest box existed at or near 3M5. No low-altitude waiver for aerobatics was requested, nor was a certificate of waiver or authorization requested by the fly-in organizers or airport. The flight operations manual of the fly-in did not contain specific guidance on aerobatic demonstrations. The airport manager's guidance, written by the accident pilot years earlier, referenced 14 CFR Part 91.303 (incorrectly cited as 91.301) and recommended aerobatic flight between 2,200 and 3,500 feet MSL over specific areas. However, the experimental operating limitations for the airplane stated that no person may be carried during exhibition of flight capabilities unless essential for the flight.
Medical and Pathological Information
Autopsies performed by the Alabama Department of Forensic Sciences determined the cause of both deaths as blunt force injuries. Toxicological testing of the pilot and passenger were negative for carbon monoxide, cyanide, and drugs, except Ibuprofen detected in the passenger's urine.
Tests and Research
Analysis of the barrel roll maneuver indicated that improper execution, such as insufficient pitch or roll rate, could result in loss of control.