History of Flight
On August 20, 2011, at approximately 1341 central daylight time, a Vertical Unlimited LLC Model 12 airplane, registration N2BJ, was substantially damaged after impacting terrain at the Charles B. Wheeler Downtown Airport (MKC) in Kansas City, Missouri. The pilot was conducting an aerobatic routine as part of the Kansas City Aviation Expo. The flight was operated under 14 Code of Federal Regulations Part 91 and a Certificate of Waiver for the air show. Visual meteorological conditions prevailed, and no flight plan was filed. The local exhibition flight departed MKC about 1336.
Video footage of the final portion of the routine showed the pilot exiting a Lomcevak maneuver into a right, inverted spin. After recovery from the inverted spin, as the airplane pitched up from a nose-down attitude, it rolled left and the nose dropped. The airplane yawed left (counterclockwise) during the final descent, completing about one and one-half revolutions before impact. The video resolution did not allow assessment of flight control surface deflections.
A series of six photographs taken at roughly one-second intervals before the accident depicted the airplane in a nose-low attitude, upright with wings level to a slight left bank. The smoke from the aerobatic smoke system was on. In the fifth photograph, the smoke stream appeared approximately vertical, with an angle of about 30 degrees between the wing chord and the smoke orientation. The elevator appeared deflected upward, the right ailerons upward and left ailerons downward, and the rudder appeared neutral or slightly right in the first two photos, then left in subsequent photos. All control surfaces appeared intact and within normal range of travel.
A colleague of the pilot stated that the Lomcevak maneuver was initiated on an inverted 45-degree up-line, followed by full forward elevator and full left rudder. He noted that recovery typically resulted in straight-ahead flight, but occasionally required recovery from an inverted spin. The pilot appeared to initiate the maneuver more aggressively than in previous performances.
Another colleague reported that the Lomcevak included an extra rotation and that the subsequent exit into an inverted spin was not unusual.
Personnel Information
The pilot held an Airline Transport Pilot certificate with single- and multi-engine land ratings, including type ratings for A-320, B-747-4, DC-9, and SA-227. The single-engine land rating was limited to commercial privileges. He also held a current Acrobatic Competency card with a minimum altitude limitation of 250 feet above ground level. A first-class medical certificate was issued on March 1, 2011, with a requirement for corrective lenses. He reported approximately 22,000 total flight hours, with 300 in the previous six months. The pilot had 15 years of aerobatic experience in various aircraft and was involved in the development and construction of the accident airplane.
Aircraft Information
The accident airplane was an amateur-built Vertical Unlimited Model 12, serial number 297, a modified single-place aerobatic biplane based on the two-place Pitts Model 12. The front cockpit was removed and replaced with smoke and auxiliary fuel tanks; the wing fuel tank was eliminated. Ailerons were lengthened and an additional hinge point added. It was powered by a 412-horsepower modified Vedeneyev M14P radial engine with a three-bladed MT Propellers MTV-9-K-C propeller. An experimental exhibition category airworthiness certificate was issued on March 5, 2009. The most recent condition inspection was on February 1, 2011, at 196.1 hours total airframe time. The engine oil and filter were changed on June 16, 2011, at 207.0 hours.
Meteorological Information
The MKC Automated Surface Observation System at 1354 recorded calm wind, 10 miles visibility with light rain, clear skies, temperature 24°C, dew point 20°C, and altimeter 29.97 inches of mercury. A colleague noted that the airplane was briefly moved into a hangar when rain began shortly before the scheduled performance; after about 15 minutes the rain stopped and the pilot began his routine. Cloud cover was reported as high enough not to affect the routine.
Airport Information
Charles B. Wheeler Downtown Airport is a public facility located along the Missouri River at an elevation of 757 feet, with two hard-surfaced runways: 1-19 (6,827 ft by 150 ft) and 3-21 (5,050 ft by 100 ft). Air traffic services were provided by the Airport Traffic Control Tower and the Kansas City Terminal Radar Approach Control. The airport was hosting the Kansas City Aviation Expo, operating under an FAA Certificate of Waiver that authorized day and night aerobatic demonstrations, high-speed flight, and parachute demonstrations within five miles of the airport up to 16,000 feet msl.
Wreckage and Impact Information
The accident site was on the airport grass infield about 280 feet west of the runway 1-19 and 3-21 intersection. The airplane came to rest upright with all major components in place. The forward fuselage, engine, cockpit, and inboard portions of the upper and lower wings were consumed by a postimpact fire. The aft fuselage and empennage remained intact and largely unaffected by the fire. The engine and propeller assembly were partially embedded. Main landing gears collapsed. A postaccident airframe examination revealed no preimpact anomalies.
Flight controls remained attached. Aileron control continuity was confirmed, except for a separated push-pull tube rod end at the left lower aileron bellcrank and a separated left wing aileron slave strut, both consistent with overstress. Elevator and rudder continuity was confirmed; the elevator push-pull tube and rudder cables had been cut for recovery. Elevator trim cables were separated consistent with overload. Engine mixture and propeller control continuity was confirmed; the throttle cable was separated at the throttle body consistent with impact.
The engine showed impact damage: the nose case and No. 6 cylinder were displaced; the reduction gear rotated freely; the crankshaft rotated freely; the master rod and articulated rods rotated freely; the No. 6 cylinder connecting rod was bent; the master rod bearing appeared intact; pistons showed no scoring; spark plugs had normal combustion signatures; the oil pump rotated freely; the oil screen had no foreign material; the supercharger rotated freely and contained ingested soil and residual fuel. All three propeller blades separated due to overstress/impact.
The Data Acquisition Unit and Electronic Flight Information System were sent to the NTSB lab; EFIS data was not relevant to the accident flight, and no data was recovered from the DAU.
Medical and Pathological Information
An autopsy performed by the Jackson County Medical Examiner's Office on August 21, 2011, attributed the pilot's death to blunt force traumatic injuries. The FAA forensic toxicology report detected nordiazepam in urine but not in blood; oxazepam not detected in blood but 0.021 ug/ml in urine; temazepam detected in urine but not in blood. These are metabolites of diazepam (Valium). The pilot's medical records indicated he sought treatment for vertigo in March 2010, reporting off-balance and nauseated sensations during aerobatics and after exiting the airplane. He reported feeling better after treatment, but dizziness returned when he flew. A physical therapist prescribed further treatment, but the pilot did not return. A colleague noted the pilot had ceased flying for about three months after the initial vertigo event and completed treatment; at the time of the accident, he showed no signs of impairment and appeared healthy. The autopsy also noted atherosclerotic disease with one coronary artery up to 99% occluded, an enlarged heart, and a congenital anomaly of the aortic valve. Histology showed transmural hypereosinophilic myocytes with contraction bands and interstitial edema. No medical records indicated a diagnosis of heart disease.
Tests and Research
A Garmin 496 GPS unit was recovered and data downloaded. Data showed two flights: one on August 19, 2011, from about 1326 to 1411, and one on August 20, 2011, from 1333:35 to 1341:40, with takeoff around 1336. Altitude, ground speed, and ground track variations were consistent with aerobatic maneuvers.
Additional Information
The FAA Airplane Flying Handbook describes a spin as an aggravated stall leading to a downward corkscrew path. Spin recovery involves reducing throttle to idle, neutral ailerons, full opposite rudder, and forward elevator. Excessive elevator use can cause a secondary stall and another spin.