History of Flight
On January 25, 2017, at 1539 central standard time, a Cirrus Design SR-22 airplane, N401SC, was destroyed during an in-flight collision with trees and terrain about 1 mile southeast of Stinson Municipal Airport (SSF), San Antonio, Texas. The pilot was fatally injured. The airplane was registered to and operated by the pilot under Title 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed, and the flight was not operated on a flight plan. The flight originated from San Antonio International Airport (SAT) at 1533, with an intended destination of SSF.
Federal Aviation Administration (FAA) air traffic control (ATC) radar data indicated that the flight departed from runway 4 at SAT and proceeded southbound toward SSF at an altitude of about 2,500 feet mean sea level (msl). At 1536, the pilot contacted the SSF control tower and informed the controller that the flight was 8 miles north of SSF. The controller instructed the pilot to enter a right downwind for landing on runway 32. At 1538, the SSF tower controller cleared the pilot to land. The controller subsequently observed the airplane turn from downwind to base in the traffic pattern but did not observe the accident sequence itself.
A witness reported observing the airplane from the opposite side of the San Antonio River; the wings were "totally vertical." The airplane appeared to be on a northeast heading and losing altitude. It subsequently nosed over and descended toward the ground. Another witness observed the airplane for about 2 seconds before it descended below the tree line. The airplane appeared northbound with wings nearly vertical, and its altitude seemed relatively constant during that brief observation, though it appeared to be moving more slowly than other airplanes. The engine sounded "fine," though somewhat louder than other airplanes, possibly because it was lower.
An NTSB airplane performance study based on data from the airplane avionics system indicated that the airplane entered the SSF traffic pattern at about 1,400 ft msl and 117 knots calibrated airspeed (KCAS). It slowed to about 95 KCAS and descended to about 1,200 ft msl on the downwind leg. The airplane then entered a continuous right turn from downwind toward final approach to runway 32. The data suggested the pilot did not fly a traditional rectangular traffic pattern but instead flew a circling base-to-final pattern.
About 1539:44, the airplane appeared to level briefly before beginning a shallow climb. The data suggested it was approaching the extended runway 32 centerline at 103 KCAS, 796 ft msl, and an approximate 48° right bank. About one second later, the airplane entered a descent that ultimately exceeded 1,800 fpm. Lateral accelerations began increasing about 1539:41 and reached 0.49g about 1539:45, varying between 0.37g and 0.62g for the remainder of the dataset. These accelerations were consistent with sideslip angles of 15° to 20° during the final turn. The calculated angle-of-attack (AOA) of the wing exceeded the critical AOA of 24° about 1539:48. Shortly afterward, the descent rate of 1,800 fpm was recorded. Although the pilot's control inputs were not directly recorded, the large lateral accelerations are consistent with left rudder input and an uncoordinated flight condition.
Personnel Information
The pilot held an FAA commercial pilot certificate with single-engine and multi-engine land airplane, and instrument airplane ratings. He was also a current U.S. Air Force pilot. He passed a flight duty medical examination in September 2016, which satisfied the requirement for an FAA medical certificate in accordance with 14 CFR 61.23 (b)(9). U.S. Air Force records revealed that the pilot had accumulated 2,411.7 hours total military flight time, with the majority in B-1B airplanes. On his most recent FAA medical certificate application (July 2006), he reported a total civilian flight time of 145 hours. His civilian logbook was not available to the NTSB.
Aircraft Information
The airplane was issued an FAA airworthiness certificate in June 2004. It was purchased by the pilot and a co-owner in June 2016. Maintenance records showed that the most recent annual inspection was completed on January 24, 2017 (the day before the accident) at an airframe total time of 1,123.3 hours. At the time of the accident, the airplane had accumulated 1,124.6 hours.
A friend of the pilot reported that he had flown the airplane in December 2016. While in cruise flight at 7,500 feet, the stall warning activated and the autopilot disengaged. Maintenance documentation dated December 8, 2016, noted that the stall warning line was blocked. The blockage was removed, and the stall warning system was tested and determined to be operational.
The stall speeds published in the Pilot's Operating Handbook (POH) are 70 KCAS at a bank angle of 45° and 84 KCAS at a bank angle of 60°, with flaps full down (100%) and a forward center of gravity. This stall speed data applies when engine power is at idle, the airplane is in level flight attitude, and at a maximum gross weight of 3,400 lbs. The published stall speeds are contingent on coordinated flight and do not account for adverse effects of sideslip, which was experienced during the final turn.
Meteorological Information
Visual meteorological conditions prevailed at the time of the accident, with surface wind from 010° at 12 knots. The wind aloft at 3,000 ft was forecast from 030° at 18 knots. An AIRMET advisory was in effect for possible moderate turbulence below 18,000 ft. At 1228, a pilot reported moderate turbulence about 15 miles northwest of SAT between 9,000 ft and 7,500 ft. No other pilot reports for turbulence below 18,000 ft within 100 miles of SAT were on file.
Wreckage and Impact Information
The airplane impacted a wooded area about one-half mile southeast of the runway 32 arrival threshold. Tree breaks began about 105 ft from the airplane wreckage. The impact path was oriented on an approximate 050° bearing. A ground impact mark was located about 30 ft from the airplane wreckage along the impact/debris path. The airplane came to rest upright on an approximate bearing of 270°.
Airframe and engine examinations did not reveal any anomalies consistent with a pre-impact failure or malfunction.
Additional Information
The Cirrus Design SR-22 Pilot's Operating Handbook stated that the airplane stall characteristics are conventional. Power-off stalls may be accompanied by slight nose bobbing if full aft stick is held. Power-on stalls are marked by a high sink rate at full aft stick. Extreme care must be taken to avoid uncoordinated or accelerated control inputs when close to the stall, especially near the ground. If, at the stall, the flight controls are misapplied and accelerated inputs are made to the elevator, rudder, and/or ailerons, an abrupt wing drop may be felt and a spiral or spin may be entered.
The FAA Airplane Flying Handbook (FAA-H-8083-3B) notes that coordinated flight is important to maintaining control. Uncoordinated flight, depending on flight control deflections, may support pro-spin inputs, especially hazardous at low altitudes. A cross-control stall occurs when the critical AOA is exceeded with aileron pressure in one direction and rudder pressure in the opposite direction, causing uncoordinated flight. The aerodynamic effects of such a stall can occur with little warning.
Medical and Pathological Information
The Bexar County Medical Examiner performed an autopsy and attributed the pilot's death to blunt force injuries sustained in the accident. Toxicology testing by the FAA Bioaeronautical Sciences Research Laboratory was negative for all substances in the testing profile.