N911TS

HISTORY OF FLIGHT

On February 10, 2016, at 1617 Pacific standard time, a Flight Design CTLS airplane, N911TS, flying at low altitude entered a hard left turn and descended into terrain 4 miles southwest of Springville, California. The airline transport pilot and single passenger were fatally injured, and the airplane was destroyed by a post-crash fire. The airplane was registered to and operated by the Tulare County Sheriff as a public aircraft under the provisions of 14 Code of Federal Regulations, Part 91. Visual meteorological conditions prevailed for the flight, which operated on visual flight rules company flight plan. The flight originated from Visalia Municipal Airport, Visalia, California, approximately 1446 as a local flight.

Witnesses reported seeing the airplane circling a nearby area at a low altitude, then depart to the southwest. While flying in a westerly direction the airplane made a left turn, the wings dipped left and right, then the airplane descended into the ground in a sideways wing down orientation. The engine was heard operating in a steady tone until ground impact. A post-crash fire ensured, destroying the airplane.

PERSONNEL INFORMATION

The pilot, age 45, held an Airline Transport Pilot certificate, issued on October 11, 2007, with ratings for airplane multiengine land, and commercial privileges for airplane single-engine land, rotorcraft helicopter, and instrument helicopter, and private pilot privileges for gliders. He held a flight instructor certificate with a rating for airplane single engine land issued on June 29, 2014. He held a first-class medical certificate issued on April 2, 2014, with no limitations. Examination of the pilot's civilian logbook revealed that he had 3,675 total civilian flight hours, 3,526.4 hours in single engine airplanes, 1,002.6 hours in the Flight Design CTLS, and his most recent flight review was conducted on December 8, 2015.

The passenger was a Sheriff Deputy who had been employed by the Tulare County Sheriff for about 27 years and had been assigned to the air unit for about a year. His duties as a crew member onboard the airplane was to act as an observer and operate the video camera equipment.

AIRCRAFT INFORMATION

The two-seat, high-wing, fixed-gear airplane, serial number F-11-02-05, was manufactured in 2011. It was powered by a Rotax 912ULS normally aspirated 100-hp engine and equipped with a Sensenich ground adjustable 3-bladed composite propeller. Review of the maintenance logbooks showed that the most recent 100-hour inspection was performed on February 3, 2016, at a total aircraft time of 3,103.9 hours, and a total engine time of 1,103.9 hours.

The basic aircraft was configured as an aerial observation aircraft with the following additional equipment. In the luggage compartment a FM transceiver, mini PC, video interface system, GNSS (global navigation satellite system) receiver, Airlink wireless modem, and a 12V to 28V DC converter. Located on the cabin roof was the GNSS antenna. Located in the cabin was an ARS mapping system, 15-inch LCD monitor, and camera control joy stick. On the bottom of the airplane was a spotlight. Located on the right wing was the video camera pod. Maintenance records showed that the most recent weight & balance performed on August 27, 2015, documented an empty weight plus 90 kg of fuel of 511 kg. Two crewmembers plus 4.5 kg personal gear for each, and a 2.3 kg survival kit added an additional 175.5 kgs. The total weight of the airplane at takeoff was 686.5 kgs. The maximum gross weight as stated in the manufacturers pilot operating handbook is 600 kgs. The center of gravity (cg) was calculated to be 0.448 m (meters) which was within the forward limit of 0.282 m and the aft limit 0.478 m. The airplane had been airborne for 90 minutes before the accident and would have burned about 6 gal of fuel (16.4 kg) which would equate to an aircraft weight at the time of the accident of 669.6 kg.

The Flight Design Pilot Operating Handbook states the following concerning aerodynamic stalls:

"Stalling speed for the CTLS with a weight of 600 kg (1320 lbs) is 72 km/h (39 kcas)with the flaps set at 35°, 77 km/h (42 kcas) with the flaps set at 0° and 90 km/h (44 kcas) with flaps set at -12°. Approaching stall is indicated by a sluggishness around the vertical axis. The controls become "soft" about 5 km/h (3 kts) above stall speed. Release the aft pressure on the stick to increase airspeed. Close to stall the aircraft can only be controlled by rudder and stabilizer. In a stall, the effectiveness of the ailerons is greatly reduced.

When the nose drops during a stall, the aircraft will lose approx. 50 m (165 ft)

altitude. Thus, near the ground a safety minimum speed of approx. 115 km/h (62 kts) should be maintained."

Aviation Circular 23-8C Flight Test Guide states that the following formula can be used to calculate the stall airspeed when the airplane's weight is different than the specified weight, Vs=Vstv(Ws/Wt) where Vs= new stall airspeed, Vst= standard stall airspeed, Ws= new weight, Wt = standard weight. Since the weight of the airplane at the time of the accident is known to be 669.6 kg, the standard weight is 600 kg, and the stall speed with zero flaps of 42 kcas (knots calibrated airspeed), results in a corrected stall speed of 44.4 kcas.

Flight Design provided additional aerodynamic stall information in the form of a stall speed, bank angle, and gross weight table. At a weight of 600 kg and 0° flaps the calculated stall airspeed while in a 15° angle of bank turn is 43 kcas. The stall airspeed in the same configuration at 30° angle of bank is 45 kcas. Using the formula in AC 28-8C to determine stall speeds for the airplane's higher weight of 669.6 kg results in a zero flap stall airspeed at 15° angle of bank of 45.3 kcas, at 30° angle of bank the value is 47.6 kcas, and at 45° angle of bank value is 52.7 kcas.

METEOROLGOICAL INFORMATION

The Porterville Municipal Airport automated weather observation system-3 (AWOS-3), located 11 miles southwest of the accident site, at an elevation of 443 feet mean sea level, recorded at 1556, wind from 300° at 8 knots, visibility 10 statute miles, sky clear, and altimeter setting of 30.18 inHg. A visual inspection of radial velocity observations close to Hanford, CA, located 45 miles west-north-west from the accident site, for altitudes near 1000' msl revealed a wide variety of wind magnitudes, generally below about 7 knots, coming from the northwest or north-northwest. North American Mesoscale model sounding was obtained for the accident area valid at 1600 PST, which identified a wind from about 290° true at 3-4 knots applicable for an altitude of about 1600' msl.

Sun position at the time of the accident was determined by using the National Oceanographic and Atmospheric Administration (NOAA) Solar Calculator. The Sun's position on February 10, 2016, at 1617, as viewed from the accident location was on an azimuth of 241° true and elevation of 13° above the horizon.

A pilot who had flown over the accident site shortly after the accident occurred stated that he was flying out of Springville around 2,000 feet, towards Lake Success, and that the angle the road (Highway 190) was lined up on was straight into the sun and there was a lot of haze. He could not distinguish the tops of the hills from the sky because of the (sun) visibility.

AIDS TO NAVIGATION

A Garmin GPSMAP 496 portable GPS receiver was recovered from the wreckage. The device was sent to the NTSB Vehicle Recorders Laboratory and the data contained within the unit was recovered. The data contained 10 tracklogs from February 4, 2016, through February 10, 2016. The accident flight was recorded starting 1446:36 Pacific standard time (PST) and ending 1614:11 on February 10, 2016. The aircraft departed Visalia Municipal Airport to the northwest at 1456 and turned northeastward. The aircraft briefly orbited a location in the vicinity of Ivanhoe, CA, at 1504, at an altitude of about 550 feet above ground level (agl) and continued eastward. The aircraft proceeded to make a touch and go at Woodlake Airport at 1515. The aircraft continued generally northward following the Friant Kern Canal until reaching a point east of East Orosi, CA, at 1530. The aircraft proceeded southward, briefly orbiting a location approximately 2.5 nautical miles northeast of Farmersville, CA, before continuing southeast. At 1601, the aircraft orbited a location on the northwest corner of Lake Success before continuing eastward. The aircraft maneuvered over a location northeast of Lake Success. At 1613:47 the aircraft was heading 249° true, at 1613:49 heading was 231°, at 1613:59 heading was 230°, and at 1614:00 heading was 242°. The track made a left turn and the last recorded position was at 1614:11 while the aircraft tracked 114.8° true at a GPS altitude of 1,096 feet (400 feet agl) and groundspeed of 52 knots.

WRECKAGE & IMPACT INFORMATION

The wreckage was located on a steep 20° slope covered with green grass, flowering yellow mustard plants, and uneven rock-boulders underneath the vegetation. The wreckage area was 80 feet in length on a bearing of 010° magnetic. The airplane wreckage was inverted pointing from tail to nose on a bearing of 190° magnetic. The airplane structure had been subjected to a post-crash fire that completely consumed the airplane leaving only the black carbon fiber cloth remnants of the airframe. The wings and tail remained attached to the fuselage. The initial point of ground impact consisted of the indentation of the left main landing gear tire and the left wing tip. Immediately forward of the tire indentation was a 4 foot by 4 foot area of disturbed earth containing fragments from the fiberglass nose cowling. The initial impact was consistent with a high vertical energy component and very little forward velocity energy component.

The horizontal stabilator was partially fire damaged, leaving the outboard...