NTSB Factual Report

HISTORY OF FLIGHT

On October 24, 2017, about 0820 central daylight time, an Air Tractor AT-502B airplane, N502G, impacted a field about 5 miles west of Olton, Texas. The pilot sustained serious injuries and the airplane was destroyed by a postimpact fire. The airplane was registered to GB Aerial Applications Inc., and operated by King Ag Aviation Inc., under the provisions of Title 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed at the time of the accident and no flight plan had been filed. The local flight had departed Fairview Field Airport (XA05), Sudan, Texas at 0748.

Multiple witnesses observed the airplane flying overhead but only one witness observed the accident sequence. The witnesses reported that the airplane was flying north over highway 70 and made a left turn towards the west about 300 ft above ground level (agl). During the left turn the airplane descended, impacted a field, and burst into flames. A large white trailer in the field blocked his view of the airplane as it impacted the ground, so he did not see the final impact, but he observed everything up to that point. He did not see any smoke or fire coming from the airplane during the accident sequence.

The pilot was transported via helicopter to a hospital in Lubbock, Texas.

PERSONNEL INFORMATION

At the time of the accident the pilot was employed by King Ag Aviation, the operator of the airplane.

A review of the pilot's logbook revealed he had received a high-performance airplane endorsement on February 11, 2016. The pilot accumulated 303.5 hours in an Air Tractor 502, registration N89MG, between July 16, 2017, and August 15, 2017. He accumulated 93.6 hours in the accident airplane between August 25, 2017, and September 10, 2017. The final logbook entry was dated October 19, 2017, for a flight review in a Cessna 172. The flight review included 1.1 hours, 2 simulated instrument approaches, 4 day landings, and 4 night landings.

The pilot was employed by a different agricultural aerial application company from March 2016 to June 2017, during which time he flew an Air Tractor AT-301 airplane and an AT-400 airplane conducting aerial application operations. The owner of the company described the pilot's abilities as "OK" and that the pilot was terminated for insubordination related to his duties as a company pilot. Another company pilot reported to the owner that the accident pilot was known to make very tight turns after a spray pass. The accident pilot was reportedly cautioned by the owner and senior company pilots about making tight turns. The owner also stated that on one occasion the accident pilot departed with his windscreen obscured by frost and during the takeoff the airplane almost collided with a stationary airplane on the ground.

AIRPLANE INFORMATION

On October 10, 2017, a 100-hour inspection was completed at an airframe total time of 7,917.2 hours. The maintenance logbook entry for this inspection stated that the header fuel tank was removed and replaced with a new tank from Air Tractor. The tank was tested for leaks and no defects were noted.

METEOROLOGICAL INFORMATION

WRECKAGE AND IMPACT INFORMATION

The responding Federal Aviation Administration (FAA) inspector reported that the airplane came to rest facing south and a post impact fire consumed most of the fuselage and the inboard sections of the wings (figure 1). The impact marks at the accident site indicated that the airplane impacted the ground in a nose-low, vertical attitude, and then came to rest upright. The engine was buried in the mud and only one propeller blade was visible.

A postaccident examination of the airplane revealed that the forward portion of the fuselage, including the engine compartment, was crushed aft. The leading edges of both wings were crushed aft from the leading edge to the main spar along the entire wing span. The outboard portions of both wings exhibited chordwise crushing and buckling. The inboard sections of the wings containing the fuel tanks were consumed by fire.

The pilot's seat frame was found intact and connected to the fuselage seat rails. All mounting points of the 4-point pilot harness remained installed. The harness webbing had been consumed by fire, but the seat belt buckle assemblies were found in the wreckage and were unclasped. The pilot's helmet did not exhibit any abnormal wear or damage.

According to the FAA inspector the empennage and associated control surfaces had been in their respective positions and intact before recovery. Both elevators remained attached to the horizontal stabilizers and the trim tabs remained in place on the elevators.

All flight control surfaces were found in their respective positions within the wreckage. The flight control cables and components were traced through the wreckage to the fullest extent possible. The elevator and rudder controls were found to be continuous except for the portions of the controls that were consumed by fire. The aileron controls exhibited multiple tension overload separations and some portions were consumed by fire. There were no preimpact flight control anomalies found that would have precluded normal operation.

A portion of the flap actuator assembly was found in the wreckage. The flap actuator shaft was extended to a point that corresponded to 22° of flap extension.

The firewall forward portion of the fuselage had separated from the remainder of the fuselage and exhibited rearward crushing signatures. The engine and propeller remained attached to the engine mount and firewall and sustained impact and fire damage. The cockpit engine control quadrant was found with significant fire damaged, but all three push-pull cables remained attached. The remaining length of these cables was traced to the extent possible with no anomalies noted. The preimpact position of the engine controls could not be determined.

The propeller spinner exhibited torsional deformation and spiral scoring of the propeller piston was noted. The propeller assembly was found mostly attached to the engine's propeller flange and two of the three blades remained attached. The third blade was separated and found in the wreckage debris. The propeller blades were labeled A, B, and C for report identification purposes only. Blade A fractured from the hub assembly and its tip also fractured and separated. Blade B was bent forward and had rotated in the clamp toward a high pitch setting. Blade C exhibited slight bending/twisting and leading-edge gouges. All 3 of the propeller blades exhibited chordwise abrasions near the leading edges. All 3 of the propeller counterweights remained in a similar position. None of the blades were bent aft to any remarkable degree.

MEDICAL AND PATHOLOGICAL INFORMATION

The pilot died in the hospital on December 3, 2017. The pilot's mother stated that the pilot died due to health complications as a result of the injuries sustained in the accident.

ADDITIONAL INFORMATION

AT-502B Airplane Flight Manual - AGRICULTURAL FLYING

"Pull-ups: Prior to pull-up apply additional power smoothly. Abrupt pull-ups should be avoided since excessive speed is lost which reduces turn performance. When making pull-ups over wires avoid starting to bank too soon.

Turns: The previous training and experience will influence the operator flying the AT-502B. All conventional types of turns may be performed in the AT-502B. Flaps may be used as a turning aid providing small deflections are used (5° to 8°). The usual method of using flaps is to make the pull-up and initial bank with flaps retracted. As the airplane is being banked to turn back into the field touch the flap switch briefly and let off a little back pressure on the stick, as the flaps cause a slight pitch up tendency. Continue the turn, and as you line up for your pass, retract the flaps. Make coordinated turns. Use the slip indicator as a means of determining whether or not you are carrying bottom rudder. The AT-502B has excellent stall characteristics and if the airplane is inadvertently placed in an impending stall situation, it is only necessary to relax some back pressure on the stick to make recovery, and little altitude is lost, providing the turn is coordinated. A stall from a skidding turn will result in the nose dropping sharply with a significant loss of altitude."

Flap Extension in Agricultural Turns

According to the airplane manufacturer, extending more than the recommended 5° to 8° of flaps in a turn allows for a tighter turn as it slows the airplane faster and increases the maximum lift coefficient of the wing. In this situation the airplane has reduced pitch stability and the effectiveness of the elevators and rudder is reduced by spoiling the airflow over the control surfaces in some attitudes. Also, the airplane's lower airspeed reduces the amount of inertia/momentum available to be used for recovery from any inflight upset or loss of control.

Airplane owner statement

The airplane owners stated that the typical procedures for this type of flight was to produce a line of smoke from the airplane's smoker during the turns between spray passes. A pilot would use the position of the smoke to determine the wind direction and then plan the next flight path. The owners used the pilot's previous flight worksheets to estimate the elapsed time to complete each turn after a spray pass. They determined that the pilot would have had to make 8 to 10 second turns between spray passes in order to match the times reported on the worksheets. They added that a normal turn should take about 30 seconds, so they think the pilot was doing something to make his turns a lot faster and a lot tighter. A hammerhead type turn is a maneuver pilots can use to decrease turnaround times. Also, the use of flaps in a turn is up to pilot preference. Some pilots make slow flat turns with no flaps. Some pilots make quick turns with flaps extended, although it's not a recommended practice.

Garmin aera500 GPS data

A Garmin aera500 handheld GPS was found in the wreckage and was sent to the NTSB Recorder Laboratory for download. A successful unit download yielded accident flight data and data from several previous flights.

Data from the handheld GPS revealed that the airplane had circled over the field being treated then made 4 east-west spray passes near the north side of the target field. The final data point was captured on the east side of the target field and heading westbound. The data did not reveal the very end of the flight where the airplane was flying northbound near the accident site, as reported by witnesses. Figure 2 shows the accident flight track with the accident site and the final recorded data point, which was at 08:12:33 CDT, at 189 ft agl, and 95 knots. The other data points are noted in coordinated universal time (UTC) and altitude in mean sea level (msl).

The GPS data revealed that four turns were 24 seconds, 18 seconds, 22 seconds, and 18 seconds for an average of 20.5 seconds. The standard turnaround for a spray pass in an AT-502B is about 30 seconds. The peak altitude in the four turns was 369 ft agl, 402 ft agl, 422 ft agl, and 500 ft agl. The peak altitude during a standard turnaround is 250 to 300 ft agl.

NTSB Probable Cause

The pilot's improper decision to execute a tight turnaround with excessive flap extension during low-altitude agricultural operations, which resulted in an aerodynamic stall with insufficient altitude to recover.