20170802010269A

This was a research flight related to weather modification. The aircraft had a spray system that put an electrical charge on the water as it exited the spray boom. There were researchers on the ground collecting real time data from the aircraft. The flight began with 350 gallons (400 gallon capacity) of water in the hopper and the intent was to find uplifting conditions (thermals) to spray the water. Uplifting conditions for this flight which had lasted 2.0 hours, were not good, so pilot decided to return to the airport. The hopper still had 281 gallons of water which weighed approximately 2250 pounds. Pilot took this into consideration during the approach knowing that the aircraft was heavier than normal landings with an empty hopper. The remaining fuel on board was approximately 50 gallons. Beginning fuel load was 164 gallons. Pilot used 100 mph as approach speed and set 10 degrees flaps. There was a right crosswind of about 30 degrees at approximately 10 KTS. Pilot had right wing down and left rudder to keep the fuselage straight with runway. As pilot flared for landing, pilot leveled the wings, reduced power to idle, and touched down in a three-point attitude in a full stall with the fuselage straight down the runway. The touch down was right at the end of the threshold and beginning of the runway. The landing was harder than usual, aircraft did not bounce and continued straight down the runway for about 500 feet. The aircraft then began an un-commanded slow turn to the right. I applied heavy left braking and left rudder with no effect. The turn continued to the point where it entered a classic ground loop with fuselage making a reversal of less than 180 degrees. The side load broke the left landing gear off and the left wing settled to the ground and the prop hit the asphalt. The tailwheel did not break off.