20190820013909A

At approximately 09:16 am on August 20th, 2019 a single pilot Grumman ag cat model G-164B serial number 765B aerial application aircraft took off east from a private airstrip for an aerial application mission loaded with 155.8 gallons of insecticide for the first spray of the day. Travel to the application site required the aircraft to turn nearly 180 degrees back to the west immediately after take-off. The weather conditions were clear with a light wind (approximately 8 mph) from the south temperature was around 80 degrees. Shortly after take-off, the ground crew witnessed smoke in the distance and could no longer see or hear N3631Z in flight. No witnesses came forward to describe the actual event.

The accident site is located approximately .6 miles and about 40 degrees north of the end of the east/west private airstrip from which the flight originated. The on scene investigation discovered impact damage consistent with a low altitude stall spin. First contact with the ground is evidenced by light ground scars dissecting the sandy country road at about a 45 degree angle. Two long ground scars in particular appear to have been made by the left wings (aircraft is a bi-wing) with additional scaring made by either left main gear or tail noted. Yellow paint transfer was discovered in the road scars. The small radius of the aircraft debris field evidences a nearly vertical ground impact. The near vertical impact is also evidenced by both left and right wing leading edges being ?crushed? In a near head on manner from the wingtips to the spars. Further evidence of a near vertical impact include mud and grass smashed into the cooling fins of the bottom engine cylinders as well as crushed exhaust pipe indicating a very hard engine/nose impact driving the bottom of the engine back toward the firewall. The aircraft came to rest after spinning to the left (tail to the right) with the wings coming to rest pointed perpendicular to the road back in the direction of the airstrip. Weight and momentum of the fuselage carried it around in a left rotation until the fuselage tail was closer to the right wings then the left. The fuselage rolled to the right in the direction of momentum until nearly upside down with the tail gear wheel pointing into the air at about 120 degree angle from the ground.

During the ground impact, the 9 cylinder radial engine broke free of the engine mounts and continuing in the direction of travel landing upside down (number 1 cylinder facing straight down) facing away from the aircraft between the fuselage tail and right wing tip. The propeller was found with one blade bent straight back. The bend in the blade originated about a foot from the hub and went 90 degrees backward. The other blade was found in near normal configuration with the outer third imbedded into the soft ground/mud. Grass and dirt found impacted/forced into the gland nut and under the propeller hub once again indicating the aircraft made a nearly vertical impact.

Post-crash fire consumed much of the cockpit flight controls of the aircraft making post accident flight control continuity check difficult to determine. If new evidence is discovered in a post-accident engine tear down this report will be modified to incorporate the new evidence.