On June 29, 1996, about 0525 mountain daylight time, a Cessna A188B, operated by Northern Aero, Inc, Whitewater, Montana, collided with terrain in Opheim, Montana, during the takeoff roll and was substantially damaged. The commercial pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed and no flight plan had been filed. The aerial application flight was conducted under 14 CFR 137. The pilot stated that he loaded his airplane with 140 gallons of herbicide and 54 gallons of fuel in preparation for a local aerial application flight. He began to take off to the north on a 2,675-foot airstrip, after determining that light winds were from the southwest. After traversing about two-thirds of the runway without becoming airborne, the pilot elected to abort the takeoff. He then began another takeoff to the south from the opposite end of the runway. He stated that he selected "full flaps" for the takeoff. After traversing half of the runway, the airplane's tail "came up," and the airplane began to bounce up and down along the remaining runway length. The pilot reported that the airplane "was not responding" to his efforts to become airborne during the takeoff roll. The airplane overran the runway and impacted a berm. The airplane's tail section was substantially damaged. The pilot stated that he does not recall hearing any unusual engine noises, and he was not aware of any preimpact mechanical malfunctions. According to an FAA aviation safety inspector from Helena, Montana, the flaps were found in the fully extended (20 degree) position at the accident site. According to the airplane flight manual for the Cessna A188B, the flaps should not be placed beyond the 10-degree retracted position for a short field takeoff. The inspector also stated that the operator did not hold a valid agriculture operating certificate at the time of the accident.