19990525005649A

Acft crashed under unknown circumstances during aerial application, the pilot/sole occupant suffered fatal injuries, the acft has substantial damage, other circumstances are unknown.(.19) on may 25, 1999, approximately 1720 central daylight time, a pzl-mielec M18A (dromader), N8199W, was substantially damaged following a power loss during takeoff from Sheffield-Smith Airstrip, Altus, Oklahoma. The commerical pilot, the sole occupant, was fatally injured. The airplane was owned by the pilot and operated by pitts ag flying, inc., under title 14 CFR part 137. Visual meteorological conditions prevailed for the local aerial application flight which was originating at the time of the accident. No flight plan had been filed. According to a witness, the "airplane's takeoff roll appeared longer than normal." He said that he "saw a white plume as the airplane dumped its load, and then it nosed over and hit the ground." The airplane came to rest inverted, crushing the vertical stabilizer and the cockpit canopy. (.4)the dromader was departing from an 1,800 foot runway with a 250 foot overrun. The airplane was estimated to be 273 pounds overweight, and the density altitude was 3,244 feet. The pilot had set his flaps at 9 degrees, although other operators of the dromader recommended 15 to 20 degrees of flaps for heavy gross weight takeoffs. The manufacturer's performance charts indicate that 1,800 feet is needed for a 10 degree flap takeoff under these conditions. A witness said that the airplane's engine was running smoothly, but the ground run appeared unusually long, and he saw it hit a small earthen berm at liftoff. He said the airplane popped up, then down, up again, and then nosed over onto its back. The airplane was found with its left main wheel separated, the crew compartment collapsed, the gate box (dump doors) closed, and approximately 510 gallons of applicant in the hopper. The engine was test run in its fuselage and operated normally with the exception of a 'popping' noise heard on its fourth run. Two exhaust valves were found heat blued, and one of the valves had a rub mark down its stem suggesting that it might have been stuck on some occasion. (-23)aircraft was on takeoff with approximately 520 gallons of chemical on board. Eye witness stated that "the airplane roll appeared longer than normal." The witness saw the pilot dump his load then the aircraft struck the ground and nosed over. The aircraft came to rest inverted crushing the vertical stabilizer and the cockpit canopy.