DEN99FA086

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.

History of flight

On May 25, 1999, approximately 1720 central daylight time, a Pzl Mielec M-18B (Dromader), N8199W, was substantially damaged after it settled to the ground following takeoff from Sheffield-Smith Airstrip, Altus, Oklahoma. The commercial pilot, the sole occupant aboard the airplane, was fatally injured. The airplane was being 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.

An employee of the pilot said that the pilot had flown two flights previously that day. The first flight departed about 0800 with 550 gallons of applicant and returned at approximately 0945. The pilot departed on the second flight at approximately 1130, with approximately 300 gallons of applicant, and landed about 1230. When the airplane landed the second time, it was immediately refueled and put in the hangar because there were no further scheduled jobs that day. The employee further reported that later in the day, he received a cellular telephone call from the pilot who said that he had received an additional work order for 507 acres.

A witness reported watching the pilot perform a preflight engine run-up, and he said the airplane sounded "OK" to him. He said the pilot began his takeoff roll to the south at approximately 1715. He further stated that during the takeoff roll the engine sounded smooth, but he thought the ground run looked longer than normal. The witness said that he saw a "puff" of what looked like smoke or dirt around the main landing gear wheels as the airplane lifted off the ground. He stated that the airplane got about 30 to 35 feet above the ground and then "tilted forward with the tail coming up." He said that "the airplane began dumping its load," then banked to the right, followed by a left bank. He said that "the nose dropped, and the plane went right on over."

Another witness located 1 mile to the east stated that he saw the airplane at approximately "one telephone pole height" (approximately 35 feet). He then saw the airplane dip down towards the ground and "pop" back up to about "half a telephone pole height." The next thing he saw was a misty spray as the airplane began dumping its load. The witness noticed that as the herbicide was released, there was no apparent "pop-up" in the airplane's flight path. It then "wobbled" from side to side with the right wing low and then the left wing low. The witness saw the airplane's nose drop, and then it went right on over onto its back.

Personal information

The pilot's flight logbook indicated that he started his flight training on August 25, 1992, and completed his commercial pilot certificate ride on October 9, 1995. He received his Airframe and Powerplant certificate on April 7, 1997. He took possession of the Dromader on December 30, 1998, and had accumulated approximately 65 hours of flight experience in it at the time of the accident. His total flight experience was approximately 2,875 hours.

The pilot had been doing aerial application work since the 1996 season, and he had accumulated an estimated 2,591 hours of application flight time. He flew a Grumman/Schweizer G-164B (known as an Ag-Cat) until he purchased the Dromader. The Ag-Cat (N6903K) had a maximum gross weight of 6,075 pounds, and was powered by a 450 horsepower engine.

Aircraft information

The airplane was a single engine, propeller-driven (variable pitch), aerial application airplane, which was manufactured in July 3, 1998, by Pzl Mielec (in Poland). It was certificated for a maximum gross weight of 9,260 pounds, which was raised to 11,700 pounds in accordance by STC SA01276AT. The airplane was flown primarily single occupant, but did have a seat behind the pilot. The airplane was powered by a WSK Pzl Kalisz ASz-62IR-M18 supercharged (single speed centrifugal), nine cylinder, radial, reciprocating, air cooled, carbureted engine which had a maximum takeoff rating of 967 horsepower. The engine's fuel air mixture was controlled in the carburetor by an aneroid atmospheric pressure sensor (the pilot has no mixture control lever). At the time of the accident, the airframe had accumulated approximately 84 hours.

The airplane had a wingspan of 58 feet, and was 31 feet in length. The dispensing hopper was 88 cubic feet in size, or it could hold 660 gallons of liquid. The engine used between 95 and 105 gallons of fuel per hour for takeoff, but several application operators, who flew Dromaders, reported that they averaged about 65 gallons per hour of fuel burn. These operators further reported that the Dromader requires "heavy stick forces" to fly, hence the pilots that fly Dromaders are known to develop "Popeye arms."

A Dromader distributor said that the center of gravity in a Dromader is a short distance from the empennage flight controls (short coupled), and proper trim settings are very important. He said that "when flying the Dromader, the pilot must be very careful not to try to get the airplane off the ground early or it could add as much as 500 feet to the takeoff roll." He said that the trim must be forward for takeoff, and the airplane is essentially landed with the use of incremental aft trim. An agricultural applicator in Nebraska said that during one of his first flights in a Dromader, he landed without the aid of trim, and the stick forces required all his strength (using both arms and both legs) to land.

Several operators of the Dromader said that the airplane requires a large left rudder force for takeoff due to the high torque forces produced by the engine at maximum power. They said that if the airplane's throttle is rapidly reduced, as in an aborted takeoff, the left rudder force must be correspondingly reduced, or the empennage will be rapidly displaced to the right.

According to the airplane's manufacturer, the pilot may choose the takeoff flap setting according to the runway length and aircraft weight. Several Dromader operators in the field reported that they routinely used 15 to 20 degrees of flaps for their takeoffs. A distributor and flyer of M-18B Dromaders said that he normally uses 15 to 20 degrees of flaps for a high gross weight takeoff which permits him to get airborne in a much shorter ground roll.

The aircraft maintenance records indicate that an engine driven air-conditioner system was installed on December 31, 1998 (tachometer time of 31.7 hours). Witnesses stated that during this installation, a maintenance "rag" was left inside the engines crankshaft. The pilot's father said that within a few hours of the air-conditioner installation, the propeller stopped cycling properly, and the pilot requested a new engine from the manufacturer. The pilot and another mechanic installed the new engine on March 27, 1999 (tachometer time of 44.2 hours).

The maintenance man that assisted the pilot in installing the new engine said that the pilot installed the original carburetor on the second engine. A Pzl Melec factory representative said that their automatic mixture adjusting carburetors may be interchanged between any Pzl Kalisz engine. He added that the Pzl Kalisz carburetors require periodical inspection every 200 hours. The above mentioned maintenance man said that the original propeller and oil cooler were used on the second engine. He said that the pilot told him that he was going to clean the oil cooler with a pressure washer and solvent. He did not observe the pilot perform the oil cooler flushing.

The estimated weight of the airplane at the time of takeoff was calculated to be 11,973 pounds (see attached computation document), which was 273 pounds over the maximum allowable gross takeoff weight of 11,700 pounds. Using the Pzl M-18A takeoff ground roll performance chart for 10 degrees of flaps, the airplane wou