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N8199W accident description

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Tail numberN8199W
Accident dateMay 25, 1999
Aircraft typePZL-Mielec M-18B
LocationAltus, OK
Additional details: None

NTSB description

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 would have needed approximately 1,800 feet for takeoff at the time of the accident. If the pilot used a rolling takeoff technique, an additional 150 to 200 feet would be required. The pilot's employee said that the pilot departed at 0800 on the morning of the accident with a load of 550 gallons of applicant. From this departure time, to the time of the accident, the density altitude had increased from 2,056 feet, to 3,244 feet.

Several pilots who fly the Dromader M-18B said that anytime difficulty is experienced during the takeoff sequence, the first thing a pilot must do is "jettison his load." They said that the jettisoning sequence usually takes between 3 to 5 seconds. This reduces the gross weight substantially, which gives the pilot more opportunities to safely handle his airplane.

METEOROLOGICAL INFORMATION

The Air Force Base at Altus (elevation 1,381 feet, 030 degrees for 7 nm from the accident site) was reporting the following weather at 1659: wind 080 degrees for 11 knots, visibility 7 sm, cloud condition 4,500 feet scattered with cumulonimbus, 6,000 feet scattered, 30,000 feet broken, temperature 82 degrees F., dew point 64 degrees F., altimeter setting 29.89 inches of mercury, density altitude 3,276 feet. The density altitude at Sheffield-Smith Airstrip was computed to be 3,244 feet.

AERODROME INFORMATION

The Sheffield-Smith private airstrip (N34 degrees 34.10 minutes, W99 degrees 21.10 minutes; elevation 1,355 feet) was 1,800 feet by 25 feet of new black asphalt; runway 17 had an additional 250 feet of grass/gravel/earth over-run. There was an east-west agricultural farm road approximately 8 feet wide which crossed the south end of the over-run. On its south side was a dirt berm 18 inch high by 2 foot wide. Beyond this dirt berm was an open level cotton field which extended for approximately 3,170 feet.

WRECKAGE AND IMPACT INFORMATION

The airplane was found on a flat cultivated cotton field (elevation 1,355 feet) approximately 2,920 feet south of the departure end of runway 17 at Sheffield-Smith Airstrip (see photographs). The night after the accident, heavy rains fell in the area making the accident scene very muddy, and reduced the clarity of the ground scars (see attached wreckage diagrams). The airplane was found inverted and tail forward with its longitudinal axis at approximately 170 degrees. All of the airplane's major components were accounted for at the accident site. Flight control continuity was established for all control surfaces. The flaps, which are hydraulically operated, were found at 9 degrees. The left main wheel had separated from its strut, and was found approximately 200 feet further south.

The vertical stabilizer and rudder were crushed into the empennage. The horizontal stabilizers and both wings were not damaged, except for an 18 by 12 inch hole on the bottom of the left wing outboard of the left main landing gear. The fuselage exhibited no damage except the cockpit's protective cage was crushed forward, and the left side of the cockpit had been cut away by the fire/rescue personnel.

The Oklahoma State Police officer that was in charge of the rescue/recovery efforts said that none of the airplane's control levers, switches, or knobs were moved by rescue personnel. The throttle was found aft of mid-range; the propeller control was found at fine pitch; and the horizontal stabilizer trim was found full forward. The gate box door (emergency dump door) was found in the closed position. An estimated 510 gallons of applicant was found in the hopper (see photographs).

An 18 inch high dirt berm, which was located approximately 8 feet from the departure end of runway 17, had two indentations in it approximately 11 to 12 feet apart, and they were centered with the centerline of the runway. Another set of ground scars, located approximately 180 feet north of the inverted airplane, had two 20 foot long parallel scars with a third small ground scar east and north. These three ground scars suggest that the airplane's second bounce occurred with the airplane's tail wheel to the right of its right main wheel (see photographs and diagrams).

The airplane's four propeller blades remained attached to their hub. Two blades had been bent aft from their mid span, and two blades had been bent aft from their outer 20 percent point. All four blades exhibited 45 degree chordwise striations with varying degrees of blade polishing (paint removal). No "S" type blade bending was observed.

After the aircraft was removed from the accident scene, the engine was examined. No abnormalities which would have affected normal engine operation were identified. The engine was found to be full of clean oil; no metal or debris was found within its system (see attached reports). The spark plugs were removed and found to be exceptionally clean. The engine was test run on its airframe (four times), and on the fourth test run, a "popping" noise was heard coming from the engine. Subsequently, compression tests were performed on all cylinders, and cylinder number 2 was between 50 and 52 psi (see attached report for all cylinder readings).

MEDICAL AND PATHOLOGICAL INFORMATION

An autopsy was performed on the pilot by the Office of the Chief Medical Examiner, Oklahoma City, Oklahoma, on May 26, 1999. The autopsy report indicates that the cause of death was positional asphyxia.

Toxicology tests were performed on the pilot by the FAA's Civil Aeromedical Institute (CAMI) in Oklahoma City, Oklahoma. According to CAMI's report (#9900101001), the pilot's carbon monoxide and cyanide tests were negative, and no ethanol was detected in the vitreous. The drug acetaminophen was detected in the urine. This is an over the counter pain reliever and fever reducer found in Tylenol, and is approved for use while flying.

TEST AND RESEARCH

An A&P mechanic with Inspection Authorization, said that the Dromader's gate box (see photograph) door is a mechanically linked pilot operated system. He further stated that a hard landing [high vertical g's], or dragging the gate box door through soft soil, could momentarily actuate the system. The result could be the expulsion of an undetermined amount of the hopper box's applicant. To the casual observer, it might appear that the pilot had dumped his load. Examination of the accident site, the airplane's hopper, and witness statements indicate that that the pilot did not dump his load.

After the airplane was released, additional evaluation of the engine by representatives of the pilot's family revealed the following:

A. The cold valve clearances were measured, and were found to be: 1. .016 inch 2. .006 inch 3. .010 inch 4. .008 inch 5. .029 inch 6. .022 inch 7. .037 inch 8. .022 inch 9. .016 inch

[A manufacturer's representative said that cold valve clearance adjustment should be between .011 and .019 of an inch.]

B. Cylinders number 1, 2, and 3, were removed and two of the exhaust valve stems were found to be blued. The mechanic that removed them said that this was an indication that at some time they had been exposed to excessive heat. The number two valve, in addition to blueing, exhibited rub marks on the side of the stem, which the mechanic said indicated it might have been stuck at some time.

A distributor of the Dromader M-18B said that having a stuck valve in a Pzl-Kalisz engine in the first 500 hours is very unlikely. He further stated that the valves do need frequent adjustment during its first 200 hours of operation. Normally the engine's sound will change, telling the pilot to adjust the valves.

ADDITIONAL DATA

The airplane, including all components and logbooks, was released to the owner's insurance representative on February 8, 2000.

(c) 2009-2011 Lee C. Baker. For informational purposes only.