DEN06GA128

The airplane was being used for mosquito control and was carrying Scourge insecticide (Bayer), a mixture of resmethrin, piperonyl butoxide, and naphtalene. A witness said the airplane passed overhead at low altitude. He heard the engines "throttle back, then rev up and sputter." He said he could tell the right engine was sputtering because "the propeller was turning slowly." He saw the airplane pitch up, roll to the right, and descend into the ground. The airplane immediately caught fire. The on-scene investigation revealed one blade on the left propeller assembly was curled aft and the other blade was curled forward. One blade on the right propeller assembly was curled aft and the other blade was straight. Both engines later were disassembled and inspected. Crankshaft rotation produced camshaft, valve, and accessory drive continuity on both engines. No anomalies were noted with either engine's lubrication, induction, fuel injector, exhaust, and ignition systems. Examination of the spark plugs and cylinders revealed normal burn patterns and color. All cylinders produced compression except the right engine's number 6 cylinder. According to the manufacturer, its intake and exhaust valve springs had lost tension as a result of having been exposed to the fire. Both the left and right propeller governor controls were in the high rpm position.

History of flight

On September 14, 2006, at 1953 eastern daylight time, a Piper PA-23-250, N5941Y, registered to and operated by the Polk County, Florida, Board of County Commissioners and piloted by an airline transport-certificated pilot, was destroyed when the airplane struck terrain while maneuvering near Fort Meade, Florida. Visual meteorological conditions prevailed at the time of the accident. The public use flight was being conducted under the provisions of Title 14 CFR Part 91 without a flight plan. The pilot and observer were fatally injured. The local flight originated at Bartow, Florida, approximately 1900.

According to Polk County officials, the airplane was being used for mosquito control. The only known witness to the accident was sitting in his car with his wife in an adjoining park. The witness said the airplane passed overhead at a low altitude. He heard the engines "throttle back, then rev up and sputter." He saw the airplane pitch up and roll to the right. The airplane hit the ground and caught fire. The witness was later interviewed by telephone. He stated that as the airplane passed overhead, he could tell the right engine was sputtering because "the propeller was turning slowly."

The accident occurred during the hours of daylight at a location of 27 degrees, 17.82' North latitude, and 81 degrees, 26.41' West longitude, and at an elevation of 92 feet msl (above mean sea level).

Personnel (crew) information

The pilot, age 71, held an airline transport pilot certificate, dated May 12, 2004, with an airplane multiengine land rating, and commercial privileges in airplanes, single engine land and sea. He held a flight instructor certificate, dated May 6, 2006, with airplane single/multiengine and instrument ratings, and a ground instructor certificate, dated May 12, 2004, with advanced and instrument ratings. He also held a mechanic certificate, dated May 12, 2004, with airframe and powerplant ratings. His second-class airman medical certificate, dated May 5, 2006, contained the restriction, "Must wear corrective lenses for near and distant vision." When the pilot applied for medical certification, he estimated his flight time to be 26,000 hours, of which 150 hours were accrued in the previous six months.

The passenger was not a rated pilot, but served as an observer for the pilot during spray runs.

Aircraft information

The Piper Aircraft Corporation manufactured N5941Y (serial number 27-3107), a model PA-23C-250, in 1965. Two Lycoming IO-540-C4B5 engines (serial number L-2672-L18, left; L-15482-48A, right), each rated at 250 horsepower, drove two Hartzell 2-blade, all-metal, full-feathering, constant speed propellers (model numbers HC-E2YK-2RB3F, left; HC-C2YK-2RB3F, right).

N5941Y was given to Polk County after it was confiscated for transporting illegal drugs. On June 15, 1995, it was extensively modified: All but the front seats were removed, the nacelle tanks were converted to chemical tanks, and spray booms were added to both wings. According to the maintenance records, the airframe and both engines and propellers were given annual inspections on February 6, 2006, at a tachometer reading of 2,779 hours. The right engine was overhauled on April 12, 2002, and had accrued 352 hours at the time of the last annual inspection.

Meteorological information

Weather recorded at Lakeland (LAL) Florida, located XX miles from the accident site, was as follows: Wind, 270 degrees at 5 knots; visibility, 12 miles; sky condition, few clouds at 4,000, scattered clouds at 25,000 feet; temperature, 29 degrees C.; dew point, 22 degrees C.; altimeter, 29.90 in. Hg.

Wreckage and impact information

The on-scene investigation revealed broken limbs from a small tree. A trail of flattened grass, 60 feet in length and on a magnetic heading of 182 degrees, led from the tree to the wreckage. The airplane rested upright against an earth berm. The berm was aligned on a magnetic heading of 302 degrees and the airplane was aligned on a magnetic heading of 317 degrees. The left wing remained attached. The flaps and landing gear were retracted. Flight control continuity was established. The right wing was torn off just outboard of the engine.

Examination of the cockpit revealed the left throttle and mixture control were full forward. The right throttle was in the mid-range position, and the right mixture control had over-traveled past the idle cutoff position. Both alternate air controls were in the off position.

One blade on the left propeller assembly was curled aft, and bore chord wise scratch marks, and signatures consistent with torsional bending. The other blade was curled forward. One blade on the right propeller assembly was curled aft, and bore signatures consistent with torsional bending. The other blade was relatively straight.

Medical and pathological information

Autopsies were performed on the pilot and passenger by the Polk County Medical Examiner's Office. According to the autopsy reports (2006-10-FA-438 and 439), both men died "as a result of multiple blunt force traumatic injuries." A toxicology screen revealed the presence of metoprolol (Lopressor, Toprol), a beta-blocker anti-hypertensive medication, in the pilot's urine.

FAA's Civil Aeromedical Institute (CAMI) in Oklahoma City, Oklahoma, performed toxicological screens on specimens from both the pilot and observer. According to CAMI's reports, there was no evidence of carbon monoxide, cyanide, ethanol, or drugs in the pilot's blood, and no evidence of carbon monoxide or cyanide in the observer's blood.

Tests and research

On October 2, 2006, the engines were partially disassembled and inspected at the facilities of Quality Enterprises, Groveland, Florida. The left engine's lubrication, induction, fuel injector, exhaust, and ignition systems were examined. No anomalies were noted. Crankshaft rotation produced camshaft, valve, and accessory drive continuity. All six cylinders produced compression. Examination of the spark plugs and the number 5 cylinder revealed normal burn patterns and color.

The right engine's lubrication, induction, fuel injector, exhaust, and ignition systems were examined. No anomalies were noted. Crankshaft rotation produced camshaft, valve, and accessory drive continuity. Five of the six cylinders produced compression. The number 6 cylinder had low compression because the intake and exhaust valve springs had lost tension as a result of having been exposed to the fire. Examination of the spark plugs and the number 6 cylinder revealed normal burn patterns and color.

Both the left and right propeller governor controls were in the high rpm position.

Additional information

In addition to the Federal Aviation Administration, parties to the investigation were the New Piper Aircraft Corporation and Textron Lycoming.

The wreckage was released to Polk County on October 23, 2006.