BUFFALO, MO, USA
N6254Z
Piper PA-25-150
The Piper PA-25 (acft), being used to develop an STC, was modified by installing 2nd seat in hopper area & extending canopy forward. On 6/30/95, operator reported to FAA that flight conformance testing to date had reflected no change in acft performance versus original configuration. Acft was equipped with external airspeed calibration device for an airspeed calibration flight, & it was loaded with 560 lbs of ballast to meet max gross wt & forward CG requirements for STC testing. Wind was gusty, & temp was 64 deg (about 30 deg warmer than on day of previous test flight). Pilot reported that after takeoff from runway 21, he maintained best rate of climb speed & 2525-2550 engine rpm, then best angle of climb speed, but acft would not climb. He then turned downwind & attempted to return to same runway; however, acft collided with trees & crashed about 1/2 mi east of airport. A witness said that during takeoff, acft lifted off, then began a left turn about half way down the runway. Pilot said that a climbing turn was made to allow for more clearance from obstacles at south end of airport. Witnesses said acft then turned north & remained at low altitude & airspeed until it hit trees & crashed. Fire then erupted, & acft was demolished. Investigation revealed that standard (original) wing root & landing gear (strut) fairings were not installed. Piper reported that removal of wing root fairings would significantly reduce wing lifting capability & change airflow over horizontal tail, requiring more elevator deflection for maneuvering. Absence of landing gear fairings would have increased drag, slightly.
HISTORY OF FLIGHT On April 24, 1996, at 1107 central daylight time (cdt), a Piper PA-25-150, N6254Z, registered to D and E Company, Republic, Missouri, and piloted by an FAA test pilot, was destroyed by an impact with terrain, and a post crash fire. The airline transport pilot sustained serious injuries and the Federal Aviation Administration (FAA) flight engineer received fatal injuries. The purpose of the flight was for a Supplemental Type Certificate (STC) approval on the airplane. The 14 CFR Part 91 flight was operating in visual meteorological conditions. No flight plan was on file. The test flight originated from Buffalo, Missouri, at 1105 cdt. The airplane was used by a private individual who had developed a STC for a dual seated Piper Pawnee 150. The purpose of this flight was to perform airspeed calibrations at the maximum gross weight with a forward center of gravity (CG). Seven (7), eighty pound bags of dry concrete had been placed in various locations on the airplane as ballast. The total fuel tank capacity is forty gallons. The pilot elected to takeoff with thirty-five gallons of automotive fuel to compensate for the extra weight of the calibration equipment. According to the pilot's written statement and interviews, he said he conducted one training flight on February 29, 1996, followed by a second flight which entailed an airspeed calibration test on the same day. The third flight was conducted on March 1, 1996. This flight consisted of stalls and climb performance tests. The pilot and flight engineer calculated a weight and balance for the third flight to load the airplane at a maximum gross weight and with a forward center of gravity. The pilot was unable to explain why the airplane was configured that way since the hopper had been removed. The temperature for the first three flights was 28 to 32 degrees fahrenheit. The pilot said it lacked overall performance but felt comfortable with the airplane. The fourth flight was conducted on April 24, 1996, the day of the accident. The temperature that day was 64 degrees fahrenheit. The airplane was modified to accommodate an external airspeed and static bomb which was routed around the forward right battery compartment door and hung down between the landing gear. The flight engineer would hold the airspeed bomb by a reel in his lap and unravel the airspeed bomb inflight to perform the airspeed calculation tests. The pilot said that the runup was normal. The takeoff was at the same spot on the runway as all the previous flights conducted. He said the takeoff was normal but as he maneuvered to stay clear of some objects south of the runway, the airplane felt as if it was not climbing but sinking. He said he maintained the best rate of climb airspeed of 70 MPH and 2525 to 2550 engine RPM. He then went down to the best angle of climb airspeed of 63 MPH. He felt the airplane was not climbing and began to turn downwind for landing. The pilot stated, "...Sink increased such that I would not reach the airport. Airplane contacted trees prior to reaching field... ." The pilot's weight and balance sheet indicated a gross weight of 2,331 pounds at a CG of 10.99 inches aft of datum. The pilot's weight and balance is included as a supplement to this report. A witness reported seeing the airplane takeoff on runway 21 and stated, "He wasn't very high over the park, but was kind of flying through the clearing of the trees. ... As the plane was coming closer to my house I thought he was going to hit the tree in my front yard. ...[the airplane] almost clipped a tree in my neighbors yard. ...When they were flying north [downwind to runway 21], they flew over the top of [neighbor's house down the street] house. They missed his house by probably 2 or 3 feet... ." The witness remembered hearing two boom sounds after the airplane disappeared behind the trees. A second witness also stated that after takeoff, "...the engine sounded good, but it sounded like it was laboring... ." The airplane turned downwind and disappeared behind the trees. A third witness who is an employee of the STC holder was interviewed by a FAA Principal Operations Inspector and said in his written statement, "...(airplane) went down the runway and lifted off. It looked like the airplane was having trouble getting enough lift to go. After they lifted off and got about 1/2 way down the runway, they turned left. The aircraft appeared to porpoise slightly as if it was stalling out. As they got maybe 1/4 mile east of the airport, they turned downwind and the aircraft stopped climbing and started sinking, wings level, nose slightly up, engine full power... ." The pilot had flown the airplane about 6 weeks earlier in the same weight configuration and seemed happy with it, however, the previous time, it was a much colder day... ." The company's test pilot for the STC holder was interviewed by the FAA Principal Operations Inspector and stated in his written statement that, "...according to his experience in the PA-25-150, the aircraft was loaded with the center of gravity too much forward. He further stated that he had not flown the aircraft nor would he have flown the aircraft loaded in this fashion... . He said as the company test pilot, that he flew the aircraft 20 to 25 times (without the seven, 80 pounds bags of quikcrete) and that all appeared normal. He said that he had calibrated the airspeed to within 1-3 NM per hr but that the FAA wasn't satisfied with that and wanted to test it more... ." The test pilot also commented on the fact that the airplane was not outfitted with a standard wing root fairing. Without this fairing the drag coefficient of the airplane is increased and it also affects the stall characteristics. The company test pilot said the reason why he would not fly the airplane loaded the way the FAA test pilot had it loaded was because the ballast could not be dumped if an emergency occurred inflight. PERSONNEL INFORMATION The pilot was born May 9, 1946. He was the holder of an airline transport pilot certificate for single engine land/sea and multi- engine land ratings. He held a second class medical issued on May 5, 1995. His most recent biennial flight review was on April 19, 1996. He had accumulated a total of 3,296 hours of flight time, 3 hours of which were in Piper PA-25-150 airplane at the time of the accident. AIRCRAFT INFORMATION The airplane was a Piper Pawnee manufactured in 1960, serial number 25-314. The airplane's airframe and engine logbooks were in the airplane at the time of the accident, consequently, the logbooks were destroyed by the post crash fire. According to the STC application dated on February 26, 1996, the airframe had accumulated 3,068 hours time in service. The engine had 1,591 hours total with 38 hours since its last overhaul. WRECKAGE AND IMPACT INFORMATION The NTSB on-scene investigation began at 0800 cdt on April 25, 1996. The wreckage was located one-half mile east of the Buffalo Airport, in a hilly wooded area. The accident site was the highest elevation in the vicinity of the airport. The airplane impacted numerous trees during its descent, leaving the right wing tip in a tree and pieces of wing ribs along the ground. The airplane came to rest almost upright with a slight left wing low attitude. A post crash fire engulfed the airplane. The right wing was bent aft and lay along the right side of the fuselage with numerous impacts to the forward spar. Most of the right wing ribs were destroyed and burned away. The front and rear wing attach points were secure. The left wing was destroyed by multiple tree impacts and post crash fire. The left wing ribs had melted and were deformed by the fire. The fuselage was found on its left side on top of the left wing. The occupiable space in both the front and rear cockpit area was not compromised. The front seat was welded to the frame and was cut loose during removal of the flight engineer. The seat belt and shoulder harness attach points were not evident for the front seat passenger; however, the five-point seat and shoulder belt buckle was found fastened near the front seat. The rear seat was found attached to the seat tracks, but the supporting structure had burned away. The rear seat belt cables and attach points were secure and in place. Dual flight controls from a Piper Cub, PA-18 had been installed. The empennage exhibited compression bending to the lower longerons and the fabric had been destroyed by fire. The horizontal stabilizer fabric, elevator fabric, vertical stabilizer fabric and rudder fabric were all destroyed by fire. Control continuity was verified to the elevator and rudder. The elevator trim spring was in place, and the trim cable was connected to the trim control located in the cockpit area. Engine controls were provided to the front seat passenger by means of metal rods extended from the rear seat occupant's engine controls. The elevator trim handle was relocated between the seats to allow access by both occupants. The center flap handle was not accessible to the front occupant, but only to the rear seat occupant. Flight control continuity to the ailerons and flaps was verified. All flight and engine instruments were destroyed by the post crash fire. The engine was turned by way of the propeller and continuity was established through all pistons and the accessory section. The propeller was attached to the severely damaged propeller flange which was still partially attached to the crankshaft. An outboard propeller blade section approximately 15 inches long had been sheared off. This section of the propeller was sent to the NTSB Materials Laboratory Division. See enclosed Metallurgist's Factual Report. Numerous pieces of hardwood (oak) were found with clean cuts that appear to have been made by the propeller. Some pieces of tree limbs were found as thick as 5 inches in diameter. The IIC calculated a forward speed of 36.2 MPH from one of the wood pieces found near the impact crater. MEDICAL AND PATHOLOGICAL INFORMATION A post mortem examination of the FAA Flight Engineer was conducted on April 25, 1996 at Cox South, Springfield, Missouri. No pre-existent anomalies were noted during this examination. TESTS AND RESEARCH The airspeed indicator was ordered by the FAA Test Pilot to be calibrated after the flight that was conducted on March 1, 1996. The airspeed indicator had a functional test performed by Aero-Mach Labs, Inc., of Wichita, Kansas, on March 5, 1996 and they reported their findings to the pilot. The airspeed indicator was later reinstalled into the airplane and a leak check was performed on the pitot-static system. ADDITIONAL DATA The IIC calculated the experimental airplane's weight and balance to indicate a gross weight of the airplane to be 2,319 pounds and the center of gravity to be approximately 10.87 inches aft of datum at the time of the accident. The purpose of the flight testing was to bring the airplane back into compliance as a Piper Pawnee through the STC. The pilot operating handbook for a Piper PA-25-150 specifies a center of gravity envelope at maximum allowable gross weight (2,300 lbs) is 11.70 to 15.25 aft of datum. The Piper Pawnee is also rated at 150 HP at 2,700 RPM. See also the enclosed Piper Aircraft's estimated weight and balance sheet. Parties to the investigation were the Federal Aviation Administration; The New Piper Aircraft Corporation; Textron Lycoming. Following the on-scene portion of the investigation, the wreckage was released to owner on April 25, 1996.
failure of company/operator personnel to install the wing and landing gear (strut) fairings after modifying the airplane for a supplemental type certificate (STC), and improper planning/decision by the pilot. Factors relating to the accident were: the airplane's reduced performance, and high obstructions.
Source: NTSB Aviation Accident Database
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