HOLDEN, UT, USA
N91017
Piper PA-18-150
The first pilot, seated in the front seat of the public use airplane, was banking the airplane to the left while flying in close proximity to the ground over an open field in pursuit of running coyote. The first pilot was in the second phase of an agency training program. The second pilot, acting as a part-time instructor pilot/gunner and seated in the rear seat, was pointing a shotgun outside the airplane in an attempt to kill the coyote as per the agency's aerial hunting program. The airplane aerodynamically stalled during the maneuver and entered an uncontrolled descent; it impacted the ground in a near-vertical, inverted attitude and was destroyed. An examination of the airframe and engine did not reveal any evidence of preimpact mechanical malfunctions. The airplane was about 75 pounds over its published maximum gross weight, and the density altitude was about 6,500 feet during the accident. Unapproved modifications to the airplane and inadequate maintenance record keeping by the operator were found during the investigation. The second pilot's throttle handle was not installed in the throttle control at the time of the accident.
HISTORY OF FLIGHT On October 10, 1996, at 0755 mountain daylight time, N91017, a Piper PA-18-150, operated by the Utah State Department of Agriculture, collided with terrain during an uncontrolled descent and was destroyed near Holden, Utah. Both commercial pilots were fatally injured. Visual meteorological conditions prevailed and an agency flight plan had been filed. The public use flight had departed from Delta, Utah, about 0730, and was conducted under 14 CFR 91. According to the operator of the aircraft, the purpose of the flight was for the aerial hunting of coyotes in accordance with a state and federal government program know as the Animal Damage Control (ADC) program. The ADC program is a part of the United States Department of Agriculture's (USDA) Animal and Plant Health Inspection Service (APHIS). The flight had been scheduled as a result of reports from a local ranch owner that calves were being attacked and killed by coyotes on the ranch owner's property. The flight was manned by the first pilot (pilot-in-command), seated in the front seat, and the "co-pilot/gunner," (second pilot) seated in the rear seat. The co-pilot/gunner was also serving as an instructor pilot during portions of the flight. According to calendar book entries (copies of excerpts attached) made by the first pilot, he and the second pilot had flown for a total of 3.6 hours in the accident airplane one day previous to the accident. The entry, dated October 9, 1996, indicated that five coyotes had been killed, and that the crew had been on duty from 0700 until 1600, with the majority of the flying conducted in the morning. No entries indicating any aircraft anomalies were noted. Another entry under the same date was found to indicate that the airplane had received 25.5 gallons of 100 low lead gasoline by the first pilot. According to the operator, the airplane was typically "topped off" after each day's flying. On the morning of the accident, the first pilot and second pilot ate breakfast with an acquaintance at a restaurant. The acquaintance reported that the crew did not complain of any problems with themselves or the airplane. The crew then proceeded to the Delta Municipal Airport, where the airplane was based, and departed on the flight. According to an eyewitness (statement attached) who was riding in a truck about one mile east of the accident site: "All I saw was the wing span as [the airplane entered a nose dive] right into the dirt.... It didn't look like they had any control at all." Another witness in the truck said that he did not note any engine problems, and that the airplane "... was probably 20 feet from the ground when I saw it and it was going straight down nose first." No other witnesses were found that observed the airplane prior to the descent into the ground, and no radio distress calls from the airplane were reported. The airplane impacted an open field and was destroyed. The accident occurred during daylight conditions at the following coordinates: North 39 degrees, 08.15 minutes; West 112 degrees, 17.61 minutes. AIRCRAFT INFORMATION The accident airplane, a Piper PA-18-150, was manufactured in 1981. It had been owned by the Utah State Department of Agriculture, and operated by the cooperative USDA-UDA ADC Program since that time. It was powered by a single Lycoming 160-horsepower model O-320-B2B engine, and had been configured as an aerial hunting aircraft. The Safety Board collected and examined copies of maintenance records for the aircraft that were obtained from the operator. The examination revealed that the airplane had received an annual inspection on July 18, 1996, with no unresolved discrepancies noted. The airplane had logged a total of 7,944 hours at the time of the inspection, and had been flown for an additional 72 hours until the accident. The entry documenting the most recent annual inspection indicated that a factory overhauled Lycoming model O-320-B2B engine had been installed on the airframe on July 18, 1996. This engine replaced the original 150-horsepower Lycoming O-320-A2B engine that had been delivered with the airplane. According to the Type Certificate Holder Aircraft Specifications, the -B2B is not approved for use on the PA-18-150. No FAA form 337 was found for the installation of the -B2B. According to the operator, the FAA Salt Lake City Flight Standards District Office was informed of the installation but elected not to require an FAA form 337 for a major repair and/or alteration. Further review of the maintenance records revealed that the most recent weight and balance data sheet was dated May 4, 1987, when two FM radios were installed. According to Lycoming, the weight of the -B2B engine is 6 pounds heavier than the -A2B engine. No evidence was found to indicate that a modification to the airplane's weight and balance had been performed at the time of the installation. The maintenance record entries were found to document the installation of an intercom system in 1989, as well as an FM radio in 1996. No evidence was found to indicate that a modification to the airplane's weight and balance had been performed at the times of the installations. The aircraft was equipped with an "Automatic Flagman" ribbon dispenser unit mounted on the right main landing gear. No entries were found in the maintenance log book to document this installation. Based on the most recent weight and balance data sheet, estimated fuel load and subsequent consumption, weight records of both occupants, and estimated weights of the cargo and equipment found on board the airplane, the Safety Board computed what the weight and balance of the airplane would have been at the time of the accident (computation attached). The computation revealed that the airplane was about 75 pounds over it's published maximum gross weight of 1,750 pounds. No record of weight and balance for the accident flight was found, despite published agency requirements (excerpts attached). According to the New Piper Aircraft Corporation, the published stall speed of the Piper PA-18-150 in level flight, at maximum gross weight, flaps up, at sea level, is 43 miles per hour. The stall speed would increase with an increase in gross weight and/or bank angle. PERSONNEL INFORMATION First Pilot Information. The first pilot, age 41, seated in the front seat, held an FAA commercial pilot certificate with a rating for airplane single-engine land. According to FAA records, the pilot was issued an FAA Second Class Medical Certificate on February 22, 1996, with no limitations. The first pilot's personal flight log books and ADC training records (copies of excerpts attached) were recovered and examined by the Safety Board. According to entries found in the log books, the pilot had logged a total of 586 hours of flight time, including 460 hours of pilot-in-command time in the Piper PA-18-150, at the time of the accident. Prior to becoming a pilot, the first pilot had been employed by the Utah ADC program for about 5 years as a fixed-wing gunner and field technician. In a letter (copy attached) dated October 24, 1995, by the Acting Director of the ADC Western Region program, the first pilot was given a waiver to begin training as an ADC pilot without the required 150 flight hours. The letter stated that the pilot had entered an "accelerated flight training program to obtain the required private pilot certificate and [obtained] 100 hours of flight time." According to an ADC "Daily Pilot Training Report" (attached) dated April 30, 1996, the first pilot had been endorsed by the second pilot as completing the required training for Phase I. The pilot had logged 100 hours of front seat pilot time and a total flight time of 394 hours at the time of the endorsement. On August 20, 1996, the pilot successfully passed an ADC fixed wing pilot proficiency check (copy of flight check form attached) and was endorsed to begin Phase II of the training. He remained in the Phase II training at the time of the accident which allowed him to pilot the airplane from the front seat, with an instructor pilot/gunner in the rear seat, during aerial hunting as per the agency's published training syllabus (attached). Second Pilot Information. The second pilot, who was acting as the co-pilot/gunner/instructor pilot in the rear seat during the accident flight, was 69 years old. He held an FAA commercial pilot certificate with ratings for airplane single-engine land and instrument airplane. He did not hold an FAA certified flight instructor certificate, nor was he required to by the USDA as a public use instructor pilot. According to FAA records, the second pilot was issued an FAA Second Class Medical Certificate on February 2, 1996, with the limitation that he must wear corrective lenses. The second pilot indicated that he had logged a total of 19,800 flight hours at the time of the medical application. According to documents (copies attached) provided by representatives of the ADC, the second pilot had been an experienced, retired ADC pilot who had been hired back by the Utah Department of Agriculture for the specific purpose of providing instruction to the first pilot during the first pilot's two-year ADC training period. METEOROLOGICAL INFORMATION Ground witnesses stated that the weather conditions were "clear and calm" at the time of the accident, and the temperature was about 58 degrees F. The Safety Board also collected recorded National Weather Service surface observations (print-out attached) for Cedar City, Utah, and Salt Lake City. These data were utilized to estimate the density altitude at the time of the accident; the estimation yielded a density altitude of about 6,500 feet. WRECKAGE AND IMPACT INFORMATION The airplane wreckage was examined at the accident site by the Safety Board on October 11, 1996, the morning after the accident. The entire accident site was about 40 feet long and 40 feet wide. The site was located on level terrain at an elevation of about 5,300 feet msl and about 18 nautical miles from the departure airport. An examination of the accident site revealed running ground tracks of at least two coyotes headed east from the west toward the accident site (wreckage diagram attached). The magnetic bearing of the tracks was 070 degrees, and the tracks crossed to the west of the wreckage. The wreckage and ground impact scars were oriented along a magnetic bearing of 290 degrees. A nearly-linear ground scar similar to the thickness and length of the airplane's leading edge wing span was noted about 30 feet east of the wreckage. The scar, as viewed looking toward the wreckage, was bisected by a hole in the ground that measured 2 feet wide by 2 feet long. Debris from the airplane's landing light, which was installed on the left wing of the airplane, was found to the right of the hole, as viewed looking toward the wreckage. Plexiglas pieces and the remains of a ribbon dispenser were found leading up to the main wreckage from the ground scar. The ribbon dispenser had been installed on the right main landing gear strut. According to local authorities (sheriff's report attached), a shotgun was found at the accident site. The shotgun muzzle was pointed out the left rear window and had five rounds in its stock and one in the chamber. According to the ADC Aviation Safety and Operations Manual: "The weapon will at no time have a shell in the chamber unless the muzzle is outside of, and pointed away from the aircraft." According to the operator, this situation typically occurs when the gunner is siting a coyote with the intention of shooting it. No evidence of fire or an in-flight structural failure was found. All primary and secondary flight control surfaces were accounted for at the main accident site. No evidence was found to indicate a flight control deficiency. Continuity of all flight control cables were verified. An examination of the left wing revealed that both lift struts were attached and bent. Uniform spanwise leading edge compression damage was evident on the wing. The leading edge exhibited distinct downward compression damage in an area beginning from the left wing tip and ending about 8 feet inboard from the tip. The left flap was destroyed and a preimpact flap setting could not be determined. An examination of the right wing revealed that both lift struts were attached and bent. Uniform spanwise leading edge compression damage was evident on the wing; the damage was less evident on the left wing as compared with the right wing. The leading edge exhibited distinct upward compression (opposite of the left wing) damage in an area beginning from the right wing tip and ending about 7 feet inboard from the tip. A piece of vegetation was found imbedded into the underside of the right wing. The right flap was destroyed and a preimpact flap setting could not be determined. All tail control surfaces were intact and undamaged. The tail cone area exhibited distinct torsional damage to the left about the airplane's longitudinal axis. The engine, with propeller attached, remained attached to the airframe and was crushed rearward into the cabin area. The cowling was removed by investigators and the engine was pulled away from the airframe to facilitate examination. The push rod tube housings on the no. 1 and 3 cylinders, the no. 1 top spark plug wire, oil sump, carburetor, and magnetos were impact damaged. The carburetor inlet screen remained attached to the fuel line and was observed to be free of contaminants. Crankshaft and valve train continuity was verified as the crankshaft was manually rotated through 360 degrees. The examination of the engine did not reveal any evidence of a preimpact mechanical deficiency. The two-bladed McCauley metal propeller was removed from the engine and examined. The propeller spinner exhibited evidence of rotational crush damage that was concentric about the tip of the spinner. Propeller blade no. 1 was bent into an "S" shape and exhibited chordwise scratching and leading edge gouging. Propeller blade no. 2 was relatively straight; it exhibited slight forward bending, chordwise scratching, and leading edge polishing. An examination of the cockpit revealed that the rear throttle handle had been removed from the rear throttle control area. When removed, the throttle is kept in a pouch placed in back of the front pilot's seat and is made accessible by the rear seat occupant. The control stick for the rear seat was intact and not jammed. The throttle and control stick in the front seat area were intact and not jammed. A shotgun, 245 shotgun shells, hand tools, rope, electrical cord, fire extinguisher, and a survival kit were found in the rear cabin area and underneath the rear seat. The cumulative weight of these items was about 50 pounds. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was performed on the first pilot by Dr. Todd C. Grey, M.D., on October 11, 1996, at the Utah State Office of the Medical Examiner in Salt Lake City. According to the report of autopsy, the immediate cause of death was "Multiple Blunt Force Injuries." Specimens taken from both pilots were analyzed by the FAA Civil Aeromedical Institute, Oklahoma City, Oklahoma. According to their report (attached), negative results for alcohol, carboxyhemoglobin, cyanide, and all screened drugs were reported. ADDITIONAL INFORMATION Aerial Hunting Flight Profile. According to representatives of the ADC, pilots of aerial hunting aircraft typically train for and perform the following: Upon identifying an animal to kill, the aircraft is flown at 100 to 150 feet above the ground and is maneuvered to place the animal on the left side of the aircraft. At this point, a "pass" is initiated, which is considered as a straight-in landing approach at 60 to 70 mph of indicated airspeed. Rudder may be applied to optimize shooting opportunity. The pass culminates 10 to 30 feet above the ground when the gunner fires the shotgun out of the left side of the aircraft. After firing, the pilot flies the aircraft in a straight line with a normal climb rate at 60 to 70 mph of indicated air
The first pilot's failure to maintain adequate airspeed while maneuvering the airplane in close proximity to the ground. This subsequently led to an aerodynamic stall and uncontrolled descent into the ground. Factors contributing to the accident include the lack of adequate altitude to recover from the stall, the pilot's failure to operate the airplane within its published weight and balance envelope, and high density altitude.
Source: NTSB Aviation Accident Database
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