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On March 11, 1998, at 1009 hours Pacific standard time, a Christen A-1, N9615G, operated by the United States Department of Agriculture (USDA) as a public-use aircraft, collided with terrain approximately 8 statute miles north of Lebec, California. At the time of the accident, the front seat pilot was maneuvering the airplane at a low altitude in furtherance of the USDA's Animal Plant Health Inspection Service (APHIS) Wildlife Services program. Visual meteorological conditions prevailed, and a company flight plan was filed. The airplane was destroyed, and the commercial pilot in the front seat (a trainee in the program) was fatally injured. The rear seat crewmember, who also possessed a commercial pilot certificate, was performing aerial gunnery and instructional duties. He was seriously injured. The local area flight originated from an open field about 0930. The field was located about 5 miles from the crash site, northwest of Interstate Highway 5 and the Pump Plant Road.
The USDA management reported that the mission of the APHIS program is to curtail damage to agricultural products caused by wildlife. To effectively accomplish the program's objectives, the Wildlife Services aviation program requires its pilots to fly in close proximity to the ground while maneuvering at slow airspeeds. The accident occurred during an authorized aerial hunting flight operation over a designated work site on private property. The flight crew consisted of a trainee-pilot and an instructor-gunner.
An USDA employee-witness, who was working as a ground crewmember in the coyote hunting operation, and the instructor-gunner reported the sequence of events leading to the accident. In summary, the ground-based witness, who was approximately 1/3-mile from the accident site, reported seeing the airplane flying at its customary low altitude. About 30 seconds prior to the crash the witness informed the airplane's crew via radio that he intended to reposition himself closer to the area where the airplane was flying. The instructor-gunner acknowledged his radio transmission and did not indicate any difficulty with the airplane.
The witness further reported observing the airplane commence a gradual left, course-reversal turn, and nothing unusual was noted. After about 8 seconds the airplane commenced another left turn. The left wing lowered and a 30- to 45-degree angle of bank was established. Within a second after initiating the left turn, the airplane appeared to be flying more slowly and at a lower altitude than normal, and this alarmed the witness. As the turn progressed, the left bank angle slightly increased and the airplane impacted the ground.
The instructor-gunner made several verbal and written statements regarding the sequence of events leading to the crash. In pertinent part, he reported the following:
During the accident flight his primary function was to kill coyotes. Secondarily, he was supposed to be observant of the manner in which the front seat trainee-pilot was handling the airplane's controls and provide any needed guidance.
The instructor verbally reported that during an earlier low-level turn, the trainee-pilot had allowed the airplane's nose to abruptly lower (as the angle of attack decreased) and the airplane dove toward the ground. The instructor stated that he had informed the trainee that her handling of the airplane was improper, and he provided guidance to resolve the problem.
The instructor further reported that a few minutes prior to the crash he shot a coyote. After the shoot, the pilot began reversing course to overfly the general area.
The pilot climbed approximately 100 feet above ground level (agl), and then, while looking for additional animals, descended to between 50 and 60 feet agl. Thereafter, the pilot descended to about 20 to 25 feet agl. The instructor ejected a live shell from the shotgun. The shell landed on the airplane's floor rather than in the shell pouch on the rear of the pilot's seat. (The USDA reported that its policy requires that before a firearm is returned inside the airplane, the firearm's breach must be cleared of any live ammunition. This process requires the gunner to briefly redirect his attention from outside to inside the airplane.)
The instructor indicated that he redirected his attention from outside the airplane toward the airplane's floor to look for the shell. During this time, the instructor reported that he felt the airplane turn left, the engine power remained around 2,000 or 2,200 rpm, and the stall warning horn activated. The bank angle was more than 30 or 40 degrees, perhaps as much as 65 degrees. The instructor looked up from the floor as the airplane's nose lowered. He attempted to grab his control stick; however, the airplane crashed.
The instructor also reported that the pilot "never let on that anything was wrong or she was having a problem of any kind. The aircraft was running good and we had no problems with the controls to my knowledge."
Front Seat Trainee-Pilot.
The trainee-pilot weighed 104 pounds and was 61 inches tall. She used two personal seat cushions while flying. The cushions were placed behind the pilot's back to move her forward in the seat. The estimated thickness of her cushions was 4 inches. USDA management reported that because the airplane was manufactured with a fixed (nonmovable) seat, some of its pilots utilize supplementary cushions to move them forward enough to reach the rudder pedals.
A review of the pilot's personal flight record logbooks revealed that her total logged flight time was about 4,082 hours. She possessed a certified flight instructor (gold seal) certificate and had given about 1,597 hours of dual flight instruction.
The pilot's first experience flying a Christen A-1 occurred on January 20, 1998. The flight was performed with the instructor-gunner in the accident airplane. The purpose of the flight was to receive initial orientation and familiarization in flight operations associated with aerial hunting. Between January and March, 1998, the pilot logged a total of 66.9 hours in the airplane during training flights on 19 days.
USDA management reported that along with data submitted by the pilot in her employment application, she indicated having 500 hours of low-level type flying experience. The pilot reported that this experience was gained during contract flying for the U.S. Forest Service and search and rescue missions for the Civil Air Patrol.
During the Safety Board's logbook review, no evidence was found of the pilot having any previous low-level flight and maneuvering experience similar to that provided by the USDA in aerial hunting operations.
The instructor-gunner weighs 144 pounds, and he is 71 inches tall. He does not use extra seat cushions while flying.
The instructor-gunner reported that his total flight time was about 6,837 hours, of which about 700 hours were flown in the accident model of airplane. He had flown about 128 hours during the preceding 90-day period.
According to the instructor-gunner, when he began teaching the pilot, he placed airplane-handling restrictions on her, which were the same as for any pilot he trains. The restrictions were: (1) No turns or passes at less than 60 miles per hour; and (2) No turns using over a 45-degree angle of bank.
The instructor reported that management asked him to provide the new hire with initial indoctrination including flight training appropriate to the USDA's aerial hunting program, and on January 20, 1998, the training commenced. The instructor reported to the Safety Board that the new hire ". . . did a very good job of handling the airplane." But, "she was not strong enough to pull full flaps . . .".
Thereafter, the trainee acquired about 43.3 hours of flight training with another USDA instructor who was located in Oregon. This instructor did not report observing any problems with the trainee's airplane handling skills.
The trainee then returned to California for additional training with her first instructor. The instructor reported that during a March 9, 1998, flight the trainee had difficulty maintaining the proper pitch attitude after applying full engine power following a shooting pass. As engine power increased, the airplane's nose rapidly pitched upwards. The instructor indicated that the trainee ". . . just was not strong enough to push the nose over, so I told [her] to try [using] trim." During the flight, the instructor also observed that when the trainee banked the airplane toward a coyote she would reduce engine power thus allowing the nose to "drop fast." The instructor stated that he provided the trainee with additional flight instruction.
The instructor further reported that during a March 10, 1998, flight, the trainee had ". . . some problems pushing the nose of the airplane forward before a turn after applying full power." He provided her with instruction that seemed to be useful.
Also, the instructor stated that he "was concerned" about the trainee trying "to cut [engine] power to idle [during a] turn with a nose low attitude and in a steep dive." The instructor provided about 45 minutes of flight instruction, and opined that the trainee was doing "a very good job."
USDA Management Policy.
The USDA's regional aviation manager reported that during the accident flight the front seat pilot was receiving instruction in low-level aerial hunting techniques during a 6-month-long flying course.
The manager reported that performance of low altitude maneuvers, including maintaining altitude while executing left turns, is a required flying skill necessitated by the aerial hunting operation. The maximum angle of bank generally required during turns is 35 to 40 degrees, and bank angles exceeding this amount are permitted only by experienced pilots.
The manager additionally indicated that it is not the USDA's intention to hire pilots with deficient flying skills. When hired, all of the pilots meet the USDA's minimum professional pilot series experience standards. The USDA aviation program does, however, teach the new hires how to perform the unique type of flying, such as low altitude maneuvering, which is required during the aerial hunting operations.
Neither the regional nor the State of California program manager reported awareness of any flying skill deficiency on the part of the front seat pilot. Both managers reported that the USDA does not maintain specific written records regarding newly hired pilots' flying skill or flight training progress.
However, instructors do provide management with verbal progress reports. Management indicated receipt of at least one verbal report which indicated that the trainee-pilot was satisfactorily progressing. Management indicated it was unaware the trainee was, at times, having difficulty performing specific low altitude turning maneuvers or fully extending the wing flaps.
According to the USDA, it frequently refers to the Christen A-1 airplane as being a "Husky." The USDA management stated that it had exclusive use of the airplane that it operated and was responsible for its maintenance. The USDA intended that the airplane be maintained in accordance with the Federal Aviation Administration's (FAA) annual and 100-hour inspection requirements.
The USDA management reported that its employees were responsible for scheduling all airplane maintenance and ensuring its adequacy. The Safety Board's review of the airplane's maintenance records revealed that between February and March, 1997, the airplane had been modified to accommodate the USDA's mission. In part, the modifications consisted of installation of an automatic flagger device, an openable left side window and communication radios. Thereafter, the airplane was placed into service.
As the airplane accumulated flight time it received a series of inspections. By the accident date, the airplane had received four, 100-hour inspections, and one annual inspection. Two different non-USDA (contract) mechanics signed the airplane's logbooks certifying their work during these inspections. The last inspection was performed on March 5, 1998, at 724.57 total airframe hours.
Postcrash, the airplane's tachometer registered 741.26 hours. No written evidence was observed in the maintenance records indicating the airplane had any outstanding squawks or received any maintenance since its last inspection.
During interviews with the operator, the Safety Board received information that during March 1997, its personnel had performed additional maintenance for which there was no written record. The operator had attached the front seat's shoulder harness, along with its associated inertial reel, to the lower back structure of the front seat. The harness webbing had been routed upward from the inertial reel, beneath seatback material, and over the top of the seat. No evidence of any approvals was found for this shoulder harness attachment installation which varied from the airplane manufacturer's design.
According to the airplane manufacturer, at the factory the front seat shoulder harnesses was anchored to an overhead structural hardpoint location on the airframe. The manufacturer reported that the operator's modification never would have been approved. The manufacturer indicated that the shoulder harness attachment at the back of the front seat was contrary to the FAA Type Data, A22NM, for a Husky A-1 airplane. Therefore, at the time of the accident the airplane was not in conformity with its type certificate.
Several persons located in the vicinity of the accident site reported that at the time of the crash it was sunny and the visibility was at least 10 miles. The wind was nearly calm, and the temperature was between 75 and 80 degrees Fahrenheit.
Neither the USDA nor the FAA reported recording any communications to or from the accident airplane. Also, communications between the airborne crewmembers were not recorded.
WRECKAGE AND IMPACT INFORMATION
The accident site was located on private property approximately 34 degrees 57.18 minutes north latitude, by 118 degrees 55.45 minutes west longitude. The estimated elevation was 1,500 feet mean sea level.
From an examination of the accident site, airplane wreckage, and witness statements, the airplane was found to have descended into the hard dirt surface of an open field while in a left bank and nose down pitch attitude. The initial point of impact (IPI) was noted by the presence of an estimated 1-inch-deep depression in the ground which approximately matched the size and shape of the left wing's leading edge. Red colored left wing navigation light lens fragments and the associated wing's crushed navigation light housing were found at the extreme south end of the ground scar. The airplane's separated pitot tube was found several yards to the north
The main impact crater was found about 26 feet north of the navigation light. The crater was oval shaped, about 1-foot deep, and was the approximate size of the airplane's engine compartment. The entire airplane structure, which remained principally intact, was found about 15 feet northeast of the main crater.
The left wing, outboard of midspan, was observed crushed aft at an estimated 30-degree angle. The wing tip was found bent upward at an estimated 45-degree angle. Compressive buckles were observed on the wing's upper surface. The outboard portion of the right wing, at the leading edge, was observed bent in an upward and aft direction.
The engine compartment was observed crushed in an aft and upward direction. The left main landing gear was found broken from its supporting structure in an aft direction. Compressive buckles were present in the skin on the left side of the fuselage and in the floor beneath the front seat.
The empennage appeared undamaged. All of the airplane's flight control surfaces were found attached to the airframe. The integrity of the entire flight control system was confirmed between each flight control surface and both of the cockpit's control sticks. The surviving pilot indicated that no mechanical malfunctions had been experienced during the flight. There was no evidence of fire. (See the accident scene photographs for additional information.)
MEDICAL AND PATHOLOGICAL INFORMATION
On March 11, 1998, an autopsy was performed by the Kern County Coroner's Office, Bakersfield, California. In addition, a x-ray examination was performed for the purpose of ascertaining whether foreign material, consistent with a firearms discharge was present. None was found. The coroner listed the cause of death as massive craniofacial and cervical injuries due to blunt force trauma.
Toxicology tests were performed by the coroner and the FAA. The laboratories' blood and urine test results were negative for all screened substances. No ethanol was detected.
The Safety Board interviewed personnel who initially responded to the accident site from the USDA, the Kern County Fire Department, the California Highway Patrol, and the private ambulance company. In summary, the persons who initially responded to the accident airplane reported finding the pilot in the front seat, with two seat cushions behind her back, and leaning forward. The pilot's head was against the right side of the instrument panel. The front seat was found rigid in place and could not be moved in any direction. The back of the seat was found inclined forward at an angle estimated between 10 and 15 degrees. The pilot was observed wearing lap and shoulder belts, and a helmet.
Several responding personnel opined that the inside of the cockpit appeared virtually intact, and the occupiable space surrounding the pilot did not appear significantly compromised.
The fire department personnel reported that the pilot was found pinned in the cockpit. The control stick was observed pressed against the front of the seat. The pilot's legs were free to move beneath the instrument panel. Firefighters were able to extricate the pilot after making several cuts removing a portion of the right side of the airframe structure.
The instructor reported that during the accident sequence both he and the front seat pilot were wearing their respective lap belts, shoulder harnesses, and safety helmets. The instructor stated that he received a neck burn injury from the left side of his shoulder harness in addition to other serious injuries during the impact sequence. The instructor climbed out of the airplane without assistance.
The instructor's shoulder harness was found attached to the airframe's upper fuselage structure at a location consistent with drawings supplied by the airplane manufacturer. The trainee-pilot's shoulder harness was found intact between the lower portion of the seatback, where it had been connected, to the buckle.
The manufacturer's chief engineer reported that the relocation of the front seat shoulder harness, from the designed and FAA approved upper airframe (overhead) structural location to the lower back area of the front seat, allowed for the transmission of inertial crash loads directly to the seat frame, which is cantilevered off of the lower fuselage structure. The seat frame and fuselage were not designed to accept this type of loading. The relocation of the shoulder harness was contrary to the airplane's type data. The overturning moment of the seat and forward bending of the seat back decreased the occupiable space afforded to the pilot.
TESTS AND RESEARCH
The propeller, engine, and airframe were initially examined on scene. The entire airplane was reexamined following its recovery.
The propeller was found attached to the crankshaft mounting flange. The blades were observed torsionally deformed. Gouges were noted in the leading edge, and score marks in a chordwise direction were present on the cambered surface.
The continuity of the engine's valve and gear train was confirmed during rotation of the crankshaft. Thumb compression was felt in all cylinders. All spark plugs exhibited wear signatures, which the engine participant opined were consistent with normal usage. The left magneto was rotated by hand and spark was observed at the termination ends of the upper left and lower right spark plug leads. The gascolator screen was clear. No blockages were noted in the air filter or within the induction or exhaust systems.
No fuel was found upon disconnecting the main fuel line leading to the carburetor inlet. The carburetor was removed from the engine. When its accelerator pump was depressed, fuel spurted from the discharge nozzle orifice.
Pilot's Front Seat and Shoulder Harness Examination.
A visual examination was performed of the front seat, including the floor structure beneath the seat and the seat's tubular legs. No evidence of preimpact repairs, weld failures, cracks, or corrosion was noted.
The front seat's forward legs were found attached to the underlying floor structure. The front seat's rear legs were found partially separated from the underlying floor supporting structure which was observed buckled in upward and aft directions (see photographs). The seat's tubular rear leg structure was found bent in a direction consistent with tension overload in both upward and forwarding bending directions.
The pilot's inertial reel was functionally tested and was operational. A slight binding or abrasion noise was evident when the shoulder harness webbing rubbed against adjacent material located above and below the harness in the seat back upholstery.
Shoulder Harness Installation Engineering Analysis.
Under the Safety Board's supervision, measurements were taken of the deformation to the accident airplane with an emphasis on deformation to the structural frame members surrounding the front seat. Using the obtained measurements, the manufacturer's chief engineer calculated that the loads which the front seat and the supporting fuselage structure encountered "far exceeded" the loads for which it was certificated and designed to withstand.
The engineer indicated that in an unmodified airplane, the pilot's seat back carries no load from the occupant since the shoulder harness is secured to the upper fuselage frame. The examination of the accident airplane's front seat revealed it was deformed. The manufacturer opined that during the impact sequence, the front seat broke free at the lower aft attachment points, which allowed the seat to pivot about the lower front attachment points. There was evidence that the front seat pilot's head impacted the instrument panel. Also the distance between the seat back and the front of the seat's cushion was about 7 inches. In a factory-equipped airplane the distance is 2.75 inches. (For complete details, see the manufacturer's April 1998, letter and report entitled "Husky S/N 1136 Shoulder Harness Installation Engineering Analysis.")
Bank Angle Determination.
The impact-damaged left wing tip was examined and measurements were obtained documenting the crush line. The manufacturer compared the measurements to an undamaged wing tip in order to ascertain the degree of left bank and nose down pitch attitude at ground contact. In part, the manufacturer reported that if the airplane's pitch attitude was level, the left wing's position light would contact the ground when established in a 64.7-degree bank. If the nose was pitched downward, the corresponding left bank angle decreased. For example, if the nose was pitched downward 24 degrees, the position light would contact the ground when in a 40-degree bank.
Maintaining Altitude During Turns.
The manufacturer selected 9 pilots, placed them into a turn using over a 30-degree angle of bank, and observed their ability to maintain altitude. Without exception, all lost altitude.
The USDA management reported that a basic airplane handling requirement during aerial hunting maneuvers is the pilot's ability to maintain altitude during turns. As the training progresses, the unique and precise flying skills required accomplish this and should become ingrained in the pilot's behavior.
Flap Extension Force.
The manufacturer reported that the force required to extend the wing flaps decreases as airspeed decreases below the 73 miles per hour maximum flap extension speed. Based upon the flap control lever's location in the cockpit, the manufacturer opined that with the added seat cushions used by the accident pilot, ". . . it would be hard to get the full 30 degrees of flaps on."
The USDA also reported that some of its pilots, who fly the same model of airplane and do not use supplemental seat cushions, were of the opinion that the force required to apply the wing flaps was high.
Airworthiness and Operation of the Airplane.
The FAA coordinator reported that its office considered the accident airplane to be a "public" aircraft. Accordingly, during the accident flight, the FAA had no regulatory authority over the operation or airworthiness responsibility for the airplane.
USDA management indicated it desired that its operation be performed in accordance with the FAA's regulations. Regarding responsibility for the airworthiness of the airplane, according to 14 Code of Federal Regulations (CFR) Part 91.403, the owner or operator of an airplane is primarily responsible for maintaining the airplane in an airworthy condition.
At 14 CFR 43, Appendix D, the FAA has indicated the scope and detail of items to be included in 100-hour inspections. In pertinent part, the mechanic performing the inspection is responsible for examining the airplane's safety belts for defects, proper installation and operation.
The FAA has also indicated that no person may operate a civil aircraft unless it is in an airworthy condition. The pilot-in-command is responsible for determining whether the airplane is in condition for safe flight (see 14 CFR 91.7).
In addition to the designated participants listed in the Safety Board's report form, the following additional persons received party status:
1. Gary Simmons, California State Director, United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, P.O. Box 255348, Sacramento, CA 95865
2. Larry Vetterman, Regional Aviation Manager, USDA, APHIS/ADC/WS, 12345 W. Alameda Parkway, Suite 204, Lakewood, CO 80228
3. Nicholas Guida, Chief Engineer, Aviat Aircraft, Inc., P.O. Box 1240, 672 South Washington, Afton, WY 83110
4. Mark Heiner, Test Pilot, Aviat Aircraft, Inc., P.O. Box 1240, 672 South Washington, Afton, WY 83110
Following the accident the airplane wreckage was recovered and placed into storage at the facilities of Ray's Aviation, Santa Paula Airport, California. On March 20, 1998, the entire wreckage was released to the USDA. No parts or records were retained.