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On August 6, 2001, about 1145 Alaska daylight time, a Cessna 172S airplane, N813SP, sustained substantial damage during a precautionary landing at the Quartz Creek Airport, located about 3 miles east of Cooper Landing, Alaska. The airplane was being operated as a visual flight rules (VFR) local area personal flight when the accident occurred. The airplane was registered to Av Alaska Inc., Anchorage, Alaska, and operated by the pilot. The private certificated pilot and one passenger received serious injuries. Two other passengers were not injured. Visual meteorological conditions prevailed. A VFR flight plan was filed. The flight originated at the Ted Stevens Anchorage International Airport about 1100.
According to information provided by an Alaska State Trooper, and information provided by a witness at the Quartz Creek Airport, the accident airplane was observed to touch down about mid-length on runway 21 and bounce several times. The airplane then collided with trees beyond the departure end of the runway, and came to rest next to a boat launch ramp in an adjacent campground. At the accident scene, the airplane was resting upright on its main landing gear, but nose down, with the nose wheel strut displaced forward, under the engine. The engine cowling was torn off the fuselage. The right wing separated from the fuselage at its rear attach point, and the wing was displaced forward from the fuselage.
In a telephone interview with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on August 10, the pilot reported that during the flight, the airplane suddenly began climbing. She said she used the manual trim wheel to trim the airplane nose down, but the airplane still pitched upward. She pushed forward on the control yoke in an attempt to counter the upward pitch. She said she did not know if the autopilot was on or off, but she did not consciously select or use the autopilot, and she said she did not know if the airplane was equipped with electric trim. She headed for the Quartz Creek airport, and bounced twice on the runway. The wheels collided with trees at the end of the runway.
During an in-person interview with the NTSB IIC on August 15, the pilot reported that after departing Anchorage, the airplane was in cruise flight about 3,000 feet msl near Kenai Lake. During the flight, the airplane suddenly began to pitch upward, climbing about 600 feet per minute. The pilot said she pushed forward on the control yoke to return to 3,000 feet msl, and noticed the trim wheel moving in a nose up direction. The pilot began to exert forward pressure on the control yoke to keep the airplane from climbing, and she said she was concerned that the airplane might stall. She asked her front seat passenger to help push forward on the control yoke. The pilot made a "mayday" call on the airplane radio, and decided to make an emergency landing at the Quartz Creek airport. The pilot said she turned onto about a one mile final approach to runway 21, but was either going too fast, or the runway was too short. She said she saw the end of the runway approaching, and added full throttle to begin a go-around. The airplane collided with trees at the departure end of runway 21. She said she had lowered the flaps for landing, but raised the flaps for the go-around.
The pilot said she did not remember any annunciator lights on the instrument panel, but during the emergency, she did remember seeing 7000 displayed in a box located above the transponder. The pilot said she used the radio transmit button on the left side of the pilot's control yoke, but did not use any other switches on the yoke. She reiterated that she was not aware the airplane had electric trim. The pilot said her front seat passenger is not a pilot, and did not touch any items on the control panel.
During an interview with the NTSB IIC, the front seat passenger reported that during their flight, the pilot suddenly told everyone to be quiet. The pilot was having trouble controlling the pitch of the airplane, and appeared to be attempting to trim the airplane by the use of a trim wheel. She was asked by the pilot to help push on the control yoke. She remember seeing a small landing strip in the area, but did not remember anything else until being placed in an ambulance.
The pilot holds a private pilot certificate with an airplane single-engine land rating. The most recent third-class medical certificate was issued to the pilot on December 15, 2000, and contained the limitation that the pilot must have available glasses for near vision.
According to the information contained in the Pilot/Operator Report (NTSB Form 6120.1/2) submitted by the pilot, the pilot's total aeronautical experience consists of about 230 hours, of which 220 were accrued in the accident airplane make and model. In the preceding 90 and 30 days prior to the accident, the report lists a total of 10.5 and zero hours, respectively.
The pilot reported she utilized the accident airplane for several instrument training flights and for personal use, and had accrued about 6 hours in the accident airplane (Cessna 172S). She said she was familiar with the electronic HSI and the moving map on the multifunction display. When she was receiving instrument flight training from an instrument instructor, she said she did not use the autopilot system, and was not provided with any familiarization with its function or controls. She said she was not aware the airplane had an electric trim system. The pilot said she was not provided with any training or a check out on the autopilot or electric trim system from the operator. She said that during personal flights, she did not intend to use the autopilot system, and had not familiarized herself with its functions or controls.
The airplane and engine had accumulated a total time in service of 333.4 hours since new. The airplane was maintained on an approved airworthiness inspection program (AAIP). The most recent inspection was accomplished on July 25, 2001, 38.2 hours before the accident.
The operator added the airplane to its fleet of rental airplanes in February, 2001. The airplane was equipped with a Honeywell KAP 140 two axis autopilot with altitude preselect, a Bendix/King transponder, dual Bendix/King KX 155A Nav/Comm radios, a Honeywell KLN 94 GPS navigation computer. The accident airplane was used for rental customers, and as a training airplane for students.
In March, 2001, additional equipment was installed in the airplane, including a Sandel Avionics SN 3308 Navigational Display, and a UPS Aviation Technologies, MX20 multifunction display as part of an FAA Capstone navigation/terrain and radar tracking demonstration project. The airplane's center radio/navigation stack was modified from its standard instrument panel installation to accommodate the installation of the multifunction display at the top of the center panel radio stack. The Honeywell KAP 140 autopilot computer, normally positioned at the bottom of the radio stack, and the airplane's transponder, were both moved to the right of the center stack. The autopilot was positioned in the center of the right side of the instrument panel, above the transponder, both in front of the right seat position.
The KAP 140 autopilot system consists of a computer/controller, interconnected to the GPS and navigation system displays, pitch and roll actuator servos, control yoke switches, and an electrical system, pull-type, circuit breaker. It provides an autotrim feature during autopilot operation, and manual electric trim when the autopilot is not engaged. The airplane also retains a manual trim wheel. The features of the autopilot system include a vertical speed mode, altitude hold, wing level, heading select, approach, ILS coupling to a localizer and glideslope, backcourse mode, altitude alert and altitude preselect. The electric trim system is designed to be fail safe for any single in-flight trim malfunction. Trim faults are visually and aurally annunciated. A lockout device prevents autopilot or electric trim engagement until the system has successfully passed a preflight self test. An automatic preflight self test begins with initial power application to the avionics electrical bus.
The left side of the pilot's control yoke contains a radio transmit button on the back side of the yoke. The front side of the yoke contains an autopilot disconnect button, and split manual electric trim switches, both of which need to be activated simultaneously to energize the electric trim.
The auto pilot system may be activated by pushing the autopilot engage/disengage button, heading select button, or the altitude hold button.
The autopilot system will disengage if an electrical power failure occurs, an internal autopilot system failure, pitch accelerations in excess of plus 1.4g or less than plus .6g (if produced by a servo runaway, not by maneuvering), a turn coordinator failure, activation of the roll, or pitch axis annunciator, activation of the A/P Disconnect/Trim switch on the control yoke, pulling off the autopilot system electrical circuit breaker, or turning off the avionics master or airplane electrical master switch.
Normal and emergency procedures for the autopilot system are listed in Supplement 15 of the airplane's information manual. The emergency procedures section of Supplement 15 that address autopilot, autopilot trim, or electric trim malfunctions, states, in part: Airplane control wheel - grasp firmly and regain aircraft control, and simultaneously press and hold the A/P DISC/Trim INT switch on the control yoke; re-trim manually as needed; autopilot circuit breaker - pull. The avionics master switch may be used as an alternate means of removing all electric power from the autopilot and electric trim systems.
Supplement 15 contains several warnings, including: "Do not help the autopilot or hand-fly the airplane with the autopilot engaged as the autopilot will run the pitch trim to oppose control wheel movement. A mistrim of the airplane, with accompanying large elevator control forces, may result if the pilot manipulates the control wheel manually while the autopilot is engaged."
The airplane's information manual, incorporated into a three-ring binder, was carried in the airplane. A pilot's checklist binder was also carried in the airplane. The pilot's checklist is a 5 by 8 inch, plastic ribbed-bound reference book containing abbreviated information about airplane systems and emergency procedures. It does not contain any information about the use of the autopilot system, or autopilot malfunctions. The cover of the pilot's checklist contains the following statement: "The pilot's checklist should not be used until the flight crew has become completely familiar with the airplane and systems. All normal and emergency procedure items and complete performance in the pilot's operating handbook and FAA approved airplane flight manual shall take precedence in case of conflict."
The operator reported that no formal training or check out for individual pilots or instructors on the autopilot, navigation, or electric trim systems, was provided to users of the airplane.
The manufacturer reported that during evaluation flights conducted by a company test pilot, the accident airplane make and model was controllable following a simulated trim failure at full nose up trim, with an aft center of gravity loading.
The closest official weather observation station is Soldotna, Alaska, which is located 38 nautical miles southwest of the accident site. At 1155, an automated weather observation system (AWOS) was reporting in part: Wind, calm; visibility, 9 statute miles; clouds and sky condition, clear; temperature, 64 degrees F; dew point, 48 degrees F; altimeter, 30.07 inHg.
AERODROME AND GROUND FACILITIES
The Quartz Creek airport is equipped with a single gravel-surfaced runway on a 030 to 210 degree magnetic orientation. Runway 21 is 2,200 feet long by 60 feet wide. The FAA's airport/facility directory, Alaska Supplement, listing for the airport notes, in part: "...the south threshold marker is 400 feet from trees." The trees are located between the south end of the runway and a paved road. The road borders a boat launch and camping area.
WRECKAGE AND IMPACT INFORMATION
The NTSB IIC, accompanied by FAA personnel and parties to the investigation, examined the airplane wreckage on August 13, 2001, at Cooper Landing after the airplane was recovered to a temporary storage area. The examination revealed the fuselage firewall was buckled and displaced aft at the top of the firewall. Additional buckling was noted along the top of the fuselage at the rear window.
The wings had been removed from the fuselage at the accident scene for recovery. The right wing had extensive spanwise leading edge aft and upward crushing, from the wingtip to about 6 feet inboard from the tip. The aileron had upward "U" shaped trailing edge deformation about 3 feet inboard from the tip. The left wing had upward and aft spanwise leading edge curling, primarily from the underside of the leading edge, from the wingtip to about 5 feet inboard from the tip. Both lift struts remained attached to their respective wing and lower attach points.
The elevator trim tab actuator was found extended at its minimum amount of travel (full tab down=.75 inches). According to the airplane manufacturer, the trim tab actuator setting corresponds to a 13 degree tab down (nose up) setting. The flaps were up. Flight control system, and trim system cable continuity was established from the cockpit to all flight control surfaces.
The propeller assembly, attached to the engine crankshaft flange, was fractured and separated from the engine at the nose of the case. The spinner was crushed aft, flat against the propeller and displaced to one side. One propeller blade had leading edge gouging, extensive chordwise scratching, and slight aft spanwise bending. The second blade had slight leading edge tip gouging, and slight forward spanwise bending.
The engine sustained impact damage to the underside and front portion of the engine. It was displaced aft and upward, and slightly to the right, into the airplane firewall. The fuel selector was on the Both position. The gascolator screen was free of contaminants. Fuel was found in the gascolator bowl and the manifold.
The pull-type circuit breaker for the autopilot system was in.
An examination of the accident site at the Quartz Creek airport revealed several broken sections of aspen and spruce tree tops located between the departure end of runway 21, and the first evidence of ground impact at the edge of a road bordering a campground and boat launch facility.
TESTS AND RESEARCH
According to the manufacturer, specific data for each make and model of airplane in which a KAP 140 autopilot is installed, is contained in a configuration module that is installed as part of the system. The configuration module also has a diagnostic function that stores autopilot system error codes that occur during a power cycle. A power cycle is counted anytime electrical power is available to the avionics electrical bus, whether or not the autopilot was turned On or Off. The configuration module can store up to 45 power cycles before it over-writes previous data, but power cycles are only recorded if an error code occurred. If an autopilot system error was detected, the error code is stored, along with the elapsed time from the start of a power cycle. An error code may occur, and be recorded, even though the autopilot was not utilized. As a diagnostic tool for avionics technicians, error codes may be downloaded onto a computer. The manufacturer provides a written text message associated with each error code.
Each specific power cycle number, along with an error code that is stored in the configuration module, has no correlation to any particular date of occurrence.
The autopilot system, consisting of the autopilot computer, the pitch and pitch trim control servos, the pilot's control yoke assembly, and the autopilot configuration module, was sent to the FAA's Kansas City, Kansas, FSDO, where an FAA inspector arranged for testing of the autopilot at the Honeywell facility located in Olathe, Kansas. On December 6, 2001, the autopilot was subjected to a variety of examinations that were overseen by an NTSB air safety investigator from the Southeast Field Office, Atlanta, Georgia. The Atlanta investigator was also conducting a separate investigation of a Cessna 172S airplane equipped with a similar autopilot system (NTSB report ATL02LA013).
During the examination of the autopilot system, a read-out of the autopilot configuration module indicated the number of the current power cycle at the time of the download was 165. A read-out of the previous 45 error codes from the autopilot configuration module revealed a variety of codes, some of which do not have a text description associated with the code. Two power cycles, numbers 26 and 166, had the error code 110 (autotrim runway) associated with their respective power cycle.
According to the manufacturer, the text description of error code 110 states, in part: "The trim servo was detected in opposition to the primary servo command. This may indicate an autotrim failure. The autotrim operations of the autopilot mode and manual electric trim operation will be disallowed until autopilot power is cycled and the KC 140 successfully passes pre-flight test."
The examination of the autopilot system at the Honeywell facility on December 6, 2001, did not reveal any mechanical or computer malfunction.
The airplane's annunciator module, consisting of a number of light emitting diodes (LEDs) was sent to the manufacturer for examination. The manufacturer, Heads Up Technologies Inc., Carrollton, Texas, reported the module passed a functional test.
On August 17, 2001, the accident airplane pilot's flight instructor notified the NTSB IIC that he experienced an autopilot system anomaly in the past. He related that during an instrument instructional flight in the accident airplane, a student seemed to have trouble controlling the airplane. He took the controls and discovered that the autopilot system was on, and the student was attempting to override a mis-trim configuration, as the autopilot had moved the trim in opposition to the student's control inputs. The instructor pilot reported he did not intentionally turn the autopilot system on. He turned the autopilot off and continued the instructional flight. He did not write up the event or report it to the operator.
The flight instructor also reported that when he provided instrument flight instruction to the accident pilot, he did not discuss the use of the autopilot system, or the electric trim system. He said he wanted the student to concentrate on basic instrument flying without the use of an autopilot.
The Safety Board released the wreckage, located at Wasilla, Alaska, to the owner's representatives on August 13, 2001. The autopilot components were retained by the Safety Board for examination until release on January 29, 2002.