IAD05LA138

With the autopilot engaged, and while climbing through approximately 5,000 feet msl, the pilot moved the heading bug 30 degrees to the right. The airplane then "sort of snapped with significant yaw," into a 60-degree right bank and lost about 1,800 feet of altitude. After recovering, the pilot continued to his destination. Examination of the airplane revealed that it was substantially damaged. Approximately five months prior to the accident, the autopilot system had been installed. Following the installation, the pilot experienced operational problems that included a "yaw problem" which began to worsen, but could not be duplicated by maintenance personnel. A postaccident examination of the autopilot and heading system also revealed no anomalies. Examination of the aft fuselage and tailcone revealed that the yaw damper was contaminated with oil. The source of the oil was an oil streak that ran from under the engine cowling aft along the belly of the airplane, and then up through the air conditioning exhaust vent. Two other airplanes which experienced yaw damper events were also examined, and oil contamination of the yaw damper amplifiers were identified.

History of flight

On September 12, 2005, about 0930 eastern daylight time, a Piper PA-46-500TP, N747AW, was substantially damaged while recovering from an in-flight upset, 15 miles southwest of Steven A. Bean Municipal Airport (8B0), Rangeley, Maine. The certificated private pilot and the two passengers were not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight destined for Lehigh Valley International Airport (ABE), Allentown, Pennsylvania. The flight was conducted under 14 CFR Part 91.

According to the pilot, the autopilot was engaged in "heading bug mode," and the airplane was climbing at approximately 700 feet per minute.

About 15 miles southwest of Rangeley, while climbing through approximately 5,000 feet msl, in "light chop" above mountainous terrain, the pilot moved the heading bug 30 degrees to the right to remain clear of clouds. The airplane then "sort of snapped with significant yaw," into a 60-degree right bank.

After overpowering the autopilot and recovering from uncontrolled flight, the pilot turned the airplane through two 360-degree turns, and climbed to 16,500 feet. About 20 to 25 miles southwest of Rangeley he requested flight following from air traffic control, and continued to Allentown without further incident.

The pilot estimated during the upset that the airplane had lost 1,000 to 1,800 feet of altitude, and could not remember if the autopilot disconnected during the upset or the recovery to controlled flight.

The accident occurred during the hours of daylight, about 44 degrees, 46 minutes north latitude, and 70 degrees, 47 minutes west longitude.

Personnel information

The pilot held a private pilot certificate with ratings for airplane single and multi-engine land, and instrument airplane. He reported a total flight time of 1,327.4 flight hours, and 224.8 hours as pilot in command in the accident airplane make and model. His most recent FAA third-class medical certificate was issued on May 16, 2005.

Aircraft information

The airplane was manufactured in 2000 and was originally equipped with an S-TEC 550 autopilot system. At the time of the accident, the airplane had accrued 1,227.3 total hours of operation.

According to logbook entries and correspondence to the Safety Board by the owner, on March 24, 2005, a new S-TEC MAGIC 1500, autopilot system was installed. This installation included a new programmer computer, yaw amplifier, yaw servo, data converter, and an autopilot master switch.

On April 1, 2005, the airplanes most recent annual inspection was completed. Seventeen days later, the pilot advised the maintenance provider that the roll rate on the heading bug was "fast," as compared to the previous autopilot, and that he was not sure the autopilot was operating properly.

Sometime during the week of May 9, 2005, the yaw servo and rudder trim were adjusted by the maintenance provider.

On June 23, 2005, the pilot reported that the "yaw problem" began to worsen. On July 3, 2005, the pilot encountered a "severe yaw" when the autopilot was "released," and the flight director bars would not work when the flight director mode was selected. The pilot also stated he requested the original "550" autopilot be reinstalled at that time.

On July 11, 2005, the maintenance provider attempted to troubleshoot the autopilot problem. The wires were checked between the autopilot computer and trim monitor, pilot and copilot's trim switches, trim master switch, pitch and pitch trim servos, with no anomalies noted. The autopilot computer was removed, a loaner unit was installed for test purposes, and no anomalies were noted. A new unit was then installed, and operationally checked. The yaw damper amplifier was also removed and replaced with a new unit, and was operationally checked.

Meteorological information

The reported weather at Berlin Municipal Airport (BML), Berlin, New Hampshire, 33 nautical miles southwest of Rangeley, at 1352, included: winds from 300 degrees at 9 knots, gusting to 16 knots, visibility 7 miles, overcast skies at 3,400 feet, temperature 72 degrees Fahrenheit, dew point 57 degrees Fahrenheit, and an altimeter setting of 29.96 inches of mercury.

Wreckage and impact information

A postaccident examination of the airplane revealed that the airplane's wings were damaged during the event. Multiple wrinkles on both wing upper surfaces were noted extending from the wing roots outboard for approximately 43 inches, and on both wings, the wrinkles terminated at a wing production splice.

Engine Examination

Examination of the engine revealed no evidence of malfunction. The engine condition trend monitoring data was downloaded for review, and no engine faults were recorded for the accident day.

Interior Examination

Examination of the airplane's interior revealed that the Federal Aviation Administration (FAA) approved pilot operating handbook (POH) for the airplane, which contained the autopilot airplane flight manual supplement, was located in a cabinet drawer behind the copilot's seat. Further examination of the interior revealed two checklists labeled: "FOR TRAINING USE ONLY," located in a sidewall storage pocket on the copilot's side of the cockpit. Both of the checklists did not contain any information associated with the autopilot installed in the airplane at the time of the accident. In addition, there was a yellow tie wrap fastened to the pitch trim circuit breaker.

Primary and Secondary Flight Controls Examination

The flaps, left and right ailerons, left and right elevators, and rudder were intact and undamaged. Flight control continuity was confirmed for all control surfaces, all control cable tensions were within specified tolerances, and control travel for all surfaces was verified to be within specifications. No problems with binding, routing, or wear was evident.

The elevator trim system, rudder trim system, and ground-adjustable aileron trim tab were examined. Functional checks were performed and no anomalies were noted. The aileron trim tab was present on the right aileron and all fasteners were secure.

Autopilot and Heading System Examination

Examination of the autopilot and heading system revealed that all system components were found to be installed as per the manufacturer's manuals and drawings with the exception of the air data attitude heading reference system (ADAHRS) wiring harness, which had been modified to help calibrate the magnetic heading portion of the electronic flight instrumentation system (EFIS).

All bridle cable tensions were found to be within specified tolerances and no problems with binding, routing, or wear was discovered.

Functional checks of the autopilot system were performed utilizing the manufacturer's ground maintenance tests procedures and the POH. No evidence of malfunction or anomalies was discovered, and no defects with the autopilot or EFIS were noted.

Simulations of several in-flight failures revealed that all autopilot disconnect functions were working. Disconnects would occur during simulated heading and ADAHRS failures, or during loss of data. All inputs from the pilot's primary flight display (PFD) and navigation display (ND) units functioned properly.

Manual disconnects of the autopilot system, yaw damper system, and pitch trim system was performed utilizing the emergency procedures contained in the airplane flight manual supplement for the autopilot. No anomalies were noted, and all disconnect functions worked.

Ability to manually override the autopilot was checked utilizing one hand on the pilot's control wheel, and the roll and pitch servos override limits were within specifications. The rudder servo was also overridden, and no unusual noise or feel was noted when overriding any of the autopilot servos.

All electronic audio alerts annunciated correctly and in proper sequence, and electronic altitude callouts were fu