BETHEL, AK, USA
N575D
Beech 1900D
The Beech 1900D airplane was landing on a dry, paved, 6,398 feet long by 150 feet wide runway, which required a correction for a left crosswind. During the landing roll, and after activation of the Decoto power steering system, the airplane suddenly veered to the right. The airplane continued off the right side of the runway, into an area of soft terrain, and the nose landing gear collapsed. In a written statement to the NTSB, the captain of the accident airplane wrote, in part: "Because of the strong winds, it was necessary to engage the power steering to assist with the left turn, a normal procedure. As I engaged the power steering, which was armed by the first officer at my request, the aircraft executed an immediate right turn of approximately 45 degrees. Both the first officer and myself attempted to counter-respond the event with full left rudder and maximum left braking. All attempts were unsuccessful, causing us to exit the runway, collapsing the nose gear, and sheering the props." In the presence of NTSB and FAA investigators, extensive tests were conducted on the Decoto power steering system, and associated components. No preaccident mechanical anomalies were noted with the system. The Flight Data Recorder revealed that the crew activated the power steering system with a derived ground speed of about 40 to 50 knots. The Decoto Power Steering System flight manual supplement states: "Use of power steering is limited to taxi operations only."
On October 22, 2000, about 1354 Alaska daylight time, a Beech 1900D airplane, N575D, operated by Frontier Flying Service, Inc., of Fairbanks, Alaska, sustained substantial damage during landing at the Bethel Airport, Bethel, Alaska. The airplane was being operated as an instrument flight rules (IFR) scheduled passenger flight under Title 14, CFR Part 121, when the accident occurred. The first pilot, a certificated airline transport pilot, the second pilot, a certificated commercial pilot, and the 17 passengers, were not injured. Visual meteorological conditions prevailed, and an IFR flight plan was filed. The flight originated at the Ted Stevens Anchorage International Airport about 1215. During a telephone conversation with the National Transportation Safety Board investigator-in-charge on October 22, the captain of the accident airplane reported that he was landing on runway 36, which required a correction for a left crosswind. He added that during the landing roll, and after activation of the Decoto power steering system, the airplane suddenly started pulling to the right. The airplane continued off the right side of the dry, paved, 6,398 feet long by 150 wide runway, into an area of soft terrain, collapsing the nose landing gear. He added that at no time did he, or the first officer, notice if the "PWR STEER FAIL" annunciator light illuminated. The airplane sustained substantial damage to the fuselage. The captain noted that upon departure from Anchorage, during the landing gear retraction, he heard a "thump" emanating from the nose wheel gear-well area, just before the landing gear doors closed. He stated that when the landing gear was lowered while on approach to the Bethel Airport, there were no abnormal sounds. The closest official weather observation station is located at Bethel. At 1353, an Aviation Routine Weather Report (METAR) was reporting in part: Wind, 340 degrees (true) at 16 knots, gusts 23 knots; visibility, 10 statute miles; clouds, 2,800 feet broken; temperature, 28 degrees F; dew point, 19 degrees F; altimeter, 29.57 inHg. In the Pilot/Operator report (NTSB form 6120.1/2) filed by the operator, the captain supplied a written statement about the accident. He wrote, in part: "Because of the strong winds, it was necessary to engage the power steering to assist with the left turn, a normal procedure. As I engaged the power steering, which was armed by the first officer at my request, the aircraft executed an immediate right turn of approximately 45 degrees. Both the first officer and myself attempted to counter-respond the event with full left rudder and maximum left braking. All attempts were unsuccessful, causing us to exit the runway, collapsing the nose gear, and sheering the props." The airplane was recovered by the operator, and moved to a hanger located on the airport. Temporary repairs were made to the airplane's propellers, engines, and nose landing gear, and the airplane was ferried to the operator's maintenance facility in Fairbanks, Alaska. A Federal Aviation Administration (FAA) airworthiness inspector from the Fairbanks Flight Standards District Office inspected the airplane at the operator's facility. He reported that after repairing any damage sustained during the nose landing gear collapse, the Decoto power steering system operated normally. The director of operations for the operator reported to the National Transportation Safety Board investigator-in-charge that during the lengthy repair process, while waiting for parts to arrive to complete the airframe repairs, the airplane was stored outside. He added that the outside air temperature was about minus 15 degrees F. He said that when maintenance personnel engaged the power steering system, with the rudder pedals in the neutral position, the airplane's nose wheel turned full right, hitting the turn stop. The Decoto power steering servo actuator assembly, and power steering amplifier, was removed from the accident airplane, and shipped to Dowty Aerospace Yakima in Yakima, Washington. On March 8, 2001, in the presence of a National Transportation Safety Board investigator, the Decoto power steering servo actuator assembly was placed on a test bench. The servo assembly operated normally at room temperature. The actuator was then placed in a temperature-controlled chamber, and cold-soaked to 0 Degrees F. for 2 hours. The servo was then removed from the chamber, and connected to the amplifier, and the servo assembly operated properly. The actuator was once again placed in the temperature-controlled chamber, and cold soaked to minus 20 degrees F. for 2 hours. The servo was again removed from the chamber, and connected to the amplifier. The servo assembly again operated properly. The servo actuator was then disassembled, with no preaccident anomalies noted. The servo valve, model 30-361, was removed from the servo assembly, and was shipped to MOOG, Inc., in East Aurora, New York. On June 19, 2001, in the presence of a Federal Aviation Administration (FAA) principal avionics inspector from the Rochester, New York, Flight Standards District Office, the servo valve was placed on a test bench, and operated at room temperature. The servo valve operated normally. The servo valve was then placed in a temperature-controlled chamber, cold soaked to 4 Degrees F., and the servo valve operated properly. The servo valve was again placed in the temperature-controlled chamber, cold soaked to minus 20 degrees F., and again the servo valve operated properly. Finally, the servo valve was again placed in the temperature-controlled chamber, heated to 75 degrees F., and again the valve operated normally. The servo valve was then disassembled, with no preaccident anomalies noted. The Cockpit Voice Recorder (CVR) was removed from the accident airplane and sent to the NTSB vehicle recorder laboratory in Washington, DC. A representative from the National Transportation Safety Board, Office of Research and Engineering, reported that the audio recording on the CVR did not offer any additional information that had not already been obtained from the accident flight crew, or other sources in the investigation. Accordingly, no CVR listening group was convened and no transcript was prepared. A summary of the CVR recording is included with this report. The Flight Data Recorder (FDR) was removed from the accident airplane and sent to the NTSB vehicle recorder laboratory in Washington, DC. A representative from the National Transportation Safety Board, Office of Research and Engineering, reported that the FDR data was downloaded using the National Transportation Safety Board's readout equipment. The data was then reduced from the recoded binary values, to engineering units, using formulas supplied by the operator and NTSB software. Ground speed was not a recorded parameter on the FDR installed on the accident airplane. The available information was entered into the NTSB proprietary software program, DANTE, which provided a derived ground speed of about 40 to 50 knots, during activation of the Decoto power steering system. A complete copy of the FDR report is included in this report. The FAA approved airplane flight manual supplement, concerning the operation of the Decoto power steering system, dated March 1992, Limitations, states: "Use of power steering is limited to taxi operations only." The Federal Aviation Administration, Principal Operations Inspector that oversees Frontier Flying Service, said that just after the accident the director of operations circulated a safety notice/letter to all Beech 1900 flight crews stating that activation of the Decoto Power Steering System above a slow taxi speed was prohibited. The Cockpit Voice Recorder (CVR), Flight Data Recorder (FDR), and Decoto power steering servo actuator assembly, were returned to the operator on July 1, 2001.
The flight crew's failure to maintain directional control during the landing roll. A factor associated with the accident was the crew's failure to follow appropriate procedures.
Source: NTSB Aviation Accident Database
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