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General Aviation Safety
On June 4, 2007, about 1600 central daylight time, a Cessna Citation 550, N550BP, impacted Lake Michigan shortly after departure from General Mitchell International Airport, Milwaukee, Wisconsin (MKE).1 The two pilots and four passengers were killed, and the airplane was destroyed. The airplane was being operated by Marlin Air under the provisions of 14 Code of Federal Regulations (CFR) Part 135 and departed MKE about 1557 with an intended destination of Willow Run Airport (YIP), near Ypsilanti, Michigan. At the time of the accident flight, marginal visual meteorological conditions prevailed at the surface, and instrument meteorological conditions prevailed aloft; the flight operated on an instrument flight rules flight plan.
TO THE FEDERAL AVIATION ADMINISTRATION: Require Cessna to reduce the aileron trim sensitivity (the unexpectedly significant aileron trim deflection that results from a relatively small amount of trim knob input) on Citation series airplanes to avoid sudden and excessive aileron trim deflections.
Original recommendation transmittal letter:
Closed - Unacceptable Action
Milwaukee, WI, United States
Loss of Control and Impact with Water, Marlin Air Cessna Citation 550, N550BP
Addressee(s) and Addressee Status:
FAA (Closed - Unacceptable Action)
Safety Recommendation History
Based on recent flight tests to evaluate trim sensitivity and a review of original flight test data, the FAA has concluded that no changes are required to the aileron trim system of any of the Citation series aircraft. The FAA considers its actions in response to this recommendation to be complete. The NTSB continues to believe the recommended action is needed, based on our investigation of the Marlin Air accident in Milwaukee. The investigation found that the aileron trim was easy to set inappropriately, inadvertently creating a hazardous out-of-trim condition. The control knob for the aileron trim system of the accident aircraft was found between a half and a full rotation to the left of the neutral (centered) position. The display in a cable-driven system such as the Cessna Citation 550 commonly does not move smoothly and will jump slightly as the system moves. A ground test conducted as part of the investigation found that a half-turn of the control knob could result in no change to the displayed setting of the trim system. Therefore, the display of a half turn to the left may have indicated that the system was anywhere between the neutral position and a full turn to the left. The owner of the accident airplane related that the trim was so sensitive that he had been surprised once after picking up the airplane from maintenance. In that incident, during the takeoff, the airplane had a strong tendency to roll and he found that a half-knob rotation created the out-of-trim condition. This had occurred at slow speed, and he corrected the out-of-trim condition before the speed, and related control forces, were allowed to increase. We continue to believe that the aileron trim system on the Citation series of airplanes causes an unexpectedly significant amount of aileron trim deflection to result from a relatively small amount of trim knob input. The FAA does not plan to require any changes to these systems, however; consequently Safety Recommendation A-09-122 is classified CLOSED—UNACCEPTABLE ACTION.
From J. Randolph Babbitt, Administrator: We have completed our investigation of this recommendation and have concluded that no changes are required to the aileron trim system of any of the Citation series aircraft. This is based on recent night tests to evaluate trim sensitivity and a review of original flight test data. A flight evaluation was conducted by Cessna and the FAA on June 14, 2010, on Cessna 550 S/N 550-0252. The aileron trim sensitivity was found to be appropriate for its intended use. The pilot must be able to trim out forces in an engine out emergency situation in a timely manner without exceptional effort as required by § 25. 143(b) and § 25.161(d). With a manual trim system, it is expected that the system will be relatively insensitive at low speeds and relatively sensitive at high speeds. The trim sensitivity was found to be similar in all three axes. The FAA and Cessna have not received any reports of aileron trim system sensitivity issues from the field. Further, Cessna's design is consistent with standard design practices for manual trim systems and is a standard design philosophy within Cessna. Therefore, the FAA did not continue this evaluation for other Citation series aircraft. I believe the FAA has effectively addressed this safety recommendation. and I consider our actions complete.
The FAA's plan to perform a flight test in a Cessna Model 550 to investigate the trim travel sensitivity at various airspeeds for both the pitch and roll axis is a first step in responding to this recommendation. The NTSB cautions the FAA that this recommendation applies to the entire Citation series of aircraft, not only to the Model 550. Pending completion of the recommended action, Safety Recommendation A-09-122 is classified OPEN – ACCEPTABLE RESPONSE.
Letter Mail Controlled 5/5/2010 12:17:19 PM MC# 2100167 - From J. Randolph Babbitt, Administrator: The Wichita ACO is working in conjunction with Cessna and will perform a flight test in a Model 550 to investigate the trim travel sensitivity at various airspeeds for both the pitch and roll axis. Once we have completed the testing we will determine the appropriate course of action. I will provide an update on the progress of this safety recommendation by March 2011.
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