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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 redesign and retrofit the yaw damper and autopilot switches on the autopilot control panel in Citation series airplanes to make them easily distinguishable and to guard against unintentional pilot activation.
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
The NTSB notes that the FAA completed its review of accident and incident data associated with the issues in this recommendation. We further note that the FAA did not identify any significant issues attributed to the location and design of the autopilot and yaw damper engage switches and that the autopilot controller installed in the Cessna 550 and other similarly designed controllers have been used in numerous airplanes by many manufacturers for over 30 years. The FAA conducted flight tests on a Cessna Citation 550 and found that the autopilot control panel provides acceptable annunciation of the autopilot and yaw damper engage status. In addition, the FAA believes that an appropriately trained and qualified Cessna Citation 550 flightcrew member is able to distinguish between the autopilot and yaw damper switches and engage them properly. The FAA determined that the yaw damper and autopilot switches on the autopilot control panel in Cessna Citation series airplanes are in compliance with all standards and requirements in effect at the time the airplane was certificated, including 14 CFR Part 25, Section 25.777. The NTSB has previously indicated our belief that the location of the switches is not in compliance with Section 25.777. As a result of its investigation, the FAA does not plan to take the actions in either Safety Recommendation A-09-114 or -115. In the NTSB’s November 17, 2010, letter concerning these recommendations, we stated the following: Although the FAA plans to examine the service history associated with these types of designs, as well as crew indications that alert them to improper switch selection and pilot training, the NTSB believes that the location and arrangement of these switches violate fundamental human factors principles in cockpit design….regardless of the findings related to service history and pilot training, an acceptable response to these recommendations will require revisions to the autopilot controller to bring it into compliance with good human factors design practice. However, the FAA has indicated that it does not plan to take the recommended actions; consequently, Safety Recommendations A-09-114 and -115 are classified CLOSED—UNACCEPTABLE ACTION.
From J. Randolph Babbitt, Administrator: Our review of the Board's aviation accident database and Federal Aviation Administration's (FAA) Service Difficulty Report database on the Cessna 550 did not identify any significant issues attributed to the location and design of the autopilot and yaw damper engage switches. The Honeywell (Sperry) SPZ-500 autopilot controller installed in the Cessna 550 and other similarly designed controllers provided by Honeywell, have been used in numerous airplanes by many manufacturers for over 30 years. The design was found to be in compliance with the applicable part 25 standards in effect at the time of certification. The grouping of the autopilot and yaw damper switches is an accepted design feature. This grouping has been incorporated, not only on older airplanes, but on more recently certified aircraft and aircraft currently in development. Our research revealed that the Honeywell, Collins, and Garmin autopilot and yaw damper switches are grouped in a manner similar to the Cessna 550. These can be found on the ATR 72. Bombardier Global Express, Cessna 52SC, Cessna 510, Cessna 560, Hawker Bccchcraft 400A, Hawker Becchcraft 850XP, Beechcrart 4000, Embraer ERJ-190, Learjet 31A, and Learjet 85. On June 14.2010, we conducted flight tests using a Cessna 550 S/N 550-0252. An FAA flight test pilot reexamined the autopilot control panel and determined it provides acceptable annunciation of the autopilot and yaw damper engage status. We verified that there is sufficient tactile and visual feedback through the yoke, flight director (FD) commands, and FD mode annunciations to provide adequate indication when the autopilot or FD is engaged. If the autopilot were unintentionally engaged, in addition to the annunciation on the autopilot control panel, the unresolved commands on the flight director would provide visual information to the pilot that the autopilot/FD was engaged. Pressing the autopilot/trim disengage switch, the go around switch, or the pitch trim switch on the pilot's control wheel would disengage the autopilot. The pilot in command of a Cessna 550 is required to be type rated and trained in the operation or all systems per the requirements or part 61. A properly trained and current flightcrew must be familiar with the operational procedures for engaging the autopilot and yaw damper and the associated autopilot and yaw damper indications. Appropriately trained flightcrew members are able to distinguish between the autopilot and yaw damper switches and engage them properly. We have completed our investigation and have concluded that a redesign of the autopilot control panel on the Cessna Citation series is not warranted. I believe the FAA has effectively addressed this safety recommendation, and I consider our actions complete.
The NTSB notes the FAA's statement that the autopilot controller used on the Sperry/Honeywell autopilots installed on the Cessna Citation is used on numerous airplanes by many manufacturers and that the design and grouping of the autopilot and yaw damper switches is a standard design used on many other Sperry/Honeywell autopilot systems. Although the FAA plans to examine the service history associated with these types of designs, as well as crew indications that alert them to improper switch selection and pilot training, the NTSB believes that the location and arrangement of these switches violate fundamental human factors principles in cockpit design. In addition, as the letter that transmitted these recommendations to the FAA indicated and as the FAA stated in its response, the location and operation of the switches on the autopilot controller are not in compliance with 14 CFR Part 25, Section 25.777. The review that the FAA has initiated is a necessary first step in issuing the requirements recommended, but regardless of the findings related to service history and pilot training, an acceptable response to these recommendations will require revisions to the autopilot controller to bring it into compliance with good human factors design practice and Section 25.777. Accordingly, pending completion of the actions recommended, Safety Recommendations A-09-114 and -115 are classified OPEN – ACCEPTABLE RESPONSE.
Letter Mail Controlled 5/5/2010 12:17:19 PM MC# 2100167 - From J. Randolph Babbitt, Administrator: The Sperry/Honeywell PC-500 autopilot controller on the Model 550 is used on numerous airplanes by many manufacturers. The design and grouping of the autopilot and yaw damper switches is a standard design used on many other Sperry/Honeywell autopilot systems. Therefore, we will examine the service history associated with these types of designs in an attempt to identify any types of deficiencies. We will examine the crew indications that alert them to the potential of an improper switch selection. We will look at pilot training requirements and how that factors into the familiarity and operation of the aircraft systems. Once we have completed our investigation 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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