The FAA has received a report of an accident involving a Cessna Model 525 airplane. The pilot reported a problem with the trim system and was forced to ditch the airplane in the water near Coupeville, Washington. Although the final investigation by the National Transportation Safety Board is not complete, investigation revealed a discrepancy that could allow single-wire shorting to 28 volts or the failure of a relay in the trim system such that the relay contacts remain closed. In addition, the pilot may be unable to stop the runaway trim condition by pressing the red autopilot-disconnect switch located on the control wheel, due to the design of the trim system on a certain serial number range of airplanes. A runaway trim condition that the pilot is unable to stop by using the autopilot- disconnect switch could result in loss of control of the airplane.
The design of the trim system on certain Cessna Model 560 airplanes is the same as that on certain Cessna Model 525 airplanes. Therefore, Model 560 airplanes may be subject to the same unsafe condition.
Explanation of Relevant Service Information
We have reviewed and approved Cessna Alert Service Letter ASL560- 27-10, dated October 10, 2003. Among other actions, that service letter describes procedures for disengaging the pitch trim and autopilot (AP) servo (servo 1) circuit breakers and tie-strapping those circuit breakers so that they may not be engaged. Accomplishment of these actions specified in the service letter is intended to adequately address the identified unsafe condition.
Cessna Alert Service Letter ASL560-27-10 also describes procedures for an inspection to determine the part number of the installed trim pc board assembly, and follow-on actions. The follow-on actions include replacement of the assembly with an improved assembly and installation of an extension cap on the pitch trim circuit breaker, as applicable. Once the inspection and applicable follow-onactions have been accomplished, the tie straps on the pitch trim and AP servo circuit breakers may be removed and those circuit breakers may be re-engaged.
Explanation of the Requirements of the Rule
Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design registered in the United States, this AD requires disengaging and tie-strapping the pitch trim and AP servo circuit breakers. This AD also provides for an optional inspection and follow-on actions that terminates the requirement for disengaging and tie-strapping those circuit breakers. These actions must be accomplished per the service letter described previously, except as discussed below.
Differences Between This AD and Service Letter
Although the service letter requires that the disengaging and tie- strapping of the pitch trim and AP servo circuit breakers be accomplished upon receipt of the service letter, this AD allows accomplishment of these actions within 5 days or 10 hours time-in- service after the effective date of this AD, whichever is first. We find that such a compliance time represents an appropriate compliance time for affected airplanes to continue to operate without compromising safety.
Although the service letter is effective for certain Model 560 airplanes having serial numbers 0260 through 0538 inclusive, this AD is applicable to certain Model 560 airplanes having serial numbers 0260 through 0396 inclusive. While the discrepancy that could allow a single-point failure in the trim system, causing a runaway trim condition, may occur on any airplane having a serial number in the range 0260 through 0538 inclusive, on airplanes having serial numbers 0397 through 0538 inclusive, the pilot would be able to stop the runaway trim condition by pressing the red autopilot-disconnect switch located on the control wheel. Therefore, we have determined that an acceptable level of safety exists on airplanes having serialnumbers 0397 through 0538 inclusive, and it is not necessary to require disengaging and tie-strapping of the pitch trim and AP servo circuit breakers on these airplanes at this time.
Although the Accomplishment Instructions of the service letter describe procedures for sending a maintenance transaction report to the manufacturer, this AD does not require this action.
Interim Action
We consider this proposed AD interim action. We are currently considering requiring the optional terminating action provided in this AD--inspection of the trim pc board assembly and follow-on actions, which would eliminate the need for the tie straps on the pitch trim and AP servo circuit breakers, and would allow those circuit breakers to be re-engaged. However, the planned compliance time for such actions would likely allow enough time to provide notice and opportunity for prior public comment on the merits of those actions.
Determination of Rule's Effective Date
Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days.
Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption ADDRESSES. All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.
Submit comments using the following format:
Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
For each issue, state what specific change to the AD is being requested.
Include justification (e.g., reasons or data) for each request.
Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 2003-NM-225-AD." The postcard will be date stamped and returned to the commenter.
Regulatory Impact
The regulations adopted herein will not have a substantial direct effect on the States, on the relationship between the national Government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, it is determined that this final rule does not have federalism implications under Executive Order 13132.
The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption ADDRESSES.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
39.13 [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive: