Discussion
What events have caused this AD? A report of an accident involving a Cessna Model 525 airplane where the pilot reported a problem with the pitch trim system, and later Cessna and FAA analysis that revealed the potential for a single-wire shorting caused us to issue AD 2003-21-07, Amendment 39-13342 (68 FR 60028, October 21, 2003). AD 2003-21-07 currently requires you to do the following on Cessna Model 525 airplanes:
--Disengage the pitch trim circuit breaker and AP servo circuit breaker; and
--Tie strap each of them to prevent them from being engaged.
What has happened since AD 2003-21-07 to initiate this action? AD 2003-21-07 is considered an interim action since compliance corrected the condition where the control wheel autopilot/trim disconnect switch did not stop the runaway condition. However, AD 2003-21-07 did not correct the issue of the single-point failure while still utilizing the desired equipment. Cessna has now developed and made changes in the design of the affected trim printed circuit board (PCB) assembly to eliminate the single-point failure while allowing the use of the equipment, and identified additional airplanes that have the same unsafe condition.
What is the potential impact if FAA took no action? Failure of the electric trim system would result in a large pitch mistrim and would cause excessive control forces that the pilot could not overcome.
Has FAA taken any action to this point? We issued a proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to certain Cessna Model 525 airplanes. This proposal was published in the Federal Register as a notice of proposed rulemaking (NPRM) on February 11, 2004 (69 FR 6585). The NPRM proposed to supersede AD 2003-21-07 with a new AD that would require you to:
--Remove any 6518351-3 or 6518351-5 trim PCB assembly and replace with a 6518351-10 (EX) trim PCB assembly; or
--Modify the 6518351-8 trim PCB assembly to a 6518351-10 trim PCB assembly.
Comments
Was the public invited to comment? We provided the public the opportunity to participate in developing this AD. We received no comments on the proposal or on the determination of the cost to the public.
Conclusion
What is FAA's final determination on this issue? We have carefully reviewed the available data and determined that air safety and the public interest require adopting the AD as proposed except for minor editorial corrections. We have determined that these minor corrections:
--Are consistent with the intent that was proposed in the NPRM for correcting the unsafe condition; and
--Do not add any additional burden upon the public than was already proposed in the NPRM.
Changes to 14 CFR Part 39--Effect on the AD
How does the revision to 14 CFR part 39 affect this AD? On July 10, 2002, the FAA published a new version of 14 CFR part 39 (67 FR 47997, July 22, 2002), whichgoverns the FAA's AD system. This regulation now includes material that relates to altered products, special flight permits, and alternative methods of compliance. This material previously was included in each individual AD. Since this material is included in 14 CFR part 39, we will not include it in future AD actions.
Costs of Compliance
How many airplanes does this AD impact? We estimate that this AD affects 251 airplanes in the U.S. registry.
What is the cost impact of this AD on owners/operators of the affected airplanes? We estimate the following costs to accomplish the modification of the 6518351-8 trim PCB assembly to a 6518351-10 trim PCB assembly. We have no way of determining the number of airplanes that may need this modification:
Labor cost
Parts cost
Total cost per airplane
4 workhours x $65 per hour = $260
$2,995
$2,995 + $260 = $3,255.
We estimate the following costs to accomplish the replacement of any 6518351-3 or 6518351-5 trim PCB assembly with a 6518351-10 (EX) trim PCB assembly. We have no way of determining the number of airplanes that may need this replacement:
Labor cost
Parts cost
Total cost per airplane
2 workhours x $65 per hour = $130
$2,995
$2,995 + $130 = $3,125.
What is the difference between the cost impact of this AD and the cost impact of AD 2003-21-07? The estimated cost impact of AD 2003-21- 07 on each of the 116 airplanes in the U.S. registry affected by AD 2003-21-07 is $65. This is to disengage the pitch trim circuit breaker and AP servo circuit breaker and then tie strap each of them to prevent them from being engaged.
The estimated cost of this AD is $3,125 or $3,255 on each of 251 airplanes in the U.S. registry to do the replacement or modification of the trim PCB assembly.
Compliance Time of This AD
What is the compliance time of this AD? The compliance time of this AD is "within the next 24 calendar months after the effective date of this AD or within 300 hours time-in-service (TIS) after the effective date of this AD, whichever occurs first."
Why is the compliance time of this AD presented in both hours TIS and calendar time? A single-wire shorting to 28 volts or a failure of a relay that results in the relay contacts remaining closed is a direct result of airplane operation. For example, either failure could occur on an affected airplane within a short period of airplane operation while you could operate another affected airplane for a considerable amount of time without experiencing either failure. Therefore, to assure that either failure is detected and corrected in a timely manner without inadvertently grounding any of the affected airplanes, we are using a compliance time based upon both hours TIS and calendar time.
Regulatory Findings
Will this AD impact various entities? We have determined that this AD will not have federalism implications under Executive Order 13132. This AD 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.
Will this AD involve a significant rule or regulatory action? For the reasons discussed above, I certify that this AD:
1. Is not a "significant regulatory action" under Executive Order 12866;
2. Is not a "significant rule" under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and
3. Will not have a significant economic impact, positive or negative, on a substantial number of small entities
under the criteria of the Regulatory Flexibility Act.
We prepared a summary of the costs to comply with this AD and placed it in the AD Docket. You may get a copy of this summary by sending a request to us at the address listed under ADDRESSES. Include "AD Docket No. 2003-CE-54-AD" in your request.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, under 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.
Sec. 39.13 [Amended]
2. The FAA amends Sec. 39.13 by removing Airworthiness Directive (AD) 2003-21-07, Amendment 39-13342 (68 FR 60028, October 21, 2003), and by adding a new AD to read as follows: