Discussion
What events have caused this AD? The FAA has received several reports of rudder tube and rib corrosion on Piper PA-31 Series airplanes. The area surrounding the rudder torque tube assembly and rudder rib does not have a means or access to inspect in this area and neither means nor exits for water to drain out.
What is the potential impact if FAA took no action? Corrosion in the rudder torque tube assembly and rudder rib could result in failure of the rudder torque tube. This failure could lead to loss of rudder control.
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 all Piper Models PA-31, PA-31-300, PA-31-325, PA-31-350, PA-31P, PA-31T, PA-31T1, PA-31T2, PA-31T3, and PA-31P-350 airplanes. This proposal was published in the Federal Register as a notice of proposed rulemaking (NPRM) on June 3, 2003 (68 FR 33030). The NPRM proposed to require you to install an inspection hole, conduct a detailed visual inspection of the rudder torque tube and associated ribs for corrosion, and, if corrosion is found, replace the rib/rudder torque tube assembly.
Comments
Was the public invited to comment? We provided the public the opportunity to participate in the development of this AD. The following presents the comments received on the proposal and FAA's response to each comment:
Comment Issue No. 1: Extend the Compliance Time
What is the commenter's concern? A commenter recommends extending the compliance time from 100 hours time-in-service (TIS) to 150 hours TIS. The commenter states that the extension is necessary due to a reported lack of parts and the difficulty in scheduling involved with AD compliance.
What is FAA's response to the concern? The FAA agrees that 150 hours TIS would be a more realistic compliance time.
We are changing the final rule AD action accordingly.Comment Issue No. 2: Allow Option to Repair Parts
What is the commenter's concern? The commenter recommends the following: if you find "light corrosion" or "corrosion that could significantly weaken the rib/rudder torque tube assembly that is less than 50 percent of the thickness over an area less than two square inches' then you may clean up, repair, and coat the corroded area to prevent further damage and continue the part in service.
What is FAA's response to the concern? The FAA is currently unaware of any approved repair design for the rib/rudder torque tube assembly. However, FAA has no objection to operation of aircraft with parts that have been repaired or reworked per an FAA-approved repair design.
Therefore, we are changing the final rule AD action to provide the option of repairing with an FAA-approved design.
Comment Issue No. 3: Special Flight Permits Are Not Addressed in the NPRM
What is the commenter's concern? The commenter states that since special flight permits are not addressed in the NPRM, the current 14 CFR part 39 applies and that there is no restriction against issuing a special flight permit.
What is FAA's response to the concern? On July 10, 2002, the FAA published a new version of 14 CFR part 39 (67 FR 47997, July 22, 2002), which governs the FAA's AD system. This regulation now includes material that relates to special flight permits. This material previously was included in each individual AD. Since this material is included in 14 CFR part 39, we did not include it in this AD action.
We are not making any changes to the final rule AD action.
Comment Issue No. 4: Allow an Alternate Method of Inspection
What is the commenter's concern? The commenter suggests an alternative to installing an inspection hole in the rudder skin for the rudder torque tube assembly. This alternative method of inspection is to use the tooling hole in the rudder bottom rib since this is convenient and does not contributeto corrosion. Further, you could enlarge the tooling hole to ease use of inspection tools.
What is FAA's response to the concern? The FAA agrees that the proposed alternative use of the tooling hole (with optional enlargement) in the rudder bottom rib is an acceptable substitute to installing an access hole.
We are changing the final rule AD action accordingly.
Comment Issue No. 5: Allow Application of Corrosion Inhibitor
What is the commenter's concern? The commenter recommends allowing application of rust inhibitor compound.
What is FAA's response to the concern? The application of rust inhibitor compound to the contact surfaces is identified in Piper Service Bulletin No. 1105A, dated September 22, 2003. As a minor correction, we are also noting to protect bare metal per Section 8, FAA Advisory Circular (AC) 43.13-1B.
We are incorporating the referenced correction in the final rule AD action.
Conclusion
What is FAA's final determination on thisissue? We have carefully reviewed the available data and determined that air safety and the public interest require adopting the AD as proposed except for the changes discussed above and minor editorial corrections. We have determined that these changes and 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), which governs 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 2,269 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 installation of inspection and drain holes and inspection of torque tube and associated ribs for corrosion:
Labor cost
Parts cost
Total cost per airplane
Total cost on U.S. operators
3 workhours x $60 per hour = $180.
$10
$190
2,269 x $190 = $431,110
We estimate the following costs to accomplish any necessary corrosion repairs/replacements of the rib/torque tube assembly that would be required based on the results of this proposed inspection. We have no way of determining the number of airplanes that may need this repair/replacement:
Labor cost
Parts cost
Total cost per airplane
16 workhours x $60 per hour = $960
$800
$1,760
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 "2003-CE-03-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.
39.13 [Amended]
2. FAA amends 39.13 by adding a new AD to read as follows: