Discussion
What events have caused this AD? The FAA has received several reports of severe corrosion being found throughout the wing center section of Univair Models Alon A-2 and A2-A; ERCO 415-C, 415-CD, 415-D, 415-E, and 415-G; Forney F-1 and F-1A, and Mooney M10 airplanes. We have determined that the original design configuration of these airplanes does not provide adequate means for routine visual inspection of the wing center section wing walkway boxes. The inability to inspect this area has resulted in corrosion being undetected on these airplanes.
What is the potential impact if FAA took no action? If corrosion is not detected and corrected, the wing center section structure could fail during flight. Such failure could lead to loss of control of the airplane.
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 Univair Models Alon A-2 and A2-A; ERCO 415-C, 415-CD, 415-D, 415-E, and 415-G; Forney F-1 and F-1A; and Mooney M10 airplanes. This proposal was published in the Federal Register as a notice of proposed rulemaking (NPRM) on April 3, 2002 (67 FR 15763). The NPRM proposed to require the following:
--Repetitively inspect the wing center section for evidence of corrosion through the installation of inspection openings, through the use of a specified scope and light source, or through the removal of the outer wing panels;
--Install cover plate assemblies if inspection openings were made; and
--Repair or replace any parts where corrosion or corrosion damage was found.
Was the public invited to comment? The FAA encouraged interested persons to participate in the making of this amendment. The following presents the comments received on the proposal and FAA's response to each comment:
Comment Issue No. 1: Add Additional Method for Accomplishing the Inspection
What is the commenter's concern? Several commenters state that the two methods specified in the NPRM are an economic burden, impact the aesthetic and structural appearance of the airplane, and/or reduce the structural integrity of the wings. Several of the commenters state that the cost of the scope and light source necessary to perform the inspection is much more expensive than that stated in the NPRM, and that installing inspection openings in the wings will reduce the structural integrity of the wings.
The commenters request to have a third method added to the AD that allows for removing the outer wing panels from the airplane to accomplish the inspections. The commenters also state that this method is less of an economic burden and feel it is more effective than the two methods proposed in the NPRM.
What is FAA's response to the concern? We concur that a third inspection method option should be added to the AD.
The manufacturer has revised the service bulletin to incorporate this additional method, and we will incorporate the new service bulletin into the final rule AD action.
We also have verified that the Olympus OSF Endoscope (sigmoidoscope) with a Fujinon FIL-150 light source, as specified in Note 1 of the NPRM, is available for the cost stated in the NPRM.
We will change the final rule AD action to incorporate Revision 1 of Univair Service Bulletin 31.
Comment Issue No. 2: Change the Repetitive Inspection Compliance Time
What is the commenter's concern? Several commenters state that the majority of the airplanes affected by this AD are over 40 years old with no history of corrosion problems in the wing center section. Therefore, once the initial inspection has been performed and no corrosion is found, the commenters do not believe that corrosion would become an unsafe condition within the next 12 months or 100 hours time-in-service (TIS). The commenters suggest that a 3 year or a 5 year repetitive interval will be more than adequate.What is FAA's response to the concern? We agree with the commenters. The initial inspection compliance time will remain the same; however, we will change the repetitive inspection intervals to be every 3 years.
We will change the final rule AD action to incorporate this change.
Comment Issue No. 3: Service Bulletin Unavailable
What is the commenter's concern? Several commenters state that Univair was unable to provide them with a copy of the service bulletin referenced in the NPRM. Therefore, the commenters were unable to provide comments related to the actions required by the service bulletin as stated in the NPRM. We infer that the commenters want the NPRM withdrawn because they could not obtain the service bulletin.
What is FAA's response to the concern? We do not concur. We understand the concerns of the commenters. However, we cannot require accomplishment of any action in accordance with a supplemental document, i.e., manufacturer's service bulletin, unless wehave an approved original copy submitted to FAA from the manufacturer. The service bulletin referenced in the NPRM is an official part of the rules docket and was available during the comment period at the offices specified in the ADDRESSES paragraph in the NPRM.
We are not changing the final rule AD action based on this comment.
Comment Issue No. 4: Remove the Mooney Model M10 Airplanes From the Applicability
What is the commenter's concern? The commenter states that the Mooney rear spar can be readily inspected after the seats and baggage compartment floor are removed. This makes it is unnecessary to install inspection holes in the skin on this airplane. The commenter wants Mooney Model M10 airplanes removed from the applicability section of the final rule AD action.
What is FAA's response to the concern? We do not concur. Corrosion or corrosion damage can occur on the Mooney Model M10 airplanes, and owners/operators of the affected airplanes have two other methods to use for accomplishing the inspection requirements of this AD without installing inspection holes.
We are not changing the final rule AD action based on this comment.
Comment Issue No. 5: AD Is Not Warranted
What is the commenter's concern? Several commenters state that, as long as the airplane has been properly maintained (using existing procedures) and properly stored, there should not be a problem with corrosion build-up in the wing center section. Also, the commenters state that the NPRM was issued based on an isolated case of corrosion being found on an airplane that was improperly maintained and stored. The commenters don't believe there is enough evidence to warrant AD action against the entire fleet. Therefore, the commenters recommend that FAA withdraw the NPRM.
What is FAA's response to the concern? We do not concur that the NPRM should be withdrawn. We have 27 documented cases, from 1974 to the present, of corrosion found throughout the wing componentsand other parts of the airframe. Our analysis indicates that normal maintenance procedures and methods do not allow for the detection of corrosion in the wing center section of the affected airplanes.
We are not changing the final rule AD based on these comments.
FAA's Determination
What is FAA's final determination on this issue? After careful review of all available information related to the subject presented above, we have determined that air safety and the public interest require the adoption of the rule as proposed except for the addition of another method to be used for accomplishing the inspection, changing the compliance time for the repetitive inspection intervals, and minor editorial corrections. We have determined that these changes and minor corrections:
--Provide 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.
Cost ImpactHow many airplanes does this AD impact? We estimate that this AD affects 2,600 airplanes in the U.S. registry.
What is the cost impact of this AD on owners/operators of the affect airplanes? We estimate the following costs to accomplish the installation of the inspection openings:
Labor cost
Parts cost
Total cost per airplane
10 workhours x $60 per hour = $600
$175
$775
We estimate the following costs to accomplish the inspection using a scope and light source:
Labor cost
Parts cost
Total cost per airplane
Total cost on U.S. operators
2 workhours x $60 per hour = $120.
$450 for purchase of a borescope or an endoscope, if applicable.
$120 or $570
$120 x 2,600 = $312,000 or
$570 x 2,600 = $1,482,000.
We estimate the following costs to accomplish the inspection by removing the outer wing panel:
Labor cost
Parts cost
Total Cost per airplane
Total Cost on U.S. operators
5 workhours x $60 per hour = $300
Not applicable
$300
$300 x 2,600 = $780,000.
The FAA has no method of determining the number of repetitive inspections each owner/operator will incur over the life of each of the affected airplanes so the cost impact is based on the initial inspection.
The FAA has no method of determining the number of repairs or replacements each owner/operator will incur over the life of each of the affected airplanes based on the results of the inspections. We have no way of determining the number of airplanes that may need such repair. The extent of damage may vary on each airplane.
Compliance Time of This AD
What would be the compliance time of this AD? The compliance time of this AD is "within the next 12 calendar months after the effective date of this AD and thereafter at intervals not to exceed 3 years."
Why is the compliance time presented in calendar time instead of hours time-in-service (TIS)? The unsafe condition specified by this AD is caused by corrosion. Corrosion can occur regardless of whether the airplane is in operation or is in storage. Therefore, to assure that the unsafe condition specified in this AD does not go undetected for a long period of time, the compliance is presented in calendar time instead of hours TIS.
Regulatory Impact
Does this AD impact various entities? 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.
Does this AD involve a significant rule or regulatory action? For the reasons discussed above, I certify that this action (1) Is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have asignificant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A copy of the final evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting 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, 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: