Discussion \n\n\tHas FAA taken any action to this point? The FAA issued AD 80-04-08, Amendment 39-3696, February 16, 1980, in order to preclude the possibility of a fuel leak or an in-flight fire due to contact between a map light switch and an adjacent fuel line of certain Cessna Models 172N, R172K, F172N, and FR172K airplanes. AD 80-04-08 requires that you do the following on the affected airplanes: \n\n\t--Visually inspect the fuel line and map light switch located in the left hand forward door post for chafing or arcing and replace damaged parts as necessary. If not already existing, provide at least a 0.50-inch clearance between the map light switch and the fuel line in accordance with procedures in FAA Advisory Circular 43.13-1A.\n\n\t--Install a cover (insulator), Cessna Part Number 0511080-1, over the map light switch in accordance with Cessna Single Engine Service Information Letter SE80-3 and Supplement #1 thereto, both dated January 21, 1980.AD 80-04-08 was the result of instances of chafing between the map light switch and the adjacent fuel line on the affected airplanes. When the chafing caused an electrical short, insulation melted from the map light wire and a hole was burned in the fuel line. \n\n\tWhat has happened to necessitate further AD action? Since issuance of AD 80-04-08, FAA has received several reports of incidents of electrical shorts on Cessna Model 172N airplanes. These electrical shorts have resulted because the mounting screws may be elongated or broken out on the affected airplanes or doorpost cover shapes have changed over time. Switch covers may: \n\n\t--Deteriorate over time; \n\n\t--Receive damage from service activities, \n\n\t--Be left off after service activities; \n\n\t--Not be mounted properly; or \n\n\t--Not be used in after-market interior installations. \n\n\tAD 80-04-08 applied to only certain serial numbers and did not cover all of the models that have map light switches in the doorpost. \n\n\tHas 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 172N, 172P, R172K, 172RG, F172N, F172P, FR172J, and FR172K series airplanes. This proposal was published in the Federal Register as a notice of proposed rulemaking (NPRM) on January 8, 2001 (66 FR 1273). The NPRM proposed to supersede AD-80-04-08 with a new AD that would require: \n\n\t--Repetitively inspecting for the existence and damage to the cover (insulator) for the doorpost map light switch; \n\n\t--Installing a cover (insulator) if missing or damaged; and --Replacing the fuel line, if damaged. \n\n\tWas the public invited to comment? The FAA encouraged interested persons to participate in the making of this amendment. At the request of several commenters, we issued an NPRM to extend the comment period from February 12, 2001, to April 13, 2001. This document was published in the Federal Register on February 12, 2001 (66 FR 9779). A summary of the comments received on both of these documents follow, along with our responses. \n\nComment Issue No. 1: Agree That This AD Will Correct an Unsafe Condition and Provide Aviation Safety \n\n\tWhat is the commenter's concern? One commenter suggests that the proposed AD is necessary because the doorposts in these aircraft have become conduits for wiring of add-on systems accomplished by the field approval process. The commenter suggests that repetitive inspections would significantly enhance the safety and reliability of airplane operation. \n\n\tSeveral commenters agree that FAA is correct in adding aircraft serial numbers to the proposed AD.\n\n\tWhat is FAA's response to the concern? Since the comments agree with the NPRM as written, we are not changing the final rule as a result of these comments. \n\nComment Issue No. 2: AD 80-04-08 Already Addresses the Unsafe Condition \n\n\tWhat is the commenter's concern? Several commenters suggest that a new AD is not necessary to correct the unsafe condition. They believe AD 80-04-08 adequately addresses this issue. The commenters suggest that if any further action regarding this unsafe condition is taken, FAA should either revise or suspend the current AD. Two commenters suggest that accomplishment of the manufacturer's service bulletin by the owners/operators of the affected airplanes will correct the unsafe condition. \n\n\tWhat is FAA's response to the concern? We do not concur that AD 80-04-08 addresses the unsafe condition. Reports indicate electrical shorts on Cessna Model 172N airplanes have occurred after compliance with AD 80-04-08. We have determined that the electrical shorts resulted because the doorpost cover deteriorated over time from heat and sunlight, which caused the attachment bolt holes to become elongated or broken out and resulted in the fuel line and the switch contact to become jammed together. AD 80-04-08 did not cover all of the airplane models that have map light switches in the doorpost. In addition, AD 80-04-08 only required an initial inspection so no requirement exists for detecting damaged doorpost covers that occur after the initial inspection. Since we are adding additional requirements and additional airplanes, we must supersede the current AD because it provides an additional burden over that in AD 80-04-08. \n\n\tWe concur that accomplishment of the referenced service bulletin will correct the unsafe condition. However, we can only require compliance through AD action. \n\n\tWe are not changing the AD based on these comments. \n\nComment Issue No. 3: The Condition Results From Poor or Lack of Maintenance \n\n\tWhat is the commenter's concern? Several commenters suggest that the conditions referenced in the proposed AD are a result of incorrect maintenance activities. The commenters state that, if damage to the doorpost cover is a result of maintenance activities, e.g., left off or not properly mounted, an AD would not correctthis situation. These conditions result from incorrect aircraft maintenance and airframe and powerplant (A&P) mechanic functions and not AD requirements. If these problems arise, the pilot should report the condition so that corrective maintenance can be performed. \n\n\tWhat is FAA's response to the concern? We do not concur. The unsafe condition is a result of the doorpost cover deteriorating over time because of the material it is made of, exposure to the heat, and use. The deterioration of the doorpost cover causes the attachment bolt holes to become elongated or broken out, which results in the fuel line and the switch contact to become jammed together. \n\n\tWe are not changing the AD based on these comments. \n\nComment Issue No. 4: Correct the Applicability \n\n\tWhat is the commenter's concern? Several commenters suggest that FAA should clarify whether Model F172N airplanes, serial numbers F17201515 through F17201639, should be included in the AD. We infer that the commenters believe that they should be included. \n\n\tWhat is FAA's response to the concern? We concur. We inadvertently left Model F172N airplanes, serial numbers F17201515 through F17201639, out of the proposed AD. These airplane models will be covered in the applicability of this AD. \n\n\tWe are changing the final rule to include these airplane models. None of these airplanes are currently on the U.S. Register so this would not add any additional burden upon the public. \n\nComment Issue No. 5: Extend the Comment Period 60 Days \n\n\tWhat is the commenter's concern? Two commenters request the comment period be extended to allow the FAA a greater opportunity to hear from more people in the aviation community. \n\n\tWhat is FAA's response to the concern? We concur with this comment. The comment period was extended on the NPRM from February 12, 2001, to April 13, 2001, to give the public an additional 60 days to respond. \n\nComment Issue No. 6: Change or Eliminate the Repetitive Inspection IntervalWhat is the commenter's concern? Several commenters suggest that the need for repetitive inspections are not necessary because they add no safety value. Specifically, one commenter suggests that the doorpost cover, switch, insulator, and fuel line should be inspected as part of the annual inspection (or when any work is performed in that area) or extended to 5 year intervals because the material the doorpost cover is made of will not deteriorate in a year's time. Another commenter suggests that the affected area is not designed for repeated access and could, in fact, contribute to and exacerbate the problem addressed by the proposed AD or create new ones. All commenters suggest that if required maintenance is done properly, there would be no need for repetitive inspections because the switch retaining screws will remain installed until they are removed; and, if installed correctly, the insulator is designed as such that it will function properly until it is removed. \n\n\tWhat is FAA's response to the concern? We do not concur. As discussed previously, electrical shorts result because the doorpost cover deteriorates over time from heat and sunlight. Our analysis shows that 12 months is a reasonable time period for detecting such a problem. A longer period would not provide the assurance that the condition was detected before a serious problem developed. We have determined that, if correctly accessed, new problems will not occur. The 12 month repetitive inspection interval should also coincide with annual inspections. \n\n\tWe are not changing the final rule as a result of these comments. \n\nFAA's Determination \n\n\tWhat 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 minor editorial corrections. We determined that these minor corrections: \n\n\t--Will not change themeaning of the AD; and \n\n\t--Will not add any additional burden upon the public than was already proposed. \n\nCost Impact \n\n\tHow many airplanes does this AD impact? We estimate that this AD affects 7,750 airplanes in the U.S. registry. \n\n\tWhat is the cost impact of this AD on owners/operators of the affected airplanes? We estimate the following costs to accomplish the initial inspection: \n\n\n\nLabor cost \n Parts cost \nTotal cost per airplane\nTotal cost on U.S. operators\n1 workhour x $60 per hour =$60. \nNo parts required for the inspection.\n$60\n7,750 x $60 = $465,000. \n \n\tThe FAA has no way of determining the number of repetitive inspections each owner/operator will incur over the life of each of the affected airplanes, or how many covers (insulators) or fuel lines will need to be replaced. If replacement parts are required as a result of the inspection, the estimated cost per airplane for the cover (insulator) is $6.00. The cost for a replacement fuel line varies from $26.00 to $129.00, plus labor, depending on the airplane model. \n\n\tWhat is the difference between the cost impact of this AD and the cost impact of AD 80-04-08? The cost impact of this AD is more than currently required by AD 80-04-08. The differences between this AD and AD 80-04-08 are the additional airplane models that will be affected and the repetitive inspections each affected airplane owner/operator will incur over the life of the airplane. \n\nRegulatory Impact \n\n\tDoes 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. \n\n\tDoes 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 a significant 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. \n\nList of Subjects in 14 CFR Part 39 \n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the Amendment \n\n\tAccordingly, 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: \n\nPART 39--AIRWORTHINESS DIRECTIVES \n\n\t1. The authority citation for part 39 continues to read as follows: \n\n\tAuthority: 49 U.S.C. 106(g), 40113, 44701. \n\nSec. 39.13 (Amended) \n\n\t2. FAA amends Sec. 39.13 by removing Airworthiness Directive (AD) 80-04-08, Amendment 39-3696, and by adding a new AD to read as follows: