A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to all Boeing Model 737 series airplanes was published in the Federal Register on June 2, 1995 (60 FR 28763). That action proposed to require revising the Emergency Procedures and Limitations Sections of the FAA- approved Airplane Flight Manual (AFM) to provide the flightcrew with these additional procedures for shutting down the APU when an APU fire is indicated. \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. \n\n\tThree commenters support the proposed rule. \n\n\tOne commenter requests that the requirements of the proposed AD be made a reference procedure found both in the AFM and the Quick Reference Handbook, rather than "recall items" in the Limitations section of the AFM. The commenter does notprovide justification for its request. The FAA concurs partially. The FAA finds that the operational procedure should be included in the Emergency Procedures Section of the AFM; however, the procedure should not be included in the Limitations Section. Further, the FAA finds that inclusion of the procedure in the Quick Reference Handbook, as suggested by the commenter, will not adequately address the recall requirement of this AD. The FAA has determined that any hesitation on the part of the flightcrew with regard to taking action to shut down the APU in the event of an APU fire could jeopardize safe flight and landing of the airplane. The FAA finds it critical that the flightcrew commit such procedures to memory; therefore, these procedures must be considered recall items. Paragraph (a) of the final rule has been revised to remove the requirement to include the operational procedure in the Limitations Section of the AFM. \n\n\tOne commenter agrees that the AFM should be revised toincorporate the additional procedures specified in the proposed rule. However, the commenter states that the unsafe condition addressed by the proposal does not warrant issuance of an AD. The commenter suggests that Boeing revise the AFM to incorporate the proposed additional procedures, which would negate the cost of AD compliance paperwork for both the FAA and operators while providing an equivalent level of safety. The commenter adds that incorporation of the additional procedures into operators' manuals (through Boeing issuing a revision to the master AFM) would be more expeditious than the FAA issuing an AD with a 6-month compliance period. \n\n\tThe FAA does not concur with the commenter's position that issuance of an AD is not warranted. As stated in the preamble of the proposed rule, the FAA received reports indicating that a latent electrical failure exists in the fire extinguishing system of the APU on the affected airplanes. This electrical failure presents an unsafe condition in airplanes, since it could eventually prevent the APU from shutting down and fire extinguishant from discharging when the flight crew pulls and rotates the fire handle. Consequently, the flightcrew would be unable to extinguish an APU fire. The FAA has determined that this unsafe condition could exist or eventually develop on Model 737 series airplanes, and that revision of the AFM must be mandated to ensure that safety is not degraded. The appropriate vehicle for mandating such action to correct an unsafe condition is the airworthiness directive. However, the FAA has confirmed that Boeing intends to update the AFM for the affected airplanes in the next revision, which is scheduled for December 1995. \n\n\tOne commenter, Boeing, requests that the FAA reevaluate the cost-benefit analysis of the proposed rule. The commenter states that simply changing the AFM to add a recall item, as proposed in this AD, will not fully accomplish the intent of the rule; flightcrews must be retrained to commit the recall item to memory. The commenter states that the cost benefit analysis should account for such training (including flightcrew training time, instructors, and updated materials). The commenter points out that the FAA is required by Executive Order 12866 to do an analysis to show that benefits outweigh costs before imposing new regulations. The commenter adds that, in calculating the total cost impact of the proposed AD, the FAA is stating that industry will be incurring a cost in implementing this rule that it would otherwise not be liable for if the rule was not issued. \n\n\tThe FAA acknowledges the concerns of this commenter. The FAA recognizes that, in accomplishing the requirements of any AD, operators may incur "incidental" costs in addition to the "direct" costs that are reflected in the cost analysis presented in the AD preamble. However, the cost analysis in AD rulemaking actions typically does not include incidental costs. In the case of this AD,for example, the requirements are to revise the AFM to include certain information. How operators actually "implement" that information thereafter (once it is placed in the AFM) may vary greatly among them: for some operators, implementation may necessitate extensive retraining among their flightcrews; for others, implementation may merely be considered a typical part of the routine, continuous training of their flightcrews. In light of this, it would be nearly impossible for the FAA to calculate accurately or to reflect all costs associated with retraining flightcrews, as suggested by the commenter. (The commenter does not provide an estimate of such costs.) \n\n\tFurther, because AD's require specific actions to address specific unsafe conditions, they appear to impose costs that would not otherwise be borne by operators. However, because of the general obligation of operators to maintain and operate aircraft in an airworthy condition, this appearance is deceptive. Attributing those costs solely to the issuance of this AD is unrealistic because, in the interest of maintaining and operating safe aircraft, prudent operators would accomplish the required actions even if they were not required to do so by the AD. In any case, the FAA has determined that direct and incidental costs are still outweighed by the safety benefits of the AD. \n\n\tIn addition, the FAA is not required to do a full cost-benefit analysis for each AD, since an AD typically does not meet the criteria of a "significant regulatory action" under Executive Order 12866. As a matter of law, in order to be airworthy, an aircraft must conform to its type design and be in a condition for safe operation. The type design is approved only after the FAA makes a determination that it complies with all applicable airworthiness requirements. In adopting and maintaining those requirements, the FAA has already made the determination that they establish a level of safety that is cost-beneficial. When the FAA later makes a finding of an unsafe condition in an aircraft and issues an AD, it means that the original cost beneficial level of safety is no longer being achieved and that the required actions are necessary to restore that level of safety. Because this level of safety has already been determined to be cost beneficial, and because the AD does not add an additional regulatory requirement that increases the level of safety beyond what has been established by the type design, a full cost-benefit analysis for each AD would be redundant and unnecessary. \n\n\tAfter careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the change previously described. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD. \n\n\tThere are approximately 2,602 Model 737 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 1,072 airplanes of U.S. registry will be affected by this AD, that it will take approximately 1 work hour per airplane to accomplish the required actions, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $64,320, or $60 per airplane. \n\n\tThe cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. \n\n\tThe regulations adopted herein will not have substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. \n\n\tFor 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 final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."\n\n List of Subjects in 14 CFR Part 39 \n\n\tAir transportation, Aircraft, Aviation safety, Safety. \n\nAdoption of the Amendment \n\n\tAccordingly, 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: \n\nPART 39 - AIRWORTHINESS DIRECTIVES \n\n\t1. The authority citation for part 39 continues to read as follows: Authority: 49 USC 106(g), 40101, 40113, 44701. § 39.13 - (Amended) \n\n\t2. Section 39.13 is amended by adding the following new airworthiness directive: