AD 98-02-05

Discussion On January 9, 1998, the FAA issued priority letter AD 98-02-05, which applies to Cessna Model 172R airplanes (serial numbers 17280001 through 17280305). That AD resulted from a quality control problem with Aeroquip engine exhaust mufflers installed on certain Cessna Model 172R airplanes. Cessna recently notified the FAA that the Aeroquip muffler, part number (P/N) 00624-NH4000011-10 71379 0554011-2, is installed in approximately 250 Cessna Model 172R airplanes. Cessna has determined, through pressure testing, that approximately 5 out of the 25 tested mufflers manufactured by Aeroquip are leaking. These inadequate or failed weldments will permit exhaust gas (including carbon monoxide) leakage from the muffler, and consequently into the airplane s cabin and cockpit area. This condition, if not corrected, could result in passenger and pilot injury with consequent loss of control of the airplane.

The FAA's Determination and Explanation ofthe AD Since an unsafe condition has been identified that is likely to exist or develop in other Cessna Model 172R airplanes of the same type design, the FAA issued priority letter AD 98-02-05 to prevent carbon monoxide gas from entering the airplane s cabin heating system and cabin, which, if not corrected, could result in passenger and pilot injury with consequent loss of control of the airplane.

The AD requires de-activating the cabin heating system, and fabricating and installing a placard within the pilot s clear view, using 1/8-inch letters with the following words: CABIN HEATER INOPERATIVE prior to further flight.

This AD also requires replacing the Aeroquip engine exhaust muffler (P/N 00624-NH4000011-10 71379 0554011-2). If replacement parts are not available, the airplane may continue operation with the heating system de-activated for a period not to exceed 6 calendar months after the effective date of this AD.

Determination of the Effective Date of the ADSince it was found that immediate corrective action was required, notice and opportunity for prior public comment thereon were impracticable and contrary to the public interest, and good cause existed to make the AD effective immediately by individual letters issued on January 9, 1998, to all known U.S. operators of Cessna Model 172R airplanes with serial numbers 17280001 through 17280305. These conditions still exist, and the AD is hereby published in the Federal Register as an amendment to section 39.13 of the Federal Aviation Regulations (14 CFR 39.13) to make it effective as to all persons.

Comments Invited Although this action is in the form of a final rule that involves requirements affecting immediate flight safety and, thus, was not preceded by notice and opportunity to comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications should identifythe Rules Docket number and be submitted in triplicate to the address specified above. All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response tothis rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket No. 98-CE-06-AD." The postcard will be date stamped and returned to the commenter.

Regulatory Impact The 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.

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT RegulatoryPolicies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES".

List of Subjects in 14 CFR Part 39 Air transportation, Aircraft, Aviation safety, Safety.

ADOPTION OF THE AMENDMENT Accordingly, 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:

PART 39 - AIRWORTHINESS DIRECTIVES 1. The authority citation for part 39 continues to read as follows: Authority: 49 USC 106(g), 40113, 44701. 39.13 [Amended] 2. Section 39.13 is amended by adding a new airworthiness directive (AD) to read as follows: