Airworthiness Directives; Boeing Model 747-200B, -200C, -200F, -300, -400, -400D, and -400F Series Airplanes; and Model 747SP Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 747-200B, -200C, -200F, -300, -400, -400D, and -400F series airplanes; and Model 747SP series airplanes. This proposal would require repetitive functional tests of the auxiliary power unit (APU) and engine fire shutoff switches and repetitive replacements of the APU and engine fire shutoff switches. This proposal would also provide an optional terminating action for the repetitive inspections and replacements. This action is necessary to prevent mineral build-up on the APU and engine fire shutoff switches, which could lead to failure of the switches to discharge fire suppressant in the affected area and could result in an uncontrolled fire that could spread to the strut, wing, or aft body of the airplane. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by August 9, 2004.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2002-NM-286-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays. Comments may be submitted via fax to (425) 227-1232. Comments may also be sent via the Internet using the following address: 9-anm-nprmcomment@faa.gov. Comments sent via fax or the Internet must contain “Docket No. 2002-NM-286-AD” in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 or 2000 or ASCII text.

The service information referenced in the proposed rule may be obtained from Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

Sulmo Mariano, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6501; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the proposed rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this action may be changed in light of the comments received.

Submit comments using the following format:

• Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
• For each issue, state what specific change to the proposed AD is being requested.
• Include justification (e.g., reasons or data) for each request.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2002-NM-286-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2002-NM-286-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received reports indicating that, during a routine maintenance check, several squib circuits failed when the engine fire extinguishing system test was performed on certain Boeing Model 747 series airplanes. One of the reports indicated that the fire handle switches failed to provide current to several squibs because of internal continuity failures. An investigation revealed that Lucas humidifiers distribute air containing minerals from the potable water supply. The humidified air contaminates the auxiliary power unit (APU) and engine fire shutoff switches. This condition, if not corrected, could result in mineral build-up on the APU and engine fire shutoff switches, which could lead to failure of the switches to discharge fire suppressant in the affected area and could result in an uncontrolled fire that could spread to the strut, wing, or aft body of the airplane.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin 747-26A2274, Revision 1, dated January 9, 2003, which describes the following procedures:

1. Performing repetitive functional tests of the APU and engine fire shutoff switches;

2. Performing repetitive replacements of the APU and engine fire shutoff switches with new or serviceable switches; and

3. Deactivation of the Lucas (also known as TRW Systemes Aeronautiques) flight deck humidifier, part numbers (P/N) M01AA0101, M01AB0101, M01AB0102, or M01AB0103, which would eliminate the need for the repetitive functional tests and replacements.

Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition.

Explanation of Requirements of Proposed Rule

Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, the proposed AD would require accomplishment of the actions specified in the service bulletin described previously, except as described below.

Difference Between Service Bulletin and Proposed Rule

Operators should note that the service bulletin specifies one of the initial compliance times as “after the airplane has 12 calendar months of service but within 18 calendar months since airplane delivery * * *.” However, this proposed AD specifies the one initial compliance time as “within 18 months since the date of issuance of the original Airworthiness Certificate or the original Export Certificate of Airworthiness.” This decision is based on our determination that “since airplane delivery” may be interpreted differently by different operators. We find that our proposed terminology is generally understood within the industry and records will always exist that establish these dates with certainty. We also did not include reference to “after the airplane has 12 calendar months of service” because accomplishing the initial actions within 18 months of service would provide an acceptable level of safety. Thus our proposed compliance time would include any airplanes that may have been operating since delivery.

Although the service bulletin recommends accomplishing the initial replacement at “18 calendar months from issue date of the service bulletin,” this proposed AD requires accomplishing the replacement “within 36 months after the effective date of this AD.” We find that a compliance time of “within 36 months after the effective date of this AD” represents an appropriate interval of time to address the identified unsafe condition and allows affected airplanes to continue to operate during that interval without compromising safety.

Also, operators should note that the service bulletin states that “Operators who perform the 90 calendar day inspection and the 18 calendar month cleaning can avoid the required test interval shown in Figure 1, by deactivation of the Lucas Flight Deck Humidifier.” However, this proposed AD specifies that if the optional deactivation of the humidifier is accomplished, operators are required to replace the switches with new or serviceable switches before further flight following the deactivation. If a flight deck humidifier is deactivated shortly before a required replacement or a required functional test, it may be possible that any one of the switches could have a latent type of failure. To address this unsafe condition, we have added the requirement to replace all switches before further flight following deactivation of the humidifier, as stated in paragraph (e) of this proposed AD. We have also added requirements as stated in paragraph (f) of this proposed AD to ensure functional tests and replacements of switches are accomplished for operators that reactivate the Lucas humidifier.

We have coordinated these changes with the manufacturer.

Cost Impact

There are approximately 316 airplanes of the affected design in the worldwide fleet. We estimate that 50 airplanes of U.S. registry would be affected by this proposed AD, and that the average labor rate is $65 per work hour. Table 1 provides the estimated costs for U.S. operators to comply with this proposed AD.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this proposed AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions.

Regulatory Impact

The regulations proposed herein would 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 proposal would not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that this proposed regulation (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) if promulgated, 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 draft regulatory 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
• Safety

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 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.