Airworthiness Directives; Boeing Model 747-400, 777-200, and 777-300 Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Supplemental notice of proposed rulemaking; reopening of comment period.

SUMMARY:

This document revises an earlier proposed airworthiness directive (AD), applicable to Boeing Model 747-400, 777-200, and 777-300 series airplanes, that would have required an inspection of the flight deck humidifier to determine certain part numbers. That proposed AD also would have required, for certain airplanes, replacing the cell stack of the flight deck humidifier with a supplier-tested cell stack, or replacing the cell stack with a blanking plate and subsequently deactivating the flight deck humidifier, if necessary. For other airplanes, that proposed AD would have required replacing the cell stack with a supplier-tested cell stack, or replacing the cell stack with a blanking plate and subsequently deactivating the humidifier system, if necessary. The proposed AD also would have allowed blanking plates to be replaced with cell stacks. This new action revises the proposed rule by adding airplanes to the applicability, requiring an inspection of the flight deck humidifier to determine certain part numbers on certain airplanes, and requiring replacement of the cell stack on certain other airplanes. The actions specified by this new proposed AD are intended to prevent an increased pressure drop across the humidifier and consequent reduced airflow to the flight deck, which could result in the inability to clear any smoke that might appear in the flight deck. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by January 30, 2006.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-360-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. 2000-NM-360-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:

Jeffrey S. Palmer, Aerospace Engineer, Cabin Safety and Environmental Systems Branch, ANM-150S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6481; 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 2000-NM-360-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. 2000-NM-360-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to add an airworthiness directive (AD), applicable to Boeing Model 747-400, 777-200, and 777-300 series airplanes, equipped with a Hamilton Sundstrand flight deck humidifier, was published as a supplemental notice of proposed rulemaking (referred to hereafter as the first SNPRM) in the Federal Register on January 6, 2005 (70 FR 1211).

The first SNPRM would have required an inspection of the flight deck humidifier to determine certain part numbers. The first SNPRM also would have required, for certain airplanes, replacing the cell stack of the flight deck humidifier with a supplier-tested cell stack, or replacing the cell stack with an end plate and subsequent deactivation of the flight deck humidifier, if necessary. For other airplanes, the first SNPRM would have required replacing the cell stack with a supplier-tested cell stack, or replacing the cell stack with a blanking plate and subsequent deactivation of the humidifier system, if necessary. The first SNPRM also would have allowed end plates or blanking plates to be replaced with cell stacks.

The first SNPRM was prompted by reports of sagging cell stack membranes of the flight deck humidifiers. That condition, if not corrected, could result in an increased pressure drop across the humidifier and consequent reduced airflow to the flight deck, which could result in the inability to clear any smoke that might appear in the flight deck.

Actions Since Issuance of First SNPRM

Since the issuance of the first SNPRM, Boeing has issued Boeing Alert Service Bulletin 747-21A2414, Revision 2, dated July 7, 2005 (Revision 1, dated October 26, 2000, was referenced as an applicable source of service information for doing the actions in that SNPRM); and Boeing Alert Service Bulletin 777-21A0048, Revision 2, dated July 14, 2005 (Revision 1, dated September 7, 2000, was referenced as an applicable source of service information for doing the actions in the first SNPRM). Revision 2 of the alert service bulletins contains essentially the same procedures for the replacement of certain cell stacks of the flight deck humidifier. However, Revision 2 of the alert service bulletins adds airplanes to the effectivity. For those airplanes, Revision 2 of the alert service bulletin adds a procedure to inspect for a certain flight deck humidifier and inspect for a certain cell stack if necessary. Revision 2 of the alert service bulletins also specifies on which airplanes the replacement should be accomplished.

We have made the following changes to the first SNPRM:

• We have revised the applicability of this second SNPRM to reference Revision 2 of the alert service bulletins.
• We have referenced Revision 2 of the alert service bulletins as the appropriate source of service information for accomplishing the cell stack replacements.
• We have also revised the format of this second SNPRM to clarify that a new or supplier-tested cell stack may be installed on flight deck humidifiers that have a blanking plate; paragraphs (a) and (d) of this second SNPRM (cited as paragraphs (b) and (e) of the first SNPRM) include the information on blanking plate replacement that was specified in paragraphs (b)(3) and (e)(3) of the first SNPRM. In addition, for the blanking plate replacement specified in paragraph (a) of this second SNPRM, we specify that the replacement be done in accordance with Hamilton Sundstrand Service Bulletin 821486-21-01, dated March 15, 2000, and that if the flight deck humidifier is activated after the replacement, the humidifier must be activated in accordance with Boeing Service Bulletin 747-21-2405, Revision 4, dated July 29, 1999.
• We have revised the format of this second SNPRM to require that certain airplanes do the inspections for part numbers and then replace the cell stack if necessary and that certain other airplanes replace the cell stack. Revision 2 of the alert service bulletins specifies on which airplanes (identified according to groups in the alert service bulletins) to do the inspection and then the replacement if necessary, and on which airplanes to do the replacement.
• We have revised the cost estimate of this second SNPRM.

Comments

We have also given due consideration to the comments received in response to the first SNPRM.

Request To Revise Number of Affected Airplanes

One commenter, the manufacturer, requests that the number of airplanes that could be fitted with the potentially defective cell stack be revised from 114 airplanes, as stated in the “Request to Withdraw the Proposed AD” section of the first SNPRM, to 176 airplanes. The commenter states that 176 humidifiers have been delivered that could have the potentially defective cell stacks.

We agree with the commenter that the total number of airplanes that could be fitted with the potentially defective cell stack is 176. We have revised the number in the Cost Impact section of this second SNPRM.

Request To Allow Additional Records Review

The same commenter requests that we add an additional records review to allow operators to show compliance with the intent of the first SNPRM. The commenter states that if an airplane or retrofit kit was delivered after December 16, 1999, and the record review shows that the humidifier or cell stack was not replaced since, no inspection or replacement of the humidifier is needed. The commenter notes that December 16, 1999 is the delivery date of the first airplane that was delivered with an acceptable cell stack that was screened in production. The commenter contends that all humidifier deliveries would thereafter contain a cell stack that is not susceptible to the unsafe condition.

We partially agree with the commenter. We acknowledge that airplanes delivered after December 16, 1999, would not require that the humidifier be inspected or replaced if there has not been any maintenance on the humidifier and the appropriate part markings could be determined. However, we have not revised the requirements for the records review specified in the first SNPRM since this review would include airplanes delivered with a known good cell stack. As specified in paragraphs (c) and (f) of this second SNPRM, a records review would be allowed in lieu of the inspection.

Request To Revise Nomenclature

The same commenter requests that the term “end plate” in the first SNPRM be revised to “blanking plate.” The commenter states that an end plate is actually a part that exists in the cell stack assembly, while a blanking plate is a part that can be installed in lieu of the cell stack. The commenter recommends that the first SNPRM describe part number (P/N) 1001157-1 as a blanking plate.

We agree with the commenter. Where the first SNPRM specifies an end plate, we have revised this second SNPRM to specify a blanking plate.

Clarification of P/Ns

Boeing Alert Service Bulletin 747-21A2414, Revision 2, dated July 7, 2005, specifies the cell stack P/N as 103111-2 in paragraph 3. of “Group 2-3: Part 3—Cell Stack Part Number Inspection” of the Accomplishment Instructions of the service bulletin. The correct P/N is 1003111-2.

Boeing Alert Service Bulletin 777-21A0048, Revision 2, dated July 14, 2005, specifies the cell stack P/N as 10311-1 in paragraph 2.C. of “Parts Necessary For Each Airplane” and 2.D. of “Parts Necessary to Change Spares” of the service bulletin. The correct P/N is 1003111-1.

Explanation of Change Made to This AD

We have revised paragraph (d)(1) of this second SNPRM to clarify the delegation authority for Authorized Representatives for the Boeing Commercial Airplanes Delegation Option Authorization.

Clarification of Alternative Method of Compliance (AMOC) Paragraph

We have revised this second SNPRM to clarify the appropriate procedure for notifying the principal inspector before using any approved AMOC on any airplane to which the AMOC applies.

Conclusion

Since this change expands the scope of this second SNPRM, the FAA has determined that it is necessary to reopen the comment period to provide additional opportunity for public comment.

Cost Impact

There are approximately 176 airplanes of the affected design in the worldwide fleet. The FAA estimates that 29 airplanes of U.S. registry would be affected by this second SNPRM. The cost per airplane would range between $390 and $6,248 per airplane, depending on the actions chosen by the operator. The fleet cost estimate would not exceed $181,192.

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 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.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in subtitle VII, part A, subpart III, section 44701, “General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

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.