E7-24521. Airworthiness Directives; Boeing Model 737-300, -400, and -500 Series Airplanes

AGENCY:

Federal Aviation Administration (FAA), Department of Transportation (DOT).

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for certain Model 737-300, -400, and -500 series airplanes. This proposed AD would require an inspection to determine the manufacturer and manufacture date of the oxygen masks in the passenger service unit and the lavatory and attendant box assemblies, corrective action if necessary, and other specified action. This proposed AD results from a report that several passenger masks with broken in-line flow indicators were found following a mask deployment. We are proposing this AD to prevent the in-line flow indicators of the passenger oxygen masks from fracturing and separating, which could inhibit oxygen flow to the masks and consequently result in exposure of the passengers and cabin attendants to hypoxia following a depressurization event.

DATES:

We must receive comments on this proposed AD by February 4, 2008.

ADDRESSES:

You may send comments by any of the following methods:

• Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
• Fax: [phone].
• Mail: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.
• Hand Delivery: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

For service information identified in this AD, contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207.

Examining the AD Docket

You may examine the AD docket on the Internet at http://www.regulations.gov;​; or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this proposed AD, the regulatory evaluation, any comments received, and other information. The street address for the Docket Office (telephone [phone]) is in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT:

Susan Letcher, Aerospace Engineer, Cabin Safety and Environmental Systems Branch, ANM-150S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send any written relevant data, views, or arguments about this proposed AD. Send your comments to an address listed under the ADDRESSES section. Include “Docket No. FAA-2007-0346; Directorate Identifier 2007-NM-202-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this proposed AD. We will consider all comments received by the closing date and may amend this proposed AD because of those comments.

We will post all comments we receive, without change, to http://www.regulations.gov,, including any personal information you provide. We will also post a report summarizing each substantive verbal contact we receive about this proposed AD.

Discussion

We have received a report indicating that several passenger masks with broken in-line flow indicators were found following a mask deployment, on a Boeing Model 777-200 series airplane. Operators subsequently found several more broken in-line flow indicators after examining the oxygen mask assemblies on other Model 777 series airplanes and on Model 747-400 series airplanes. Investigation revealed that certain flow indicators are weaker and can fracture because of internal residual stresses caused by the flow indicator joint design and manufacturing processes. Fractures cause the in-line flow indicator to separate and consequently prevent oxygen flow to the mask during an emergency. This condition, if not corrected, could result in exposure of the passengers and cabin attendants to hypoxia following a depressurization event.

The oxygen masks on certain Model 777 airplanes and Model 747-400 series airplanes have the same flow indicators as those installed on certain Model 737-300, -400, and -500 series airplanes. Therefore, the Model 737-300, -400, and -500 series airplanes may be subject to the identified unsafe condition.

Relevant Service Information

We have reviewed Boeing Special Attention Service Bulletin 737-35-1099, dated April 9, 2007. The service bulletin describes procedures for doing a general visual inspection to determine the manufacturer and manufacture date of the oxygen masks in the passenger service unit (PSU) and the lavatory and attendant box assemblies. The service bulletin also describes procedures for doing the corrective action if necessary and other specified action. The corrective action includes repairing any B/E Aerospace oxygen mask assembly with a manufacturing date after January 1, 2002, and before March 1, 2006. The service bulletin also specifies that as an alternative to doing the repair (rework), the oxygen mask assembly may be replaced with a new oxygen mask outside the scope of the service bulletin. The other specified action includes doing the oxygen mask drop test.

Boeing Special Attention Service Bulletin 737-35-1099 refers to B/E Aerospace Service Bulletin 174080-35-01, dated February 6, 2006; and Revision 1, dated May 1, 2006; as additional sources of service information for repairing the oxygen mask assembly. B/E Aerospace Service Bulletin 174080-35-01 describes procedures for modifying the oxygen mask assembly by replacing the flow indicator, part number (P/N) 118023-02, with an improved flow indicator, P/N 118023-12. B/E Aerospace Service Bulletin 174080-35-01 also specifies that, as an alternative to modifying the oxygen mask, operators may replace the oxygen mask with a new oxygen mask having the improved flow indicator.

Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition.

FAA's Determination and Requirements of the Proposed AD

We have evaluated all pertinent information and identified an unsafe condition that is likely to exist or develop on other airplanes of this same type design. For this reason, we are proposing this AD, which would require accomplishing the actions specified in the service information described previously.

Clarification Between the Proposed AD and Service Bulletin

Although Boeing Special Attention Service Bulletin 737-35-1099 specifies to repair the oxygen mask assembly, the intent of the service bulletin is to replace it with either a new or modified oxygen mask assembly having an improved flow indicator. Therefore, this proposed AD would require replacing the oxygen mask assembly with a new or modified oxygen mask assembly having an improved flow indicator.

Costs of Compliance

There are about 1,956 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 646 airplanes of U.S. registry. The proposed actions would take about 16 work hours per airplane, for an average of 180 oxygen masks per airplane distributed in about 45 PSU/oxygen boxes, at an average labor rate of $80 per work hour. Required parts would cost about $6 per oxygen mask, or $1,080 per airplane. Based on these figures, the estimated cost of the proposed AD for U.S. operators is $1,524,560, or $2,360 per airplane.

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 Findings

We have determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD 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.

For the reasons discussed above, I certify that the 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. 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.

We prepared a regulatory evaluation of the estimated costs to comply with this proposed AD and placed it in the AD docket. See the ADDRESSES section for a location to examine the regulatory evaluation.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 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.

§ 39.13

[Amended]

2. The Federal Aviation Administration (FAA) amends § 39.13 by adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2007-0346; Directorate Identifier 2007-NM-202-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by February 4, 2008.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Boeing Model 737-300, -400, and -500 series airplanes, certificated in any category; as identified in Boeing Special Attention Service Bulletin 737-35-1099, dated April 9, 2007.

Unsafe Condition

(d) This AD results from a report that several passenger masks with broken in-line flow indicators were found following a mask deployment. We are issuing this AD to prevent the in-line flow indicators of the passenger oxygen masks from fracturing and separating, which could inhibit oxygen flow to the masks and consequently result in exposure of the passengers and cabin attendants to hypoxia following a depressurization event.

Compliance

(e) You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.

Inspection and Related Investigative/Corrective Actions if Necessary

(f) Within 60 months after the effective date of this AD, do a general visual inspection to determine the manufacturer and manufacture date of the oxygen masks in the passenger service unit and the lavatory and attendant box assemblies, and do the applicable corrective action and other specified action, by accomplishing all of the applicable actions specified in the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-35-1099, dated April 9, 2007; except where the service bulletin specifies repairing the oxygen mask assembly, replace it with a new or modified oxygen mask assembly having an improved flow indicator. The corrective action and other specified action must be done before further flight.

Note 1:

Boeing Special Attention Service Bulletin 737-35-1099 refers to B/E Aerospace Service Bulletin 174080-35-01, dated February 6, 2006; and Revision 1, dated May 1, 2006; as additional sources of service information for modifying the oxygen mask assembly by replacing the flow indicator with an improved flow indicator.

Alternative Methods of Compliance (AMOCs)

(g)(1) The Manager, Seattle Aircraft Certification Office, FAA, has the authority to approve AMOCs for this AD, if requested in accordance with the procedures found in 14 CFR 39.19.

(2) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Before using any approved AMOC on any airplane to which the AMOC applies, notify your appropriate principal inspector (PI) in the FAA Flight Standards District Office (FSDO), or lacking a PI, your local FSDO.

Issued in Renton, Washington, on December 10, 2007.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.