Airworthiness Directives; Boeing Model 747-200B, -200C, -300, - 400, and -400D Series Airplanes Equipped With Passenger Oxygen System Reservoir Mask Assemblies, Boeing Part Numbers 10-60137-152 through - 165

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 93-NM-128-AD; Amendment 39-8812; AD 94-03-05]

Airworthiness Directives; Boeing Model 747-200B, -200C, -300, -

400, and -400D Series Airplanes Equipped With Passenger Oxygen System

Reservoir Mask Assemblies, Boeing Part Numbers 10-60137-152 through -

165

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD),

applicable to certain Boeing Model 747-200B, -200C, -300, -400, and

400D series airplanes, that requires a revision to the FAA-approved

maintenance program to require unrestricted opening of the passenger

service unit (PSU) door during functional testing of the passenger

oxygen system; and requires an inspection to detect leaks in certain

passenger oxygen system reservoir bags, and marking and replacement of

damaged mask assemblies. This amendment is prompted by reports that the

passenger oxygen mask reservoir bags became overpressurized and split

at the seams, resulting in failure of the bags. The actions specified

by this AD are intended to ensure the delivery of emergency oxygen

through the passenger oxygen system reservoir mask assemblies.

DATES: Effective March 14, 1994.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of March 14, 1994.

ADDRESSES: The service information referenced in this AD may be

obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle,

Washington 98124-2207. This information may be examined at the Federal

Aviation Administration (FAA), Transport Airplane Directorate, Rules

Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of

the Federal Register, 800 North Capitol Street, NW., suite 700,

Washington, DC.

FOR FURTHER INFORMATION CONTACT: Kathi Ishimaru, Aerospace Engineer,

Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane

Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue,

SW., Renton, Washington 98055-4056; telephone (206) 227-2674; fax (206)

227-1181.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal

Aviation Regulations to include an airworthiness directive (AD) that is

applicable to certain Boeing Model 747-200B, -200C, -300, -400, and -

400D series airplanes was published in the Federal Register on August

23, 1993 (58 FR 44468). That action proposed to revise the FAA-approved

maintenance program to require unrestricted opening of the passenger

service unit (PSU) door during functional testing of the passenger

oxygen system; and to require an inspection to detect leaks in certain

passenger oxygen system reservoir bags, and marking and replacement of

damaged mask assemblies.

Interested persons have been afforded an opportunity to participate

in the making of this amendment. Due consideration has been given to

the comments received. -

Two commenters support the proposed rule.

One commenter notes that an unsafe condition does not exist since

its airplanes are equipped with approximately 20 percent more oxygen

masks than the maximum number of passengers, and the projected failure

rate for these masks is estimated to be only 10 to 15 percent. From

this comment, the FAA infers that the commenter is requesting that the

rule be withdrawn. The FAA does not concur. Although the projected

failure rate is lower than the number of available masks, the FAA has

determined that passengers using defective masks may not realize that

the masks are supplying an insufficient quantity of oxygen; and thus,

passengers would not seek out spare oxygen masks. Therefore, the

potential would still exist for passengers to be unable to obtain

unrestricted delivery of emergency oxygen through the passenger oxygen

system reservoir mask assembly. This AD action addresses that potential

unsafe condition.

Boeing Commercial Airplane Group requests that the applicability of

the proposal be revised to exclude airplanes that were delivered prior

to August 1991. Boeing indicates that data have demonstrated that the

masks installed on those airplanes have had significantly fewer leaks/

failures than masks installed on airplanes that were delivered after

August 1991; therefore, those earlier airplanes would not necessarily

be subject to the same unsafe condition addressed by the proposed AD

action. The FAA does not concur with the commenter's request to exclude

certain airplanes from the applicability. The FAA has reviewed the new

data concerning the failure rate of the subject masks, which indicate

that the masks' failure rate is lower than previously anticipated.

While the data do demonstrate that airplanes delivered prior to August

1991 have had significantly fewer leaking masks that fail to provide

oxygen at or above FAA-required levels than those airplanes delivered

in August 1991 and later, the FAA does not consider that this lower

failure rate warrants the exclusion of any airplanes from the

requirements of the rule. However, in light of the lower than

originally anticipated failure rates for all of these masks, coupled

with the unlikely event of decompression of the airplane, the FAA has

reconsidered the proposed compliance time for inspection and

replacement of the masks, and has determined that the compliance time

can be extended for all airplanes without adversely affecting safety.

Accordingly, the final rule has been revised to require a 15-month

compliance time for Model 747-200B, -200C, and -300 series airplanes

(the earlier-delivered airplanes), and a 180-day compliance time for

Model 747-400 and -400D series airplanes.

Several other commenters request that the proposed compliance time

of 45 days to inspect and replace the masks be extended for a variety

of reasons: Two of these commenters request that the proposed

compliance time be revised to coincide with operators' regularly

scheduled maintenance periods. One of these commenters suggests an

alternative compliance time of ``the next 3C check'' for Model 747-200

series airplanes, and ``the next 2C check'' for Model 747-400 series

airplanes. One of these commenters did not offer an alternative

suggestion to the proposed compliance time; however, the commenter

asserts that the supplier of these replacement oxygen masks cannot

deliver an adequate quantity of original or modified oxygen masks

within the proposed compliance time, therefore an extension is

necessary. Another commenter requests that the proposed compliance time

be revised to coincide with the time at which a newly-designed mask is

anticipated to become available. As discussed above, the FAA has

extended the compliance time for the required actions, although not for

the reasons requested by these commenters. The extended compliance

time, however, should be sufficient to allow the inspection and

replacement actions to be accomplished during normally scheduled

maintenance, and to allow for any anticipated new mask design to become

available.

Several commenters request that the proposal be revised to include

an option to replace the currently installed passenger oxygen masks

with improved oxygen masks. These commenters request that installation

of these improved oxygen masks eliminate the need to perform a one-time

visual inspection to detect leaks in the passenger oxygen system

reservoir bags. The FAA does not concur. The FAA acknowledges that

Boeing is currently developing new passenger oxygen masks; however,

those masks are not yet available. The FAA considers that delaying this

action until the masks are available would be inappropriate. Since an

unsafe condition exists, the FAA finds that defective masks must be

replaced to ensure continued safety. Therefore, when the improved masks

are developed, approved, and available, affected operators may request

approval to install these improved masks as an alternative method of

compliance, under the provisions of paragraph (e) of the final rule. -

Two commenters note that the cost estimate presented in the

preamble to the Notice was too low and did not take into account the

time to clean, sanitize, repack, and stow the passenger oxygen masks

following the proposed inspection. The commenters state that the

required inspection, and the consequent cleaning, sanitizing,

repacking, and stowing of the oxygen masks would necessitate

approximately 90 work hours. After considering the data presented by

commenters, the FAA concurs that the number of work hours required to

accomplish the required actions is higher than previously approximated;

the economic impact information, below, has been revised to indicate

this higher amount. The economic analysis, however, is limited only to

the cost of actions actually required by the rule. It does not consider

the costs of ``on condition'' actions, e.g., ``repair, if necessary,''

since those actions would be required to be accomplished, regardless of

AD direction, in order to correct an unsafe condition identified in an

airplane and to ensure operation of that airplane in an airworthy

condition, as required by the Federal Aviation Regulations.

After 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 changes previously

described. The FAA has determined that these changes will neither

increase the economic burden on any operator nor increase the scope of

the AD.

There are approximately 160 Boeing Model 747-200B, -200C, -300, -

400, and -400D series airplanes of the affected design in the worldwide

fleet. The FAA estimates that 25 airplanes of U.S. registry will be

affected by this AD, that it will take approximately 90 work hours per

airplane to accomplish the required actions, and that the average labor

rate is $55 per work hour. Based on these figures, the total cost

impact of the AD on U.S. operators is estimated to be $123,750, or

$4,950 per airplane. This total cost figure assumes that no operator

has yet accomplished the requirements of this AD.

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.

For 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.''

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by

reference, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration amends 14 CFR part

39 of the Federal Aviation Regulations as follows:

PART 39--AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C.

106(g); and 14 CFR 11.89.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

94-03-05 Boeing: Amendment 39-8812. Docket 93-NM-128-AD.

Applicability: Model 747-200B, -200C, -300, -400, and -400D

series airplanes equipped with passenger oxygen system reservoir

mask assemblies, having Boeing part numbers 10-60137-152 through -

165 inclusive; certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To ensure the delivery of emergency oxygen through the passenger

oxygen system reservoir mask assemblies, accomplish the following:

(a) For all airplanes: Within 45 days after the effective date

of this AD, revise the FAA-approved maintenance program to require

unrestricted opening of the passenger service unit (PSU) door during

functional testing of the passenger oxygen system.

(b) After accomplishing the requirements of paragraph (a) of

this AD, perform a one-time visual inspection to detect leaks in the

passenger oxygen system reservoir bags, in accordance with Boeing

Telex M-7240-93-1411, dated July 20, 1993, at the time specified in

either paragraph (b)(1) or (b)(2) of this AD, as applicable.

(1) For Model 747-200B, -200C, and -300 series airplanes listed

in Boeing Telex M-7240-93-1411, dated July 20, 1993: Within 15

months after the effective date of this AD.

(2) For Model 747-400 and 747-400D series airplanes listed in

Boeing Telex M-7240-93-1411, dated July 20, 1993: Within 180 days

after the effective date of this AD.

(c) If the masks inflate properly during the inspection required

by paragraph (b) of this AD: No further action is required by this

AD.

(d) If any mask does not inflate properly during the inspection

required by paragraph (b) of this AD: Prior to further flight, mark

the mask assembly and replace it with a new or serviceable mask

assembly, in accordance with Boeing Telex M-7240-93-1411, dated July

20, 1993.

(e) An alternative method of compliance or adjustment of the

compliance time that provides an acceptable level of safety may be

used if approved by the Manager, Seattle Aircraft Certification

Office (ACO), FAA, Transport Airplane Directorate. Operators shall

submit their requests through an appropriate FAA Principal

Maintenance Inspector, who may add comments and then send it to the

Manager, Seattle ACO.

Note: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the Seattle ACO.

(f) Special flight permits may be issued in accordance with FAR

21.197 and 21.199 to operate the airplane to a location where the

requirements of this AD can be accomplished.

(g) The inspection, marking, and replacement shall be done in

accordance with Boeing Telex M-7240-93-1411, dated July 20, 1993.

This incorporation by reference was approved by the Director of the

Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part

51. Copies may be obtained from Boeing Commercial Airplane Group,

P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be

inspected at the FAA, Transport Airplane Directorate, 1601 Lind

Avenue, SW., Renton, Washington; or at the Office of the Federal

Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(h) This amendment becomes effective on March 14, 1994.

Issued in Renton, Washington, on January 26, 1994.

James V. Devany,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-2182 Filed 2-10-94; 8:45 am]

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