Airworthiness Directives; Boeing Model 747 Series Airplanes With Stretched Upper Decks (SUD)

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 93-NM-138-AD; Amendment 39-8797; AD 94-01-15]

Airworthiness Directives; Boeing Model 747 Series Airplanes With

Stretched Upper Decks (SUD)

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 series airplanes, that requires

installation of an aluminum seal retainer on the bulb seal attached to

the fascia panels of the escape systems on the SUD. This amendment is

prompted by a report that, during deployment of an emergency evacuation

slide, the slide inflated but subsequently lost air from one chamber.

The actions specified by this AD are intended to prevent the bulb seal

from coming off the fascia panels and being ingested into the turbofans

of the escape systems on the stretched upper deck (SUD), which could

impede the inflation of the escape slide during an emergency situation.

DATES: Effective March 3, 1994.

The incorporation by reference of certain publications listed in

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

of March 3, 1994.

ADDRESSES: The service information referenced in this AD may be

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

Washington 98124. 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: Jayson Claar, Aerospace Engineer,

Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle

Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,

Washington 98055-4056; telephone (206) 227-2784; 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 Boeing Model 747 series airplanes with stretched upper

decks (SUD) was published in the Federal Register on September 21, 1993

(58 FR 48983). That action proposed to require installation of an

aluminum seal retainer on the bulb seal attached to the fascia panels

of the escape systems on the SUD.

Interested persons have been afforded an opportunity to participate

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

the comments received.

Three commenters support the proposal.

One commenter considers that the proposed rule is not warranted

since there has been only one reported incident where the bulb seal was

ingested into the turbofan. The commenter states that, even during that

incident, the damage was limited to one of the escape slide's chambers

and the slide was still usable. The FAA does not concur with the

suggestion that this AD action is not warranted. While the commenter is

correct in noting that there has been only a single reported case of

ingestion of the bulb seal into the turbofans, the potential still

exists for a bulb seal to break away if there is no component to retain

it. The consequences of the bulb seal breaking away and being ingested

into the turbofan can ultimately impede the inflation of the escape

slide, which creates a potential unsafe condition by rendering the

slide unusable in the event of an emergency evacuation. Although the

commenter indicates that the incident slide was still usable after

being damaged, the FAA has determined that the potential exists for

similar or greater damage to occur on any of the subject escape slides,

as long as there is the possibility that the bulb seal can be ingested

into the turbofans. Installation of the bulb seal retainer, as required

by this AD, will positively address this potential unsafe condition by

preventing the separation of the bulb seal from the fascia panel.

This same commenter requests that one airplane be deleted from the

applicability of the AD. The airplane having line number 981 was

modified with the bulb seal retainer prior to delivery; therefore, the

unsafe condition does not exist with regard to this specific airplane.

The FAA concurs and has revised the applicability of the final rule

accordingly. Additionally, the economic impact information, below, has

been revised to indicate the deletion of this airplane from those

affected by the AD requirements.

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 290 Model 747 series airplanes of the

affected design in the worldwide fleet. The FAA estimates that 29

airplanes of U.S. registry will be affected by this AD, that it will

take approximately 4 work hours per airplane to accomplish the required

actions, and that the average labor rate is $55 per work hour. The cost

of required parts would be nominal. Based on these figures, the total

cost impact of the AD on U.S. operators is estimated to be $6,380, or

$220 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:

94-01-15 Boeing: Amendment 39-8797. Docket 93-NM-138-AD.

Applicability: Model 747 series airplanes with a stretched upper

deck, all line numbers up to and including line number 980;

certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent the bulb seal from coming off the fascia panels and

being ingested into the turbofans of the escape systems on the

stretched upper deck (SUD), which could impede the inflation of the

escape slide during an emergency situation, accomplish the

following:

(a) Within 6 months after the effective date of this AD, install

an aluminum seal retainer on the bulb seal attached to the fascia

panel of the escape systems on the SUD, in accordance with Boeing

Alert Service Bulletin 747-25A3056, dated July 12, 1993.

(b) 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). 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.

(c) 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.

(d) The installation shall be done in accordance with Boeing

Alert Service Bulletin 747-25A3056, dated July 12, 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. Copies may be inspected at

the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW.,

Renton, Washington; at the Office of the Federal Register, 800 North

Capitol Street, NW., suite 700, Washington, DC.

(e) This amendment becomes effective on March 3, 1994.

Issued in Renton, Washington, on January 5, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-584 Filed 1-31-94; 8:45 am]

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