[Federal Register Volume 59, Number 21 (Tuesday, February 1, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-584]


[[Page Unknown]]

[Federal Register: February 1, 1994]


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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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