[Federal Register Volume 61, Number 84 (Tuesday, April 30, 1996)]
[Proposed Rules]
[Pages 18997-18999]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-10622]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-NM-36-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100 and -200 Series 
Airplanes, and Model 747-100, -200, -300, and -SP Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Boeing Model 737 and 747 
series airplanes. This proposal would require replacement of Waterman 
hydraulic fuse assemblies with modified assemblies. This proposal is 
prompted by reports of failure of hydraulic system A and the standby 
system due to corrosion on the magnesium piston of the hydraulic fuse 
and consequent failure of the fuse to close sufficiently to prevent the 
loss of hydraulic fluid from the system. The actions specified by the 
proposed AD are intended to prevent such failure of the fuse, which 
could result in the failure of one or more hydraulic systems and 
resultant reduced controllability of the airplane.

DATES: Comments must be received by June 10, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 96-NM-

[[Page 18998]]

36-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments 
may be inspected at this location between 9:00 a.m. and 3:00 p.m., 
Monday through Friday, except Federal holidays.
    The service information referenced in the proposed rule may be 
obtained from Boeing Commercial Airplane Group, 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: Kenneth W. Frey, Aerospace Engineer, 
Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft 
Certification Office, 1601 Lind Avenue, SW., Renton, Washington; 
telephone (206) 227-2673; fax (206) 227-1181.

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 notice may be changed in 
light of the comments received.
    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 notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 96-NM-36-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-103, Attention: Rules 
Docket No. 96-NM-36-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA received two reports indicating that the hydraulic system A 
and the standby hydraulic system have failed on Model 737 series 
airplanes during flight. During subsequent emergency landings, these 
airplanes departed the end of the runway and sustained severe damage. 
On one of these airplanes, both actuator attach lugs on the support 
fittings of the No. 1 Krueger flap actuator were severed completely. 
The actuator separated from the front spar, and the adjacent hydraulic 
lines were severed. On another airplane, the No. 3 Krueger flap 
actuator separated from the fitting, and the hydraulic lines to the 
actuator were severed. Subsequently, the hydraulic fuse did not close 
sufficiently to prevent the loss of hydraulic fluid from the system. 
Results of a laboratory examination of the fuse indicated that 
corrosion existed on the magnesium piston of the fuse, which 
contributed to the failure of the fuse. Failure of the hydraulic fuse, 
if not corrected, could result in the failure of one or more hydraulic 
systems and, consequently, could result in reduced controllability of 
the airplane.
    Hydraulic fuses are installed to prevent failure of the hydraulic 
system in the event of breakage of the hydraulic lines to leading edge 
devices such as the actuators. These fuses also preserve the flight 
control systems following a major failure such as an uncontained engine 
failure, and minimize the fire hazard in the event of a hydraulic line 
failure in the brake system. The FAA has determined that hydraulic 
fuses having magnesium pistons are installed on Model 737-100 and -200 
series airplanes as well as Model 747-100, -200, -300, and -SP series 
airplanes. Therefore, the FAA finds that all of these airplane models 
are subject to the unsafe condition identified in this proposal.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Letter 737-SL-29-
21, dated December 16, 1982 (for Model 737 series airplanes). This 
service letter describes procedures for replacement of the existing 
Waterman hydraulic fuse assemblies with modified assemblies having 
pistons made from aluminum. Accomplishment of this replacement will 
reduce the susceptibility of the piston to corrosion damage. The Boeing 
service letter references Imperial Clevite, Inc., Service Bulletins 
G838-80-4, G838-80-5, and G838-80-6, all dated April 15, 1982, as 
additional sources of service information for accomplishment of the 
replacement.
    The FAA also has reviewed and approved Boeing Service Letter 747-
SL-32-19, dated January 16, 1980 (for Model 747 series airplanes). This 
service letter describes procedures for an inspection of the existing 
Waterman Type II hydraulic fuse assemblies for corrosion of the piston, 
and replacement of Type II hydraulic fuse assemblies with improved Type 
I fuse assemblies. Waterman Type II fuses require reverse flow to 
reset, while Type I fuses have a manual reset lever. The improved fuses 
are manufactured by Pneudraulics, Inc.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require replacement of Waterman hydraulic fuse 
assemblies with modified assemblies. The actions would be required to 
be accomplished in accordance with the service letters described 
previously.
    Affected operators of Model 737 series airplanes should note that, 
although Boeing Service Letter 737-SL-29-21 recommends that subsequent 
periodic tests of the modified fuses be accomplished, the FAA has not 
included such a requirement in this proposed AD. The FAA has determined 
that procedures required by operators' individual maintenance programs 
will adequately address periodic inspections of the new fuse 
assemblies.
    The FAA is considering the issuance of a separate rulemaking action 
to address fatigue and stress corrosion of the support fitting on the 
Krueger flap actuator for Model 737-100 and -200 series airplanes. (The 
Krueger flap actuator installed on Model 747 series airplanes has a 
different part number from that installed on Model 737 series 
airplanes.)

Cost Impact

    There are approximately 1,145 Model 737 series airplanes and 727 
Model 747 series airplanes of the affected design in the worldwide 
fleet.
    The FAA estimates that 421 Model 737 series airplanes of U.S. 
registry would be affected by this proposed AD, that it would take 
approximately 16 work hours per airplane (8 fuses per airplane; 2 work 
hours per fuse) to accomplish the proposed actions, and that the 
average labor rate is $60 per work hour. Required parts that are 
modified by the vendor would be provided at no cost to operators. Based 
on these figures, the cost impact of the

[[Page 18999]]

proposed AD on U.S. operators is estimated to be $404,160, or $960 per 
airplane.
    The FAA estimates that 208 Model 747 series airplanes of U.S. 
registry would be affected by this proposed AD, that it would take 
approximately 48 work hours per airplane (24 fuses per airplane; 2 work 
hours per fuse) to accomplish the proposed actions, and that the 
average labor rate is $60 per work hour. Required parts that are 
modified by the vendor would be provided at no cost to operators. Based 
on these figures, the cost impact of the proposed AD on U.S. operators 
is estimated to be $599,040, or $2,880 per airplane.
    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.

Regulatory Impact

    The regulations proposed herein would 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 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    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 USC 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

Boeing: Docket 96-NM-36-AD.

    Applicability: Model 737-100 and -200 series airplanes, as 
identified in Boeing Service Letter 737-SL-29-21, dated December 16, 
1982; and Model 747-100, -200, -300, and -SP series airplanes, as 
identified in Boeing Service Letter 747-SL-32-19, dated January 16, 
1980; certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
otherwise modified, altered, or repaired in the area subject to the 
requirements of this AD. For airplanes that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (d) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent failure of the hydraulic fuse, which could result in 
the failure of one or more hydraulic systems and resultant reduced 
controllability of the airplane, accomplish the following:
    (a) For Model 737-100 and -200 series airplanes: Within 3,000 
flight hours after the effective date of this AD, replace Waterman 
hydraulic fuse assemblies, having Waterman part number (P/N) G838-8-
40, G838-8-60, or G838-8-160, with modified assemblies having P/N 
G8381-8-40, G8381-8-60, or G8381-8-160, respectively; or with a 
Pneudraulics fuse specified in Boeing Service Letter 737-SL-29-21, 
dated December 16, 1982. Accomplish the replacement in accordance 
with the service letter.

    Note 2: The Boeing service letter references Imperial Clevite, 
Inc., Service Bulletins G838-80-4, G838-80-5, and G838-80-6, all 
dated April 15, 1982, as additional sources of service information 
for accomplishment of the replacement.

    (b) For Model 747-100, -200, -300, and -SP series airplanes: 
Within 3,000 flight hours after the effective date of this AD, 
replace Waterman hydraulic fuse assemblies, having Waterman P/N 
G905-120, with Pneudraulics assemblies having Pneudraulics P/N 6105, 
in accordance with Boeing Service Letter 747-SL-32-19, dated January 
16, 1980.
    (c) As of the effective date of this AD, no person shall install 
on any airplane Waterman hydraulic fuse assemblies having Waterman 
P/N G838-8-40, G838-8-60, G838-8-160, or G905-120 on any airplane.
    (d) 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 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (e) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the airplane to a location where 
the requirements of this AD can be accomplished.

    Issued in Renton, Washington, on April 24, 1996.
S.R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-10622 Filed 4-29-96; 8:45 am]
BILLING CODE 4910-13-U