[Federal Register Volume 59, Number 112 (Monday, June 13, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-13626]
Federal Register / Vol. 59, No. 112 / Monday, June 13, 1994 /
[[Page Unknown]]
[Federal Register: June 13, 1994]
VOL. 59, NO. 112
Monday, June 13, 1994
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 93-NM-182-AD; Amendment 39-8932; AD 94-12-04]
Airworthiness Directives; Boeing Model 747 Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
-----------------------------------------------------------------------
SUMMARY: This amendment adopts a new airworthiness directive (AD),
applicable to certain Boeing Model 747 series airplanes, that requires
repetitive inspections to detect cracking in certain fuselage skin lap
joints, and repair, if necessary. This amendment is prompted by the
results of extensive pressure fatigue tests conducted by the
manufacturer. The actions specified by this AD are intended to detect
and repair fatigue cracking in certain lap joints, which will ensure
safe operation of airplanes that have exceeded their economic design
goal.
DATES: Effective July 13, 1994.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of July 13, 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: Steven C. Fox, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (206) 227-2777; 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 series airplanes was published
in the Federal Register on December 17, 1993 (58 FR 65943). That action
proposed to require repetitive high frequency eddy current (HFEC)
inspections to detect cracking in certain fuselage skin lap joints, and
repair, if necessary.
Interested persons have been afforded an opportunity to participate
in the making of this amendment. Due consideration has been given to
the comments received.
One commenter supports the proposed rule.
One commenter requests that Revision 1 of Boeing Service Bulletin
747-53-2367, dated January 27, 1994, be included as an additional
source of service information. The FAA concurs. Since the issuance of
the proposal, the FAA has reviewed and approved Revision 1 of Boeing
Service Bulletin 747-53-2367, dated January 27, 1994, which clarifies
the procedures for accomplishment of the inspections described in the
Initial Release of the service bulletin, dated December 18, 1991 (which
was referenced in the proposal as the sole source of appropriate
service information). Therefore, paragraphs (a) and (c) of the final
rule have been revised to reference Revision 1 of the service bulletin
as an additional source of service information.
This same commenter requests that the proposed rule be revised to
include a reporting requirement to keep Boeing and the FAA advised of
findings of cracks. The FAA does not concur. The FAA has determined
that the unsafe condition addressed by this AD (which is to detect and
repair fatigue cracking in certain lap joints) will be adequately
addressed by paragraph (a) of the final rule, which requires the
inspection of certain lap joints, and paragraph (c) of the final rule,
which requires the repair of all cracks found during the inspection.
Therefore, since the final rule requires repetitive inspections to
detect cracks and repair of all findings of cracks, the FAA finds that
a reporting requirement would unduly burden operators.
This commenter further requests that the proposed rule be revised
to compensate for operators that fly with cabin pressure differentials
of 2.0 psi or less when calculating the number of flight cycles to
determine the compliance time. The FAA does not concur. The FAA finds
that operating at cabin pressure differentials of 2.0 psi or less is
applicable to only one operator. Since there are numerous factors that
affect the calculation of flight cycles, such as total number of low
pressure cycles, amount of thrust, number of gross weight flight
cycles, etc., the FAA has determined that these mitigating factors
could be best evaluated through requests for alternative methods of
compliance, as provided for in paragraph (d) of the final rule.
One commenter requests that the proposed compliance time of 22,000
flight cycles be extended to 25,000 flight cycles to inspect the lap
joints in areas outside of Stringer 14 since data indicate that
cracking in these areas did not occur until after 25,000 flight cycles.
The FAA does not concur. In developing an appropriate compliance time
for this AD, the FAA not only evaluated the fatigue test data that was
provided by the manufacturer, but took into consideration the size of
the test sample: the test results were based upon just one airplane
that had no loads and was not pressurized. Based on this data, the FAA
determined that 22,000 flight cycles represented a conservative
threshold for initiating inspections so as to ensure that any cracking
initiation would be found in a timely manner.
Another commenter requests that the proposed compliance time of
3,000 flight cycles to perform the repetitive inspections be extended
to 4,300 flight cycles to coincide with operators' regularly scheduled
maintenance periods. The FAA does not concur. The FAA has determined
that the compliance time, as proposed, represents the maximum interval
of time allowable for the affected airplanes to continue to operate
without compromising safety. In developing this inspection interval,
the FAA evaluated the reliability of the inspection method and the
results of fatigue test data. The FAA found that extending this
interval by more than one-third would allow cracks to propagate
undetected, which would adversely affect the structural integrity of
the airplane.
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 change previously
described. The FAA has determined that this change will neither
increase the economic burden on any operator nor increase the scope of
the AD.
There are approximately 723 Model 747 series airplanes of the
affected design in the worldwide fleet. The FAA estimates that 183
airplanes of U.S. registry will be affected by this AD, that it will
take approximately 14 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 $140,910, or $770 per airplane.
The total cost impact figure discussed above is based on
assumptions that no operator has yet accomplished any of the
requirements of this AD action, and that no operator would accomplish
those actions in the future if this AD were not adopted.
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:
94-12-04 Boeing: Amendment 39-8932. Docket 93-NM-182-AD.
Applicability: Model 747-100, -200, -300, 747SP, and 747SR
series airplanes, as listed in Boeing Service Bulletin 747-53-2367,
dated December 18, 1991, certificated in any category.
Compliance: Required as indicated, unless accomplished
previously.
To prevent structural failure in the fuselage due to fatigue
cracking in certain lap joints, accomplish the following:
(a) Prior to the accumulation of 22,000 full pressure flight
cycles (or, if the external skin panel of an affected lap joint has
been replaced: Prior to the accumulation of 22,000 full pressure
flight cycles since skin replacement), or within 1,000 landings
after the effective date of this AD, whichever occurs later, perform
an external surface high frequency eddy current (HFEC) inspection of
the skin around the upper row of fasteners in accordance with the
Accomplishment Instructions of Boeing Service Bulletin 747-53-2367,
dated December 18, 1991; or Revision 1, dated January 27, 1994.
(b) If no crack is found, repeat the inspection at intervals not
to exceed 3,000 full pressure flight cycles.
(c) If any crack is found, accomplish paragraphs (c)(1) and
(c)(2) of this AD.
(1) Prior to further flight, perform an open hole HFEC
inspection to detect cracking in the upper row fastener holes
between the adjacent frames in accordance with the Accomplishment
Instructions of Boeing Service Bulletin 747-53-2367, dated December
18, 1991; or Revision 1, dated January 27, 1994. Prior to further
flight, repair any crack found in accordance with the 747 Structural
Repair Manual, Chapter 53-30-03.
(2) Repeat the inspection required by paragraph (a) of this AD
at intervals not to exceed 3,000 full pressure flight cycles.
(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: 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
Secs. 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.
(f) The inspections shall be done in accordance with Boeing
Service Bulletin 747-53-2367, dated December 18, 1991; or Boeing
Service Bulletin 747-53-2367, Revision 1, dated January 27, 1994.
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.
(g) This amendment becomes effective on July 13, 1994.
Issued in Renton, Washington, on May 31, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 94-13626 Filed 6-10-94; 8:45 am]
BILLING CODE 4910-13-U