[Federal Register Volume 61, Number 252 (Tuesday, December 31, 1996)]
[Rules and Regulations]
[Pages 69026-69027]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-33041]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 96-NM-279-AD; Amendment 39-9867; AD 96-26-04]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 747 Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule; request for comments.
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SUMMARY: This amendment adopts a new airworthiness directive (AD) that
is applicable to certain Boeing Model 747 series airplanes. This action
requires a one-time inspection to detect fatigue cracking of the
vertical beam webs and chords of the nose wheel well (NWW) at body
station (BS) 300 and BS 320, and repair, if necessary. This action also
requires inspections to detect fatigue cracking of the inner chord and
web of the fuselage frames at BS 300 and BS 320, and repair, if
necessary. This amendment is prompted by a report indicating that the
fuselage frames at BS 300 and BS 320 severed approximately 10 inches
outboard of the NWW side panel and resulted in accelerated fatigue
cracking and subsequent failure of the adjacent NWW vertical beams. The
actions specified in this AD are intended to detect and correct such
fatigue cracking, which could result in collapse of the NWW pressure
bulkhead and subsequent rapid decompression of the airplane.
DATES: Effective January 6, 1997.
Comments for inclusion in the Rules Docket must be received on or
before March 3, 1997.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 96-NM-279-AD, 1601 Lind Avenue, SW.,
Renton, Washington 98055-4056.
FOR FURTHER INFORMATION CONTACT: Bob Breneman, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office,
1601 Lind Avenue, SW., Renton, Washington; telephone (206) 227-2776;
fax (206) 227-1181.
SUPPLEMENTARY INFORMATION: The FAA has received a report indicating
that the flight crew of a Boeing Model 747-200 series airplane heard a
loud noise below the cockpit area during flight descent. The flight
continued with an uneventful landing. Investigation revealed that the
left-hand side wall of the nose wheel well (NWW) was bulging. Further
investigation revealed that the fuselage frames at body stations (BS)
300 and BS 320 had severed approximately 10 inches outboard of the NWW
side panel. Additionally, the vertical beam of the NWW at BS 300
contained multiple cracks in the inner chord, a severed web, and a
cracked and deformed outer chord. The vertical beam of the NWW at BS
320 also was found to have a severed web and cracks in the radius of
the inner chord, as well as severe damage to numerous horizontal
stiffeners and clips. The apparent cause of this cracking is fatigue.
Fatigue cracking of the BS 300 and BS 320 fuselage frames in the
area of the NWW, if not detected and corrected in a timely manner,
could result in collapse of the NWW pressure bulkhead, and subsequent
rapid decompression of the airplane.
Other Relevant Rulemaking
The FAA previously issued AD 90-06-14, amendment 39-6544 (55 FR
10045, March 19, 1990), which is applicable to certain Boeing Model 747
series airplanes. [A correction of that rule was published in the
Federal Register on May 18, 1990 (55 FR 20590).] That AD requires
repetitive visual inspections to detect fatigue cracking of the
vertical beams, webs, clips, side wall web, top panel and intercostals
of the NWW. That AD requires that the initial inspection be
accomplished prior to the accumulation of 10,000 total flight cycles,
and that repetitive inspections be accomplished at intervals of 1,500
or 3,000 flight cycles, depending on the inspection method used.
The FAA also issued AD 91-11-01, amendment 39-6997 (56 FR 22306,
May 15, 1991), which also is applicable to certain Boeing Model 747
series airplanes. That AD requires the inspection to detect fatigue
cracking of the fuselage frames adjacent to the NWW, prior to the
accumulation of 16,000 flight cycles. That AD provides an optional
terminating modification that entails installing new fuselage frames
(including the frames adjacent to the NWW) with improved durability.
That modification is required prior to the accumulation of 20,000
flight cycles in accordance with AD 90-06-06 (aging fleet AD).
The airplane involved in the incident described previously had
accumulated 14,341 total flight cycles at the time of structural
failure. A visual inspection to detect cracking of the vertical beams
of the NWW in accordance with AD 90-06-14 had been performed only 621
cycles prior to the reported failure. The fuselage frames in its NWW
area had not yet been replaced with the new, improved durability frames
in accordance with AD 91-11-01.
Explanation of the Requirements of the Rule
Since an unsafe condition has been identified that is likely to
exist or develop on other Boeing Model 747 series airplanes of the same
type design, this AD is being issued to detect and correct fatigue
cracking of BS 300 and BS 320 fuselage frames adjacent to the NWW,
which could result in collapse of the NWW pressure bulkhead and
possibly result in rapid decompression of the airplane. This AD
requires repetitive visual inspections to detect fatigue cracking of
the inner chord and web of the left and right side of fuselage frames
at BS 300 and BS 320, from the NWW side panel outboard to stringer 39.
This AD also requires a one-time visual inspection to detect fatigue
cracking of the vertical beam webs and chords of the NWW at BS 300 and
BS 320. This AD also requires that any cracking detected during those
inspections be repaired in accordance with a method approved by the
FAA.
Interim Action
This is considered to be interim action until final action is
identified, at which time the FAA may consider further rulemaking.
Determination of Rule's Effective Date
Since a situation exists that requires the immediate adoption of
this regulation, it is found that notice and opportunity for prior
public comment hereon are impracticable, and that good cause exists for
making this amendment effective in less than 30 days.
Comments Invited
Although this action is in the form of a final rule that involves
requirements affecting flight safety and, thus, was not preceded by
notice and an opportunity for public comment, comments are invited on
this rule. Interested persons are invited to comment on this rule by
submitting such written data, views, or arguments as they may desire.
Communications shall identify the
[[Page 69027]]
Rules Docket number and be submitted in triplicate to the address
specified under the caption ADDRESSES. All communications received on
or before the closing date for comments will be considered, and this
rule may be amended in light of the comments received. Factual
information that supports the commenter's ideas and suggestions is
extremely helpful in evaluating the effectiveness of the AD action and
determining whether additional rulemaking action would be needed.
Comments are specifically invited on the overall regulatory,
economic, environmental, and energy aspects of the rule that might
suggest a need to modify the 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 that
summarizes each FAA-public contact concerned with the substance of this
AD will be filed in the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments
submitted in response to this rule must submit a self-addressed,
stamped postcard on which the following statement is made: ``Comments
to Docket Number 96-NM-279-AD.'' The postcard will be date stamped and
returned to the commenter.
Regulatory Impact
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.
The FAA has determined that this regulation is an emergency
regulation that must be issued immediately to correct an unsafe
condition in aircraft, and that it is not a ``significant regulatory
action'' under Executive Order 12866. It has been determined further
that this action involves an emergency regulation under DOT Regulatory
Policies and Procedures (44 FR 11034, February 26, 1979). If it is
determined that this emergency regulation otherwise would be
significant under DOT Regulatory Policies and Procedures, a final
regulatory evaluation will be prepared and placed in the Rules Docket.
A copy of it, if filed, 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, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration amends 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 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
96-26-04 Boeing: Amendment 39-9867. Docket 96-NM-279-AD.
Applicability: Model 747 series airplanes having line numbers 1
through 678 inclusive; on which the Section 41 frame replacement in
zone 1 specified in Boeing Service Bulletin 747-53-2272 has not been
accomplished; 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 (c) 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 detect and correct fatigue cracking of body station (BS) 300
and BS 320 fuselage frames adjacent to the nose wheel well (NWW),
which could result in collapse of the NWW pressure bulkhead, and
subsequent rapid decompression of the airplane, accomplish the
following:
(a) Prior to the accumulation of 10,000 total flight cycles, or
within 50 flight cycles after the effective date of this AD,
whichever occurs later, perform a detailed visual inspection to
detect fatigue cracking of the inner chord and web of the left side
and right side of BS 300 and BS 320 fuselage frames from the nose
wheel well (NWW) side panel outboard to stringer 39, in accordance
with normal maintenance practices. Pay particular attention to the
area where the NWW vertical beam inner chord interfaces with the
fuselage frame.
(1) If no cracking is detected, repeat the detailed visual
inspection thereafter at intervals not to exceed 100 flight cycles.
(2) If any cracking is detected, prior to further flight, repair
in accordance with a method approved by the Manager, Seattle
Aircraft Certification Office (ACO), FAA, Transport Airplane
Directorate.
(b) Prior to the accumulation of 10,000 total flight cycles, or
within 50 flight cycles after the effective date of this AD,
whichever occurs later, perform a detailed one-time visual
inspection to detect fatigue cracking of the left and right side
vertical beam webs and chords of the NWW at BS 300 and BS 320, in
accordance with normal maintenance procedures.
(1) If no cracking is detected, no further action is required by
this paragraph.
(2) If any cracking is detected, prior to further flight, repair
in accordance with a method approved by the Manager, Seattle ACO.
(c) 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 2: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
(d) 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.
(e) This amendment becomes effective on January 6, 1997.
Issued in Renton, Washington, on December 20, 1996.
S. R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 96-33041 Filed 12-30-96; 8:45 am]
BILLING CODE 4910-13-U
