[Federal Register: December 1, 2004 (Volume 69, Number 230)]
[Proposed Rules]
[Page 69844-69847]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr01de04-19]
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2004-19755; Directorate Identifier 2004-NM-23-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 747 Airplanes
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking (NPRM).
-----------------------------------------------------------------------
SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for certain Boeing Model 747 airplanes. This proposed AD would require
repetitive tests to detect hot air leaking from the trim air diffuser
ducts or sidewall riser duct assemblies (collectively referred to in
this proposed AD as ``TADDs''), related investigative actions, and
corrective actions if necessary. This proposed AD also would provide an
optional terminating action for the repetitive tests. This proposed AD
is prompted by reports of deteriorating sealants both inside and
outside the center wing fuel tank due to heat damage from leaking
TADDs. We are proposing this AD to prevent leakage of fuel or fuel
vapors into areas where ignition sources may be present, which could
result in a fire or explosion.
DATES: We must receive comments on this proposed AD by January 18,
2005.
ADDRESSES: Use one of the following addresses to submit comments on
this proposed AD.
DOT Docket Web site: Go to http://dms.dot.gov and follow
the instructions for sending your comments electronically.
Government-wide rulemaking Web site: Go to http://www.regulations.gov
and follow the instructions for sending your
comments electronically.
Mail: Docket Management Facility, U.S. Department of
Transportation, 400 Seventh Street, SW., Nassif Building, room PL-401,
Washington, DC 20590.
By fax: (202) 493-2251.
Hand Delivery: Room PL-401 on the plaza level of the
Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
For service information identified in this proposed AD, contact
Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-
2207.
You can examine the contents of this AD docket on the Internet at
http://dms.dot.gov, or at the Docket Management Facility, U.S.
Department of Transportation, 400 Seventh Street, SW., room PL-401, on
the plaza level of the Nassif Building, Washington, DC.
FOR FURTHER INFORMATION CONTACT:
Technical information: Dan Kinney, Aerospace Engineer, Propulsion
Branch, ANM-140S, FAA, Seattle Aircraft Certification Office, 1601 Lind
Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6499;
fax (425) 917-6590.
Plain language information: Marcia Walters, marcia.walters@faa.gov.
SUPPLEMENTARY INFORMATION:
Docket Management System (DMS)
The FAA has implemented new procedures for maintaining AD dockets
electronically. As of May 17, 2004, new AD actions are posted on DMS
and assigned a docket number. We track each action and assign a
corresponding directorate identifier. The DMS AD docket number is in
the form ``Docket No. FAA-2004-99999.'' The Transport Airplane
Directorate identifier is in the form ``Directorate Identifier 2004-NM-
999-AD.'' Each DMS AD docket also lists the directorate identifier
(``Old Docket Number'') as a cross-reference for searching purposes.
Comments Invited
We invite you to submit any relevant written data, views, or
arguments regarding this proposed AD. Send your comments to an address
listed under ADDRESSES. Include ``Docket No. FAA-2004-19755;
Directorate Identifier 2004-NM-23-AD'' in the subject line of your
comments. We specifically invite comments on the overall regulatory,
economic, environmental, and energy aspects of the proposed AD. We will
consider all comments submitted by the closing date and may amend the
proposed AD in light of those comments.
We will post all comments we receive, without change, to http://dms.dot.gov
, including any personal information you provide. We will
also post a report summarizing each substantive verbal contact with FAA
personnel concerning this proposed AD. Using the search function of
that Web site, anyone can find and read the comments in any of our
dockets, including the name of the individual who sent the comment (or
signed the comment on behalf of an association, business, labor union,
etc.). You can review DOT's complete Privacy Act Statement in the
Federal Register published on April 11, 2000 (65 FR 19477-78), or you
can visit http://dms.dot.gov.
[[Page 69845]]
We are reviewing the writing style we currently use in regulatory
documents. We are interested in your comments on whether the style of
this document is clear, and your suggestions to improve the clarity of
our communications that affect you. You can get more information about
plain language at http://www.faa.gov/language and http://www.plainlanguage.gov.Examining
the Docket
You can examine the AD docket on the Internet at http://dms.dot.gov
, or in person at the Docket Management Facility office
between 9 a.m. and 5 p.m., Monday through Friday, except Federal
holidays. The Docket Management Facility office (telephone (800) 647-
5227) is on the plaza level of the Nassif Building at the DOT street
address stated in the ADDRESSES section. Comments will be available in
the AD docket shortly after the DMS receives them.
Discussion
We have received a report indicating that inspections have revealed
deteriorating sealants both inside and outside the center wing fuel
tank on certain Boeing Model 747 airplanes. The deterioration is
attributed to damage caused by hot air leaking from the trim air
diffuser ducts or sidewall riser duct assemblies (collectively referred
to in this proposed AD as ``TADDs''), which are part of the cabin air
distribution system that is located between the top of the center wing
fuel tank and the floor of the passenger cabin. These hot air leaks
occur when the fiberglass diffuser ducts are damaged by the hot bleed
air that they carry, leading the fiberglass diffuser ducts to leak or
disconnect from the titanium trim air manifold. The release of hot air
can damage the upper skin of the center wing section, the longitudinal
floor beams, and the fuselage frame intercostals, as well as the
sealants of the center wing fuel tank. Damage to the sealants inside or
outside the center wing fuel tank could allow fuel or fuel vapors to
leak into an area where ignition sources may be present. This
condition, if not corrected, could result in a fire or explosion.
Relevant Service Information
We have reviewed Boeing Alert Service Bulletin 747-21A2418,
Revision 2, dated March 4, 2004; including Information Notice (IN) 747-
21A2418 IN 01, dated March 11, 2004. The service bulletin describes
procedures for repetitive tests to detect hot air leaking from the
TADDs, related investigative actions, and corrective actions if
necessary. The related investigative actions are repetitive general
visual inspections for discrepancies or damage of the TADDs; and, if
necessary, for damage of adjacent structure, the primary and secondary
fuel barriers of the center wing fuel tank, control cables, and cable
pulleys, and for raised cable seals. The corrective actions, if any
damage is found, consist of replacing any damaged TADD with a new TADD
having the same part number, or a new, improved TADD that has a higher
temperature tolerance; and repairing any damage to adjacent structure,
the primary and secondary fuel barriers of the center wing fuel tank,
control cables, cable pulleys, or raised cable seals. After a TADD is
replaced with a new TADD having the same part number, there is no need
to test or inspect the replaced TADD until 21,200 flight hours after
the replacement. After a TADD is replaced with a new, improved TADD,
the repetitive inspections are no longer needed for that TADD.
Accomplishing the actions specified in the service information is
intended to adequately address the unsafe condition.
IN 747-21A2418 IN 01 identifies some headings that were
inadvertently omitted from the Accomplishment Instructions of Boeing
Alert Service Bulletin 747-21A2418, Revision 2. These headings clarify
what procedures apply to which airplane configuration.
The service bulletin refers to Chapter 21-61-20 of the 747 Airplane
Maintenance Manual as an additional source for service information for
the test and inspection of the TADDs. Chapter 21-61-20 contains, among
other things, detailed procedures for the general visual inspection of
the TADDs for damage or discrepancies, including detachment of the trim
air duct from the diffuser duct, delamination, missing or softened
surface material, or blackened material. For any discrepant TADD,
Chapter 21-61-20 also describes procedures for a general visual
inspection for damage of the primary and secondary fuel barriers of the
center wing tank; structure adjacent to the discrepant TADD; and
cables, cable pulleys, and raised cable seals in the over-wing area.
FAA's Determination and Requirements of the Proposed AD
We have evaluated all pertinent information and identified an
unsafe condition that is likely to exist or develop on other airplanes
of this same type design. Therefore, we are proposing this AD, which
would require doing the actions specified in the service information
described previously, except as discussed under ``Differences Between
the Proposed AD and Service Information.''
This proposed AD also provides an optional terminating action for
the repetitive inspections, which is replacing the existing TADDs with
new, improved TADDs. We have determined that it is acceptable to allow
you to continue doing repetitive tests and inspections in lieu of
requiring that you do the terminating action. In making this
determination, we considered that long-term continued operational
safety in this case will be adequately ensured by repetitive
inspections to detect hot air leaking from the TADDs or discrepancies
of the TADDs before these conditions are a hazard to the airplane.
Clarification of Proposed Requirements
This proposed AD would require that any replacement TADD must be
new. Used TADDs are not acceptable replacement parts. Because the
material of the TADDs deteriorates at a known rate, an operator would
have to know how many total flight hours had been accumulated on a
serviceable TADD, and would have to test and inspect that TADD at
appropriate intervals. We find that it is unlikely that operators will
have all of the data that would be needed for a serviceable TADD to be
an acceptable replacement. Therefore, this proposed AD would allow
replacement only with new parts.
Differences Between the Proposed AD and Service Information
For the hot air leak test, the service bulletin provides a
compliance time of the earlier of 180 days or 2,000 flight hours after
the release date of Revision 2 of the service bulletin, once the
airplane has accumulated 20,000 total flight hours. For this test, this
proposed AD would require the initial test to be done prior to the
accumulation of 21,200 flight hours, or within 1,200 flight hours after
the effective date of this AD, whichever is later. This compliance time
is the equivalent of the inspection threshold of 20,000 total flight
hours, plus a grace period of 1,200 flight hours (which is equivalent
to one repetitive interval, as specified in the service bulletin). In
developing an appropriate compliance time for this AD, we considered
the manufacturer's recommendation, and the degree of urgency associated
with the subject unsafe condition. In light of these factors, we find
that a 1,200-flight-hour grace period represents an appropriate
interval of time for affected airplanes (with close to or more than
20,000 total flight hours as of the effective date of the AD) to
continue to operate without compromising safety.
[[Page 69846]]
Costs of Compliance
This proposed AD would affect about 1,305 airplanes worldwide. The
following table provides the estimated costs for U.S. operators to
comply with this proposed AD.
Estimated Costs
----------------------------------------------------------------------------------------------------------------
Average Number of
Work labor Cost per U.S.-
Action hours rate per Parts airplane registered Fleet cost
hour airplanes
----------------------------------------------------------------------------------------------------------------
Hot air leak test............ 3 $65 None....... $195 per test 246 $47,970 per
cycle. test cycle.
General visual inspection.... 5 65 None....... $325 per 246 $79,950 per
inspection inspection
cycle. cycle.
----------------------------------------------------------------------------------------------------------------
Regulatory Findings
We have determined that this proposed AD would not have federalism
implications under Executive Order 13132. This proposed AD would not
have a substantial direct effect 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.
For the reasons discussed above, I certify that the 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. 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.
We prepared a regulatory evaluation of the estimated costs to
comply with this proposed AD. See the ADDRESSES section for a location
to examine the regulatory evaluation.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Safety.
The Proposed Amendment
Accordingly, under the authority delegated to me by the
Administrator, the FAA proposes to amend 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. The FAA amends Sec. 39.13 by adding the following new
airworthiness directive (AD):
Boeing: Docket No. FAA-2004-19755; Directorate Identifier 2004-NM-
23-AD.
Comments Due Date
(a) The Federal Aviation Administration (FAA) must receive
comments on this AD action by January 18, 2005.
Affected ADs
(b) None.
Applicability
(c) This AD applies to Boeing Model 747-100, 747-100B, 747-100B
SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 747-
400F, 747SR, and 747SP series airplanes; certificated in any
category; line numbers 1 through 1316 inclusive.
Unsafe Condition
(d) This AD was prompted by reports of deteriorating sealants
both inside and outside the center wing fuel tank due to heat damage
from leaking trim air diffuser ducts or sidewall riser duct
assemblies (collectively referred to in this AD as ``TADDs''). We
are issuing this AD to prevent leakage of fuel or fuel vapors into
areas where ignition sources may be present, which could result in a
fire or explosion.
Compliance
(e) You are responsible for having the actions required by this
AD performed within the compliance times specified, unless the
actions have already been done.
Repetitive Tests and Inspections
(f) Do the actions in Table 1 of this AD at the times specified
in Table 1 of this AD, in accordance with the Accomplishment
Instructions of Boeing Alert Service Bulletin 747-21A2418, Revision
2, dated March 4, 2004; including Information Notice 747-21A2418 IN
01, dated March 11, 2004.
Table 1.--Compliance Times
------------------------------------------------------------------------
Then repeat within
this interval
Do this action-- Initially at the until paragraph
later of-- (j) is done--
------------------------------------------------------------------------
(1) Repetitive test to detect Prior to the 1,200 flight
hot air leaking from TADDs. accumulation of hours.
21,200 total
flight hours, or
within 1,200
flight hours
after the
effective date of
this AD.
(2) General visual inspection Prior to the 7,000 flight
for damage or discrepancies of accumulation of hours.
the TADDs. 27,000 total
flight hours, or
within 7,000
flight hours
after the
effective date of
this AD, except
as provided by
paragraph (g) of
this AD.
------------------------------------------------------------------------
Note 1: For the purposes of this AD, a general visual inspection
is: ``A visual examination of an interior or exterior area,
installation, or assembly to detect obvious damage, failure, or
irregularity. This level of inspection is made from within touching
distance unless otherwise specified. A mirror may be necessary to
ensure visual access to all surfaces in the inspection area. This
level of inspection is made under normally available lighting
conditions such as daylight, hangar lighting, flashlight, or
droplight and may require removal or opening of access panels or
doors. Stands, ladders, or platforms may be required to gain
proximity to the area being checked.''
Note 2: Boeing Alert Service Bulletin 747-21A2418, Revision 2,
refers to Chapter 21-61-20 of the 747 Airplane Maintenance Manual as
an additional source for service information for the test and
inspections of the TADDs.
(g) If any hot air leak is found during any test required by
paragraph (f) of this AD: Before further flight, do the general
visual inspection for damage or discrepancies of the TADDs, in
accordance with the
[[Page 69847]]
Accomplishment Instructions of Boeing Alert Service Bulletin 747-
21A2418, Revision 2, dated March 4, 2004; including Information
Notice 747-21A2418 IN 01, dated March 11, 2004.
Corrective Actions
(h) If any damage or discrepancy is found during any general
visual inspection for damage required by paragraph (f) or (g) of
this AD: Before further flight, perform a general visual inspection
for damage of the primary and secondary fuel barriers of the center
wing tank; structure adjacent to the discrepant TADD; and cables,
cable pulleys, and raised cable seals in the over-wing area; do
applicable repairs; and replace the damaged TADD with a new TADD
having the same part number or a new, improved TADD having a part
number listed in the ``New TADD Part Number'' or ``New Sidewall
Riser Duct Assy Part Number'' column, as applicable, of the tables
in Section 2.C.2. of the service bulletin. Do all of these actions
in accordance with the Accomplishment Instructions of Boeing Alert
Service Bulletin 747-21A2418, Revision 2, dated March 4, 2004;
including Information Notice 747-21A2418 IN 01, dated March 11,
2004. Then, repeat the test and inspection required by paragraph (f)
of this AD at the times specified in Table 1 of this AD, except as
provided by paragraphs (i) and (j) of this AD.
Note 3: Only new TADDs, not used ones, are acceptable as
replacement parts, as specified in paragraph (h) of this AD.
(i) For any TADD, whether damaged or not, that is replaced with
a new TADD having the same part number as the TADD being replaced:
Within 21,200 flight hours after the TADD is replaced, do the test
to detect hot air leaking from the replaced TADD, and within 27,000
flight hours after the TADD is replaced, do the general visual
inspection for damage, as specified in paragraph (f) of this AD.
Thereafter, repeat the test and inspection at the repetitive
intervals specified in Table 1 of this AD.
Optional Terminating Action
(j) For any TADD that is replaced with a new, improved TADD
having a part number listed in the ``New TADD Part Number'' or ``New
Sidewall Riser Duct Assy Part Number'' column, as applicable, of the
tables in Section 2.C.2. of Boeing Alert Service Bulletin 747-
21A2418, Revision 2, dated March 4, 2004; including Information
Notice 747-21A2418 IN 01, dated March 11, 2004: The repetitive tests
and inspections required by this AD are terminated for the TADD that
is replaced with a new, improved TADD.
Previously Accomplished Actions
(k) Actions accomplished before the effective date of this AD in
accordance with Boeing Alert Service Bulletin 747-21A2418, dated
November 14, 2002; or Revision 1, dated October 16, 2003; are
acceptable for compliance with the corresponding actions required by
this AD.
Alternative Methods of Compliance (AMOCs)
(l) The Manager, Seattle Aircraft Certification Office (ACO),
FAA, has the authority to approve AMOCs for this AD, if requested in
accordance with the procedures found in 14 CFR 39.19.
Issued in Renton, Washington, on November 17, 2004.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 04-26492 Filed 11-30-04; 8:45 am]
BILLING CODE 4910-13-P