[Federal Register Volume 60, Number 219 (Tuesday, November 14, 1995)]
[Rules and Regulations]
[Pages 57174-57177]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-27913]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95-NM-206-AD; Amendment 39-9426; AD 95-23-06]


Airworthiness Directives; British Aerospace Model BAe 146-100A, -
200A, and -300A Airplanes and Model Avro 146-RJ70A, -RJ85A, and RJ-100A 
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 

[[Page 57175]]
applicable to certain British Aerospace Model BAe 146-100A, -200A, and 
-300A airplanes and Model Avro 146-RJ70A, -RJ85A, and RJ-100A 
airplanes. This action requires inspections to detect cracking and 
evidence of exhaust leaks in the forward face of the central panel of 
the forward firewall of the auxiliary power unit (APU) bay, and 
replacement of the central panel with a new panel, if necessary. This 
amendment is prompted by a report indicating that cracking due to 
leakage of hot exhaust gases was found in the forward face of the 
forward firewall of the APU bay. The actions specified in this AD are 
intended to prevent such gas leakage and subsequent cracking, which 
could damage the wiring to the APU fire bottle; this condition could 
result in failure of the APU fire bottle to discharge in the event of 
an APU fire.

DATES: Effective November 29, 1995.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of November 29, 1995.
    Comments for inclusion in the Rules Docket must be received on or 
before January 16, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 95-NM-206-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. The service information referenced in 
this AD may be obtained from British Aerospace Holding, Inc., Avro 
International Aerospace Division, P.O. Box 16039, Dulles International 
Airport, Washington, DC 20041-6039. This information may be examined 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.

FOR FURTHER INFORMATION CONTACT: Tim Backman, Aerospace Engineer, 
Standardization Branch, ANM-113, FAA, Transport Airplane Directorate, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 
227-2797; fax (206) 227-1149.

SUPPLEMENTARY INFORMATION: The Civil Aviation Authority (CAA), which is 
the airworthiness authority for the United Kingdom, recently notified 
the FAA that an unsafe condition may exist on certain British Aerospace 
Model BAe 146-100A, -200A, and -300A airplanes and Model Avro 146-
RJ70A, -RJ85A, and RJ-100A airplanes. The CAA advises that it received 
a report indicating that cracking was found in the aluminum face plate 
on the forward side of the central panel of the forward firewall of the 
auxiliary power unit (APU) bay on a British Aerospace Model BAe 146 
series airplane. Hot exhaust gases escaped through the sealing system 
used around the duct at the central panel of the forward firewall of 
the APU bay. Exposure to these hot gases resulted in cracking of the 
aluminum alloy portion of the central panel. Leakage of additional hot 
gases through the seal and resultant cracking could damage the wiring 
to the APU fire bottle. This condition, if not corrected, could result 
in failure of the APU fire bottle to discharge in the event of an APU 
fire.
    British Aerospace has issued Service Bulletin S.B.26-35, Revision 
1, dated August 30, 1995, which describes procedures for repetitive 
close detailed visual inspections to detect cracking and evidence of 
exhaust leaks in the forward face of the central panel of the forward 
firewall of the APU bay. For airplanes on which both cracking and 
evidence of gas leakage are found, the service bulletin specifies that 
operation of the APU must be prohibited either when the aircraft is on 
the ground or in flight until the central panel has been replaced with 
a new panel. The CAA classified this service bulletin as mandatory in 
order to assure the continued airworthiness of these airplanes in the 
United Kingdom.
    British Aerospace also has issued Service Bulletin SB.26-35-36179A, 
dated August 4, 1995, which describes procedures for replacement of the 
central panel (constructed of aluminum alloy) of the forward firewall 
of the APU bay with a new panel constructed of titanium TA2 
(Modification HCM36179A). The modification also involves replacing the 
associated stiffeners. The titanium central panel will provide better 
resistance to cracking at high temperatures. Accomplishment of this 
modification eliminates the need for repetitive inspections of the 
forward face of the central panel of the forward firewall of the APU 
bay.
    For airplanes on which the previously described modification has 
not been accomplished, British Aerospace also has issued Service 
Bulletin SB.26-36-36179B, dated June 22, 1995, which describes 
procedures for installation of a protective aluminum alloy shield on 
the vertical stiffener (left-hand) next to the exhaust aperture of the 
forward firewall of the APU bay (Modification HCM36179B). 
Accomplishment of the installation provides protection of the wiring 
installation of the APU fire bottle. The service bulletin specifies 
that accomplishment of this installation increases the interval for 
repetitive inspections of the forward face of the central panel of the 
forward firewall of the APU bay to coincide with regularly scheduled 
maintenance of the affected airplanes.
    These airplane models are manufactured in the United Kingdom and 
are type certificated for operation in the United States under the 
provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 
21.29) and the applicable bilateral airworthiness agreement. Pursuant 
to this bilateral airworthiness agreement, the CAA has kept the FAA 
informed of the situation described above. The FAA has examined the 
findings of the CAA, reviewed all available information, and determined 
that AD action is necessary for products of this type design that are 
certificated for operation in the United States.
    Since an unsafe condition has been identified that is likely to 
exist or develop on other airplanes of the same type design registered 
in the United States, this AD is being issued to prevent leakage of hot 
exhaust gases and subsequent cracking of the forward face of the 
forward firewall of the APU bay, which could damage the wiring to the 
APU fire bottle and result in failure of the APU fire bottle to 
discharge in the event of an APU fire. This AD requires repetitive 
close detailed visual inspections to detect cracking and evidence of 
exhaust leaks in the forward face of the central panel of the forward 
firewall of the APU bay, and replacement of the central panel with a 
new panel, if necessary. Such replacement, if accomplished, constitutes 
terminating action for the requirements of this AD. For airplanes on 
which cracking and evidence of gas leakage are found, this AD also 
prohibits operation of the APU (either when the aircraft is on the 
ground or in flight) until the central panel has been replaced with a 
new panel. This AD also provides for installation of a protective 
aluminum alloy shield on the vertical stiffener (left-hand) next to the 
exhaust aperture of the forward firewall of the APU bay, which, if 
accomplished, increases the interval for repetitive inspections of the 
forward face of the central panel of the forward firewall of the APU 
bay. The actions are required to be accomplished in accordance with the 
service bulletins described previously.
    Operators should note that, for airplanes on which cracks are 
found, but no evidence of gas leakage is found, British Aerospace 
Service Bulletin S.B.26-35 recommends that daily inspections be 
accomplished and that 

[[Page 57176]]
corrective action be accomplished at the ``next convenient downtime.'' 
This AD, however, requires daily inspections and accomplishment of the 
corrective action (replacement of the central panel) within 14 days 
after crack detection. The FAA finds that a 14-day compliance time will 
address the unsafe condition in a timely manner and will decrease 
reliance on daily inspections, which require approximately one work 
hour to perform.
    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 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 95-NM-206-AD.'' The postcard will be date stamped and 
returned to the commenter.
    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, Incorporation by 
reference, 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 USC 106(g), 40101, 40113, 44701.
Sec. 39.13  [Amended]
    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

95-23-06 British Aerospace Regional Aircraft Limited, Avro 
International Aerospace Division (Formerly British Aerospace, plc; 
British Aerospace Commercial Aircraft Limited): Amendment 39-9426. 
Docket 95-NM-206-AD.

    Applicability: Model BAe 146-100A, -200A, and -300A airplanes, 
and Model Avro 146-RJ70A, -RJ85A, and RJ-100A airplanes; on which 
British Aerospace Modification HCM36019A is installed; 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 use the authority 
provided in paragraph (d) of this AD to request approval from the 
FAA. This approval may address either no action, if the current 
configuration eliminates the unsafe condition; or different actions 
necessary to address the unsafe condition described in this AD. Such 
a request should include an assessment of the effect of the changed 
configuration on the unsafe condition addressed by this AD. In no 
case does the presence of any modification, alteration, or repair 
remove any airplane from the applicability of this AD.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent leakage of hot exhaust gases and subsequent cracking 
of the forward face of the forward firewall of the auxiliary power 
unit (APU) bay, which could damage the wiring to the APU fire bottle 
and result in failure of the APU fire bottle to discharge in the 
event of an APU fire, accomplish the following:
    (a) Within 7 days after the effective date of this AD: Perform a 
close detailed visual inspection to detect cracking and evidence of 
exhaust leaks in the forward face of the central panel of the 
forward firewall of the APU bay, in accordance with British 
Aerospace Service Bulletin S.B.26-35, Revision 1, dated August 30, 
1995.
    Note 2: Inspections accomplished prior to the effective date of 
this AD in accordance with British Aerospace Service Bulletin 
S.B.26-35, dated May 17, 1995, are considered acceptable for 
compliance with the applicable action specified in this amendment.
    (1) If no crack or evidence of gas leakage is found, repeat the 
inspection required by paragraph (a) of this AD thereafter at 
intervals not to exceed 200 landings, except as provided by 
paragraph (b) of this AD.
    (2) If any crack is found, but no evidence of gas leakage is 
detected, repeat the inspection required by paragraph (a) of this AD 
thereafter at daily intervals. Within 14 days after detecting any 
crack, accomplish the replacement specified in paragraph (c) of this 
AD.
    (3) If any crack is found and evidence of gas leakage is 
detected, prior to further flight, accomplish the replacement 
specified in paragraph (c) of this AD. Operation of the APU is 
prohibited (either when the aircraft is on the ground or in flight) 
until the replacement is accomplished.
    (b) Installation of a protective aluminum alloy shield on the 
vertical stiffener (left-hand) next to the exhaust aperture of the 
forward firewall of the APU bay (Modification HCM36179B), in 
accordance with British Aerospace Service Bulletin SB.26-36-36179B, 
dated June 22, 1995, increases the interval for repetitive 
inspections required by paragraph (a)(1) of this AD from 200 
landings to 400 landings.
    (c) Replacement of the central panel of the forward firewall of 
the APU bay with a new panel (Modification HCM36179A), in

[[Page 57177]]

accordance with British Aerospace Service Bulletin SB.26-35-36179A, 
dated August 4, 1995, constitutes terminating action for the 
requirements of this AD.
    (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, Standardization Branch, ANM-113, 
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, 
Standardization Branch, ANM-113.

    Note 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Standardization Branch, ANM-113.

    (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.
    (f) The actions shall be done in accordance with British 
Aerospace Service Bulletin S.B.26-35, Revision 1, dated August 30, 
1995; British Aerospace Service Bulletin SB.26-35-36179A, dated 
August 4, 1995; and British Aerospace Service Bulletin SB.26-36-
36179B, dated June 22, 1995. 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 
British Aerospace Holding, Inc., Avro International Aerospace 
Division, P.O. Box 16039, Dulles International Airport, Washington 
DC 20041-6039. 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 November 29, 1995.

    Issued in Renton, Washington, on November 6, 1995.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 95-27913 Filed 11-13-95; 8:45 am]
BILLING CODE 4910-13-U