DEPARTMENT OF TRANSPORTATION

FEDERAL AVIATION ADMINISTRATION

14 CFR Part 39

[Docket  No.  FAA-2008-0178;  Directorate  Identifier  2007-NM-366-AD] RIN
2120-AA64

AIRWORTHINESS DIRECTIVES; Bombardier Model DHC-8-400 Series Airplanes

AGENCY: Federal Aviation Administration (FAA), Department of  Transportat-
ion (DOT).

ACTION: Supplemental  notice of  proposed rulemaking  (NPRM); reopening of
comment period.

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SUMMARY: We are  revising an earlier  NPRM for the  products listed above.
This action revises the earlier NPRM by expanding the scope. This proposed
AD  results  from mandatory  continuing  airworthiness information  (MCAI)
originated by  an aviation  authority of  another country  to identify and
correct an unsafe condition on an aviation product. The MCAI describes the
unsafe condition as:

Bombardier Aerospace has completed a system safety review of the  aircraft
fuel system against fuel tank safety standards * * *.

[A]ssessment showed  that supplemental  maintenance tasks  [inspections of
various fuel system  components such as  shields, harnesses, sleeves,  and
sealant] are  required to  prevent potential  ignition sources  inside the
fuel system, which could result in a fuel tank explosion. * * *

The proposed  AD would  require actions  that are  intended to address the
unsafe condition described in the MCAI.

DATES: We must receive comments on this proposed AD by May 21, 2008.

ADDRESSES: You may send comments by any of the following methods:

Federal eRulemaking Portal:  Go to http://www.regulations.gov.  Follow the
instructions for submitting comments.

Fax: (202) 493-2251.

Mail: U.S.  Department of  Transportation, Docket  Operations, M-30,  West
Building  Ground  Floor,  Room  W12-140,  1200  New  Jersey  Avenue,  SE.,
Washington, DC 20590.

Hand Delivery: U.S. Department of Transportation, Docket Operations, M-30,
West Building  Ground Floor,  Room W12-40,  1200 New  Jersey Avenue,  SE.,
Washington, DC, between 9 a.m.  and 5 p.m., Monday through  Friday, except
Federal holidays.

EXAMINING THE AD DOCKET

You   may   examine   the   AD  docket   on   the   Internet   at  http://
www.regulations.gov; or in person at the Docket Operations office  between
9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The  AD
docket contains this proposed AD, the regulatory evaluation, any  comments
received,  and  other  information.  The  street  address  for  the Docket
Operations office (telephone (800) 647- 5527) is in the ADDRESSES section.
Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT: Rocco Viselli,  Aerospace  Engineer, Air-
frame and Propulsion Branch, ANE-171, FAA, New York Aircraft Certification
Office,  1600  Stewart  Avenue,  Suite  410,  Westbury,  New  York  11590;
telephone (516) 228-7331; fax (516) 794-5531.

SUPPLEMENTARY INFORMATION:

COMMENTS INVITED

We invite you to send any written relevant data, views, or arguments about
this  proposed AD.  Send your  comments to  an address  listed under   the
ADDRESSES  section.   Include  "Docket   No.  FAA-2008-0178;   Directorate
Identifier  2007-NM-366-AD"  at  the   beginning  of  your  comments.   We
specifically  invite  comments   on  the  overall   regulatory,  economic,
environmental, and energy  aspects of this  proposed AD. We  will consider
all comments received by the closing  date and may amend this proposed  AD
based on those comments.

We  will  post  all  comments  we  receive,  without  change,  to  http://
www.regulations.gov, including  any personal  information you  provide. We
will also  post a  report summarizing  each substantive  verbal contact we
receive about this proposed AD.

DISCUSSION

We proposed to amend 14 CFR part 39 with an earlier NPRM for the specified
products, which was published in the Federal Register on February 19, 2008
(73 FR 9053).  That earlier NPRM  proposed to require  actions intended to
address the unsafe condition for the products listed above.

Since that earlier  NPRM was issued,  we have determined  that the initial
compliance times for doing the tasks specified in paragraph (f)(1) of  the
earlier NPRM  must be  reduced. That  earlier NPRM  resulted from Canadian
Airworthiness Directive CF-2007-33, dated  December 17, 2007 (referred  to
after this as "the MCAI").

The MCAI does not provide an initial compliance time for doing the  tasks.
In the earlier NPRM, we  proposed an initial compliance time  that started
from the effective date of the AD; or the date of issuance of the original
Canadian standard airworthiness certificate or the date of issuance of the
original Canadian  export certificate  of airworthiness;  whichever occurs
later. Although unstated in the  MCAI, we have determined that  the intent
of the MCAI is for the  initial compliance time to start from  the initial
delivery date of  the airplane in  order to address  the identified unsafe
condition in a timely manner. We have also revised the initial  compliance
times for clarity by providing a threshold and grace period for the tasks.
We have revised paragraphs  (f)(1)(i) and (f)(1)(ii) of  this supplemental
NPRM accordingly. You may obtain further information by examining the MCAI
in the AD docket.

FAA'S DETERMINATION AND REQUIREMENTS OF THIS PROPOSED AD

This  product  has been  approved  by the  aviation  authority of  another
country, and is approved for  operation in the United States.  Pursuant to
our bilateral agreement with the  State of Design Authority, we  have been
notified  of  the  unsafe  condition described  in  the  MCAI  and service
information  referenced  above.  We  are  proposing  this  AD  because  we
evaluated all  pertinent information  and determined  an unsafe  condition
exists and is  likely to exist  or develop on  other products of  the same
type design.

Certain changes described above expand the scope of the earlier NPRM. As a
result, we  have determined  that it  is necessary  to reopen  the comment
period to provide additional opportunity for the public to comment on this
proposed AD.

DIFFERENCES BETWEEN THIS AD AND THE MCAI OR SERVICE INFORMATION

We have reviewed the MCAI and related service information and, in general,
agree with their substance.  But we might have  found it necessary to  use
different words from those in the MCAI to ensure the AD is clear for  U.S.
operators and is enforceable. In making these changes, we do not intend to
differ substantively from the information provided in the MCAI and related
service information.

We might also have required different actions in this AD from those in the
MCAI  in  order to  follow  our FAA  policies.  Any such  differences  are
highlighted in a Note within the AD.

COSTS OF COMPLIANCE

Based on the service information, we estimate that this proposed AD  would
affect about 38 products of U.S. registry. We also estimate that it  would
take about 1 work-hour per  product to comply with the  basic requirements
of this proposed AD. The average labor rate is $80 per work-hour. Based on
these figures, we estimate the cost  of the proposed AD on U.S.  operators
to be $3,040, or $80 per product.

AUTHORITY FOR THIS RULEMAKING

Title 49 of the United States Code specifies the FAA's authority to  issue
rules on aviation safety. Subtitle I, section 106, describes the authority
of the FAA Administrator. "Subtitle VII: Aviation Programs," describes  in
more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in  "Subtitle
VII, Part A, Subpart III, Section 44701: General requirements." Under that
section, Congress  charges the  FAA with  promoting safe  flight of  civil
aircraft  in  air  commerce  by  prescribing  regulations  for  practices,
methods, and procedures  the Administrator finds  necessary for safety  in
air  commerce.  This regulation  is  within the  scope  of that  authority
because  it addresses  an unsafe  condition that  is likely  to exist   or
develop on products identified in this rulemaking action.

REGULATORY FINDINGS

We 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 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. 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 and placed it in the AD docket.

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 AD: