DEPARTMENT OF TRANSPORTATION

FEDERAL AVIATION ADMINISTRATION

14 CFR Part 39

[Docket  No.  FAA-2010-0802;  Directorate  Identifier  2009-NM-256-AD] RIN
2120-AA64

AIRWORTHINESS DIRECTIVES; Learjet Inc. Model 45 Airplanes

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

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to supersede an existing airworthiness directive
(AD) that applies to certain Learjet Inc. Model 45 airplanes. The existing
AD currently requires, for  certain airplanes, repetitive inspections  for
chafing and other damage  of the case drain  tube from the hydraulic  pump
case  installed  on  the  left-hand  engine,  and  corrective  action   if
necessary. The existing  AD also requires,  for all airplanes,  repetitive
inspections  for  discrepancies  of  the  left  engine's  nacelle  tubing,
repetitive  inspections  for evidence  of  fluid leakage  within  the left
engine accessory  compartment, and  corrective actions  if necessary. This
proposed AD  would require  replacing the  left engine  fuel and hydraulic
tubing and installing a tubing support channel, which would terminate  the
repetitive inspections required in the existing AD. This proposed AD  also
removes airplanes from  the applicability. This  proposed AD results  from
reports  of  chafed  hydraulic  tubes  in  the  left-hand  engine.  We are
proposing this  AD to  detect and  correct chafed  hydraulic tubes  in the
left-hand engine  and consequent  hydraulic tube  failure and uncontrolled
loss of flammable fluid within the engine cowling, which could result in a
fire in the engine nacelle and loss of control of the airplane.

DATES: We must receive comments on this proposed AD by October 7, 2010.

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 W12-140,  1200 New  Jersey Avenue, SE.,
Washington, DC 20590,  between 9 a.m.  and 5 p.m.,  Monday through Friday,
except Federal holidays.

For service information identified  in this proposed AD,  contact Learjet,
Inc.,  One Learjet  Way, Wichita,  Kansas  67209-2942;  telephone: 316-946
-2000;  fax: 316-946-2220;  e-mail: ac.ict@aero.bombardier.com;  Internet:
http://www.bombardier.com. You may review copies of the referenced service
information at the FAA, Transport Airplane Directorate, 1601 Lind  Avenue,
SW.,  Renton,  Washington. For  information  on the  availability  of this
material at the FAA, call 425-227-1221.

EXAMINING THE AD DOCKET

You   may   examine   the   AD  docket   on   the   Internet   at  http://
www.regulations.gov;  or  in  person  at  the  Docket  Management Facility
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  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: James  Galstad, Aerospace  Engineer, Sys-
tems and Propulsion Branch, ACE-116W, FAA, Wichita Aircraft  Certification
Office,  1801  Airport  Road, Room  100,  Mid-Continent  Airport, Wichita,
Kansas 67209; telephone (316) 946-4135; fax (316) 946-4107.

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-2010-0802;   Directorate
Identifier 2009-NM-256-AD" at the beginning of your comments. We specific-
ally 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 because  of
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

On May 20, 2009, we issued AD 2009-11-13, amendment 39-15923 (74 FR 26288,
June  2, 2009),  for  certain  Learjet Inc.  Model 45  airplanes. That  AD
requires, for  certain airplanes,  repetitive inspections  for chafing and
other damage of the case drain tube from the hydraulic pump case installed
on the left-hand engine, and corrective action if necessary. This AD  also
requires, for all airplanes,  repetitive inspections for discrepancies  of
the left engine's nacelle  tubing, repetitive inspections for  evidence of
fluid leakage within the left engine accessory compartment, and corrective
actions if necessary.  That AD resulted  from reports of  chafed hydraulic
tubes in the  left-hand engine. We  issued that AD  to detect and  correct
chafed hydraulic tubes  in the left-hand  engine and consequent  hydraulic
tube failure and  uncontrolled loss of  flammable fluid within  the engine
cowling, which could result  in a fire in  the engine nacelle and  loss of
control of the airplane.

ACTIONS SINCE EXISTING AD WAS ISSUED

The preamble to AD 2009-11-13 specifies that we consider the  requirements
"interim action" and that the manufacturer is developing a modification to
address the  unsafe condition.  That AD  explains that  we might  consider
further  rulemaking  if  a   modification  is  developed,  approved,   and
available. The manufacturer now has developed such a modification, and  we
have determined that further rulemaking is indeed necessary; this proposed
AD follows from that determination.

CHANGES TO THE APPLICABILITY

The  applicability  of  AD  2009-11-13  includes  airplanes  having serial
numbers (S/N)  45-002 through  45-4000 inclusive.  This proposed  AD would
apply to  airplanes having  S/Ns 45-005  through 45-405  inclusive, and 45
-2001 through 45-2126 inclusive.  Airplanes having S/Ns 45-406  through 45
-2000 and 45-2127  through 45-4000, have  incorporated a design  change in
production that addresses the  identified unsafe condition, and  therefore
we removed these airplanes from the applicability. We also removed S/N  45
-002 because  it is  an experimental  airplane at  Learjet, and we removed
S/Ns 45-003 and 45-004 because they no longer exist.

RELEVANT SERVICE INFORMATION

We have reviewed Bombardier  Service Bulletins 40-71-04 (Model  45, serial
numbers 45-2001 through 45-2126) and 45-71-7 (Model 45, serial numbers  45
-005 through 45-405), both dated December 7, 2009. These service bulletins
describe  procedures  for replacing  the  left engine  fuel  and hydraulic
tubing and installing a tubing support channel, including doing a  general
visual inspection  for galling  of the  fuel supply  manifold  assembly, a
general visual inspection for minimum clearance between the firewall  fuel
supply tube  assembly and  the engine  firewall cutout,  a general  visual
inspection for minimum clearance between the lower nacelle hydraulic  tube
and hose  assemblies, a  general visual  inspection for  minimum clearance
between the lower  nacelle fuel tubes  and flexible hoses,  and corrective
actions if necessary.  The corrective actions  include replacing the  fuel
supply  manifold,   trimming  the   cutout  to   meet  minimum   clearance
specifications,   and   adjusting   parts   to   meet   minimum  clearance
specifications.  Modification  of  the  applicable  in-service   airplanes
eliminates the need for the existing requirements of AD 2009-11-13.

Bombardier Service  Bulletin 45-71-7,  dated December  7, 2009,  specifies
prior or concurrent accomplishment of Bombardier Service Bulletin 45-71-5,
dated  February  13,  2007, for  airplanes  having  serial numbers  45-005
through 45-319,  and 45-321.  Bombardier Service  Bulletin 40-71-04, dated
December  7,  2009,  specifies  prior  or  concurrent  accomplishment   of
Bombardier  Service  Bulletin  40-71-02,  dated  February  13,  2007,  for
airplanes  having  serial  numbers  45-2001  through  45-2069.  Bombardier
Service  Bulletins 45-71-5  and 40-71-02,  both dated  February 13,  2007,
describe the following procedures:

For certain airplanes, changing the routing and clamping configuration  of
the engine and alternator  wire harnesses, and the  starter/generator wire
bundles.

For certain airplanes, doing a detailed inspection for chafing of specific
hydraulic  tubes  located  within  the  left  engine  nacelle  between the
adjacent fuel tubes and to determine if there is interference between  the
fuel  tubing  and  hydraulic tubing,  securing  the  hydraulic tubes  with
additional clamps, inspecting adjacent  fuel tubing for interference  with
the  hydraulic tubing,  and corrective  actions  if  necessary. Corrective
actions include replacing chafed hydraulic tubes and replacing fuel  tubes
if interference is found.

For certain airplanes, replacing the left engine hydraulic pump case drain
tube.

For certain airplanes,  inspecting for clearance  between the left  engine
hydraulic tubing  with adjacent  tubing, structure,  and other components;
and replacing tubing if necessary.

For all airplanes, inspecting for clearance between the wire harnesses and
the  hydraulic and  fuel tubing  on the  left engines,  if necessary;  and
replacing tubing if necessary.

For certain airplanes, inspecting for clearance between the wire harnesses
and the hydraulic and fuel tubing on the right engines, if necessary;  and
replacing tubing if necessary.

FAA'S DETERMINATION AND REQUIREMENTS OF THE PROPOSED AD

We  have  evaluated all  pertinent  information and  identified  an unsafe
condition that is likely  to develop on other  airplanes of the same  type
design. For this reason, we  are proposing this AD, which  would supersede
AD 2009-11-13 and would retain  the requirements of the existing  AD until
the  modification   is  done.   This  proposed   AD  would   also  require
accomplishing the actions specified in Bombardier Service Bulletins  40-71
-04  and 45-71-7,  both dated  December 7,  2009; and  Bombardier  Service
Bulletins 40-71-02 and 45-71-5, both dated February 13, 2007.

COSTS OF COMPLIANCE

There are  about 530  airplanes of  the affected  design in  the worldwide
fleet. The following table provides the estimated costs for U.S. operators
to comply with this proposed AD.

                                          ESTIMATED COSTS
---------------------------------------------------------------------------------------------------
                                                                    NUMBER OF
                             AVERAGE                                  U.S.-
        ACTION        WORK  LABOR RATE   PARTS        COST PER     REGISTERED      FLEET COST
                      HOURS  PER HOUR                 AIRPLANE      AIRPLANES
---------------------------------------------------------------------------------------------------
Inspection (required
by AD 2009-11-13).      3      $85      $0......  $255 per inspect-    325    $82,875 per inspect-
                                                  ion..............           ion.
Modification (new
proposed action)...    20       85      Up to
                                        $14,740.  Up to $16,440....    358    Up to $5,885,520.
Concurrent Action..     4       85      $189....  $529.............    358    $189,382.
---------------------------------------------------------------------------------------------------

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 devel-
op on products identified in this rulemaking action.

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 Pro-
   cedures (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. 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, Incorporation by reference,
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 removing amendment 39-15923 (74 FR 26288,
   June 2, 2009) and adding the following new AD: