[Federal Register Volume 66, Number 32 (Thursday, February 15, 2001)]
[Rules and Regulations]
[Pages 10353-10355]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-3671]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2001-NM-11-AD; Amendment 39-12109; AD 2001-03-05]
RIN 2120-AA64


Airworthiness Directives; Learjet Model 45 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 Learjet Model 45 airplanes. This action 
requires revising the airplane flight manual (AFM) to prohibit flight 
into known icing conditions; inspecting the anti-ice manifold assembly 
for missing material, and performing corrective actions if necessary; 
replacing the anti-ice manifold assembly with a new assembly, which 
terminates the AFM revision requirement; and revising the Learjet 45 
maintenance program to incorporate additional inspections and 
maintenance practices for the anti-ice manifold assembly. This action 
is necessary to prevent metal fragments from breaking off the anti-ice 
manifold assembly due to fatigue, which could block a duct in the anti-
ice system and result in an unannunciated loss of ice protection. This 
action is intended to address the identified unsafe condition.

DATES: Effective February 20, 2001.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of February 20, 2001.
    Comments for inclusion in the Rules Docket must be received on or 
before April 16, 2001.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2001-NM-11-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays. Comments may be submitted via fax to (425) 227-1232. 
Comments may also be sent via the Internet using the following address: 
[email protected]. Comments sent via fax or the Internet must 
contain ``Docket No. 2001-NM-11-AD'' in the subject line and need not 
be submitted in triplicate. Comments sent via the Internet as attached 
electronic files must be formatted in Microsoft Word 97 for Windows or 
ASCII text.
    The service information referenced in this AD may be obtained from 
Learjet, Inc., One Learjet Way, Wichita, Kansas 67209-2942. This 
information may be examined at the FAA, Transport Airplane Directorate, 
1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Wichita 
Aircraft Certification Office, 1801 Airport Road, Room 100, Mid-
Continent Airport, Wichita, Kansas; or at the Office of the Federal 
Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Robert Busto, Aerospace Engineer, 
Systems and Propulsion Branch, ACE-116W, FAA, Wichita Aircraft 
Certification Office, 1801 Airport Road, Room 100, Mid-Continent 
Airport, Wichita, Kansas 67209; telephone (316) 946-4157; fax (316) 
946-4407.

SUPPLEMENTARY INFORMATION: The FAA has been advised that a Learjet 
Model 45 airplane recently experienced anti-ice system difficulties, 
generating a warning to the flight crew of an overheat condition of the 
horizontal stabilizer. Subsequent inspection revealed a fragment of 
metal from the system's bleed air manifold lodged in a section of the 
system's ducts. Inspection of other airplanes revealed fatigue cracking 
on the manifold splitter vanes.
    The anti-ice system on Model 45 airplanes incorporates a bleed 
airflow manifold to deliver air to the wing and horizontal stabilizer 
piccolo tubes. The manifold contains a set of internal splitter vanes, 
which recent inspections indicate are subject to premature fatigue 
cracking. The vanes are inadequately welded and subject to engine bleed 
airflow at high temperatures.

[[Page 10354]]

Consequently, the vanes are susceptible to fatigue caused by turbulent 
airflow traveling within the manifold. Metal pieces of the vanes may 
break off and become lodged in the anti-ice system downstream of the 
leading edge skin temperature sensors. This condition, if not 
corrected, could result in an unannunciated loss of ice protection.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Learjet 45 Temporary Flight 
Manual Change TFM 2000-16, dated January 8, 2001, which prohibits 
flight into icing conditions until the airplane's anti-icing system has 
been inspected and modified, as described below.
    The FAA has reviewed and approved Bombardier (Learjet 45) Alert 
Service Bulletin SB A45-30-2, dated December 18, 2000. The alert 
service bulletin describes procedures for a one-time inspection to 
detect missing pieces of the manifold assembly splitter. If fragments 
are missing from the splitter, the service bulletin recommends 
borescopic inspections to detect debris in the anti-ice tube assemblies 
within the wing and horizontal stabilizer anti-ice system, and removal 
of any splitter debris. The alert service bulletin also describes 
procedures for replacing the anti-ice manifold assembly with a new 
assembly.
    The manufacturer has issued Temporary Revisions (TR) 4-2, 5-2, and 
30-1, all dated January 2, 2001, for the Learjet 45 maintenance program 
manual. TR's 4-2 and 5-2 add borescopic inspections of the anti-ice 
manifold. TR 30-1 adds certain maintenance practices for the removal, 
installation, and inspection of the anti-ice manifold assembly. The 
TR's are to be incorporated into the Learjet maintenance program manual 
to revise the Learjet maintenance program.
    Accomplishment of the actions specified in the AFM revision, alert 
service bulletin, and maintenance program revisions is intended to 
adequately address the identified unsafe condition.

Explanation of the Requirements of the Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other airplanes of the same type design, this AD is 
being issued to prevent metal fragments of the splitter in the anti-ice 
system from breaking due to fatigue, which could block a duct in the 
anti-ice system and result in an unannunciated loss of ice protection. 
This AD requires accomplishment of the actions specified in the AFM 
revision, alert service bulletin, and maintenance program revisions 
described previously, except as discussed below.

Difference Between AD and Alert Service Bulletin

    This AD requires replacement of the anti-ice manifold assembly 
within 100 flight hours, whereas the alert service bulletin recommends 
replacement within 25 flight hours. At the time the alert service 
bulletin was developed, the shorter compliance time was recommended 
because of the urgency of the unsafe condition and the lack of 
available interim procedures developed to prohibit flight into known 
icing conditions until the manifold is replaced. In developing an 
appropriate compliance time for this AD, the FAA considered the safety 
implications as well as subsequent recommendations from the 
manufacturer. The FAA finds that 100 flight hours represents an 
appropriate interval of time allowable for affected airplanes to 
continue to operate without compromising safety.

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 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.
    Submit comments using the following format:
     Organize comments issue-by-issue. For example, discuss a 
request to change the compliance time and a request to change the 
service bulletin reference as two separate issues.
     For each issue, state what specific change to the AD is 
being requested.
     Include justification (e.g., reasons or data) for each 
request.
    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 2001-NM-11-AD.'' The postcard will be date stamped and 
returned to the commenter.

Regulatory Impact

    The regulations adopted herein will 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. Therefore, it 
is determined that this final rule does not have federalism 
implications under Executive Order 13132.
    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

[[Page 10355]]

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:

2001-03-05  Learjet: Amendment 39-12109. Docket 2001-NM-11-AD.
    Applicability: Model 45 airplanes, certificated in any category, 
serial numbers 45-002 through 45-004 inclusive, 45-006 through 45-
121 inclusive, and 45-124 through 45-129 inclusive.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
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 (e) 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 prevent metal fragments from breaking off the anti-ice 
manifold assembly due to fatigue, which could block a duct in the 
anti-ice system and result in an unannunciated loss of ice 
protection, accomplish the following:

Revision of Airplane Flight Manual (AFM)

    (a) Within 24 hours after the effective date, and until 
accomplishment of the requirements of paragraph (b) of this AD: 
Revise the Limitations section of the FAA-approved AFM by replacing 
the existing information in the TYPE OF OPERATION section with the 
following. This may be accomplished by inserting a copy of this AD 
into the AFM.
    ``This airplane is approved for:
     VFR (Visual)
     IFR (Instrument)
     Day
     Night
    Flight into icing conditions is prohibited. If icing conditions 
are encountered, comply with the Inadvertent Icing Encounter 
procedure, Section IV. Fly out of icing conditions as soon as 
possible.
    Icing conditions exist when outside air temperature (OAT) on the 
ground and for takeoff is 10 deg.C (50 deg.F) or below, or the 
static air temperature (SAT) in flight is 10 deg.C (50 deg.F) to 
-40 deg.C (-40 deg.F), and visible moisture in any form is present 
(such as clouds, fog with visibility of one mile or less, rain, 
snow, sleet, or ice crystals).
    Icing conditions also exist when the OAT on the ground and for 
takeoff is 10 deg.C (50 deg.F) or below when operating on ramps, 
taxiways, or runways where surface snow, ice, standing water, or 
slush may be ingested by the engines, or freeze on engines, 
nacelles, or engine sensor probes.''

    Note 2: Insertion into the AFM of a copy of Learjet 45 Temporary 
Flight Manual Change (TFM) TFM 2000-16, dated January 8, 2001, is 
also acceptable for compliance with the requirements of paragraph 
(a) of this AD.

Anti-Ice Manifold Assembly Replacement

    (b) Within 100 flight hours after the effective date of this AD: 
Perform a general visual inspection to detect missing pieces from 
the splitter vanes of the manifold assembly, perform all applicable 
corrective actions (including borescopic inspections to detect 
debris and removal of debris), and replace the anti-ice manifold 
assembly with a new assembly. Do the actions in accordance with 
Bombardier (Learjet 45) Alert Service Bulletin SB A45-30-2, dated 
December 18, 2000. When the manifold assembly has been replaced, the 
TFM required by paragraph (a) of this AD may be removed from the 
AFM.

    Note 3: For the purposes of this AD, a general visual inspection 
is defined as: ``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 under normally 
available lighting conditions such as daylight, hangar lighting, 
flashlight, or drop-light, 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.''

Maintenance Program Revision

    (c) Concurrently with the accomplishment of the requirements of 
paragraph (b) of this AD, revise the Learjet maintenance program by 
incorporating the procedures for removal, installation, and 
inspection of the anti-ice manifold assembly specified in Learjet 
Model 45 Maintenance Manual Temporary Revisions 4-2, 5-2, and 30-1; 
all dated January 2, 2001.
    (d) When the temporary revisions required by paragraph (c) of 
this AD have been incorporated into the general revisions of the 
maintenance program, the general revisions may be incorporated into 
the maintenance program, provided that the information contained in 
the general revisions is identical to that specified in the 
temporary revisions.

Alternative Methods of Compliance

    (e) 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, Wichita Aircraft Certification 
Office (ACO), FAA. Operators shall submit their requests through an 
appropriate FAA Principal Maintenance Inspector, who may add 
comments and then send it to the Manager, Wichita ACO.

    Note 4: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Wichita ACO.

Special Flight Permits

    (f) 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, provided the 
airplane is restricted from flight into known icing conditions.

Incorporation by Reference

    (g) Except as required by paragraph (a) of this AD: The actions 
shall be done in accordance with Bombardier (Learjet 45) Alert 
Service Bulletin SB A45-30-2, dated December 18, 2000; Learjet 45 
Maintenance Manual Temporary Revision 4-2, dated January 2, 2001; 
Learjet 45 Maintenance Manual Temporary Revision 5-2, dated January 
2, 2001; and Learjet 45 Maintenance Manual Temporary Revision 30-1, 
dated January 2, 2001; as applicable. The actions required by 
paragraph (a) of this AD may also be done in accordance with Learjet 
45 Temporary Flight Manual Change TFM 2000-16, dated January 8, 
2001. 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 Learjet, Inc., One Learjet Way, 
Wichita, Kansas 67209-2942. Copies may be inspected at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington; or at the FAA, Wichita Aircraft Certification Office, 
1801 Airport Road, Room 100, Mid-Continent Airport, Wichita, Kansas; 
or at the Office of the Federal Register, 800 North Capitol Street, 
NW., suite 700, Washington, DC.

Effective Date

    (h) This amendment becomes effective on February 20, 2001.

    Issued in Renton, Washington, on February 7, 2001.
Vi L. Lipski,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 01-3671 Filed 2-14-01; 8:45 am]
BILLING CODE 4910-13-U