[Federal Register Volume 65, Number 12 (Wednesday, January 19, 2000)]
[Rules and Regulations]
[Pages 2844-2861]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-951]


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DEPARTMENT OF TRANSPORTATION

 Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-CE-67-AD; Amendment 39-11514; AD 2000-01-16]
RIN 2120-AA64


Airworthiness Directives; Cessna Aircraft Company 300 and 400 
Series Airplanes

AGENCY:  Federal Aviation Administration, DOT.

ACTION:  Final rule; request for comments.

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[[Page 2845]]

SUMMARY:  This amendment supersedes Airworthiness Directive (AD) 75-23-
08 R5, which currently requires repetitively inspecting and replacing 
or repairing the exhaust system on certain Cessna Aircraft Company 
(Cessna) 300 and 400 series airplanes. The requirements of this AD 
replace the inspections and replacements that are required by AD 75-23-
08 R5 with inspections and replacements containing new simplified 
procedures for all 300 and 400 series airplanes (models affected by the 
current AD plus additional models). This AD also revises the inspection 
intervals and requires replacing certain unserviceable parts and 
removing the exhaust system for a detailed inspection. This AD is the 
result of numerous incidents and accidents relating to the exhaust 
systems on Cessna 300 and 400 series airplanes dating from the middle 
1970's to the present, including six incidents since issuance of AD 75-
23-08 R5 where exhaust problems were cited. The actions specified by 
this AD are intended to detect and correct cracks and corrosion in the 
exhaust system, which could result in exhaust system failure and a 
possible uncontrollable in-flight fire with pilot and/or passenger 
injury.

DATES:  Effective February 15, 2000.
    Comments for inclusion in the Rules Docket must be received on or 
before April 14, 2000.

ADDRESSES:  Information that relates to this AD may be examined at the 
Federal Aviation Administration (FAA), Central Region, Office of the 
Regional Counsel, Attention: Rules Docket No. 97-CE-67-AD, 901 Locust, 
Room 506, Kansas City, Missouri 64106.

FOR FURTHER INFORMATION CONTACT:  Paul O. Pendleton, Aerospace 
Engineer, FAA, Wichita Aircraft Certification Office, 1801 Airport 
Road, Room 100, Wichita, Kansas 67209; telephone: (316) 946-4143; 
facsimile: (316) 946-4407.

SUPPLEMENTARY INFORMATION:

Events Leading to the Issuance of This AD

    A proposal to amend part 39 of the Federal Aviation Regulations (14 
CFR part 39) to include an AD that would apply to certain Cessna 300 
and 400 series airplanes was published in the Federal Register as a 
notice of proposed rulemaking (NPRM) on July 6, 1999 (64 FR 36307). The 
NPRM proposed to supersede AD 75-23-08 R5, Amendment 39-5451, with a 
new AD. AD 75-23-08 R5 currently requires repetitively inspecting, 
using visual methods, the exhaust system on certain Cessna 300 and 400 
series airplanes; and repairing or replacing any unserviceable parts. 
The actions specified in the NPRM proposed to replace the inspections 
and replacements that are required by AD 75-23-08 R5 with inspections 
and replacements containing new simplified procedures for all 300 and 
400 series airplanes (models affected by the current AD plus additional 
models). The NPRM also proposed to revise the inspection intervals and 
proposed to require replacing certain unserviceable parts and removing 
the exhaust system for a detailed inspection. Other provisions included 
in the NPRM, as currently written, are:

--Prohibiting patch-type repairs; and
--Removing the exhaust system and sending it to a designated facility 
for metallic identification, airworthiness determinations, and repair 
or replacement of any unserviceable parts.

    The NPRM was the result of numerous incidents and accidents 
relating to the exhaust systems on Cessna 300 and 400 series airplanes 
dating from the middle 1970's to the present, including six incidents 
since issuance of AD 75-23-08 R5 where exhaust problems were cited.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Introduction to the Comment Disposition

    The FAA received over 350 comments on the NPRM. Many of the 
comments indicate that some kind of action needs to be taken regarding 
the ongoing problems with the exhaust systems on Cessna 300 and 400 
series airplanes. Many commenters present detailed suggestions for 
alternatives to the proposed actions included in the NPRM. The FAA 
believes that, for the most part, these suggestions and alternatives 
have merit and the final rule reflects many of these suggestions and 
alternatives.
    The FAA will continue to make available information that relates to 
the exhaust system problems on the Cessna 300 and 400 series airplanes. 
However, the FAA does not believe that this advisory information alone 
will alleviate and eliminate the unsafe condition of the exhaust system 
problems on the Cessna 300 and 400 series airplanes. The FAA also does 
not believe that continuing to only mandate the actions of AD 75-23-08 
R5 will provide the safety level that is necessary for the affected 
airplanes.
    The NPRM proposed to require an inspection to determine the type of 
material (Inconel or stainless steel) and the condition of the exhaust 
system. Of note is that the minimum wall thickness criteria was 
established as an attempt to remove from service those systems that 
were over 30 years old. However, the FAA did not account for those 
unused or recently installed exhaust systems that were manufactured 
over 30 years ago and either are currently held as or until recently 
were held as spares. The final rule accounts for this by requiring an 
inspection of the tailpipes 5 years after installation of an unused or 
overhauled exhaust system or within 100 hours time-in-service (TIS) 
after the effective date of the AD (the prevalent one being that which 
occurs later).
    In addition, the FAA has found that Cessna has not manufactured any 
exhaust assemblies that are 100-percent Inconel material. Much of the 
confusion raised on and in opposition to the proposal stems from 
sending the exhaust system to a facility to get a determination on 
whether the system was a stainless steel or Inconel exhaust system. The 
different compliance times for the different systems adds to the 
confusion and opposition. The FAA has revised the proposal to include 
the same compliance times for all airplanes regardless of the exhaust 
system material and to remove the proposed requirement of sending the 
exhaust system to a specific facility for a material determination.
    The final rule reflects other changes made based on the FAA's 
analysis of the comments received and all other information related to 
the exhaust systems on the Cessna 300 and 400 series airplanes. All 
changes, like the ones referenced above, will alleviate the burden upon 
the public as proposed in the NPRM while still providing the necessary 
safety level intended by this AD.
    The following paragraphs present the comments received with the 
FAA's response and changes to the AD, as applicable:
    Comment Issue No. 1: Include Alternative Proposals
    Numerous commenters recommend that the FAA incorporate the 
provisions of proposals that the Cessna Pilot's Association and Twin 
Cessna Flyer submitted. The commenters state that there is a need for 
the AD, and that these proposals provide a viable safety alternative.
    The FAA evaluated both of these proposals, determined that many of 
these comments have merit, and has made changes to the final rule. 
Among

[[Page 2846]]

the items in the proposals that the FAA incorporated into the final 
rule include:

--Eliminating the check of the system for wall thickness;
--Having the same compliance schedule for all airplanes regardless of 
whether the exhaust systems are made of Inconel or stainless steel; and
--Eliminating the proposed requirement of removing the exhaust system 
and sending it to a specific facility for a material determination.

Comment Issue No. 2: The Existing AD is Sufficient

    Many commenters state that the current actions of AD 75-23-08 R5 
are sufficient to meet the necessary safety level intended by this AD 
for the exhaust systems of the Cessna 300 and 400 series airplanes. 
Several commenters state that, if AD 75-23-08 R5 was complied with in a 
correct and timely matter, the incidents referenced in the NPRM may not 
have happened. Some commenters believe that changing the inspection 
requirements from that already required by AD 75-23-08 R5 will cause 
confusion and add unnecessary costs to the inspections. One other 
commenter suggests that the FAA issue a Special Airworthiness 
Information Bulletin (SAIB) to address the requirements of the AD.
    The FAA does not concur that AD 75-23-08 R5 is sufficient. Analysis 
of the incidents and accidents pertaining to the exhaust systems on the 
Cessna 300 and 400 series airplanes that have occurred since the 
issuance of AD 75-23-08 R5 reveals the need to require different 
inspection requirements to meet the conditions known today. The FAA 
believes that the changes made to the final rule will also make the 
inspections easier to accomplish and will allow them to be accomplished 
to coincide with regularly scheduled maintenance.
    The FAA does not concur that an SAIB should be issued instead of an 
AD. An SAIB is an ``information only'' document and has no regulatory 
requirement; therefore, it is not mandatory. The only vehicle the FAA 
has of assuring that certain actions are complied with is through the 
issuance of an AD. No changes have been made to this AD as a result of 
this comment.

Comment Issue No. 3: Cost Impact

    Many commenters state that the FAA's estimate of the cost impact 
upon U.S. owners/operators of the affected airplanes is incorrect. Some 
also believe that the FAA should have completed the Regulatory 
Flexibility Analysis before issuing the NPRM. Among the specific cost 
issues that were identified is the FAA's failure to account for the 
revenue lost due to airplane downtime and the fact that the cost of the 
proposed AD would affect the airplanes' value and make them 
unaffordable.
    The FAA does not concur that the estimate of the cost impact upon 
U.S. owners/operators of the affected airplanes is incorrect. The FAA 
has no way of determining the number or extent of repairs and 
replacements that would be necessary based on the inspections proposed 
in the NPRM. Therefore, the FAA can only account for the costs of the 
inspections. The FAA believes it is the owners'/operators' 
responsibility to repair or replace parts when found damaged, 
regardless of whether the action is required by AD.
    The FAA does not concur that it was necessary to complete the 
Regulatory Flexibility Analysis before issuing the NPRM. Having this 
analysis completed prior to issuing the NPRM is preferred; however, the 
FAA did not believe it could wait to initiate rulemaking on this 
subject. The FAA has until 180 days after issuance of the final rule AD 
action to have the completed Regulatory Flexibility Analysis in the 
docket file.
    The FAA concurs that airplane downtime is not accounted for in the 
estimate of the cost impact. The FAA has no way of determining the 
operational characteristics of each owner/operator of the affected 
airplanes. Therefore, estimating the lost expenses due to the affected 
airplanes being out of service is not possible. Even if this were 
possible, the safety aspects of the proposed rule would outweigh the 
potential lost revenue due to airplane downtime.

Comment Issue No. 4: V-Band Clamp Replacements

    Several commenters state that the proposed V-band replacement 
requirements are inconsistent with what is currently required by AD 75-
23-08 R5 and would be difficult to accomplish. The commenters request 
clarification on the FAA's intent.
    The FAA's intent was to maintain the V-band replacements from AD 
75-23-08 R5. Based on this and after evaluating all the comments and 
information on this subject, the FAA has revised the proposal to only 
require replacement of the multi-band V-clamps at 500-hour TIS 
intervals. Inspection of the other V-band clamps is part of the exhaust 
system inspections required by this AD.

Comment Issue No. 5: Concerns With the Slip Joint Requirement

    Many commenters express concerns regarding the requirements of the 
slip joints, specifically either require (1) replacement of the old 
style joints; (2) lubrication of the slip joints; or (3) a change to 
the compliance time of the slip joint removal and inspection 
requirements. The majority of these commenters state that removing the 
slip joints would cause more damage than would be caused during normal 
usage.
    The FAA concurs that removing the slip joints too frequently could 
cause damage. The FAA has determined that the necessary safety level 
intended by this AD will be reached by requiring the slip joints to be 
annually inspected for freedom of movement without removing the slip 
joints from the nacelle. The slip joints will be removed for inspection 
at each 2,500-hour TIS inspection. The FAA believes that the 
inspections will reveal deterioration of the older style joints and 
require replacement.

Comment Issue No. 6: Stainless Steel Versus Inconel

    Many commenters state that the different compliance times for 
stainless steel exhaust systems and Inconel exhaust systems need 
clarification. These commenters request that the FAA define an ``all 
Inconel system'' since all exhaust systems consist of some stainless 
steel parts. Several commenters state that having different compliance 
times for different exhaust systems is confusing, and request that all 
exhaust systems be treated equally.
    The FAA concurs that no exhaust system is made exclusively of 
Inconel alloy and that the current compliance times could cause 
confusion among those airplane owners/operators and mechanics trying to 
accomplish the AD. The FAA has revised the AD to provide compliance 
times that are applicable to all exhaust systems. This eliminates the 
need to send the exhaust system to an authorized facility for material 
determination. The FAA has revised the compliance times to coincide 
with regularly scheduled maintenance.

Comment Issue No. 7: Facilities and Personnel

    Numerous commenters express concern about the FAA's requirement of 
the qualifications of the personnel to accomplish the work and what 
facilities must be used to accomplish portions of this AD. These 
concerns include:

--The three approved facilities would not be able to accomplish the 
parts evaluation and inspections on these parts evaluations and 
inspections on all of the affected airplanes in a timely manner;
--Foreign airworthiness authorities that adopt an FAA AD verbatim for 
their

[[Page 2847]]

countries would then require all airplanes certificated for operation 
in those countries to have the parts evaluations and inspections 
accomplished at one of the three U.S. facilities; and
--Maintenance personnel in foreign countries with equivalent ratings to 
those specified in the proposed AD would not be able to accomplish the 
work under the current wording of this AD.

    The FAA has evaluated these concerns and has changed this AD to 
include:
--Clarifying who can accomplish what actions in this AD, including a 
clause of ``or for non U.S. registered airplanes: the state of 
registry's equivalent facility in accordance with their applicable 
procedure'';
--Consolidating the actions of all airplanes into one compliance 
program so the need to send to one of the three facilities to determine 
the material used for the exhaust system and the condition is no longer 
necessary; and
--Changing the facilities required to do the repair work to any FAA-
approved exhaust repair facility.

Comment Issue No. 8: Compliance Times

    Many commenters request changes to the proposed compliance times. 
The main reason for these proposed changes is to time the actions 
specified in the NPRM to coincide with regular maintenance intervals, 
i.e., engine overhaul and annual inspections. Several commenters also 
request a 10-percent adjustment on inspection compliance times.
    The FAA has re-evaluated the compliance times and has changed the 
final rule to add provisions that would make the actions coincide with 
regularly scheduled maintenance activities. Having one compliance time 
for all airplanes, regardless of the exhaust system type (Inconel or 
stainless steel) allowed this to be accomplished. The FAA is also 
allowing the 10-percent adjustment allowance to allow the actions to be 
accomplished with other scheduled maintenance. All of these adjustments 
actually reflect a reduction in the burden upon U.S. operators over 
that proposed in the NPRM.

Comment Issue No. 9: Cessna Service Bulletins

    A few commenters suggest that the FAA issue an AD that mandates the 
Cessna service bulletins that relate to this subject instead of what is 
proposed in the NPRM. These commenters state that the actions specified 
in the service bulletins are adequate to address the unsafe condition.
    The FAA does not concur. The Cessna service bulletins were not 
available at the time of issuance of the NPRM. Cessna has issued the 
following service bulletins since the NPRM:
--Service Bulletin (SB) MEB99-8, SB MEB99-11, SB MEB99-14, and SB 
MEB99-15, all dated August 2, 1999. These service bulletins specify and 
include procedures for replacing the crossfeed fuel lines with 
stainless steel cross feed lines. Each service bulletin applies to 
various Cessna airplane models.
--SB MEB99-6, SB MEB99-9, and SB MEB99-12, all dated August 2, 1999. 
These service bulletins specify and include procedures for installing 
access panels to help with exhaust system inspections. Each service 
bulletin applies to various Cessna airplane models.
--SB MEB99-7, SB MEB99-10, and SB MEB99-13, all dated August 2, 1999. 
These service bulletins specify and include procedures for installing 
stainless steel engine beam covers and inspecting the engine beams. 
Each service bulletin applies to various Cessna airplane models.

    The FAA has determined that the best course of action is 
accomplishing that specified in the final rule (the actions of the NPRM 
as modified based on the comments received) instead of incorporating 
the Cessna service bulletins. Reasons include:

--The service bulletins focus more on the protection of the affected 
airplanes once the exhaust system has failed; and
--The service bulletins do not address the turbocharger installation on 
the firewall, including the engine exhaust pipes and the tail pipe. The 
leakage of exhaust gases in this area is considered the unsafe 
condition.

    The FAA does believe that installing the access panels as specified 
in the Cessna service bulletins will aid in the repetitive exhaust 
system inspections. The FAA has added a note to the AD to include this 
access panel information. No other changes to the final rule have been 
made as a result of these comments.

Comment Issue No. 10: Supplemental Type Certificates and Parts 
Manufacturer Approvals

    Two commenters suggest that airplanes that have been modified 
through the incorporation of Riley Aviation supplemental type 
certificates (STC's) not be subject to this AD, or that the FAA wait 
for the Riley Aviation solution to the unsafe condition for those 
affected airplanes. In addition, two commenters request explanation 
related to installation requirements of STC and parts manufacturer 
approval (PMA) parts as they relate to the exhaust systems on Cessna 
300 and 400 series airplanes.
    The FAA does not concur. The Riley Aviation modification through 
STC's utilizes design parts that are equivalent to the original type 
design. The FAA has determined that exhaust systems that have been 
modified through Riley Aviation STC's are subject to the unsafe 
condition addressed by this AD. Although Riley Aviation may indeed 
develop actions to address this unsafe condition, the FAA cannot delay 
AD action waiting for actions that have yet to be developed or 
approved. However, any owners/operators of the affected airplanes can 
present data to show that their exhaust systems utilize design parts 
that should not be subject to this AD by submitting an alternative 
method of compliance request in accordance with the procedures 
specified in this AD. The FAA will evaluate the merits of each request 
and either grant or deny the alternative method of compliance. No 
changes have been made to this AD as a result of these comments.

Comment Issue No. 11: Maintenance and Pilot Training

    Numerous commenters state that part of the safety problem comes 
from inadequate maintenance and the need for pilot training. These 
commenters suggest that additional pilot training and mandated 
preflight checks could alleviate the unsafe condition. Many commenters 
feel that the FAA is arbitrarily punishing the majority of owners/
operators of the affected airplanes because of the inadequate 
maintenance practices of a few operators. These commenters state that 
the existing maintenance requirements are adequate to provide the 
necessary safety level intended by this AD, and that if the FAA 
enforced the existing rules there would not be any problems.
    The FAA concurs that pilot training and preflight checks could 
reduce the potential for the unsafe condition from occurring. However, 
the FAA has determined that the unsafe condition is in part the result 
of maintenance practices that are not adequate to provide the necessary 
safety level intended by this AD. The FAA has determined that the 
condition should be addressed through inspections and exhaust system 
repair and parts replacement. No changes to this AD

[[Page 2848]]

have been made as a result of these comments.

Comment Issue No. 12: Part 135 Operations

    Five commenters suggest that the FAA exempt those airplanes that 
are regulated by a maintenance program such as that required for 
airplanes operating in accordance with part 135 of the Federal Aviation 
Regulations (14 CFR part 135). The commenters state that such 
maintenance programs already require the actions specified in the NPRM.
    The FAA partially concurs. The FAA agrees that certain actions may 
already be accomplished by maintenance programs required under 14 CFR 
part 135. A note has been added to this AD that specifies that the 
owners/operators of those airplanes operating under 14 CFR part 135 may 
have already had the actions of this AD incorporated, and appropriate 
``unless already accomplished'' credit could be taken for the 
applicable portion of this AD. The FAA cannot exempt these airplanes 
from this AD because operators are not obligated to fly predominately 
in part 135 operations and could operate under part 91 of the Federal 
Aviation Regulations (14 CFR part 91).

Comment Issue No. 13: Leak Testing for Cracks

    Several commenters suggest that the FAA allow a leak test to detect 
cracked exhaust system parts. The FAA presumes that these commenters 
would prefer the leak test over the currently proposed pressure tests.
    The FAA has determined that the pressure checks required in this AD 
will detect cracks, pinholes, or other damage, and that leak testing is 
not required. Owners/operators of the affected airplanes can submit an 
alternative method of compliance to the FAA that contains appropriate 
data and information to show that an equivalent level of safety to this 
AD would be obtained through leak testing. No changes to this AD have 
been made as a result of these comments.

Comment Issue No. 14: Firewall, Bulkhead, Engine Beams, and Fuel 
Lines

    Many commenters request modification or explanation concerning the 
need to inspect the firewall, bulkheads, engine beams, and fuel lines. 
The commenters suggest that the FAA only require inspection of the fuel 
lines and areas behind the firewall to be inspected if damage has 
occurred or work has been done in the firewall area. These commenters 
also request the FAA define the acceptable limits of corrosion in the 
engine beams and associated structure.
    The FAA maintains that the firewalls, canted bulkheads, and engine 
beams should be inspected and has written the compliance time of these 
inspections to allow them to be accomplished during the regular 
maintenance schedule that coincides with other inspections or repairs. 
The FAA concurs that the fuel lines should only be inspected upon 
condition, and this AD has beenwill be changed to only require the 
inspections if there is evidence of past damage to the firewalls, 
canted bulkheads, and engine beams. The fuel lines will be replaced if 
damage is found.

Comment No. 15: Wall Thickness

    Numerous commenters state that the wall thickness inspection is 
unworkable due to the thickness limit of .025 inches. Some of these 
commenters are concerned that some new parts would not pass the 
thickness requirement. The commenters recommend specific thickness of 
.049 inches for the ``wye'' and .035 inches for the tailpipe.
    After further analysis of the wall thickness inspection 
requirement, the FAA has determined that overly thin parts will be 
detected and corrected in the general airworthiness inspections 
required on the ``wye'' and tailpipe. Therefore, the FAA has deleted 
this requirement from this AD.

Comment Issue No. 16: Install an Insulation Blanket

    Five commenters suggest installing an insulation blanket (such as 
Kevlar) as an alternative to the actions specified in the NPRM. Another 
commenter states that installing this insulation blanket would 
complicate inspections.
    The FAA concurs that the addition of an insulation blanket could 
relieve some of the potential difficulties, although it would only 
alleviate the condition and would not provide the necessary safety 
level intended by this AD. Also, the FAA concurs that installing an 
insulation blanket could make already required inspections difficult to 
accomplish. Based on this, the FAA has determined that the installation 
of an insulation blanket will not meet the necessary safety level 
intended by this AD and the FAA has not incorporated this suggestion. 
No changes have been made to this AD as a result of these comments.

Comment Issue No. 17: Inadequate Maintenance Practices

    Several commenters state that the NPRM lacks test and inspection 
procedures. These commenters suggest specific changes or additions to 
these inspection methods, including:
    1. Make a video tape of the inspection process;
    2. Require an inspection for exhaust stains;
    3. Specify wear rates and leakage rates on the pressure tests;
    4. Include information about the confusion concerning the various 
types of slip joints utilized on the affected airplanes;
    5. Clarify what is meant by an exhaust repair station;
    6. Require only visual inspections;
    7. Clarify the pressure check requirements because this check is 
too judgmental, and that an unacceptable leak is not identified;
    8. Add a ``tap test'' to check parts; and
    9. Clarify and mandate assembly and torquing sequence requirements.
    The FAA concurs with some of the recommendations, as follows:
    1. The FAA believes a video could be a great visual aid in 
illustrating the inspection, but the FAA has determined that it could 
only be an informational aid and cannot be mandated by AD action. No 
changes have been made to this AD as a result of this comment;
    2. The FAA does not consider the exhaust stains to be a reliable 
indication of whether exhaust problems exist. Stains could be a sign to 
look further, but not a true indicator. No changes have been made to 
this AD as a result of this comment;
    3. As specified in Comment Issue No. 13, the FAA has determined 
that the pressure checks required in this AD will detect cracks, 
pinholes, or other damage, and that leak testing is not required. 
Owners/operators of the affected airplanes can submit an alternative 
method of compliance to the FAA that contains appropriate data and 
information to show that an equivalent level of safety to this AD would 
be obtained with this method. No changes have been made to this AD as a 
result of this comment;
    4. The FAA has revised this AD to only require removal of the slip 
joints during the 2,500-hour TIS engine overhaul inspection;
    5. The FAA has revised the AD to specify an FAA-approved exhaust 
system repair facility. This means a facility that has FAA approval to 
work on exhaust systems;
    6. Due to the extent and location of the damage found on the Cessna 
300 and 400 series airplanes, the FAA has determined that visual 
inspections will not provide the necessary safety level intended by 
this AD. No changes have been made to this AD as a result of this 
comment;

[[Page 2849]]

    7. The pressure check is intended to identify leakage that is 
considered to be excessive or in locations where it will help identify 
crack, pinholes, or damage. Any application of the pressure test will 
be judgmental; however, many owners/operators have already accomplished 
this test on the affected airplanes with success so the FAA has 
determined that authorized or appropriate maintenance personnel can 
accomplish the procedure repeatedly with acceptable results. No changes 
have been made to this AD as a result of this comment;
    8. The FAA concurs that a ``tap test'' may be helpful in 
identifying damaged parts, however, the FAA has determined that this 
procedure is not definitive and any suspect part should be further 
investigated. No changes have been made to this AD as a result of this 
comment; and
    9. After re-examining the procedures and information in the 
maintenance manuals and service information for the affected airplanes, 
the FAA has determined that the assembly and torquing techniques are 
acceptable to meet the necessary safety level intended by this AD. No 
changes have been made to this AD as a result of this comment.

Comment Issue No. 18: Incorporate a Design Change

    Many commenters recommend that the FAA incorporate a design change 
to the exhaust systems rather than requiring repetitive inspections and 
testing. One commenter states that various failure modes of the system 
should be analyzed and that various system changes should be 
implemented to prevent failure. Five commenters suggest that adding 
provisions to isolate the crossfeed lines or adding crossfeed valves 
could be a proposed solution to the problem. Each of the other 
commenters recommend at least one of the following:

--Installing a fire detector system;
--Incorporating a ``tell tale'' patch that changes color with heat 
exposure, or using paint that changes color when exposed to heat;
--Incorporating heat shields to protect the fuel lines that are behind 
the firewall from the effects of the exhaust heat; and
--Adding heat shields to the firewall.

    The FAA concurs that adding a design change would be a more 
desirable solution to the exhaust system problems on the Cessna 300 and 
400 series airplanes rather than relying on repetitive inspections and 
testing to detect any problems. The FAA reviewed many of the design 
ideas presented above, and found that they are designed to mitigate the 
effects of an exhaust system failure, but none prevent failure of the 
exhaust system. The FAA currently knows of no such design changes that 
would provide the same safety level as those actions in this AD. The 
FAA will look at any design changes on an individual basis if they are 
submitted as an alternative method of compliance in accordance with the 
procedures specified in this AD. No changes have been made to this AD 
as a result of this comment.

Comment Issue No. 19: V-Band Clamps

    One commenter recommends that the FAA change the word V-band clamps 
in paragraph (g) of the NPRM to multi-segment V-band clamps. This 
commenter states that this was an oversight by the FAA.
    The FAA concurs and has revised this AD accordingly.

Comment Issue No. 20: All Airplanes Should Not Be Affected

    Five commenters suggest that there are design differences in the 
affected airplanes and believe that this AD should not apply to all 
airplanes. One commenter states that less demand is placed on the 
exhaust system of unpressurized airplanes and this AD should only apply 
to pressurized airplanes.
    The FAA's analysis and interpretation of the service history on the 
exhaust systems of the Cessna 300 and 400 series airplanes does not 
indicate that certain designs are more/less susceptible to the exhaust 
system problems than others. No changes have been made to this AD as a 
result of this comment.

Comment Issue No. 21: Lesser Requirements for Newer Exhaust Systems

    Several commenters believe that less stringent initial inspection 
requirements should exist for airplanes with newer exhaust systems 
installed. The commenters do not feel that the potential for damage 
exists for airplanes with exhaust systems that have not been in service 
for very long.
    The FAA sees merit in this comment and has re-evaluated the 
compliance time of the initial inspection for cracks, corrosion, holes, 
or distortion, which is the inspection that requires removal of the 
tailpipes. The FAA has determined that the initial inspection 
compliance time should read ``upon the accumulation of 5 years since 
installing a new or overhauled exhaust system or within the next 100 
hours time-in-service (TIS) after the effective date of this AD, 
whichever occurs later.''
    The FAA has revised the AD accordingly.

Comment Issue No. 22: Certification Process of Exhaust Systems

    One commenter believes that the FAA is changing the certification 
process of exhaust systems because the requirements of this AD were not 
required at the time the airplanes were type certificated.
    The FAA does not concur. The exhaust systems that were certificated 
with the airplane met all design criteria at the time of certification 
are not available to the field or the current maintenance procedures 
are AD's are the vehicle that the FAA uses to mandate modifications, 
inspections, etc. to correct an unsafe condition that is caused by 
airplane usage (fatigue), quality control, or maintenance problems 
(where the procedures to accomplish such maintenance not meeting the 
necessary safety level). The FAA has determined that the current 
maintenance procedures for the exhaust systems of the Cessna 300 and 
400 series airplanes, including those required by AD 75-23-08 R5, are 
not adequate to eliminate the unsafe condition. No changes have been 
made to this AD as a result of this comment.

Comment Issue No. 23: Welds and Weld Repairs

    Several commenters express opinions concerning welds and the use of 
weld repairs in the NPRM. The comments vary and include the following:

--Patch welds should be banned;
--Patch welds should be retained;
--Inlay weld repairs should be allowed;
--Multi-seam welds should be defined;
--Butt welds are a better type of weld;
--No welds should be allowed; and
--Patch or multi-seam weld repairs should not be left in service for 
500 hours TIS and should be removed after 100 hours TIS.

    The FAA has further examined the subject of welds on the exhaust 
systems as a method of repair and has incorporated the following into 
this AD:

--Overlay patch-type and parallel multi-seam weld repairs will not be 
permitted;
--Inlay patch repairs and multi-seam welds at the joints that are 
similar to the original construction are acceptable;
--Inspection schedules have been adjusted; and
--Removal of patch and multi-seam welds will not be required at 100 
hours TIS, and will be inspected on

[[Page 2850]]

condition until removed with the rest of the exhaust system.

Comment Issue No. 24: Exhaust System Removal Requirement

    One commenter recommends that the FAA remove paragraph (i) from the 
NPRM. This paragraph specifies removal of the exhaust system from the 
slip joints and specifies the system be sent to an exhaust repair 
facility to be inspected for serviceable condition with accomplishment 
of necessary repairs. The FAA infers that the commenter believes that 
these requirements are not necessary.
    The FAA does not concur. Based on its analysis of all information 
related to this subject, the FAA has determined that the removal, 
inspection, and possible repair requirements are necessary to reach the 
necessary safety level intended by this AD. The FAA has revised the 
compliance time to coincide with engine overhauls, when the system is 
removed for other reasons, thereby reducing the downtime of the 
airplane.

Comment Issue No. 25: No Compelling Safety Issues

    Five commenters state that there are no compelling safety issues 
driving this AD action. These commenters further explain that this is 
evidenced through the AD process delays and the amount of time it took 
the FAA to issue the NPRM. The FAA infers that the commenters would 
like the NPRM withdrawn.
    The FAA does not concur. The FAA has determined that an unsafe 
condition exists and this condition must be corrected. No changes have 
been made to this AD as a result of this comment.

Comment Issue No. 26: No Guarantee That the AD Will Work

    One commenter states that there is no guarantee that the actions 
specified in the NPRM will eliminate the unsafe condition on the 
affected airplanes. The FAA infers that the commenter wants the NPRM 
withdrawn.
    The FAA believes that, based on its analysis and evaluation of all 
available information related to this subject, the actions in this AD 
address items that have directly contributed to exhaust system 
incidents and accidents on the Cessna 300 and 400 series airplanes. The 
FAA also believes that the final rule AD (with the changes made to the 
NPRM) will be easier to comply with than AD 75-23-08 R5.

Comment Issue No. 27: Impossible To Comply With the AD

    One commenter states that Environmental Protection Agency (EPA) 
requirements make it impossible to comply with the NPRM. The commenter 
expresses that this is due to the requirement to use certain solvents 
that the EPA has banned.
    No banned substances are required to accomplish this AD. No changes 
have been made to this AD as a result of this comment.

Comment Issue No. 28: Extend the Comment Period

    One commenter requests an extension to the comment period to allow 
persons to comment. The commenter states that this is necessary because 
the existence of the NPRM was not widely known.
    The FAA does not concur. Based on the fact that over 350 comments 
were received, the FAA believes that it was widely known that the NPRM 
was issued and available. The FAA is aware that several owner 
associations sent their members individual letters advising them of the 
content and availability of the NPRM, and encouraging the owners to 
comment. In addition, the FAA is aware of several news articles that 
publicized the proposed action. The FAA has determined that there was 
adequate time to comment on the NPRM. No changes have been made to this 
AD as a result of this comment.

Comment Issue No. 29: More Information on the Accident Airplanes

    One commenter requests more information on the accidents referenced 
in the NPRM. The FAA infers that the commenter does not believe the 
action is justified based on the information provided in the NPRM. The 
commenter is requesting information such as the age of the airplanes, 
the maintenance of the airplanes, the frequency in which the airplanes 
were flown, the States where the accidents occurred, any temperature 
swings that were involved, and the provider of the failed parts.
    The FAA did a thorough investigation and examination of all the 
information available on the exhaust system failures of the Cessna 300 
and 400 series airplanes, and has determined that the explanation 
presented in the NPRM adequately explained the situation. No changes 
have been made to this AD as a result of this comment.

Comment Issue No. 30: Exhaust System Time Is Not Always Recorded

    One commenter states that, although required by FAA regulations, 
exhaust system component time is not always recorded or recorded 
correctly. The commenter states that improper maintenance and 
recordkeeping can negate any mandated action. The commenter makes no 
suggestion as to modifying or eliminating this AD action.
    No changes had been made to this AD as a result of this comment.

Comment Issue No. 31: Exhaust Systems Have a Limited Life

    One commenter states that exhaust system components have a limited 
life. This commenter believes that the FAA should require replacement 
of the exhaust system at a certain time of hours TIS.
    The FAA concurs that exhaust systems have a limited life. However, 
the utilization differences between operators and the environment where 
the airplanes are operated contribute to the condition. For these 
reasons, a definite life limit on the exhaust systems could not be 
established and the FAA is requiring repetitive inspections and tests 
to assure that the condition of the systems is adequate. No changes 
have been made to this AD as a result of this comment.

Comment Issue No. 32: Apply a Corrosion Standard

    Several commenters suggest that the FAA should incorporate a 10-
percent corrosion standard for the corrosion inspection of the engine 
beams and bulkhead. These commenters state that the proposed AD will 
require structural repair if any corrosion is found on the engine 
beams, canted bulkhead, or firewalls.
    The FAA concurs that a reasonable standard should be applied. 
Revisions have been incorporated that require further investigation if 
corrosion or damage is found during the inspections. This includes 
holes or defects in the structural components. A 10-percent material 
thickness requirement for engine beam damage has been included in the 
AD.

Comment Issue No. 33: Visual Examination and Pressure Tests Are 
Adequate

    Many commenters believe that visual examination and pressure tests 
of the exhaust systems are adequate to meet the necessary safety level 
intended by this AD. These commenters state that they have found 
defects by visual and pressure checking.
    The FAA does not concur. Although visual examination and pressure 
tests will reveal defects, many defects may go undetected if only these 
tests are utilized. No changes have been made to this AD as a result of 
this comment.

The FAA's Determination

    After careful review of all available information related to the 
subject

[[Page 2851]]

presented above, the FAA has determined that air safety and the public 
interest require the adoption of the rule as proposed except for the 
changes discussed above in the comment disposition and minor editorial 
corrections. The FAA has determined that these changes and minor 
corrections will not change the meaning of this AD and will not add any 
additional burden upon the public than was already proposed. In fact, 
the changes made based on the comments received will actually reduce 
the burden that was originally proposed in the NPRM.

Comments Invited

    Although this action is in the form of a final rule that was 
preceded by notice and opportunity for comment, public comments are 
again invited on this rule. The FAA has determined that because of the 
large number of comments received on the proposed rule and the 
controversial nature of the situation, the public should be provided an 
opportunity to comment on the changes being made in this final rule. In 
addition, the FAA is in the process of completing a regulatory 
flexibility analysis for this action. The FAA anticipates completion of 
the analysis well within 180 days after issuance of this AD and will 
accept comments on the analysis at any time, even after the comment 
closing date for comments on this final rule. The FAA is particularly 
interested in receiving factual information on alternative means of 
compliance with the AD as well as the regulatory flexibility analysis
    Interested persons are invited to comment on this rule by 
submitting such written data, views, or arguments as they may desire. 
Communications should identify the Rules Docket number and be submitted 
in triplicate to the address specified above. 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 No. 97-CE-67-AD.'' The postcard will be date stamped and 
returned to the commenter.

Cost Impact

    The FAA estimates that 6,500 airplanes in the U.S. registry will be 
affected by this AD. The cost of the inspections will be as follows at 
an average labor rate of approximately $60 per hour. The cost of any 
necessary repair depends on the extent of the rework and replacement 
needed based on the results of the inspections.

--The repetitive visual inspections of the exhaust system will take 
approximately 3 workhours to accomplish, with a labor cost of $180 per 
airplane for each inspection;
--The repetitive visual inspections of the removed tailpipes will take 
approximately 1 workhour per tailpipe to accomplish, with a labor cost 
of $120 per airplane for each inspection;
--The inspection of the engine beams and canted bulkheads, as a result 
of damage to the tailpipes, will take approximately 3 workhours to 
accomplish, with a labor cost of $180 per airplane;
--The inspection of the fuel tubing behind the firewall, as a result of 
damage to the tailpipes, engine beams, and canted bulkheads, will take 
approximately 16 workhours to accomplish, with a labor cost of $960 per 
airplane;
--The replacement of the fuel tubing, if necessary, will take 
approximately 30 workhours to accomplish, with a labor cost of $1,800 
per airplane;
--The requirement of removing exhaust system prior to shipping to an 
approved facility will take approximately 8 workhours, with a labor 
cost of $480 per airplane. The cost of shipping the exhaust system to 
the facility and the inspections by the facility is estimated at $500 
per airplane;
--The repetitive pressure test is estimated to take 1 workhour, with a 
labor cost of $60 per airplane; and
--The multi-band V-clamp replacement is estimated to take 1 workhour, 
with a labor cost of $60 per airplane.

    The total cost impact on the U.S. operators for the initial 
inspections is estimated to be $28,210,000, or $4,340 per airplane. The 
maximum expense for full exhaust parts replacement is estimated to be 
approximately $60,000 per airplane. These figures do not take into 
account the costs of any repetitive inspections or repairs or 
replacements that may be necessary. The FAA has no way of determining 
the number of repetitive inspections an owner/operator will incur over 
the life of the airplane, or the extent of the repairs and replacements 
that may be necessary for any affected airplane.

Compliance Time of This AD

    Certain repetitive inspections of this AD are presented in both 
calendar time and hours time-in service (TIS). The unsafe condition 
specified in this AD is a result of the stress cracking and/or 
corrosion that results over time. Stress corrosion starts as a result 
of high local stress incurred through operation of the affected part 
(the exhaust systems). Corrosion can then develop regardless of whether 
the airplane is in operation. The cracks may not be noticed initially 
as a result of the stress loads, but could then progress as a result of 
corrosion. The stress incurred during flight operations (while in-
flight) or temperature changes (either while in-flight or on the 
ground) could then cause rapid crack growth. In order to assure that 
these stress corrosion cracks do not go undetected, a compliance time 
of specific hours TIS and calendar time (whichever occurs first) is 
utilized.

Regulatory Flexibility Analysis

    The FAA believes that this regulation may have a significant 
economic impact on a substantial number of small businesses.
    Due to the urgent nature of the safety issues addressed, the FAA 
was not able to complete a regulatory flexibility analysis prior to 
issuing the NPRM. As stated in the NPRM, the FAA will complete the 
final regulatory flexibility analysis within 180 days after issuance of 
this AD. Copies of this analysis may be obtained at that time at the 
Central Region, Office of the Regional Counsel, Attention: Rules Docket 
No. 97-CE-67-AD, 901 Locust, Room 506, Kansas City, Missouri 64106.

Regulatory Impact

    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

[[Page 2852]]

not have sufficient federalism implications to warrant the preparation 
of a Federalism Assessment.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and (3) may have a 
significant economic impact, positive or negative, on a substantial 
number of small entities under the criteria of the Regulatory 
Flexibility Act.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, 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 U.S.C. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing Airworthiness Directive 
(AD) 75-23-08 R5, Amendment 39-5451, and by adding a new AD to read as 
follows:

2000-01-16  Cessna Aircraft Company: Amendment 39 11514; [Docket No. 
97-CE-67-AD].

    Applicability: Models T310P, T310Q, T310R, 320, 320A, 320B, 
320C, 320D, 320E, 320F, 320-1, 335, 340, 340A, 321 (Navy OE-2),401, 
401A, 401B, 402, 402A, 402B, 402C, 404, 411, 411A, 414, 414A, 421, 
421A, 421B, and 421C airplanes, all serial numbers, certificated in 
any category.

    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 (i) 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 in the compliance table in 
Figure 1 of this AD, unless already accomplished. Compliance times 
of this AD may be extended 10-percent to work the actions in with 
already scheduled maintenance.
    To detect and correct cracks and corrosion in the exhaust 
system, which could result in exhaust system failure and a possible 
uncontrollable in-flight fire with pilot and/or passenger injury, 
accomplish the following:
    (a) The following paragraphs present the type of individuals who 
have the authority to accomplish the actions of this AD:
    (1) Repairs: Required to be accomplished at an FAA-approved 
exhaust repair facility (or for non U.S.-registered airplanes: the 
state of registry's equivalent facility in accordance with their 
applicable procedure).
    (2) Replacements: Required to be accomplished in accordance with 
the appropriate Cessna Service Manual and must be accomplished by a 
person holding a currently effective mechanic certificate with both 
an airframe and powerplant (A&P) rating or by an individual 
authorized to represent an FAA-approved repair station (or for non 
U.S.-registered airplanes: the state of registry's equivalent 
facility in accordance with their applicable procedure).
    (3) Visual inspections except for paragraph (g) of this AD: 
Required to be accomplished by a person holding a currently 
effective mechanic certificate with both an airframe and powerplant 
(A&P) rating (or for non U.S.-registered airplanes: the state of 
registry's equivalent facility in accordance with their applicable 
procedure).

    Note 2:  Commercial certificate holders operating under part 121 
or part 135 of the Federal Aviation Regulations (14 CFR part 121 or 
14 CFR part 135) could have accomplished the actions of this AD if 
in compliance with an FAA-approved maintenance program. ``Unless 
already accomplished'' credit should be taken in these situations.


    Note 3:  Cessna service information and Maintenance Manual 
Revisions include assembly, disassembly, and general guidance 
information for the subject of this AD. These documents should not 
be utilized for repairs. This AD takes precedence over these 
documents.



[[Page 2853]]


[GRAPHIC] [TIFF OMITTED] TR19JA00.000

    (b) At the Initial Compliance Time and Repetitive Compliance 
Times specified in Figure 1 of this AD, visually inspect the exhaust 
system for burned areas, cracks, or looseness. If any area of the 
exhaust system shows damage as defined in the Appendix of this AD, 
prior to further flight, repair or replace the damaged part.

    Note 4:  Cessna Service Bulletin (SB) MEB99-6, Cessna SB MEB99-
9, and Cessna SB MEB99-12, all dated August 2, 1999, specify and 
include procedures for installing access panels to help with the 
exhaust system inspections. Each service bulletin applies to various 
Cessna airplane models.

    (c) At the Initial Compliance Time specified in Figure 1 of this 
AD, remove the tailpipes and visually inspect for cracks, corrosion, 
holes, or distortion.
    (1) If no crack, corrosion, hole, or distortion is found, 
continue to visually inspect at intervals indicated in Repetitive 
Compliance Times in Figure 1 of this AD.
    (2) If a crack, corrosion, hole, or distortion is found during 
any inspection, prior to further flight, repair or replace the 
tailpipe.

    Note 5:  Although not required by this AD, the FAA recommends 
removing and cleaning internally (every 12 calendar months) all

[[Page 2854]]

tailpipes that are more than 5 years old from the date of 
manufacture or overhaul (yellow tag). This includes accomplishing 
the following:

    --inspecting for cracks, pinholes, corrosion buildup, and 
general airworthiness;
    --overhauling the tailpipe or replacing all parts considered 
suspect; and
    --approving for return to service of all parts considered 
airworthy.

    Note 6:  The FAA recommends checking the turbocharger wheel for 
ease of rotation any time the tailpipe is removed. Excessive 
friction in the turbocharger wheel bearings can cause high exhaust 
back pressure, which can adversely affect the cylinder compression, 
the exhaust valve guide, and the exhaust valve and piston life. The 
turbine wheel should continue to rotate for at least three seconds 
after spinning induced by fingers or a wooden tool.


    Note 7:  The FAA recommends examining the system to assure that 
cables and torque tag values are intact on the single-piece V-band 
clamps.

    (d) At the Initial Compliance Time and Repetitive Compliance 
Times specified in Figure 1 of this AD, visually inspect the 
outboard engine beam (adjacent to the tailpipe) and the canted 
bulkheads for signs of distress, chafing, corrosion, or cracking. 
Even though some airplanes may have stainless steel engine beams, 
carefully inspect the areas of contact between the engine beam and 
canted bulkhead for corrosion.
    (1) If damage to the engine beams is found that exceeds 10-
percent of the material thickness or there is evidence of 
overheating on the firewall beyond that which can be removed with 
``scotchbrite '' or equivalent, prior to further flight, replace the 
firewall and the aluminum fuel lines behind the firewall. Stainless 
steel fuel lines are available from the Cessna Aircraft Company. 
Replacement of the fuel lines behind the firewall may require 
removing and replacing the firewall or accomplishing major repair of 
the firewall.
    (2) Prior to further flight, accomplish one of the following:
    (i) Repair any chafing, corrosion, or cracking on the engine 
beams or canted bulkheads or distress or damage beyond that which is 
described in paragraph (d)(1) of this AD, in accordance with data 
provided by any individual or facility that is authorized by the FAA 
to perform the necessary repairs or provide the FAA approved data to 
authorized personnel for repair of these items; or
    (ii) Replace any parts that have chafing, corrosion, or cracking 
on the engine beams or canted bulkheads, or distress or damage 
beyond that which is described in paragraph (d)(1) of this AD.
    (e) At the Initial Compliance Time (which is based on the 
condition of the exhaust system at the slip joints and aft) and 
Repetitive Compliance Times specified in Figure 1 of this AD, 
inspect the exhaust system from the slip joints and aft and perform 
a pressure test in accordance with the Appendix of this AD. If any 
condition as specified in the Appendix of this AD is found, prior to 
further flight, send these parts to an FAA-approved exhaust repair 
facility for inspection and possible repair or replace the affected 
parts with serviceable parts approved for the affected airplanes.
    (f) At the Initial Compliance Time and Repetitive Compliance 
Times specified in Figure 1 of this AD, replace all multi-segment V-
band clamps per the appropriate Cessna Service Manual.
    (g) At the Initial Compliance Time and Repetitive Compliance 
Times specified in Figure 1 of this AD, remove the exhaust system 
from the slip joints and aft to all turbo-charger attached 
components, and send to any FAA-approved exhaust repair facility. 
The FAA approved exhaust repair facility will inspect this portion 
of the exhaust system for serviceable condition and make any 
necessary repairs to these items. No overlay patch-type or parallel 
multi-seam weld repairs are permitted. Inlay patch repairs and 
multi-seam welds at joints that are similar to the original 
construction are acceptable.
    (h) 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. Isolation of the 
fuel cross feed lines behind the firewall may be required.
    (i) An alternative method of compliance or adjustment of the 
initial or repetitive compliance times that provides an equivalent 
level of safety may be approved by the Manager, Wichita Aircraft 
Certification Office, 1801 Airport Road, Room 100, Wichita, Kansas 
67209.
    (1) The request shall be forwarded through an appropriate FAA 
Maintenance Inspector, who may add comments and then send it to the 
Manager, Wichita Aircraft Certification Office.
    (2) Alternative methods of compliance approved in accordance 
with AD 75-23-08 R5 are not considered approved as alternative 
methods of compliance for this AD.

    Note 8:  Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Wichita Aircraft Certification Office.

    (j) Information related to this AD may be examined at the FAA, 
Central Region, Office of the Regional Counsel, 901 Locust, Room 
506, Kansas City, Missouri 64106.
    (k) This amendment supersedes AD 75-23-08 R5, Amendment 39-5451.

Appendix to Docket No. 97-CE-67-AD

Visual Inspection

(a) Cleaning

    In order to properly inspect the exhaust system, components must 
be clean and free of oil, grease, etc. If required, clean as 
follows:
    (1) Clean engine exhaust components with a suitable solvent, 
allow to drain, and wipe dry with a clean cloth.
    WARNING: Never use highly flammable solvents on engine exhaust 
systems. Never use a wire brush or abrasives to clean exhaust 
systems or mark on the system with lead pencils.
    (2) Remove the heat shields from the turbocharger in accordance 
with the heat shield removal procedures in the appropriate Cessna 
Aircraft Service Manual.
    (3) Remove shields around the exhaust bellows or slip joints, 
multi-segment ``V'' band clamps at joints, and other items that 
might hinder the inspection of the system. Removal of the ``V'' band 
clamps may not be necessary.
    (4) Using crocus cloth, polish any suspect surfaces to verify 
that no cracks or pinholes exist in the material. Replace or repair 
any part where cracks or pinholes exist.

(b) Visual Inspection of Complete System

    Note 1:  Conduct this inspection when the engine is cool.

    (1) Visually inspect exhaust stacks for burned areas, cracks, 
bulges, and looseness. Make sure the attach bolts are properly 
torqued, in accordance with the appropriate Cessna Aircraft Service 
Manual.

    Note 2:  During this inspection, pay special attention to the 
condition of the bellows, if installed, and welded areas along the 
seams; the welded areas around the bellows; and the welded seams 
around the exhaust system components.


    (2) Visually inspect the flexible connection between the waste-
gate and overboard duct (when applicable) for cracks and security.
    (3) Visually inspect the exhaust joint springs for correct 
compression. If the joint is disturbed or if the springs are 
obviously loose or frozen, proceed with the following inspection 
(see Figure 1 of this Appendix).
    (i) Before removal of the exhaust joint springs, measure the 
installed length of each spring, and replace the springs compressed 
to less than .45 inch.
    (ii) Remove all the springs and measure the free length. Replace 
any spring having a free length of less than .57 inch.

    Note 3:  Add AN960-10 (or FAA-approved equivalent part number) 
washers under the head of the joint bolts as required to obtain the 
correct dimension. During installation, the joint bolts should be 
tightened gradually and spring length checked frequently to prevent 
overcompression of the springs.

    (iii) Reinstall the springs and measure the installed length. 
The length must be .51 inch (+.00, -.03 inch).
    (4) If installed, visually inspect the slip joint(s) for bulges 
beyond the normal manufacturing irregularities of .03 inches and/or 
cracks. If any bulges and/or cracks are present, replace the bulged 
or cracked slip joint(s). (Refer to the appropriate Cessna Aircraft 
Service Manual) (See Figure 2 of this Appendix).

(c) Inspection of the Multi-Segment ``V'' Band Clamp(s) (Between 
Engine and Turbocharger)

    (1) Using crocus cloth, clean the outer band of the multi-
segment ``V'' band clamp(s). Pay particular attention to the spot 
weld area on the clamp(s).
    (2) With the clamp(s) properly torqued, progress to the 
following actions:
    (i) Visually inspect the outer band in the area of the spot weld 
for cracks (see Figure

[[Page 2855]]

3 of this Appendix). If cracks are found, replace the clamp(s) with 
new multi-segment ``V'' band clamp(s).

Appendix to Docket No. 97-CE-67-AD (continued)

    (ii) Visually inspect the corner radii of the clamp inner 
segments for cracks (see Figure 3 of this Appendix). This inspection 
requires careful use of artificial light and inspection mirrors.
    (iii) Visually inspect the flatness of the outer band, 
especially within 2 inches of the spot welded tabs that retain the 
T-bolt fastener. This can be done by placing a straight edge across 
the flat part of the outer band as shown in Figure 4 of this 
Appendix, then check the gap between the straight edge and the outer 
band. This gap should be less than 0.062 inch. If deformation 
exceeds the 0.062-inch limit, replace the clamp(s) with new multi-
segment clamp(s). (See Figure 3 of this Appendix). See Cessna 
maintenance manual(s) and revisions for correct installation 
procedures.
    (iv) Visually inspect the one-piece ``V'' band clamp (overboard 
exhaust to turbocharger) with a light and mirror, in the area of the 
clamp surfaces adjacent to the intersection of the ``V'' apex and 
bolt clips, and the entire length of the ``V'' apex of the clamp for 
signs of cracks or fractures. If cracks or fractures are visible, 
replace the clamp (see Figure 5 of this Appendix). See Cessna 
service manual(s) and revisions for correct installation procedures

[[Page 2856]]

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[[Page 2857]]


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[[Page 2858]]


[GRAPHIC] [TIFF OMITTED] TR19JA00.003


[[Page 2859]]


[GRAPHIC] [TIFF OMITTED] TR19JA00.004


[[Page 2860]]


[GRAPHIC] [TIFF OMITTED] TR19JA00.005

Inspection of the Exhaust System Aft of the Slip Joints

    (a) Remove all top and bottom engine cowlings, as well as the 
under-nacelle inspection panels (on aircraft so equipped). Remove 
the nacelle-mounted induction air filter canister, slip-joint heat 
shields, turbocharger heat shields, and any other readily-removable 
components that facilitate a better view of the exhaust system aft 
of the slip joints.
    (b) Visually inspect each elbow pipe that runs from the slip 
joint to the wye duct. Carefully inspect the hard-to-see areas where 
the manifold passes through the canted bulkhead, beneath the clamp-
on heat shields, and around the flange and V-band clamp, where it 
joins the wye. Use a flashlight and mirror to inspect the areas that 
cannot be seen directly.
    (1) Look for evidence of exhaust stains, bulges, cracks, or 
pinholes.
    (2) Exhaust stains or evidence of heat-induced corrosion on any 
portion of the engine mount beams or canted bulkhead should be 
grounds for removing the elbow pipe for closer inspection.

[[Page 2861]]

    (3) Inspect for cracks, bulges, pinholes, or corrosion on the 
elbow (manifold) pipe, and if any of this damage is found, replace 
the elbow pipe.
    (c) Visually inspect each wye duct beneath the turbocharger for 
leakage, stains, cracks, or pinholes, and, if damaged, repair or 
replace. Carefully inspect the hard-to-see area between the duct and 
firewall.
    (1) Carefully inspect the turbocharger and waste-gate flanges 
and welded seams between the ducts and the firewall for evidence of 
exhaust stains on the wye or the firewall, bulges, cracks, or 
pinholes.
    (2) If exhaust stains, bulges, cracks or pinholes are found, 
repair or replace the damaged part.

Pressure Test

    (a) Pressurize the exhaust system with air regulated to 20 PSI 
or below.
    (b) Apply this air pressure to the tailpipe. Fabricate shop 
fixtures as required to accomplish this.
    (c) Seal off the waste-gate pipe.
    (d) Check the tailpipe, elbow pipes and the wye duct for leaks 
by spraying leak check fluid (bubbling) on these parts and looking 
for the appearance of bubbles. Some air leakage is normal at the 
joints and flanges, but none should be seen anywhere else.
    (e) Pay special attention to any weld repairs, and various hard-
to-see areas described previously.
    (f) If the tailpipes, elbow pipes, or the wye ducts fail the 
pressure test, repair or replace the distressed component.
    (m) This amendment becomes effective on February 15, 2000.

    Issued in Kansas City, Missouri, on January 10, 2000.
Michael Gallagher,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. 00-951 Filed 1-18-00; 8:45 am]
BILLING CODE 4910-13-U