[Federal Register Volume 64, Number 128 (Tuesday, July 6, 1999)]
[Proposed Rules]
[Pages 36307-36318]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-16752]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 97-CE-67-AD]
RIN 2120-AA64
Airworthiness Directives; Cessna Aircraft Company 300 and 400
Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: This document proposes to supersede 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 proposed AD would
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 proposed AD would also revise
the inspection intervals and would require replacing certain
unserviceable parts and removing the exhaust system for detailed
inspections at regular intervals. The proposed 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 the
proposed 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: Comments must be received on or before August 9, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Central Region, Office of the Regional Counsel,
Attention: Rules Docket No. 97-CE-67-AD, Room 1558, 601 E. 12th Street,
Kansas City, Missouri 64106. Comments may be inspected at this location
between 8 a.m. and 4 p.m., Monday through Friday, holidays excepted.
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:
Comments Invited
Interested persons are invited to participate in the making of the
proposed 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. The FAA
believes that the proposed 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 has been unable to
complete a preliminary regulatory flexibility analysis prior to
issuance of the NPRM. A final regulatory flexibility analysis will be
completed before, or within 180 days of issuance of, the final rule. To
assist in this analysis, the FAA is particularly interested in
receiving information on the impact of the proposed rule on small
businesses and suggested alternative methods of compliance that reduce
or eliminate such impacts. All communications received on or before the
closing date for comments, specified above, will be considered before
taking action on the proposed rule. The proposals contained in this
notice may be changed in light of the comments received.
Comments are specifically invited on the overall regulatory,
economic, environmental, and energy aspects of the proposed 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 proposal will be filed in the Rules Docket.
[[Page 36308]]
Commenters wishing the FAA to acknowledge receipt of their comments
submitted in response to this notice 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.
Availability of NPRMs
Any person may obtain a copy of this NPRM by submitting a request
to the FAA, Central Region, Office of the Regional Counsel, Attention:
Rules Docket No. 97-CE-67-AD, Room 1558, 601 E. 12th Street, Kansas
City, Missouri 64106.
Discussion
AD 75-23-08 R5, Amendment 39-5451, 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.
Cessna and the FAA performed extensive investigation and found the
following possible causes and effects of these exhaust problems:
--Significant vibration between the beam-mounted engine and the
firewall-mounted turbocharger;
--Leaking exhaust gases, which can cause fuel line failure because the
fuel lines behind the firewall overheat and rupture. (Most of these
fuel lines cannot be isolated or shut-off);
--Reduced structural strength of the engine mount beams and canted
bulkheads as a result of exposure to high heat, which could compromise
the engine installation; and
--Structural failure of the wing or loss of flight control that results
from an in-flight fire.
The FAA issued AD 75-23-08 and five subsequent revisions to this
AD, including the current one referenced above, as an attempt to manage
these problems through repetitive visual inspections.
Actions Since Issuance of Previous Rule
In the 20 plus years since the issuance of AD 75-23-08, failures of
exhaust systems on Cessna 300 and 400 series airplanes have continued
to occur and have contributed to fatalities. The FAA, the National
Transportation Safety Board (NTSB), and Cessna have conducted numerous
tests and analysis on the exhaust system configurations in an attempt
to resolve the repeated problems and to alleviate these failures.
The FAA and the NTSB have issued several safety recommendations to
provide guidance on how to alleviate problems with the exhaust systems
on Cessna 300 and 400 series airplanes. From these recommendations, the
FAA has developed new service information (included as an Appendix to
this AD) and Cessna has revised the maintenance and service manuals.
The FAA believes that this new information should help to reduce the
confusion of the requirements in the current action and simplify the
procedures.
A recent fatal accident has occurred involving a Cessna Model 421B
airplane. While not implicated in the cause of the accident, the FAA
and the NTSB have determined that the exhaust system on the accident
airplane was in a condition of imminent catastrophic failure. The
airplane records indicate that the exhaust system inspection and
replacement requirements of AD 75-23-08 R5 had been accomplished.
The FAA's Determination
After examining the circumstances and reviewing all available
information related to the incidents described above, including the
referenced service information, the FAA has determined that AD action
should be taken 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. Exposure to these conditions
could cause injury to the pilot and passengers during flight.
Explanation of the Provisions of the Proposed AD
Since an unsafe condition has been identified that is likely to
exist or develop in other Cessna 300 and 400 series airplanes of the
same type design, the FAA is proposing an AD to supersede AD 75-23-08
R5. The proposed AD would 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 proposed AD would also revise the inspection intervals and would
require replacing certain unserviceable parts and removing the exhaust
system for detailed inspections at regular intervals. Provisions of the
proposed AD include:
--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.
Service Information
In the future, Cessna may develop service information or additional
maintenance and/or service manual revisions to address this issue. The
FAA will issue alternative methods of compliance to this AD if the
procedures are deemed acceptable to address the unsafe condition
specified in the proposed AD.
Cost Impact
The FAA estimates that 6,500 airplanes in the U.S. registry would
be affected by the proposed AD. The cost of the proposed inspections
would 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 proposed
inspections.
--The proposed repetitive 50-hour time-in-service (TIS) visual
inspections of the exhaust system would take approximately 3 workhours
to accomplish, with a labor cost of $180 per airplane for each
inspection;
--The proposed repetitive 100-hour TIS visual inspections of the
removed tailpipes would take approximately 1 workhour per tailpipe to
accomplish, with a labor cost of $120 per airplane for each proposed
inspection;
--The proposed inspection of the engine beams and canted bulkheads, as
a result of damage to the tailpipes, would take approximately 3
workhours to accomplish, with a labor cost of $180 per airplane;
--The proposed inspection of the fuel tubing behind the firewall, as a
result of damage to the tailpipes, engine beams, and canted bulkheads,
would take approximately 16 workhours to accomplish, with a labor cost
of $960 per airplane;
--The proposed replacement of the fuel tubing, if necessary, would take
approximately 30 workhours to accomplish, with a labor cost of $1,800
per airplane;
--The proposed 500-hour TIS proposed requirement of removing and
shipping the exhaust system to an approved facility would take
approximately 8 workhours, with a labor cost of $480. The cost of
shipping the exhaust system to the facility and the inspections by the
facility is estimated at $500;
--The proposed repetitive pressure test is estimated to take 1
workhour, with a labor cost of $60 per airplane; and
--The proposed V-band 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 proposed
initial inspections is estimated to be
[[Page 36309]]
$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 the account the costs of any
repetitive inspections or repairs or replacements that would be
necessary if the FAA adopted the proposed rule. 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 the proposed AD are presented in
both calendar time and hours time-in-service (TIS). The unsafe
condition specified in the proposed 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 proposed.
Regulatory Impact
The regulations proposed herein would 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
proposal would 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) if promulgated,
may have a significant economic impact on a substantial number of small
entities under the criteria of the Regulatory Flexibility Act. The FAA
is currently conducting a Regulatory Flexibility Determination and
Analysis and has considered alternatives to the proposed AD that could
minimize the impact on small entities.
After careful consideration, the FAA determined that AD action is
the best course of action to address the unsafe condition specified in
this document; and (2) the situation does not warrant waiting for the
completion of the Regulatory Flexibility Determination and Analysis
before issuing the NPRM. When completed, a copy of the Regulatory
Flexibility Determination and Analysis will be placed in the Docket
file and can be obtained at the address specified in the caption
ADDRESSES.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Safety.
The Proposed Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration proposes to amend 14
CFR part 39 of the Federal Aviation Regulations 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:
Cessna Aircraft Company: Docket No. 97-CE-67-AD; Supersedes AD 75-
23-08 R5, Amendment 39-5451.
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 (k) 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.
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
repair facility.
(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.
(3) Visual inspections except for paragraphs (f) and (i) 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.
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(b) At the compliance time 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.
(c) At the 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 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.
(3) When a new tailpipe is installed after the effective date of
this AD, terminate the 100-hour time-in-service (TIS) repetitive
inspections required as specified in Figure 1 of this AD until the
accumulation of 500 hours TIS or 5 years from the installation date,
whichever occurs first, at which time continue the 100-hour TIS
inspection intervals.
(d) At the compliance time 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 or there is evidence
of overheating on the firewall, 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, repair any distress, chafing,
corrosion, or cracking on the engine beams or canted bulkheads 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.
(e) At the compliance time specified in Figure 1 of this AD,
inspect the exhaust system 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, repair or
replace the affected parts.
(f) At the compliance time specified in Figure 1 of this AD,
remove the exhaust system from the slip joints and aft to all
turbocharger-attached components and send to an FAA-approved
manufacturing and repair facility that is authorized by the FAA to
perform material and condition determinations, and prior to further
flight, accomplish any necessary repairs on these items.
Note 2: The following repair facilities have been approved as of
the effective date of this AD. A current list of FAA-approved
facilities can be obtained from the FAA, Wichita Aircraft
Certification Office, 1801 Airport Road, Room 100, Wichita, Kansas
67209; Attention: Paul O. Pendleton, Aerospace Engineer; telephone:
(316) 946-4143; facsimile: (316) 946-4407:
Wall Colmony Corp., 4700 S.E. 59th St., Oklahoma City, OK 73135,
(405) 672-1361
Knisley Welding Inc., 3450 Swetzer Road, Loomis, CA 95650, (916)
652-5891
Heliarc Welding Service, 3965 Newport St., 73135 Denver, CO 80207-
73135, (303) 672-1361
Note 3: The FAA-approved manufacturing and repair facilities
will perform the following and provide information to be utilized
for future actions required by this AD:
Determine the airworthiness of the exhaust system
parts;
Measure for the minimum acceptable material thickness
of .025 inch;
Determine the airworthiness of previous repairs (multi-
seam welds and patch-type welds are not considered airworthy);
Repair or replace all unserviceable parts (no multi-
seam or patch-type weld repairs are permitted);
Determine the material type of the exhaust system
(i.e., Inconel or stainless steel); and
Stamp the material type with an ``I'' for Inconel or
``SS'' for stainless steel, the name of the facility making the
determination, and the date on the exhaust system.
(g) At the compliance time specified in Figure 1 of this AD,
replace all V-band clamps per the appropriate Cessna Service Manual.
(h) At the compliance time specified in Figure 1 of this AD,
disassemble and visually inspect the slip joint for freedom of
motion. If the slip joint is seized or frozen, prior to further
flight, replace the slip joint.
(i) At the compliance time 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 patch-type or
multi-seam weld repairs are permitted.
(j) 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.
(k) 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, 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 4: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Wichita Aircraft Certification Office.
(l) Information related to this AD may be examined at the FAA,
Central Region, Office of the Regional Counsel, Room 1558, 601 E.
12th Street, Kansas City, Missouri 64106.
(m) 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) Spray engine exhaust components with a suitable solvent
(such as Stoddard 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 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.
[[Page 36312]]
Note 3. Add AN960-10 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 over-compression 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 3 of this Appendix). If cracks are found,
replace the clamp(s) with new multi-segment ``V'' band clamp(s).
(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
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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.
(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 turbo charger 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 turbo-charger 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.
Issued in Kansas City, Missouri, on June 25, 1999.
Michael Gallagher,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. 99-16752 Filed 7-2-99; 8:45 am]
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