[Federal Register: November 26, 2002 (Volume 67, Number 228)]
[Rules and Regulations]
[Page 70688-70691]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr26no02-9]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 99-NE-44-AD; Amendment 39-12957; AD 2002-23-13]
RIN 2120-AA64
Airworthiness Directives; Pratt & Whitney Canada PT6A Series
Turboprop Engines
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
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SUMMARY: This amendment adopts a new airworthiness directive (AD), that
is applicable to Pratt & Whitney Canada PT6A series turboprop engines
that have certain turbine exhaust ducts that were modified by a number
of different companies. This amendment requires inspections for low-
quality welds and cracks of a large population of turbine exhaust
ducts. This amendment is prompted by reports of cracks along the weld
seams of certain turbine exhaust ducts. The actions specified by this
AD are intended to prevent failure of the turbine exhaust duct due to
cracking that could result in possible separation of the reduction
gearbox and propeller from the engine, and possible loss of control of
the airplane.
DATES: Effective December 31, 2002. The incorporation by reference of
certain publications listed in the regulations is approved by the
Director of the Federal Register as of December 31, 2002.
ADDRESSES: The service information referenced in this AD may be
obtained from Pratt & Whitney Canada, 1000 Marie-Victorin, Longueuil,
Quebec, Canada J4G1A1. This information may be examined, by
appointment, at the Federal Aviation Administration (FAA), New England
Region, Office of the Regional Counsel, 12 New England Executive Park,
Burlington, MA; or at the Office of the Federal Register, 800 North
Capitol Street, NW., suite 700, Washington, DC.
FOR FURTHER INFORMATION CONTACT: James Lawrence, Aerospace Engineer,
[[Page 70689]]
Engine Certification Office, FAA, Engine and Propeller Directorate, 12
New England Executive Park, Burlington, MA 01803-5299; telephone (781)
238-7176; fax (781) 238-7199.
SUPPLEMENTARY INFORMATION: A supplemental proposal to amend part 39 of
the Federal Aviation Regulations (14 CFR part 39) to include an AD that
is applicable to Pratt & Whitney Canada PT6A series turboprop engines
was published in the Federal Register on June 10, 2002 (67 FR 39640).
That action proposed to require inspections for low-quality welds and
cracks of a large population of turbine exhaust ducts that were
modified by a number of companies, all using a similar unapproved gas
tungsten arc welding (GTAW) process instead of the resistance (seam or
stitch) weld process. Since the issuance of that supplemental proposal,
Pratt & Whitney Canada issued a revised SB P&WC SB No. PT6A-72-1610,
Revision 2, dated October 1, 2002, which deletes models PT6A-114 and
PT6A-114A from the applicability.
Bilateral Agreement Information
This engine model is manufactured in Canada and is type
certificated for operation in the United States under the provisions of
section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and
the applicable bilateral airworthiness agreement. Pursuant to this
bilateral airworthiness agreement, Transport Canada (TC) has kept the
FAA informed of the situation described above. The FAA has examined the
findings of TC, reviewed all available information, and determined that
AD action is necessary for products of this type design that are
certificated for operation in the United States.
Comments
Interested persons have been afforded an opportunity to participate
in the making of this amendment. Due consideration has been given to
the comments received.
Request To Remove SAL Reference
One commenter requests removal of any reference to Standard Aero
Limited (SAL) of Winnipeg, Canada, from the AD. Since the first issue
of the NPRM, the FAA has found that several other companies have
incorrectly used the GTAW weld process. Therefore, any references to
SAL can and will cause confusion for the operators.
The FAA agrees. All references to SAL are removed from the final
rule.
Misinterpretation of Unsafe Condition
The same commenter points out that the SNPRM incorrectly notes that
TC AD CF-98-14 says ``that condition if not corrected could result in
possible separation of the reduction gearbox and propeller from the
engine and possible loss of control of the airplane,'' and that the TC
AD actually states that compliance is required ``to minimize the
possibility of an in-flight shutdown due to a cracked exhaust duct.''
The FAA does not agree. The FAA feels that the commenter has
misinterpreted the unsafe condition statement in the proposal's
preamble, incorrectly attributing it to the TC AD. Based on the
structure of the preamble, the FAA understands how the statement could
be attributed to the TC AD. However, the FAA has determined ``that
condition if not corrected could result in possible separation of the
reduction gearbox and propeller from the engine and possible loss of
control of the airplane,'' is the correct unsafe condition. Since the
questionable section does not appear in the preamble of the final rule,
no change needs to be made to the final rule.
Incorrect Total of Cracked Ducts
The same commenter remarks that the SNPRM incorrectly states that a
total of 116 exhaust ducts have been discovered with cracks along the
affected weld seam, when in fact, to date the actual number of cracked
ducts found with cracks is 18.
The FAA agrees. However, since the questionable statement does not
appear in the preamble of a final rule, no change needs to be made to
the final rule.
Request to Exclude Single Port Exhaust Duct
One commenter requests that the single port exhaust duct, P/N
3112171-01 and subsequently any reference to the PT6A-114 and PT61-114A
engine models be excluded from the AD. For conversion of single port
exhaust ducts, part number (P/N) 3112171-01, welding is done in a much
different fashion. The original inner cone remains in place and the
majority of it is untouched. Only a small portion of its free end is
removed for the attachment of a cover. No welding is performed anywhere
on or near the load bearing outer skin. The original junction between
the outer skin and the inner cone is entirely undisturbed so adhesion
between the propeller reduction gearbox flange and the outer skin is
entirely unaffected and the load path is uncompromised.
The FAA agrees. The FAA has consulted with P&WC and has confirmed
that the commenter is correct. The inner skin replacement is performed
differently on a single port duct than on the dual duct. No welding is
done in the ``A'' flange area for the -114 series. It was the welding
at the ``A'' flange that triggered the original TC AD. There have been
no reports of cracks or poor welds on the-114 models. P&WC has revised
the-114 manuals to clearly state that the ``A'' flange is to be
examined in detail at aircraft minor (150 hours) inspections and at hot
section inspection. The PT6A-114 and PT6A-114A engines have been
incorrectly included in the proposal. Therefore, models-114 and -114A,
and exhaust duct P/N 3112171-01 are removed from the final rule.
After careful review of the available data, including the comments
noted above, the FAA has determined that air safety and the public
interest require the adoption of the rule with the changes described
previously. The FAA has determined that these changes will neither
increase the economic burden on any operator nor increase the scope of
the AD.
Economic Analysis
There are approximately 22,000 Pratt & Whitney Canada PT6A series
turboprop engines of the affected design in the worldwide fleet. The
FAA estimates that 7,000 engines installed on airplanes of U.S.
registry will be affected by this AD, that it will take approximately 2
work hours per engine to perform the required actions, and that the
average labor rate is $60 per work hour. Based on these figures, the
total cost of the AD to U.S. operators is estimated to be $840,000.
Regulatory Analysis
This final rule does not have federalism implications, as defined
in Executive Order 13132, because it would not have a substantial
direct effect on the States, on the relationship between the national
government and the States, or on the distribution of power and
responsibilities among the various levels of government. Accordingly,
the FAA has not consulted with state authorities prior to publication
of this final rule.
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 the DOT Regulatory Policies and
Procedures (44 FR 11034, February 26, 1979); and (3) will not have a
significant economic impact, positive or negative, on a substantial
number of small entities under the criteria of the Regulatory
[[Page 70690]]
Flexibility Act. A final evaluation has been prepared for this action
and it is contained in the Rules Docket. A copy of it may be obtained
by contacting the Rules Docket at the location provided under the
caption ADDRESSES.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration amends part 39 of
the Federal Aviation Regulations (14 CFR part 39) as follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding a new airworthiness directive
to read as follows:
2002-23-13 Pratt & Whitney Canada: Amendment 39-12957. Docket No.
99-NE-44-AD.
Applicability: This airworthiness directive (AD) is applicable
to Pratt & Whitney Canada (P&WC) PT6A series turboprop engines, with
turbine exhaust ducts part number (P/N) 3012290, P/N 3031988, P/N
3032117, P/N 3035784, P/N 3035786, P/N 3105890-01, P/N 3112167-01,
and P/N 3111780-01. These engines are installed on, but not limited
to, Beechcraft King Air-90 and-100 series, Bombardier DHC-6 series,
Empresa Brasileira de Aeronautica, S.A. (Embraer) EMB-110 series,
Pilatus PC-6 series, and Piper PA-42 series airplanes.
Note 1: This AD applies to each engine 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 engines 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 (g) 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: Compliance with this AD is required as indicated,
unless already done.
To prevent failure of the turbine exhaust duct due to cracking
that could result in possible separation of the reduction gearbox
and propeller from the engine, and possible loss of control of the
airplane, do the following:
Inspection of Turbine Exhaust Ducts for Low-Quality Welds
(a) If the engine has not yet been overhauled, and if the
turbine exhaust duct has not yet been subject to a shop visit for
repair, no further action is required.
(b) Otherwise, at the next shop visit or within 150 hours time-
in-service (TIS) after the effective date of this AD, whichever
occurs first, do the following:
(1) Inspect for low-quality welds created during repair, on the
turbine exhaust duct near flange ``A'', in accordance with
paragraphs 3B through 3E of P&WC service bulletin (SB) No. PT6A-72-
1610, Revision 2, dated October 1, 2002, for models PT6A-6, -6A, -
6B, -20, -20A, -20B, -21, -25, -25A, -25C, -27, -28, -34, -34AG, -
34B, -36, -135, and -135A engines, and SB No. PT6A-72-12173, dated
January 24, 2002, for models PT6A-11, -11AG, -15AG, -110, and -112
engines.
(2) If it is determined that the welds meet the acceptable
criteria specified in SB No. PT6A-72-1610, Revision 2, dated October
1, 2002; or SB No. PT6A-72-12173, dated January 24, 2002, continue
using the duct until the next scheduled overhaul. Inspect duct per
the engine overhaul manual before reinstallation.
(3) If it is determined that the welds do not meet the
acceptable criteria specified in SB No. PT6A-72-1610, Revision 2,
dated October 1, 2002; or SB No. PT6A-72-12173, dated January 24,
2002, replace the duct with a serviceable part, or perform the
initial and repetitive inspections in the following paragraphs.
Initial Visual Inspection of Welds That Do Not Meet SB Acceptable
Criteria
(c) Use 5X magnification to visually inspect the circumference
of the forward area of the exhaust duct from the propeller reduction
gearbox mounting flange to 2 inches aft of the flange for any crack
indications. Mark and record cracks and return the duct to service,
or replace with a serviceable part as follows:
(1) If no cracks are found, the duct may be returned to service;
or
(2) If three or less cracks are found, and the total cumulative
length of the cracks exceeds 2.0 inches, replace the duct with a
serviceable part; or
(3) If any one crack exceeds 1.0 inch in length, replace the
duct with a serviceable part; or
(4) If any two cracks are separated by less than six times the
length of the longest crack (6L) or 3.0 inches or less, whichever is
the closest separation, replace the duct with a serviceable part; or
(5) If more than three cracks are found, replace the duct with a
serviceable part; and
(6) Mark all allowable cracks, on the duct, with suitable metal
marking material; and
Note 2: Marking materials that are suitable for use on the
exhaust duct may be found in the P&WC Engine Manual.
(7) Record the length of the crack, location, number of duct
hours, and time-since-overhaul (TSO).
Repetitive Visual Inspection of Welds That Do Not Meet SB Acceptable
Criteria
(d) Repeat the inspection specified in paragraph (c) of this AD
as follows:
(1) For ducts that did not exhibit any cracking at the last
inspection, repeat the inspection within 150 hours TIS since the
last inspection. Return the duct to service or replace with a
serviceable part as specified in paragraph (c)(1) through paragraph
(c)(5) of this AD.
(2) For ducts that exhibited cracking at the last inspection,
repeat the inspection within 25 hours TIS since the last inspection.
Return the duct to service or replace with a serviceable part as
follows:
(i) Inspect for new cracks, and cracks that were recorded as
specified in paragraph (c) of this AD. Return the duct to service or
replace with a serviceable part as specified in paragraph (c)(1)
through paragraph (c)(5) of this AD.
(ii) In addition, if the growth rate of an existing crack
exceeds 0.015 inch per hour TIS since the last inspection, replace
the duct with a serviceable part.
Optional Terminating Action
(e) Replacing an affected exhaust duct with a serviceable
exhaust duct constitutes terminating action for the repetitive
inspection requirements of this AD.
Definition of a Serviceable Exhaust Duct
(f) For the purposes of this AD, a serviceable duct is defined
as a duct that meets the acceptability limits of this AD.
Alternative Method of Compliance
(g) An alternative method of compliance or adjustment of the
compliance time that provides an acceptable level of safety may be
used if approved by the Manager, Engine Certification Office (ECO).
Operators must submit their requests through an appropriate FAA
Principal Maintenance Inspector, who may add comments and then send
it to the ECO.
Note 3: Information concerning the existence of approved
alternative methods of compliance with this airworthiness directive,
if any, may be obtained from the ECO.
Special Flight Permits
(h) Special flight permits are not allowed.
Documents That Have Been Incorporated By Reference
(i) The inspections must be done in accordance with the
following Pratt & Whitney Canada (P&WC) service bulletins:
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Document No. Pages Revision Date
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PT6A-72-1610....................... All.................. 2.................... October 1, 2002.
[[Page 70691]]
Total Pages: 10
PT6A-72-12173...................... All.................. Original............. January 24, 2002.
Total pages: 9
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This incorporation by reference was approved by the Director of
the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR
part 51. Copies may be obtained from Pratt & Whitney Canada, 1000
Marie-Victorin, Longueuil, Quebec, Canada J4G1A1. Copies may be
inspected at the FAA, New England Region, Office of the Regional
Counsel, 12 New England Executive Park, Burlington, MA; or at the
Office of the Federal Register, 800 North Capitol Street, NW., suite
700, Washington, DC.
Note 4: The subject of this AD is addressed in AD CF-98-41 in
order to assure the airworthiness of these P&WC PT6A series
turboprop engines in Canada.
Effective Date
(j) This amendment becomes effective on December 31, 2002.
Issued in Burlington, Massachusetts, on November 15, 2002.
Mark C. Fulmer,
Acting Manager, Engine and Propeller Directorate, Aircraft
Certification Service.
[FR Doc. 02-29671 Filed 11-25-02; 8:45 am]
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