[Federal Register Volume 67, Number 228 (Tuesday, November 26, 2002)]
[Rules and Regulations]
[Pages 70688-70691]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-29671]


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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]
BILLING CODE 4910-13-P