[Federal Register Volume 67, Number 111 (Monday, June 10, 2002)]
[Proposed Rules]
[Pages 39640-39642]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-14251]



[[Page 39640]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NE-44-AD]
RIN 2120-AA64


Airworthiness Directives; Pratt & Whitney Canada PT6A Series 
Turboprop Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Supplemental notice of proposed rulemaking; reopening of 
comment period.

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SUMMARY: This action revises an earlier proposed airworthiness 
directive (AD), applicable to Pratt & Whitney Canada PT6A series 
turboprop engines, that have certain turbine exhaust ducts that were 
modified by Standard Aero Limited (SAL) of Winnipeg, Canada before 
September 1, 1997. That proposal would have required initial and 
repetitive inspections for cracks and, if necessary, replacing the 
turbine exhaust duct if the cracks exceed allowable limits. That 
proposal was prompted by reports of cracks along the weld seams of 
certain turbine exhaust ducts. This action revises the proposed rule by 
requiring inspections for low-quality welds and cracks, of a larger 
population of turbine exhaust ducts than those modified by SAL. The 
actions specified by this proposed 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: Comments must be received by August 9, 2002.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Regional 
Counsel, Attention: Rules Docket No. 99-NE-44-AD, 12 New England 
Executive Park, Burlington, MA 01803-5299. Comments may be inspected at 
this location, by appointment, between 8 a.m. and 4:30 p.m., Monday 
through Friday, except Federal holidays. Comments may also be sent via 
the Internet using the following address: ``[email protected].'' 
Comments sent via the Internet must contain the docket number in the 
subject line. The service information referenced in the proposed rule 
may be obtained from Pratt & Whitney Canada, 1000 Marie-Victorin, 
Longueuil, Quebec, Canada J4G1A1. This information may be examined, by 
appointment, at the FAA, New England Region, Office of the Regional 
Counsel, 12 New England Executive Park, Burlington, MA.

FOR FURTHER INFORMATION CONTACT: James Lawrence, Aerospace Engineer, 
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:

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. 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 action 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 summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this action must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 99-NE-44-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRM's

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, New England Region, Office of the Regional Counsel, 
Attention: Rules Docket No. 99-NE-44-AD, 12 New England Executive Park, 
Burlington, MA 01803-5299.

Discussion

    A proposal to amend part 39 of the Federal Aviation Regulations (14 
CFR part 39) to add an airworthiness directive (AD), applicable to 
Pratt & Whitney Canada 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, P/N 3112171-01, 
and P/N 3111780-01, was published as a notice of proposed rulemaking 
(NPRM) in the Federal Register on December 8, 1999 (64 FR 68640). That 
proposal would have required initial and repetitive inspections for 
cracks of certain turbine exhaust ducts, and, if necessary, replacing 
the duct if the cracks exceed allowable limits. That proposal was 
prompted by reports of cracks along the weld seams of certain turbine 
exhaust ducts that were modified by Standard Aero Limited (SAL) of 
Winnipeg, Canada, before September 1, 1997. Transport Canada, which is 
the airworthiness authority for Canada, notified the FAA that an unsafe 
condition may exist on Pratt & Whitney Canada (P&WC) PT6A series 
turboprop engines. Transport Canada advised the FAA that certain part 
numbers of exhaust ducts were modified before September 1, 1997, by 
Standard Aero Limited (SAL) of Winnipeg, Canada, using an alternate gas 
tungsten arc welding (GTAW) process instead of the resistance (seam or 
stitch) weld process that was specified in P&WC service bulletin (SB) 
1430. Some of those ducts have experienced cracking that may be 
attributed to the GTAW process. Transport Canada issued AD CF-98-41 on 
November 26, 1998, in order to assure the airworthiness of these P&WC 
PT6A series turboprop engines in Canada. 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.
    Since the issuance of that proposal, further investigation by the 
FAA has determined that a number of additional companies have used the 
same GTAW process as SAL. As a result, the affected population of 
turbine exhaust ducts has expanded. Therefore, this proposal is no 
longer confined to turbine exhaust ducts modified by SAL, and is 
expanded to include the entire affected duct population. This proposal 
differs from Transport Canada AD CF 98-41. That AD is confined to SAL 
modified turbine exhaust ducts only. A total of 116 turbine exhaust 
ducts have been discovered with cracks along the affected weld seam. 
Since these changes expand the scope of the originally proposed rule, 
the FAA has determined that it is necessary to reopen the comment 
period to provide additional opportunity for public comment.

Manufacturer's Service Information

    Pratt & Whitney Canada has issued Service Bulletin (SB) No. PT6A-
72-1610, dated January 24, 2002, and SB

[[Page 39641]]

No. PT6A-72-12173, dated January 24, 2002, that specify procedures for 
inspection of turbine exhaust duct weld seams for low-quality welds 
created during repair, initial and repetitive inspections of affected 
ducts for cracks, and serviceable turbine exhaust duct criteria.

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.

Proposed Requirements of this AD

    Since an unsafe condition has been identified that is likely to 
exist or develop on other PT6A series engines of the same type design 
registered in the United States, this proposal requires:
     At the next shop visit or within 150 hours time-in-service 
after the effective date of the AD, inspection for low-quality welds 
created during repair on turbine exhaust ducts near flange ``A''.
     Initial and repetitive inspections for cracks of affected 
exhaust ducts.
    The actions would be required to be done in accordance with the 
SB's described previously.

Economic Analysis

    There are approximately 22,000 engines of the affected design in 
the worldwide fleet. The FAA estimates that 7,000 engines would be 
affected by this proposed AD, that it would take approximately 2 work 
hours per engine to do one inspection, and that the average labor rate 
is $60 per work hour. Based on these figures, the total cost of the 
proposed AD on U.S. operators for one inspection is estimated to be 
$840,000.

Regulatory Analysis

    This proposed 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 proposed rule. For the reasons discussed above, I 
certify that this proposed regulation (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) if promulgated, will not have 
a significant economic impact, positive or negative, on a substantial 
number of small entities under the criteria of the Regulatory 
Flexibility Act. A copy of the draft regulatory evaluation prepared for 
this action 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, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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 the following new 
airworthiness directive:

Pratt & Whitney Canada: 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, P/N 
3112171-01, and P/N 3111780-01. These engines are installed on, but 
not limited to, Beechcraft King Air-90 and -100 series, Bombadier 
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, dated January 24, 2002, for models PT6A-6, -6A, -6B, -20, -
20A, -20B, -21, -25, -25A, -25C, -27, -28, -34, -34AG, -34B, -36, -
114, -114A, -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, dated January 24, 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, dated January 
24, 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 inches 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

[[Page 39642]]

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 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 part 
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.

    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.


    Issued in Burlington, Massachusetts, on May 30, 2002.
Mark C. Fulmer,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 02-14251 Filed 6-7-02; 8:45 am]
BILLING CODE 4910-13-P