[Federal Register Volume 64, Number 235 (Wednesday, December 8, 1999)]
[Proposed Rules]
[Pages 68640-68642]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-31816]


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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 
Turboshaft Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of 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 Standard Aero Limited (SAL) of Winnipeg, Canada before 
September 1, 1997. This proposal would

[[Page 68641]]

require initial and repetitive inspections for cracks and, if 
necessary, replacing the duct if the cracks exceed allowable limits. 
This proposal is prompted by reports of cracks along the weld seams of 
certain turbine exhaust ducts. The actions specified by the 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 February 7, 2000.

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 also be 
submitted to the Rules Docket by using the following Internet address: 
``[email protected]''. Comments may be inspected at this location 
between 8:00 a.m. and 4:30 p.m., Monday through Friday, except Federal 
holidays.

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 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 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 notice 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 NPRMs

    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

    Transport Canada (TC), which is the airworthiness authority for 
Canada, recently notified the Federal Aviation Administration (FAA) 
that an unsafe condition may exist on Pratt & Whitney Canada (P&WC) 
PT6A series turboprop engines. TC advises the FAA that certain 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 were modified before September 1, 1997, by Standard Aero 
Limited (SAL) of Winnipeg, Canada, using the alternate gas tungsten arc 
welding (GTAW) process instead of the resistance (seam or stitch) weld 
process that were specified in P&WC service bulletin (SB) 1430. Some of 
those ducts have experienced cracking that may be attributed to the 
GTAW process. TC 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.

Bilateral Airworthiness Agreement

    These engine models are manufactured in Canada and are type 
certificated for operation in the United States under the provisions of 
Sec. 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the 
applicable bilateral airworthiness agreement. Pursuant to this 
bilateral airworthiness agreement, TC has kept the FAA informed of the 
situation described above. The FAA has examined the findings of TC, has 
reviewed all available information, and has determined that AD action 
is necessary for products of this type design that are certificated for 
operation in the United States.

Requirements of this AD

    Since an unsafe condition has been identified that is likely to 
exist or develop on other PT6A series turboprop engines of the same 
type design registered in the United States, the proposed AD would 
require initial and repetitive visual inspections of certain turbine 
exhaust ducts 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, that were modified using a GTAW procedure by SAL before 
September 1, 1997.

Cost Impact

    There are approximately 22,000 engines of the affected design in 
the worldwide fleet. The FAA estimates that 7,000 engines installed on 
airplanes of U.S. registry would be affected by this proposed AD, that 
it would take approximately 2 work hours per engine to determine if an 
affected duct is installed, and that it would take approximately 20 
hours to replace an affected duct. There are approximately 116 engines 
worldwide that may have an affected duct installed, however, it is not 
known how many of those engines are installed on airplanes of U.S. 
registry. The average labor rate is $60 per work hour. Required parts 
would cost approximately $32,000 per engine. Based on these figures, 
the total cost impact of the proposed AD on U.S. operators is estimated 
to be $840,000 to determine if an affected duct is installed on an 
engine, and $3,851,200 to replace the ducts if all ducts are installed 
in engines that are installed on airplanes of U.S. registry The 
estimated total economic impact may be $4,691,200.

Regulatory Impact

    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.

[[Page 68642]]

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: Pratt & Whitney Canada (P&WC) PT6A series 
turboprop engines with certain 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, that 
were modified before September 1, 1997, by Standard Aero Limited 
(SAL) of Winnipeg, Canada. These engines are installed on, but not 
limited to, Beechcraft King Air-90 and -100 series, Bombadier DHC-6 
series, Empresa Brasielira de Aeronautica, S.A. (Embraer) EMB-110 
series, Pilatus PC-6 series, and Piper PA-42 series airplanes.

    Note 1: This airworthiness directive (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: Required as indicated, unless accomplished 
previously.
    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, accomplish the following:

Inspection of Exhaust Duct

    (a) If the exhaust duct was not modified before September 1, 
1997, by SAL of Winnipeg, Canada, using the gas tungsten arc weld 
(GTAW) process of P&WC service bulletin (SB) 1430, no further action 
is required

    Note 2: Engine log books, engine maintenance records, etc., can 
be used to determine if the duct was modified before September 1, 
1997, by SAL of Winnipeg, Canada, using the GTAW process of P&WC SB 
1430.

    (b) If the exhaust duct 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 modified before September 1, 1997 
by SAL using the GTAW process of P&WC SB 1430, or if it cannot be 
determined if the GTAW process was used in complying with P&WC SB 
1430, do the following within 100 hours time-in-service (TIS) after 
the effective date of this AD:

Initial Visual Inspection of Affected Exhaust Ducts for Cracks

    (1) 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. Return the duct to service or replace with a 
serviceable part as follows:
    (i) If no cracks are found, the duct may be returned to service. 
Or,
    (ii) 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,
    (iii) If any one crack exceeds 1.0 inches in length, replace the 
duct with a serviceable part. Or,
    (iv) If any two cracks are separated by less than six times the 
length of the longest crack (6L) or by less than 3.0 inches, 
whichever is less, replace the duct with a serviceable part. Or,
    (v) If more than three cracks are found, replace the duct with a 
serviceable part.
    (2) Mark all allowable cracks, on the duct, with a suitable 
metal marking pencil.

    Note 3: Marking materials that are suitable for use on the the 
exhaust duct may be found in the P&WC Engine Manual.

    (3) Record the length of the crack, location, number of duct 
hours, and time since overhaul (TSO).

Repetitive Visual Inspection of Affected Exhaust Ducts for Cracks

    (c) Repeat the inspection specified in paragraph (b)(1) 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 (b)(1)(i) through 
paragraph (b)(2).
    (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) For new cracks that have developed since the last 
inspection, return the duct to service or replace with a serviceable 
part as specified in paragraph (b)(1)(ii) through paragraph (b)(3).
    (ii) Inspect cracks that were recorded as specified in paragraph 
(b)(2). Return the duct to service or replace with a serviceable 
part as specified in paragraph (b)(1)(ii) through paragraph (b)(2). 
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

    (d) 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

    (e) For the purposes of this AD, a serviceable duct is defined 
as a duct that has been modified per P&WC SB 1430, but did not use 
the GTAW process.

Alternative Method of Compliance

    (f) 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 shall submit their request through an appropriate FAA 
Principal Maintenance Inspector, who may add comments and then send 
it to the Manager, ECO.

    Note 4: 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

    (g) Special flight permits may be issued in accordance with 
Sec. Sec. 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the aircraft to a location where 
the requirements of this AD can be accomplished.

    Issued in Burlington, Massachusetts, on December 1, 1999.
Thomas A. Boudreau,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 99-31816 Filed 12-7-99; 8:45 am]
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