Airworthiness Directives; Pratt & Whitney Canada Model PT6A-67D Turboprop Engines

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 93-ANE-53; Amendment 39-8909; AD 94-10-02]

Airworthiness Directives; Pratt & Whitney Canada Model PT6A-67D

Turboprop Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment supersedes an existing priority letter

airworthiness directive (AD), applicable to Pratt & Whitney Canada

(PWC) PT6A-67D turboprop engines, that currently requires inspections

of the compressor turbine (CT) disk and blades for cracking and other

irregularities using visual inspections and fluorescent penetrant

inspections (FPI). That AD also requires amending the Beech Model 1900D

Airplane Flight Manual (AFM) and installing a placard that alerts the

pilot of this requirement. This amendment continues all the

requirements of the current priority letter AD and requires the

installation of parts having an improved design including a CT stator

assembly, a CT shroud housing, CT turbine blades, feather seals, and a

small exit duct assembly. This amendment is prompted by the

manufacturer developing new design improvements that will reduce the

susceptibility of the CT blades to high cycle fatigue (HCF) damage. The

actions specified by this AD are intended to prevent engine failure and

inflight engine shutdown due to HCF failure of the CT blades.

DATES: Effective June 15, 1994.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of June 15, 1994.

ADDRESSES: The service information referenced in this AD may be

obtained from Pratt & Whitney Canada, 1000 Marie-Victorin, Longueil,

Quebec, Canada J4G 1A1. This information may be examined at the Federal

Aviation Administration (FAA), New England Region, Office of the

Assistant Chief Counsel, 12 New England Executive Park, Burlington, MA

01803-5299; or at the Office of the Federal Register, 800 North Capitol

Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Mark A. Rumizen, Aerospace Engineer,

Engine Certification Office, FAA, Engine and Propeller Directorate, 12

New England Executive Park, Burlington, MA 01803-5299; telephone (617)

238-7137, fax (617) 238-7199.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal

Aviation Regulations by superseding priority letter airworthiness

directive (AD) 92-27-19, which is applicable to Pratt & Whitney Canada

(PWC) PT6A-67D turboprop engines, was published in the Federal Register

on November 26, 1993 (58 FR 62296). That action proposed to retain the

inspections and Airplane Flight Manual (AFM) revisions required by the

current AD, but would also require installation at the next shop visit

after the effective date of this AD, or December 31, 1994, whichever

occurs first, of the improved compressor turbine (CT) turbine stator

assembly, CT shroud housing, small exit duct assembly, CT blades, and

feather seals. Installation of this hardware constitutes terminating

action to the inspections required by this AD. PWC has advised the FAA

that December 31, 1994, is the earliest compliance end-date possible

due to parts availability. The actions are required to be accomplished

in accordance with PWC Service Bulletin (SB) No. 14128, Revision 3,

dated April 19, 1993; PWC SB No. 14132, Revision 1, dated May 12, 1993;

and PWC SB 14142, Revision 1, dated May 12, 1993. Transport Canada,

which is the airworthiness authority of Canada, classified these

service bulletins as mandatory and issued AD CF-92-25-R1, dated June 1,

1993, in order to assure the airworthiness of these PWC PT6A-67D

engines in Canada.

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 and the applicable

bilateral airworthiness agreement. Pursuant to this bilateral

airworthiness agreement, Transport Canada has kept the FAA informed of

the situation described above. The FAA has examined the findings of

Transport Canada, 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.

Interested persons have been afforded an opportunity to participate

in the making of this amendment. Due consideration has been given to

the comment received.

The commenter concurs with the rule as proposed.

After careful review of the available data, including the comment

noted above, the FAA has determined that air safety and the public

interest require the adoption of the rule as proposed.

There are approximately 100 engines of the affected design in the

worldwide fleet. The FAA estimates that 87 engines installed on

aircraft of U.S. registry will be affected by this AD, that it will

take approximately 40 work hours per engine to install the improved

hardware, and that the average labor rate is $55 per work hour. PWC

advises the FAA that it will reimburse operators for the cost of labor

and the cost of required parts. Based on these figures, the total cost

impact of the AD on U.S. operators is estimated to be negligible.

The regulations adopted herein will 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 final

rule does 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) 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 final evaluation has been prepared for this action

and it is contained in the Rules Docket. A copy of it may be obtained

from 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 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. App. 1354(a), 1421 and 1423; 49 U.S.C.

106(g); and 14 CFR 11.89.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

94-10-02 Pratt & Whitney Canada: Amendment 39-8909 Docket 93-ANE-

53.

Applicability: Pratt & Whitney Canada (PWC) Model PT6A-67D

turboprop engines with serial numbers prior to PC-E114100, installed

on but not limited to Beech Model 1900D airplanes.

Compliance: Required as indicated, unless accomplished

previously.

To prevent engine failure and inflight engine shutdown due to

high cycle fatigue (HCF) failure of the compressor turbine (CT)

blades, accomplish the following:

(a) Prior to further flight, amend the Beech Model 1900D

Aircraft Flight Manual (AFM), Part Number (P/N) 129-590000-3, by

inserting the following requirements between pages 2-4 and 2-5:

ENGINE OPERATING LIMITATIONS

Gas Generator RPM (N1)--Continuous operation of the gas

generator between 94.0% and 97.1% is prohibited.

Notes

1. This limitation does not prohibit the use of N1's between

94.0% and 97.1% when the pilot in command determines that the power

setting is required for the safe operation of the airplane. If such

occurrences exceed 5 minutes, the engine(s) must be inspected in

accordance with Pratt & Whitney Canada Service Bulletin No. 14128,

Revision 3, dated April 19, 1993.

2. This limitation does not prohibit the use of static Take-Off

Power and Maximum Continuous Power between 94.0% and 97.1% N1 to

meet the required Take-Off performance. If such occurrences exceed 5

minutes, the engine(s) must be inspected in accordance with Pratt &

Whitney Canada Service Bulletin No. 14128, Revision 3, dated April

19, 1993.

3. Operation at 94.0% and below, and at 97.1% and above are

permitted. Continuous operation at 94.1% through 97.0% is

prohibited.

4. ``Continuous Operation'' means time periods exceeding 5

minutes.

5. High Speed Cruise Power Tables found in the Pilot's Operating

Manual may produce N1's in the prohibited range. Flights should be

planned using Intermediate or Long Range Power settings.

6. The goal of the operator should be to keep the total time of

operation in the prohibited range to the absolute minimum, since the

effects of operating between N1's of 94.0% and 97.1% are cumulative.

PLACARDS

Located in front of the pilot on the aft edge of the glareshield

between the Master Caution annunciator and the fire extinguisher

control switch:

CONTINUOUS OPERATION BETWEEN 94.0% AND 97.1% N1 IS PROHIBITED--SEE

AFM''

(b) Compliance with the requirements of paragraph (a) of this AD

may also be accomplished by inserting a copy of this AD into the

Beech Model 1900D AFM.

(c) Prior to further flight, install the placard as specified in

paragraph (a) of this AD.

(d) For engines that have not been inspected prior to the

effective date of this AD in accordance with PWC SB No. 14128,

Revision 1, dated November 13, 1992, or debladed and inspected in

accordance with PWC SB No. 14128, Revision 2, dated December 22,

1992, or PWC SB No. 14128, Revision 3, dated April 19, 1993,

accomplish the following:

(1) For engines with Serial Numbers PC-E114001 to PC-E114044,

within 25 hours time in service (TIS) after the effective date of

this AD, deblade the CT disk, inspect the entire disk surface area

and fir tree area of the CT blades for cracking and the trailing

edge of the blade airfoil section for irregularities, and replace,

if necessary, with serviceable parts, in accordance with the

Accomplishment Instructions of PWC SB No. 14128, Revision 3, dated

April 19, 1993.

(2) For engines with Serial Numbers PC-E114045 to PC-E114099,

within 50 hours TIS after the effective date of this AD, deblade the

CT disk, inspect the entire disk surface area and fir tree area of

the CT blades for cracking, and replace, if necessary, with

serviceable parts, in accordance with the Accomplishment

Instructions of PWC SB No. 14128, Revision 3, dated April 19, 1993.

(e) For engines that have been inspected in accordance with PWC

SB No. 14128, Revision 1, dated November 13, 1992, prior to the

effective date of this AD, deblade the CT disk, inspect the entire

disk surface area and fir tree area of the CT blades for cracking,

and replace, if necessary, with serviceable parts, in accordance

with the Accomplishment Instructions of PWC SB No. 14128, Revision

3, dated April 19, 1993, as follows:

(1) For blade sets with greater than 600 hours TIS since new on

the effective date of this AD, deblade, inspect, and replace, if

necessary, within the next 50 hours TIS.

(2) For blade sets with greater than or equal to 250 hours TIS,

and less than or equal to 600 hours TIS, since new, on the effective

date of this AD, deblade, inspect, and replace, if necessary, within

the next 100 hours TIS.

(3) For blade sets with less than 250 hours TIS since new on the

effective date of this AD, deblade, inspect, and replace, if

necessary, within the next 250 hours TIS.

(f) For uninstalled CT disk and blade assemblies that have not

been inspected in accordance with the Accomplishment Instructions of

PWC SB No. 14128, Revision 2, dated December 22, 1992, or PWC SB No.

14128, Revision 3, dated April 19, 1993, in the preceding 250 hours

TIS from the effective date of this AD, deblade the CT disk, inspect

the entire disk surface area and fir tree area of CT blades for

cracking, and replace, if necessary, with serviceable parts, in

accordance with the Accomplishment Instructions of PWC SB No. 14128,

Revision 3, dated April 19, 1993, prior to installation.

(g) For engines with CT disk and blade assemblies that have been

debladed and inspected in accordance with the Accomplishment

Instructions of PWC SB No. 14128, Revision 2, dated December 22,

1992, or PWC SB No. 14128, Revision 3, dated April 19, 1993, prior

to the effective date of this AD, within 250 hours TIS since the

last deblading and inspection, deblade the CT disk, inspect the

entire disk surface area and fir tree area of CT blades for

cracking, and replace, if necessary, with serviceable parts, in

accordance with the Accomplishment Instructions of PWC SB No. 14128,

Revision 3, dated April 19, 1993.

(h) For CT disk and blade assemblies that have been debladed and

inspected in accordance with paragraphs (d), (e), (f), and (g) of

this AD, deblade the CT disk, reinspect the entire disk surface area

and fir tree area of CT blades for cracking, and replace, if

necessary, with serviceable parts, in accordance with the

Accomplishment Instructions of PWC SB No. 14128, Revision 3, dated

April 19, 1993, at intervals not to exceed 250 hours TIS since the

last deblading and inspection performed in accordance with the

Accomplishment Instructions of PWC SB No. 14128, Revision 3, dated

April 19, 1993.

(i) Install a CT stator assembly, a CT shroud housing, and a

small exit duct assembly in accordance with PWC SB No. 14132,

Revision 1, dated May 12, 1993, at the next shop visit after the

effective date of this AD, or December 31, 1994, whichever occurs

first.

(j) Install CT blades and feather seals in accordance with PWC

SB No. 14142, Revision 1, dated May 12, 1993, at the next shop visit

after the effective date of this AD, or December 31, 1994, whichever

occurs first.

(k) For the purpose of this AD, a shop visit is defined as when

major engine flanges are separated.

(l) Installation of improved hardware in accordance with

paragraphs (i) and (j) of this AD constitutes terminating action for

the inspections required by paragraphs (d) through (h) of this AD.

(m) 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. The

request should be forwarded through an appropriate FAA Principal

Maintenance Inspector, who may add comments and then send it to the

Manager, Engine Certification Office.

Note: Information concerning the existence of approved

alternative method of compliance with this AD, if any, may be

obtained from the Engine Certification Office.

(n) Special flight permits may be issued in accordance with 14

CFR 21.197 and 21.199 to operate the aircraft to a location where

the requirements of this AD can be accomplished.

(o) The inspections and modifications shall be done in

accordance with the following service bulletins:

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Document No. Pages Revision Date

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PWC SB No. 14128; Total pages: 5.......................... 1-5 3 April 19, 1993.

PWC SB No. 14132; Total pages: 6.......................... 1-6 1 May 12, 1993.

PWC SB No. 14142; Total pages: 7.......................... 1-7 1 May 12, 1993.

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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, Longueil, Quebec, Canada J4G 1A1. Copies may be

inspected at the FAA, New England Region, Office of the Assistant

Chief 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.

(p) This amendment supersedes priority letter AD 92-27-19,

issued December 28, 1992.

(q) This amendment becomes effective on June 15, 1994.

Issued in Burlington, Massachusetts, on April 29, 1994.

Jay J. Pardee,

Manager, Engine and Propeller Directorate, Aircraft Certification

Service.

[FR Doc. 94-10913 Filed 5-13-94; 8:45 am]

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