Airworthiness Directives; Pratt & Whitney JT8D Series Turbofan Engines

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 93-ANE-83; Amendment 39-9036; AD 94-20-08]

Airworthiness Directives; Pratt & Whitney JT8D Series Turbofan

Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment supersedes an existing airworthiness directive

(AD), applicable to certain Pratt & Whitney (PW) JT8D series turbofan

engines, that currently requires initial and repetitive inspections of

installed third and fourth stage low pressure turbine (LPT) blade sets

for blade shroud crossnotch wear, and removal of blade sets found with

excessively worn blade shroud crossnotches. This amendment continues to

require inspections, and removal, if necessary, of blade sets, but also

requires, as a terminating action to the inspections: installation of

improved LPT containment hardware, and installation of an improved No.

6 bearing scavenge pump bracket bushing. This amendment is prompted by

reports of additional uncontained engine failures since publication of

the current AD, and the availability of improved LPT containment

hardware. The actions specified by this AD are intended to prevent

damage to the aircraft resulting from engine debris following an LPT

blade or shaft failure.

DATES: Effective on November 14, 1994.

The incorporation by reference of certain publications listed in

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

of November 14, 1994.

ADDRESSES: The service information referenced in this AD may be

obtained from Pratt & Whitney, 400 Main Street, East Hartford, CT

06108. 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: On May 24, 1993, the Federal Aviation

Administration (FAA) issued airworthiness directive (AD) 93-06-05,

Amendment 39-8530 (58 FR 31902, June 1, 1993), applicable to Pratt &

Whitney (PW) JT8D-1, -1A, -1B, -7, -7A, -7B, -9, -9A, -11, -15, -17,

and -17R engines, to require initial and repetitive inspections of the

third and fourth stage low pressure turbine (LPT) blade sets for

excessively worn blade shroud crossnotches, and the removal of blade

sets found with excessively worn blade crossnotches. That AD is not

applicable, however, to PW JT8D-1, -1A, -1B, -7, -7A, -7B, -9, -9A, -

11, -15, -17, and -17R engines that contain fan exhaust inner front

duct segment assemblies that are installed in accordance with PW Alert

Service Bulletin (ASB) No. 6039, Revision 2, dated May 4, 1992, or

earlier revisions of PW ASB No. 6039, and either (a) PW honeycomb third

stage outer airseal Part Number (P/N) 801931, 802097, 797594, or

798279; or (b) Pyromet Industries, Inc., honeycomb third stage outer

airseal P/N PI9336; or (c) McClain International, Inc., honeycomb third

stage outer airseal P/N M2433; or (d) a turbine case shield assembly

installed in accordance with PW ASB No. 6039, Revision 2, dated May 4,

1992, or earlier revisions of PW ASB No. 6039; or (e) a third stage

blade set that has third stage turbine blades that were installed in

accordance with PW SB No. 5331, dated October 27, 1982.

A proposal to amend part 39 of the Federal Aviation Regulations (14

CFR part 39) by superseding AD 93-06-05 was published in the Federal

Register on December 28, 1993 (58 FR 68572). That action proposed to

continue to require repetitive inspections of installed third and

fourth stage LPT blade sets for blade shroud crossnotch wear, and

removal of blade sets found with excessively worn blade shroud

crossnotches. These inspections are not required, however, for PW JT8D-

1, -1A, -1B, -7, -7A, -7B, -9, -9A, -11, -15, -17, and -17R engines

that contain fan exhaust inner front duct segment assemblies that are

installed in accordance with PW ASB No. 6039, Revision 3, dated October

15, 1993, or earlier revisions of PW ASB No. 6039, and either (a) PW

honeycomb third stage outer airseal P/N 801931, 802097, 797594, or

798279; or (b) Pyromet Industries, Inc., honeycomb third stage outer

airseal P/N PI9336; or (c) McClain International, Inc., honeycomb third

stage outer airseal P/N M2433; or (d) a turbine case shield assembly

installed in accordance with PW ASB No. 6039, Revision 3, dated October

15, 1993, or earlier revisions of PW ASB No. 6039; or (e) a third stage

blade set that has third stage turbine blades that were installed in

accordance with PW SB No. 5331, dated October 27, 1982.

That notice of proposed rulemaking (NPRM) also proposed to require,

however, for all engines, installation of improved third stage LPT

containment hardware at the next access to the third stage LPT air

sealing ring, but not later than December 31, 1998; installation of the

improved fourth stage LPT containment hardware at the next shop visit,

but not later than December 31, 1998; installation of the improved No.

6 bearing scavenge pump bracket bushing at the next shop visit, but not

later than December 31, 1998; and modification and remarking with a new

identification number third and fourth stage LPT vanes with a reduced

platform leading edge dimension at the next shop visit, but not later

than December 31, 1998. The installation of improved containment

hardware would serve as terminating action for the repetitive

inspections.

The actions would be required to be accomplished in accordance with

the following service documents: PW ASB No. A5913, Revision 6, dated

October 15, 1993, that describes the third and fourth stage LPT blade

set inspection procedures and replacement requirements; PW ASB No.

A6110, Revision 1, dated October 15, 1993, that describes procedures

for installation of improved LPT containment hardware; PW ASB No.

A6131, dated August 24, 1993, that describes procedures for

installation of an improved No. 6 bearing scavenge pump bracket

bushing; and PW SB No. 5748, Revision 5, dated August 3, 1993, that

describes procedures for removing material from the inner platform

leading edge on third and fourth stage LPT vane and vane cluster

assemblies, and remarking these modified vanes with new identification

numbers.

Interested persons have been afforded an opportunity to participate

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

the comments received.

The FAA received several comments that state that inspections and

modifications are available that address the root cause of shaft

fractures and blade failures, whereas the installation of the

containment hardware does not, and should therefore not be mandated.

The FAA does not concur. Currently available inspections and

modifications only protect against known failure modes, whereas the

containment hardware will diminish the severity of all failure modes,

both known and unknown, by protecting the aircraft from damage due to

uncontained engine debris.

The FAA received several comments that state that the FAA should

evaluate PW JT8D engine models separately to determine if all models

require the proposed actions to be accomplished, or if some models can

be exempted from compliance due to differences in design or

demonstrated operational safety. The FAA does not concur. Design

differences between the various PW JT8D engine models were evaluated

and no significant differences, other than low pressure rotor speed in

the higher rated engines, were revealed that could impact containment

capability. The increased rotor speeds are protected for in the design

of the higher rated engines with the addition of a turbine shield, and

the historical event data does not indicate that these higher low

pressure rotor speeds result in a greater number of uncontained

failures.

One commenter states that the FAA's economic analysis does not

reflect the true cost of the containment hardware. The FAA does not

concur. The intent of the economic analysis is to quantify the total

direct cost to operators of the proposed rule. The analysis does,

however, account for engines currently equipped with the required

parts, and the price for the required parts quoted in the proposed rule

is actually an average value that reflects costs for these engines.

One commenter states that the FAA's economic analysis does not

account for the increased fuel costs resulting from the added weight of

the containment hardware. The economic analysis reflects the direct

costs of performing the requirements of the AD. Since the FAA has

determined that the AD is required to correct an unsafe condition found

in engines of this type design, and, therefore, operators must perform

the requirements of the AD in order to ensure the continued

airworthiness of the engines they operate, a comparison of the costs of

operating the engine with and without the required containment hardware

would not be proper.

One commenter states that the definition of shop visit stated in

the proposed rule encompasses many types of minor or peripheral

maintenance activities where installation of the containment hardware

cannot be accomplished, thus causing a forced induction into an

overhaul facility. The FAA concurs. The shop visit definition has been

revised to address this commenter's concern.

One commenter states that the FAA's economic analysis should

account for the costs to implement AD 93-06-05 and other safety

concerns since they are directed at reducing the safety concern

addressed by the proposed rule. AD 93-06-05 requires LPT blade torque

check inspections. The FAA does not concur. The proposed rule maintains

the inspection requirements of AD 93-06-05, but only until the

installation of the containment hardware, which is ultimately required

for all engines in accordance with the compliance schedule. Therefore,

the inspections continue only as options, and only the mandated

hardware installation is used to compute the direct costs of this AD.

Further, since inspections are not mandated for engines that have

containment hardware installed, only the cost of either the inspection

or containment hardware applies for any given engine. The containment

hardware cost, the higher of the two, was used on the assumption that

an operator would install the hardware rather than continue with the

optional inspection program.

One commenter states that the modifications required by PW SB No.

5748, LPT vane cluster cut-back, are not applicable to the engine

models specified in this AD. This requirement should be eliminated from

the AD. The FAA concurs. The modification of the LPT vane clusters in

accordance with PW SB No. 5748, is not required for the ``non-A'' JT8D

engine models and therefore has been eliminated from this AD.

One commenter states that PMA 3rd stage outer air seal, Part Number

(P/N) M2533, manufactured by McClain International, should be an

acceptable alternative installation to the corresponding PW part, P/N

811962. The FAA concurs. Third stage turbine outer air seal, P/N M2533,

has been granted FAA PMA approval, and therefore meets all applicable

Federal Aviation Regulations and is directly interchangeable with PW P/

N 811962. The AD has been revised to specify PP/N M2533 as an

acceptable installation.

One commenter states that a one-year extension of the compliance

end date to December 31, 1999, should be granted. The FAA concurs. A

one-year extension of the compliance end date has been granted to

adjust for the time required to review the comments to the NPRM and

process the Final Rule.

One commenter states that only engines removed for shop visits on

or after the AD effective date will be required to comply with the AD,

and therefore AD compliance would not be required for engines already

undergoing a shop visit as of the AD effective date. The FAA concurs,

but no revision of the AD is required because the wording in the

proposed rule accounts for this situation.

One commenter states that the compliance requirements should be

revised to minimize economic impact due to major engine disassembly.

Specifically, modification of the LPT vane cluster assemblies and

installation of the No. 6 bearing scavenge pump bracket bushing could

entail major engine disassembly depending on the scope of work

performed at the next shop visit occurring after the effective date of

the AD. The FAA concurs in part. The FAA has determined that the

modification of the LPT vane cluster assemblies is not applicable to

the engine models specified in this AD, and therefore has eliminated

this requirement. However, the compliance requirements for the

installation of the No. 6 bearing scavenge pump bracket bushing is

still required at the next shop visit to achieve the desired level of

safety.

One commenter states that additional costs could be incurred due to

lack of availability of the parts required by this AD. The FAA does not

concur. The FAA has coordinated this AD closely with PW to ensure the

availability of the required parts. In addition, PMA parts are

specified in this AD as an acceptable alternative for PW parts.

One commenter states that the -15A/-17A models were the only engine

group to have the initial steel duct modification incorporated during

manufacture in accordance with PW SB No. 5697. These engines, together

with a limited number of retrofitted engines, will be the only ones

able to take advantage of the associated industry support program. The

FAA has no comment on the extent or application of any support program

which may offset some of the costs of the hardware required by this

airworthiness directive. While some operators may receive discounts on

the cost of the containment hardware, the economic analysis is computed

on the assumption that no discount or warranty program is available.

Therefore, this comment is beyond the scope of the AD or its economic

analysis.

One commenter states that an alternative to the compliance end date

of December 31, 1998, should be expressed in hours and cycles, with

performance required as whichever occur later, to accommodate low

utilization operators. The FAA concurs. The FAA performed a risk

analysis to determine the inspection interval requirements and that

risk analysis accounted for both high and low utilization operations.

However, determining the hourly and cyclic equivalent to the compliance

end date specified in the AD, the FAA has determined that the fleet

average utilization rate can be applied to low utilization operators.

The FAA has added the hourly and cyclic equivalents to the AD.

One commenter states the PW JT8D-17R engines should be exempted

from the requirement to install the thicker third stage turbine outer

air seal because these engines are already configured with a turbine

shield for containment protection. The FAA does not concur. The PW

JT8D-17R engines require additional containment protection due to

higher rated low pressure rotor speeds on these engine models.

Therefore, both the thicker third stage turbine outer air seal and the

turbine shield are required for these engine models.

One commenter concurs with the rule as proposed.

In addition, the FAA has determined that inspections of the third

and fourth stage LPT blade sets in accordance with the procedures and

intervals described in PW ASB No. 5913, Revision 5, dated August 10,

1992; or PW ASB No. 5913, Revision 4, dated February 20, 1992,

constitute acceptable alternative methods of compliance for the

inspections required by paragraphs (a)(1) and (a)(1)(iii) of this AD.

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.

The FAA estimates that 6,000 engines installed on aircraft of U.S.

registry will be affected by this AD, that it will take an average of 4

work hours, based on fleet configuration mix, per engine to accomplish

the required actions, and that the average labor rate is $55 per work

hour. Required parts will cost approximately $7,235 per engine. Based

on these figures, the total cost impact of the AD on U.S. operators is

estimated to be $44,730,000.

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 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. 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 removing Amendment 39-8530 (58 FR

31902, June 7, 1993) and by adding a new airworthiness directive,

Amendment 39-9036, to read as follows:

94-20-08 Pratt & Whitney: Amendment 39-9036. Docket No. 93-ANE-83.

Supersedes AD 93-06-05, Amendment 39-8530.

Applicability: Pratt & Whitney (PW) JT8D-1, -1A, -1B, -7, -7A, -

7B, -9, -9A, -11, -15, -17, and -17R turbofan engines, installed on

but not limited to Boeing 737 and 727 series aircraft, and McDonnell

Douglas DC-9 series aircraft.

Compliance: Required as indicated, unless accomplished

previously.

To prevent damage to the aircraft resulting from engine debris

following a low pressure turbine (LPT) blade or shaft failure,

accomplish the following:

(a) For engines that do not contain fan exhaust inner front duct

segment assemblies that are installed in accordance with PW Alert

Service Bulletin (ASB) No. 6039, Revision 3, dated October 15, 1993,

or earlier revisions of PW ASB No. 6039, and either PW honeycomb

third stage outer airseal Part Number (P/N) 801931, 802097, 797594,

or 798279; or Pyromet Industries, Inc., honeycomb third stage outer

airseal P/N PI9336; or McClain International, Inc., honeycomb third

stage outer airseal P/N M2433; or a turbine case shield assembly

installed in accordance with PW ASB No. 6039, Revision 3, dated

October 15, 1993, or earlier revisions of PW ASB No. 6039; or a

third stage blade set that has third stage turbine blades that were

installed in accordance with PW SB No. 5331, dated October 27, 1982,

accomplish the following:

(1) Conduct initial and repetitive inspections on installed

third and fourth stage LPT blade sets, and remove and replace with

serviceable blade sets, as necessary, in accordance with Part 1 of

the Accomplishment Instructions of PW ASB No. A5913, Revision 6,

dated October 15, 1993; or PW ASB No. 5913, Revision 5, dated August

10, 1992; or PW ASB No. 5913, Revision 4, dated February 20, 1992,

as follows:

(i) Initially inspect the blade shroud crossnotches of the third

stage LPT blade set when specified in paragraphs (a)(1)(i)(A) or

(a)(1)(i)(B) of this AD, whichever occurs later. Engines that

contain a third stage blade set that have third stage turbine blades

that were installed per the requirements specified in PW Service

Bulletin No. 5331, dated October 27, 1982, do not require the third

stage blade set inspection.

(A) Inspect within 6,000 cycles or 6,000 hours time in service,

whichever occurs first, since new, since the last blade shroud

crossnotch inspection specified in Section 72-53-12 of PW JT8D

Engine Manual P/N 481672, or since last blade shroud crossnotch

repair that was accomplished per the requirements specified in

Section 72-53-12 of PW JT8D Engine Manual P/N 481672; or

(B) Inspect within 1,000 cycles or 1,000 hours time in service,

whichever occurs first, after the effective date of this AD.

(ii) Initially inspect the blade shroud crossnotches of the

fourth stage LPT blade set when specified in paragraph (a)(1)(ii)(A)

or (a)(1)(ii)(B) of this AD, whichever occurs later. Engines that

contain fan exhaust inner front duct segment assemblies that were

installed per the requirements of PW ASB No. 6039, Revision 3, dated

October 15, 1993, or earlier revisions of PW ASB No. 6039, do not

require the fourth stage blade set inspection.

(A) Inspect within 6,000 cycles or 6,000 hours time in service,

whichever occurs first, since new, since the last blade shroud

crossnotch inspection specified in Section 72-53-13 of PW JT8D

Engine Manual P/N 481672, or since last blade shroud crossnotch

repair that was accomplished per the requirements specified in

Section 72-53-13 of PW JT8D Engine Manual P/N 481672; or

(B) Inspect within 1,000 cycles or 1,000 hours time in service,

whichever occurs first, after the effective date of this AD.

(iii) Thereafter, inspect the third and fourth stage LPT blade

sets in accordance with the procedures and intervals specified in PW

ASB No. A5913, Revision 6, dated October 15, 1993;

(2) At the next shop visit after the effective date of this AD;

but not later than December 31, 1999, 8,000 hours time in service

after the effective date of this AD, or 7,000 cycles after the

effective date of this AD, whichever occurs latest, install the

improved inner front fan exhaust duct and associated hardware in

accordance with Part A of the Accomplishment Instructions of PW ASB

No. A6110, Revision 1, dated October 15, 1993.

(3) At the next access to the third stage turbine air sealing

ring after the effective date of this AD, but not later than

December 31, 1999, 8,000 hours time in service after the effective

date of this AD, or 7,000 cycles after the effective date of this

AD, whichever occurs latest, install the improved third stage

turbine air sealing ring and associated hardware in accordance with

Part B of the Accomplishment Instructions of PW ASB No. A6110,

Revision 1, dated October 15, 1993.

Note: Third stage turbine outer air seal, P/N M2533, is an

acceptable alternative to PW P/N 811962 for compliance with this

paragraph.

(4) At the next shop visit after the effective date of this AD,

but not later than December 31, 1999, 8,000 hours time in service

after the effective date of this AD, or 7,000 cycles after the

effective date of this AD, whichever occurs latest, install the

improved No. 6 bearing scavenge pump bracket bushing in accordance

with the Accomplishment Instructions of PW ASB No. A6131, dated

August 24, 1993.

(5) Accomplishment of the installations required by paragraphs

(a)(2), (a)(3), and (a)(4) of this AD constitutes terminating action

to the repetitive inspections required by paragraph (a)(1) of this

AD.

(b) For engines that do contain fan exhaust inner front duct

segment assemblies that are installed in accordance with PW ASB No.

6039, Revision 3, dated October 15, 1993, or earlier revisions of PW

ASB No. 6039, and either PW honeycomb third stage outer airseal P/N

801931, 802097, 797594, or 798279; or Pyromet Industries, Inc.,

honeycomb third stage outer airseal P/N PI9336; or McClain

International, Inc., honeycomb third stage outer airseal P/N M2433;

or a turbine case shield assembly installed in accordance with PW

ASB No. 6039, Revision 3, dated October 15, 1993, or earlier

revisions of PW ASB No. 6039; or a third stage blade set that has

third stage turbine blades that were installed in accordance with PW

SB No. 5331, dated October 27, 1982, perform the installations

required by paragraphs (a)(2), (a)(3), and (a)(4) of this AD, at the

times specified in those respective paragraphs.

(c) For the purpose of this AD, a shop visit is defined as an

engine removal, where engine maintenance entails separation of pairs

of major mating engine flanges or the removal of a disk, hub, or

spool at a maintenance facility that is capable of compliance with

the instructions of this AD, regardless of other planned

maintenance, except for field maintenance type activities performed

at this maintenance facility in lieu of performing them on-wing or

at another peripheral facility.

(d) 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.

(e) Special flight permits may be issued in accordance with

sections 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.

(f) The installations shall be done in accordance with the

following service documents:

------------------------------------------------------------------------

Document No. Pages Revision Date

------------------------------------------------------------------------

PW ASB No. A5913........ 1 6........... October 15, 1993.

2 4........... February 20, 1992.

3-8 6........... October 15, 1993.

9 4........... February 20, 1992.

10 6........... October 15, 1993.

11 4........... February 20, 1992.

12 6........... October 15, 1993.

Appendix A.............. 1 6........... October 15, 1993.

2-3 5........... August 10, 1992.

4 2........... September 28, 1990.

5 6........... October 15, 1993.

6 Original.... April 2, 1990.

7 2........... September 28, 1990.

8-14 Original.... April 2, 1990.

Total pages: 26.

PW ASB No. A6110........ 1 1........... October 15, 1993.

2 Original.... March 19, 1993.

3-59 1........... October 15, 1993.

Total pages: 59.

PW ASB No. A6131........ 1-13 Original.... August 24, 1993.

Total pages: 13.

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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, 400 Main

Street, East Hartford, CT 06108. 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.

(g) This amendment becomes effective on November 14, 1994.

Issued in Burlington, Massachusetts, on September 22, 1994.

Mark C. Fulmer,

Acting Manager, Engine and Propeller Directorate, Aircraft

Certification Service.

[FR Doc. 94-24200 Filed 10-12-94; 8:45 am]

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