Federal Register / Vol. 62, No. 62 / Tuesday, April 1, 1997 / Rules and Regulations 15375

Room 1558, 601 E. 12th Street, Kansas City,

Missouri, or at the Office of the Federal

Register, 800 North Capitol Street, NW., suite

700, Washington, DC.

(f) This amendment (39–9984) becomes

effective on May 23, 1997.

Issued in Kansas City, Missouri, on March

26, 1997.

James E. Jackson,

Acting Manager, Small Airplane Directorate,

Aircraft Certification Service.

[FR Doc. 97–8249 Filed 3–31–97; 8:45 am]

BILLING CODE 4910–13–U

14 CFR Part 39

[Docket No. 95–CE–10–AD; Amendment 39–

9985; AD 97–07–11]

Airworthiness Directives; Jetstream

Aircraft Limited HP137 Mk1, Jetstream

Series 200, and Jetstream Models 3101

and 3201 Airplanes

AGENCY: Federal Aviation

Administration, DOT.

ACTION: Final rule.

SUMMARY: This amendment supersedes

Airworthiness Directive (AD) 81–20–01,

which currently requires repetitively

inspecting the nose landing gear (NLG)

actuator support structure and the front

pressure bulkhead for cracks on

Jetstream Aircraft Limited (JAL) HP137

Mk1 and Jetstream series 200 airplanes,

and replacing any cracked part. This AD

retains the repetitive inspections

required by AD 81–20–01; requires

repetitively inspecting the NLG

retraction jack upper mounting fitting

and attachment hardware for security

bolt failure and for bolts with improper

torque levels on the HP137 Mk1,

Jetstream series 200, and Jetstream

Model 3101 airplanes, and requires

replacing any failed security bolts and

adjusting any bolt with an improper

torque level; and requires modifying the

NLG retraction jack on all affected

airplanes, as terminating action for the

repetitive inspections. This AD results

from reports of NLG jack mounting

fitting failures on several of the affected

airplanes, and the Federal Aviation

Administration’s policy on aging

commuter-class aircraft. The actions

specified by this AD are intended to

prevent failure of the NLG caused by a

cracked NLG actuator support structure

or cracked front pressure bulkhead,

which, if not detected and corrected,

could lead to nose gear collapse and

damage to the airplane.

DATES: Effective May 23, 1997.

The incorporation by reference of

certain publications listed in the

regulations is approved by the Director

of the Federal Register as of May 23,

1997.

ADDRESSES: Service information that

applies to this AD may be obtained from

Jetstream Aircraft Limited, Prestwick

International Airport, Ayrshire, KA9

2RW, Scotland, telephone (44–292)

79888; facsimile (44–292) 79703; or

Jetstream Aircraft Inc., Librarian, P.O.

Box 16029, Dulles International Airport,

Washington, D.C. 20041–6029;

telephone (703) 406–1161; facsimile

(703) 406–1469. This information may

also be examined at the Federal

Aviation Administration (FAA), Central

Region, Office of the Assistant Chief

Counsel, Attention: Rules Docket No.

95-CE–10-AD, Room 1558, 601 E. 12th

Street, Kansas City, Missouri 64106; or

at the Office of the Federal Register, 800

North Capitol Street, NW., suite 700,

Washington, DC.

FOR FURTHER INFORMATION CONTACT: Mr.

Tom Rodriguez, Program Manager,

Brussels Aircraft Certification Division,

FAA, Europe, Africa, and Middle East

Office, c/o American Embassy, B–1000

Brussels, Belgium; telephone (32 2)

508.2715; facsimile (32 2) 230.6899; or

Mr. S.M. Nagarajan, Project Officer,

Small Airplane Directorate, Aircraft

Certification Service, FAA, 1201

Walnut, suite 900, Kansas City, Missouri

64106; telephone (816) 426–6932;

facsimile (816) 426–2169.

SUPPLEMENTARY INFORMATION:

Events Leading to the Issuance of This

AD

A proposal to amend part 39 of the

Federal Aviation Regulations (14 CFR

part 39) to include an AD that would

apply to certain JAL HP137 Mk1,

Jetstream series 200, and Jetstream

Models 3101 and 3201 airplanes that do

not have an improved design

attachment bracket (Modification JM

5285) installed for the nose landing gear

(NLG) retraction jack was published in

the Federal Register as a notice of

proposed rulemaking (NPRM) on

September 19, 1995 (60 FR 48429). The

NPRM proposed to supersede AD 81–

20–01 with a new AD that would:

—Retain the requirement contained in

AD 81–20–01 of repetitively

inspecting (using dye penetrant

methods) the NLG actuator support

structure and the front pressure

bulkhead for cracks on JAL HP137

Mk1 and Jetstream series 200

airplanes that do not have the front

pressure bulkhead strengthened in the

area of the NLG jack attachment

fitting (Modification No. 5127), and

replacing or repairing any cracked

NLG actuator support structure or

cracked front pressure bulkhead.

Accomplishment of the proposed

inspections as specified in the NPRM

would be in accordance with

Jetstream Service Bulletin (SB) No. 6/

5, dated September 4, 1978.

—Require repetitively inspecting the

NLG retraction jack upper mounting

fitting and attachment hardware for

security bolt failure and bolts with

improper torque levels on the HP137

Mk1, Jetstream series 200, and

Jetstream Model 3101 airplanes, and

replacing any failed security bolts and

adjusting any bolt with an improper

torque level. Accomplishment of the

proposed inspections as specified in

the NPRM would be in accordance

with Jetstream SB 53–A–JA870510,

which consists of the following pages

and revision levels:

Pages Revision

level Date

3, 5, 6, 8, 9,

and 10.

Original

Issue.

May 26, 1987.

1, 2, 4 and 7 .. Revision 1 Nov. 10, 1987.

—Require modifying the NLG retraction

jack on the HP137 Mk1, Jetstream

series 200, and Jetstream Models 3101

and 3201 airplanes, as terminating

action for all the repetitive

inspections, including the inspections

referenced in the Model 3201

maintenance manual.

Accomplishment of the proposed

modification as specified in the

NPRM would be in accordance with

Jetstream SB 53–JM 5285, which

consists of the following pages and

revision levels:

Pages Revision

level Date

1 and 4 .......... Revision 2 Nov. 12, 1992.

2, 3, and 5

through 26.

Revision 1 May 18, 1992.

Interested persons have been afforded

an opportunity to participate in the

making of this amendment. One

comment was received regarding the

NPRM. An analysis of the comment

follows:

The commenter provides information

on the company’s fleet size and the

estimated projection on when the

proposed replacement would be

mandatory on the affected airplanes in

the company’s fleet, as well as the

number of repetitive inspections that

would be required during that time. The

commenter states that it is more

economical for the company to

incorporate the modification on its

entire fleet immediately rather than

continuing to repetitively inspect. The

commenter also mentions that parts to
15376 Federal Register / Vol. 62, No. 62 / Tuesday, April 1, 1997 / Rules and Regulations

modify the NLG retraction jack cost

$1,800 instead of $1,600. The FAA

concurs with the correction to the cost

and has incorporated this change.

As written, the original NPRM would

have allowed continued flight if cracks

are found in the front pressure bulkhead

membrane or actuator support structure

when the cracks do not exceed certain

limits. Since issuing that NPRM, the

FAA established a policy to disallow

airplane operation when known cracks

exist in primary structure, unless the

ability to sustain ultimate load with

these cracks is proven. The front

pressure bulkhead and actuator support

structure are considered primary

structure, and the FAA has not received

any analysis to prove that ultimate load

can be sustained with cracks in this

area.

For this reason, the FAA has

determined that the crack limits

contained in the NPRM should be

eliminated and that AD action should be

taken to require immediate replacement

of any cracked front pressure bulkhead

membrane or actuator support structure.

Since revising the proposed AD to

require immediate replacement of any

cracked part went beyond the scope of

what was presented in the original

NPRM, the FAA published a

supplemental NPRM in the Federal

Register on October 21, 1996 (61 FR

54582), in order to give the public an

opportunity to comment on the

proposal.

Interested persons were again

afforded an opportunity to participate in

the making of this amendment. No

comments were received regarding the

substance of the supplemental NPRM or

the FAA’s determination of the cost to

the public.

The FAA’s Determination

After careful review of all available

information related to the subject

presented above, the FAA has

determined that air safety and the

public interest require the adoption of

the AD as proposed except for minor

editorial corrections. The FAA has

determined that these minor corrections

will not change the meaning of the AD

and will not add any additional burden

upon the public than was already

proposed.

The FAA’s Aging Commuter Aircraft

Policy

The actions required by this AD are

consistent with the FAA’s aging

commuter aircraft policy, which briefly

states that, when a modification exists

that could eliminate or reduce the

number of required critical inspections,

the modification should be

incorporated. This policy is based on

the FAA’s determination that reliance

on critical repetitive inspections on

airplanes utilized in commuter service

carries an unnecessary safety risk when

a design change exists that could

eliminate or, in certain instances,

reduce the number of those critical

inspections. In determining what

inspections are critical, the FAA

considers (1) the safety consequences of

the airplane if the known problem is not

detected by the inspection; (2) the

reliability of the inspection such as the

probability of not detecting the known

problem; (3) whether the inspection area

is difficult to access; and (4) the

possibility of damage to an adjacent

structure as a result of the problem.

Cost Impact

The FAA estimates that 170 airplanes

in the U.S. registry will be affected by

this AD, that it will take approximately

41 workhours per airplane to

accomplish the proposed modification,

and that the average labor rate is

approximately $60 an hour. Parts cost

approximately $1,800 per airplane.

Based on these figures, the total cost

impact of this AD on U.S. operators is

estimated to be $724,200 or $4,260 per

airplane. This figure only takes into

account the cost of the inspectionterminating modification and does not

take into account the cost of the

repetitive inspections. The FAA has no

way of determining the number of

repetitive inspections each HP137 Mk1,

Jetstream series 200, and Jetstream

Model 3101 airplane owner/operator

will incur over the life of the airplane.

This figure is also based on the

presumption that no affected airplane

owner/operator has accomplished the

required modification. This AD

eliminates the need for the repetitive

inspections required by AD 81–20–01.

The FAA has no way of determining the

operational levels of each individual

operator of the affected airplanes, and

subsequently cannot determine the

repetitive inspection costs that will be

eliminated by this AD. The FAA

estimates these costs to be substantial

over the long term.

In addition, JAL has informed the

FAA that parts have been distributed to

owners/operators to equip

approximately 39 of the affected

airplanes. Presuming that each set of

parts has been installed on an affected

airplane, the cost impact of the required

modification upon the public is reduced

$166,140 from $724,200 to $558,060.

The intent of the FAA’s aging

commuter airplane program is to ensure

safe operation of airplanes that are in

commercial service without adversely

impacting private operators. Of the

approximately 170 airplanes in the U.S.

registry that will be affected by this AD,

the FAA has determined that

approximately 95 percent are operated

in scheduled passenger service by 10

different operators.

Regulatory Impact

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 copy of the final

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, 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 USC 106(g), 40113, 44701.

§ 39.13 [Amended]

2. Section 39.13 is amended by

removing Airworthiness Directive (AD)

81–20–01, Amendment 39–4223, and by

adding a new AD to read as follows:

97–07–11 Jetstream Aircraft Limited:

Amendment 39–9985; Docket No. 95–

CE–10–AD. Supersedes AD 81–20–01,

Amendment 39–4223.

Applicability: The following airplanes,

certificated in any category, that do not have
Federal Register / Vol. 62, No. 62 / Tuesday, April 1, 1997 / Rules and Regulations 15377

an improved design attachment bracket for

the nose landing gear (NLG) retraction jack

(Modification JM 5285) installed in

accordance with the ACCOMPLISHMENT

INSTRUCTIONS section of Jetstream Service

Bulletin (SB) 53–JM 5285:

—HP137 Mk1 airplanes, all serial numbers;

—Jetstream Series 200 airplanes, all serial

numbers;

—Jetstream Model 3101 airplanes, all serial

numbers; and

—Jetstream Model 3201 airplanes, serial

numbers 601 through 840.

Note 1: This AD applies to each airplane

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

airplanes 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 (e) 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 in the

body of this AD, unless already

accomplished.

To prevent failure of the NLG caused by a

cracked NLG actuator support structure or

cracked front pressure bulkhead, which

could lead to nose gear collapse and damage

to the airplane, accomplish the following:

Note 2: The paragraph structure of this AD

is as follows:

Level 1: (a), (b), (c), etc.

Level 2: (1), (2), (3), etc.

Level 3: (i), (ii), (iii), etc.

Level 2 and Level 3 structures are

designations of the Level 1 paragraph they

immediately follow.

(a) For HP137 Mk1 and Jetstream series 200

airplanes that do not have the front pressure

bulkhead strengthened in the area of the NLG

jack attachment fitting (Modification 5127),

upon accumulating 1,600 landings or within

the next 200 landings after the effective date

of this AD, whichever occurs later, and

thereafter at intervals not to exceed 200

landings until the modification required by

paragraph (c) of this AD is incorporated,

inspect (using dye penetrant methods) the

nose landing gear actuator support structure,

part number (P/N) 137139C–13 and P/N

137139C–25 (or FAA-approved equivalents),

and the membrane of the front pressure

bulkhead for cracks. Accomplish the

inspection in accordance with British

Aerospace (BAe) SB No. 6/5, dated

September 4, 1978.

(1) Prior to further flight after any of the

inspections required by paragraph (a) of this

AD, replace any cracked P/N 137139C–13 (or

FAA-approved equivalent) NLG actuator

support structure. This replacement does not

eliminate the repetitive inspection

requirement of this AD.

(2) Prior to further flight after any of the

inspections required by paragraph (a) of this

AD, repair any cracked P/N 137139C–25 (or

FAA-approved equivalent) NLG actuator

support structure in accordance with the

applicable maintenance manual. This repair

does not eliminate the repetitive inspection

requirement of this AD.

(3) Prior to further flight after any of the

inspections required by paragraph (a) of this

AD, repair any cracked front pressure

bulkhead membrane in accordance with the

applicable maintenance manual. This repair

does not eliminate the repetitive inspection

requirement of this AD.

(b) For all HP137 Mk1, Jetstream series

200, and Jetstream Model 3101 airplanes,

upon accumulating 3,500 landings or within

the next 200 landings after the effective date

of this AD, whichever occurs later,

accomplish the following:

(1) Inspect the NLG retraction jack upper

mounting fitting and attaching hardware for

correct installation, security bolt failure, and

bolts with improper torque levels in

accordance with Part A and B of the

ACCOMPLISHMENT INSTRUCTIONS

section of Jetstream SB 53–A–JA870510,

which incorporates the following pages and

revision levels:

Pages Revision

level Date

3, 5, 6, 8, 9,

and 10.

Original

Issue.

May 26, 1987.

1, 2, 4 and 7 .. Revision 1 November 10,

1987.

Prior to further flight, replace any failed

security bolt and adjust any bolt with an

improper torque level in accordance with

Jetstream SB 53–A–JA870510.

(2) Reinspect the NLG retraction jack upper

mounting fitting and attaching hardware for

security bolt failure and bolts with improper

torque levels in accordance with Part A of the

ACCOMPLISHMENT INSTRUCTIONS

section of Jetstream SB 53–A–JA870510 at

intervals not to exceed 1,600 landings until

the modification required by paragraph (c) of

this AD is incorporated. Prior to further

flight, replace any failed security bolt and

adjust any bolt with an improper torque level

in accordance with Jetstream SB 53–A–

JA870510.

(3) Reinspect the NLG retraction jack upper

mounting fitting security nuts for correct

installation in accordance with Part B of the

ACCOMPLISHMENT INSTRUCTIONS

section of Jetstream SB 53–A–JA870510 at

intervals not to exceed 200 landings until the

modification required by paragraph (c) of this

AD is incorporated. If correct installation is

not evident, prior to further flight,

accomplish the reinspection specified in

paragraph (b)(2) of this AD.

(c) For all applicable HP137 Mk1, Jetstream

series 200, and Jetstream Models 3101 and

3201 airplanes, upon accumulating 25,000

landings or within the next 2,000 landings

after the effective date of this AD, whichever

occurs later, install an improved design

attachment bracket for the NLG retraction

jack (Modification JM 5285) in accordance

with the ACCOMPLISHMENT

INSTRUCTIONS section of Jetstream SB 53–

JM 5285, which incorporates the following

pages and revision levels:

Pages Revision

level Date

1 and 4 .......... Revision 2 November 12,

1992.

2, 3, and 5

through 26.

Revision 1 May 18, 1992.

(1) Incorporating Modification JM 5285 on

Jetstream HP137 Mk1, Jetstream series 200,

and Jetstream Model 3101 airplanes

terminates the repetitive inspection

requirement of this AD.

(2) Incorporating Modification JM 5285 on

Jetstream Model 3201 airplanes eliminates

the need for the repetitive inspections

specified in the applicable maintenance

manual.

(3) Modification JM 5285 may be

accomplished at any time prior to

accumulating 25,000 landings or within the

next 2,000 landings after the effective date of

this AD, whichever occurs later, at which

time it must be incorporated.

(d) 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 airplane to

a location where the requirements of this AD

can be accomplished.

(e) An alternative method of compliance or

adjustment of the initial or repetitive

compliance times that provides an equivalent

level of safety may be approved by the

Manager, Brussels Aircraft Certification

Division, Europe, Africa, Middle East office,

FAA, c/o American Embassy, 1000 Brussels,

Belgium. The request should be forwarded

through an appropriate FAA Maintenance

Inspector, who may add comments and then

send it to the Manager, Brussels Aircraft

Certification Division. Alternative methods of

compliance approved in accordance with AD

81–20–01 (superseded by this action) are not

considered approved as alternative methods

of compliance with this AD.

Note 3: Information concerning the

existence of approved alternative methods of

compliance with this AD, if any, may be

obtained from the Brussels Aircraft

Certification Division.

(f) The NLG actuator support structure

inspections required by this AD shall be done

in accordance with British Aerospace (BAe)

Service Bulletin No. 6/5, dated September 4,

1978. The inspection of the NLG retraction

jack upper mounting fitting and attaching

hardware required by this AD shall be done

in accordance with Jetstream Service Bulletin

53–A–JA870510, which incorporates the

following pages and revision levels:

Pages Revision

level Date

3, 5, 6, 8, 9,

and 10.

Original

Issue.

May 26, 1987.

1, 2, 4 and 7 .. Revision 1 Nov. 10, 1987.

The installation required by this AD shall be

accomplished in accordance with Jetstream

SB 53–JM 5285, which incorporates the

following pages and revision levels:
15378 Federal Register / Vol. 62, No. 62 / Tuesday, April 1, 1997 / Rules and Regulations

Pages Revision

level Date

1 and 4 .......... Revision 2 November 12,

1992.

2, 3, and 5

through 26.

Revision 1 May 18, 1992.

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 Jetstream Aircraft Limited, Manager

Product Support, Prestwick Airport,

Ayrshire, KA9 2RW Scotland; or Jetstream

Aircraft Inc., Librarian, P.O. Box 16029,

Dulles International Airport, Washington,

DC, 20041–6029. Copies may be inspected at

the FAA, Central Region, Office of the

Assistant Chief Counsel, Room 1558, 601 E.

12th Street, Kansas City, Missouri, or at the

Office of the Federal Register, 800 North

Capitol Street, NW., suite 700, Washington,

DC.

(g) This amendment (39–9985) becomes

effective on

May 23, 1997.

Issued in Kansas City, Missouri, on March

26, 1997.

Michael Gallagher,

Manager, Small Airplane Directorate, Aircraft

Certification Service.

[FR Doc. 97–8248 Filed 3–31–97; 8:45 am]

BILLING CODE 4910–13–U

14 CFR Part 39

[Docket No. 96–ANE–36; Amendment 39–

9955; AD 97–05–11]

RIN 2120–AA64

Airworthiness Directives; AlliedSignal

Inc. ALF502 and LF507 Series

Turbofan Engines

AGENCY: Federal Aviation

Administration, DOT.

ACTION: Final rule; request for

comments.

SUMMARY: This amendment supersedes

an existing airworthiness directive (AD),

applicable to AlliedSignal Inc. ALF502R

series turbofan engines, that currently

requires initial and repetitive

inspections of the oil system chip

detectors and oil filter bypass valve, and

optional installation of an improved oil

filter bypass valve, to ensure the

integrity of the reduction gear system

and overspeed protection system. The

optional installation of the improved oil

filter bypass valve provides terminating

action for the oil bypass valve spring

compression test requirements of the

current AD. This amendment requires

more stringent oil system inspection

requirements and expands the

applicable engine models to include

ALF502L and LF507 series turbofan

engines. This amendment is prompted

by power turbine (PT) shaft separations

on engines that had been inspected in

accordance with the current AD. The

actions specified by this AD are

intended to prevent No. 4 and 5 duplex

bearing failure, which can result in a

Stage 4 low pressure turbine (LPT) rotor

failure, an uncontained engine failure,

and damage to the aircraft.

DATES: Effective April 16, 1997.

The incorporation by reference of

certain publications listed in the

regulations is approved by the Director

of the Federal Register as of April 16,

1997. Comments for inclusion in the

Rules Docket must be received on or

before June 2, 1997.

ADDRESSES: Submit comments in

triplicate to the Federal Aviation

Administration (FAA), New England

Region, Office of the Assistant Chief

Counsel, Attention: Rules Docket No.

96-ANE–36, 12 New England Executive

Park, Burlington, MA 01803-5299.

Comments may also be sent via the

Internet using the following address: ‘‘9-

ad-engineprop@dot.faa.gov’’. Comments

sent via the Internet must contain the

docket number in the subject line.

The service information referenced in

this AD may be obtained from

AlliedSignal Aerospace, Attn: Data

Distribution, M/S 64–3/2101–201, P.O.

Box 29003, Phoenix, AZ 85038–9003;

telephone (602) 365–2493, fax (602)

365–5577. This information may be

examined at the FAA, New England

Region, Office of the Assistant Chief

Counsel, Burlington, MA; or at the

Office of the Federal Register, 800 North

Capitol Street, NW., suite 700,

Washington, DC.

FOR FURTHER INFORMATION CONTACT:

Raymond Vakili, Aerospace Engineer,

Los Angeles Aircraft Certification

Office, FAA, Transport Airplane

Directorate, 3960 Paramount Blvd.,

Lakewood, CA 90712–4137; telephone

(310) 627–5262; fax (310) 627–5210.

SUPPLEMENTARY INFORMATION: On July

17, 1987, the Federal Aviation

Administration (FAA) issued

airworthiness directive (AD) 87–06–52

R1, Amendment 39–5688 (52 FR 31979,

August 25, 1987), applicable to

AlliedSignal Inc. (formerly Avco

Lycoming Textron) ALF502R series

turbofan engines, to require initial and

repetitive inspections of the oil system

chip detectors and oil filter bypass

valve, and optional installation of an

improved oil filter bypass valve, to

ensure the integrity of the reduction

gear system and overspeed protection

system. The optional installation of the

improved oil filter bypass valve

provides terminating action for the

repetitive oil filter bypass valve spring

compression test requirements of the

AD 87–06–52 R1, Amendment 39–5688.

That action was prompted by reports of

power turbine (PT) overspeed and

uncontained PT blade failure resulting

from reduction gear system decouple

and inaccurate PT overspeed signal

generation. That condition, if not

corrected, could result in No. 4 and 5

duplex bearing failure, which can result

in a Stage 4 low pressure turbine (LPT)

rotor failure, an uncontained engine

failure, and damage to the aircraft.

Since the issuance of that AD, the

FAA has received reports of four

additional failures of the Stage 4 low

pressure turbine (LPT) rotor on

AlliedSignal Inc. ALF502 series

turbofan engines. The LPT failures were

caused by failure of the No. 4 and 5

duplex bearing, causing bearing seizure

and LPT shaft separation between the

two bearings forward of the Stage 4 LPT

rotor. In one incident the Stage 4 LPT

shaft separation caused an uncontained

rotor failure.

The FAA has reviewed and approved

the technical contents of the following

AlliedSignal Inc. Service Bulletins

(SBs): No. ALF502L 79–0171, Revision

1, dated November 27, 1996; No.

LF507–1F 79–5, Revision 1, dated

November 27, 1996; No. LF507–1H 79–

5, Revision 1, dated November 27, 1996;

and No. ALF502R 79–9, Revision 1,

dated November 27, 1996. These SBs

describe procedures for oil system

inspection. In addition, the FAA has

reviewed and approved the technical

contents of Textron Lycoming SB No.

ALF 502R–79–0162 R2, dated

September 8, 1987, to ensure that

portions of the accomplishment

instructions paragraph of this SB

continue to provide the terminating

action for the oil filter bypass valve

compression spring test, which is

required by AD 87–06–52 R1,

Amendment 39–5688. Also, the FAA