10228 Federal Register / Vol. 62, No. 44 / Thursday, March 6, 1997 / Proposed Rules

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.

§ 39.13 [Amended]

2. Section 39.13 is amended by

removing amendment 39–511 (32 FR

7248, May 16, 1967), and by adding a

new airworthiness directive (AD), to

read as follows:

Gulfstream Aerospace Corporation (formerly

Grumman): Docket 97–NM–19–AD.

Supersedes AD 67–17–05, Amendment

39–511.

Applicability: All Model G–159 (G–I)

airplanes, certificated in any category.

Note 1: This AD applies to each airplane

identified in the preceding applicability

provision, regardless of whether it has been

otherwise 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 (c) 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 excessive chafe wear of the

engine mount tube and upper diagonal truss,

which could lead to failure of the engine

mount assembly and possible separation of

the engine from the airplane, accomplish the

following:

(a) For airplanes on which chafe guards, P/

N 159WP10017–11, have not been installed

on each upper diagonal truss prior to the

effective date of this AD: Accomplish

paragraphs (a)(1), (a)(2), and (a)(3) of this AD:

(1) Restatement of Requirements of AD 67–

17–05: Within 100 hours time-in-service after

May 16, 1967 (the effective date of AD 67–

17–05, amendment 39–411), visually inspect

to detect chafe wear of the lower half of the

upper diagonal engine mount tubes having

part number (P/N) 159W10172–11 (left

engine) and P/N 159W10172–13 (right

engine).

(i) If no chafe wear is detected: Repeat this

inspection thereafter at intervals not to

exceed 200 hours time-in-service until the

requirements of paragraph (a)(2) are

accomplished.

(ii) If any tube is found to have wear depth

greater than 0.030 inch (as measured from the

outer edge of the tube): Prior to further flight,

replace the tube with a tube of the same part

number or with an FAA-approved equivalent

part. After replacement, repeat the inspection

required by this paragraph at intervals not to

exceed 200 hours time-in-service until the

requirements of paragraph (a)(2) are

accomplished.

(iii) If any tube is found to have wear depth

of 0.030 inch deep or less, as measured from

the outer edge of the tube: Prior to further

flight, either repair the tube in accordance

with an FAA-approved repair, or replace the

tube with a part of the same part number or

with an FAA-approved equivalent part. After

repair or replacement, repeat the inspection

required by this paragraph at intervals not to

exceed 200 hours time-in-service until the

requirements of paragraph (a)(2) are

accomplished.

(2) One-Time Inspection of Upper Diagonal

Truss and Installation of Chafe Guards.

Within 600 hours time-in-service after the

effective date of this AD, perform a one-time

visual inspection to detect chafe wear of the

left-hand and right-hand upper diagonal

truss, P/N’s 159W10172–5 (left-hand nacelle)

and P/N 159W10172–7 (right-hand nacelle),

in accordance with Grumman Gulfstream

Service Change No. 180, dated October 17,

1966. Once this inspection is completed, the

repetitive inspections required by paragraph

(a)(1) of this AD may be terminated.

(i) If there is no evidence of chafe wear on

the truss; or if there is evidence of chafe wear

and the depth of wear is .030 inch or less

(measured from the surface of the tube): Prior

to further flight, install a chafe guard, P/N

159WP10017–11, on the truss.

(ii) If there is any evidence of chafe wear

and the depth of wear exceeds .030 inch

measured (from the surface of the tube): Prior

to further flight, install a new upper diagonal

truss and install a chafe guard, P/N

159WP10017–11, on the truss.

(3) Continuing Inspections of Chafe

Guards. Within 2,500 hours time-in-service

after installation of the chafe guards required

by paragraph (a)(2) of this AD, perform an

inspection of the undersurface of each chafe

guard for evidence of chafe wear, in

accordance with Grumman Gulfstream

Service Change No. 180, dated October 17,

1966.

(i) If no chafe wear is detected: Repeat the

inspection at intervals not to exceed 2,500

hours time-in-service.

(ii) If any chafe wear is detected: Prior to

further flight, replace the chafe guard with a

new or serviceable part. After replacement,

repeat the inspection for chafe wear of the

chafe guard thereafter at intervals not to

exceed 2,500 hours time-in-service.

(b) For airplanes on which chafe guards, P/

N 159WP10017–11, have been installed on

each upper diagonal truss prior to the

effective date of this AD: Within 2,500 hours

time-in-service after the last inspection of the

chafe guard required by paragraph (c) of AD

67–17–05, repeat that inspection to detect

chafe wear of the chafe guards in accordance

with Grumman Gulfstream Service Change

No. 180, dated October 17, 1966.

(1) If no chafe wear is detected: Repeat the

inspection thereafter at intervals not to

exceed 2,500 hours time-in-service.

(2) If any chafe wear is detected: Prior to

further flight, replace the chafe guard with a

new or serviceable part. After replacement,

repeat the inspection thereafter at intervals

not to exceed 2,500 hour time-in-service.

(c) 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, Atlanta

Aircraft Certification Office (ACO), FAA,

Small Airplane Directorate. Operators shall

submit their requests through an appropriate

FAA Principal Maintenance Inspector, who

may add comments and then send it to the

Manager, Atlanta ACO.

Note 2: Information concerning the

existence of approved alternative methods of

compliance with this AD, if any, may be

obtained from the Atlanta ACO.

(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.

Issued in Renton, Washington, on February

27, 1997.

Darrell M. Pederson,

Acting Manager, Transport Airplane

Directorate, Aircraft Certification Service.

[FR Doc. 97–5462 Filed 3–5–97; 8:45 am]

BILLING CODE 4910–13–U

14 CFR Part 39

[Docket No. 97–NM–16–AD]

RIN 2120–AA64

Airworthiness Directives; Gulfstream

Aerospace Corporation Model G–159

(G–I) Airplanes

AGENCY: Federal Aviation

Administration, DOT.

ACTION: Notice of proposed rulemaking

(NPRM).

SUMMARY: This document proposes the

supersedure of an existing airworthiness

directive (AD), applicable to certain

Gulfstream Model G–159 (G–I)

airplanes, that currently requires

modification and repetitive inspections

for cracks in the main landing gear

(MLG) retract cylinder attachment

fittings. This action would require the

installation of improved attachment

fittings which, when accomplished,
Federal Register / Vol. 62, No. 44 / Thursday, March 6, 1997 / Proposed Rules 10229

would terminate the requirement for the

repetitive inspections. This proposal is

prompted by the development of a

modification that positively addresses

the identified unsafe condition. The

actions specified by the proposed AD

are intended to prevent failure of the

MLG retract cylinder attachment fitting

due to fatigue cracking. That condition,

if not corrected, could result in the

inability to retract the MLG.

DATES: Comments must be received by

April 14, 1997.

ADDRESSES: Submit comments in

triplicate to the Federal Aviation

Administration (FAA), Transport

Airplane Directorate, ANM–103,

Attention: Rules Docket No. 97–NM–

16–AD, 1601 Lind Avenue, SW.,

Renton, Washington 98055–4056.

Comments may be inspected at this

location between 9:00 a.m. and 3:00

p.m., Monday through Friday, except

Federal holidays.

The service information referenced in

the proposed rule may be obtained from

Gulfstream Aerospace Corporation,

Technical Operations Department, P.O.

Box 2206, M/S D–10, Savannah, Georgia

31402–2206. This information may be

examined at the FAA, Transport

Airplane Directorate, 1601 Lind

Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

Christina Marsh, Aerospace Engineer,

Airframe and Propulsion Branch, ACE–

117A, FAA, Small Airplane Directorate,

Atlanta Aircraft Certification Office,

Campus Building, 1701 Columbia

Avenue, Suite 2–160, College Park,

Georgia 30337–2748; telephone (404)

305–7362; fax (404) 305–7348.

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 shall

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 97–NM–16–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, Transport Airplane Directorate,

ANM–103, Attention: Rules Docket No.

97–NM–16–AD, 1601 Lind Avenue,

SW., Renton, Washington 98055–4056.

Discussion

In 1967, the FAA issued AD 67–31–

08, amendment 39–515 (32 FR 16201,

November 28, 1967), applicable to

certain Gulfstream Model G–159

airplanes, to require repetitive visual

and dye penetrant inspections for cracks

in the main landing gear (MLG) retract

cylinder attachment fittings, part

number (P/N) 159WM10032–1 and –2,

located on the lower surface of the lefthand and right-hand wings; and

replacement of cracked parts. It also

requires that the fittings be modified by

rounding off their aft end edges.

AD 67–31–08 also provided for an

optional terminating action, which

consisted of replacing the MLG retract

cylinder attachment fittings with

improved fittings, having Grumman P/N

159WM10276–1 and –2, and balls

having Grumman P/N 159WM10277–1.

That action was prompted by a report

indicating that, during a routine

inspection, the MLG retract cylinder

attachment fitting on one airplane was

found to be cracked through the aft end.

Examination of the fitting revealed

several notches located along one edge

in the area where the failure had

occurred. This cracking in the fitting

was determined to be due to fatigue that

could be directly attributed to these

notches.

The requirements of that AD are

intended to prevent failure of the MLG

retract cylinder attachment fitting due to

fatigue cracking. This condition, if not

corrected, could result in the inability to

retract the MLG.

Actions Since Issuance of Previous Rule

As part of its on-going program to

address issues relevant to the continued

operational safety of the aging transport

fleet, the FAA, along with Gulfstream

Aerospace Corporation and several U.S.

and non-U.S. operators of the affected

airplanes, agreed to undertake the task

of identifying and implementing

procedures to ensure the continuing

structural airworthiness of aging

commuter-class airplanes. This group

reviewed selected customer bulletins

and aircraft service changes, applicable

to Gulfstream Model G–159 airplanes, to

be recommended for mandatory

rulemaking action to ensure the

continued operational safety of these

airplanes.

Explanation of Relevant Service

Information

The group reviewed and

recommended Grumman Gulfstream

Service Change No. 184, dated February

1, 1968, and Amendment 1 to that

Service Change, dated June 28, 1968, for

mandatory rulemaking action. This

service information describes

procedures for removing MLG retract

cylinder attachment fitting assemblies

made of aluminum alloy and having P/

N 159WM10032–1 and –2, and

replacing them with fitting assemblies

made of steel and having P/N

159WM10276–1 and –2 and balls

having P/N 159WM10277–1.

Installation of steel assemblies will

preclude the potential for fatigue

cracking to occur in the fittings.

Explanation of Requirements of

Proposed Rule

Since an unsafe condition has been

identified that is likely to exist or

develop on other products of this same

type design, the proposed AD would

supersede AD 67–31–08. It would

continue to require the repetitive

inspections and modification of the

MLG retract cylinder attachment

fittings, and replacement, if necessary.

This new action would require that the

attachment fitting assemblies eventually

be replaced with assemblies made of

steel. Once this replacement is

accomplished, the previously required

modification and inspections may be

terminated. The replacement action

would be required to be accomplished

in accordance with the service

information described previously.

FAA’s Determination for the Need to

Mandate the Replacement

The FAA has determined that long

term continued operational safety will

be better assured by design changes to

remove the source of the problem, rather

than by repetitive inspections. Long

term inspections may not be providing

the degree of safety assurance necessary

for the transport airplane fleet. This,

coupled with a better understanding of

the human factors associated with

numerous continual inspections, has led
10230 Federal Register / Vol. 62, No. 44 / Thursday, March 6, 1997 / Proposed Rules

the FAA to consider placing less

emphasis on inspections and more

emphasis on design improvements. The

proposed replacement requirement is in

consonance with these considerations.

Cost Impact

There are approximately 146

Gulfstream Model G–159 (G–I) airplanes

of the affected design in the worldwide

fleet. The FAA estimates that 72

airplanes of U.S. registry would be

affected by this proposed AD.

The actions that are currently

required by AD 67–31–08 take

approximately 3 work hours per

airplane to accomplish, at an average

labor rate of $60 per work hour. Based

on these figures, the cost impact of the

currently required actions on U.S.

operators is estimated to be $12,960, or

$180 per airplane, per inspection.

The replacement action that is

proposed in this AD action would take

approximately 45 work hours per

airplane to accomplish, at an average

labor rate of $60 per work hour.

Required parts would cost

approximately $5,400 per airplane.

Based on these figures, the cost impact

of the proposed requirements of this AD

on U.S. operators is estimated to be

$583,200, or $8,100 per airplane.

The cost impact figures discussed

above are based on assumptions that no

operator has yet accomplished any of

the current or proposed requirements of

this AD action, and that no operator

would accomplish those actions in the

future if this AD were not adopted.

Regulatory Impact

The regulations proposed herein

would 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

proposal would not have sufficient

federalism implications to warrant the

preparation of a Federalism Assessment.

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.

§ 39.13 [Amended]

2. Section 39.13 is amended by

removing amendment 39–515 (32 FR

16201, November 28, 1967), and by

adding a new airworthiness directive

(AD), to read as follows:

Gulfstream Aerospace Corporation (formerly

Grumman): Docket 97-NM–16-AD.

Supersedes AD 67–31–08, amendment

39–515.

Applicability: Model G–159 (G-I) airplanes;

serial numbers (S/N) 1 through 12 inclusive,

14 through 112 inclusive, 114 through 148

inclusive, 322, and 323; on which main

landing gear cylinder attach fitting

assemblies having part number (P/N)

159WM10276–1 and -2 and balls having P/

N 159WM10277–1 are not installed;

certificated in any category.

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 (d)(1) 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 main landing gear

(MLG) retract cylinder attachment fittings

due to fatigue cracking, which could result in

the inability to retract the MLG, accomplish

the following:

(a) Accomplish the actions specified in

paragraphs (a)(1) and (a)(2) of this AD, at the

times indicated in those paragraphs and in

accordance with Grumman Gulfstream

Customer Bulletin No. 172, dated September

6, 1963.

(1) Beginning November 7, 1967 (the

effective date of AD 67–31–08, amendment

39–515), and prior to each flight, conduct a

visual inspection to detect cracks in the MLG

retract cylinder attachment fittings on the

lower surface of the right-hand and left-hand

wings in the vicinity of the aft end of the

fitting.

(2) Within 25 hours time-in-service after

November 7, 1967, accomplish the actions

specified in paragraphs (a)(2)(i) and (a)(2)(ii)

of this AD:

(i) Conduct a dye penetrant inspection, in

conjunction with at least a 10X magnifying

glass, to detect cracks in the MLG retract

cylinder attachment fittings on the lower

surface of the right-hand and left-hand wings

in the vicinity of the aft end of the fitting.

Repeat this inspection thereafter at intervals

not to exceed 25 hours time-in-service. And

(ii) Modify the aft end edges of the fitting

by rounding them off to approximately 1/32’’

radius.

(b) If any crack is found during an

inspection required by paragraph (a) of this

AD, prior to further flight, accomplish either

paragraph (b)(1) or (b)(2) of this AD:

(1) Replace the cracked part with a part of

the same part number that has been modified

and inspected in accordance with paragraph

(a) of this AD, in accordance with Grumman

Gulfstream Customer Bulletin No. 172, dated

September 6, 1963. Thereafter, continue the

inspections required by paragraph (a) of this

AD. Or

(2) Replace the fitting assembly with an

assembly having part number (P/N)

159WM10276–1 or -2, and balls having P/N

159WM10277–1. After accomplishing this

replacement, the repetitive inspections of

that fitting required by paragraph (a) of this

AD may be terminated.

(c) Within 400 hours time-in-service after

the effective date of this AD, replace the MLG

retract cylinder attachment fitting assemblies

with assemblies having part numbers (P/N)

159WM10276–1 and -2, and balls having P/

N 159WM10277–1. This replacement

constitutes terminating action for the

inspection requirements of this AD.

(d)(1) 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, Atlanta

Aircraft Certification Office (ACO), FAA,

Small Airplane Directorate. Operators shall

submit their requests through an appropriate

FAA Principal Maintenance Inspector, who

may add comments and then send it to the

Manager, Atlanta ACO.

(2) Alternative methods of compliance,

approved previously in accordance with AD

67–31–08, amendment 39–515, are approved

as alternative methods of compliance with

this AD.

Note 2: Information concerning the

existence of approved alternative methods of

compliance with this AD, if any, may be

obtained from the Atlanta ACO.

(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 airplane to

a location where the requirements of this AD

can be accomplished.
Federal Register / Vol. 62, No. 44 / Thursday, March 6, 1997 / Proposed Rules 10231

Issued in Renton, Washington, on February

27, 1997.

Darrell M. Pederson,

Acting Manager, Transport Airplane

Directorate, Aircraft Certification Service.

[FR Doc. 97–5461 Filed 3–5–97; 8:45 am]

BILLING CODE 4910–13–U

14 CFR Part 39

[Docket No. 97–NM–15–AD]

RIN 2120–AA64

Airworthiness Directives; Gulfstream

Aerospace Corporation Model G–159

(G–I) Airplanes

AGENCY: Federal Aviation

Administration, DOT.

ACTION: Notice of proposed rulemaking

(NPRM).

SUMMARY: This document proposes the

supersedure of an existing airworthiness

directive (AD), applicable to certain

Gulfstream Model G–159 (G–I)

airplanes, that currently requires

repetitive inspections to detect cracking

in the mounting lugs of the elevator trim

tab actuators, and replacement, if

necessary. This action would require the

installation of improved elevator trim

tab actuators that are not susceptible to

the subject cracking. This proposal is

prompted by the development of a

modification that positively addresses

the identified unsafe condition. The

actions specified by the proposed AD

are intended to prevent failure of the

mounting lugs on the elevator trim tab

actuator due to cracking; such failure

could result in severe vibration during

flight and/or reduction or loss of

elevator trim tab capability, which

could lead to reduced controllability of

the airplane.

DATES: Comments must be received by

April 14, 1997.

ADDRESSES: Submit comments in

triplicate to the Federal Aviation

Administration (FAA), Transport

Airplane Directorate, ANM–103,

Attention: Rules Docket No. 97–NM–

15–AD, 1601 Lind Avenue, SW.,

Renton, Washington 98055–4056.

Comments may be inspected at this

location between 9:00 a.m. and 3:00

p.m., Monday through Friday, except

Federal holidays. The service information referenced in

the proposed rule may be obtained from

Gulfstream Aerospace Corporation,

Technical Operations Department, P.O.

Box 2206, M/S D–10, Savannah, Georgia

31402–2206. This information may be

examined at the FAA, Transport

Airplane Directorate, 1601 Lind

Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

Christina Marsh, Aerospace Engineer,

Airframe and Propulsion Branch, ACE–

117A, FAA, Small Airplane Directorate,

Atlanta Aircraft Certification Office,

Campus Building, 1701 Columbia

Avenue, Suite 2–160, College Park,

Georgia 30337–2748; telephone (404)

305–7362; fax (404) 305–7348.

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 shall

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 97–NM–15–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, Transport Airplane Directorate,

ANM–103, Attention: Rules Docket No.

97–NM–15–AD, 1601 Lind Avenue,

SW., Renton, Washington 98055–4056.

Discussion

In 1972, the FAA issued AD 72–24–

04, amendment 39–1559 (37 FR 24419,

November 17, 1972), applicable to

certain Gulfstream Model G–159’’

airplanes (formerly designated as

‘‘Grumman Gulfstream G–159’’

airplanes), to require: 1. repetitive dye penetrant inspections

to detect cracking in the mounting lugs

of the elevator trim tab actuator, part

number (P/N) 159SCC100–1 and –5; and

2. shimming to correct any out-ofplane mounting. If cracking is detected during any

inspection, the AD requires that the

actuator be replaced with an actuator

having P/N 159SCC100–1, –5, or –11.

(AD 72–24–04 specifies that, if an

actuator having P/N 159SCC100–11 is

installed, no further action is required.)

That action was prompted by a report

indicating that, during an inspection, all

four mounting lugs on a Gulfstream G–

159 elevator trim tab actuator were

found to be cracked. Examination of the

actuator unit indicated that two of the

lugs had been failed for an

undetermined period of time.

Additional inspections of other

airplanes revealed numerous fittings

with one lug failed and some with two

lugs failed.

Once one lug fails, the adjacent lug is

under twice the normal stress, and will

eventually fail. At that point, the

remaining two lugs are being worked in

bending and their remaining service life,

in this condition, is short.

The requirements of that AD are

intended to detect cracked lugs as early

as possible so as to prevent the

concurrent failure of the four lugs. Such

failure could cause severe vibration

during flight and/or reduction or loss of

elevator trim tab capability; this could

then result in reduced controllability of

the airplane.

Actions Since Issuance of Previous Rule

As part of its on-going program to

address issues relevant to the continued

operational safety of the aging transport

fleet, the FAA, along with Gulfstream

Aerospace Corporation and several U.S.

and non-U.S. operators of the affected

airplanes, agreed to undertake the task

of identifying and implementing

procedures to ensure the continuing

structural airworthiness of aging

commuter-class airplanes. This group

reviewed selected customer bulletins

and aircraft service changes, applicable

to Gulfstream Model G–159 airplanes, to

be recommended for mandatory

rulemaking action to ensure the

continued operational safety of these

airplanes.

Explanation of Relevant Service

Information

The group reviewed and

recommended Grumman Gulfstream I

Aircraft Service Change No. 191, dated

August 18, 1972, for mandatory

rulemaking action. This service change

describes procedures for replacing the

elevator trim tab actuators having P/N

159SCC100–1 or –5, with actuators

having P/N 159SCC100–11. The

replacement actuators have new,

increased strength housings, and are not

susceptible to the type of cracking that