Federal Register / Vol. 63, No. 96 /Tuesday, May 19, 1998 /Rules and Regulations 27465

Page No. shown on

page

Revision level

shown on page

List of Active Pages—

Pages 1 thru 17.2 ..... H

(Note: The issue date of Revision H is indicated only on the title page; no other page of

the document is dated.) 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 Boeing Commercial Airplane

Group, P.O. Box 3707, Seattle, Washington

98124–2207. Copies may be inspected at the

FAA, Transport Airplane Directorate, 1601

Lind Avenue, SW., Renton, Washington; or at

the Office of the FEDERAL REGISTER, 800 North

Capitol Street, NW., suite 700, Washington,

DC.

(l) This amendment becomes effective on

June 23, 1998.

Issued in Renton, Washington, on May 12,

1998.

D. L. Riggin,

Acting Manager, Transport Airplane

Directorate, Aircraft Certification Service.

[FR Doc. 98–13077 Filed 5–18–98; 8:45 am]

BILLING CODE 4910–13–U

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96–NM–264–AD; Amendment

39–10531; AD 98–11–04]

RIN 2120–AA64

Airworthiness Directives; Boeing

Model 737–100 and –200 Series

Airplanes

AGENCY: Federal Aviation

Administration, DOT.

ACTION: Final rule.

SUMMARY: This amendment supersedes

an existing airworthiness directive (AD),

applicable to all Boeing Model 737–100

and –200 series airplanes, that currently

requires that the FAA-approved

maintenance inspection program be

revised to include inspections that will

give no less than the required damage

tolerance rating for each Structural

Significant Item, and repair of cracked

structure. That AD was prompted by a

structural re-evaluation by the

manufacturer which identified

additional structural elements where, if

damage were to occur, supplemental

inspections may be required for timely

detection. This amendment requires

additional and expanded inspections,

and repair of cracked structure. This

amendment also expands the

applicability of the existing AD to

include additional airplanes. The

actions specified by this AD are

intended to ensure the continued

structural integrity of the entire Boeing

Model 737–100 and –200 fleet.

DATES: Effective June 23, 1998.

The incorporation by reference of

certain publications is approved by the

Director of the Federal Register as June

23, 1998.

ADDRESSES: The service information

referenced in this AD may be obtained

from Boeing Commercial Airplane

Group, P.O. Box 3707, Seattle,

Washington 98124–2207. This

information may be examined at the

Federal Aviation Administration (FAA),

Transport Airplane Directorate, Rules

Docket, 1601 Lind Avenue, SW.,

Renton, Washington; or at the Office of

the Federal Register, 800 North Capitol

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

FOR FURTHER INFORMATION CONTACT: Greg

Schneider, Aerospace Engineer,

Airframe Branch, ANM–120S, FAA,

Seattle Aircraft Certification Office,

1601 Lind Avenue, SW., Washington;

telephone (425) 227–2028; fax (425)

227–1181.

SUPPLEMENTARY INFORMATION: A

proposal to amend part 39 of the Federal

Aviation Regulations (14 CFR part 39)

by superseding airworthiness directive

(AD) 91–14–20, amendment 39–7061

(56 FR 30680, July 5, 1991), which is

applicable to all Boeing Model 737–100

and –200 series airplanes, was

published in the Federal Register on

August 7, 1997 (62 FR 42433). That

action proposed to supersede AD 91–

14–20 to continue to require that the

FAA-approved maintenance program be

revised to include inspections that will

give no less than the required damage

tolerance rating for each Structural

Significant Item (SSI). That action also

proposed to require additional and

expanded inspections, and repair of

cracked structure. In addition, that

action proposed to expand the

applicability of the existing AD to

include additional airplanes. [A similar

proposal applicable to all Boeing Model

727 series airplanes also was published

in the Federal Register on May 29, 1997

(62 FR 29081).]

Comments

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 has received comments in

response to the two NPRM’s discussed

previously (i.e., Docket Nos. 96–NM–

263–AD and 96–NM–264–AD). Because

in most cases the issues raised by the

commenters are generally relevant to

both NPRM’s, each final rule includes a

discussion of all comments received.

Two commenters support the

proposed rule.

Delete Repairs and Type Certificate

Holder Modifications

Several commenters request that, for

the reasons stated below, the FAA

delete the requirements that address

repairs and Boeing modifications (i.e.,

modifications specified in service

bulletins or other technical data issued

by Boeing), as specified in paragraphs

(d) and (f) of the proposed AD.

Several commenters contend that the

intent of the Boeing Supplemental

Structural Inspection Program (SSIP)

was to evaluate the original structure of

candidate fleet airplanes using the latest

damage tolerance methods, not to bring

all airplanes up to damage tolerance

design. They note that the Boeing

Supplemental Structural Inspection

Document (SSID) explicitly excluded

SSI’s that had been modified or

repaired, because they were no longer

considered to be representative of the

configuration of the fleet. One of these

commenters also states that Boeing

should retain the authority to determine

whether repaired SSI’s are

representative.

The FAA infers that the commenters

believe that the purpose of the SSIP for

Boeing airplanes is limited to protecting

the original airplane structure. As

discussed in the notice of proposed

rulemaking (NPRM), FAA Advisory

Circular (AC) No. 91–56, Change 2,

dated April 15, 1983, states that

assessments should be accomplished on

modified or repaired structure to

determine whether special inspections

are needed to ensure continued

airworthiness, regardless of whether the

structure continues to be

‘‘representative’’ of the original

structure. Consistent with this policy,

the FAA has previously issued other

SSIP AD’s that effectively require

assessment of repairs and modifications:

• For McDonnell Douglas Model DC–

8 series airplanes: AD 93–01–15,

amendment 39–8464 (58 FR 5576,

January 22, 1993);

• For McDonnell Douglas Model DC–

9 series airplanes: AD 96–13–03,

amendment 39–9671 (61 FR 31009, June

19, 1996); and

• For McDonnell Douglas Model DC–

10 series airplanes: AD 95–23–09,

amendment 39–9429 (60 FR 61649,

December 1, 1995).

One of the purposes of this AD is to

correct this deficiency in the Boeing

SSIP. The commenters have not

provided any information to call this

basic policy into question. The FAA

finds that repaired or modified SSI’s

should be included in the Boeing SSIP
27466 Federal Register / Vol. 63, No. 96 /Tuesday, May 19, 1998 /Rules and Regulations

to ensure timely detection of cracking in

those areas. Boeing does retain the

authority to determine whether repaired

or modified SSI’s are ‘‘representative,’’

but that determination will no longer

have the effect of deleting repaired or

modified SSI’s from the Boeing SSIP.

Several commenters also state that, in

consideration of their request to delete

repaired SSI’s or Boeing modifications

from the SSIP, reducing the inspection

thresholds specified in the proposed AD

would offset the FAA’s concern

regarding the reduction in the number

of inspected SSI’s. One of these

commenters suggests that the FAA

reduce the inspection thresholds

specified in the proposed AD by an

incremental amount to increase the

inspected fleet by 10 percent. Such a

reduction would compensate for the

subject deletions. Another commenter

states that lowering the threshold would

require less time and lower labor costs

than that required to develop special

inspections for repairs and

modifications. The FAA does not

concur. As discussed previously, the

purpose of the SSIP is to ensure the

continued airworthiness of all airplanes,

including those that have been repaired

or modified. The commenters’ proposal

would not achieve this objective.

In contrast to the previous comments,

several commenters state that SSI’s

affected by standard repairs or Boeing

modifications do not need to be

included in the Boeing SSIP, because

the original structure is ‘‘representative’’

of the durability of repaired or modified

structure. The FAA does not concur.

Although repaired or modified structure

may be similar to original structure,

operators must accomplish an

assessment to determine if the

inspection program specified in the

SSID is effective. It should be noted

that, if the assessment indicates that the

applicable inspection specified in the

SSID is effective, no change to the

Boeing SSIP is required.

Several commenters state that

paragraphs (d) and (f) of the proposed

AD are unnecessary because other

airworthiness programs and documents,

such as the proposed repair assessment

program (RAP) for pressurized

fuselages, will require operators to

assess repairs and modifications. [The

FAA has issued Notice No. 97–16,

Docket No. 29104 (63 FR 126, January

2, 1998) that would require operators of

certain transport category airplanes,

including the Model 737, to adopt

RAP’s into their maintenance or

inspection programs.] Two of these

commenters state that the 737

Structures Task Group (STG) (a group

consisting of 737 operators and Boeing)

has taken the position that only repairs

to the fuselage skins and pressure webs

need to be assessed for damage

tolerance, not repairs to other areas of

the airplane structure (e.g., wing and

empennage SSI’s).

For two reasons, the FAA does not

concur that the proposed RAP is

adequate to address potential fatigue

cracking of modified or repaired SSI’s.

First, the proposed RAP does not

address either the damage tolerance

characteristics of SSI’s in supplemental

type certificate (STC) modified structure

that has not been repaired, or the effects

of such modifications on original SSI’s.

Second, the FAA does not concur

with the commenters that only the

pressure boundary should be subject to

a damage tolerance assessment. The

STG’s conclusion that only repairs to

the pressure boundary need to be

assessed is based on a small sampling of

existing repairs and on an assumption

that those repairs are representative of

all repairs. This approach would not

give any consideration to repairs that

are internal to the fuselage skin, or

repairs to the wings or empennage. The

FAA is aware that a significant number

of these types of repairs have been

installed on Model 737 airplanes, and

that these repairs have not been

assessed, to the extent practicable, in

accordance with the principles of the

current damage tolerance standards (14

CFR 25.571, Amdt. 25–45). For those

repairs that affect SSI’s, the failure of

which could be catastrophic, reliance on

an assumption that these repairs are free

of fatigue cracking is inappropriate.

Therefore, reliance on the proposed

RAP is inconsistent with the policy of

AC No. 91–56, which does not draw a

distinction between original structure

and modified or repaired structure in

describing the need for damage

tolerance assessments of SSI’s to ensure

the structural integrity of the airplane.

As discussed in the NPRM, the FAA

continues to consider that appropriate

damage tolerance based inspections are

a necessary means to ensure long-term

structural integrity of all SSI’s,

including those that have been modified

or repaired. It should be noted that this

AD and the proposed RAP are

complementary for the structure

associated with fuselage skins and

pressure webs. Compliance with the

SSID may be facilitated by use of the

repair assessment guidelines developed

in conjunction with the proposed RAP;

and, assuming that the FAA adopts the

proposed RAP, compliance with this AD

will facilitate compliance with the

requirements of the proposed RAP.

One commenter states that the

existing Corrosion Prevention and

Control Program (CPCP), in concert with

the proposed RAP, makes the

inspections specified in the proposed

AD unnecessary and redundant. In

addition, this commenter states that the

CPCP requires 100 percent (visual)

inspections of all SSI’s, including

repaired or modified SSI’s.

The FAA does not concur. The

relationship of this AD to the proposed

RAP is discussed previously. The CPCP

AD’s require visual inspections to detect

corrosion of SSI’s. In contrast, the SSIP

AD’s require various inspection

methods (e.g., visual, eddy current,

ultrasonic) to detect fatigue cracks in

SSI’s. Because the purposes of the two

programs are different, in many cases,

the corrosion inspections would not be

adequate to detect fatigue cracking. In

conclusion, the FAA has determined

that the Boeing SSIP is necessary to

maintain the airworthiness of the

Boeing Model 737 fleet, and that it is

not redundant with the proposed RAP

and CPCP.

Extend Compliance Time for Assessing

Existing Repairs and Boeing

Modifications

Several commenters request that the

FAA revise paragraph (d) of the

proposed AD to extend the compliance

time of 18 months for existing repairs

and Boeing modifications. The

commenters state that repairs and

Boeing modifications are likely to have

fatigue characteristics that are similar to

the original structure and, therefore, are

not of immediate concern. These

commenters also state that compliance

within 18 months would cause an

undue burden on operators because of

the size of the fleet, the number of

repairs and modifications on each

airplane that would need to be

identified and evaluated, the difficulty

of accessing the affected structure, and

the total number of work hours

necessary to comply with the

requirement. The commenters state that,

because the purpose of the inspections

is to identify potential unsafe

conditions, rather than address known

unsafe conditions, the level of effort

necessary to comply within 18 months

is unjustified. One commenter states

that there is a shortage of sufficiently

trained personnel to develop necessary

non-destructive test (NDT) procedures

to conduct the required inspections

within the proposed compliance time.

Another commenter proposes that

operators be able to address repairs

during the required SSID inspections.

The FAA concurs that an extension of

the compliance time is appropriate. The

FAA agrees that Boeing repairs and

modifications are likely to have fatigue
Federal Register / Vol. 63, No. 96 /Tuesday, May 19, 1998 /Rules and Regulations 27467

characteristics that are similar to the

original structure and, therefore, are not

of immediate concern. For other repairs,

although their fatigue characteristics

may be different, the FAA recognizes

that the records and data necessary to

identify and evaluate these repairs may

not be readily available.

Therefore, the FAA has revised the

final rule to include a new paragraph (e)

to specifically address repairs and

design changes other than STC’s.

Operators are required to identify each

repair or design change to an SSI at the

time of the first inspection of each SSI

after the effective date of the AD in

accordance with Revision D of the SSID.

Within 12 months after such

identification, operators are required to

assess the damage tolerance

characteristics of each SSI created or

affected by each repair or design change

to determine the effectiveness of the

applicable SSID inspection for each SSI

and, if not effective, revise the FAAapproved maintenance or inspection

program to include an inspection

method and compliance times for each

new or affected SSI. This change will

enable operators to identify these

repairs and modifications at the time of

the required SSID inspection, so that no

additional inspections will be

necessary. This change also will allow

for the timely development of NDT

procedures. The requirement to revise

the maintenance or inspection program

within 12 months after identification of

each repair or design change is

consistent with both the guidance of AC

No. 25–1529–1, dated August 1, 1991,

and the long-standing practice under the

McDonnell Douglas SSIP’s.

Evaluation of Existing STC Design

Changes

Several commenters state that

paragraph (d) of the proposed AD

should retain the requirement to revise

the maintenance or inspection program

to address STC design changes within

18 months after the effective date of this

AD. The commenters state that the

durability of individual airplanes is

affected by STC design changes, which

affect existing SSI’s and create new

SSI’s. Thus, the inspection times for

these SSI’s might need to be revised to

account for changes in durability. The

commenters also state that the STC

documentation should be readily

available. This would permit a timely

paperwork evaluation of the effect on

the Boeing SSIP without an extensive

airplane inspection. In contrast, another

commenter requests an extension of the

18-month compliance time to 5 years for

implementing program revisions for

addressing STC’s. This commenter notes

that STC holders are not equipped to

perform the assessments of affected

SSI’s.

The FAA concurs partially. Although

most of these commenters support the

proposed requirements of paragraph (d)

for STC design changes, the FAA has

revised paragraph (d) of the final rule to

limit its applicability to airplanes on

which STC’s have been incorporated,

and to provide an option that would

extend the compliance time for

identifying and evaluating SSI’s created

or affected by STC’s and revising the

maintenance or inspection programs to

reflect those evaluations. The FAA has

recently reviewed several STC’s

regarding the installation of cargo doors

on 727 airplanes and determined that

the substantiating data for many of these

STC’s do not include internal loads

data. Without the internal loads data for

the modified structure, it would be

difficult to perform an adequate damage

tolerance assessment.

In accordance with the guidance

provided in AC No. 91–56, external

(flight, pressure, and ground) loads are

necessary to complete a structural

damage tolerance assessment and must

be obtained from the type certificate

(TC) holder or be developed by another

source. Those external loads must then

be applied to the structure and resolved

into an internal distribution within the

STC structural components (this

includes original structure that is not

modified but could be affected by the

STC design change). All STC structural

parts, whose failure could reduce the

structural integrity of the airplane, then

must be identified (as SSI’s), and a

damage tolerance assessment must be

performed. Subsequently, the inspection

methods compliance times (i.e.,

thresholds and repetitive intervals) must

be developed for these SSI’s and added

to the operator’s maintenance or

inspection program. Therefore, the FAA

has determined that operators may need

more time to assess STC design changes

on their airplanes.

To avail themselves of the option of

extending the 18-month compliance

time, operators are required to

accomplish the following three actions:

1. Within 18 months after the effective

date of this AD, submit a plan to ensure

that they are developing data, as

described above, that supports their

revision to the FAA-approved

maintenance or inspection program (i.e.,

compliance times and inspection

methods for new or affected SSI’s), and

to demonstrate that they are able to

complete the required tasks within 48

months after the effective date of this

AD.

2. Within 18 months after the effective

date of this AD, and thereafter at

intervals not to exceed 18 months,

accomplish a detailed visual inspection

of all structure identified in Revision D

of the SSID that has been modified in

accordance with an STC (this repetitive

inspection will be terminated by

accomplishment of the third action).

The detailed visual inspection and the

repair of any crack shall be

accomplished in accordance with a

method approved by the Manager of the

Seattle Aircraft Certification Office

(ACO).

3. Within 48 months after the effective

date of this AD, revise the maintenance

or inspection program to include an

inspection method for each new or

affected SSI and to include the

compliance times for initial and

repetitive accomplishment of these

inspections.

The plan that an operator submits to

the FAA for approval should include a

detailed description of the: (1) STC; (2)

methodology for identifying new or

affected SSI’s; (3) method for developing

loads and validating the analysis; (4)

methodology for evaluating and

analyzing the damage tolerance

characteristics of each new or affected

SSI (see discussion below); and (5)

proposed inspection methods. The plan

would not need to include all of these

elements if the operator can otherwise

demonstrate that its plan will result in

implementation of an acceptable

program within 48 months after the

effective date of this AD. For this

option, the final rule requires that the

plan be submitted to the Manager of the

Seattle ACO within 18 months after the

effective date of the AD.

As indicated by the commenters, STC

modifications may pose a greater risk of

fatigue cracking than standard repairs or

Boeing modifications. However, STC

holders normally do not have access to

Boeing type certification data.

Therefore, STC modified structure may

not have the same durability as the

original structure or structure that has

been subject to standard repairs or

Boeing modifications. In order to ensure

the structural integrity of STC modified

structure during the 48-month

compliance time provided for the

development of a revision of the

maintenance or inspection program to

address STC’s, the FAA considers it

necessary to require repetitive detailed

visual inspections of that structure.

These visual inspection methods are

required to be approved by the Manager

of the Seattle ACO to ensure that

adequate access is provided and that the

inspection area is adequately defined. In

addition, the repair of any crack must be
27468 Federal Register / Vol. 63, No. 96 /Tuesday, May 19, 1998 /Rules and Regulations

approved by the Manager of the Seattle

ACO. This contrasts with the repair

provision of paragraph (f) of the final

rule, which requires that cracks be

repaired in accordance with any FAAapproved method. Seattle ACO approval

for these repairs is necessary because, as

discussed previously, the durability of

these STC’s is unknown, and findings of

cracks may indicate the need for

additional corrective action. The FAA

has revised paragraph (f) of the final

rule to reference the ACO approval as an

exception to the general provisions

allowing repairs in accordance with an

FAA-approved method. The FAA

selected an 18-month inspection

interval to coincide with most operators’

normal maintenance schedules. It

should be noted that these visual

inspections would not be required for

operators who adopt a damage tolerance

based revision to the maintenance or

inspection program to address STC

modifications within 18 months after

the effective date of this AD, as

proposed in the NPRM.

One commenter also requests that the

FAA develop guidelines to assist

operators in assessing STC’s. The FAA

does not consider that there is a need for

further guidance at this time. As

discussed previously, AC No. 91–56

provides extensive guidance on

methods for assessing the airplane

structure using damage tolerance

principles to the extent practicable. This

guidance is also applicable to STC’s.

Revise Compliance Time to Assess

Future Repairs and Modifications

Several commenters concur with the

requirements of paragraph (f) of the

proposed AD.

Several other commenters request that

paragraph (f) be revised to extend the

compliance time for assessment of

repairs and modifications installed after

the effective date of this AD. Rather than

completing a damage tolerance

assessment within 12 months after

installation of the repair or

modification, as proposed in the NPRM,

these commenters suggest that operators

should be required to complete an

assessment within 12 months after

accomplishment of the next SSID

inspection of the SSI following such an

installation.

The FAA does not concur. The FAA

has determined that delaying the

assessment until after the next SSID

inspection is not appropriate. At the

time of the installation, operators have

all the data necessary to define the

repair or modification that would be

used in an assessment. Delaying the

assessment until after the subsequent

SSID inspection may result in loss of

these data. Requiring an assessment

within 12 months after installation of

the repair or modification provides

sufficient time and ensures that the

inspection program accurately reflects

the actual airplane structure. As stated

previously, the requirement to revise the

maintenance or inspection program

within 12 months after installation is

consistent with both the guidance of AC

No. 25–1529 and the long-standing

practice under the McDonnell Douglas

SSIP’s.

Clarify What ‘‘Affected’’ Means

One commenter requests clarification

of the meaning of the word ‘‘affected’’

in paragraphs (d) and (f) of the proposed

AD. The commenter states that the

definition provided in the proposed AD

is vague. As an example, the commenter

states that it was not clear whether an

operator needs to obtain a new

inspection method and threshold or

interval for a corrosion blend-out repair

that does not include a doubler to

reinforce the structure.

The FAA concurs that clarification is

necessary. As defined in paragraphs (d)

and (f) of the proposed AD, the term

‘‘affected’’ means that an SSI has been

changed such that the original structure

has been physically modified or that the

loads acting on the SSI have been

increased or redistributed.

For existing altered or repaired SSI’s,

the FAA has determined that it is

evident when an SSI is ‘‘affected’’

because of a physical change to the

structure. For existing changes where

the loads acting on the SSI have been

increased or redistributed, the FAA has

determined that it may not be readily

evident that an SSI is ‘‘affected’’ because

there has not been a physical change to

the structure. Because of this, it may not

be possible for operators to identify all

‘‘affected’’ SSI’s without performing a

damage tolerance assessment. For these

reasons, the FAA has changed

paragraph (d) to require identification of

structure that has been ‘‘physically

altered,’’ rather than ‘‘affected,’’ in

accordance with an STC; and has added

a new paragraph (e) to require

identification of other structure that has

been ‘‘physically altered or repaired.’’

In the cited example of a corrosion

blend-out to an SSI not requiring

reinforcement, the operator would be

required to assess whether the repair

reduced the effectiveness of the original

SSID inspection method and repetitive

interval. However, a blend-out would

not normally reduce the effectiveness of

the original inspection method, because

the structure is essentially unchanged.

The repetitive interval would continue

to be appropriate because the blend-out

would not appreciably affect the

durability of the structure.

After the effective date of this AD,

when SSI’s are altered or repaired or

when the loads acting on an SSI are

increased or redistributed, it should be

evident to the operator that SSI’s are

‘‘affected.’’ The FAA has determined

that, at the time of the installation,

operators should have all the data

necessary to define the repair or

modification that would be used in an

assessment. For this reason, the FAA

has determined that the word ‘‘affected’’

in paragraph (g) [proposed paragraph (f)]

is appropriate.

If an SSI is determined to be

‘‘affected,’’ an operator must perform an

assessment of the damage tolerance

characteristics of the SSI to determine

the effectiveness of the applicable SSID

inspection for that SSI. It is only if that

inspection is determined not to be

effective that the operator must revise

the FAA-approved maintenance or

inspection program to include an

inspection method and compliance

times for that SSI. Accordingly, the FAA

has revised paragraph (d)(1) of the final

rule [which corresponds to paragraph

(d) of the proposed AD as it applied to

STC modified structure] to require the

operator to assess the damage tolerance

characteristics of each SSI created or

affected by each repair or design change

to determine the effectiveness of the

applicable SSID inspection for each SSI.

If it is not effective, the operator is

required to revise the FAA-approved

maintenance or inspection program to

include an inspection method and

compliance times for each new or

affected SSI. The FAA will monitor

operators’ compliance with these

provisions to determine whether future

revisions to this AD are necessary to

fulfill the intent of AC No. 91–56.

Threshold for STC Modified Airplanes

One commenter questions whether

airplanes that have been converted from

a passenger configuration to an all-cargo

configuration by the STC process are

subject to the requirements of paragraph

(c)(1) or (c)(2) of the proposed AD. (This

comment specifically addresses Model

727 airplanes identified in NPRM

Docket No. 96–NM–263–AD; however,

the comment also applies to this AD.)

The commenter’s concern appears to

result from the fact that, when some

passenger airplanes were converted to

cargo airplanes, the modifier revised the

airplane records to reflect a different

model number (e.g., a –200 may be

reidentified as –200C). The FAA’s intent

is that the references to model numbers

in the AD correspond to the model

numbers specified on the type
Federal Register / Vol. 63, No. 96 /Tuesday, May 19, 1998 /Rules and Regulations 27469

certificate data sheet (TCDS). Because

these converted airplanes are not

identified as Model 737–200C series

airplanes on the TCDS, paragraph (c)(1)

does not apply, and paragraph (c)(2)

does. As discussed previously, for SSI’s

altered by the conversion, operators also

must consider the provisions of

paragraph (d) of this AD, which require

a damage tolerance evaluation to

determine what structure needs to be

inspected, what inspection methods are

needed, and when the inspections are to

occur. The FAA has revised the final

rule to include a new NOTE following

paragraph (c)(1) that clarifies this point.

Candidate Fleet Approach

One commenter suggests that the FAA

delete the threshold approach defined

in paragraph (c) of the proposed AD and

retain the candidate fleet approach

defined in AD 84–24–05 and the SSID.

The commenter proposes that the

candidate fleet be updated annually to

reflect changes in the fleet (e.g., when

an airplane is modified from a passenger

configuration to a cargo configuration).

(This comment specifically addresses

Model 727 airplanes identified in NPRM

Docket No. 96–NM–263–AD; however,

the comment also applies to this AD.)

The FAA does not concur. As stated

in the NPRM, the policy established in

AC No. 91–56 anticipated that all SSIP’s

would establish thresholds. The

candidate fleet approach was originally

based on an understanding that the

airplanes in the candidate fleet would

continue to represent the entire fleet

and would have the highest number of

flight cycles in the fleet. This would be

achieved by periodic updates to the

candidate fleet. In practice, this

approach has not fulfilled the intent of

AC No. 91–56. Because of the extensive

modifications and repairs of both

candidate fleet airplanes and noncandidate fleet airplanes, the candidate

fleet is no longer representative.

In addition, the FAA finds that the

candidate fleet no longer includes all of

the highest time airplanes in the fleet.

Even if the SSID were updated annually

to reflect changes to the fleet, this

approach would be impractical for both

operators and the FAA. Because of the

frequency of modifications and changes

in utilization of the affected airplanes,

even annual updates would quickly be

rendered obsolete. Annual changes in

the composition of the candidate fleet

would deprive operators of the

predictability needed for long-term

maintenance planning provided by the

approach of defining the thresholds as

adopted in this AD. For these reasons,

the FAA has determined that the 737

SSIP must contain inspection thresholds

for all Model 737 series airplanes to

ensure the timely detection of fatigue

cracks in the SSI’s.

Extend Compliance Time for Revising

the Maintenance or Inspection Program

Several commenters request that the

compliance time of 12 months in

paragraph (b) of the proposed AD be

extended to provide operators more

time to incorporate Revision D of the

SSID into their FAA-approved

maintenance or inspection program.

These commenters state that an operator

should not be required to revise its

FAA-approved maintenance or

inspection program to incorporate

Revision D of the SSID until its

airplanes are at or near the threshold

specified in paragraph (c) of the

proposed AD. The commenters state

that, as paragraph (b) of the proposed

AD is currently worded, all operators

are required to incorporate the change

regardless of the cycle age of an

airplane. This requirement poses an

undue burden (cost and time) to those

operators that are not required to

inspect until much later. Several other

commenters also state that the safety of

the fleet is not increased by requiring

incorporation of Revision D of the SSID

into an inspection program on low-cycle

airplanes.

The FAA concurs with the

commenters’ requests to extend the

compliance time of paragraph (b) to

prior to reaching the threshold specified

in paragraph (c) of the AD, or within 12

months after the effective date of this

AD, whichever occurs later. The FAA

has revised the final rule accordingly.

However, as discussed previously in

this AD, operators are required to

comply with the requirements of

paragraphs (d) and (g) of this AD, which

may necessitate action before reaching

the threshold.

Extend Grace Period for Initial

Inspections

Several commenters request that the

18-month grace period specified in

paragraph (c) of the proposed AD be

extended to provide operators that are

near or over the threshold more time to

accomplish the initial inspection. Many

inspections included in the SSID

require several work hours to

accomplish. These commenters point

out that the proposed AD allows 12

months to implement Revision D of the

SSID, but allows only 6 months

thereafter to accomplish inspections (18

months total from the effective date).

The commenters contend that

accomplishment of all the inspections

within the 18-month grace period will

significantly affect an operator’s

planned maintenance schedule and

program, especially operators of large

fleets.

Several of these same commenters

state that the original SSID AD 91–14–

20 permitted the initial compliance time

to be the repeat interval (after

incorporation of the revision into a

maintenance or inspection program).

Several commenters also state that other

AD’s that mandate maintenance type

programs, such as the CPCP for aging

airplanes, give operators one repeat

interval to come into compliance;

therefore, the initial inspection should

be similar in concept to such

maintenance type programs (i.e., the

grace period should be 18, 36, 48, 60,

and 72-month intervals depending on

the inspection).

One commenter states that no service,

test, or engineering analysis could

justify the inspection of new SSI’s

within 18 months. Another commenter

states that the approach used in the

proposed AD appeared to be the same

as for a service bulletin with a known

fatigue problem. This commenter also

states that this approach was not

appropriate for damage tolerance based

inspections contained in the Boeing

SSID, which are exploratory inspections

and are not intended to address

identified problems. Another

commenter states that the SSID

threshold is somewhat arbitrary,

because it is based on a reliability

analysis rather than a true fatigue

analysis. The threshold is derived from

calculations that ensure that a

statistically accurate representation of

the fleet is being inspected, rather than

a true crack growth analysis. One of

these commenters suggests that the

grace period be based on flight cycles

instead of calendar time because the

SSID addresses structural fatigue.

Several commenters state that a major

maintenance check would be a more

appropriate grace period for

accomplishing the inspections specified

in the SSID.

The FAA concurs that more time

should be provided to accomplish the

initial inspections specified in

paragraph (c) of the proposed AD.

However, the FAA does not concur that

the grace period should be tied to the

repeat interval established in the Boeing

SSID because some of the repeat

inspections have extremely long

compliance times. The existing Boeing

SSID is not like the CPCP document

which establishes an initial compliance

time (threshold) within the document.

As discussed in Item 3. of the ‘‘Action

Since Issuance of Previous AD’’ Section

of the NPRM, the FAA has determined

that a grace period based on a repeat
27470 Federal Register / Vol. 63, No. 96 /Tuesday, May 19, 1998 /Rules and Regulations

interval does not ensure that the SSI

inspections are accomplished, and that

fatigue cracks in SSI’s are detected, in

a timely manner.

The FAA finds that it would be

appropriate to base the grace period on

the number of accumulated flight cycles

rather than calendar time, because the

Boeing SSIP is based on fatigue and

crack-growth analyses. In addition, the

FAA concurs that the grace period

should begin at the time when operators

are required to have revised their

maintenance or inspection programs to

incorporate Revision D of the SSID. The

FAA has determined that such a grace

period would provide operators with

more time to accomplish the inspection;

yet it also would ensure that the SSI

inspections are accomplished, and that

fatigue cracks in SSI’s are detected, in

a timely manner. As a result, the FAA

has revised the final rule to specify a

grace period of 4,000 flight cycles

measured from the date 12 months after

the effective date of the AD. The 4,000-

flight cycle grace period corresponds to

a typical maintenance interval for most

operators and, therefore, minimizes the

need for special maintenance

scheduling.

Modify Criteria for Adjusting the

Threshold

Several commenters request that the

criteria for adjusting the thresholds

specified in paragraph (c) of the

proposed AD (discussed in Item 3 of the

‘‘Actions Since Issuance of Previous

AD’’ Section of the NPRM) should allow

for the threshold to be reasonably

adjusted. These commenters suggest

that the FAA allow operators to use the

rate of risk methodology to extend the

threshold in the future.

The FAA concurs. The rate of risk

methodology is a means of determining

the probability that cracks will be

detected in the inspected fleet before

they initiate on other airplanes that have

not been inspected. As discussed in the

NPRM, in accordance with paragraph

(i)(1) of the final rule, the FAA would

approve threshold increases if it can be

shown by sufficient data that the

increase in the threshold does not result

in an increased risk that damage will

occur in the uninspected fleet before it

is detected in the inspected fleet.

Some of these commenters state that

the following statement in the NPRM is

unreasonable: ‘‘* * * the FAA may

approve requests for adjustments to the

compliance time * * * provided that no

cracking is detected in the airplane

structure.’’ Confirmed fatigue cracks

should not restrict the ability to adjust

the SSIP threshold. The commenters

state that the present philosophy for

addressing an SSI with a confirmed

fatigue crack is to remove that SSI from

the SSID and to issue a service bulletin

to correct the problem. The FAA then

issues an AD to mandate the action, if

the FAA deems it necessary. Once this

SSI has been removed from the SSID, it

should not affect the ability to adjust the

SSIP threshold. The FAA concurs. In

evaluating requests for extension of

thresholds, the FAA would consider

whether identified cracking has been

addressed in accordance with the

philosophy described by the

commenters.

One commenter expresses concern

that eventually all Model 737 airplanes

would be subject to the Boeing SSIP.

This commenter suggests that the

threshold be defined in the SSID and

managed by the STG. The FAA does not

concur. As discussed previously, if data

are submitted substantiating extension

of the threshold, the FAA will approve

such extensions, which may have the

effect of excepting relatively low-time

airplanes. The FAA would be receptive

to proposals of threshold extensions

from any source that submits sufficient

data, including the STG. Because the

thresholds are specified in the AD itself,

there is no need for the SSID to be

revised to incorporate the threshold.

Compliance Time for Initial Inspection

One commenter requests that the

compliance time for the initial

inspection requirements of paragraphs

(c), (d), and (f) of the proposed AD be

clarified. The commenter asks if there is

anything in the proposed AD that would

establish a threshold for inspections

other than the 46,000-flight cycle

compliance time specified in paragraph

(c)(1) of the proposed AD. The

commenter states that it has Model 727–

100C series airplanes that have

accumulated less than 27,000 total flight

cycles, but are more than 30 years old.

(This comment specifically addresses

Model 727 airplanes identified in NPRM

Docket No. 96–NM–263–AD; however,

the comment also applies to this AD.)

The FAA finds that no change to the

final rule is necessary. The age of an

airplane is irrelevant to the inspection

threshold. Because the inspections are

related to fatigue, only the number of

flight cycles that have accumulated on

an airplane are relevant to the

inspection threshold. If an airplane has

been modified, altered, or repaired, such

as an STC cargo conversion, the results

of an assessment in accordance with

either paragraph (d) or (g) of the AD

could indicate that the initial

inspections are required prior to the

thresholds specified in paragraph (c) of

the AD.

Limit Applicability of the

Transferability Requirement

One commenter concurs with

paragraph (g) of the proposed AD,

which addresses the inspection

schedule for transferred airplanes,

provided that it is limited to airplanes

that have exceeded the threshold

established by paragraph (c)(1) or (c)(2).

Paragraph (h) of the final rule [proposed

paragraph (g)] is limited as stated by the

commenter, and paragraph (h) is

adopted as proposed.

Clarification of FAA-Approved Method

One commenter requests that

paragraph (e) of the proposed AD be

clarified so that there is no confusion

regarding the level of FAA approval

required for repairs to SSI’s. The

commenter states that it interprets

paragraph (e) to mean that any

Designated Engineering Representative

(DER) with delegated authority would

still have the authority to approve

repairs to SSI’s based on a static

strength analysis. The commenter also

interprets that an operator would have

12 months after the repair to develop an

alternative inspection plan, or to

demonstrate that the existing inspection

program provides an acceptable level of

safety.

The commenter is correct that DER’s

still have the authority to approve

repairs to SSI’s based on a static

strength analysis. Except as discussed

under the heading ‘‘Evaluation of

Existing STC Design Changes,’’

paragraph (f) of the final rule [proposed

paragraph (e)] is unchanged from the

corresponding paragraph of AD 91–14–

20. The commenter also is correct that

operators are allowed 12 months after

installation of the repair to revise their

FAA-approved maintenance or

inspection program to include new

inspections for the affected SSI’s. The

new inspection method and compliance

times must be approved by the Manager

of the Seattle ACO.

Delegate Approval Authority to DER’s

Several commenters request that the

FAA delegate approval authority to the

DER’s to approve new inspections and

compliance times specified in

paragraphs (d) and (f) of the proposed

AD. These commenters state that this

delegation would decrease the time

required to obtain such approvals.

These commenters question whether the

FAA will be able to process a

substantial number of requests that will

be generated because of the proposed

AD. This question arises from one

commenter’s past experience with the
Federal Register / Vol. 63, No. 96 /Tuesday, May 19, 1998 /Rules and Regulations 27471

CPCP in which the approval process

took a long period of time.

In the broader context of delegation of

AD required approvals, the FAA has

recently issued guidance on this subject

and will be implementing this guidance

in the near future. Because this request

may be accommodated through FAA

management of designees, no revision to

the final rule is needed.

Credit for Previous Inspections

Several commenters request that

paragraph (c) of the proposed AD

positively reflect that an operator is in

compliance if inspections have been

accomplished in accordance with

Revision D of Boeing Document No. D6–

37089 prior to the effective date of the

AD. These commenters state that

paragraph (c) of the proposed AD is not

clear with regard to whether or not

credit is to be given and when the next

inspection would be required. These

commenters point out that the phrase

‘‘Compliance: Required as indicated,

unless accomplished previously,’’ as

stated in the proposed AD, allows the

necessary credit for previously

accomplished inspections.

The FAA does not consider that a

change to the final rule is necessary.

Operators are given credit for work

previously performed by means of the

phrase in the AD that was referenced by

the commenters. In the case of this AD,

if the initial inspection has been

accomplished prior to the effective date

of this AD, this AD does not require that

it be repeated. However, the AD does

require that repetitive inspections be

conducted thereafter at the intervals

specified in the Boeing SSID, and that

other follow-on actions be accomplished

when indicated.

Further FAA/Industry Discussions

Several commenters request that the

FAA have further discussions with

Boeing, operators, and other regulatory

agencies prior to issuing the final rule

because the proposed AD reflects a

major change in FAA policy and

extends well beyond the original

concept of the Boeing SSIP. The FAA

does not concur. As discussed in the

NPRM and the preceding discussion of

comments, this AD is consistent with

the FAA’s long-standing policy, as

expressed in AC No. 91–56. As

demonstrated by the breadth and depth

of comments received, the public has

had an ample opportunity to comment

on the merits of the proposal.

Cost Estimate

Several commenters request that the

FAA revise the Cost Impact information

of NPRM Docket No. 96–NM–263–AD

(for Model 727 airplanes) and NPRM

Docket No. 96–NM–264–AD (for Model

737 airplanes) to accurately reflect the

costs associated with accomplishing the

requirements of both proposed AD’s.

One commenter states that all affected

737 airplanes worldwide should be

included in the cost estimate in NPRM

Docket No. 96–NM–264–AD. The FAA

does not concur. Airworthiness

directives that are issued by the FAA

directly affect only U.S.-registered

airplanes; therefore, the cost estimate in

an AD is limited only to U.S.-registered

airplanes.

Several commenters to NPRM Docket

No. 96–NM–263–AD (applicable to

Model 727 series airplanes) state that

1,030 Model 727 airplanes (U.S.-

registered) are affected by the proposed

AD, not just 74 airplanes, as specified in

NPRM. One of these commenters states

that the cost estimate in the NPRM does

not reflect the cost for all 727 operators

to incorporate Revision H of the SSID

into an FAA-approved maintenance or

inspection program. Similarly, several

commenters also state that the cost

estimate in NPRM Docket No. 96–NM–

264–AD does not reflect comparable

costs for all 737–100 and –200

airplanes.

The FAA concurs with the

commenters in that the NPRM proposed

that every affected U.S. operator must

revise their maintenance or inspection

programs to incorporate Revision H (for

Model 727 airplanes) or Revision D (for

Model 737 airplanes) of the SSID within

12 months after the effective date of the

applicable AD. As discussed previously

under the heading ‘‘Extend Compliance

Time for Revising the Maintenance or

Inspection Program,’’ the FAA has

revised both final rules so that the

maintenance or inspection program

revision is only required for any

airplane prior to its reaching the

applicable threshold.

In addition, the FAA has revised the

Cost Impact information of Final Rule

Docket No. 96–NM–263–AD to address

a total of 1,001 airplanes, which

includes 223 airplanes (35 operators)

that are estimated to exceed the

thresholds specified in the AD within

the next 10 years. For this final rule, the

FAA also has revised the Cost Impact

information to address a total of 404

airplanes, which includes 158 airplanes

(39 operators) that are estimated to

exceed the thresholds specified in the

AD within the next 10 years. As

discussed previously under the heading

‘‘Modify Criteria for Adjusting the

Threshold,’’ if sufficient substantiating

data are submitted to justify extending

the threshold, the FAA will grant such

extensions so that the operators of some

relatively low utilization airplanes may

never be required to revise their

maintenance or inspection program to

incorporate the SSIP.

One commenter estimates that it will

take 1,700 work hours per airplane (for

Model 727 airplanes) to identify

previously installed repairs, which will

require at least 10 days of downtime to

survey each airplane at a total cost to

the commenter of $8.9 million. This

commenter also estimates that its cost

due to lost revenue would be $10.2

million, for a total cost of $19.1 million

over 6 months (identification and lost

revenue). This commenter further

estimates that it will cost $110.5 million

to survey existing repairs on all 727

airplanes.

Another commenter estimates that it

will cost $240 million to accomplish the

initial inspection to determine if there

are existing repairs on the 727 airplanes.

This task will take over 4,000 work

hours per airplane to accomplish (2,000

work hours to open and close; 500 work

hours to inspect, map, assess, etc.; and

1,500 work hours to complete nonroutines generated by this special

inspection).

Similar comments were submitted to

NPRM Docket No. 96–NM–264–AD;

however, the commenters did not

provide specific cost figures for

performing assessments on existing

repairs.

As discussed under the heading

‘‘Extend Compliance Time for Assessing

Existing Repairs and Boeing

Modifications,’’ the FAA has revised

both final rules to postpone the

requirement to assess existing repairs of

SSI’s until after the applicable SSID

inspection. This revision eliminates the

need for any special inspection in order

to comply with the requirement to

assess repairs.

Several commenters also state that the

cost estimate in the NPRM’s did not

reflect the costs of developing

inspection programs for repairs and

Boeing modifications that are installed

prior to the effective date of the AD. The

FAA concurs and has revised the Cost

Impact information of both final rules to

include (within the total costs) $258,000

per airplane over the next 10 years to

account for these costs.

Several commenters assert that the

cost of the proposed AD is over $100

million, which is more than 20 times

the FAA’s estimate in the NPRM Docket

No. 96–NM–263–AD (for Model 727

airplanes). As discussed below in the

Cost Impact information, the FAA

estimates that the total cost over the

next 10 years associated with this final

rule is $98,044,800, or an average of

$9,804,480 per year. The FAA also
27472 Federal Register / Vol. 63, No. 96 /Tuesday, May 19, 1998 /Rules and Regulations

estimates that the highest total cost

during any one of the next 10 years

associated with this final rule is

$23,916,000. The difference between

these estimates is at least in part

attributable to the changes in the final

rule discussed previously, which

provide significant relief to operators.

(Similar comments were submitted to

NPRM Docket No. 96–NM–264–AD;

however, the commenters did not

provide a total cost estimate for these

actions.)

Additional Clarifications

In reviewing the comments submitted

to the NPRM, questions arose regarding

the relationship of the inspection

threshold requirements of paragraph (c)

of the proposed AD and the provisions

of the Boeing SSID that allow for

sampling of specified percentages of the

affected fleet. As explained in the

NPRM, the FAA’s intent in paragraph

(c) is to require that all airplanes that

exceed the threshold be inspected in

accordance with the Boeing SSID. To

the extent that there is any potential for

conflict between paragraph (c) and the

Boeing SSID, the provisions specified in

this AD would prevail. Therefore, even

if Revision D would permit operators to

omit inspections of SSI’s based on a

sampling approach, this AD requires

that those inspections be performed on

all airplanes exceeding the specified

thresholds. The FAA has revised the

final rule to include a new NOTE

following paragraph (c) to clarify this

point.

Similarly, the FAA notes that

paragraph (b) of the proposed AD would

have required that the revision to the

maintenance or inspection program

include certain SSID provisions that

were proposed to be overridden by other

paragraphs of the proposed AD. The

FAA has revised the requirements of

paragraph (b) to clarify that the AD

overrides these SSID provisions.

The FAA has added a parenthetical

clarification in the applicability of the

final rule to point out that Model 737–

200C series airplanes also are subject to

the requirements of the AD.

Conclusion

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

previously described. The FAA has

determined that these changes will

neither increase the economic burden

on any operator nor increase the scope

of the AD.

Cost Impact

There are approximately 1,007 Boeing

Model 737–100 and –200 series

airplanes of the affected design in the

worldwide fleet. The FAA estimates that

404 airplanes of U.S. registry and 43

U.S. operators (over 10 years) will be

affected by this AD.

Incorporation of the SSID program

into an operator’s maintenance or

inspection program, as required by AD

91–14–20, takes approximately 1,000

work hours per airplane (6 affected

airplanes) to accomplish, at an average

labor rate of $60 per work hour. Based

on these figures, the cost of

incorporating the revised procedures

(specified in Revisions B and C of the

SSID) into the maintenance or

inspection program is estimated to be

$360,000, or $60,000 per airplane.

The recurring inspections, as required

by AD 91–14–20, take approximately

500 work hours per airplane to

accomplish, at an average labor rate of

$60 per work hour. Based on these

figures, the recurring inspection cost to

the 6 U.S.-registered candidate fleet

airplanes is estimated to be $180,000, or

$30,000 per airplane, per inspection

cycle.

The incorporation of Revision D of the

SSID into an operator’s maintenance or

inspection program, as required by this

new AD, takes approximately 1,200

work hours (per operator) to

accomplish, at an average labor rate of

$60 per work hour. The FAA estimates

that within 10 years, 39 operators will

be required to incorporate Revision D of

the SSID. Based on these figures, the

cost of incorporating the revised

procedures (specified in Revision D of

the SSID) into the maintenance or

inspection program is estimated to be

$2,808,000, or $72,000 per operator.

The recurring inspections, as required

by this new AD, take approximately 600

work hours per airplane to accomplish,

at an average labor rate of $60 per work

hour. The FAA estimates that after 10

years, 39 operators will be required to

inspect 146 airplanes and assess the

damage tolerance characteristics of each

repaired SSI or each SSI that is

physically altered by an existing design

change other than an STC. The cost

impact of this inspection and

assessment required by this AD on U.S.

operators is estimated to be $71,328,000

over 10 years, or an average of $48,855

per airplane, per year. During the 10

years, the FAA also conservatively

estimates that 43 operators of 404

airplanes will be required to assess the

damage tolerance characteristics of each

SSI on which the structure identified in

Revision D of the SSID has been

physically altered in accordance with an

STC prior to the effective date of this

AD. The cost impact of this assessment

required by this AD on U.S. operators is

estimated to be $21,000,000 over 10

years, or an average of $5,198 per

airplane, per year.

In summary, the FAA estimates that

the actions, as required by this new AD,

will cost $98,044,800 over 10 years, or

an average of $9,804,480 per year. The

FAA also estimates that the average cost

per airplane over 10 years is $242,685,

or an average of $24,269 per year. The

highest total cost during any one of the

10 years is $23,916,000. (The FAA has

included in the Rules Docket a detailed

description of cost estimates related to

the actions required by this AD.)

The cost impact figures discussed

above are based on assumptions that no

operator has yet accomplished any of

the requirements of this AD action, and

that no operator would accomplish

those actions in the future if this AD

were not adopted. However, it can

reasonably be assumed that the majority

of the affected operators have already

initiated the original SSID program (as

required by AD 91–14–20), and many

may have already initiated the

additional inspections required by this

new AD action.

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 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.
Federal Register / Vol. 63, No. 96 /Tuesday, May 19, 1998 /Rules and Regulations 27473

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. 106(g), 40113, 44701.

§ 39.13 [Amended]

2. Section 39.13 is amended by

removing amendment 39–7061 (56 FR

30680, July 5, 1991), and by adding a

new airworthiness directive (AD),

amendment 39–10531, to read as

follows:

98–11–04 Boeing: Amendment 39–10531.

Docket 96–NM–264–AD. Supersedes AD

91–14–20, Amendment 39–7061.

Applicability: All Model 737–100 and –200

series airplanes (including Model 737–200C

series airplanes), certificated in any category.

Compliance: Required as indicated, unless

accomplished previously.

To ensure the continued structural

integrity of the total Boeing Model 727 fleet,

accomplish the following:

Note 1: Where there are differences

between the AD and the Supplemental

Structural Inspection Document, the AD

prevails.

(a) For airplanes listed in Section 3.0 of

Boeing Document No. D6–37089,

‘‘Supplemental Structural Inspection

Document’’ (SSID), Revision B, dated

February 18, 1987, and Revision C, dated

January 1990: Within 12 months after August

9, 1991 (the effective date of AD 91–14–20,

amendment 39–7061), incorporate a revision

into the FAA-approved maintenance

inspection program which provides no less

than the required damage tolerance rating

(DTR) for each Structural Significant Item

(SSI) listed in that document. (The required

DTR value for each SSI is listed in the

document.) The revision to the maintenance

program shall include and shall be

implemented in accordance with the

procedures in Sections 5.0 and 6.0 of the

SSID. This revision shall be deleted

following accomplishment of the

requirements of paragraph (b) of this AD.

Note 2: For the purposes of this AD, an SSI

is defined as a principal structural element

that could fail and consequently reduce the

structural integrity of the airplane.

(b) Prior to reaching the threshold specified

in paragraph (c) of this AD, or within 12

months after the effective date of this AD,

whichever occurs later, incorporate a

revision into the FAA-approved maintenance

or inspection program that provides no less

than the required DTR for each SSI listed in

Boeing Document No. D6–37089,

‘‘Supplemental Structural Inspection

Document’’ (SSID), Revision D, dated June

1995 (hereinafter referred to as ‘‘Revision

D’’). (The required DTR value for each SSI is

listed in the document.) Except as provided

to the contrary in paragraphs (c), (d), and (g)

of this AD, the revision to the maintenance

or inspection program shall include and shall

be implemented in accordance with the

procedures in Section 5.0, ‘‘Damage

Tolerance Rating (DTR) System Application’’

and Section 6.0, ‘‘SSI Discrepancy

Reporting’’ of Revision D. Upon

incorporation of the revision required by this

paragraph, the revision required by

paragraph (a) of this AD may be deleted.

(c) Except as provided in paragraph (d), (e),

or (g) of this AD, perform an inspection to

detect cracks in all structure identified in

Revision D at the time specified in paragraph

(c)(1) or (c)(2) of this AD, as applicable.

(1) For Model 737–200C series airplanes:

Inspect prior to the accumulation of 46,000

total flight cycles, or within 4,000 flight

cycles measured from the date 12 months

after the effective date of this AD, whichever

occurs later.

Note 3: The requirements specified in

paragraph (c)(1) of this AD only apply to

airplanes listed as 737–200C on the type

certificate data sheet. Paragraph (c)(1) does

not apply to airplanes that have been

modified from a passenger configuration to

an all-cargo configuration by supplemental

type certificate (STC). Paragraphs (c)(2) and

(d) apply to those airplanes.

(2) For all airplanes, except for those

airplanes identified in paragraph (c)(1) of this

AD: Inspect prior to the accumulation of

66,000 total flight cycles, or within 4,000

flight cycles measured from the date 12

months after the effective date of this AD,

whichever occurs later.

Note 4: Notwithstanding the provisions of

paragraphs 5.1.1, 5.1.2, 5.1.6(e), .1.11, 5.1.12,

5.1.13, 5.2, 5.2.1, 5.2.2, 5.2.3, and 5.2.4 of the

General Instructions of Revision D, which

would permit operators to perform fleet and

rotational sampling inspections, to perform

inspections on less than whole airplane fleet

sizes and to perform inspections on

substitute airplanes, this AD requires that all

airplanes that exceed the threshold be

inspected in accordance with Revision D.

Note 5: Once the initial inspection has

been performed, operators are required to

perform repetitive inspections at the intervals

specified in Revision D in order to remain in

compliance with their maintenance or

inspection programs, as revised in

accordance with paragraph (b) of this AD.

(d) For airplanes on which the structure

identified in Revision D has been physically

altered in accordance with an STC prior to

the effective date of this AD: Accomplish the

requirements specified in paragraph (d)(1) or

(d)(2) of this AD.

(1) Within 18 months after the effective

date of this AD, assess the damage tolerance

characteristics of each SSI created or affected

by each STC to determine the effectiveness

of the applicable Revision D inspection for

each SSI and, if not effective, revise the FAAapproved maintenance or inspection program

to include an inspection method for each

new or affected SSI, and to include the

compliance times for initial and repetitive

accomplishment of each inspection.

Following accomplishment of the revision

and within the compliance times established,

perform an inspection to detect cracks in the

structure affected by any design change or

repair, in accordance with the new

inspection method. The new inspection

method and the compliance times shall be

approved by the Manager, Seattle Aircraft

Certification Office (ACO), FAA, Transport

Airplane Directorate.

Note 6: For purposes of this AD, an SSI is

‘‘affected’’ if it has been physically altered or

repaired, or if the loads acting on the SSI

have been increased or redistributed. The

effectiveness of the applicable inspection

method and compliance time should be

determined based on a damage tolerance

assessment methodology, such as that

described in FAA Advisory Circular AC No.

91–56, Change 2, dated April 15, 1983.

(2) Accomplish paragraphs (d)(2)(i),

(d)(2)(ii), and (d)(2)(iii) of this AD.

(i) Within 18 months after the effective

date of this AD, submit a plan that describes

a methodology for accomplishing the

requirements of paragraph (d)(1) of this AD

to the Manager, Seattle ACO, 1601 Lind

Avenue, SW., Renton, Washington 98055–

4056; fax (425) 227–1181.

Note 7: The plan should include a detailed

description of the: STC; methodology for

identifying new or affected SSI’s; method for

developing loads and validating the analysis;

methodology for evaluating and analyzing

the damage tolerance characteristics of each

new or affected SSI; and proposed inspection

method. The plan would not need to include

all of these elements if the operator can

otherwise demonstrate that its plan will

enable the operator to comply with paragraph

(d)(2)(iii) of this AD.

(ii) Within 18 months after the effective

date of this AD, perform a detailed visual

inspection in accordance with a method

approved by the Manager, Seattle ACO to

detect cracks in all structure identified in

Revision D that has been altered by an STC.

(A) If no crack is detected, repeat the

detailed visual inspection thereafter at

intervals not to exceed 18 months.

(B) If any crack is detected, prior to further

flight, repair it in accordance with a method

approved by the Manager, Seattle ACO.

(iii) Within 48 months after the effective

date of this AD, revise the FAA-approved

maintenance or inspection program to

include an inspection method for each new

or affected SSI, and to include the

compliance times for initial and repetitive

accomplishment of each inspection. The

inspection methods and the compliance

times shall be approved by the Manager,

Seattle ACO. Accomplishment of the actions

specified in this paragraph constitutes

terminating action for the repetitive
27474 Federal Register / Vol. 63, No. 96 /Tuesday, May 19, 1998 /Rules and Regulations

inspection requirements of paragraph

(d)(2)(ii)(A) of this AD.

Note 8: Notwithstanding the provisions of

paragraphs 5.1.17 and 5.1.18 of the General

Instructions of Revision D, which would

permit deletions of modified, altered, or

repaired structure from the SSIP, the

inspection of SSI’s that are modified, altered,

or repaired shall be done in accordance with

a method approved by the Manager, Seattle

ACO.

(e) For airplanes on which the structure

identified in Revision D has been repaired or

physically altered by any design change other

than an STC identified in paragraph (d), prior

to the effective date of this AD: At the time

of the first inspection of each SSI after the

effective date of this AD in accordance with

Revision D, identify each repair or design

change to that SSI. Within 12 months after

such identification, assess the damage

tolerance characteristics of each SSI created

or affected by each repair or design change

to determine the effectiveness of the

applicable SSID inspection for each SSI and,

if not effective, revise the FAA-approved

maintenance or inspection program to

include an inspection method and

compliance times for each new or affected

SSI. The new inspection method and the

compliance times shall be approved by the

Manager, Seattle ACO.

Note 9: For the purposes of this AD, a

design change is defined as any modification,

alteration, or change to operating limitations.

(f) Except as provided in paragraph

(d)(2)(ii)(B) of this AD, cracked structure

found during any inspection required by this

AD shall be repaired, prior to further flight,

in accordance with an FAA-approved

method.

(g) For airplanes on which the structure

identified in Revision D is affected by any

design change (including STC’s) or repair

that is accomplished after the effective date

of this AD: Within 12 months after that

modification, alteration, or repair, revise the

FAA-approved maintenance or inspection

program to include an inspection method

and compliance times for each new or

affected SSI, and to include the compliance

times for initial and repetitive

accomplishment of each inspection. The new

inspection method and the compliance times

shall be approved by the Manager, Seattle

ACO.

Note 10: Notwithstanding the provisions of

paragraphs 5.1.17 and 5.1.18 of the General

Instructions of Revision D, which would

permit deletions of modified, altered, or

repaired structure from the SIP, the

inspection of SSI’s that are modified, altered,

or repaired shall be done in accordance with

a method approved by the Manager, Seattle

ACO.

(h) Before any airplane that is subject to

this AD and that has exceeded the applicable

compliance times specified in paragraph (c)

of this AD can be added to an air carrier’s

operations specifications, a program for the

accomplishment of the inspections required

by this AD must be established in accordance

with paragraph (h)(1) or (h)(2) of this AD, as

applicable.

(1) For airplanes that have been inspected

in accordance with this AD, the inspection of

each SSI must be accomplished by the new

operator in accordance with the previous

operator’s schedule and inspection method,

or the new operator’s schedule and

inspection method, whichever would result

in the earlier accomplishment date for that

SSI inspection. The compliance time for

accomplishment of this inspection must be

measured from the last inspection

accomplished by the previous operator. After

each inspection has been performed once,

each subsequent inspection must be

performed in accordance with the new

operator’s schedule and inspection method.

(2) For airplanes that have not been

inspected in accordance with this AD, the

inspection of each SSI required by this AD

must be accomplished either prior to adding

the airplane to the air carrier’s operations

specification, or in accordance with a

schedule and an inspection method approved

by the Manager, Seattle ACO. After each

inspection has been performed once, each

subsequent inspection must be performed in

accordance with the new operator’s schedule.

(i)(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, Seattle

ACO. Operators shall submit their requests

through an appropriate FAA Principal

Maintenance Inspector, who may add

comments and then send it to the Manager,

Seattle ACO.

Note 11: Information concerning the

existence of approved alternative methods of

compliance with this AD, if any, may be

obtained from the Seattle ACO.

(i)(2) Alternative methods of compliance,

approved previously in accordance with AD

91–14–20, amendment 39–7061, are not

considered to be approved as alternative

methods of compliance with this AD.

(j) 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.

(k) The actions specified in paragraphs (b)

and (c) shall be done in accordance with

Boeing Document No. D6–37089,

‘‘Supplemental Structural Inspection

Document’’ (SSID), Revision D, dated June

1995, which contains the following list of

effective pages:

Page number shown on page

Revision

level

shown on

page

List of Effective Pages Pages 1

thru 10.

D.

Note: The issue date of Revision D is

indicated only on the title page; no other

page of the document is dated.) 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 Boeing

Commercial Airplane Group, P.O. Box 3707,

Seattle, Washington 98124–2207. Copies may

be inspected at the FAA, Transport Airplane

Directorate, 1601 Lind Avenue, SW., Renton,

Washington; or at the Office of the Federal

Register, 800 North Capitol Street, NW., suite

700, Washington, DC.

(l) This amendment becomes effective on

June 23, 1998.

Issued in Renton, Washington, on May 12,

1998.

D.L. Riggin,

Acting Manager, Transport Airplane

Directorate, Aircraft Certification Service.

[FR Doc. 98–13078 Filed 5–18–98; 8:45 am]

BILLING CODE 4910–13–U

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 71

[Airspace Docket No. 98–ACE–17]

Amendment to Class D and Class E

Airspace; Fort Leonard Wood, MO

AGENCY: Federal Aviation

Administration (FAA), DOT.

ACTION: Direct final rule; request for

comments.

SUMMARY: This action amends the Class

D and Class E airspace areas at Fort

Leonard Wood, Forney Army Airfield,

MO. The FAA has developed Global

Positioning System (GPS) Runway

(RWY) 14; GPS RWY 32; Localizer

(LOC) RWY 14; Nondirectional Radio

Beacon (NDB) RWY 14; NDB RWY 32;

VHF Omnidirectional Range (VOR)

RWY 14; and VOR RWY 32 Standard

Instrument Approach Procedures

(SIAPs) to serve Fort Leonard Wood,

Forney Army Airfield, MO. The

enlarged Class E surface area and Class

E airspace area 700 feet Above Ground

Level (AGL) will contain the new SIAPs

within controlled airspace. A minor

revision to the Airport Reference Point

(ARP) coordinates is included in this

document. The intended effect of this

rule is to revise the ARP coordinates

and to provide additional controlled

Class E airspace for aircraft operating

under Instrument Flight Rules (IFR).

DATES: Effective date: 0901 UTC,

October 8, 1998.

Comments for inclusion in the Rules

Docket must be received on or before

July 1, 1998.

ADDRESSES: Send comments regarding

the rule in triplicate to: Manager,

Airspace Branch, Air Traffic Division,

ACE–520, Federal Aviation