Airworthiness Directives; Boeing Model 727 Series Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 91-NM-65-AD; Amendment 39-8802; AD 94-04-04]

Airworthiness Directives; Boeing Model 727 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD),

applicable to all Boeing Model 727 series airplanes, that requires

inspections of certain fuselage frames for cracks, and modification, if

necessary; inspections to detect cracks in certain frame gussets, and

replacement, if necessary; and inspections at certain body stations to

detect open pilot holes and to detect cracks in any open pilot hole

found, and repair and modification, if necessary. This amendment is

prompted by reports of cracked frames and open pilot holes. The actions

specified by this AD are intended to prevent frame failures and

consequent rapid decompression of the cabin.

DATES: Effective March 3, 1994.

The incorporation by reference of certain publications listed in

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

of March 3, 1994.

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: Phil Forde, Aerospace Engineer,

Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle

Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,

Washington 98055-4056; telephone (206) 227-2771; fax (206) 227-1181.

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

Aviation Regulations to include an airworthiness directive (AD) that is

applicable to all Boeing Model 727 series airplanes was published as a

supplemental notice of proposed rulemaking (NPRM) in the Federal

Register on May 7, 1993 (58 FR 27217). That action proposed to require

inspections of certain fuselage frames for cracks, and modification, if

necessary; inspections to detect cracks in certain frame gussets, and

replacement, if necessary; and inspections at certain body stations to

detect open pilot holes and to detect cracks in any open pilot hole

found, and repair and modification, if necessary.

Interested persons have been afforded an opportunity to participate

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

the comments received.

One commenter supports the proposed rule.

One commenter, Boeing, requests that the proposed rule be withdrawn

and suggests that the service bulletin cited in the proposal be

incorporated into the structural modification and inspection program

for aging airplanes. Boeing references a similar situation involving

the overwing stub frames on Model 737 series airplanes. No AD was

issued in that instance; instead, the preventive modification was made

part of the aging fleet modification program at life goal. Boeing also

states that including the service bulletin cited in the proposal in the

modification program would reduce the number of AD's concerning that

subject.

Boeing also believes that the consequence of frame failures was

overstated in the proposal. Boeing indicates that although dozens of

cases of basic frame cracking have occurred, only four cases of inboard

strap cracking and no cases of frame outboard reinforcing strap

cracking have been reported. Boeing adds that for rapid decompression

to occur, the skin must crack; and there have been no reports of skin

cracks in this area as a result of frame cracks. Boeing believes that

rapid decompression is extremely unlikely because there is ample

reinforcing structure in this area.

The FAA does not concur with the commenter's request to withdraw

the proposal. Although there have been no reports of outboard strap or

skin cracking, the FAA has determined that the potential exists for

failure of the frames, which could lead to failure of the straps and

skin in the absence of the repair and preventive modification or

inspection program. Such failures would result in rapid decompression

of the airplane. The FAA finds that it is not warranted to delay the

proposed repair for inclusion in the aging airplane program.

The Air Transport Association (ATA) of America, on behalf of two of

its members, requests that the FAA reconsider the proposed requirement

of this AD to remove fasteners prior to inspection and, if necessary,

require another inspection to verify the existence of cracks without

fastener removal. One commenter suggests that an option should be

included in the final rule that would allow visual inspections at more

frequent intervals in lieu of the proposed fastener removal and eddy

current inspections. Another commenter suggests that fastener removal

should be required only during the initial inspection, and that

subsequent inspections should be accomplished using visual and high

frequency eddy current inspection methods. This commenter states that

accomplishment of these suggested subsequent inspections will ensure

that a crack does not reach a critical length. ATA expresses concern

that continual removal of fasteners may initiate crack development.

The FAA does not concur with the commenters' requests to revise the

intervals or procedures specified in this AD for inspections involving

fastener removal. The FAA has reconsidered various alternatives to the

inspection methods and intervals specified in this AD in light of

available crack growth analysis data. The FAA finds that eddy current

inspections with fasteners in place would be required at intervals of

1,500 flight cycles, or four times as often as the interval of 6,000

flight cycles (with fasteners removed) specified in this AD. Further,

the FAA finds that if fastener removal were only required during the

initial inspection and subsequent eddy current inspections with

fasteners in place were required, the first inspection interval would

be 6,000 flight cycles with subsequent inspection intervals of 1,500

flight cycles. In light of the safety implications and practical

aspects of an orderly inspection of the fleet during regular

maintenance periods, the FAA considers inspections with fasteners

removed at intervals of 6,000 flight cycles to be the appropriate

requirement for this AD. However, the FAA would consider a request for

an adjustment of the inspection methods or intervals, in accordance

with the provisions of paragraph (e) of this AD, provided that, for

example, data is submitted to substantiate that such methods or

intervals ensure that cracks will not reach a critical length.

One commenter requests that credit be given in paragraph (d) of the

proposal for inspections to detect open pilot holes performed in

accordance with the original issue of the service bulletin. The

commenter asks specifically that the proposal be revised to state that

repairs accomplished in accordance with the Model 727 Structural Repair

Manual (SRM) are acceptable, provided repetitive inspections are

performed thereafter at intervals of 6,000 flight cycles. This

commenter has inspected the addressed area in accordance with the

original issue of the service bulletin. The commenter indicates that

the area targeted for inspection in paragraph (d) of the proposal is

essentially the same area identified in the original issue of the

service bulletin. The commenter is confident that any cracks in the

pilot holes would have been detected during that inspection (and

subsequently repaired) in accordance with that issue of the service

bulletin. The commenter adds that airplanes inspected in accordance

with the original issue of the service bulletin may have been repaired

in accordance with chapter 51-40-3 of the SRM, as specified in that

service bulletin. The commenter states that Boeing has not included a

reference to the SRM repair in Revision 1 of the service bulletin

because the SRM repair is not easily adapted to the subject frames.

However, Revision 1 of the service bulletin indicates that repairs

installed in accordance with the original issue of the service bulletin

are adequate as long as repetitive inspections are accomplished.

Similarly, one commenter requests that paragraphs (b) and (c) of

the proposal, which address (in part) inspections of the fastener

holes, the frame flange and web, and certain frame gussets, be revised

to allow credit for inspections accomplished previously in accordance

with the original issue of the service bulletin in that the proposed

compliance time should be longer for airplanes that have been inspected

previously in accordance with the original issue of the service

bulletin than for those airplanes that have not been inspected. The

commenter states that any cracks in the pilot holes would have been

detected during inspections accomplished in accordance with the

original issue of the service bulletin.

The FAA does not concur with the commenters' requests to allow

credit for inspections accomplished in accordance with the procedures

described in the original issue of the service bulletin. The original

issue of the service bulletin does not contain procedures for

inspections to detect cracks in open pilot holes, which is a

requirement of this AD. Consequently, the FAA cannot be certain that

operators that accomplished procedures specified in the original issue

of the service bulletin also inspected for and repaired cracks in open

pilot holes, as required by this AD.

Another commenter requests that plugging uncracked pilot holes in

accordance with Part VII of the service bulletin be considered optional

terminating action for the repetitive inspections proposed in paragraph

(d)(2)(i) of this AD. The FAA does not concur. The location of pilot

holes in the members of the built-up structure has been shown to vary;

therefore, since all of the open pilot holes may not be visible during

an inspection, it is possible that ``figure 8 holes'' could exist on

the inner members of that structure. These figure 8 holes are two holes

that have not been drilled concentrically. The danger of figure 8 holes

is that they have been shown to create very high local stress. In light

of this hazard, the FAA cannot allow plugging uncracked pilot holes to

be considered terminating action for the repetitive inspections

discussed previously.

This commenter also requests that reference to Part VI of the

Accomplishment Instructions of the service bulletin be removed from

paragraph (d)(2) of the proposal. The commenter states that the

procedures described in Part VI of the Accomplishment Instructions of

the service bulletin are not applicable to this paragraph of the

proposal.

The FAA concurs partially. The FAA's intent in referring to Part VI

of the Accomplishment Instructions of the service bulletin was simply

to specify that the appropriate inspection technique to be performed is

a close visual inspection, which is referenced in Part VI of the

Accomplishment Instructions of the service bulletin. However, the FAA

recognizes that clarification of this inspection method is necessary.

Therefore, paragraph (d)(2) of this final rule has been revised by

removing reference to Part VI of the Accomplishment Instructions of the

service bulletin and by specifying that a ``close visual inspection''

is defined as a close intensive visual inspection of highly defined

structural details or locations, searching for evidence of structural

irregularity and using adequate lighting. In addition, inspection aids

such as mirrors, etc., surface cleaning, and access procedures are

required, as necessary, to gain proximity.

The commenter also requests that paragraph (d)(2)(iii) be revised

to delete the phrase, ``in accordance with * * * the service

bulletin.'' The commenter states that repair of any crack found in an

open pilot hole that is located outside any of the shaded areas shown

in Figures 3, 4, and 5 of the service bulletin cannot be separated from

the preventive modification.

The FAA does not concur. Repair of a crack in an open pilot hole

and installation of the preventive modification are two different

items. While the service bulletin contains instructions for repairing

cracks, it does not specify how to install the modification if the

cracked pilot hole is located outside the shaded area covered by the

service bulletin. Consequently, operators are required to request

approval from the FAA of a method of installing the modification.

The final rule has been revised to correct certain typographical

errors in regard to paragraph and service information references, as

follows:

1. Paragraph (d)(1) has been revised to clarify that if no open

pilot hole is found, no further action is required by paragraph (d) of

this AD.

2. Paragraph (d)(2)(i) of this AD has been changed to refer to

paragraphs (d)(2)(ii) and (d)(2)(iii), rather than paragraphs

(d)(1)(ii) and (d)(1)(iii), respectively.

3. Paragraph (d)(2)(ii) of this AD has been revised to refer to

paragraph (d)(2)(i), rather than paragraph (d)(1)(i).

4. Paragraph (d)(2)(iii) of this AD has been changed to refer to

paragraph (d)(2)(i), rather than paragraph (d)(1)(i).

Additionally, for consistency with the service bulletin, paragraphs

(a) and (b) of this AD have been revised to include the word ``repair''

where any reference is made to the preventive modification. This word

is added to clarify the FAA's intent that when cracks are found,

operators must install the applicable ``repair and preventive

modification.''

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.

There are approximately 1,695 Model 727 series airplanes of the

affected design in the worldwide fleet. The FAA estimates that 1,172

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

take approximately 53 work hours per airplane to accomplish the

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

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

operators is estimated to be $3,416,380, or $2,915 per airplane. This

total cost figure assumes that no operator has yet accomplished the

requirements of this AD.

The regulations adopted herein will not have substantial direct

effects on the States, on the relationship between the national

government and the States, or on the distribution of power and

responsibilities among the various levels of government. Therefore, in

accordance with Executive Order 12612, it is determined that this final

rule does not have sufficient federalism implications to warrant the

preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (1) is

not a ``significant regulatory action'' under Executive Order 12866;

(2) is not a ``significant rule'' under DOT Regulatory Policies and

Procedures (44 FR 11034, February 26, 1979); and (3) will not have a

significant economic impact, positive or negative, on a substantial

number of small entities under the criteria of the Regulatory

Flexibility Act. A final evaluation has been prepared for this action

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

from the Rules Docket at the location provided under the caption

ADDRESSES.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by

reference, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration amends 14 CFR part

39 of the Federal Aviation Regulations as follows:

PART 39--AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

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

106(g); and 14 CFR 11.89.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

94-04-04 Boeing: Amendment 39-8802. Docket 91-NM-65-AD.

Applicability: All Model 727 series airplanes, certificated in

any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent failure of fuselage frames and depressurization of

the airplane, accomplish the following:

(a) For airplanes identified as Group 1 or 2 in Boeing Service

Bulletin 727-53-0197, Revision 1, dated April 9, 1992: Prior to the

accumulation of 12,000 flight cycles since manufacture, or within

3,000 flight cycles after the effective date of this AD, whichever

occurs later, perform an eddy current inspection of the fastener

holes and a close visual inspection of the frame flange and web to

detect cracks at body stations (BS) 760.95, 783.95, 825.95, and

848.95 in accordance with Part I of the Accomplishment Instructions

of the service bulletin.

(1) If any crack is found, prior to further flight, install the

applicable repair and preventive modification in accordance with

Part III of the Accomplishment Instructions of the service bulletin.

Once this repair and preventive modification is installed, no

further eddy current inspections of the fastener holes or close

visual inspections of the modified frame flange and web are required

by this AD.

(2) If no crack is found, prior to further flight, accomplish

one of the procedures identified in paragraphs (a)(2)(i),

(a)(2)(ii), or (a)(2)(iii) of this AD, in accordance with Part I,

paragraph E., of the Accomplishment Instructions of the service

bulletin.

(i) Oversize the hole by \1/32\ inch and install an oversized

fastener. Prior to the accumulation of 12,000 flight cycles after

oversizing the hole, and thereafter at intervals not to exceed 6,000

flight cycles, continue to accomplish the inspections required by

paragraph (a) of this AD. If any crack is found, prior to further

flight, install the applicable repair and preventive modification in

accordance with Part III of the Accomplishment Instructions of the

service bulletin. Once this repair and preventive modification is

installed, no further eddy current inspections of the fastener holes

or close visual inspections of the frame flange and web are required

by this AD. Or

(ii) Install the same size fastener that was removed. Thereafter

at intervals not to exceed 6,000 flight cycles, continue to

accomplish the inspections required by paragraph (a) of this AD. If

cracks are found, prior to further flight, install the applicable

repair and preventive modification in accordance with Part III of

the Accomplishment Instructions of the bulletin. Once this repair

and preventive modification is installed, no further eddy current

inspections of the fastener holes or close visual inspections of the

frame flange and web are required by this AD. Or

(iii) Install the applicable repair and preventive modification

in accordance with Part III of the Accomplishment Instructions of

the service bulletin. Once this repair and preventive modification

is installed, no further eddy current inspections of the fastener

holes or close visual inspections of the frame flange and web are

required by this AD.

(b) For airplanes identified as Group 3, 4, or 5 in Boeing

Service Bulletin 727-53-0197, Revision 1, dated April 9, 1992: Prior

to the accumulation of 12,000 flight cycles since manufacture, or

within 3,000 flight cycles after the effective date of this AD,

whichever occurs later, perform an eddy current inspection of the

fastener holes and a close visual inspection of the frame flange and

web to detect cracks at body stations (BS) 760.95 and 783.95 in

accordance with Part II of the Accomplishment Instructions of the

service bulletin.

(1) If any crack is found, prior to further flight, install the

applicable repair and preventive modification in accordance with

Part IV of the Accomplishment Instructions of the service bulletin.

Once this repair and preventive modification is installed, no

further eddy current inspections of the fastener holes or close

visual inspections of the frame flange and web are required by this

AD.

(2) If no crack is found, prior to further flight, accomplish

one of the procedures identified in paragraphs (b)(2)(i),

(b)(2)(ii), or (b)(2)(iii) of this AD, in accordance with Part II,

paragraph E. of the Accomplishment Instructions of the service

bulletin:

(i) Oversize the hole by \1/32\ inch and install an oversized

fastener. Prior to the accumulation of 12,000 flight cycles after

oversizing the hole, and thereafter at intervals not to exceed 6,000

flight cycles, continue to accomplish the inspections required by

paragraph (b) of this AD. If cracks are found, prior to further

flight, install the applicable repair and preventive modification in

accordance with Part IV of the Accomplishment Instructions of the

service bulletin. Once this repair and preventive modification is

installed, no further eddy current inspections of the fastener holes

or close visual inspections of the frame flange and web are required

by this AD. Or

(ii) Install the same size fastener that was removed. Thereafter

at intervals not to exceed 6,000 flight cycles, continue to

accomplish the inspections required by paragraph (b) of this AD. If

cracks are found, prior to further flight, install the applicable

repair and preventive modification in accordance with Part IV of the

Accomplishment Instructions of the service bulletin. Once this

repair and preventive modification is installed, no further eddy

current inspections of the fastener holes or close visual

inspections of the frame flange and web are required by this AD. Or

(iii) Install the applicable repair and preventive modification

in accordance with Part IV of the Accomplishment Instructions of the

service bulletin. Once this repair and preventive modification is

installed, no further eddy current inspections of the fastener holes

or close visual inspections of the frame flange and web are required

by this AD.

(c) For airplanes identified as Group 1, 2, 3, or 4 in Boeing

Service Bulletin 727-53-0197, Revision 1, dated April 9, 1992: Prior

to the accumulation of 12,000 flight cycles since manufacture, or

within 3,000 flight cycles after the effective date of this AD,

whichever occurs later, perform a close visual inspection to detect

cracks in the frame gussets at BS 825.95 in accordance with Part V

(for Groups 1 and 2 airplanes) or Part VI (for Groups 3 and 4

airplanes) of the Accomplishment Instructions of the service

bulletin. Repeat these inspections thereafter at intervals not to

exceed 6,000 flight cycles.

(1) If any crack is found, prior to further flight, replace the

gusset with a new gusset in accordance with Figure 10 (for Groups 1

and 2 airplanes) or Figure 11 (for Groups 3 and 4 airplanes) of the

service bulletin.

(2) Replacement of the gusset in accordance with paragraph

(c)(1) of this AD constitutes terminating action for the repetitive

inspections required by paragraph (c) of this AD.

(d) For airplanes identified as Group 1, 2, 3, 4, or 5 in Boeing

Service Bulletin 727-53-0197, Revision 1, dated April 9, 1992: Prior

to the accumulation of 12,000 flight cycles since manufacture, or

within 3,000 flight cycles after the effective date of this AD,

whichever occurs later, perform a close visual inspection of the

inner flange of the frames and the strap on the inner flange at BS

760.95 and 783.95 to detect open pilot holes in accordance with Part

VII of the Accomplishment Instructions of the service bulletin.

(1) If no open pilot hole is found, no further action is

required by paragraph (d) of this AD.

(2) If any open pilot hole is found, perform a close visual

inspection to detect cracks in that open pilot hole. A ``close

visual inspection'' is defined as a close, intensive visual

inspection of highly defined structural details or locations,

searching for evidence of structural irregularity and using adequate

lighting. In addition, inspection aids such as mirrors, etc.,

surface cleaning, and access procedures are required, as necessary,

to gain proximity.

(i) If no crack is found in any open pilot hole, repeat the

inspection required by paragraph (d)(2) of this AD thereafter at

intervals not to exceed 6,000 flight cycles until the preventive

modification specified in paragraph (d)(2)(ii) or (d)(2)(iii) of

this AD, as applicable, is installed.

(ii) If any crack is found in an open pilot hole that is located

inside any of the shaded areas shown in Figures 3, 4, and 5 of the

service bulletin, prior to further flight, repair the crack in the

pilot hole and install a preventive modification in accordance with

Part III or IV of the Accomplishment Instructions of the service

bulletin. Installation of a preventive modification constitutes

terminating action for the repetitive inspections of the open pilot

holes specified in paragraph (d)(2)(i) of this AD.

(iii) If any crack is found in an open pilot hole that is

located outside any of the shaded areas shown in Figures 3, 4, and 5

of the service bulletin, prior to further flight, repair the crack

in the pilot hole in accordance with part III or IV of the

Accomplishment Instructions of the service bulletin, and install a

preventive modification in accordance with a method approved by the

Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport

Airplane Directorate. Installation of a preventive modification

constitutes terminating action for the repetitive inspections of the

open pilot holes specified in paragraph (d)(2)(i) of this AD.

(e) 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, FAA, Transport

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, Seattle ACO.

Note: Information concerning the existence of approved

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

obtained from the Seattle ACO.

(f) Special flight permits may be issued in accordance with FAR

21.197 and 21.199 to operate the airplane to a location where the

requirements of this AD can be accomplished.

(g) The actions shall be done in accordance with Boeing Service

Bulletin 727-53-0197, Revision 1, dated April 9, 1992. This

incorporation by reference was approved by the Director of the

Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part

51. Copies may be obtained from 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.

(h) This amendment becomes effective on March 3, 1994.

Issued in Renton, Washington, on January 12, 1994.

John J. Hickey,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-1226 Filed 1-31-94; 8:45 am]

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