Airworthiness Directives; Boeing Model 747 Series Airplanes Equipped With General Electric Model CF6-80C2 Series Engines or Pratt & Whitney Model PW4000 Series Engines

Proposed Rules

Federal Register

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Proposed Rules

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-NM-224-AD]

Airworthiness Directives; Boeing Model 747 Series Airplanes

Equipped With General Electric Model CF6-80C2 Series Engines or Pratt &

Whitney Model PW4000 Series Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness

directive (AD) that is applicable to certain Boeing Model 747 series

airplanes. This proposal would require modification of the nacelle

strut and wing structure, inspections and checks to detect

discrepancies, and correction of discrepancies. This proposal is

prompted by the development of a modification of the strut and wing

structure that improves the fail-safe capability and durability of the

strut-to-wing attachments, and reduces reliance on inspections of those

attachments. The actions specified by the proposed AD are intended to

prevent failure of the strut and subsequent loss of the engine.

DATES: Comments must be received by March 3, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Transport Airplane Directorate, ANM-103,

Attention: Rules Docket No. 94-NM-224-AD, 1601 Lind Avenue, SW.,

Renton, Washington 98055-4056. Comments may be inspected at this

location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except

Federal holidays.

The service information referenced in the proposed rule may be

obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle,

Washington 98124-2207. This information may be examined at the FAA,

Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton,

Washington.

may be inspected at this

location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except

Federal holidays.

The service information referenced in the proposed rule may be

obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle,

Washington 98124-2207. This information may be examined at the FAA,

Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton,

Washington.

FOR FURTHER INFORMATION CONTACT: Tim Backman, Aerospace Engineer,

Airframe Branch, ANM-121S, FAA, Transport Airplane Directorate, Seattle

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

Washington 98055-4056; telephone (206) 227-2776; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the

proposed rule by submitting such written data, views, or arguments as

they may desire. Communications shall identify the Rules Docket number

and be submitted in triplicate to the address specified above. All

communications received on or before the closing date for comments,

specified above, will be considered before taking action on the

proposed rule. The proposals contained in this notice may be changed in

light of the comments received.

Comments are specifically invited on the overall regulatory,

economic, environmental, and energy aspects of the proposed rule. All

comments submitted will be available, both before and after the closing

date for comments, in the Rules Docket for examination by interested

persons. A report summarizing each FAA-public contact concerned with

the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments

submitted in response to this notice must submit a self-addressed,

stamped postcard on which the following statement is made: ``Comments

to Docket Number 94-NM-224-AD.'' The postcard will be date stamped and

returned to the commenter.

Availability of NPRMs

th

the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments

submitted in response to this notice must submit a self-addressed,

stamped postcard on which the following statement is made: ``Comments

to Docket Number 94-NM-224-AD.'' The postcard will be date stamped and

returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request

to the FAA, Transport Airplane Directorate, ANM-103, Attention: Rules

Docket No. 94-NM-224-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

The FAA has received numerous reports of fatigue cracking and/or

corrosion in the strut-to-wing attachments on Boeing Model 747 series

airplanes. In two cases, cracking resulted in the failure of a strut

load path and the subsequent loss of the number 3 engine and strut. In

both cases, catastrophic accidents occurred when the number 3 engine

and strut separated from the wing of the airplane and struck the number

4 engine, causing it to separate from the airplane. Investigation into

the cause of these accidents and other reported incidents has revealed

that fatigue cracks and corrosion in the strut-to-wing attachments, if

not detected and corrected in a timely manner, can result in failure of

the strut and subsequent separation of the engine from the airplane.

Investigation also has revealed that the structural fail-safe

capability of the strut-to-wing attachment is inadequate on these

airplanes.

The FAA has previously issued 3 airworthiness directives (AD's)

that address various problems associated with the strut attachment

assembly on Model 747 series airplanes equipped with General Electric

Model CF6-80C2 series engines or Pratt & Whitney Model PW4000 series

engines. These AD's have required, among other things, inspection of

the strut, midspar fittings, diagonal brace, and midspar fuse pins.

Explanation of Service Information

irectives (AD's)

that address various problems associated with the strut attachment

assembly on Model 747 series airplanes equipped with General Electric

Model CF6-80C2 series engines or Pratt & Whitney Model PW4000 series

engines. These AD's have required, among other things, inspection of

the strut, midspar fittings, diagonal brace, and midspar fuse pins.

Explanation of Service Information

Boeing recently has developed a modification of the strut-to-wing

attachment structure installed on certain Model 747 series airplanes

equipped with General Electric Model CF6-80C2 series engines or Pratt &

Whitney Model PW4000 series engines that significantly improves the

load-carrying capability and durability of the strut-to-wing

attachments. Such improvement also will substantially reduce the

possibility of fatigue cracking and corrosion developing in the

attachment assembly.

The FAA has reviewed and approved Boeing Alert Service Bulletin

747-54A2156, dated December 15, 1994, which describes procedures for

modification of the nacelle strut and wing structure. This modification

entails the following:

1. Providing a new fail-safe load path by installing a new dual

side load fitting to the strut and the underwing structure and the

associated wing back-up fitting, front spar post, and side links;

2. Installing a new titanium dual side load fitting to the strut

aft bulkhead and new 15-5 stainless steel midspar

fittings;

3. Replacing the aft bulkhead assembly and overhaul of the spring

beam;

4. Improving the strut-to-wing attachments by replacing the upper

link and the diagonal brace;

5. Reworking the rib of wing station (WS)1140; and

6. Modifying the electrical wiring and hydraulics by rerouting

certain wire bundles around the new dual side load fitting and

installing new hydraulic tubes

idspar

fittings;

3. Replacing the aft bulkhead assembly and overhaul of the spring

beam;

4. Improving the strut-to-wing attachments by replacing the upper

link and the diagonal brace;

5. Reworking the rib of wing station (WS)1140; and

6. Modifying the electrical wiring and hydraulics by rerouting

certain wire bundles around the new dual side load fitting and

installing new hydraulic tubes.

This alert service bulletin specifies that the modification of the

nacelle strut and wing structure is to be accomplished prior to, or

concurrently with, the terminating actions described in the service

bulletins listed in paragraph I.C., Table 2, ``Prior or Concurrent

Service Bulletins,'' on page 7 of this alert service bulletin. These

terminating actions include the following:

1. Replacement of the diagonal brace, midspar, and upper link fuse

pins with new third generation 15-5 corrosion resistant steel fuse

pins;

2. Inspection and replacement of the bearings on the lower spar

fitting of the outboard engine strut with new bearings;

3. Installation of improved bushings in the strut-to-wing attach

fittings; and

4. Inspection and rework of improperly torqued fasteners.

Paragraph III, NOTES 8, 9, 10, and 11 of the Accomplishment

Instructions on page 91 of the alert service bulletin also describe

procedures for inspections and checks to detect discrepancies of the

adjacent structure, and correction of any discrepancies.

Explanation of the Provisions of the Proposed AD

rut-to-wing attach

fittings; and

4. Inspection and rework of improperly torqued fasteners.

Paragraph III, NOTES 8, 9, 10, and 11 of the Accomplishment

Instructions on page 91 of the alert service bulletin also describe

procedures for inspections and checks to detect discrepancies of the

adjacent structure, and correction of any discrepancies.

Explanation of the Provisions of the Proposed AD

Since an unsafe condition has been identified that is likely to

exist or develop on other products of this same type design, the

proposed AD would require modification of the nacelle strut and wing

structure, inspections and checks to detect discrepancies in the

adjacent structure, and correction of discrepancies. The actions would

be required to be accomplished in accordance with the alert service

bulletin described previously.

The FAA has determined that long term continued operational safety

will be better assured by design changes to remove the source of the

problem, rather than by repetitive inspections. Long term inspections

may not be providing the degree of safety assurance necessary for the

transport airplane fleet. This, coupled with a better understanding of

the human factors associated with numerous continual inspections, has

led the FAA to consider placing less emphasis on inspections and more

emphasis on design improvements. The proposed modification requirement

is in consonance with these considerations.

Accomplishment of the modification of the nacelle strut and wing

structure would terminate the inspections currently required by the

following AD's:

the AD. If an airplane has been altered

or repaired in the affected area in such a way as to affect compliance

with the AD, the owner or operator is required to obtain FAA approval

for an alternative method of compliance with the AD, in accordance with

the paragraph of each AD that provides for such approvals. A note has

been included in this notice to clarify this requirement.

Cost Estimate

There are approximately 257 Model 747 series airplanes equipped

with General Electric Model CF6-80C2 series engines or Pratt & Whitney

Model PW4000 series engines of the affected design in the worldwide

fleet. The FAA estimates that 36 airplanes of U.S. registry would be

affected by this proposed AD.

The proposed modification would take approximately 6,253 work hours

per airplane to accomplish, at an average labor cost of $60 per work

hour. The manufacturer would incur the cost of labor, on a prorated

basis, with 20 years being the expected life of these airplanes. The

total cost impact of the proposed AD on U.S. operators is based on the

median age for the fleet of Model 747 series airplanes equipped with

General Electric Model CF6-80C2 series engines or Pratt & Whitney Model

PW4000 series engines, which is estimated to be 5 years. Required parts

would be supplied by the manufacturer at no cost to the operators.

Based on these figures, the total cost impact of the proposed AD on

U.S. operators is estimated to be $3,376,620, or $93,795 per airplane.

This cost impact figure does not reflect the cost of the

terminating actions described in the service bulletins listed in

paragraph I.C., Table 2, ``Prior or Concurrent Service Bulletins,'' on

page 7 of Boeing Alert Service Bulletin 747-54A2156, dated December 15,

1994, that are proposed to be accomplished prior to, or concurrently

with, the modification of the nacelle strut and wing structure

his cost impact figure does not reflect the cost of the

terminating actions described in the service bulletins listed in

paragraph I.C., Table 2, ``Prior or Concurrent Service Bulletins,'' on

page 7 of Boeing Alert Service Bulletin 747-54A2156, dated December 15,

1994, that are proposed to be accomplished prior to, or concurrently

with, the modification of the nacelle strut and wing structure. Since

some operators may have accomplished certain modifications on some or

all of the airplanes in its fleet, while other operators may not have

accomplished any of the modifications on any of the airplanes in its

fleet, the FAA is unable to provide a reasonable estimate of the cost

of accomplishing the terminating actions described in the service

bulletins listed in Table 2 of the Boeing alert service bulletin. As

indicated earlier in this preamble, the FAA invites comments

specifically on the overall economic aspects of this proposed rule. Any

data received via public comments to this notice will aid the FAA in

developing an accurate accounting of the cost impact of the rule.

The cost impact figure discussed above is based on assumptions that

no operator has yet accomplished any of the proposed requirements of

this AD action, and that no operator would accomplish those actions in

the future if this AD were not adopted.

The FAA recognizes that the obligation to maintain aircraft in an

airworthy condition is vital, but sometimes excessive. Because AD's

require specific actions to address specific unsafe

conditions, they appear to impose costs that would not otherwise be

borne by operators. However, because of the general obligation of

operators to maintain aircraft in an airworthy condition, this

appearance is deceptive. Attributing those costs solely to the issuance

of this AD is unrealistic because, in the interest of maintaining safe

aircraft, prudent operators would accomplish the required actions even

if they were not required to do so by the AD

ise be

borne by operators. However, because of the general obligation of

operators to maintain aircraft in an airworthy condition, this

appearance is deceptive. Attributing those costs solely to the issuance

of this AD is unrealistic because, in the interest of maintaining safe

aircraft, prudent operators would accomplish the required actions even

if they were not required to do so by the AD.

A full cost-benefit analysis has not been accomplished for this

proposed AD. As a matter of law, in order to be airworthy, an aircraft

must conform to its type design and be in a condition for safe

operation. The type design is approved only after the FAA makes a

determination that it complies with all applicable airworthiness

requirements. In adopting and maintaining those requirements, the FAA

has already made the determination that they establish a level of

safety that is cost-beneficial. When the FAA, as in this proposed AD,

makes a finding of an unsafe condition, this means that the original

cost-beneficial level of safety is no longer being achieved and that

the proposed actions are necessary to restore that level of safety.

Because this level of safety has already been determined to be cost-

beneficial, a full cost-benefit analysis for this proposed AD would be

redundant and unnecessary.

Regulatory Impact

The regulations proposed herein would not have substantial direct

effects on the States, on the relationship between the national

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

responsibilities among the various levels of government. Therefore, in

accordance with Executive Order 12612, it is determined that this

proposal would not have sufficient federalism implications to warrant

the preparation of a Federalism Assessment

ubstantial direct

effects on the States, on the relationship between the national

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

responsibilities among the various levels of government. Therefore, in

accordance with Executive Order 12612, it is determined that this

proposal would not have sufficient federalism implications to warrant

the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this proposed

regulation (1) is not a ``significant regulatory action'' under

Executive Order 12866; (2) is not a ``significant rule'' under the DOT

Regulatory Policies and Procedures (44 FR 11034, February 26, 1979);

and (3) if promulgated, will not have a significant economic impact,

positive or negative, on a substantial number of small entities under

the criteria of the Regulatory Flexibility Act. A copy of the draft

regulatory evaluation prepared for this action is contained in the

Rules Docket. A copy of it may be obtained by contacting the Rules

Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration proposes to amend

part 39 of the Federal Aviation Regulations (14 CFR part 39) as

follows:

PART 39--AIRWORTHINESS DIRECTIVES

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

Authority: 49 U.S.C. 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:

Boeing: Docket 94-NM-224-AD.

Applicability: Model 747 series airplanes having line positions

679 through 1046 inclusive, equipped with General Electric Model

CF6-80C2 series engines or Pratt & Whitney Model PW4000 series

engines; certificated in any category.

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:

Boeing: Docket 94-NM-224-AD.

Applicability: Model 747 series airplanes having line positions

679 through 1046 inclusive, equipped with General Electric Model

CF6-80C2 series engines or Pratt & Whitney Model PW4000 series

engines; certificated in any category.

Note 1: This AD applies to each airplane identified in the

preceding applicability provision, regardless of whether it has been

modified, altered, or repaired in the area subject to the

requirements of this AD. For airplanes that have been modified,

altered, or repaired so that the performance of the requirements of

this AD is affected, the owner/operator must use the authority

provided in paragraph (d) to request approval from the FAA. This

approval may address either no action, if the current configuration

eliminates the unsafe condition; or different actions necessary to

address the unsafe condition described in this AD. Such a request

should include an assessment of the effect of the changed

configuration on the unsafe condition addressed by this AD. In no

case does the presence of any modification, alteration, or repair

remove any airplane from the applicability of this AD.

Compliance: Required as indicated, unless accomplished

previously.

To prevent failure of the strut and subsequent loss of the

engine, accomplish the following:

de an assessment of the effect of the changed

configuration on the unsafe condition addressed by this AD. In no

case does the presence of any modification, alteration, or repair

remove any airplane from the applicability of this AD.

Compliance: Required as indicated, unless accomplished

previously.

To prevent failure of the strut and subsequent loss of the

engine, accomplish the following:

(a) Within 80 months after the effective date of this AD,

accomplish the modification of the nacelle strut and wing structure

in accordance with Boeing Alert Service Bulletin 747-54A2156, dated

December 15, 1994. All of the terminating actions described in the

service bulletins listed in paragraph I.C., Table 2, ``Prior or

Concurrent Service Bulletins,'' on page 7 of Boeing Alert Service

Bulletin 747-54A2156, dated December 15, 1994, must be accomplished

in accordance with those service bulletins prior to, or concurrently

with, the accomplishment of the modification of the nacelle strut

and wing structure required by this paragraph.

(b) Perform the inspections and checks specified in paragraph

III, NOTES 8, 9, 10, and 11 of the Accomplishment Instructions on

page 91 of Boeing Alert Service Bulletin 747-54A2156, dated December

15, 1994, concurrently with the modification of the nacelle strut

and wing structure required by paragraph (a) of this AD. Prior to

further flight, correct any discrepancies in accordance with the

alert service bulletin.

ions and checks specified in paragraph

III, NOTES 8, 9, 10, and 11 of the Accomplishment Instructions on

page 91 of Boeing Alert Service Bulletin 747-54A2156, dated December

15, 1994, concurrently with the modification of the nacelle strut

and wing structure required by paragraph (a) of this AD. Prior to

further flight, correct any discrepancies in accordance with the

alert service bulletin.

(c) Accomplishment of the modification of the nacelle strut and

wing structure in accordance with Boeing Alert Service Bulletin 747-

54A2156, dated December 15, 1994, constitutes terminating action for

the inspections required by the following AD's:

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Amendment Federal Register Date of

AD No. No. citation publication

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93-17-07............... 39-8678 58 FR 45827..... Aug. 31, 1993.

93-03-14............... 39-8518 58 FR 14513..... Mar. 18, 1993.

92-24-51............... 39-8439 57 FR 60118..... Dec. 18, 1992.

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(d) An alternative method of compliance or adjustment of the

compliance time that provides an acceptable level of safety may be

used if approved by the Manager, Seattle Aircraft Certification

Office (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 2: Information concerning the existence of approved

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

obtained from the Seattle ACO.

le Aircraft Certification

Office (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 2: Information concerning the existence of approved

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

obtained from the Seattle ACO.

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

sections 21.197 and 21.199 of the Federal Aviation Regulations (14

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

the requirements of this AD can be accomplished.

Issued in Renton, Washington, on December 30,

1994.

S.R. Miller,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 95-307 Filed 1-5-95; 8:45 am]

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