Airworthiness Directives; Boeing Model 757 Series Airplanes Equipped With Pratt and Whitney Engines

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-NM-72-AD]

Airworthiness Directives; Boeing Model 757 Series Airplanes

Equipped With Pratt and Whitney Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the supersedure of an existing

airworthiness directive (AD), applicable to certain Boeing Model 757

series airplanes, that currently requires repetitive inspections to

detect cracking in the midspar fuse pins and replacement of certain

fuse pins. This action would require inspecting straight fuse pins and

replacing cracked straight fuse pins with either new corrosion-

resistant steel fuse pins or like pins, replacing bulkhead fuse pins

with new corrosion-resistant steel fuse pins, and repetitively

inspecting newly installed fuse pins. This proposal is prompted by the

development of new corrosion-resistant steel fuse pins. The actions

specified by the proposed AD are intended to prevent cracking of the

midspar fuse pins, which may lead to separation of the strut and engine

from the wing of the airplane.

DATES: Comments must be received by October 3, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 94-NM-72-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.

FOR FURTHER INFORMATION CONTACT: Carrie Sumner, Aerospace Engineer,

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

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

Washington 98055-4056; telephone (206) 227-2778; 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-72-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-72-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

On August 17, 1993, the FAA issued AD 93-16-09, amendment 39-8666

(58 FR 45044, August 26, 1993), applicable to certain Boeing Model 757

series airplanes, to require repetitive inspections to detect cracking

in the midpsar fuse pins and replacement of certain fuse pins with new

or refinished fuse pins. That action was prompted by reports of cracked

fuse pins found on in-service airplanes. The requirements of that AD

are intended to prevent separation of the strut and engine from the

wing of the airplane.

Since the issuance of that AD, the manufacturer has developed new

15-5PH corrosion-resistant steel fuse pins. Test data have shown that

these new fuse pins have a longer service life. Therefore, the FAA has

determined that the inspection interval for these new pins can be

increase significantly without compromising safety.

Further, the FAA has reviewed the service experience of affected

in-service airplanes and has found that consistent quality of the fuse

pins cannot be ensured during the refinishing process of the fuse pins.

Consequently, refinished straight fuse pins, currently allowed by AD

93-16-09 as suitable replacement fuse pins, are no longer considered to

be suitable replacements.

Cracked fuse pins, if not corrected, could result in separation of

the strut and engine from the wing of the airplane.

The FAA has reviewed and approved Boeing Service Bulletin 757-

54A0019, Revision 5, dated March 17, 1994, which describes procedures

for eddy current inspection to detect cracking in straight fuse pins,

replacement of cracked straight fuse pins with either new 15-5PH pins

or like pins, replacement of bulkhead fuse pins with new 15-5PH

corrosion-resistant steel fuse pins, and repetitive eddy current

inspections to detect cracking in the newly installed fuse pins.

Since an unsafe condition has been identified that is likely to

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

proposed AD would supersede AD 93-16-09 to require inspection of

straight fuse pins, replacement of cracked straight fuse pins with

either new 15-5PH corrosion-resistant steel fuse pins or like pins,

replacement of bulkhead fuse pins with new 15-5PH corrosion-resistant

steel fuse pins, and repetitive inspections of newly installed fuse

pins. Installation of the steel fuse pins would allow a longer

repetitive inspection interval than was previously provided by AD 93-

16-09. The actions would be required to be accomplished in accordance

with the service bulletin described previously.

There are approximately 273 Model 757 series airplanes equipped

with Pratt and Whitney engines of the affected design in the worldwide

fleet. The FAA estimates that 237 airplanes of U.S. registry would be

affected by this proposed AD.

The inspections that were previously required by AD 93-16-09, and

retained in this proposal take approximately 8 work hours per fuse pin

at an average labor rate of $55 per work hour. There are 4 fuse pins

per airplane. Based on these figure, the total cost impact of these

inspections on U.S. operators is estimated to be $417,120, or $1,760

per airplane, per cycle. However, since the integrity and strength of

the new steel fuse pins permit longer inspection intervals, the cost

impact for these inspections would actually be lessened because the

proposed inspections are not required to be performed as frequently as

currently required by AD 93-16-09.

The proposed replacement would take approximately 56 work hours per

fuse pin at an average labor rate of $55 per work hour. Required parts

would be provided by the manufacturer at no cost to the operator. Based

on these figures, the total cost impact of the proposed replacement on

U.S. operators is estimated to be $2,919,840, or $12,320 per airplane.

The total 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 expensive. 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, most

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 this 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.

The regulations proposed herein would not have substantial direct

effects on the States, on the relationship between the national

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

responsibilities among the various levels of government. Therefore, in

accordance with Executive Order 12612, it is determined that this

proposal would not have sufficient federalism implications to warrant

the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this proposed

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

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

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

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

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

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

regulatory evaluation prepared for this action is contained in the

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

Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration proposes to amend

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

follows:

PART 39--AIRWORTHINESS DIRECTIVES -

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

Authority: 49 U.S.C. 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 removing amendment 39-8666 (58 FR

45044, August 26, 1993), and by adding a new airworthiness directive

(AD), to read as follows:

Boeing: Docket 94-NM-72-AD. Supersedes AD 93-16-09, Amendment

39-8666. -

Applicability: Model 757 series airplanes equipped with Pratt

and Whitney engines, certificated in any category. -

Compliance: Required as indicated, unless accomplished

previously.

Note 1: Inspections accomplished prior to the effective date of

this amendment in accordance with the procedures described in Boeing

Service Bulletin 757-54A0019, Revision 4, dated May 27, 1993,

Revision 3, dated March 26, 1992, or Revision 2, dated October 11,

1989, are considered acceptable for compliance with the applicable

inspection specified in this amendment. -

To prevent cracking of the midspar fuse pins, which may lead to

separation of the strut and engine from the wing of the airplane,

accomplish the following:

(a) For airplanes equipped with straight fuse pins, part number

(P/N) 311N5067-1: Prior to the accumulation of 3,800 total flight

cycles on the straight fuse pin, perform an eddy current inspection

to detect cracking in those fuse pins, in accordance with Boeing

Service Bulletin 757-54A0019, Revision 5, dated March 17, 1994.

(1) If no cracking is detected, repeat the inspection thereafter

at intervals not to exceed 1,000 flight cycles on the straight fuse

pin.

(2) If any cracking is detected, prior to further flight,

accomplish the requirements of either paragraph (a)(2)(i) or

(a)(2)(ii) of this AD.

(i) Replace the cracked straight fuse pins with new straight

fuse pin, P/N 311N5067-1, and prior to the accumulation of 3,800

total flight cycles on the newly installed straight fuse pin,

perform an eddy current inspection, in accordance with the service

bulletin. Repeat the inspection thereafter at intervals not to

exceed 1,000 flight cycles on the newly installed straight fuse pin.

Or

(ii) Replace the cracked straight fuse pin with new 15-5PH fuse

pin, P/N 311N5217-1, and prior to the accumulation of 14,000 total

flight cycles on the newly installed 15-5PH fuse pin, perform an

eddy current inspection to detect cracking in the newly installed

pin, in accordance with the service bulletin. Repeat the inspection

thereafter at intervals not to exceed 3,000 flight cycles on the

newly installed fuse pin.

(b) For airplanes equipped with bulkhead fuse pins, P/N

311N5211-1: Within 90 days after the effective date of this AD,

replace bulkhead fuse pins with 15-5PH fuse pins, P/N 311N5217, in

accordance with Boeing Service bulletin 757-54A0019, Revision 5,

dated March 17, 1994, and accomplish the requirements of paragraph

(c) of this AD.

(c) For airplanes equipped with 15-5PH fuse pins: Prior to the

accumulation of 14,000 total flight cycles on the 15-5PH fuse pins,

perform an eddy current inspection to detect cracking in those fuse

pins, in accordance with Boeing Service Bulletin 757-54A0019,

Revision 5, dated March 17, 1994.

(1) If no cracking is detected, repeat the inspection thereafter

at intervals not to exceed 3,000 flight cycles on the fuse pin.

(2) If any cracking is detected, accomplish the requirements of

paragraphs (c)(2)(i) and (c)(2)(ii) of this AD.

(i) Prior to further flight, replace any cracked 15-5PH fuse pin

with a new 15-5PH fuse pin, P/N 311N5217-1, in accordance with the

service bulletin.

(ii) Prior to the accumulation of 14,000 total flight cycles on

the newly installed 15-5PH fuse pin, perform an eddy current

inspection to detect cracking in the newly installed pin, in

accordance with the service bulletin. Repeat the inspection

thereafter at intervals not to exceed 3,000 flight cycles on the

newly installed fuse pin.

(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. -

(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 August 2, 1994.

James V. Devany,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-19351 Filed 8-8-94; 8:45 am]

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