Airworthiness Directives; Boeing Model 747 Series Airplanes, Excluding Airplanes Equipped with Pratt & Whitney PW4000 and General Electric CF6-80C2 Series Engines

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-NM-123-AD]

Airworthiness Directives; Boeing Model 747 Series Airplanes,

Excluding Airplanes Equipped with Pratt & Whitney PW4000 and General

Electric CF6-80C2 Series Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

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 replacement of certain fuse pins

on the upper link of the inboard and outboard struts. This AD also

would require inspections to detect corrosion or cracks of certain fuse

pins, and replacement, if necessary. This proposal is prompted by

reports of cracked or corroded fuse pins on the upper link of the

inboard and outboard struts, which could result in fracturing of the

pins. The actions specified by the proposed AD are intended to prevent

failure of the strut and separation of an engine from the airplane due

to fracturing of the fuse pins.

DATES: Comments must be received by January 10, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 94-NM-123-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: Tim Backman, Aerospace Engineer,

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

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

Washington 98055-4056; telephone (206) 227-2776; 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-123-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-123-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion -

The FAA received several reports of cracked fuse pins on the upper

link of the inboard and outboard struts on Boeing Model 747 series

airplanes. Several pins also showed evidence of corrosion. The fuse

pins involved in these reports were ``bottle bore style'' fuse pins

installed in the forward position of the struts. The cracking initiated

in a machining groove in the inner recess of the pin bore, and it

propagated due to fatigue. Cracking of the pins occurred on some

airplanes as early as 9,366 total flight cycles (on the airplane) and

42,493 total flight hours. One of the reports involved the complete

fracture of both shear planes on the fuse pin; consequently, that pin

had no load carrying capability. Analysis of several of the cracked

fuse pins indicated that fracturing occurred in the recess area of the

pin bore. -

Corrosion may cause cracking of the fuse pins; this could lead to

fracturing of the fuse pins. This condition, if not corrected, could

result in failure of the strut and separation of an engine from the

airplane. -

The FAA has reviewed and approved Boeing Alert Service Bulletin

747-54A2166, dated April 28, 1994, which describes procedures for

replacement of ``bulkhead style'' and ``bottle bore style'' fuse pins,

installed in the forward position of the upper link on the inboard and

outboard struts, with either a 15-5 corrosion-resistant steel fuse pin

(also known as a ``third generation'' pin) or a new bulkhead style pin.

(This alert service bulletin specifies that installation of the third

generation pin is preferred.) The alert service bulletin also describes

procedures for repetitive detailed visual inspections to detect

corrosion of the bulkhead style pins; magnetic particle inspections to

detect cracks in these pins; and replacement of any cracked or corroded

pin with a third generation pin or a new bulkhead style pin. -

The alert service bulletin references Boeing Service Bulletin 747-

54-2155, dated September 23, 1993, as an additional source of service

information for replacement of certain fuse pins, installed in the

forward and aft positions of the upper link, with third generation

pins. (Although there have been no reports of cracked pins in the aft

position, replacement of the pin in the forward position with a third

generation pin necessitates that the aft pin also be replaced with a

third generation pin in order to preserve the function and location of

the primary structural fuse.) -

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 replacement of bottle bore style fuse pins,

installed in the forward position of the upper link on the inboard and

outboard struts, with either third generation fuse pins or new bulkhead

style pins. This proposed AD also would require repetitive detailed

visual inspections to detect corrosion of bulkhead style fuse pins;

magnetic particle inspections to detect cracks in those pins; and

replacement of any corroded or cracked bulkhead style fuse pin with a

third generation fuse pin or with a new bulkhead style pin.

Installation of a third generation fuse pin, if accomplished, would

constitute terminating action for the inspection requirements of the

proposed AD. The actions would be required to be accomplished in

accordance with the alert service bulletin described previously. -

The manufacturer has advised that it is currently developing a

modification program for the engine strut that will positively address

the unsafe condition addressed by this AD. Once this modification

program is developed, approved, and available, the FAA may consider

additional rulemaking.

There are approximately 869 Model 747 series airplanes of the

affected design in the worldwide fleet. The FAA estimates that 147

airplanes of U.S. registry would be affected by this proposed AD. -

It would take approximately 122 work hours per airplane to

accomplish the proposed replacement of fuse pins with bulkhead style

pins. The average labor rate is $60 per work hour. Based on these

figures, the total cost impact on U.S. operators who replace fuse pins

with bulkhead style pins is estimated to be $7,320 per airplane. -

It would take approximately 140 work hours per airplane to

accomplish the proposed replacement of fuse pins with third generation

pins. The average labor rate is $60 per work hour. Based on these

figures, the total cost impact on U.S. operators who replace fuse pins

with third generation pins is estimated to be $8,400 per airplane. -

It would take approximately 1.5 work hours per airplane to

accomplish the proposed inspections (in addition to the work hours

necessary for fuse pin replacement). The average labor rate is $60 per

work hour. Based on these figures, the total cost impact on U.S.

operators for the proposed inspections is estimated to be $90 per

airplane per inspection. -

The cost of required replacement parts would vary from airplane to

airplane, depending upon the current airplane configuration. -

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 number of required work hours, as indicated above, is presented

as if the accomplishment of the proposed inspection and replacement

actions were to be conducted as ``stand alone'' actions. However, in

actual practice, these actions, for the most part, would be

accomplished coincidentally or in combination with normally scheduled

airplane inspections and other maintenance program tasks. Therefore,

the actual number of necessary additional work hours would be minimal

in many instances. Additionally, any costs associated with special

airplane scheduling would be minimal. -

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,

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. -

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 adding the following new

airworthiness directive:

Boeing: Docket 94-NM-123-AD.

Applicability: Model 747 series airplanes; line numbers 1

through 967 inclusive, and 969 through 992 inclusive; excluding

airplanes equipped with Pratt & Whitney PW4000 or General Electric

CF6-80C2 series engines; certificated in any category.

Note 1: This AD does not require that the actions be

accomplished on the struts of airplanes having straight bore fuse

pins (installed on Model 747 series airplanes equipped with Pratt &

Whitney PW4000 or General Electric CF6-80C2 series engines) or 15-5

corrosion resistant steel (third generation) fuse pins.

Compliance: Required as indicated, unless accomplished

previously.

To prevent failure of the strut and loss of an engine due to

corrosion or cracking of the fuse pins, accomplish the following:

(a) For airplanes having bottle bore style fuse pins in the

forward position on the upper link: Replace any bottle bore style

fuse pin with a new bulkhead style fuse pin in the forward position,

or with 15-5 corrosion resistant steel (third generation) fuse pins

in the forward position, in accordance with Boeing Alert Service

Bulletin 747-54A2166, dated April 28, 1994, at the later of the

times specified in paragraphs (a)(1) and (a)(2) of this AD.

(1) Prior to the accumulation of 5,000 landings on the fuse pin,

or within 5 years since installation of the pin, whichever occurs

first. Or

(2) Within 6 months after the effective date of this AD.

Note 2: Third generation fuse pins are installed in pairs (in

the forward and aft positions). Therefore, replacement of an

individual upper link fuse pin in the forward position with a third

generation pin also would necessitate replacement of the pin in the

aft position.

Note 3: The alert service bulletin references Boeing Service

Bulletin 747-54-2155, dated September 23, 1993, as an additional

source of service information for replacement of the fuse pins with

15-5 corrosion resistant steel (third generation) fuse pins.

Installation of these third generation fuse pins is preferred over

installation of bulkhead style fuse pins.

(b) For airplanes having bulkhead style fuse pins in the forward

position on the upper link: Perform a detailed visual inspection to

detect corrosion of the pins, and a magnetic particle inspection to

detect cracks, in accordance with Boeing Alert Service Bulletin 747-

54A2166, dated April 28, 1994, at the later of the times specified

in paragraphs (b)(1) and (b)(2) of this AD.

(1) Prior to the accumulation of 8,000 landings on the fuse pin,

or within 8 years since installation of the pin, whichever occurs

first. Or

(2) Within 12 months after the effective date of this AD.

(c) If no corrosion or crack is found during the inspection

required by paragraph (b) of this AD, repeat the inspections

thereafter at the intervals specified in paragraph (c)(1) or (c)(2)

of this AD, as applicable.

(1) For the inboard and outboard struts on airplanes other than

those identified in paragraph (c)(2) of this AD: Repeat the

inspections at intervals not to exceed 1,000 landings.

(2) For the outboard struts on airplanes equipped with Rolls-

Royce RB211-524G or -524H series engines: Repeat the inspections at

intervals not to exceed 2,000 landings.

Note 4: The outboard struts of airplanes equipped with Rolls-

Royce RB211-524G or -524H series engines are equipped with thick

wall ``4330 steel'' bulkhead style fuse pins in the forward position

of the upper link. Crack propagation to critical length in these

thick wall pins is slower than for pins installed on the struts of

airplanes equipped with engines other than the Rolls-Royce RB211-

524G or -524H series.

(d) If any corrosion or crack is found during any inspection

required by this AD, prior to further flight, replace the corroded

or cracked pin with either a new bulkhead style fuse pin in the

forward position of the upper link, or with 15-5 corrosion resistant

steel (third generation) fuse pins in the forward and aft positions

of the upper link, in accordance with Boeing Alert Service Bulletin

747-54A2166, dated April 28, 1994.

(1) If the corroded or cracked fuse pin is replaced with a new

bulkhead style fuse pin, prior to the accumulation of 8,000 landings

on the new pin, or within 8 years since installation of the new pin,

whichever occurs first, perform a detailed visual inspection to

detect corrosion of the new pin, and a magnetic particle inspection

to detect cracks of the new pin, in accordance with Boeing Alert

Service Bulletin 747-54A2166, dated April 28, 1994. Repeat these

inspections thereafter at the interval specified in paragraph

(d)(1)(i) or (d)(1)(ii) of this AD, as applicable.

(i) For the inboard and outboard struts on airplanes other than

those identified in paragraph (d)(1)(ii) of this AD: Repeat the

inspections at intervals not to exceed 1,000 landings.

(ii) For the outboard struts on airplanes equipped with Rolls-

Royce RB211-524G or -524H series engines: Repeat the inspections at

intervals not to exceed 2,000 landings.

(2) If the corroded or cracked fuse pin is replaced with a 15-5

corrosion resistant steel (third generation) fuse pin, no further

action is required by this AD.

(e) Installation of 15-5 corrosion resistant steel (third

generation) fuse pins in the forward and aft positions of the upper

link on the inboard or outboard strut constitutes terminating action

for the requirements of this AD.

(f) 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 5: Information concerning the existence of approved

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

obtained from the Seattle ACO.

(g) 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 November 4, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-27852 Filed 11-9-94; 8:45 am]

BILLING CODE 4910-13-U