Airworthiness Directives; Boeing Model 747-100, -200, 747SP, and 747SR Series; Airplanes Equipped With Pratt & Whitney JT9D-7, -7A, -7F, and -7J Series Engines

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-242-AD]

RIN 2120-AA64

Airworthiness Directives; Boeing Model 747-100, -200, 747SP, and

747SR Series; Airplanes Equipped With Pratt & Whitney JT9D-7, -7A, -7F,

and -7J 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 747-100, -

200, 747SP, and 747SR series airplanes. This proposal would require

one-time detailed visual and eddy current inspections to detect

cracking of the nose cowl mounting flange; rework of the nose cowl

mounting flange; eddy current inspection to detect cracking of the

reworked nose cowl mounting flange; and corrective action, if

necessary. This proposal is prompted by reports of the nose cowl

separating from the engine and departing the airplane following severe

engine vibration. The actions specified by the proposed AD are intended

to prevent separation of the nose cowl from the engine, which could

cause collateral damage to the airplane, and, possibly, reduced

controllability of the airplane.

DATES: Comments must be received by November 22, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Transport Airplane Directorate, ANM-114,

Attention: Rules Docket No. 99-NM-242-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: Dionne Stanley, Aerospace Engineer,

Propulsion Branch, ANM-140S, FAA,

[[Page 54241]]

Transport Airplane Directorate, Seattle Aircraft Certification Office,

1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425)

227-2250; fax (425) 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 99-NM-242-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-114, Attention: Rules

Docket No. 99-NM-242-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

The FAA has received reports indicating that, on certain Boeing

Model 747 series airplanes equipped with certain Pratt & Whitney JT9D

series engines, the nose cowl has separated from the engine and

departed the airplane following severe engine vibration.

The severe engine vibration was caused by engine damage resulting

from bird or foreign object ingestion. Separation of the nose cowl from

the engine, if not corrected, could cause collateral damage to the

airplane, and, possibly, reduced controllability of the airplane.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Service Bulletin 747-71-

2290, dated March 18, 1999, which describes procedures for one-time

detailed visual and eddy current inspections to detect cracking of the

existing nose cowl mounting flange; rework of the nose cowl mounting

flange to increase the number of attachment fastener holes from 37 to

67; and a one-time eddy current inspection to detect cracking of the

new fastener holes in the reworked nose cowl mounting flange.

Accomplishment of the actions specified in the service bulletin is

intended to adequately address the identified unsafe condition.

Explanation of Requirements of Proposed Rule

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 accomplishment of the actions specified in

the service bulletin described previously, except as discussed below.

If any cracking is found during any inspection, corrective actions

would be required to be accomplished in accordance with a method

approved by the FAA.

Differences Between Proposed Rule and Service Bulletin

Operators should note that the service bulletin does not recommend

any compliance time for accomplishing the nose cowl inspections and

rework. In developing an appropriate compliance time for this AD, the

FAA considered the degree of urgency associated with addressing the

subject unsafe condition, the average utilization of the affected

fleet, and the time necessary to perform the inspections and rework. In

light of all of these factors, the FAA finds a 24-month compliance time

for initiating the required actions to be warranted, in that it

represents an appropriate interval of time allowable for affected

airplanes to continue to operate without compromising safety.

Cost Impact

There are approximately 257 airplanes of the affected design in the

worldwide fleet. The FAA estimates that 106 airplanes of U.S. registry

would be affected by this proposed AD, that it would take approximately

19 work hours per airplane to accomplish the proposed actions, and that

the average labor rate is $60 per work hour. Required parts would cost

approximately $500 per airplane. Based on these figures, the cost

impact of the proposed AD on U.S. operators is estimated to be

$173,840, or $1,640 per airplane.

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.

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.

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. 106(g), 40113, 44701.

[[Page 54242]]

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

Boeing: Docket 99-NM-242-AD.

Applicability: Model 747-100, -200, 747SP, and 747SR series

airplanes; certificated in any category; equipped with Pratt &

Whitney JT9D-7, -7A, -7F and -7J series engines.

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 request approval for an

alternative method of compliance in accordance with paragraph (d) of

this AD. The request should include an assessment of the effect of

the modification, alteration, or repair on the unsafe condition

addressed by this AD; and, if the unsafe condition has not been

eliminated, the request should include specific proposed actions to

address it.

Compliance: Required as indicated, unless accomplished

previously.

To prevent separation of the nose cowl from the engine, which

could cause collateral damage to the airplane, and, possibly,

reduced controllability of the airplane, accomplish the following:

One-Time Inspections and Rework

(a) Within 24 months after the effective date of this AD,

perform one-time detailed visual and eddy current inspections to

detect cracking of the existing nose cowl mounting flange, rework

the nose cowl mounting flange to increase the number of attachment

fastener holes from 37 to 67, and perform a one-time eddy current

inspection to detect cracking of the new fastener holes in the

reworked nose cowl mounting flange, in accordance with the

Accomplishment Instructions of Boeing Service Bulletin 747-71-2290,

dated March 18, 1999.

Note 2: For the purposes of this AD, a detailed visual

inspection is defined as ``An intensive visual examination of a

specific structural area, system, installation, or assembly to

detect damage, failure, or irregularity. Available lighting is

normally supplemented with a direct source of good lighting at

intensity deemed appropriate by the inspector. Inspection aids such

as mirror, magnifying lenses, etc., may be used. Surface cleaning

and elaborate access procedures may be required.''

Corrective Action

(b) If any crack is found during any inspection required by

paragraph (a) of this AD: Prior to further flight, repair in

accordance with a method approved by the Manager, Seattle Aircraft

Certification Office (ACO), FAA, Transport Airplane Directorate.

(c) As of the effective date of this AD, no person shall install

a nose cowl on any airplane, unless it has been inspected and

modified in accordance with paragraph (a) of this AD.

Alternative Methods of Compliance

(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 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 3: Information concerning the existence of approved

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

obtained from the Seattle ACO.

Special Flight Permits

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

Secs. 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 September 30, 1999.

D.L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 99-26085 Filed 10-5-99; 8:45 am]

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