Airworthiness Directives; Boeing Model 767 Series Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 93-NM-228-AD]

Airworthiness Directives; Boeing Model 767 Series Airplanes

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 767 series

airplanes. This proposal would require dye penetrant inspection and

proof pressure testing to detect cracks or ruptures of the crossover

pneumatic duct, and repair or replacement, as necessary. This proposal

would also require stress relieving of the crossover pneumatic duct

assembly. This proposal is prompted by several reports of ruptured

engine bleed air crossover ducts. The actions specified by the proposed

AD are intended to prevent failure of the engine bleed air crossover

duct, which could result in loss of pneumatics and damage to adjacent

structure.

DATES: Comments must be received by April 11, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 93-NM-228-AD, 1601 Lind Avenue, SW.,

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

location between 9 a.m. and 3 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: Barbara Mudrovich, Aerospace Engineer,

Systems and Equipment Branch, ANM-130S; Seattle Aircraft Certification

Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone

(206) 227-2670; 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 93-NM-228-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. 93-NM-228-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

On July 14, 1993, the FAA issued AD 93-14-11, Amendment 39-8635 (58

FR 43550, August 17, 1993), applicable to Boeing Model 767 series

airplanes, line position 001 through 307, inclusive. That AD requires a

dye penetrant inspection and proof pressure testing to detect cracks or

ruptures of the crossover pneumatic ducts, and repair or replacement,

as necessary. That action was prompted by several reported incidents of

ruptured engine bleed air crossover ducts on certain Boeing Model 767

series airplanes. The duct ruptures resulted in a loss of cabin

pressure, loss of bleed air to the air driven hydraulic pump, loss of

wing thermal anti-ice capabilities, and damage to the air conditioning

panels. These duct ruptures were caused by cracking, which started and

progressed around the circumferential welds. These cracks formed in the

heat affected zones of the duct welds because of hydrogen oxide

(hydride) concentration. The hydrides have an embrittling effect on the

duct material, which may initiate the cracking.

Duct ruptures, if not corrected, could result in loss of pneumatics

for cabin pressurization, air conditioning, air driven hydraulic pump,

wing thermal anti-ice, hydraulic reservoir pressurization, engine cross

starting ability, and cargo heating, and could also damage air

conditioning panels.

Since the issuance of AD 93-14-11, the manufacturer has discovered

that stress relieving of one of the four crossover ducts was

incorporated during production on airplanes starting at line number 322

instead of line number 308. The manufacturer has informed the FAA that

14 airplanes did not receive stress relieving of the crossover duct.

Therefore, these 14 airplanes would be subject to the same unsafe

condition as addressed by AD 93-14-11.

The FAA has reviewed and approved Boeing Service Bulletin 767-

36A0041, Revision 2, dated October 28, 1993, that describes procedures

for conducting dye penetrant inspections and proof pressure tests of

the crossover pneumatic duct. This service bulletin also describes

procedures for repairing or replacing this duct, and stress relieving

this duct. Stress relieving this duct will eliminate the residual

stress and local stress concentration. A dye penetrant inspection,

proof pressure test, and stress relieving will reduce the possibility

of engine bleed air crossover duct rupture caused by cracking due to

hydride formation. The effectivity listing of this service bulletin

includes the 14 airplanes on which the stress relieving procedure was

not accomplished during production.

Since an unsafe condition has been identified that is likely to

exist on other products of this same type design, the proposed AD would

require conducting dye penetrant inspections and proof pressure tests

of the crossover pneumatic duct on 14 specific airplanes. This proposed

AD would also require repairing or replacing this duct, and stress

relieving this duct. The actions would be required to be accomplished

in accordance with the service bulletin described previously.

(Note: The FAA's normal policy is that, when an AD requires a

substantive change, such as a change in its applicability, the

``old'' AD is superseded by being removed from the system and a new

AD added. In the case of this AD action, the FAA normally would have

proposed superseding AD 93-14-11 to expand its applicability to

include the 14 additional airplanes. However, in reconsideration of

the entire fleet size that would be affected by such a supersedure

action, and the consequent workload associated with revising

maintenance record entries, the FAA has determined that a less

burdensome approach is to issue a separate AD applicable only to the

14 airplanes. This AD does not supersede AD 93-14-11; airplanes

listed in the applicability of AD 93-14-11 continue to be required

to comply with the requirements of that AD. This proposed AD is a

separate AD action, and is applicable only to airplanes having line

numbers 308 through 321, inclusive.)

There are 14 Model 767 series airplanes of the affected design in

the worldwide fleet. The FAA estimates that 6 airplanes of U.S.

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

approximately 18 work hours per airplane to accomplish the proposed

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

parts would cost approximately $2,208 per airplane. Based on these

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

estimated to be $19,188, or $3,198 per airplane. This total cost figure

assumes that no operator has yet accomplished the proposed requirements

of this AD action.

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 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:

Boeing: Docket 93-NM-228-AD.

-Applicability: Model 767 series airplanes, line position 308

through 321 inclusive, certificated in any category. -

Compliance: Required as indicated, unless accomplished

previously.

-Note 1: Inspections, testing, and repair or replacement

accomplished prior to the effective date of this amendment in

accordance with Boeing Alert Service Bulletin 767-36A0041, dated

July 2, 1992; or Revision 1, dated February 25, 1993; are considered

acceptable for compliance with the applicable action specified in

this amendment. -

To prevent failure of the engine bleed air crossover duct, which

could result in loss of pneumatics and damage to adjacent structure,

accomplish the following: -

(a) OPTION 1: As an alternative to the requirements of paragraph

(b) of this AD, accomplish the following: -

(1) Within 6 months after the effective date of this AD, or

prior to the accumulation of 7,000 total flight cycles, whichever

occurs later, conduct a dye penetrant inspection and proof pressure

test of the crossover pneumatic duct, in accordance with Boeing

Service Bulletin 767-36A0041, Revision 2, dated October 28, 1993. -

(i) If cracks or ruptures are detected, prior to further flight,

repair or replace the crossover pneumatic duct in accordance with

the service bulletin. -

(ii) Stress relieving of the duct, in accordance with the

service bulletin, may be accomplished in conjunction with the

initial dye penetrant inspection and proof pressure test required by

this paragraph. Such action constitutes terminating action for the

requirements of paragraph (a)(2) of this AD. -

(2) Within 3,000 flight cycles after accomplishing the initial

dye penetrant inspection and proof pressure test required by

paragraph (a)(1) of this AD, conduct an additional dye penetrant

inspection and proof pressure test of the crossover pneumatic duct,

and stress relieve the crossover pneumatic duct assembly, in

accordance with Boeing Service Bulletin 767-36A0041, Revision 2,

dated October 28, 1993. If cracks or ruptures are detected, prior to

further flight, repair or replace the crossover pneumatic duct in

accordance with the service bulletin. -

(b) OPTION 2: As an alternative to the requirements of paragraph

(a) of this AD, accomplish the following: -

(1) Within 18 months after the effective date of this AD, or

prior to the accumulation of 7,000 total flight cycles, whichever

occurs later, conduct a dye penetrant inspection and proof pressure

test of the crossover pneumatic duct and stress relieve the

crossover pneumatic duct assembly, in accordance with Boeing Service

Bulletin 767-36A0041, Revision 2, dated October 28, 1993. -

(2) If cracks or ruptures are detected, prior to further flight,

repair or replace the crossover pneumatic duct in accordance with

the service bulletin. -

(c) Replacement of the crossover pneumatic duct with a stress

relieved duct in accordance with Boeing Service Bulletin 767-

36A0041, Revision 2, dated October 28, 1993, constitutes terminating

action for the requirements of paragraphs (a) and (b) of this AD.

(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 FAR

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 February 9, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-3460 Filed 2-14-94; 8:45 am]

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