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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 99-NM-350-AD] 
          - RIN 2120-AA64 

# AGENCY:

Federal Aviation Administration, DOT. 

# ACTION:

Notice of proposed rulemaking (NPRM). 

# SUMMARY:

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Boeing Model 747-400, 757-200, 767-200, and 767-300 series airplanes. That AD currently requires repetitive checks to detect certain failures in the warning electronic unit (WEU) or modular avionic warning electronic assembly (MAWEA); repetitive tests to detect any failure of tactile, visual, or aural alerts generated by the WEU or MAWEA; and corrective action, if necessary. This action would make these requirements applicable to other airplanes on which the defective power supplies may be installed, eliminate the repetitive tests for certain airplanes, and increase the interval for the repetitive tests for certain other airplanes. This action also would require replacement of the existing power supplies in the WEU or MAWEA with modified, new, or serviceable power supplies. The actions specified by the proposed AD are intended to prevent failure of the WEU or MAWEA power supplies, which could result in loss of visual, aural, and tactile alerts to the flightcrew. Absence of such alerts could result in the flightcrew being unaware that an immediate or appropriate action should be taken in the event of an unsafe condition. 

# DATES:

Comments must be received by July 31, 2000. 

# ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-350-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:

Sheila I. Mariano, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2675; 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-350-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-350-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. 

## Discussion 

On August 24, 1999, the FAA issued AD 99-18-16, amendment 39-11282 (64 FR 47653, September 1, 1999), applicable to certain Boeing Model 747-400, 757-200, 767-200, and 767-300 series airplanes. That AD requires repetitive checks to detect certain failures in the warning electronic unit (WEU) or modular avionic warning electronic assembly (MAWEA); repetitive tests to detect any failure of tactile, visual, or aural alert generated by the WEU or MAWEA; and corrective action, if necessary. The AD also provides for optional terminating action for the repetitive checks and tests. That action was prompted by a report of a MAWEA power supply failure due to inadequate over-voltage protection. The requirements of that AD are intended to detect and correct such a failure, which could result in loss of visual, aural, and tactile alerts to the flightcrew. Absence of such alerts could result in the flightcrew being unaware that an immediate or appropriate action should be taken in the event of an unsafe condition. 

## Actions Since Issuance of Previous Rule 

                    In the preamble to AD 99-18-16, the FAA indicated that the actions required by that AD were considered “interim action” and that further rulemaking action was being considered to require the accomplishment of the optional terminating action specified in that AD. The FAA now has determined that further rulemaking action is indeed necessary, and this proposed AD follows from that determination. The optional terminating action described in AD 99-18-16 provides for replacement of the existing power supplies of the WEU or MAWEA with new power supplies having part number 285T0035-202 Mod A. However, since the issuance of that AD, the FAA has determined that several older power supplies are also acceptable replacements for the existing                           ( print page 37495)                        power supplies. Therefore, the proposed AD would provide for installation of certain other new or serviceable power supplies, in addition to the new power supply referenced for optional terminating action in AD 99-18-16.                 

Additionally, the FAA has determined that the defective power supplies that were the subject of AD 99-18-16 may have been installed as spares on airplanes that did not originally have the defective power supplies installed. Accordingly, the FAA finds it is necessary to expand the applicability of the existing AD to include any Boeing Model 747-400, 747-400F, 757-200, 757-200CB, 757-200PF, 767-200, 767-300, or 767-300F series airplane equipped with a WEU or MAWEA power supply having the affected part number, in order to prevent the identified unsafe condition on these airplanes. 

Also, since the issuance of AD 99-18-16, the FAA has determined that it is not necessary for the system functional tests required by paragraph (a) of that AD to be accomplished on Boeing Model 747-400 and -400F series airplanes. The FAA finds that the internal MAWEA system “byte check” on Model 747-400 and -400F series airplanes is sufficient to detect failures of the MAWEA either in the air or on the ground. Therefore, the requirement for system functional tests on Boeing Model 747-400 and -400F series airplanes has not been included in this AD. This AD continues to require checks of the engine indication and crew alerting system (EICAS) status page before each flight to detect MAWEA or WEU failure, as applicable, for all airplanes subject to this AD. 

## Explanation of Relevant Service Information 

The FAA has reviewed and approved Boeing Service Bulletin 747-31-2288, Revision 2, dated November 18, 1999, which describes procedures for replacement of the power supplies in the MAWEA of certain Boeing Model 747-400 and 747-400F series airplanes with modified, new, or serviceable power supplies. 

The FAA also has reviewed and approved Boeing Special Attention Service Bulletins 757-31-0066, Revision 2, and 767-31-0106, Revision 2, both dated November 18, 1999. These service bulletins describe procedures for replacing the power supplies in the WEU card file of Boeing Model 757-200, 757-200CB, 757-200PF, 767-200, 767-300, and 767-300F series airplanes with modified, new, or serviceable power supplies. 

Accomplishment of the actions specified in the service bulletins is intended to adequately address the identified unsafe condition. 

The service bulletins described previously refer to Boeing Component Service Bulletin 285T0035-31-07, dated December 17, 1998, as the appropriate source of service information for modification of WEU or MAWEA power supplies having P/N 28T0035-201. The modification of the power supplies involves replacing a printed circuit card and mounting screw, and changing the part number to 285T0035-202 Mod A. 

## 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 supersede AD 99-18-16 to continue to require repetitive checks to detect certain failures in the WEU or MAWEA and, for certain airplanes, repetitive tests to detect any failure of tactile, visual, or aural alerts generated by the WEU. This proposed AD would also continue to require corrective action, if necessary. This proposed AD would expand the applicability of the existing AD to include other airplanes on which the defective power supplies may be installed, increase the interval for the repetitive tests, and add a requirement for replacement of the existing power supplies in the WEU or MAWEA with modified, new, or serviceable power supplies. The actions would be required to be accomplished in accordance with the applicable service bulletin described previously. 

## Cost Impact 

There are approximately 1,592 airplanes of the affected design in the worldwide fleet. The FAA estimates that 802 airplanes of U.S. registry would be affected by this proposed AD. 

The repetitive checks and tests required by AD 99-18-16 are currently applicable to approximately 33 U.S.-registered airplanes. The repetitive checks and tests take approximately 1 work hour per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required checks and tests on U.S. operators is estimated to be $1,980, or $60 per airplane, per check/test cycle. Because this proposed AD would eliminate the currently required repetitive tests for certain airplanes, and increase the repetitive interval for the tests for certain other airplanes, the proposed AD would result in a reduction in costs to operators currently subject to AD 99-18-16. 

The repetitive checks and tests in this new proposed action would be applicable to approximately 769 additional airplanes. Based on the figures discussed above, the new costs to U.S. operators for the repetitive checks and tests that would be imposed by this proposed AD are estimated to be $46,140, or $60 per airplane, per check/test cycle. 

For all airplanes subject to this proposed AD, the new replacement that is proposed in this AD action would take approximately 3 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts would cost approximately $6,424 per airplane. Based on these figures, the cost impact of the replacement proposed by this AD action on U.S. operators is estimated to be $5,296,408, or $6,604 per airplane. 

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the current or 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 a substantial direct effect 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, it is determined that this proposal would not have federalism implications under Executive Order 13132. 

                    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                           ( print page 37496)                        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. 

§ 39.13 

2. Section 39.13 is amended by removing amendment 39-11282 (64 FR 47653, September 1, 1999), and by adding a new airworthiness directive (AD), to read as follows: 

**Boeing:**                                Docket 99-NM-350-AD. Supersedes AD 99-18-16, Amendment 39-11282.                             

*Applicability:*                                 Model 747-400, 747-400F, 757-200, 757-200CB, 757-200PF, 767-200, 767-300, and 767-300F series airplanes; equipped with either a warning electronics unit (WEU) or a modular avionics warning electronic assembly (MAWEA) power supply having part number (P/N) 285T0035-201; 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 request approval for an alternative method of compliance in accordance with paragraph (h)(1) 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 failure of the WEU or MAWEA power supplies, which could result in loss of visual, aural, and tactile alerts to the flightcrew (the absence of which could result in the flightcrew being unaware that an immediate or appropriate action should be taken in the event of an unsafe condition), accomplish the following: 

## Partial Restatement of Requirements of AD 99-18-16 

### Model 747-400 Series Airplanes: EICAS Status Page Checks 

(a) For Model 747-400 and 747-400F series airplanes having L/N 1121 through 1177 inclusive: Within 15 days after September 16, 1999 (the effective date of AD 99-18-16, amendment 39-11282), check the status page of the engine indication and crew alerting system (EICAS) for any MAWEA failure. Thereafter, repeat the EICAS status page check before each flight until the requirements of paragraph (c) or (f) of this AD have been accomplished. 

### Model 757-200, 767-200, and 767-300 Series Airplanes: Checks and Functional Tests 

(b) For Model 757-200, -200CB, and -200PF series airplanes having L/N 761 through 828 inclusive; and Model 767-200, -300, and -300F series airplanes having L/N 668 through 723 inclusive: Within 15 days after September 16, 1999, check the status page of the EICAS for any WEU failure; and perform the Work Instructions in Section 3, Part 1, of Boeing Service Bulletin 757-31-0066, Revision 1, dated December 17, 1998, or Revision 2, dated November 18, 1999 (for Model 757-200, -200CB, and -200PF series airplanes); or Boeing Service Bulletin 767-31-0106, Revision 1, dated December 17, 1998, or Revision 2, dated November 18, 1999 (for Model 767-200, 767-300, and 767-300F series airplanes); as applicable; to detect loss of any visual, aural, or tactile alert. Thereafter, repeat the EICAS status page check before each flight, and the Work Instructions in Section 3, Part 1, of the applicable service bulletin at intervals not to exceed every “A” check or 45 days, whichever occurs first, until the requirements of paragraph (c) or (f) of this AD has been accomplished. After the effective date of this AD, only Revision 2 of the applicable service bulletin shall be used. 

### Corrective Action 

(c) If any failure of the MAWEA or WEU, as applicable, or the loss of any visual, aural, or tactile alert is detected during any test required by either paragraph (a) or (b) of this AD, prior to further flight, accomplish paragraph (c)(1), (c)(2), or (c)(3) of this AD; as applicable. 

(1) For Model 747-400 or -400F series airplanes: Replace the power supplies of the MAWEA with new or modified power supplies having P/N 285T0035-202 Mod A, in accordance with either Boeing Service Bulletin 747-31-2288, dated December 17, 1998, or Revision 1, dated January 28, 1999; or with new, modified, or serviceable power supplies having P/N 285T0035-202 Mod A, P/N 285T0035-10, or P/N 285T0035-11; in accordance with Boeing Service Bulletin 747-31-2288, Revision 2, dated November 18, 1999. Such replacement constitutes terminating action for the requirements of this AD. After the effective date of this AD, only Revision 2 of the applicable service bulletin shall be used. 

(2) For Model 757-200, -200CB, and -200PF series airplanes: Replace the power supplies of the WEU with new or modified power supplies having P/N 285T0035-202 Mod A, in accordance with Boeing Service Bulletin 757-31-0066, Revision 1, dated December 17, 1998; or with new, modified, or serviceable power supplies having P/N 285T0035-202 Mod A, P/N 285T0035-9, P/N 285T0035-10, or P/N 285T0035-11, in accordance with Boeing Special Attention Service Bulletin 757-31-0066, Revision 2, dated November 18, 1999. Such replacement constitutes terminating action for the requirements of this AD. After the effective date of this AD, only Revision 2 of the service bulletin shall be used. 

(3) For Model 767-200, -300, and -300F series airplanes: Replace the power supplies of the WEU with new or modified power supplies having P/N 285T0035-202 Mod A, in accordance with Boeing Service Bulletin 767-31-0106, Revision 1, dated December 17, 1998; or with new, modified, or serviceable power supplies having P/N 285T0035-202 Mod A, P/N 285T0035-9, P/N 285T0035-10, or P/N 285T0035-11; in accordance with Boeing Special Attention Service Bulletin 767-31-0106, Revision 2, dated November 18, 1999. Such replacement constitutes terminating action for the requirements of this AD. After the effective date of this AD, only Revision 2 of the applicable service bulletin shall be used. 

# Note 2:

Page 59 of Boeing Service Bulletin 747-31-2288, Revision 1, dated January 28, 1999, incorrectly references the Boeing 767 AMM as the appropriate source of service information for accomplishment of the removal and installation of the power supply. However, the correct reference is the Boeing 747 AMM. 

## New Requirements of This AD 

# Note 3:

Boeing Component Service Bulletin 285T0035-31-07, dated December 17, 1998, describes procedures for modifying WEU or MAWEA power supplies having P/N 28T0035-201 to 285T0035-202 Mod A. 

### Repetitive Checks: Model 747-400 and -400F 

(d) For Model 747-400 and -400F series airplanes other than those identified in paragraph (a) of this AD: At the next “A” check or within 45 days, whichever occurs first, check the status page of the EICAS for any MAWEA failure. 

(1) If no MAWEA failure is detected: Thereafter, repeat the EICAS status page check before each flight, until the requirements of paragraph (e) are accomplished. 

(2) If any MAWEA failure is detected: Prior to further flight, replace MAWEA power supplies having P/N 285T0035-201 with new or modified power supplies having P/N 285T0035-202 Mod A, or new or serviceable power supplies having P/N 285T0035-10 or P/N 285T0035-11; in accordance with Boeing Service Bulletin 747-31-2288, Revision 2, dated November 18, 1999. Such replacement constitutes terminating action for the requirements of this AD. 

### Repetitive Checks and Functional Tests: Model 757 and 767 

(e) For Model 757-200, 757-200CB, 757-200PF, 767-200, 767-300, and 767-300F series airplanes other than those identified in paragraph (b) of this AD: At the next “A” check or within 45 days, whichever occurs first, check the status page of the EICAS for any WEU failure; and perform the Work Instructions in Section 3, Part 1, of Boeing Special Attention Service Bulletin 757-31-0066, Revision 2, dated November 18, 1999; or Boeing Special Attention Service Bulletin 767-31-0106, Revision 2, dated November 18, 1999; as applicable; to detect loss of any visual, aural, or tactile alert. 

                                (1) If no failure of the WEU or loss of any visual, aural, or tactile alert is detected: Thereafter, repeat the EICAS status page check before each flight, and accomplish the Work Instructions in Section 3, Part 1 of the applicable service bulletin at intervals not to exceed every “A” check or 45 days, whichever occurs first, until the requirements of paragraph (e) are accomplished.                                       ( print page 37497)    

(2) If any failure of the WEU or loss of any visual, aural, or tactile alert is detected: Prior to further flight, replace WEU power supplies having P/N 285T0035-201, with new or modified power supplies having P/N 285T0035-202 Mod A; or new or serviceable power supplies having P/N 285T0035-9, P/N 285T0035-10, or P/N 285T0035-11; in accordance with the applicable service bulletin. Such replacement constitutes terminating action for the requirements of this AD. 

### Replacement 

(f) Within 1 year after the effective date of this AD, replace WEU or MAWEA power supplies having P/N 285T0035-201, with new or modified power supplies having P/N 285T0035-202 Mod A; or new or serviceable power supplies having P/N 285T0035-9, P/N 285T0035-10, or P/N 285T0035-11; in accordance with Boeing Service Bulletin 747-31-2288, dated December 17, 1998, Revision 1, dated January 28, 1999, or Revision 2, dated November 18, 1999 (for Model 747-400 and 747-400F series airplanes); Boeing Service Bulletin 757-31-0066, Revision 1, dated December 17, 1998, or Revision 2, dated November 18, 1999 (for Model 757-200, 757-200CB, and 757-200PF series airplanes); or Boeing Service Bulletin 767-31-0106, Revision 1, dated December 17, 1998, or Revision 2, dated November 18, 1999 (for Model 767-200, 767-300, and 767-300F series airplanes); as applicable. After the effective date of this AD, only Revision 2 of the applicable service bulletin shall be used. Such replacement constitutes terminating action for the repetitive inspection requirements of this AD. 

### Spares 

(g) As of the date specified in paragraph (g)(1) or (g)(2), as applicable, no person shall install a WEU or MAWEA power supply having Boeing P/N 285T0035-201 on any airplane. 

(1) For Model 747-400 series airplanes, line numbers 1121 through 1177 inclusive; Model 757-200, -200CB, and -200PF series airplanes, line numbers 761 through 828 inclusive; and Model 767-200, 767-300, and -300F series airplanes, line numbers 668 through 723 inclusive: As of September 16, 1999 (the effective date of AD 99-18-16, amendment 39-11282). 

(2) For airplanes other than those identified in paragraph (g)(1) of this AD: As of the effective date of this AD. 

### Alternative Methods of Compliance 

(h)(1) 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 Avionics Inspector, who may add comments and then send it to the Manager, Seattle ACO. 

(2) Alternative methods of compliance, approved previously by the FAA in accordance with AD 99-18-16, amendment 39-11282, are approved as alternative methods of compliance with this AD. 

# Note 4:

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 

(i) 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 June 9, 2000. 

Donald L. Riggin, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 00-15189 Filed 6-14-00; 8:45 am] 

BILLING CODE 4910-13-U