Airworthiness Directives; Boeing Model 767 Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Final rule.

SUMMARY:

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 767 series airplanes, that requires a one-time detailed visual inspection to detect discrepancies of the wire expando sleeve of the wire bundles adjacent to the landing gear control lever module; certain follow-on actions and repair, if necessary; and wrapping the wire expando sleeve with tape, or with zippertubing and tape. This amendment is prompted by reports indicating that the landing gear failed to extend on an in-service airplane, and that the landing gear control cable was severed on a second in-service airplane. The actions specified by this AD are intended to prevent interference between the landing gear control lever and wire bundles adjacent to the landing gear control lever module, and to prevent wire chafing and arcing between the landing gear control cable and adjacent wire bundles, which could result in the inability to extend the landing gear prior to landing.

DATES:

Effective March 28, 2000.

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of March 28, 2000.

ADDRESSES:

The service information referenced in this AD 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; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT:

Elias Natsiopoulos, 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) 227-1279; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION:

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing Model 767 series airplanes was published in the Federal Register on February 17, 1999 (64 FR 7829). That action proposed to require a one-time inspection to detect discrepancies of the wire expando sleeve of the wire bundles adjacent to the landing gear control lever module; certain follow-on actions and repair, if necessary; and wrapping the wire expando sleeve with tape, or with zippertubing and tape.

Comments

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

Support for the Proposal

Two commenters concur with the proposal. Another commenter states that it is not affected by the proposal, as the proposed actions have been accomplished for its fleet.

Request to Clarify Wire Bundle Interference

One commenter, the manufacturer, recommends clarification of the description of wire bundle interference in the Summary and Discussion sections of the proposed rule. The notice of proposed rulemaking (NPRM) describes two incidents on in-service Model 767 series airplanes. In the first incident, the expando sleeve on a wire bundle adjacent to the landing gear lever mechanism in the flight deck became caught on the lever mechanism such that the lever could not be moved from the UP position, and the gear was extended by depressurizing the center hydraulic system. The commenter contends that interference of the wire bundle expando sleeve with the landing gear control lever did not result in the wires for the alternate extension system interfering and arcing with the landing gear UP cable. Such interference and arcing are unrelated events. The contact with the gear UP cable was solely the result of the amount of slack in the wire bundle itself. The only wire bundle long enough to reach the gear UP cable is the one that contains wires for the alternate extension system.

In the second incident, which was an unrelated incident, a wire bundle containing wires for the alternate extension system chafed on the landing gear UP cable, causing arcing and failure of the gear UP cable; however, the landing gear was extended at the time and gear extension capability was still available through the gear DOWN cable. The commenter contends that the inability to extend the landing gear also is not an issue if the landing gear had been UP and locked; the landing gear will extend. If the landing gear had been retracted when the UP cable was severed, and assuming that the alternate extension system had been rendered inoperative due to the arcing, the normal extension system is available. When gear DOWN is selected, the landing gear selector valve will move to the gear DOWN position through the landing gear lever and the DOWN cable, and the landing gear will extend. In addition, because the DOWN cable is located forward of the UP cable and the wire bundle, the landing gear DOWN cable is not susceptible to the same arcing and severing as the UP cable.

For the Summary section of the NPRM, the commenter suggests clarifying that only one report prompted the NPRM, the landing gear “UP cable” was severed, and that “consequent arcing” was not a factor in the interference between the landing gear control lever and the wire bundles. In addition, the commenter suggests adding that the proposed AD also is intended to prevent chafing and arcing between the wire bundle containing wires for the landing gear alternate extension system and the landing gear UP cable.

The FAA concurs partially with the commenter's recommended changes to the Summary section of the NPRM and has determined that certain changes add technical clarity. However, more than one report was received regarding the unsafe condition; therefore, no change to the final rule is necessary in that regard.

Although the Summary does not specify which cable (UP or DOWN) was severed, the FAA points out that one of the reports of an in-service incident on a Model 767 series airplane does not specify which cable was severed, or the condition of the other cable. In one incident, the FAA concluded that it was the UP cable that was damaged because the flight crew could not retract the landing gear. However, it is not the severance of the UP cable that could result in the inability to extend the landing gear, but the loss of the alternate extend system due to the damaged wires (an undetectable failure) and the inability to move the control lever from the UP to the DOWN position, or the loss of the center hydraulic system. In light of this, the final rule has not been changed to specify which cable was severed.

The FAA has clarified that the action required by the proposed AD is intended to prevent “interference” between the landing gear control lever module and adjacent wire bundles rather than to prevent “interference and consequent arcing.” However, the FAA has determined that this AD also is intended to “prevent wire chafing and arcing between the landing gear control cable and adjacent wire bundles” rather than “to prevent chafing and arcing between the wire bundle containing wires for the landing gear alternate extension system and the landing gear UP cable.”

For the Discussion section of the NPRM, the commenter suggests further clarification of what the investigation revealed, and the damage caused by interference between the landing gear and wire bundles. The commenter contends that the landing gear still would extend when the landing gear lever is moved to the DOWN position because the DOWN cable would not be affected.

Although the FAA agrees with some of the commenter's suggested changes to the Discussion section of the proposed AD, no changes are necessary because that section is not included in the final rule. However, as stated earlier in this AD, the inability to extend the landing gear is not due to the severance of the UP cable but to a number of other factors.

The FAA also agrees that the wire bundle that contains the wires of the landing gear alternate extension system interfered with the landing gear cable, and that this interference caused the wires of the alternate extension system to arc. In addition, the FAA agrees that repeated arcing over a period of time could sever the landing gear cable; however, as stated earlier, it is not necessary to specify the “UP” cable. Further, the FAA agrees that the landing gear will extend when the landing gear lever is moved to the DOWN position if the landing gear DOWN cable is unaffected.

Request To Clarify the Wire Bundle Wrapping Procedure

The Air Transport Association (ATA) of America, on behalf of one of its members, states that this member requests clarification with regard to the procedure for wrapping the wire bundles. According to the commenter, the proposed rule gives the option to perform the work in accordance with Boeing Alert Service Bulletin 767-32A0163, original issue, dated March 5, 1998, or Boeing Service Bulletin 767-32A0163, Revision 1, dated October 1, 1998. However, the proposed rule requires wrapping the wire bundles with “tape,” or with “zippertubing and tape,” and does not include the option to wrap the wire bundle with “zippertubing” only, as permitted in the original issue of the service bulletin. (Both versions of the service bulletin are cited in the proposal as appropriate sources of service information.) For this reason, the commenter contends that this inconsistency could lead to confusion and should be clarified.

The FAA acknowledges that clarification of the wrapping procedure is necessary. Although the original issue of the alert service bulletin specifies using either “tape” or “zippertubing,” and the Summary of Revision 1 of the service bulletin specifies using either “tape” or “zippertubing,” the FAA points out that the Accomplishment Instructions of Revision 1 of the service bulletin specify using either “tape” or “zippertubing and tape.”

Although the original issue of the alert service bulletin specifies wrapping the wire bundles together in a single grouping, Revision 1 of the service bulletin specifies separating the wire bundles into two separate groups (one group consisting of a small single wire bundle, and the other group consisting of the remaining wire bundles that are larger in trunk diameter). Revision 1 of the service bulletin was issued after reports indicated that, due to limited access, it was difficult to wrap all of the wire bundles together in the P31 panel, and that grouping the wire bundles in a single wrap resulted in a stiff, unmanageable assembly. The FAA was informed by the manufacturer that zippertubing small enough for wrapping a single wire bundle is unavailable, and using a larger size of zippertubing is not recommended. For that reason, Revision 1 of the service bulletin includes the preferred procedures for separating the wire bundles into two groups for wrapping and provides an easier method for accomplishing those actions than the original issue of the alert service bulletin. [The FAA has added Note 3 following paragraph (a) of this AD to specify this information.] The FAA has determined that if operators have accomplished the action required to wrap the expando sleeve with either “tape” or “zippertubing only” in accordance with the original issue of the alert service bulletin, that action is adequate in addressing the identified unsafe condition. References to the type of wrapping required have been removed from paragraph (a)(1), (a)(2)(i), (a)(2)(ii)(A), or (a)(2)(ii)(B) of the final rule.

Request To Extend the Compliance Time and Change Inspection Requirements

The ATA, on behalf of one of its members, requests that the proposed compliance threshold for the initial inspection be extended to 1 year after the effective date of the AD, so that the required inspections can be conducted in a controlled hangar environment. According to the commenter, with a fleet of 79 Model 767 series airplanes affected by this proposed rule, the 90-day compliance time would pose a significant operational burden; whereas, an extension of the compliance time to 1 year would allow sufficient flexibility to perform the inspection at the next scheduled maintenance.

The FAA does not concur with the request to extend the compliance time. In developing an appropriate compliance time for this action, the FAA considered not only the safety implications but the normal maintenance schedules for timely accomplishment of the required inspection and corrective actions. In consideration of these items and reports of the identified unsafe condition, the FAA has determined that a 90-day compliance time represents an appropriate interval of time allowable wherein the corrective actions can be accomplished during scheduled maintenance intervals for the majority of affected operators, and an adequate level of safety can be maintained. The FAA points out this AD does not require that inspections be performed in a controlled hangar environment. In addition, other operators with large fleets of Model 767 series airplanes have already complied with those requirements. No change to paragraph (a) of the final rule is necessary in this regard.

Request for an Additional Modification of the Landing Gear

One commenter states that the accomplishment of an additional modification of the control lever module, in accordance with Boeing Service Bulletin 757-32-0179, dated December 22, 1998, is necessary to provide a newly designed left-side plate of the landing gear control lever module. Although the actions required by the proposed AD are intended to detect and prevent possible interference between the wire bundle and landing gear control lever module, such action does not completely remove the possibility that such interference could occur in the specific area of the landing gear control lever module behind the instrument panel. Such a modification would effectively prevent interference between the wire bundle and the control lever module and also prevent a subsequent “blocked” lever.

The FAA does not concur that the final rule should include a requirement for installing a newly designed left-side plate of the landing gear control lever module in accordance with Service Bulletin 767-32-0179. Accomplishment of the actions specified by either the original issue or Revision 1 of Service Bulletin 767-32A0163 is intended to adequately address the identified unsafe condition by preventing interference between the landing gear control lever and wire bundles adjacent to the landing gear control lever module and by preventing wire chafing and arcing between the landing gear control cable and adjacent wire bundles. The FAA points out that, although the new left-side plate specified by Service Bulletin 767-32-0179 provides a barrier between the wire bundles and landing gear control lever module, such a plate does not protect the wires from chafing.

Request for Issuance of an Interim Flight Crew Procedure

One commenter states that it considers issuance of a flight crew operating procedure by an operational bulletin to be essential in providing instructions on how to shut down the center hydraulic system for Model 767 series airplanes and subsequently extend the landing gear. The commenter contends that this procedure is necessary until a hydraulic bypass valve is installed (as described in the following paragraphs).

Although the FAA acknowledges the concerns of the commenter regarding issuance of a flight crew operating procedure for shutting down the center hydraulic system, it does not concur that this AD should include such a procedure. The FAA has determined that, because of the complexity of the hydraulic system, issuance of such an operating procedure could introduce other unforeseeable problems. At the present time, shutting down the center hydraulic system is only used in an emergency situation, and such a decision is determined by the flight crew. The FAA considers that such a provision is adequate in addressing the identified unsafe condition and ensuring the continued safety of the affected fleet. No change to this final rule is necessary in this regard.

Request To Install a Hydraulic Bypass Valve for the Landing Gear

One commenter recommends installing a hydraulic bypass valve in the landing gear hydraulic system on Model 767 series airplanes. Because of an incident that occurred in the 1980's on a Model 757 series airplane in which the flight crew was unable to extend the landing gear when a blocked system occurred while the landing gear was in the UP position, the manufacturer issued Boeing Service Bulletin 757-32-0053, which specifies installation of a hydraulic bypass valve. Such a valve bypasses the hydraulic pressure from the UP position when using the alternate gear extension system, and allows the gear to be extended with the extension system, even with the gear UP pressure still applied when the extension system is blocked in its UP position. The hydraulic bypass valve, specified by Service Bulletin 757-32-0053 and installed in Model 757 series airplanes in accordance with that service bulletin, also is available for Model 767 series airplanes as a masterchange for retrofit, and has been installed on one operator's fleet of Model 767 series airplanes.

However, the commenter contends that accomplishment of the actions specified by Service Bulletin 767-32-0179 and those specified by the original issue and Revision 1 of Service Bulletin 767-32A0163 would only prevent an incident in which the flight crew would be unable to extend the landing gear if the cause is related to the landing gear control lever module or its adjacent wire bundles. The flight crew would still be unable to extend the landing gear when a blocked system in the UP position is caused by a different component of the landing gear extension system. That this possibility exists is indicated by the fact that this condition occurred on Model 757 series airplanes in the 1980's (as described previously).

The commenter also states that one operator of a Model 767 series airplane experienced an inflight event when the landing gear lever failed to move from the UP to the OFF position. Following this event, extensive troubleshooting revealed the anomaly of the wire bundle and the associated landing gear lever module, as described in the proposed rule. Based on those findings and the immediate action taken to prevent such an incident in the future, the commenter has investigated and reviewed the entire design of the landing gear extension system, and has concluded that a design deficiency exists in the Model 767 landing gear extension system.

The FAA acknowledges the concerns of the commenter, and may consider additional rulemaking to address that concern in the future on certain airplanes. However, while there may be merit to the commenter's suggestion regarding installation of a hydraulic bypass valve, this AD is not the appropriate context in which to evaluate that suggestion. The FAA finds that to delay this action would be inappropriate in light of the identified unsafe condition. In addition, at the present time, the FAA has not determined all of the failure modes of the hydraulic bypass valve and the effects of such failures on the landing gear hydraulic system for Model 767 series airplanes. Therefore, no change to the final rule is deemed necessary.

Request To Add a Phrase to the Proposed AD

One commenter states that it has reviewed the proposed NPRM and, having already commenced embodiment of Boeing Service Bulletin 767-32A0163, would like to see the words “unless previously accomplished” inserted before paragraph (a) of the proposed NPRM.

The FAA points out that operators are always given credit for work accomplished previously, and that the compliance statement of an AD includes the phrase “Required as indicated, unless accomplished previously.” Therefore, no change to the final rule is necessary.

Explanation of Changes Made to the Proposal

The FAA has clarified the inspection requirements by specifying a “detailed visual inspection” rather than an “inspection,” which was cited in the Summary of the NPRM, or a “visual inspection,” which was cited in paragraphs (a), (a)(2), and (a)(2)(ii) of the proposed AD. In addition, in the final rule Note 2 has been added to clarify the definition of a detailed visual inspection. The final rule has been changed accordingly.

Conclusion

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

Cost Impact

There are approximately 666 Model 767 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 268 airplanes of U.S. registry will be affected by this AD, that it will take approximately 1 work hour per airplane to accomplish the required actions, and that the average labor rate is $60 per work hour. The cost of required parts are nominal. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $16,080, or $60 per airplane.

The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the 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 adopted herein will 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 final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (1) is not a “significant regulatory action” under Executive Order 12866; (2) is not a “significant rule” under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption “ADDRESSES.”

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Incorporation by reference
• Safety

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 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.

2. Section 39.13 is amended by adding the following new airworthiness directive:

2000-03-21 Boeing: Amendment 39-11581. Docket 98-NM-193-AD.

Applicability: Model 767 airplanes, as listed in Boeing Service Bulletin 767-32A0163, Revision 1, dated October 1, 1998; 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 (b) 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 interference between the landing gear control lever and wire bundles adjacent to the landing gear control lever module, and to prevent wire chafing and arcing between the landing gear control cable and adjacent wire bundles, which could result in the inability to extend the landing gear prior to landing, accomplish the following:

Detailed Visual Inspection

(a) Within 90 days after the effective date of this AD, perform a one-time detailed visual inspection to detect discrepancies (i.e., cut, abrasion, fraying, and arcing) of the wire expando sleeve of the wire bundles adjacent to the landing gear control lever module, in accordance with Boeing Alert Service Bulletin 767-32A0163, dated March 5, 1998, or Boeing Service Bulletin 767-32A0163, Revision 1, dated October 1, 1998.

Note 2:

For the purposes of this AD, a detailed visual inspection is defined as: “An intensive 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 an intensity deemed appropriate by the inspector. Inspection aids such as mirrors, magnifying lenses, etc. may be used. Surface cleaning and elaborate access procedures may be required.”

Note 3:

Boeing Service Bulletin 767-32A0163, Revision 1, dated October 1, 1998, specifies the preferred procedures for separating the wire bundles into two groups for wrapping, which is an easier method for accomplishing those actions.

Follow-On Actions, Repair, and Wire Wrapping

(1) If no discrepancy of the wire expando sleeve is detected, prior to further flight, wrap the wire expando sleeve in accordance with the alert service bulletin or Revision 1.

(2) If any discrepancy of the wire expando sleeve is detected, prior to further flight, perform a detailed visual inspection to detect discrepancies of the varglas layer, in accordance with the alert service bulletin or Revision 1.

(i) If no discrepancy of the varglas layer is detected, prior to further flight, repair and wrap the wire expando sleeve in accordance with the alert service bulletin or Revision 1.

(ii) If any discrepancy of the varglas layer is detected, prior to further flight, perform a detailed visual inspection to detect discrepancies of the wire bundles, in accordance with the alert service bulletin or Revision 1.

(A) If no discrepancy of the wire bundles is detected, prior to further flight, rewrap the wires with new varglas layer, and repair and wrap the wire expando sleeve in accordance with the alert service bulletin or Revision 1.

(B) If any discrepancy of the wire bundles is detected, prior to further flight, repair the wires, rewrap the wire bundles with new varglas layer, and repair and wrap the wire expando sleeve in accordance with the alert service bulletin or Revision 1.

Alternative Methods of Compliance

(b) 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 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

(c) 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.

Incorporation by Reference

(d) The actions shall be done in accordance with Boeing Alert Service Bulletin 767-32A0163, dated March 5, 1998, or Boeing Service Bulletin 767-32A0163, Revision 1, dated October 1, 1998. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(e) This amendment becomes effective on March 28, 2000.