# AD 94-07-01: Modify Cavity Vent Drain Tube Assembly - Type: Airworthiness directive - Status: Current - Products: Boeing MD-11 and MD-11F - Effective: May 16, 1994 - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Large airplane - Amendment: 39-8859 - Docket: 93-NM-162-AD - Registered aircraft: 108 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/214AF778E561246286256A0800676802.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/94-07-01 ## Summary This amendment adopts a new airworthiness directive (AD), applicable to certain McDonnell Douglas Model MD-11 and MD-11F series airplanes, that requires modification of the cavity vent drain tube assembly at the center wing lower auxiliary fuel tank cavity. This amendment is prompted by a report that the cavity vent tube, if not properly grounded, could act as an electrical path in the event of a lightening strike. The actions specified by this AD are intended to prevent arcing in the tank cavity and possible resulting fire. ## The airworthiness directive 94-07-01 MCDONNELL DOUGLAS: Amendment 39-8859. Docket 93-NM-162-AD. Applicability: Model MD-11 and MD-11F series airplanes; as listed in McDonnell Douglas MD-11 Service Bulletin 28-42, dated August 12, 1993; certificated in any category. Compliance: Required as indicated, unless accomplished previously. To prevent arcing in the tank cavity and possible resulting fire, accomplish the following: (a) Within 18 months after the effective date of this AD, modify the cavity vent drain tube assembly at the center wing lower auxiliary fuel tank cavity in accordance with McDonnell Douglas MD-11 Service Bulletin 28-42, dated August 12, 1993. (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, Los Angeles 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, Los Angeles ACO. NOTE: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Los Angeles ACO. (c) Special flight permits may be issued in accordance with Federal Aviation Regulations (FAR) 21.197 and 21.199 to operate the airplane to a location where the requirements of this AD can be accomplished. (d) The modification shall be done in accordance with McDonnell Douglas MD-11 Service Bulletin 28-42, dated August 12, 1993. 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 McDonnell Douglas Corporation, P.O. Box 1771, Long Beach, California 90846-1771, Attention: Business Unit Manager, Technical Publications - Technical Administrative Support, C1-L5B. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Los Angeles Aircraft Certification Office (ACO), 3229 East Spring Street, Long Beach, California; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. (e) This amendment becomes effective on May 16, 1994. ## Rule preamble ### Supplementary information A proposal to amend part 39 of the Federal Aviation Regulations to include an airworthiness directive (AD) that is applicable to certain McDonnell Douglas Model MD-11 and MD-11F series airplanes was published in the Federal Register on November 4, 1993 (58 FR 58808). That action proposed to require modification of the cavity vent drain tube assembly located in the center wing lower auxiliary fuel tank. Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. One commenter supports the proposed rule. The Air Transport Association (ATA) of America, on behalf of one of its member operators, requests that the proposal be withdrawn. The commenter maintains that the proposed modification will allow some fuel leakage within specified limits into the lower auxiliary tank cavity. This commenter asserts that, if this modification is not mandated by the FAA, then fuel will not be permitted to leak into the cavity and, unless fuel/vapor is present, there is no risk of fire in this cavity in the event of a lighting strike. The commenter also points out that a daily check to detect fuel leakage in the cavity drain valve is currently specified in the On Aircraft Maintenance Planning (OAMP) document for Model MD-11 series airplanes. The commenter concludes that, since these inspections are performed on a daily basis, and since fuel will not be permitted to leak into the cavity if the modification is not mandated, then a lightning strike will not pose a threat to an area containing fuel or fuel vapor. The FAA does not concur that withdrawal of the proposal is appropriate. First, the FAA points out that the OAMP document is not a mandated, FAA-approved document; therefore, regardless of the number or types of inspections that are contained in it, there is no assurance that operators will strictly comply with those inspections or theindicated inspection intervals. Additionally, there is always the potential that a fuel leak could develop during flight between inspection intervals. Second, the FAA has determined that, since the required modification of the cavity vent drain tube assembly will prevent the possibility of a lightning strike traveling up the cavity vent tube, the possibility of arcing in the fuel tank cavity is thereby eliminated (regardless of whether or not fuel/vapor is present). Further, the FAA has determined that long term continued operational safety will be better assured by actual modification of the cavity vent drain tube assembly to remove the source of the problem, rather than by continuous inspections. Long term inspections may not be providing the degree of safety assurance necessary for the transport airplane fleet. This, coupled with a better understanding of the human factors associated with numerous continual inspections, has led the FAA to consider placing less emphasis on inspections and more emphasis on design improvements. The modification required by this AD is in consonance with these considerations. The ATA also requests that the proposed compliance time of 12 months for the modification be extended to 18 months. Such an extension would permit accomplishment of the proposed modification during regularly scheduled maintenance visits for most affected operators and would preclude special scheduling at considerable expense. The FAA concurs. Upon consideration of the information provided by the commenter, and the fact that there have been no in-service incidents of arcing or fire in the tank cavity (related to grounding problems in the cavity vent drain tube assembly), the FAA has determined that extending the compliance time by 6 additional months will not adversely affect safety. Paragraph (a) of the final rule has been revised accordingly. After careful review of the available data, including the comments noted above, the FAA has determinedthat air safety and the public interest require the adoption of the rule with the change previously described. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD. There are approximately 73 McDonnell Douglas Model MD-11 and MD-11F series airplanes of the affected design in the worldwide fleet. The FAA estimates that 29 airplanes of U.S. registry will be affected by this AD, that it will take approximately 3 work hours per airplane to accomplish the required actions, and that the average labor rate is $55 per work hour. Required parts will cost approximately $120 per airplane. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $8,265, or $285 per airplane. The total 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 actionsin the future if this AD were not adopted. 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 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. ยง 39.13 - (Amended) 2. Section 39.13 is amended by adding the following new airworthiness directive: ## Affected data sheets (1) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS A22WE](https://openairdocs.org/tcds/A22WE): The Boeing Company; names 2 of 11 models: MD-11, MD-11F ## Registered aircraft it may apply to (OpenAirDocs) Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment. - Aircraft: 108 (108 by airframe model, 0 by engine model) - Makers: Mcdonnell Douglas 104, Boeing 4 Models with the most aircraft: - [Mcdonnell Douglas MD-11F](https://openairdocs.org/model/mcdonnell-douglas-md-11f): 100 aircraft (airframe model) - [Mcdonnell Douglas MD-11](https://openairdocs.org/model/mcdonnell-douglas-md-11): 4 aircraft (airframe model) - [Boeing MD-11F](https://openairdocs.org/model/boeing-md-11f): 4 aircraft (airframe model) All 3 models: https://openairdocs.org/ad/94-07-01/models.md Every aircraft: https://openairdocs.org/ad/94-07-01/aircraft.md Its text cites no advisory circulars or STCs. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.