E6-4443. Airworthiness Directives; McDonnell Douglas Model 717-200 Airplanes

AGENCY:

Federal Aviation Administration (FAA), Department of Transportation (DOT).

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for certain McDonnell Douglas Model 717-200 airplanes. This proposed AD would require replacing the lightning critical clamp bases of the fuel tank vent system with improved clamp bases; and checking the electrical bond of the modified self-bonding mounting clamps. This proposed AD results from an investigation that revealed the aluminum foil strip on the nylon base of the ground clamps can fracture or separate from the base. We are proposing this AD to ensure that the fuel pipes are properly bonded to the airplane structure. Improper bonding could prevent electrical energy from a lightning strike from dissipating to the airplane structure, which could result in a fuel tank explosion.

DATES:

We must receive comments on this proposed AD by May 12, 2006.

ADDRESSES:

Use one of the following addresses to submit comments on this proposed AD.

• DOT Docket Web site: Go to http://dms.dot.gov and follow the instructions for sending your comments electronically.
• Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically.
• Mail: Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street, SW., Nassif Building, room PL-401, Washington, DC 20590.
• Fax: [phone].
• Hand Delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

Contact Boeing Commercial Airplanes, Long Beach Division, 3855 Lakewood Boulevard, Long Beach, California 90846, Attention: Data and Service Management, Dept. C1-L5A (D800-0024), for the service information identified in this proposed AD.

FOR FURTHER INFORMATION CONTACT:

Serj Harutunian, Aerospace Engineer, Propulsion Branch, ANM-140L, FAA, Los Angeles Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood, California 90712-4137; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to submit any relevant written data, views, or arguments regarding this proposed AD. Send your comments to an address listed in the ADDRESSES section. Include the docket number “FAA-2006-24256; Directorate Identifier 2006-NM-010-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments received by the closing date and may amend the proposed AD in light of those comments.

We will post all comments we receive, without change, to http://dms.dot.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this proposed AD. Using the search function of that web site, anyone can find and read the comments in any of our dockets, including the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You may review DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you may visit http://dms.dot.gov.

Examining the Docket

You may examine the AD docket on the Internet at http://dms.dot.gov, or in person at the Docket Management Facility office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Management Facility office (telephone [phone]) is located on the plaza level of the Nassif Building at the DOT street address stated in the ADDRESSES section. Comments will be available in the AD docket shortly after the Docket Management System receives them.

Discussion

The FAA has examined the underlying safety issues involved in fuel tank explosions on several large transport airplanes, including the adequacy of existing regulations, the service history of airplanes subject to those regulations, and existing maintenance practices for fuel tank systems. As a result of those findings, we issued a regulation titled “Transport Airplane Fuel Tank System Design Review, Flammability Reduction and Maintenance and Inspection Requirements” (67 FR 23086, May 7, 2001). In addition to new airworthiness standards for transport airplanes and new maintenance requirements, this rule included Special Federal Aviation Regulation No. 88 (“SFAR 88,” Amendment 21-78, and subsequent Amendments 21-82 and 21-83).

Among other actions, SFAR 88 requires certain type design (i.e., type certificate (TC) and supplemental type certificate (STC)) holders to substantiate that their fuel tank systems can prevent ignition sources in the fuel tanks. This requirement applies to type design holders for large turbine-powered transport airplanes and for subsequent modifications to those airplanes. It requires them to perform design reviews and to develop design changes and maintenance procedures if their designs do not meet the new fuel tank safety standards. As explained in the preamble to the rule, we intended to adopt airworthiness directives to mandate any changes found necessary to address unsafe conditions identified as a result of these reviews.

In evaluating these design reviews, we have established four criteria intended to define the unsafe conditions associated with fuel tank systems that require corrective actions. The percentage of operating time during which fuel tanks are exposed to flammable conditions is one of these criteria. The other three criteria address the failure types under evaluation: single failures, single failures in combination with another latent condition(s), and in-service failure experience. For all four criteria, the evaluations included consideration of previous actions taken that may mitigate the need for further action.

We have determined that the actions identified in this AD are necessary to reduce the potential of ignition sources inside fuel tanks, which, in combination with flammable fuel vapors, could result in fuel tank explosions and consequent loss of the airplane.

We have received a report indicating that the electrical bonds of in-tank fuel system components were degrading on McDonnell Douglas DC-9 and MD-80 airplanes. Investigation revealed that the aluminum foil strip on the nylon base of the ground clamps can fracture or separate from the base. These grounded clamp bases are used to bond the fuel pipe to the airplane structure in the wing leading edge, main fuel tanks, center fuel tank, and aft fuselage on Model 717-200 airplanes. Bonding of the fuel pipes to the airplane structure is critical to ensure that electrical energy from a lightning strike dissipates to the airplane structure. This condition, if not corrected, could result in a fuel tank explosion.

The grounded clamp bases on certain Model 717-200 airplanes are identical to those on the affected Model DC-9 and MD-80 airplanes. Therefore, all of these models may be subject to the same unsafe condition.

Other Related Rulemaking

Boeing has issued Service Bulletin DC9-28-211, dated February 23, 2005, to address replacing the clamp bases for the fuel vent pipe with improved clamp bases on all McDonnell Douglas Model DC-9-10, -20, -30, -40, and -50 series airplanes; we are planning to address the unsafe condition of that service bulletin with a separate rulemaking action.

Relevant Service Information

We have reviewed Boeing Service Bulletin 717-28-0004, Revision 2, dated March 11, 2005. The service bulletin describes procedures for replacing the grounded clamp bases for the fuel pipes located in the wing leading edge, main fuel tanks, center fuel tank, and aft fuselage with improved clamp bases; and checking the electrical bond of the modified self-bonding mounting clamps. Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition.

The service bulletin refers to Chapter 28-00-00 of Boeing 717 Aircraft Maintenance Manual and Chapter 20-50-01, Class “L,” of the Boeing 717 Standard Wiring Practices Manual as additional sources of service information for checking the electrical bond of the modified self-bonding clamps.

FAA's Determination and Requirements of the Proposed AD

We have evaluated all pertinent information and identified an unsafe condition that is likely to exist or develop on other airplanes of this same type design. For this reason, we are proposing this AD, which would require accomplishing the actions specified in the service information described previously, except as discussed under “Differences Between the NPRM and Service Bulletin.”

Differences Between the NPRM and Service Bulletin

The service bulletin describes procedures for replacing 43 grounded clamp bases with improved clamp bases, as identified in Tables 1 and 2 of the Accomplishment Instructions. This NPRM, however, proposes to require replacing only the lightning critical clamp bases identified in Table 1. We have determined that replacement of the lightning critical clamp bases adequately addresses the unsafe condition identified in this NPRM.

The service bulletin specifies checking the electrical bond of the modified self-bonding mounting clamps, but does not specify what corrective action to take if an electrical bond fails that check. This NPRM proposes to require, before further flight, repairing any electrical bond of the mounting clamp according to a method approved by the Manager, Los Angeles Aircraft Certification Office, FAA. Chapter 28-00-00 of Boeing 717 Aircraft Maintenance Manual and Chapter 20-50-01 of the Boeing 717 Standard Wiring Practices Manual are one approved method for repairing an electrical bond.

Although the service bulletin recommends accomplishing the replacements “at a scheduled maintenance period when manpower, materials, and facilities are available,” we have determined that this imprecise compliance time would not address the identified unsafe condition in a timely manner. In developing an appropriate compliance time for this AD, we considered not only the manufacturer's recommendation, but 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 modifications. In light of all of these factors, we find a compliance time of 78 months for completing the required actions to be warranted, in that it represents an appropriate interval of time for affected airplanes to continue to operate without compromising safety. This difference has been coordinated with the airplane manufacturer.

Costs of Compliance

There are about 120 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 92 airplanes of U.S. registry. The proposed actions would take about 16 work hours per airplane, at an average labor rate of $80 per work hour. Required parts would cost about $239 per airplane. Based on these figures, the estimated cost of the proposed AD for U.S. operators is $139,748, or $1,519 per airplane.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in subtitle VII, part A, subpart III, section 44701, “General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

Regulatory Findings

We have determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD 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.

For the reasons discussed above, I certify that the 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. 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.

We prepared a regulatory evaluation of the estimated costs to comply with this proposed AD and placed it in the AD docket. See the ADDRESSES section for a location to examine the regulatory evaluation.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 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

[Amended]

2. The Federal Aviation Administration (FAA) amends § 39.13 by adding the following new airworthiness directive (AD):

McDonnell Douglas: Docket No. FAA-2006-24256; Directorate Identifier 2006-NM-010-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by May 12, 1006.

Affected ADs

(b) None.

Applicability

(c) This AD applies to McDonnell Douglas Model 717-200 airplanes, certificated in any category; as identified in Boeing Service Bulletin 717-28-0004, Revision 2, dated March 11, 2005.

Unsafe Condition

(d) This AD results from an investigation that revealed the aluminum foil strip on the nylon base of the ground clamps can fracture or separate from the base. We are issuing this AD to ensure that the fuel pipes are properly bonded to the airplane structure. Improper bonding could prevent electrical energy from a lightning strike from dissipating to the airplane structure, which could result in a fuel tank explosion.

Compliance

(e) You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.

Replace the Grounded Clamp Bases

(f) Within 78 months after the effective date of this AD, replace the lightning critical clamp bases of the fuel tank vent system with improved clamp bases, in accordance with Table 1 of Figure 1 of the Accomplishment Instructions of Boeing Service Bulletin 717-28-0004, Revision 2, dated March 11, 2005. Before further flight after the replacement, check the electrical bond of the modified self-bonding mounting clamps in accordance with the service bulletin. If any electrical bond fails the check, before further flight, repair the electrical bond of the mounting clamp according to a method approved by the Manager, Los Angeles Aircraft Certification Office (ACO), FAA. Chapter 28-00-00 of the Boeing 717 Aircraft Maintenance Manual and Chapter 20-50-01 of the Boeing 717 Standard Wiring Practices Manual are one approved method.

Alternative Methods of Compliance (AMOCs)

(g)(1) The Manager, Los Angeles ACO, FAA, has the authority to approve AMOCs for this AD, if requested in accordance with the procedures found in 14 CFR 39.19.

(2) Before using any AMOC approved in accordance with § 39.19 on any airplane to which the AMOC applies, notify the appropriate principal inspector in the FAA Flight Standards Certificate Holding District Office.

Issued in Renton, Washington, on March 20, 2006.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.