01-4220. Airworthiness Directives; Boeing Model 747-400 Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 747-400 series airplanes. This proposal would require an inspection to detect miswiring of diodes in the heating system of the pitot static probes, and corrective action, if necessary. This action is necessary to prevent reduced power to the heating system of the pitot static probes, leading to ice accumulation on the pitot static probes, which could result in erroneous airspeed or altitude indications to the flight crew, and consequent reduced operational safety in all phases of flight. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by April 9, 2001.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-320-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. Comments may be submitted via fax to [phone]. Comments may also be sent via the Internet using the following address: [e-mail]. Comments sent via fax or the Internet must contain “Docket No. 2000-NM-320-AD” in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 for Windows or ASCII text.

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:

Don Eiford, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

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 action may be changed in light of the comments received.

Submit comments using the following format:

• Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
• For each issue, state what specific change to the proposed AD is being requested.
• Include justification (e.g., reasons or data) for each request.

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 action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2000-NM-320-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. 2000-NM-320-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received reports indicating that several operators have found burnt diodes in the heating system of the pitot static probes on certain Boeing Model 747-400 series airplanes. Investigation revealed that diodes in the power reduction circuitry were miswired. The miswiring results in the probe-head heat element always being at full-power, while the probe strut heater is only at half-power. If the probe strut heater is only at half-power, ice may accumulate on the pitot static probes. This condition, if not corrected, could result in erroneous airspeed or altitude indications to the flight crew, and consequent reduced operational safety in all phases of flight.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin 747-30A2078, Revision 1, dated November 16, 2000, which describes procedures for an inspection to detect miswiring of diodes in the heating system of the pitot probes. The inspection involves using a multimeter to verify continuity between certain relay sockets, absence of a diode between certain relay sockets, and diode orientation between certain relay sockets. If any miswiring is found, the service bulletin specifies to rewire per Boeing 747-400 Wiring Diagrams 30-31-11 and 30-31-21. Doing the actions in the service bulletin is intended to adequately address the identified unsafe condition.

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 require operators to do the actions specified in the service bulletin described previously, except as discussed below.

Differences Between This Proposed AD and the Service Bulletin

Operators should note that, although the service bulletin recommends accomplishing the inspection at the earliest maintenance opportunity when manpower and facilities are available, the FAA has determined that this compliance time may not ensure that the identified unsafe condition is addressed in a timely manner. In developing an appropriate compliance time for this proposed AD, the FAA 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 proposed AD. In light of all of these factors, the FAA finds a 15-month compliance time to be warranted, in that it represents an appropriate interval of time allowable for affected airplanes to continue to operate without compromising safety.

Operators also should note that, while the service bulletin describes only an inspection/verification that necessitates use of a multimeter, this proposed AD refers to this inspection/verification as a “special detailed inspection.” The definition of a “special detailed inspection” is included as a note in the proposed AD.

Cost Impact

There are approximately 497 airplanes of the affected design in the worldwide fleet. The FAA estimates that 69 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 2 work hours per airplane to accomplish the proposed actions, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $8,280, or $120 per airplane.

The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this proposed AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions.

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 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

[Amended]

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

Boeing: Docket 2000-NM-320-AD.

Applicability: Model 747-400 series airplanes, as listed in Boeing Alert Service Bulletin 747-30A2078, Revision 1, dated November 16, 2000; 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 reduced power to the heating system of the pitot static probes, leading to ice accumulation on the pitot static probes, which could result in erroneous airspeed or altitude indications to the flight crew, and consequent reduced operational safety in all phases of flight, accomplish the following:

Inspection

(a) Within 15 months after the effective date of this AD, perform a special detailed inspection to detect miswiring of diodes in the heating system of the pitot static probes by using a multimeter to verify continuity between certain relay sockets, absence of a diode between certain relay sockets, and diode orientation between certain relay sockets, per Boeing Alert Service Bulletin 747-30A2078, Revision 1, dated November 16, 2000. If any miswiring is found, rewire per Boeing 747-400 Wiring Diagrams 30-31-11 and 30-31-21, as referenced in the service bulletin.

Note 2:

Inspections accomplished prior to the effective date of this AD per Boeing Alert Service Bulletin 747-30A2078, dated August 24, 2000, are considered acceptable for compliance with the applicable action specified in this amendment.

Note 3:

For the purposes of this AD, a special detailed inspection is defined as: “An intensive examination of a specific item(s), installation, or assembly to detect damage, failure, or irregularity. The examination is likely to make extensive use of specialized inspection techniques and/or equipment. Intricate cleaning and substantial access or disassembly procedures may be required.”

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. 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.

Issued in Renton, Washington, on February 13, 2001.

Vi L. Lipski,

Manager, Transport Airplane Directorate, Aircraft Certification Service.