Airworthiness Directives; Boeing Model 747-400 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-NM-81-AD; Amendment 39-8939; AD 94-12-11]

Airworthiness Directives; Boeing Model 747-400 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that

is applicable to all Boeing Model 747-400 series airplanes. This action

requires revising the Airplane Flight Manual to include procedures that

will enable the flight crew to identify fuel system leaks and to take

appropriate action to prevent further fuel loss. This amendment is

prompted by reports that flight crew procedures related to fuel system

leaks are not defined adequately in the FAA-approved AFM for these

airplanes. The actions specified in this AD are intended to ensure that

the flight crew is advised of the potential hazard related to fuel

exhaustion due to undetected leakage, and the procedures necessary to

address it.

DATES: Effective June 30, 1994.

Comments for inclusion in the Rules Docket must be received on or

before August 15, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Transport Airplane Directorate, ANM-103,

Attention: Rules Docket No. 94-NM-81-AD, 1601 Lind Avenue SW., Renton,

Washington 98055-4056.

Information concerning this rulemaking action may be examined at

the FAA, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton,

Washington.

FOR FURTHER INFORMATION CONTACT: Jon Regimbal, Aerospace Engineer,

Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate,

Seattle Aircraft Certification Office, 1601 Lind Avenue SW., Renton,

Washington 98055-4056; telephone (206) 227-2687; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION: On March 21, 1994, a Boeing Model 747-400

diverted from its intended destination airport because of indications

that insufficient fuel remained to complete the scheduled leg of the

flight. During landing and rollout, a large amount of fuel was spilled

on the runway; additionally, during application of reverse thrust, fuel

sprayed on the airplane. With such fuel leakage, the potential for a

large fire existed during and after landing; however, the fuel did not

ignite and no injuries occurred.

Investigation of this incident revealed that a major fuel leak had

developed much earlier in the flight, and that approximately 35,000

lbs. of fuel had been lost. The operator of the incident airplane

pointed out that, had a similar scenario occurred on the same flight

leg in the opposite direction, the airplane's fuel supply would have

been exhausted prior to reaching a suitable airport.

The fuel apparently had leaked from a cracked fuel tube within the

engine nacelle. The cause of the cracking currently is under

investigation by the engine manufacturer (and may be the subject of

future rulemaking, if warranted). The fuel leak was located upstream of

the fuel flow meter. Under these circumstances, sufficient fuel may

still be supplied to the engine, and the engine may operate normally.

In this particular incident, the flight crew received no immediate

indication of abnormal fuel flow (i.e., excessive fuel flow on one

engine) from the fuel flow meter. The ``FUEL DISAGREE--PROG 2/2''

Flight Management System--Control Display Unit (FMS-CDU) message and

the ``FUEL IMBALANCE'' Engine Indication and Crew Alerting System

(EICAS) message were displayed some time after the fuel began leaking.

However, because there currently are no explicit instructions in the

Airplane Flight Manual (AFM) or the Operations Manual relative to

actions that should be taken during situations such as these, the

flight crew did not initiate procedures to isolate the leak and retain

the remaining fuel on the airplane.

If the flight crew fails to detect a fuel leak, appropriate action

would not be taken to prevent further fuel loss. This condition, if not

corrected, could result in fuel exhaustion due to undetected fuel

leakage.

In light of this information, the FAA finds that certain procedures

should be included in the FAA-approved AFM for Model 747-400 series

airplanes to enable the flight crew to detect fuel system leaks and to

take appropriate action. The FAA has determined that such procedures

currently are not defined adequately in the AFM for these airplanes.

Since an unsafe condition has been identified that is likely to

exist or develop on other Boeing Model 747-400 series airplanes of the

same type design, this AD is being issued to ensure that flight crews

are advised of the potential hazard related to a significantly reduced

or exhausted airplane fuel supply, and of the procedures necessary to

address it. This AD requires revising the Non-Normal Procedures Section

of the AFM to include procedures that will enable the flight crew to

identify fuel system leaks and to take appropriate action to prevent

further fuel loss.

The applicability of this AD action is limited to only Model 747-

400 series airplane. While Model 747-100, -200, -300, SP, and SR series

airplanes have a similar fuel delivery system to that of the Model 747-

400, the indication systems and flight crew procedures for monitoring

fuel usage are significantly different for these models. These models

were designed to be operated by three flight crew members and, in the

event of a similar fuel leak on one of these airplanes, the flight

engineer would detect the fuel leak and recommend shutdown of the

appropriate engine prior to the loss of such a large quantity of fuel.

Since a situation exists that requires the immediate adoption of

this regulation, it is found that notice and opportunity for prior

public comment hereon are impracticable, and that good cause exists for

making this amendment effective in less than 30 days. -

Comments Invited

Although this action is in the form of a final rule that involves

requirements affecting flight safety and, thus, was not preceded by

notice and an opportunity for public comment, comments are invited on

this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All

communications received on or before the closing date for comments will

be considered, and this rule may be amended in light of the comments

received. Factual information that supports the commenter's ideas and

suggestions is extremely helpful in evaluating the effectiveness of the

AD action and determining whether additional rulemaking action would be

needed.

Comments are specifically invited on the overall regulatory,

economic, environmental, and energy aspects of the rule that might

suggest a need to modify the 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 that

summarizes each FAA-public contact concerned with the substance of this

AD 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 94-NM-81-AD.'' The postcard will be date stamped and

returned to the commenter.

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.

The FAA has determined that this regulation is an emergency

regulation that must be issued immediately to correct an unsafe

condition in aircraft, and that it is not a ``significant regulatory

action'' under Executive Order 12866. It has been determined further

that this action involves an emergency regulation under DOT Regulatory

Policies and Procedures (44 FR 11034, February 26, 1979). If it is

determined that this emergency regulation otherwise would be

significant under DOT Regulatory Policies and Procedures, a final

regulatory evaluation will be prepared and placed in the Rules Docket.

A copy of it, if filed, 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, 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. App. 1354(a), 1421 and 1423; 49 U.S.C.

106(g); and 14 CFR 11.89.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

94-12-11 Boeing: Amendment 39-8939. Docket 94-NM-81-AD.

Applicability: All Model 747-400 series airplanes, certificated

in any category.

Compliance: Required as indicated, unless accomplished

previously.

To ensure that the flight crew is advised of the potential

hazard associated with fuel exhaustion due to undetected fuel

leakage, and of the procedures necessary to address it, accomplish

the following:

(a) Within 60 days after the effective date of this AD, revise

the Non-Normal Procedures Section of the FAA-approved Airplane

Flight Manual (AFM) to include the following procedures, which will

enable the flight crew to identify fuel system leaks and to take

appropriate action to prevent further fuel loss. This may be

accomplished by inserting a copy of this AD in the AFM.

In-Flight Fuel Leak

If the Flight Management Computer System (FMCS) message ``FUEL

DISAGREE--PROG 2/2'' or ``INSUFFICIENT FUEL'' is displayed:

Compare the Fuel Quantity Indicating System (FQIS) total fuel

quantity and the FMC calculated fuel remaining (based on fuel flow)

with estimated fuel usage data.

If a fuel leak is suspected, turn off the stabilizer tank pump

switches, ifinstalled, the center wing tank pump switches, and the

tank 2 and 3 override pump switches, and close all crossfeed valves

(tank-to-engine fuel feed configuration). Watch for any unusual

decrease in fuel tank quantity and/or a fuel imbalance to determine

if fuel is being lost.

If an engine fuel leak is confirmed (either visually or by

flight deck indications), shut down the affected engine to stop the

leak and retain the remaining fuel. After shutdown of the affected

engine, resume normal fuel management procedures. All remaining fuel

can be used for the operating engines. Use FQIS to determine fuel

remaining.''

(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: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the Seattle ACO.

(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.

(d) This amendment becomes effective on June 30, 1994.

Issued in Renton, Washington, on June 8, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-14360 Filed 6-14-94; 8:45 am]

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