AD 96-23-16

Effective November 25, 1996 to all persons except those persons to whom it was made immediately effective by emergency AD 96-23-16, issued November 8, 1996, which contained the requirements of this amendment.

Comments for inclusion in the Rules Docket must be received on or before January 21, 1997.

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 96-NM-262-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.

Tim Dulin, Aerospace Engineer, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 227-2141; fax (206) 227-1149.

On November 8, 1996, the FAA issued emergency AD 96-23-16, which is applicable to all Fokker Model F28 Mark 0070 and 0100 series airplanes.

That AD was prompted by notification from the Rijksluchtvaartdienst (RLD), which is the airworthiness authority for the Netherlands, that an unsafe condition may exist on all Fokker Model F28 Mark 0070 and 0100 series airplanes. The RLD advised that, on October 31, 1996, a Fokker Model F28 Mark 0100 series airplane was involved in an accident shortly after take-off in Sao Paulo, Brazil.

Preliminary accident investigation results indicate that, during take-off, the thrust reverser of the right-hand engine may have inadvertently deployed. The cause of this possible deployment is unknown at this time.

However, the results of a study conducted by Fokker following the accident revealed that a malfunction of the secondary lock of the thrust reverser may occur without indication to the flightcrew. The secondary lock of the thrust reverser may remain in the unlocked position (i.e., No. 1 relay energized) in conditions when it should be locked. The secondary lock is a backup to the primary actuator lock and is designed to open only when thrust reverser deployment is commanded. If the flightcrew is unaware that the secondary lock is in the unlocked position, the airplane may take off with reduced safety margins. Currently, there are no indications that the secondary lock No. 1 relay failure contributed to the accident that occurred on October 31.

An unannunciated failure of the secondary lock of the thrust reversers could result in reduced protection against inadvertent deployment of the thrust reversers in-flight.

The thrust reverser system that is installed on Fokker Model F28 Mark 0100 series airplanes is identical in design to that installed on Fokker Model F28 Mark 0070 series airplanes. Therefore, the FAA finds that both of these models are subject to the same unsafe condition identified in this AD.

Fokker has developed procedural information, for inclusion in the Airplane Flight Manual (AFM) of the affected airplanes, that will enable the flightcrew to determine if the thrust reversers are properly locked prior to take-off by monitoring proper engagement of the autothrottle system (ATS).

Fokker also has developed procedural information to prohibit dispatch of the airplane with both autothrottle channels inoperative, unless both thrust reversers are deactivated and secured in the stowed position, and no operations are conducted that are predicated on thrust reverser operation.

In addition, Fokker has developed procedural information, for inclusion in the airplane maintenance program of the affected airplanes, that will provide instructions to correct thrust reverser malfunctions.

All of the procedures described in these documents will contribute to preventing the unannunciated failure of the secondary lock of the thrust reversers, which could result in reduced protection against inadvertent deployment of the thrust reversers during flight.

The RLD classified these procedures as mandatory, and issued Netherlands airworthiness directive BLA 1996-138 (A), dated November 7, 1996, in order to assure the continued airworthiness of these airplanes in the Netherlands.

This airplane model is manufactured in the Netherlands and is type certificated for operation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, the RLD has kept the FAA informed of the situation described above. The FAA has examined the findings of the RLD, reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States.

Since the unsafe condition described is likely to exist or develop on other airplanes of the same type design registered in the United States, the FAA issued emergency AD 96-23-16 to prevent an unannunciated failure of the secondary lock of the thrust reversers, which could result in reduced protection against inadvertent deployment of the thrust reversers during flight. The AD requires:

1. Revising the Limitations Section of the FAA-approved AFM to enable the flightcrew to determine if the thrust reversers are properly locked prior to take-off by monitoring proper engagement of the ATS;

2. Prohibiting the dispatch of the airplane with both autothrottle channels inoperative, unless both thrust reversers are deactivated and secured in the stowed position, and no operations are conducted that are predicated on thrust reverser operation; and

3. Revising the FAA-approved maintenance program to provide instructions to correct thrust reverser malfunctions.

Since it was found that immediate corrective action was required, notice and opportunity for prior public comment thereon were impracticable and contrary to the public interest, and good cause existed to make the AD effective immediately by individual notices issued on November 8, 1996, to all known U.S. owners and operators of Fokker Model F28 Mark 0070 and 0100 series airplanes. These conditions still exist, and the AD is hereby published in the Federal Register as an amendment to section 39.13 of the Federal Aviation Regulations (14 CFR 39.13) to make it effective as to all persons.

This is considered to be interim action until final action is identified, at which time the FAA may consider further rulemaking.

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 rule must submit a self-addressed, stamped postcard on which the following statement is made: ``Comments to Docket Number 96-NM-262-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.

Air transportation, Aircraft, Aviation safety, Safety.

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:

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.