AD 95-26-15

This document publishes in the Federal Register an amendment adopting an airworthiness directive that was sent previously by individual letters to all known U.S. owners and operators of various transport category airplanes equipped with Allied Signal Commercial Avionics Systems CAS-81 TCAS. This amendment is prompted by reports of failure of the audio output of the CAS-81 TCAS. This AD requires a revision to the Airplane Flight Manual to provide the flightcrew with procedures to cycle power to the TCAS processor via the circuit breaker or power bus, and to perform a TCAS functional test to verify proper operation of the TCAS. The actions specified by this AD are intended to ensure that the flightcrew is advised of the potential hazard associated with failure of the audio output of the CAS-81 TCAS, and of the procedures necessary to address it.

Final rule; request for comments.

95-26-15 ALLIED SIGNAL COMMERCIAL AVIONICS SYSTEMS: Amendment 39-9495. Docket 95-NM-270-AD.

Applicability: All CAS-81 Traffic Alert and Collision Avoidance Systems (TCAS) that are installed in, but not limited to, the following airplanes, certificated in any category:

Aerospatiale Models ATR42 and ATR72 series airplanes;

Airbus Industries Models A300, A310, and A340 series airplanes;

Beech Models 1900 and BE-65 through -90 (inclusive) series airplanes;

Boeing Models 727-100, 727-200, 737-200, 737-300, 737-400, 737-500,
747-100, 747-200, 747-300, 747-400, 747SP, 757-200, 767-200, and
767-300 series airplanes;

Convair Model CV-580 airplanes;

de Havilland Model DHC-7 series airplanes and Model DHC-8-100 airplanes;

EMBRAER Model EMB-120 series airplanes;

Fairchild Model F227 airplanes;

Fokker Models F28 Mark 100, Mark 1000, and Mark 4000 series airplanes;

General Dynamics Models Convair 340 and 440 airplanes;

Gulfstream Models G-159 and G-IV airplanes;

Lockheed Model L-1011 series airplanes;

McDonnell Douglas Models DC-8-60, DC-9-31, DC-9-51, DC-10-10,
DC-10-30, DC-10-30F, MD-11, and MD-80 series airplanes;

Rockwell International NA-265-65 airplanes;

Saab Model 340 series airplanes; and

Shorts Model 360 series airplanes.

NOTE 1: This AD applies to, but is not limited 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 use the authority provided in paragraph (b) of this AD to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition; or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any affected airplane from the applicability of this AD.

Compliance: Required as indicated, unless accomplished previously.

To ensure that the flightcrew is advised of the potential hazard associated with failure of the audio output of the CAS-81 TCAS, and of the procedures necessary to address it, accomplish the following:

(a) Within 3 calendar days after the effective date of this AD, revise the Limitations Section of the FAA-approved Airplane Flight Manual (AFM) to include the following. This may be accomplished by inserting a copy of this AD in the AFM.

"In order to ensure that the audio output of the CAS-81 TCAS operates properly, accomplish the following:

Prior to the first flight of the day; prior to the accumulation of
10 hours of uninterrupted power; and at the mid-point of any one flight scheduled to exceed 10 hours: Cycle the power to the TCAS processor via the circuit breaker or power bus.

Prior to taxi before takeoff: Initiate the TCAS functional test in
accordance with AFM procedures to verify operational condition of the CAS-81 TCAS."

(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, FAA, Atlanta Aircraft Certification Office. Operators shall submit their requests through an appropriate FAA Principal Operations Inspector, who may add comments and then send it to the Manager, Atlanta ACO.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Atlanta ACO.

(c) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR21.197 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 February 5, 1996.

On December 26, 1995, the FAA issued priority letter AD 95-26-15, applicable to Allied Signal Commercial Avionics Systems CAS-81 Traffic Alert and Collision Avoidance Systems (TCAS) that are installed in, but not limited to, various transport category airplanes. That action requires a revision to the FAA-approved Airplane Flight Manual (AFM) to provide the flightcrew with procedures to cycle power to the TCAS processor via the circuit breaker or power bus, and to perform a TCAS functional test to verify proper operation of the TCAS. That action was prompted by reports of failure of the audio output of the CAS-81 TCAS.

During bench testing, the parts manufacturer identified a capacitor in the audio output circuit that continued to build charge as long as the system was powered. The capacitor biases the audio circuit and causes failure of the audio output. The absence of audio output can occur after the TCAS has been powered without interruption for approximately 12 hours. Power interrupts (intentional or unintentional) tend to relieve the failure condition by causing the capacitor to discharge. This condition, if not corrected, could result in a critical reduction of the reliability of the CAS-81 TCAS to perform its collision avoidance function.

Since the unsafe condition described is likely to exist or develop on other airplanes of the same type design, the FAA issued priority letter AD 95-26-15 to ensure that the flightcrew is advised of the potential hazard associated with failure of the audio output of the CAS-81 TCAS, and of the procedures necessary to address it. The AD requires a revision to the AFM to provide the flightcrew with procedures to cycle power to the TCAS processor via the circuit breaker or power bus prior to the first flight of the day, prior to the accumulation of 10 hours of uninterrupted power, and at the mid-point of any one flight scheduled to exceed 10 hours. Additionally, the AD requires that, prior to taxi before takeoff, a functional test must be accomplished to verify proper operation of the TCAS.

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 letters issued on December 26, 1995, to all known U.S. owners and operators of various transport category airplanes equipped with Allied Signal Commercial Avionics Systems CAS-81 TCAS. 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 to all persons.

This is considered to be interim action. The manufacturer has advised that it currently is developing a modification that will positively address the unsafe condition addressed by this AD. Once this modification is developed, approved, and available, the FAA may consider additional rulemaking.

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 rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 95-NM-270-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, itis 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 USC 106(g), 40113, 44701.

39.13 - [AMENDED]
2. Section 39.13 is amended by adding the following new airworthiness directive: