The Direction G n rale de l'Aviation Civile (DGAC), which is the airworthiness authority for France, recently notified the FAA that an unsafe condition may exist on all Aerospatiale Model ATR-42 and ATR-72 series airplanes. The DGAC advises that an ATR airplane experienced the loss of the number one direct current (DC) generator, followed by the loss of the number two DC generator, during flight. The loss of the second generator occurred following an attempt by the flightcrew to reset the number one generator, in accordance with approved procedures. After a few minutes, the airplane experienced the loss of main battery power. The cause of the failure of the second generator is currently under investigation. Such failures, if not corrected, could result in the loss of all electrical power, except the emergency battery supply, during flight.
French Airworthiness Directives
The DGAC issued French telegraphic airworthiness directives T98-148-076(B) and T98-149-038(B), both dated March 20, 1998, in order to assure the continued airworthiness of these airplanes in France. These French airworthiness directives require adherence to instructions specified in ATR AFM Chapter 5_04 in the event of one DC generator failure, and specify that no attempt should be made to reset the affected DC generator. Additionally, the French airworthiness directives note that, in the event of failure of both DC generators, resetting the generators should be attempted.
Explanation of FAA s Findings
The current version of the FAA-approved ATR Airplane Flight Manual (AFM) specifies that a single failed generator is to be left in the "OFF" position; however, the AFM does not explicitly prohibit an attempted reset of a failed generator. Moreover, for some operators, Flight Crew Operating Manuals may contain instructions for one attempt to reset a failed generator. Therefore, the FAA has determined that explicit instructions must be provided in the Limitations section of the AFM to specify that flight crews should not attempt to reset a single failed generator. However, in the event of dual DC generator failure, reset of the generators should be attempted.
FAA's Conclusions
These airplane models are manufactured in France and are 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 DGAC has kept the FAA informed of the situation described above. The FAA has examined the findings of the DGAC, 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.
Explanation of Requirements of Rule
Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design registered inthe United States, this AD is being issued to prevent failure of the second of two DC generators after the failure of the first generator, which could lead to the loss of main battery power and result in the loss of all electrical power, except the emergency battery supply, during flight. This AD requires revising the Limitations Section of the AFM to add specific flightcrew instructions to be followed in the event of failure of one or both of DC generators.
Interim Action
This is considered to be interim action. The manufacturer has advised the FAA that it is currently investigating the cause of the dual generator failure and may develop a modification that will positively address the unsafe condition in this AD. Once the investigation is concluded, the FAA may consider further rulemaking.
Determination of Rule's Effective Date
Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public commenthereon 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 rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 98-NM-124-AD." The postcard will be date stamped and returned to the commenter.
Regulatory Impact
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, Aviationsafety, 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. 106(g), 40113, 44701.
39.13 [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive: