Discussion
What events have caused this AD? The FAA has received reports of two incidents involving temporary loss of all attitude display information during flight on certain Raytheon Model 390 airplanes. Through investigation and testing, we discovered that moisture is entering the aft power distribution box through the aft ram air duct, which could freeze and/or cause corrosion to form in the left-hand and right-hand generator relays, battery tie relay, and the essential bus relay. This condition could cause the relays to fail in the open position or fail in the mid position and result in loss of power.
Raytheon issued Safety Communique No. 222, dated April 2002, to inform the owners/operators that power to the standby electrical bus can be restored by placing the Battery switch in the STBY position to allow continued flight and landing.
What are the consequences if the condition is not corrected? This condition, if not corrected, couldresult in electrical power failure. Such failure could lead to loss of all attitude display information during flight.
Is there service information that applies to this subject? Raytheon has issued Mandatory Service Bulletin SB 24-3606, Issued: April, 2003; and Mandatory Service Bulletin 24-3544, Issued; November, 2002.
What are the provisions of this service information? These service bulletins include procedures for:
Modifying the aft power distribution box by replacing part number SM400D79 (left-hand and right-hand generator relays and battery tie relay) with part number SM400D79-1 relays, and replacing part number SM150D22 (essential bus relay) with part number SM150D22-1 relay; and
Modifying the aft ram air duct.
The FAA's Determination and an Explanation of the Provisions of This AD
What has FAA decided? The FAA has reviewed all available information, including the service information referenced above; and determined that:
The unsafe condition referenced in this document exists or could develop on other Raytheon Model 390 airplanes of the same type design;
The actions specified in the previously-referenced service information should be accomplished on the affected airplanes; and
AD action should be taken in order to correct this unsafe condition.
What does this AD require? This AD requires you to incorporate the actions in the previously-referenced service bulletins.
In preparation of this rule, we contacted type clubs and aircraft operators to obtain technical information and information on operational and economic impacts. We did not receive any information through these contacts. If received, we would have included, in the rulemaking docket, a discussion of any information that may have influenced this action.
How does the revision to 14 CFR part 39 affect this AD? On July 10, 2002, FAA published a new version of 14 CFR part 39 (67 FR 47997, July 22, 2002), which governs FAA's AD system. This regulation now includes material that relates to special flight permits, alternative methods of compliance, and altered products. This material previously was included in each individual AD. Since this material is included in 14 CFR part 39, we will not include it in future AD actions.
Will I have the opportunity to comment prior to the issuance of the rule? Because the unsafe condition described in this document could result in loss of all attitude display information during flight, we find that notice and opportunity for public prior comment are impracticable. Therefore, good cause exists for making this amendment effective in less than 30 days.
Comments Invited
How do I comment on this AD? Although this action is in the form of a final rule and was not preceded by notice and opportunity for public comment, FAA invites your comments on the rule. You may submit whatever written data, views, or arguments you choose. You need to include the rule's docket number and submit your comments to the address specified under the caption ADDRESSES. We will consider all comments received on or before the closing date specified above. We may amend this rule in light of comments received. Factual information that supports your ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether we need to take additional rulemaking action.
Are there any specific portions of the AD I should pay attention to? We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. You may view all comments we receive before and after the closing date of the rule in the Rules Docket. We will file a report in the Rules Docket that summarizes each FAA contact with the public that concerns the substantive parts of this AD.
How can I be sure FAA receives my comment? If you want us to acknowledge the receipt of your comments, you must include a self- addressed, stamped postcard. On the postcard, write "Comments to Docket No. 2003-CE-18-AD." We will date stamp and mail the postcard back to you.
Regulatory Impact
Does this AD impact various entities? These regulations will 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, FAA has determined that this final rule does not have federalism implications under Executive Order 13132.
Does this AD involve a significant rule or regulatory action? We have determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and 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 (otherwise, an evaluation is not required). A copy of it, if filed, may be obtained from the Rules Docket.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.