Discussion
The FAA has received three reports of Raytheon Aircraft Company (Raytheon) 1900 series airplanes entering into an uncommanded roll after setting the flaps at 35. In each incident, the operator applied extreme force to the control wheel to counter the roll and landed.
Further investigation revealed that the outboard flaps detached from the flap aft roller bearings at the outboard flap inboard flap track. Detachment of the outboard flap from the roller bearing results in a flap asymmetric condition causing contact between the outboard flap and the aileron, consequently inhibiting aileron movement. In addition, as the flap aft roller bearing detaches from the outboard flap, the outer flange element of the roller bearing repositions on the bearing, resulting in contact between the outer flange element and the attachment bracket. This contact eventually wears through the attachment bracket allowing the outboard flap to detach from the aft roller bearing.
Relevant Service Information
Raytheon has issued Safety Communiqu No. 137, dated May 1997, which specifies procedures for inspecting the flap attachment brackets for signs of wear, and inspecting the aft roller bearing attachment holes for elongation. If wear from contact is visible or the roller bearing attachment holes are elongated, the Safety Communiqu specifies repairing or replacing the part.
The FAA's Determination
After examining the circumstances and reviewing all available information related to the incidents described above, including the relevant service information, the FAA has determined that AD action should be taken to preclude interference between the flap and the aileron, which could prevent aileron movement and result in possible loss of control of the airplane.
Explanation of the Provisions of the AD
Since an unsafe condition has been identified that is likely to exist or develop in other Raytheon 1900 series airplanes of the same type design, this AD requires repetitively inspecting the outboard flap attachment brackets and aft roller bearings for wear, inspecting for elongation of the holes in the flap attachment brackets, and repairing or replacing any part showing wear. The actions are to be done in accordance with the instructions in Raytheon Aircraft Safety Communiqu No. 137, dated May 1997, and Temporary Revision No. 57-1 to Raytheon Aircraft Company Beech 1900 Airliner Series Structural Repair Manual, part number 114-590021-9B, dated May 16, 1997; Reissued June 30, 1992.
Justification of Compliance Time and Determination of the Effective Date of this AD
Wear of the flap aft roller bearings and flap attachment brackets and elongation of the flap attachment bracket holes occurs over time. Examination of the referenced incidents and all information available to the FAA indicates that this problem has the potential of becoming detectable at around 2,600 ground-air-ground (GAG) cycles. Numerous 1900 series airplanes are either currently over or closely approaching this 2,600 GAG cycle threshold. These airplanes are utilized primarily in commuter service. Operators of these airplanes average anywhere from 8 GAG cycles per day to 14 GAG cycles per day. Based on these averages, operators of 1900 series airplanes would reach the above thresholds between 185 days to 325 days after manufacture of the airplane, and thereafter every 185 to 325 days after each inspection.
For these reasons, the FAA has determined that the inspections required by this AD should occur" Upon the accumulation of 2,600 GAG cycles or within the next 100 GAG cycles after the effective date of this AD, whichever occurs later, unless already accomplished, and thereafter at intervals not to exceed 2,600 GAG cycles." The 100 GAG cycles for the initial compliance time is utilized to allow a grace period for those airplanes already over the 2,600 GAG cycle time, so as not to inadvertently ground the affected airplanes.
Determination of the Effective Date of the AD
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 immediate flight safety and, thus, was not preceded by notice and opportunity to 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 should identify the Rules Docket number and be submitted in triplicate to the address specified above. 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 No. 97-CE-47-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 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 evaluationis 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.
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 a new airworthiness directive (AD) to read as follows: