The FAA has received reports of two incidents where a Fairchild Aircraft SA226 series airplane made an emergency main gear-up landing when the main landing gear (MLG) door stop bolts and striker plate hardware jammed and prevented the MLG from extending. Investigation revealed that misalignment of the bolts and striker caused this jamming. This misalignment occurred because the gear did not fully extend upon gear retraction after the previous take-off, which was caused by low hydraulic fluid in the strut.
The landing gear oleos on these airplanes can fail to fully extend on takeoff when the hydraulic fluid upper chamber is under-serviced. Hydraulic servicing of the struts is not part of the affected airplanes' regular maintenance program. The FAA has requested that Fairchild Aircraft include hydraulic servicing as part of the maintenance program in the future. In the meantime, the FAA has determined that the struts should be serviced within a certain period of time to ensure that a low hydraulic fluid level does not exist in the strut.
In addition, Fairchild Aircraft Service Bulletin (SB) 226-32-043, Revised: September 6, 1983, specifies procedures for a MLG door stop installation. The FAA has determined that problems could occur on airplanes with this door stop installation. If the MLG oleo fails to fully extend upon gear retraction, the door stop bolts are positioned differently as they are attached to the upper torque links. This can force the stop bolts against the striker plate attach bolts, which can jam the doors and could prevent subsequent gear extension. Normally, the gear squat switch would prevent the gear from retracting if the "air" position was not achieved; however, the tolerance of the position of the "make-break" point of the switch is such that retraction is initiated even if the oleo has not fully extended.
After examining the circumstances and reviewing all available information related to theincidents described above, the FAA has determined that (1) the stop bolts on the bracket assembly upper scissors should be removed from those airplanes with a MLG door stop that has been installed in accordance with Fairchild Aircraft SB 226-32-043, Revised: September 6, 1983; (2) the MLG oleos on the SA226 series airplanes should be serviced within a certain period of time; and (3) AD action should be taken to mandate these actions in order to prevent the MLG doors from jamming, which could prevent the gear from extending and could result in an emergency gear-up landing.
Since an unsafe condition has been identified that is likely to exist or develop in other Fairchild Aircraft SA226 series airplanes of the same type design, this AD requires removing the stop bolts from the bracket assembly on the upper scissors for those airplanes with a MLG door stop installation, and servicing the MLG oleos for all affected airplanes.
Since a situation exists (possible emergency gear-up landing) that requires the immediate adoption of this regulation, it is found that notice and opportunity for public prior 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 notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket No. 95-CE-36-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 and 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.
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), 40101, 40113, 44701.
Section 39.13 - [AMENDED]
2. Section 39.13 is amended by adding a new airworthiness directive to read as follows: