AD 95-17-14

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Bombardier Model CL-600-1A11, CL-600-2A12, and CL-600-2B16 series airplanes. This action requires functional testing of the brake of the horizontal stabilizer trim actuator (HSTA); and exercising the pitch trim system, revising the FAA-approved Airplane Flight Manual (AFM), operational testing of the HSTA, and replacing the HSTA or horizontal stabilizer trim control unit, if necessary. This amendment is prompted by reports of overspeed annunciation of the pitch trim due to slippage of the no-back device on the HSTA. The actions specified in this AD are intended to prevent uncommanded movement of the HSTA due to failure of the no-back device on the HSTA to operate properly; this condition could adversely affect the controllability of the airplane.

Final rule; request for comments

95-17-14 BOMBARDIER, INC. (Formerly Canadair): Amendment 39-9344. Docket 95-NM-139-AD.
Applicability: Model CL-600-1A11 (CL-600) series airplanes having serial numbers 1004 through 1085 inclusive; Model CL-600-2A12 (CL-601) series airplanes having serial numbers 3001 through 3066 inclusive; and Model CL-600-2B16 (CL-601-3A and -3R) series airplanes having serial numbers 5001 through 5137 inclusive, and 5139 through 5299 inclusive; certificated in any category.

NOTE 1: This AD applies 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 (e) 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 airplane from the applicability of this AD.

Compliance: Required as indicated, unless accomplished previously.

To prevent uncommanded movement of the horizontal stabilizer trim actuator (HSTA), accomplish the following:

(a) Within 20 hours time-in-service after the effective date of this AD, perform the following "Functional Test Procedures of the HSTA Brake":

(1) Press the CHAN 1 INOP/CHAN 2 INOP switch/light and then the OVSP/CHNG CHAN switch/light on the center pedestal control panel.

(2) Set and hold the pitch trim switch on the pilot's control wheel until the stabilizer is in full NOSE UP position.

(3) Set andhold the pitch trim switch on the pilot's control wheel to NOSE DOWN position and, while the stabilizer is moving, press the PITCH TRIM DISC switch on the pilot's control wheel when the needle on the stabilizer trim position indicator reaches the first marking of the take-off configuration green band. Verify that both CHAN INOP lights are on.

(4) Verify that the stabilizer over-travel is less than one degree, as read on the stabilizer trim position indicator on the center instrument panel.

NOTE 2: One increment on the stabilizer trim position indicator is equal to one degree of stabilizer travel.

(i) If the stabilizer over-travel is less than or equal to one degree, the pitch trim brake performance meets the ground performance requirements and is considered serviceable.

(ii) If the stabilizer over-travel is more than one degree, dispatch is prohibited. Correction is required prior to further flight, in accordance with Bombardier Alert Service Bulletin A600-0645, dated January 11, 1995 (for Model CL-600-1A11 series airplanes), or A601-0443, dated January 11, 1995 (for Model CL-600-2A12 and CL-600-2B16 series airplanes), as applicable.

(b) For airplanes on which the stabilizer over-travel is shown to be equal to or less than 1 degree during the functional test required by paragraph (a) of this AD, and no overspeed annunciation has been reported previously, repeat the functional test thereafter at intervals not to exceed 100 hours time-in-service.

(c) For airplanes on which the stabilizer over-travel is shown to be equal to or less than 1 degree during the functional test required by paragraph (a) of this AD, and overspeed annunciation has been reported previously, accomplish paragraphs (c)(1), (c)(2), (c)(3), and (c)(4) of this AD.

(1) Prior to each flight, exercise the pitch trim system by accomplishing the following: "Command full NOSE DOWN, then full NOSE UP and re-position."

(2) Prior to further flight following accomplishment of the functional test required by paragraph (a) of this AD, revise the Limitations Section of the FAA-approved Airplane Flight Manual (AFM) to include the following information. This may be accomplished by inserting a copy of this AD in the AFM.

"1. Do not engage autopilot at an altitude below 1,000 feet AGL.

2. Monitor 8 CH annunciator for FLT CONT light.

3. Maximum flap setting to be used is Flap 20 degrees."

(3) Within 50 hours time-in-service after the effective date of this AD, perform an operational test to identify the unserviceable HSTA or horizontal stabilizer trim control unit (HSTCU) and replace it with a serviceable unit, in accordance with Bombardier Alert Service Bulletin A600-0645, dated January 11, 1995 (for Model CL-600-1A11 series airplanes), or A601-0443, dated January 11, 1995 (for Model CL-600-2A12 and CL-600-2B16 series airplanes), as applicable. Replacement of the unserviceable unit with a serviceable unit constitutes terminating action for the requirements of paragraphs (c)(1) and (c)(2) of this AD. Following such replacement, exercise of the pitch trim system may be discontinued and the limitation may be removed from the AFM.

(4) Thereafter at intervals not to exceed 100 hours time-in-service repeat the functional test of the HSTA brake as specified in paragraph (a) of this AD.

(d) For airplanes on which the stabilizer over-travel is shown to be more than 1 degree during the functional test required by paragraph (a) of this AD, accomplish the requirements of paragraphs (d)(1) and (d)(2) of this AD.

(1) Prior to further flight, perform an operational test to identify the unserviceable HSTA or HSTCU and replace it with a serviceable unit, prior to further flight, in accordance with Bombardier Alert Service Bulletin A600-0645, dated January 11, 1995 (for Model CL-600-1A11 series airplanes), or A601-0443, dated January 11, 1995 (for Model CL- 600-2A12 and CL-600-2B16 series airplanes),as applicable.

(2) Thereafter at intervals not to exceed 100 hours time-in-service repeat the functional test of the HSTA brake as specified in paragraph (a) in this AD.

(e) 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, New York Aircraft Certification Office (ACO), FAA, Engine and Propeller Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, New York ACO.

NOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the New York ACO.

(f) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.(g) The operational test and replacement shall be done in accordance with Bombardier Alert Service Bulletin A600-0645, dated January 11, 1995, or Bombardier Alert Service Bulletin A601-0443, dated January 11, 1995, as applicable. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Bombardier, Inc., Canadair, Aerospace Group, P.O. Box 6087, Station Centre-ville, Quebec H3C 3G9, Canada. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, New York Aircraft Certification Office, Engine and Propeller Directorate, 10 Fifth Street, Third Floor, Valley Stream, New York; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(h) This amendment becomes effective on September 12, 1995.

Transport Canada Aviation, which is the airworthiness authority for Canada, recently notified the FAA that an unsafe condition may exist on certain Bombardier Model CL-600-1A11 (CL-600), CL-600-2A12 (CL-601), and CL-600-2B16 (CL-601-3A and -3R) series airplanes. Transport Canada Aviation advises that it has received reports of overspeed annunciation of the pitch trim. Each time such annunciation occurred, the horizontal stabilizer trim actuator (HSTA) mechanical brake prevented uncommanded movement of the HSTA, i.e., HSTA runaway. Investigation has revealed that the reported overspeed annunciation of the pitch trim may be attributed to slippage of the no-back device on the HSTA. Further investigation revealed that the no-back device on the HSTA failed to operate properly at low temperatures, but operated properly at ambient temperatures above zero degrees centigrade. This condition, if not corrected, could result in uncommanded movement of the HSTA, which could adversely affect the controllability of the airplane.

Bombardier has issued Alert Service Bulletins A600-0645 (for Model CL-600-1A11 series airplanes), and A601-0443 (for Model CL-600-2A12 and CL-600-2B16 series airplanes), both dated January 11, 1995, which describe procedures for an operational test of the HSTA brake, and replacement of the HSTA or horizontal stabilizer trim control unit (HSTCU) with a serviceable unit. Transport Canada Aviation approved these service bulletins and issued Canadian airworthiness directive CF-95-02, dated February 28, 1995, in order to assure the continued airworthiness of these airplanes in Canada.

This airplane model is manufactured in Canada and is 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, Transport Canada Aviation has kept the FAA informed of the situation described above. The FAA has examined the findings of Transport Canada Aviation, 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.

Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design registered in the United States, this AD is being issued to prevent uncommanded movement of the HSTA. This AD requires repetitive functional testing of the HSTA brake for all airplanes. If certain conditions are found to exist during the functional tests, this AD also requires exercising of the pitch trim system, revising the Limitations Section of the FAA-approved Airplane Flight Manual (AFM), operational testing of the HSTA, and replacing the HSTA or HSTCU with a serviceable unit. Accomplishment of the replacement terminates the requirement to exercise the pitch trim system and revise the AFM.

Operational testing of the HSTA and replacement of the HSTA or HSTCU are required to be accomplished in accordance with the applicable alert service bulletin described previously.

As a result of recent communications with the Air Transport Association (ATA) of America, the FAA has learned that, in general, some operators may misunderstand the legal effect of AD's on airplanes that are identified in the applicability provision of the AD, but that have been altered or repaired in the area addressed by the AD. The FAA points out that all airplanes identified in the applicability provision of an AD are legally subject to the AD. If an airplane has been altered or repaired in the affected area in such a way as to affect compliance with the AD, the owner or operator is required to obtain FAA approval for an alternative method of compliance with the AD, in accordance with the paragraph of each AD that provides for such approvals. A note has been included in this rule to clarify this long-standing requirement.

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 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-139-AD." The postcard will be date stamped and returned to the commenter.

The regulations adopted herein will not have substantialdirect 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 ofit, 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, 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.

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