AD 94-22-06

This amendment adopts a new airworthiness directive (AD), applicable to certain Bombardier Model CL-600-2B19 series airplanes, that requires modification of the stall protection system (SPS) input wiring; a revision to the FAA-approved Airplane Flight Manual (AFM) to specify that a pre-flight check of the slip/skid indications must be conducted prior to engine start; and modification of the stall protection computer (SPC) to accept restored dual attitude and heading reference system (AHRS) input. This amendment is prompted by a report that the AHRS could send conflicting input to the SPC on the airplane. The actions specified by this AD are intended to prevent the loss of stall warning protection on the airplanes.

Final rule

94-22-06 BOMBARDIER, INC. (FORMERLY CANADAIR): Amendment 39-9055. Docket 93-NM-213-AD.
Applicability: Model CL-600-2B19 (Regional Jet Series 100) series airplanes; serial numbers 7003 through 7026, inclusive; certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent the loss of stall warning protection on the airplane, accomplish the following:

(a) Within 30 days after the effective date of this AD, modify the stall protection system (SPS) input wiring in accordance with Canadair Regional Jet Alert Service Bulletin A601R-34-028, Revision 'A,' dated October 22, 1993.

(b) Prior to further flight after accomplishment of the modification required by paragraph (a) of this AD, revise the Normal Procedures section of the FAA-approved Airplane Flight Manual (AFM) by inserting the following into the AFM as facing page 04-20-13 to advise the flight crew that a pre-flight check of the slip/skid indications mustbe accomplished as a "Before Start" item. This may be accomplished by inserting a copy of this AD into the AFM.

"Change step (4) within paragraph E, Before Start, to read as follows:

(4) EFIS...................................................................Checked and Set
oCheck that no annunciations are displayed on EFIS
oEFIS slip/skid indications................................Normal
oIndications of a one-half (1/2) symbol width lateral deviation
should be interpreted as an AHRS failure.

NOTE

One-half (1/2) symbol width displacement corresponds to
approximately one-half displacement on a conventional inclinometer.
oEFIS.................................................................Set for Departure"

NOTE 1: Insertion of Canadair Regional Jet Airplane Flight Manual CSP A-012, Temporary Revision RJ/26, dated October 21, 1993, in the Normal Procedures section of the AFM is an acceptable method of compliance with the requirements of paragraph (b) of this AD.

(c) Within 9 months after the effective date of this AD, modify the stall protection computer (SPC) to accept restored dual attitude and heading reference system (AHRS) input, in accordance with a method approved by the Manager, New York Aircraft Certification Office (ACO), FAA, Engine and Propeller Directorate.

(d) Modification of the SPC in accordance with paragraph (c) of this AD constitutes terminating action for the AFM revision required by paragraph (b) of this AD. Following accomplishment of that modification, the AFM revision may be removed from the FAA-approved AFM.

(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 ACO. 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 2: 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 modification shall be done in accordance with Canadair Regional Jet Alert Service Bulletin A601R-34-028, Revision 'A,' dated October 22, 1993. 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, Montreal, Quebec H3C 3G9, Canada. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Engine and Propeller Directorate, New York Aircraft Certification Office, 181 South Franklin Avenue, 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 December 12, 1994.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Bombardier Model CL-600-2B19 (Regional Jet Series 100) series airplanes was published in the Federal Register on March 4, 1994 (59 FR 10340). That action proposed to require modification of the stall protection system (SPS) input wiring; a revision to the Normal Procedures section of the FAA-approved Airplane Flight Manual (AFM) to specify that a pre-flight check of the slip/skid indications must be conducted prior to engine start; and modification of the attitude and heading reference system (AHRS) to restore the dual AHRS inputs to the SPC.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

One commenter requests that the FAA revise the final rule to indicate that it is not the AHRS that will be modified, but the stall protection computer (SPC). The FAA concurs, and has revised the preamble and paragraph (c) of the final rule to clarify its intent that the SPC be modified to restore the dual AHRS inputs to the SPC.

The commenter also requests that the proposed compliance time of 6 months for modification of the SPC, as specified in paragraph (c) of the proposed rule, be extended due to the complex nature of the SPC modification and the need to modify additional equipment to support the SPC change. The commenter proposes a target date of April 4, 1995, for accomplishment of the modification. As justification for this suggested extension, the commenter states that the SPC software will detect a loss of AHRS input to both SPC channels, and a "STALL FAIL" amber message will be displayed; additionally, the AFM defines abnormal procedures to be followed when loss of the SPS occurs. The commenter adds that there are several components in the SPS that can fail and cause the loss of stall protection on any one flight. The commenter believes that the loss of AHRS input is no worse than, and the system is just as reliable as, a system with two independent AHRS inputs.

The FAA does not concur. Compliance times for AD's are normally based on a parameter related to failure of a particular component. The FAA has determined that there is no apparent direct relationship between the transmittal of conflicting input from the AHRS to the SPC (and subsequent loss of stall warning protection on the airplane) and a calendar date. Therefore, the FAA does not consider that the compliance time for modification of the SPC should be expressed in terms of a calendar date, as suggested by the commenter.

Further, in developing a compliance time for this requirement of the rule, the FAA considered not only the safety implications, but the availability of required parts and the practical aspect of installing the required modification within a maximum intervalof time allowable for all affected airplanes to continue to operate without compromising safety. In light of these items, the FAA finds that a compliance time of 6 months is appropriate. (Additionally, based on the effective date of this final rule, the compliance time for operators to perform the modification will fall close to the calendar date requested by the commenter.)

A new paragraph (d) has been added to the final rule to clarify the FAA's intent that modification of the SPC constitutes terminating action for the AFM revision required by paragraph (b) of this AD. Therefore, once the SPC is modified, the AFM revision may be removed from the AFM.

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increasethe scope of the AD.

The FAA estimates that 9 airplanes of U.S. registry will be affected by this AD, that it will take approximately 2 work hours per airplane to accomplish the required actions, and that the average labor rate is $55 per work hour. The cost for required parts will be minimal. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $990, or $110 per airplane.

The total cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted.

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 thatthis final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it 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 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.

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