Airworthiness Directives; Canadair Model CL-600-2B19 (Regional Jet) Series Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 93-NM-213-AD]

Airworthiness Directives; Canadair Model CL-600-2B19 (Regional

Jet) Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness

directive (AD) that is applicable to certain Canadair Model CL-600-2B19

(Regional Jet) series airplanes. This proposal would require

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 attitude and heading

reference system (AHRS). This proposal is prompted by a report that the

AHRS could send conflicting input to the stall protection computer

(SPC) on the airplane. The actions specified by the proposed AD are

intended to prevent the loss of stall warning protection on the

airplanes.

DATES: Comments must be received by April 29, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Transport Airplane Directorate, ANM-103,

Attention: Rules Docket No. 93-NM-213-AD, 1601 Lind Avenue, SW.,

Renton, Washington 98055-4056. Comments may be inspected at this

location between 9 a.m. and 3 p.m., Monday through Friday, except

Federal holidays.

The service information referenced in the proposed rule may be

obtained from Bombardier, Inc., Canadair, Aerospace Group, P.O. Box

6087, Station A, Montreal, Quebec H3C 3G9, Canada. This information may

be examined 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.

FOR FURTHER INFORMATION CONTACT: Peter Cuneo, Electrical Engineer,

Systems and Equipment Branch, ANE-173, FAA, Engine and Propeller

Directorate, New York Aircraft Certification Office, 181 South Franklin

Avenue, room 202, Valley Stream, New York 11581; telephone (516) 791-

6427; fax (516) 791-9024.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the

proposed 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 above. All

communications received on or before the closing date for comments,

specified above, will be considered before taking action on the

proposed rule. The proposals contained in this notice may be changed in

light of the comments received.

-Comments are specifically invited on the overall regulatory,

economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with

the substance of this proposal 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 Number 93-NM-213-AD.'' The postcard will be date

stamped and returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request

to the FAA, Transport Airplane Directorate, ANM-103, Attention: Rules

Docket No. 93-NM-213-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

-Transport Canada Aviation, which is the airworthiness authority

for Canada, recently notified the FAA that an unsafe condition may

exist on certain Canadair Model CL-600-2B19 series airplanes. Transport

Canada advises that the attitude and heading reference system (AHRS)

could send conflicting input to the stall protection computer (SPC) on

these airplanes. When the AHRS sends input to the SPC, the left- and

right-hand channels on the SPC receive and compare that input. The SPC

has a built-in feature that compares lateral acceleration from these

channels. When the SPC recognizes unequal lateral acceleration signals

of 0.03g or higher, it will inhibit the stall horn, light, and stick

push command, and an ``SPS FAILURE'' caution message will display on

the primary flight display. Due to a build-up effect of AHRS

tolerances, these unequal signals may be detected within the SPC at a

roll rate within the normal flight envelope. This condition, if not

corrected, could result in the loss of stall warning protection on the

airplane.

Bombardier, Inc., has issued Regional Jet Canadair Alert Service

Bulletin S.B. A601R-34-028, Revision `A,' dated October 22, 1993, that

describes procedures for modification of the stall protection system

(SPS) input wiring. The modification involves removing the right

channel input wires from the connection to the SPC, capping and stowing

the removed wires, installing splices from the left-hand channel input

to the right-hand channel connection of the SPC, and installing a

ground jumper wire. Accomplishment of these wiring changes will prevent

a build-up effect of AHRS tolerances and unequal signals between the

left- and right-hand SPC channels. Transport Canada Aviation classified

this service bulletin as mandatory and issued Canadian Airworthiness

Directive CF-93-27, dated October 26, 1993, 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 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, the proposed AD would require modification of the

SPS input wiring. The modification would be required to be accomplished

in accordance with the alert service bulletin described previously.

-This proposed AD would also require revising 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. Finally, this proposed AD would require

modification of the AHRS to restore the dual AHRS inputs to the SPC.

This modification would be required to be accomplished in accordance

with a method approved by the FAA.

-It should be noted that Canadian AD CF-93-27 requires that the

flight crew be advised of the possibility of an inadvertent inhibition

of the stall horn, light, and stick push command at a roll rate within

the normal flight envelope, and that an ``SPS FAILURE'' caution message

will be displayed on the primary flight display. The Canadian AD

requires that when such a message is displayed, appropriate abnormal

procedures in the AFM should be followed. However, the FAA's position

in this regard is that it is not necessary to include a requirement in

this proposed AD to direct the flight crew to follow existing AFM

procedures.

-The FAA estimates that 9 airplanes of U.S. registry would be

affected by this proposed AD, that it would take approximately 2 work

hours per airplane to accomplish the proposed actions, and that the

average labor rate is $55 per work hour. The cost for required parts

would be minimal. Based on these figures, the total cost impact of the

proposed AD on U.S. operators is estimated to be $990, or $110 per

airplane. This total cost figure assumes that no operator has yet

accomplished the proposed requirements of this AD action.

-The regulations proposed herein would 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

proposal would not have sufficient federalism implications to warrant

the preparation of a Federalism Assessment.

-For the reasons discussed above, I certify that this proposed

regulation (1) is not a ``significant regulatory action'' under

Executive Order 12866; (2) is not a ``significant rule'' under the DOT

Regulatory Policies and Procedures (44 FR 11034, February 26, 1979);

and (3) if promulgated, 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 copy of the draft

regulatory evaluation prepared for this action is contained in the

Rules Docket. A copy of it may be obtained by contacting the Rules

Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

-Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration proposes to amend 14

CFR part 39 of the Federal Aviation Regulations 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.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

Canadair Limited: Docket 93-NM-213-AD.

Applicability: Model CL-600-2B19 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 must be 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

Check that no annunciations are displayed on EFIS

EFIS slip/skid indications--Normal

Indications 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.

EFIS--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 6 months after the effective date of this AD, modify

the attitude and heading reference system (AHRS) to restore the dual

AHRS inputs to the stall protection computer (SPC), in accordance

with a method approved by the Manager, New York Aircraft

Certification Office (ACO), FAA, Engine and Propeller Directorate.

(d) 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, 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: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the New York ACO.

(e) Special flight permits may be issued in accordance with

Federal Aviation Regulations (FAR) 21.197 and 21.199 to operate the

airplane to a location where the requirements of this AD can be

accomplished.

Issued in Renton, Washington, on February 28, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-4955 Filed 3-3-94; 8:45 am]

BILLING CODE 4910-13-U