AD 96-24-08 ACTIVE

This amendment adopts a new airworthiness directive (AD) that applies to certain Air Tractor, Inc. (Air Tractor) Models AT-250, AT-300, AT-301, AT-302, AT-400, AT-400A, AT-401, AT-402, AT-501, and AT-502 airplanes that are equipped with a Gerdes part number (P/N) A-850-5 or Cleveland P/N 60-9 parking brake valve. This action requires replacing the parking brake valve with a Scott P/N 4500A-2 parking brake valve. This AD results from several reports of the parking brake valve inadvertently slipping to the "PARK" position during flight, which causes constant pressure on the brakes. When the pilot applies the brake upon landing, this pressure causes the airplane to overturn. The actions specified by this AD are intended to prevent the airplane from overturning because of extreme pressure applied to the brake if the parking brake valve inadvertently slips to the "PARK" position during flight.

Final rule; request for comments.

96-24-08 AIR TRACTOR, INC.: Amendment 39-9833; Docket No. 96-CE-49-AD.

Applicability: The following airplane models and serial numbers, certificated in any category, that are equipped with a Gerdes part number (P/N) A-850-5 or Cleveland P/N 60-9 parking brake valve:

Model
Serial Numbers
AT-250
250-0491
AT-300
300-0001 through 300-0708
AT-301
301-0001 through 301-0708
AT-302
302-0001 through 302-0708
AT-400
400-0001 through 400-0708
AT-400A
400A-0001 through 400A-0708
AT-401
401-0001 through 401-0708
AT-402
402-0001 through 402-0708
AT-501
501-0001 through 501-0036
AT-502
502-0001 through 502-0036

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 request approval for an alternative method of compliance in accordance with paragraph (c) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required within the next 75 hours time-in-service after the effective date of this AD, unless already accomplished.

To prevent the airplane from overturning because of extreme pressure applied to the brake if the parking brake valve inadvertently slips to the "PARK" position during flight, accomplish the following:

(a) Replace the Gerdes P/N A-850-5 or Cleveland P/N 60-9 parking brake valve with a Scott P/N 4500A-2 parking brake valve. Accomplish this replacement in accordance with Air Tractor Service Letter #76 Instructions, as referenced in Snow Engineering Co. ServiceLetter #76, dated December 12, 1988.

(b) 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.

(c) An alternative method of compliance or adjustment of the compliance time that provides an equivalent level of safety may be approved by the Manager, FAA, Aircraft Certification Office, 2601 Meacham Boulevard, Fort Worth, Texas 76193-0150. The request shall be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Fort Worth ACO.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Fort Worth ACO.

(d) The replacement required by this AD shall be done in accordance with Air Tractor Service Letter #76 Instructions, as referenced in Snow Engineering Co. Service Letter #76, dated December 12, 1988. 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 Air Tractor Inc., P.O. Box 485, Olney, Texas 76374. Copies may be inspected at the FAA, Central Region, Office of the Assistant Chief Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri, or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(e) This amendment becomes effective on December 23, 1996.

Events Leading to This AD
The FAA has received several reports of the parking brake valve inadvertently slipping to the "PARK" position during flight on Air Tractor Models AT-250, AT-300, AT-301, AT-302, AT-400, AT-400A, AT-401, AT-402, AT-501, and AT-502 airplanes. When the parking brake is in the "PARK" position, a constant pressure is applied to the brakes, which cannot be relieved or reduced when the pilot removes pressure from the brake pedals. This pressure builds to the point that when the pilot applies the brake upon landing to slow the airplane, the airplane overturns.

The airplanes in the incidents described above were equipped with Gerdes part number (P/N) A-850-5 or Cleveland P/N 60-9 parking brake valves. The FAA has determined that these Gerdes or Cleveland parking brake valves should be replaced with Scott parking brake valves, P/N 4500A-2, on certain Air Tractor Models AT-250, AT-300, AT-301, AT-302, AT-400, AT-400A, AT-401, AT-402,AT-501, and AT-502 airplanes.

Applicable Service Information
Air Tractor has issued Snow Engineering Co. Service Letter #76, dated December 12, 1988, which specifies replacing Gerdes part number A-850-5 and Cleveland P/N 60-9 parking brake valves with Scott parking brake valves, P/N 4500A-2. Air Tractor Service Letter #76 Instructions specify procedures for accomplishing this parking brake valve replacement.

The FAA's Determination
After examining the circumstances and reviewing all available information related to the incidents described above, including the referenced service information, the FAA has determined that AD action should be taken to prevent the airplane from overturning because of extreme pressure applied to the brake if the parking brake valve inadvertently slips to the "PARK" position during flight.

Explanation of the Provisions of This AD
Since an unsafe condition has been identified that is likely to exist or develop in other Air Tractor Models AT-250,AT-300, AT-301, AT-302, AT-400, AT-400A, AT-401, AT-402, AT-501, and AT-502 airplanes of the same type design that are equipped with a Gerdes (P/N) A-850-5 or Cleveland P/N 60-9 parking brake valve, the FAA is implementing AD action. This AD requires replacing these Gerdes or Cleveland parking brake valves with a Scott P/N 4500A-2 parking brake valve. Accomplishment of this replacement is in accordance with Air Tractor Service Letter #76 Instructions, as referenced in Snow Engineering Co. Service Letter #76, dated December 12, 1988.

Since a situation exists (possibility of the airplane overturning during 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 forexamination 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. 96-CE-49 -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 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), 40113, 44701.

Section 39.13 - [AMENDED]
2. Section 39.13 is amended by adding a new airworthiness directive (AD) to read as follows:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Central Region, Office of the Assistant Chief Counsel, Attention: Rules Docket 96-CE-49-AD, Room 1558, 601 E. 12th Street, Kansas City, Missouri 64106.

Service information that applies to this AD may be obtained from Air Tractor Inc., P.O. Box 485, Olney, Texas 76374; telephone (817) 564-5616; facsimile (817) 564-2348. This information may also be examined at the Federal Aviation Administration (FAA), Central Region, Office of the Assistant Chief Counsel, Attention: Rules Docket 96-CE-49-AD, Room 1558, 601 E. 12th Street, Kansas City, Missouri 64106; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Mr. Werner Koch, Aerospace Engineer, FAA, Aircraft Certification Office, 2601 Meacham Boulevard, Fort Worth, Texas 76193-0150; telephone (817) 222-5133; facsimile (817) 222-5960.