AD 94-04-17

This amendment adopts a new airworthiness directive (AD) that applies to Twin Commander Aircraft Corporation (Twin Commander) 500, 520, 560, 680, 681, 685, 690, 695, and 720 series airplanes. This action requires inspecting the flap system for cables with broken wires or pulleys with worn cable clips, replacing any damaged parts, and replacing the master pulley and cable with new parts of improved design. Reports of cable fatigue, particularly the master pulley cable, on several of the affected airplanes prompted this action. The actions specified by this AD are intended to prevent flap system failure caused by cable fatigue, which could result in loss of control of the airplane.

Final rule.

94-04-17 TWIN COMMANDER AIRCRAFT CORPORATION: Amendment 39-8837; Docket No. 92-CE-59-AD.

Applicability: Models 500, 500A, 500B, 500S, 500U, 520, 560, 560A, 560E, 560F, 680, 680E, 680F, 680FL, 680FL(P), 680FP, 680T, 680V, 680W, 681, 685, 690, 690A, 690B, 690C, 690D, 695, 695A, 695B, and 720 airplanes (all serial numbers), certificated in any category:

Compliance: Required within the next 50 hours time-in-service after the effective date of this AD, unless already accomplished.

To prevent flap system failure caused by cable fatigue, which could result in loss of control of the airplane, accomplish the following:

(a) Accomplish the following inspections and parts replacements (where applicable) of the flap system in accordance with the ACCOMPLISHMENT INSTRUCTIONS section of Twin Commander Service Bulletin (SB) No. 210, dated February 1, 1991.

(1) Rub each flap system cable over its length using a soft cotton cloth. Where the cotton snags, visually inspectthe cable for broken wires. Prior to further flight, replace any cable having a broken wire.

(2) Inspect the slave pulley groove width. If the groove is too narrow as specified in Part I, paragraph C, of the ACCOMPLISHMENT INSTRUCTIONS section of Twin Commander SB No. 210, prior to further flight, replace the slave pulley and slave pulley cable.

(3) Visually inspect the flap system for pulleys with worn cable clips or rubbing against the upper or lower support brackets. Prior to further flight, replace any damaged pulleys, brackets, or clips.

(b) Replace the master pulley and the master pulley cable with new parts of improved design in accordance with the ACCOMPLISHMENT INSTRUCTIONS section of Twin Commander SB No. 210, dated February 1, 1991. The applicable master pulley and master cable pulley part numbers are referenced in Table I of Twin Commander SB No. 210.

(c) Special flight permits may be issued in accordance with 14 CFR 21.197 and 21.199 to operate the airplane to a location where the requirements of this AD can be accomplished.

(d) An alternative method of compliance or adjustment of the compliance time that provides an equivalent level of safety may be approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Northwest Mountain Region, 1601 Lind Avenue S.W., Renton, Washington 98055-4056. The request shall be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO, FAA, Northwest Mountain Region.

NOTE: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO, FAA, Northwest Mountain Region.

(e) The inspection and replacement required by this AD shall be done in accordance with Twin Commander Service Bulletin No. 210, dated February 1, 1991. This incorporation by reference was approved by the Director of the Federal Register in accordance with5 U.S.C. 552(a) and 1 CFR Part 51. Copies may be obtained from the Twin Commander Aircraft Corporation, 19003 59th Drive, NE., Arlington, Washington 98223. 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.

(f) This amendment becomes effective on April 15, 1994.

A proposal to amend part 39 of the Federal Aviation Regulations to include an AD that would apply to certain Twin Commander 500, 520, 560, 680, 681, 685, 690, 695, and 720 series airplanes was published in the Federal Register on July 19, 1993 (58 FR 38540). The action proposed to require inspecting the flap system for cables with broken wires and pulleys with worn clips, replacing any damaged parts, and replacing the master pulley with a new part of improved design. The proposed actions would be accomplished in accordance with Twin Commander Service Bulletin No. 210, dated February 1, 1991.

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

One commenter, the Twin Commander Aircraft Corporation, supports the proposed rule, and recommends wording the proposed AD to more closely coincide with Service Bulletin 210, dated February 1, 1991. The FAA concurs and has reworded the proposal accordingly. This change does not add any additional burden upon U.S. owners/operators of the affected airplanes than was originally proposed.

The other commenter states that a parts availability problem may occur if owners/operators of the affected airplanes find as many damaged pulleys in the cable system as this owner/operator did on a Model 690B airplane. This commenter feels that there is not sufficient parts inventory to coincide with the 50-hour time-in-service (TIS) compliance time, and recommends changing the compliance time to 12 months. The FAA does not concur. Twin Commander has assured the FAA that there will be adequate parts available for all required repairs. In addition, if a temporary delay in parts availability should occur, then an owner/operator could request an extension of the compliance time through instructions specified in paragraph (d) of the proposed AD. The proposed AD is unchanged as a result ofthis comment.

After careful review of all available information, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed except for the wording changes referenced above and minor editorial corrections. The FAA has determined that these minor changes and corrections will not change the meaning of the AD nor add any additional burden upon the public than was already proposed.

The FAA estimates that 1,860 airplanes in the U.S. registry will be affected by this AD, that it will take approximately 25 workhours per airplane to accomplish the required action, and that the average labor rate is approximately $55 an hour. Parts cost approximately $600 per airplane. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $3,673,500. This figure is based upon the assumption that none of the affected airplane operators have accomplished the required actions.

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.

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 copy of the final 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, Incorporation by reference, Safety.

Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 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.

Section 39.13 - [AMENDED]
2. Section 39.13 is amended by adding the following new AD to read as follows: