The Civil Aviation Authority (CAA), which is the airworthiness authority for the United Kingdom, notified the FAA that an unsafe condition may exist on certain Short Brothers Model SD3- 60 series airplanes. The CAA advises that balance weight brackets have been found cracked on both the left and right elevator trim tabs. Investigation revealed that the cracked brackets do not conform to the approved design standard. This nonconformity substantially reduces the expected fatigue life of the brackets, causing premature cracking and failure. This condition, if not corrected, could lead to loss of the balance weight. This could result in incorrect trim during takeoff and landing, and reduced controllability of the airplane.
Other Relevant Rulemaking
We have previously issued AD 2004-13-08, amendment 39-13690 (69 FR 38813, June 29, 2004). That AD applies to all Short Brothers Model SD3- 60 series airplanes. That AD requires repetitive inspections for cracking of the welded joints of the balance weight brackets for the elevator trim tabs, and replacement of any cracked bracket with a new or serviceable bracket. That AD provides for eventual replacement of uncracked brackets as terminating action for the repetitive inspections.
AD 2004-13-08 refers to Short Brothers Service Bulletin SD360-55- 20, dated June 26, 2003, as the applicable source of service information for the required actions. CAA notified us that operators may have installed the defective balance weight brackets that are the subject of this new AD while accomplishing Short Brothers Service Bulletin SD360-55-20.
Relevant Service Information
Short Brothers has issued Alert Service Bulletin SD360-55-A21, dated December 16, 2004. Short Brothers Alert Service Bulletin SD360- 55-A21 describes procedures for performing repetitive dye penetrant inspections for cracking of the subject balance weight brackets. Short Brothers Alert Service Bulletin SD360-55-A21 also describes procedures for replacing balance weight brackets with new balance weight brackets that conform to the approved design standard, which is mandatory for any cracked balance weight bracket. Short Brothers Alert Service Bulletin SD360-55-A21 also describes procedures for refitting balance weights, covers, and trim tabs following any inspection or replacement. Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition. The CAA mandated Short Brothers Alert Service Bulletin SD360-55-A21 and issued British emergency airworthiness directive G-2004-0032, dated December 30, 2004, to ensure the continued airworthiness of these airplanes in the United Kingdom.
FAA's Determination and Requirements of This AD
This airplane model is manufactured in the United Kingdom and is type certificated for operation in the United States under the provisions of Sec. 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, the CAA has kept the FAA informed of the situation described above. We have examined the CAA's findings, evaluated all pertinent information, and determined that we need to issue an AD for products of this type design that are certificated for operation in the United States.
Therefore, we are issuing this AD to prevent failure of the balance weight bracket for the elevator trim tab, which could cause loss of the balance weight. This could result in incorrect trim during takeoff and landing, and reduced controllability of the airplane. This AD requires, for certain airplanes, accomplishing the actions specified in the service information described previously, except as discussed under "Differences Between the AD and the Service Bulletin."
Differences Between the AD and the Service Bulletin
The service bulletin specifies that operators may contact the manufacturer for disposition of certain conditions when refitting balance weights; for those conditions, this proposed AD would require operators to obtain further instructions from the FAA or the CAA (or its delegated agent).
The service bulletin specifies that subject parts must be returned to Short Brothers. This AD does not require that action.
Differences Between the AD and the British Emergency Airworthiness Directive
British emergency airworthiness directive G-2004-0032 requires replacing all subject balance weight brackets with new or reworked brackets that conform to the approved design standard. The British emergency airworthiness directive recommends that this replacement be accomplished before the accumulation of 1,750 flight hours since installation of the balance weight bracket. This AD provides for replacement of uncracked subject balance weight brackets as an option that, if accomplished, would constitute terminating action for the requirements of this AD.
British emergency airworthiness directive G-2004-0032 applies to Model SD3-60 series airplanes on which subject balance weight brackets were installed in accordance with the original issue of Short Brothers Service Bulletin SD360-55-20. This AD applies to all Model SD3-60 series airplanes. We have determined it is necessary to include all Model SD3-60 series airplanes in the applicability of this AD to ensure that no subject balance weight bracket will be installed in the future on any Model SD3-60 series airplane.
Interim Action
We consider this AD interim action. We are currently considering requiring the replacement of all subject balance weight brackets with new or reworked brackets that conform to the approved design standard, which would constitute terminating action for the repetitive inspections required by this AD. However, the planned compliance time for the replacement would allow enough time to provide notice and opportunity for prior public comment on the merits of the modification.
FAA'sDetermination of the Effective Date
An unsafe condition exists that requires the immediate adoption of this AD; therefore, providing notice and opportunity for public comment before the AD is issued is impracticable, and good cause exists to make this AD effective in less than 30 days.
Comments Invited
This AD is a final rule that involves requirements that affect flight safety and was not preceded by notice and an opportunity for public comment; however, we invite you to submit any relevant written data, views, or arguments regarding this AD. Send your comments to an address listed under ADDRESSES. Include "Docket No. FAA-2005-20108; Directorate Identifier 2005-NM-006-AD" at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the AD. We will consider all comments received by the closing date and may amend the AD in light of those comments.
We will post all comments we receive, without change, to http://dms.dot.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this AD. Using the search function of our docket Web site, anyone can find and read the comments in any of our dockets, including the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You can review the DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you can visit http://dms.dot.gov.
Authority for this Rulemaking
Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, Section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.
We are issuing this rulemaking under the authority described in Subtitle VII,Part A, Subpart III, Section 44701, "General requirements." Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.
Regulatory Findings
We have determined that this AD will not have federalism implications under Executive Order 13132. This AD will not have a substantial direct effect 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.
For the reasons discussed above, I certify that the 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. 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.
We prepared a regulatory evaluation of the estimated costs to comply with this AD. See the ADDRESSES section for a location to examine the regulatory evaluation.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, under the authority delegated to me by the Administrator, the FAA amends 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. 106(g), 40113, 44701.
39.13 [Amended]
2. The FAA amends 39.13 by adding the following new airworthiness directive (AD):