AD 99-23-23 Airworthiness Directives; Bell Helicopter Textron, Inc. Model 412, 412EP and 412CF Helicopters

Models named: 412 or 412EP. Read the applicability below — it usually turns on serial or part numbers too.

Model 412 or 412EP helicopters, serial numbers (S/N) 33001 through 33213, 34001 through 34036, and 36001 through 36204, or Model 412CF helicopter, S/N 46400 through 46499, with main rotor yoke assembly (yoke), part number 412-010-101-123 or -127, installed, certificated in any category. Note 1: This AD applies to each helicopter identified in the preceding applicability provision, regardless of whether it has been otherwise modified, altered, or repaired in the area subject to the requirements of this AD. For helicopters 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 (b) 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.

Required within 10 hours time-in-service (TIS) for a yoke with 4,500 or more hours TIS or required within 90 days for a yoke with less than 4,500 hours TIS but prior to the accumulation of 4,500 hours TIS, unless accomplished previously. To prevent a fatigue failure of a yoke, loss of a main rotor blade, and subsequent loss of control of the helicopter, accomplish the following: (a) Inspect and measure each yoke in accordance with the Accomplishment Instructions, paragraphs 1 through 6, of Bell Helicopter Textron, Inc. (BHTI), Alert Service Bulletin (ASB) 412- 98-93, applicable to the Model 412 and 412EP helicopters, or BHTI ASB 412CF-98-5, applicable to the Model 412CF helicopters, both dated March 2, 1998. If any measurement for a yoke is less than 0.478-inch thickness, add 500 hours to the TIS indicated on the component history card or equivalent record. (b) 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, Rotorcraft Certification Office, FAA, Rotorcraft Directorate. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Rotorcraft Certification Office. Note 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Rotorcraft Certification Office. (c) Special flight permits may be issued in accordance with Secs. 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the helicopter to a location where the requirements of this AD can be accomplished. (d) The inspection shall be done in accordance with Bell Helicopter Textron, Inc. Alert Service Bulletins 412-98-93 or 412CF- 98-5, both dated March 2, 1998, as applicable. This incorportion 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 Bell Helicopter Textron, Inc., P.O. Box 482, Fort Worth, Texas 76101, telephone (817) 280-3391, fax (817) 280-6466. Copies may be inspected at the FAA, Office of the Regional Counsel, Southwest Region, 2601 Meacham Blvd., Room 663, Fort Worth, Texas; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. (e) This amendment becomes effective on December 1, 1999. Issued in Fort Worth, Texas, on November 4, 1999. Henry A. Armstrong, Manager, Rotorcraft Directorate, Aircraft Certification Service. [FR Doc. 99-29612 Filed 11-15-99; 8:45 am] BILLING CODE 4910-13-P