AD 99-13-09 Airworthiness Directives; MD Helicopters, Inc (MDHI) Model 369D and E Helicopters

Models named: 369D, E. Read the applicability below — it usually turns on serial or part numbers too.

Model 369D and E helicopters, with four-bladed tail rotor fork (fork) assemblies, part number (P/N) 369D21701-21, 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 (d) 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 as indicated, unless accomplished previously. To prevent failure of the fork assembly, P/N 369D21701-21, which can result in loss of a tail rotor blade and subsequent loss of control of the helicopter, accomplish the following: (a) Before further flight, inspect each fork assembly, P/N 369D21701-21, for the presence of ridges on the arms. See Figure 1, sheets 1 and 2. Note 2: MD Helicopters, Inc., Service Bulletin SB369D-198, SB369E-092, dated May 10, 1999, pertains to the subject of this AD. (1) If ridges are found, no further action is required by this AD. (2) If no ridges are found, chemically remove paint from the machined areas, inspect the fork assembly for a crack using the dye- penetrant procedure of MIL-STD-6866 or ASTM-E1417, and conduct a visual inspection using a 10X or higher magnifying glass. (See Figure 1, sheets 1 and 2.) Replace a cracked fork assembly with an airworthy fork assembly. A fork assembly without ridges, P/N 369D21701-21, may not be installed. Note 3: The fork assembly is titanium, which requires dwell times for the dye-penetrant inspection that are appropriate for titanium. (b) Thereafter, at intervals not to exceed 50 hours time-in- service (TIS), visually inspect each fork assembly without ridges, P/N 369D21701-21, for a crack using a 10X or higher magnifying glass. (See Figure 1, sheets 1 and 2.) If a crack is found, replace the cracked fork assembly with an airworthy fork assembly. A fork assembly without ridges, P/N 369D21701-21, may not be installed. (c) Replacing an unairworthy fork assembly with an airworthy fork assembly other than P/N 369D21701-21 without ridges constitutes terminating action for this AD. (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, Los Angeles Aircraft Certification Office, FAA. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Los Angeles Aircraft Certification Office. Note 4: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Los Angeles Aircraft Certification Office. BILLING CODE 4910-13-P [[Page 38819]] [GRAPHIC] [TIFF OMITTED] TR20JY99.006 [[Page 38820]] [GRAPHIC] [TIFF OMITTED] TR20JY99.007 (e) Special flight permits will not be issued. (f) This amendment becomes effective on August 4, 1999, to all persons except those persons to whom it was made immediately effective by Priority Letter AD 99-13-09, issued June 16, 1999, which contained the requirements of this amendment. Issued in Fort Worth, Texas, on July 13, 1999. Henry A. Armstrong, Manager, Rotorcraft Directorate, Aircraft Certification Service. [FR Doc. 99-18367 Filed 7-19-99; 8:45 am] BILLING CODE 4910-13-C