AD 97-20-12 Airworthiness Directives; McDonnell Douglas Helicopter Systems Model MD-900 Helicopters

Models named: MD-900. Read the applicability below — it usually turns on serial or part numbers too.

Model MD-900 helicopters, certificated in any category. Note 1: This AD applies to each helicopter 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 helicopters that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must use the authority provided in paragraph (h) to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition, or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any helicopter from the applicability of this AD.

Required before further flight, unless accomplished previously. To prevent possible heat accumulation and resulting damage to the main rotor swashplate bearing (bearing) caused by the bearing races rotating relative to the bearing seat, which could result in degraded helicopter response to pilot control input and possible loss of control of the helicopter, accomplish the following: (a) Disconnect the lower end of the main rotor pitch links. Disconnecting the drive link may make the inspection easier. (b) Cut the safety wire and remove the inner and outer labyrinth seals, part number (P/N) 900C2010194-101 and P/N 900C201190-101, respectively, and the inner and outer bearing retaining rings. (c) Inspect the bearing, part number (P/N) 900C3010100-101, to determine if it has one of the following serial numbers (S/N): S/N 059150-E0019, S/N 059150-E0020, S/N 059150-E0021, S/N 059150-E0022, S/N 059150-E0023, S/N 059150-E0024, S/N 059150-E0025, S/N 059150- E0026, S/N 059150-E0027, S/N 059150-E0028, S/N 059150-E0029, or S/N 059150-E0030. Note 2: S/N's similar to those above were produced without the character ``E'' in the number. This AD is only concerned with those that contain the character ``E''. (d) Enter into the helicopter Log Book the bearing S/N. (e) If a bearing having one of the S/N's stated in paragraph (c) of this AD is installed on the helicopter, remove the bearing and replace it with an airworthy bearing prior to further flight. (f) Prior to the installation of a swashplate assembly, inspect the bearing in accordance with the requirements of this AD. (g) Report the results of all inspections required by this AD within 72 hours to the Manager, Los Angeles Aircraft Certification Office, 3960 Paramount Blvd., Lakewood, California 90712. Reporting requirements have been approved by the Office of Management and Budget and assigned OMB control number 2120-0056. (h) 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 3: 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. (i) 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 helicopter to a location where the requirements of this AD can be accomplished. (j) This amendment becomes effective on November 6, 1997. Issued in Fort Worth, Texas, on September 24, 1997. Eric Bries, Acting Manager, Rotorcraft Directorate, Aircraft Certification Service. [FR Doc. 97-25970 Filed 10-1-97; 8:45 am] BILLING CODE 4910-13-U