AD 98-26-06 Airworthiness Directives; Schweizer Aircraft Corporation Model 269D Helicopters

Makes named: schweizer. Models named: 269D. Read the applicability below — it usually turns on serial or part numbers too.

Model 269D helicopters with a large diameter main rotor hub (hub), part number (P/N) 269A1002-11, and main rotor drive shaft (shaft), P/N 269A5305-139, -143, -145, or -147, 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 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 (c) 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 as indicated, unless accomplished previously. To prevent failure of the shaft and subsequent loss of control of the helicopter, accomplish the following: (a) Prior to 200 hours time-in-service (TIS) since the assembly of the hub and a shaft having zero hours TIS, and thereafter at intervals not to exceed 100 hours TIS, (1) Remove the shaft from the power train system. (2) Clean and inspect the shaft for a crack in the area of the six hub attach bolt (bolt) holes using a 10-power or higher magnifying glass and bright light. (3) If no crack is found, inspect the shaft using a direct or indirect magnetic particle inspection method in accordance with ASTM Standard No. E1444 as follows: (i) For direct magnetization, use an AC, DC, or AC/DC wet continuous method with fluorescent or nonfluorescent particles. (A) Circular (Head Shot)--1,100 amperes Look for a longitudinal crack. (B) Longitudinal (Coil Shot)--Because of variations in coil design, only the length-to-diameter ratio based on effective diameter and inspection region is provided. Effective diameter--1.279 inches, Length--6.00 inches, L/D Ratio--5, Look for a circumferential crack. (C) Demagnetize and clean the inspection areas with solvent to remove residual particles. (ii) For indirect magnetization, use an AC electromagnetic yoke (Magnaflux product No. Y-6 or equivalent). Set the spacing and the angle to suit the external diameter of the shaft. (A) Magnetize each of the six hole areas by applying the AC electromagnetic yoke (yoke) circumferentially across the hole. (B) During each magnetization, apply dry color contrasting particles to the inspection area and look for a circumferential crack propagating from any hole. (C) Demagnetize and repeat the inspections with the poles of the yoke positioned longitudinally across each hole group looking for a circumferential crack. (D) Demagnetize and clean the inspection areas with solvent to remove residual particles. (iii) If no crack is found as a result of the magnetic particle inspection, reassemble the hub and shaft. Note 2: Procedures in Model 269D Handbook of Maintenance Instructions (HMI) revised on June 12, 1998, include installing a three-piece retention fitting, applying a higher torque to each bolt, assembling with no lubricant, and applying zinc chromate primer between the hub and the shaft. (4) If a crack is found, replace the shaft with an airworthy shaft. (b) At intervals not to exceed 50 hours TIS after accomplishing paragraph (a), (1) Unsafety and clean the exterior of the bolts. (2) Unsafety and loosen the droop stop nut. (3) Apply 390 in-lbs of torque to each of the six bolts. If any bolt rotates, accomplish the requirements of paragraph (a). (4) Apply 390 to 410 in-lbs of torque to each of the six bolts and resafety. (5) Torque and safety the droop stop nut. (6) Seal the exterior of the bolts and washers with a corrosion preventative compound. (c) 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, New York Aircraft Certification Office, FAA. Operators [[Page 2823]] shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, New York 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 New York Aircraft Certification Office. (d) 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. (e) This amendment becomes effective on February 3, 1999, to all persons except those persons to whom it was made immediately effective by Priority Letter AD 98-26-06, issued December 9, 1998, which contained the requirements of this amendment. Issued in Fort Worth, Texas, on January 8, 1999. Henry A. Armstrong, Manager, Rotorcraft Directorate, Aircraft Certification Service. [FR Doc. 99-1064 Filed 1-15-99; 8:45 am] BILLING CODE 4910-13-P