Airworthiness Directive · Amendment 39-18950 · Main rotor drive system
Sikorsky Aircraft Corporation Helicopters (Type Certificate Previously Held by Schweizer Aircraft Corporation)
This AD applies to Model TH55A, 269A, 269A-1, 269B, 269C and 269C-1 helicopters, with a lower coupling driveshaft (driveshaft) part number (P/N) 269-5412, 269A5504, 269A5504-003, 269A5504-005, 269A5559, or 269A5559-003 installed, certificated in any category.
We are superseding airworthiness directive (AD) 93-17-13 for Schweizer Aircraft Corporation and Hughes Helicopters, Inc. (now Sikorsky Aircraft Corporation) (Sikorsky) Model TH55A, 269A, 269A-1, 269B, and 269C helicopters. AD 93-17-13 required installing tachometer markings and inspecting the lower coupling driveshaft (driveshaft). This new AD requires repetitive inspections of the driveshaft and expands the applicability to include Model 269C-1 helicopters. This AD is prompted by reports of accidents because of driveshaft failures. The actions of this AD are intended to prevent the unsafe condition on these products.
You are responsible for performing each action required by this AD within the specified compliance time unless it has already been accomplished prior to that time.
(1) Within 25 hours time-in-service (TIS), install engine and rotor tachometer markings in accordance with Part II of Schweizer Aircraft Service Bulletin B-257.1, dated May 21, 1993.
(2) Within 25 hours TIS and thereafter at intervals not to exceed 150 hours TIS:
(i) Visually inspect the driveshaft for corrosion, a pit, a nick, a scratch, a dent, and a crack in accordance with the Accomplishment Instructions, paragraph 3.B.(1) through 3.B.(6) of Sikorsky 269C Helicopter Alert Service Bulletin B-307, Basic Issue, dated December 18, 2014 (269C ASB), or Sikorsky 269C-1 Helicopter Alert Service Bulletin C1B-043, Basic Issue, dated December 18, 2014 (269C-1 ASB), whichever is applicable for your model helicopter, except we do not require that you use a Sikorsky recommended vendor list. If there is any corrosion, a pit, a nick, a scratch, a dent, or a crack, replace the driveshaft before further flight.
(ii) If there is no corrosion and no pits, nicks, scratches, dents, and cracks, magnetic particle inspect the driveshaft for a crack in accordance with paragraph 3.C.(1) of the 269C ASB or 269C-1 ASB, whichever is applicable for your model helicopter. This magnetic particle inspection must be performed by a Level II or higher technician with the National Aerospace Standard 410 or equivalent certification who has performed a magnetic particle inspection within the last 12 months. If there is a crack, replace the driveshaft before further flight.
Compliance with paragraph (a)(1) of AD 93-17-13, Amendment 39-8684 (58 FR 51770, October 5, 1993) before the effective date of this AD is considered acceptable for compliance with the actions specified in paragraph (f)(1) of this AD.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
