Airworthiness Directive · Amendment 39-17879 · And 6210 nacelle/pylon structure and main rotor blades
Columbia Helicopters, Inc. (Type Certificate Previously Held by Boeing Defense & Space Group) Helicopters
This AD applies to Model 234 helicopters, certificated in any category.
We are adopting a new airworthiness directive (AD) for Columbia Helicopters, Inc. (Columbia) Model 234 helicopters. This AD requires visually and tap inspecting each fore and aft rotor blade for any defect, damage, or a disbond and, if necessary, repairing or replacing the blade. Also, this AD requires dye-penetrant inspecting the aft pylon structure for fatigue cracking in certain areas near the attachment fittings and, if there is a crack, repairing or replacing the aft pylon. This AD is prompted by an accident caused by fatigue failure of an aft pylon fitting attach structure combined with aft rotor blade damage. The actions specified by this AD are intended to detect fatigue cracks in the aft pylon attach structure to prevent overload of the aft pylon structure and failure of the rotor blade, rotor blade vibration, departure of the aft pylon, and subsequent loss of control of the helicopter.
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 50 hours time-in-service (TIS):
(i) Clean and inspect each fore and aft rotor blade for a defect, damage, or a disbond in accordance with the Accomplishment Instructions, paragraph 3.A.(1)(b) through 3.A.(2)(b), of Columbia Helicopters, Inc., Service Bulletin No. 234-62-0008, Revision 1, dated December 6, 2013 (SB 234-62-0008).
(ii) Using a metallic coin or tap hammer, tap inspect each rotor blade trailing edge for defect, damage, or a disbond in accordance with the Accomplishment Instructions, paragraph 3.B.(1) through 3.B.(2)(e) and Figures 1 and 2 of SB 234-62-0008.
(iii) If there is any defect, damage, or a disbond, repair the blade before further flight. If the defect, damage, or disbond is beyond acceptable limits, replace the blade before further flight.
(2) Within 50 hours TIS and thereafter at intervals not to exceed 100 hours TIS, inspect the aft pylon at the station 534 and 594 tension attachment fittings as follows:
(i) Dye-penetrant inspect the aft pylon at the attachment fitting for a crack as shown in Figures 1, 2, and 3 and by following the Detailed Special Inspection-Dye Penetrant Method, paragraph 2.A.(2) through 2.G.(1), of Columbia Helicopters, Inc. Service Bulletin No. 234-54-0004, Revision 0, dated November 22, 2013 (SB 234-54-0004).
(ii) If there is a crack, before further flight, repair or replace the aft pylon. Figures 2, 3, 4, and 5 of SB 234-54-0004 contain examples of a crack.
(3) Do not install an aft pylon or a rotor blade until the requirements of paragraphs (e)(1) and (e)(2) of this AD are accomplished.
