Airworthiness Directive · Amendment 39-17267 · Rotorcraft tail boom
Erickson Air-Crane Incorporated Helicopters
This AD applies to Erickson Air-Crane Incorporated (Erickson) Model S-64F helicopters with a left or right splice fitting (transition fitting), part number (P/N) 6420-66341-101, -102, -103, or -104; pylon bulkhead assembly-canted (bulkhead assembly), P/N 6420-66340-043 or -044; or a pylon steel strap (strap), P/N 6420-66301-119 or -127, installed, certificated in any category.
We are adopting a new airworthiness directive (AD) for Erickson Air-Crane Incorporated (Erickson) Model S-64F helicopters. This AD requires inspecting for cracking or working rivets in each left and right splice fitting (transition fitting), the pylon bulkhead assembly-canted (bulkhead assembly), and the pylon steel strap (strap). This AD was prompted by several reports of cracking in the transition fittings, the bulkhead assembly, and the pylon. The actions specified by this AD are intended to detect cracking in the rotary rudder boom or pylon due to fatigue, and to prevent failure from static overload 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 20 hours time-in-service (TIS), and thereafter at intervals not to exceed 20 hours (TIS):
(i) Visually inspect each transition fitting, P/N 6420-66341-101, -102, -103, or -104, for a crack or working rivets on the inboard face of the rotary rudder boom and pylon, paying particular attention to the fastener attachment holes, as depicted in Figure 1, Detail A, of the Accomplishment Instructions in Erickson Air-Crane Incorporated Service Bulletin No. 64B20-6, Revision A, dated December 12, 2007 (SB).
(ii) Visually inspect the outboard face of each rotary rudder boom and pylon skin panel (skin panel) that attaches to the transition fittings for a crack or working rivets in the transition fitting attachment areas, paying particular attention to the fastener attachment holes, as shown in Figure 1, Detail B, of the Accomplishment Instructions in the SB.
(iii) Visually inspect the forward and aft sides of each bulkhead assembly, P/N 6420-66340-043 or -044, for a crack. Pay particular attention to the circled areas shown in Figure 2 of the Accomplishment Instructions in the SB.
(iv) Visually inspect the upper 12 inches of each strap, P/N 6420-66301-119 or -127, for a crack or for working rivets as shown in Figure 3 of the Accomplishment Instructions in the SB.
(v) Visually inspect the pylon for a crack or working rivets on each side of the upper 12 inches of the strap, and also 6 inches above the end of the strap as shown in Figure 3 of the Accomplishment Instructions in the SB.
(2) For any pylon with a strap installed, within 155 hours TIS, and thereafter at intervals not to exceed 155 hours TIS, remove the inspection access covers, P/N 6420-66304-109 and P/N 6420-66303-125, on the forward and aft sides of the pylon and visually inspect the left-hand cap angle (longeron), P/N 6420-66304-136, and the interior area of the pylon adjacent to the upper 12 inches of the strap, as well as 6 inches above the end of the strap, for a crack or working rivets, as shown in Figure 3 of the Accomplishment Instructions in the SB.
(3) At each transition fitting replacement, which is required at intervals not to exceed 8,300 hours TIS:
(i) With each transition fitting removed, visually inspect both sides of each skin panel for a crack in the areas to which the transition fitting attaches, paying particular attention to the fastener attachment holes, as depicted in Details A and B, Figure 1, of the Accomplishment Instructions in the SB.
(ii) Perform a fluorescent penetrant inspection of each skin panel for a crack in the areas around the fastener holes where the transition fittings attach to the rotary rudder boom and pylon.
(4) If there is a crack, before further flight, replace any cracked part with an airworthy part, or repair the cracked part if the damage is within the maximum repair damage limits.
Note to paragraph (e)(4) of this AD: The maximum repair damage limitations are stated in the applicable Component and Repair Overhaul Manual.
(5) If any loose or working rivets are found, before further flight, remove the rivets and visually inspect the fastener holes and surrounding area for a crack or any other damage. Replace any part that is cracked with an airworthy part; replace any damaged part with damage exceeding the maximum repair damage limits with an airworthy part; or repair any damaged part that is within the maximum repair damage limits. Also, replace any loose or working rivets.
