Airworthiness Directive · Amendment 39-17772 · Tail rotor blades
Agusta S.p.A. Helicopters
This AD applies to Agusta S.p.A. (Agusta) Model AB412 and AB412 EP helicopters with a tail rotor blade (T/R) blade, part number (P/N) 212-010-750 (all dash numbers), installed, certificated in any category.
We are adopting a new airworthiness directive (AD) for Agusta S.p.A. (Agusta) Model AB412 and AB412 EP helicopters. This AD requires inspecting the tail rotor (T/R) blade for a crack, corrosion, nick, scratch, dent, or other damage and replacing or repairing the blade, depending on the damage. This AD is prompted by reports of T/R blade failures caused by fatigue cracking that originated from surface damage. These actions are intended to prevent failure of the T/R blade 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 25 hours time-in-service (TIS) or 30 days, whichever occurs first, and thereafter at intervals not to exceed 25 hours TIS or 30 days, whichever occurs first:
(i) Clean each T/R blade by hand using a mild soap and cheesecloth on both sides of the blade in a spanwise direction and dry thoroughly.
(ii) Using a 3X or higher power magnifying glass and a light, visually inspect the T/R blade skin, leading edge spar, doublers, grip plates, and trailing edge on both sides of each blade for a crack, corrosion (which may be indicated by blistering, peeling, flaking, bubbling, or cracked paint), a nick, a scratch, a dent, or other damage. Pay particular attention to both sides of each T/R blade in the area located 16 to 32 inches from the T/R blade tip (blade station 20.00 to 35.00; the T/R blade tip is located at blade station 51) as depicted by the shaded area in Figure 2 of AgustaWestland Bollettino Tecnico No. 412-136, dated August 13, 2013 (BT). Also, pay particular attention to the inboard T/R blade butt area near the attachment of the external balance weight and screws and to any T/R blade surface that was snagged by cheesecloth, as this may be an indication of a crack or paint chip that could lead to corrosion.
(iii) Using a 10X or higher power magnifying glass and a light, visually inspect both sides of each T/R blade for a crack, corrosion (which may be indicated by blistering, peeling, flaking, bubbling, or cracked paint), a nick, a scratch, a dent or other damage between blade station 20.00 to 35.00 as depicted by the shaded area in Figure 2 of the BT.
(iv) If there is any blistering, peeling, flaking, bubbling, or cracked paint on a T/R blade, remove the paint from the affected area by sanding in a spanwise direction first with abrasive cloth or paper 240-grit or finer and then with abrasive cloth or paper 400-grit or finer. After paint removal, wipe area with a clean cloth dampened with alcohol and dry thoroughly and then visually inspect the affected area for any corrosion or a crack using a 10X or higher power magnifying glass and a light. If any corrosion is found, measure the depth of the damage.
(v) If there is a nick, scratch, or dent on the T/R blade, visually inspect for a crack using a 10X or higher power magnifying glass and a light. Measure the depth of the damage.
(2) Before further flight, remove from service any T/R blade that has a crack, corrosion, a nick, a scratch, a dent, or other damage that exceeds any of the maximum repair damage limits.
(3) Before further flight, repair or remove from service any T/R blade that has corrosion, a nick, a scratch, a dent or other damage that is within the maximum repair damage limits.
(4) Do not install on any helicopter T/R blade P/N 212-010-750 (all dash numbers) unless it has been inspected in accordance with the requirements of this AD.
