Airworthiness Directive · Amendment 39-17173 · Main rotor blades
Various Restricted Category Helicopters
This AD applies to restricted category Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, and UH-1P helicopters with a main rotor (M/R) blade, part number (P/N) 204-012-001-023 or -033; 210-015-001-101; 212-015-501-005, -111, -113, -115, -117, -119, or -121, installed, certificated in any category.
We are adopting a new airworthiness directive (AD) for various restricted category Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B, UH-1E, UH- 1F, UH-1H, UH-1L, and UH-1P helicopters with certain main rotor (M/R) blade assemblies installed, to require inspecting the grip plates, doublers, and upper and lower surfaces of the M/R blades in the area between blade stations 24.5 and 40 for an edge void, corrosion, or a crack. This AD is prompted by several reports of fatigue cracks on M/R blades installed on Bell Helicopter Textron, Inc. (Bell) Model 212 helicopters. These same part-numbered M/R blades may also be installed on certain FAA-approved modified restricted category helicopters. These actions are intended to detect an edge void, corrosion, or a crack on an M/R blade, which could lead to loss of the M/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), and thereafter at intervals not to exceed 25 hours TIS:
(i) Wash the upper and lower surfaces of each affected M/R blade with a solution of cleaning compound (C-318) and water. Rinse thoroughly and wipe dry.
(ii) Using a 3x power or higher magnifying glass and a bright light, on each affected M/R blade, in an area from blade stations 24.5 to 40, including the entire width of the M/R blade chord, as depicted in Figure 1 to Paragraph (e) of this AD:
(A) Visually inspect the upper and lower grip plates and doublers of the M/R blade for an edge void, any corrosion, or a crack.
(B) Visually inspect the remaining upper and lower surfaces of the M/R blade for an edge void, any corrosion, or a crack.
Note 1 to paragraphs (e)(1)(ii) and (e)(1)(iv): The inspections required by paragraphs (e)(1)(ii) and (e)(1)(iv) of this AD do not require removal of the M/R blades from the M/R hub and can be accomplished while the M/R blades are installed on the helicopter.
Note 2 to paragraph (e)(1)(ii): Crack indications on an actual M/R blade are shown in Figure 2 to Paragraph (e) of this AD.
(iii) Wipe each of the bond lines at the edges of both grip plates and each of the layered doublers (bond lines) on the upper and lower surfaces of each affected M/R blade with an alcohol-soaked cloth (C-385) for their entire length and chord width. Wipe dry with a clean cloth.
(iv) Using a 3x power or higher magnifying glass and a bright light, visually inspect each of the bond lines on the upper and lower surfaces of the M/R blade for their entire length and chord width for an edge void, any corrosion, or any edge delamination, as indicated by a crack in the paint finish. An edge delamination is defined as a separation of the detail parts along an edge.
Note 3 to paragraph (e)(1)(iv): A crack in the paint finish which follows the outline of a grip plate or doubler may indicate a possible edge void.
(v) If there is any edge delamination along any bond line of a grip plate or doubler, or a crack in the paint finish, before further flight, remove the paint in the affected area by lightly sanding with 180-220 grit paper in a span-wise direction to determine if there is an edge void, or if the grip plate, doubler, or skin is cracked. If any parent material is removed during the sanding operation, replace the M/R blade with an airworthy M/R blade or repair the M/R blade if the amount of parent material removed is within the maximum repair damage limits. If there is no edge void or crack, refinish the sanded area.
Note 4 to paragraphs (e)(1)(v) and (e)(2): The maximum repair damage limits are contained in the applicable Component and Repair Overhaul Manual.
(vi) If there is no edge void, corrosion, or crack, apply a light coat of preservative oil (C-125) to all surfaces of each affected M/R blade.
(2) If an edge void, any corrosion, or a crack is discovered during any inspections in paragraph (e)(1) of this AD, before further flight, accomplish the following:
(i) If there is an edge void, determine the depth and length using a.0015 inch feeler gauge.
(ii) If there is an edge void in a grip plate or doubler near the outboard tip, tap inspect the affected area to determine the size and shape of the void.
(iii) Repair the M/R blade if the edge void is within the maximum repair damage limits or replace the M/R blade with an airworthy M/R blade.
(iv) If there is any corrosion, replace the M/R blade with an airworthy M/R blade or repair the M/R blade if the damage is within the maximum repair damage limits.
(v) If there is a crack in any grip plate or doubler, replace the M/R blade with an airworthy M/R blade.
(vi) If there is a crack in the M/R blade skin, replace the M/R blade with an airworthy M/R blade, or repair the M/R blade if the damage is within the maximum repair damage limits.
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.
Aircraft
Appliances and equipment
