AD 2021-15-14 Airworthiness Directives; Various Restricted Category Helicopters

Makes named: robinson. Models named: HH-1K, TH-1F, TH-1L, UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, UH-1P. Read the applicability below — it usually turns on serial or part numbers too.

This AD applies to various restricted category helicopters originally manufactured by Bell Textron Inc., (Bell) certificated in any category, including but not limited to: (1) Rotorcraft Development Corporation Model HH-1K helicopters; (2) Robinson Air Crane Inc.; Rotorcraft Development Corporation; and Tamarack Helicopters, Inc., Model TH-1F helicopters; (3) Bell; Overseas Aircraft Support, Inc. (type certificate previously held by JTBAM, Inc.); and Rotorcraft Development Corporation Model TH-1L helicopters; (4) Richards Heavylift Helo, Inc., Model UH-1A helicopters; (5) International Helicopters, Inc.; Overseas Aircraft Support, Inc.; Red Tail Flying Services, LLC; Richards Heavylift Helo, Inc.; Rotorcraft Development Corporation; Southwest Florida Aviation International, Inc.; and WSH, LLC (type certificate previously held by San Joaquin Helicopters), Model UH-1B helicopters without Supplemental Type Certificate (STC) No. SR00026DE installed; Note 1 to paragraph (c)(5): Helicopters with an SW204 or SW204HP designation are Southwest Florida Aviation International, Inc., Model UH-1B helicopters. (6) Bell; Overseas Aircraft Support, Inc.; Rotorcraft Development Corporation; Smith Helicopters; and West Coast Fabrications Model UH-1E helicopters; (7) AST, Inc.; California Department of Forestry; Robinson Air Crane, Inc.; Rotorcraft Development Corporation; and Tamarack Helicopters, Inc., Model UH-1F helicopters; (8) Arrow Falcon Exporters Inc.; Global Helicopter Technology, Inc.; Hagglund Helicopters, LLC; JJASPP Engineering Services, LLC; Northwest Rotorcraft, LLC; Overseas Aircraft Support, Inc.; Richards Heavylift Helo, Inc.; Rotorcraft Development Corporation; Southwest Florida Aviation International, Inc.; and Tamarack Helicopters, Inc., Model UH-1H helicopters; Note 2 to paragraph (c)(8): Helicopters with an SW205 designation are Southwest Florida Aviation International, Inc., Model UH-1H helicopters. (9) Bell; Overseas Aircraft Support, Inc.; and Rotorcraft Development Corporation Model UH-1L helicopters; and (10) Robinson Air Crane, Inc.; and Rotorcraft Development Corporation Model UH-1P helicopters.

Comply with this AD within the compliance times specified, unless already done.

(1) Before further flight, revise the limitations section of the existing Rotorcraft Flight Manual (RFM) for your helicopter by adding the information in Figure 1 to paragraph (g)(1) of this AD or by inserting a copy of this AD. The action required by this paragraph and the checks required by Figure 1 to paragraph (g)(1) of this AD may be done by the owner/operator (pilot) holding at least a private pilot certificate and must be entered into the aircraft records showing compliance with this AD by following 14 CFR 43.9 (a)(1) through (4) and 14 CFR 91.417(a)(2)(v). The record must be maintained as required by 14 CFR 91.417, 121.380, or 135.439. BILLING CODE 4910-13-P ER26JY21.000 BILLING CODE 4910-13-C (2) Within 25 hours time-in-service (TIS): (i) Open the oil cooler/baggage compartment door on the right hand side of the helicopter to gain access to the interior of the tail boom. (ii) Remove paint and stray sealant and clean the eight attach fittings (four on the tail boom side and four on the fuselage side). Remove paint and stray sealant and clean the four cap angles, forward of the fuselage fittings, for at least 12 inches from the end of the fittings. Remove paint and stray sealant and clean the four longerons, aft of the tail boom fittings, for at least 12 inches from the end of the fittings. It is only necessary to remove the topcoat. Primer may be left in place and edge and fillet sealant may be left in place. If any primer or edge or fillet sealant is removed, before further flight, reapply the removed primer and sealant. Note 3 to paragraph (g)(2)(ii): On some models, the baggage compartment floor and net must be removed to gain access to the lower fuselage attach fittings and cap angles. (iii) With an additional person pushing on the tail boom at the third vertical rivet line aft of the trailing edge of the elevator with both hands and gradually applying and relieving pressure using body weight a minimum of three times in each of the following directions: Inboard pushing from the left; inboard pushing from the right; and upward pushing from the bottom; and using a bright light and borescope, inspect each of the four tail boom attach structures for cracks, bond separation, and loose rivets. On the fuselage side, inspect the fittings and the cap angles running forward from the fittings, paying particular attention to the fitting sections near the rivets closest to the attach bolts and the cap angle rivets next to the fittings. On the tail boom side, inspect the fittings and the longerons running aft from the fittings, paying particular attention to the fitting sections near the rivets closest to the attach bolts. Without pushing on the tail boom, and using a bright light and borescope, inspect each of the four tail boom attach structures for scratches, nicks, gouges, tears, corrosion, buckling, and distortion, and for loose, missing, and smoking rivets. If there are any scratches, nicks, gouges, tears, or corrosion within allowable limits, before further flight, repair the affected components. If there are any scratches, nicks, gouges, tears, or corrosion that exceed allowable limits, or any cracks, buckling or distortion, or loose, missing, or smoking rivets, before further flight, remove the affected components from service. If there is any bond separation, before further flight, re-bond the affected components. Note 4 to paragraph (g)(2)(iii): It is not required to push on the tail boom if it cannot be reached from ground level while inspecting for cracks, bond separation, and loose rivets. (iv) Inspect each of the four tail boom attach bolts for exposed threads. If there is less than one full thread or more than three threads exposed, before further flight, remove the bolt and self-locking nut from service and replace with a new bolt and new self-locking nut. Self-locking nuts on Model HH-1K, SW204, SW204HP, TH-1F, TH-1L, UH-1A, UH-1B without STC No. SR00026DE installed, and Model UH-1E, UH-1F, UH-1L, and UH-1P helicopters must be replaced with self-locking nut part number (P/N) NAS9926-7L at the upper left-hand (LH) attach point and self-locking nut P/N NAS9926-6L at the other three attach points. (v) Inspect each of the four tail boom attach bolts for movement by either applying the required installation torque in the tightening direction only, or by inspecting for torque stripe misalignment if present and attempting to rotate the bolt by hand. If a bolt is under-torqued, a torque stripe is misaligned, or a bolt moves, before further flight, remove the bolt and self-locking nut from service and replace with a new bolt and new self-locking nut. Self-locking nuts on Model HH-1K, SW204, SW204HP, TH-1F, TH-1L, UH-1A, UH-1B without STC No. SR00026DE installed, UH-1E, UH-1F, UH-1L, and UH-1P helicopters must be replaced with self-locking nut P/N NAS9926-7L at the upper LH attach point and self-locking nut P/N NAS9926-6L at the other three attach points. (vi) After the first flight following any bolt replacement as required by paragraph (g)(iv) or (v) of this AD, retorque any replaced bolt by applying torque in accordance with the existing maintenance instructions for your helicopter in the tightening direction only and then apply a torque stripe on the bolt head. (3) For Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B without STC No. SR00026DE installed, UH-1E, UH-1F, UH-1L, and UH-1P helicopters and Southwest Florida Aviation International, Inc. Model SW204 and SW204HP helicopters, at intervals not to exceed 25 hours TIS, perform the actions required by paragraphs (g)(2)(i) through (vi) of this AD, except you are only required to perform the actions on the upper LH tail boom attach structure including the bolt. (4) For Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B without STC No. SR00026DE installed, UH-1E, UH-1F, UH-1L, and UH-1P helicopters and Southwest Florida Aviation International, Inc. Model SW204 and SW204HP helicopters, at intervals not to exceed 100 hours TIS, perform the actions required by paragraphs (g)(2)(i) through (vi) of this AD at all four tail boom attach points. (5) For Model UH-1H helicopters and Southwest Florida Aviation International, Inc. Model SW205 helicopters, at intervals not to exceed 150 hours TIS, perform the actions required by paragraphs (g)(2)(i) through (vi) of this AD on all four tail boom attach points.

This AD was prompted by multiple events involving failure of the tail boom attach structure, including the bolts. The FAA is issuing this AD to address fatigue cracking of tail boom attach fittings, cap angles, longerons, and bolts. The unsafe condition, if not addressed, could result in separation of the tail boom from the helicopter and subsequent loss of control of the helicopter.

None.