AD 99-25-12 Airworthiness Directives; Bell Helicopter Textron-manufactured Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, and UH-1P Helicopters; and Southwest Florida Aviation SW204, SW204HP, SW205, and SW205A-1 Helicopters

Model HH-1K (Type Certificate Data Sheet (TCDS) H5NM), TH-lF (TCDS H12NM, and R00008AT), TH-1L (TCDS H5NM, H7SO, and H4NM), UH-1A (TCDS H3SO), UH-1B (TCDS H1RM, H3NM, H13WE, H3SO, H5SO, and R00012AT), UH-1E (TCDS H5NM, H7SO, H8NM, and H4NM), UH-1F (TCDS H2NM, H7NE, H11SW, H12NM, and R00008AT), UH-1H (TCDS H13WE, H3SO, H15NM, and R00007DE), UH-lL (TCDS H5NM, H7SO, and H4NM), UH-1P (TCDS H12NM, and R00008AT), and SW204 (TCDS H6SO), SW204HP (TCDS H6SO), SW205 (TCDS H6SO), and SW205A-1 (TCDS H6SO) helicopters, with tailboom vertical fin spar (vertical fin spar), part number (P/N) 205-032-899-all dash numbers, 205-030-846-all dash numbers, or 205- 032-851-all dash numbers, installed, certificated in any category. Note 1: This AD applies to each helicopter identified in the preceding applicability provision, regardless of whether it has been otherwise modified, altered, or repaired in the area subject to the requirements of this AD. For helicopters that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (h) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Required as indicated, unless accomplished previously. To prevent failure of the tailboom vertical fin (fin) spar and subsequent loss of control of the helicopter, accomplish the following: [[Page 68279]] (a) Within 8 hours time-in-service (TIS), modify the vertical fin spar as follows: (1) Remove the 42 deg. gearbox cover and open the drive shaft cover on the fin spar assembly (see Figure 1). (2) Remove the first four rivets from the fin spar located at the bottom of the fin spar left-hand side at the tailboom and fin spar junction, and the first four rivets aft of the junction along the lower edge of the fin spar side-skin as shown (see Figure 2). (3) Trim the fin spar left-hand skin using extreme care to not damage the fin spar assembly (see Figure 3). (4) Deburr the rivet holes and trimmed skin edges. Remove all debris. In a ventilated work area, remove any surface contaminants with a cloth that has been dampened with aliphatic naphtha or an equivalent cleaning solvent. (5) Reattach the side-skin to the fin spar using MS 20470AD rivets. DO NOT install the bottom two rivets into the fin spar where the skin was trimmed. (6) Attach the fin spar side-skin lower edge using the rivets specified in Figure 3. (7) Refinish all reworked areas. (b) After modifying the fin spar assembly, inspect the fin spar for cracks before further flight and thereafter, at intervals not to exceed 8 hours TIS as follows: (1) Remove the lower aft tailboom inspection door, located at tailboom station 180 (see Figure 1). (2) Remove the 42 deg. gearbox cover and open the drive shaft cover on the fin (see Figure 1). (3) In a ventilated work area, clean all surfaces to be inspected with a cloth dampened with aliphatic naphtha or an equivalent cleaning solvent. (4) Through the lower aft tailboom inspection door, using a bright light and an inspection mirror, inspect the fin spar assembly adjacent to the tailboom top skin on the forward side, paying special attention to the left-hand edge and the adjacent surfaces (see Figures 1 and 2). (5) Using a bright light and a 10x or higher magnifying glass, inspect the fin spar assembly adjacent to the tailboom top-skin on the in-board and out-board sides, the vertical edge, and the two open rivet holes. Using a bright light and a mirror, inspect the aft side of the fin spar in the same area. Special attention must be given to the left-hand edge of the fin spar and any adjacent surfaces between fin stations 66.31 and 71.31 (see Figure 2). (6) If any crack is discovered on the fin spar, replace the fin spar assembly with an airworthy fin spar assembly before further flight. (c) Within 50 hours TIS, and thereafter at intervals not to exceed 50 hours TIS, inspect the fin spar assembly as follows: (1) Remove the 42 deg. gearbox cover and open the driveshaft cover on the fin spar assembly (see Figure 1). Remove the aft lower fin fairing and fin access panels that allow access to the aft side of the forward fin spar and the secondary spar (see Figure 1). (2) In a ventilated work area, clean all surfaces to be inspected with a cloth dampened with aliphatic naphtha or an equivalent cleaning solvent. Using a bright light, 10x or higher magnifying glass, and a borescope as required, inspect all of the fin ribs, fittings, skins, and secondary aft spar of the fin assembly (see Figures 4 and 5). Pay particular attention to the upper and lower fittings at tailboom station 227 for cracked or corroded fittings or sheared or loose rivets. (3) Gain access to the canted bulkhead aft of tailboom station 194.30 through the most aft lower access covers by removing the aft access covers or position light fairings as required. Visually inspect the canted bulkhead forward and aft sides through the lower tailboom inspection hole and position light access holes for cracks, corrosion, or loose or sheared rivets in all skins, fittings and bulkheads using a bright light, an inspection mirror, and a borescope as required (see Figures 4 and 5). Pay particular attention to the area in the upper forward corners of the aft skin directly around the fin spar assembly and the overlap area of the top skin beneath the 42 deg. gearbox for cracks, which are only visible from the underside. (4) Any crack found in the fin spar assembly requires replacement with an airworthy part. Replacing the entire fin spar configuration with an airworthy fin spar configuration that has been demonstrated to the FAA to satisfy the structural fatigue requirements of repeated high-torque events and is approved by the Manager, FAA, Rotorcraft Standards Staff, will constitute a terminating action for the requirements of this AD. Any corrosion, loose or sheared rivets, or cracked skins or ribs found within the inspection areas must be repaired prior to further flight. (d) Within 50 hours TIS, modify the fin spar as follows: (1) Remove the 42 deg. gearbox cover and open the driveshaft cover on the fin spar assembly (see Figure 1). (2) Remove the next 10 rivets from the fin spar located at the bottom of the fin spar left-hand side at the tailboom and fin spar junction (see Figures 6 and 7, whichever is applicable). Caution: Extreme care must be taken when drilling and removing rivets from the side of the fin spar to ensure the fin spar assembly is not damaged. (3) Trim the fin left-hand side skin using extreme care to not damage the fin spar assembly to expose the spar outboard edge (See Figure 6 or 7, whichever is applicable). (4) Deburr the rivet holes and trimmed side skin edges. Remove all debris. In a ventilated work area, remove any surface contaminates with a cloth that has been dampened with aliphatic naphtha or an equivalent cleaning solvent. (5) Fabricate cover plates in accordance with the notes and drawings of Figure 8 or 9, whichever is applicable. Ream prepare the holes in the fin spar and parts and install HI-LOK fasteners. Note 2: Bell Helicopter Medium Structural Repair Manual, BHT- MED-SRM-1, pages 3-36 through 3-38, pertains to this installation and reaming procedure. (6) Refinish all reworked areas, close driveshaft and replace 42 deg. gearbox cover. (e) After modification of the fin spar assembly, before further flight and thereafter at intervals not to exceed 100 hours TIS, inspect the fin spar for cracks as follows: (1) Remove the 42 deg. gearbox cover, open the driveshaft cover on the vertical fin spar assembly, and remove the spar cover plate and filler plate from the lower left-hand side of the fin assembly (see Figures 1 and 8 or 9, whichever is applicable). Caution: Extreme care must be taken when removing the cover plate and filler from the side of the fin spar to ensure that the spar assembly is not damaged. (2) In a ventilated work area, clean the surface to be inspected with a cloth dampened with aliphatic naphtha. Caution: Do not use chemical paint strippers. Use Scotch-Brite Grade-A VFN and methyl-ethyl ketone (MEK) or a suitable solvent to remove the paint and primer in the inspection area. (3) Perform a dye-penetrant inspection of the exposed area of the fin spar (see Figures 6 and 7). Note 3: ASTM E1416 or MIL-STD-6866, or the Bell Helicopter Standard Practices Manual, BHT-ALL-SPM, Chapter 6.2, pertains to this inspection. (4) If any crack is discovered on the fin spar, replace the fin spar assembly with an airworthy fin spar assembly before further flight. (5) After inspection, apply zinc chromate primer to the bare surfaces. When dry, re-install the cover plate and the filler using fasteners specified in Figure 8 or 9, whichever is applicable. (6) Install the 42 deg. gearbox cover and the driveshaft cover. (f) Within 12 calendar months, remove the fin spar, P/N 205-030- 846-all dash numbers, P/N 205-032-899-all dash numbers, or P/N 205- 032-851-all dash numbers, whichever is applicable, and replace it with an airworthy fin spar configuration that has been demonstrated to the FAA to satisfy the structural fatigue requirements of repeated high torque events, and is approved by the Manager, FAA, Rotorcraft Standards Staff. BILLING CODE 4910-13-U [[Page 68280]] [GRAPHIC] [TIFF OMITTED] TR07DE99.079 [[Page 68281]] [GRAPHIC] [TIFF OMITTED] TR07DE99.080 [[Page 68282]] [GRAPHIC] [TIFF OMITTED] TR07DE99.081 [[Page 68283]] [GRAPHIC] [TIFF OMITTED] TR07DE99.082 [[Page 68284]] [GRAPHIC] [TIFF OMITTED] TR07DE99.083 [[Page 68285]] [GRAPHIC] [TIFF OMITTED] TR07DE99.084 [[Page 68286]] [GRAPHIC] [TIFF OMITTED] TR07DE99.085 [[Page 68287]] [GRAPHIC] [TIFF OMITTED] TR07DE99.086 [[Page 68288]] [GRAPHIC] [TIFF OMITTED] TR07DE99.087 BILLING CODE 4910-13-C [[Page 68289]] (g) Replacing the fin spar, P/N's 205-032-899-all dash numbers, 205-030-846-all dash numbers, or 205-032-851-all dash numbers, with an airworthy fin spar that has been demonstrated to the FAA to satisfy the structural fatigue requirements of repeated high torque events and approved by the Manager, FAA, Rotorcraft Standards Staff, constitutes a terminating action for the requirements of this AD. (h) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, FAA, Regulations Group, Rotorcraft Standards Staff. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, FAA, Regulations Group. Note 4: Information concerning the existence of approved fin spar configurations and alternative methods of compliance with this AD, if any, may be obtained from the Regulations Group. (i) Special flight permits may be issued in accordance with Secs. 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the helicopter to a location where the requirements of this AD can be accomplished. (j) This amendment becomes effective on January 11, 2000. Issued in Fort Worth, Texas, on November 30, 1999. Mark R. Schilling, Acting Manager, Rotorcraft Directorate, Aircraft Certification Service. [FR Doc. 99-31675 Filed 12-6-99; 8:45 am] BILLING CODE 4910-13-U