AD 97-20-09

This amendment supersedes an existing priority letter airworthiness directive (AD), applicable to Bell-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, and SW205 helicopters, that currently requires modification and inspections of the vertical fin spar. This amendment requires the same modification and inspections required by the existing priority letter AD, but adds the Southwest Florida Aviation Model SW205A-1 and Utah State University UH-1H helicopters to the applicability of this AD. This amendment is prompted by accidents involving in-flight failure of the tailboom vertical fin spar. The actions specified by this AD are intended to prevent in-flight failure of the vertical fin spar and subsequent loss of control of the helicopter.

Final rule; request for comments.

97-20-09 CALIFORNIA DEPARTMENT OF FORESTRY; FIREFLY AVIATION HELICOPTER SERVICES (PREVIOUSLY ERICKSON AIR CRANE CO.); GARLICK HELICOPTERS, INC.; HAWKINS AND POWERS AVIATION, INC.; INTERNATIONAL HELICOPTERS, INC.; RANGER HELICOPTER SERVICES; ROBINSON AIRCRANE; SCOTT PAPER CO.; SMITH HELICOPTERS; SOUTHERN HELICOPTER; SOUTHWEST FLORIDA AVIATION; UTAH STATE UNIVERSITY; WESTERN INTERNATIONAL AVIATION, INC.; UNC HELICOPTERS; AND U.S. HELICOPTER, INC.: Amendment 39-10521. Docket No. 97-SW-35-AD. Final Rule priority letter AD 97-20-09. \n\n\tApplicability: Model HH-1K (Type Certificate Data Sheet (TCDS) H5NM), TH-lF (TCDS H12NM, and R0008AT), 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 R0008AT), UH-1H (TCDS H13WE, H3SO, and H15NM), UH-lL (TCDS H5NM, H7SO, and H4NM), UH-1P (TCDS H12NM, and R0008AT), and SW204 (TCDS H6SO), SW204HP (TCDS H6SO), SW205 (TCDS H6SO), and SW205A-1 (TCDS H6SO) helicopters, with tailboom vertical fin spar, part number (P/N) 205-032-899, 205-030-846, or 205-032-851, all dash numbers, installed, certificated in any category. \n\n\tNOTE 1: This AD applies to each helicopter identified in the preceding applicability provision, regardless of whether it has been 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 use the authority provided in paragraph (d) to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition, or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any helicopter from the applicability of this AD. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent in-flight failure of the tailboom vertical fin spar (vertical fin spar) and subsequent loss of control of the helicopter, accomplish the following: \n\n\t(a)\tWithin 8 hours time-in-service (TIS) after the effective date of this AD, modify the vertical fin spar as follows: \n\n\t\t(1)\tRemove the 42 deg. gearbox cover and open the drive shaft cover on the vertical fin spar assembly (see Figure 1). \n\n\t\t(2)\tRemove the first four rivets from the vertical fin spar located at the bottom of the vertical fin spar left-hand side at the tailboom and vertical fin spar junction, and the first four rivets aft of the junction along the lower edge of the vertical fin spar side-skin as shown (see Figure 2). CAUTION: Extreme care must be taken when drilling and removing rivets from the side of thevertical fin spar to ensure the vertical fin spar assembly is not damaged. \n\n\t\t(3)\tTrim the vertical fin spar left-hand skin using extreme care to not damage the vertical fin spar assembly (see Figure 3). \n\n\t\t(4)\tDeburr 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. \n\n\t\t(5)\tReattach the side-skin to the vertical fin spar using MS 20470AD rivets. DO NOT install the bottom two rivets into the vertical fin spar where the skin was trimmed. \n\n\t\t(6)\tReinstall the vertical fin spar skin lower edge rivets using M 7885/6-5 rivets (see Figure 2). \n\n\t\t(7)\tRefinish all reworked areas. \n\n\t\t(8)\tAfter modifying the vertical fin spar, immediately inspect the vertical fin spar in accordance with paragraphs (b)(3) and (b)(4) of this AD. \n\n\t(b)\tAfter the initial modification and inspection of the vertical fin spar have been accomplished in accordance with paragraph (a) of this AD, thereafter, at intervals not to exceed 8 hours TIS, inspect the vertical fin spar for cracks as follows: \n\n\t\t(1)\tRemove the lower aft tailboom inspection door, located at tailboom station 180 (see Figure 4). \n\n\t\t(2)\tRemove the 42 deg. gearbox cover and open the drive shaft cover on the vertical fin (see Figure 1). \n\n\t\t(3)\tThrough the lower aft tailboom inspection door, using a bright light and an inspection mirror, inspect the vertical 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 Figure 2). \n\n\t\t(4)\tIn 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 and a 10x magnifying glass, inspect the vertical fin spar assembly adjacent to the tailboom top-skin on the in-board and out-board sides, the vertical edge, andthe two open rivet holes. Using a bright light and a mirror, inspect the aft side of the vertical fin spar in the same area. Special attention must be given to the left-hand edge of the vertical fin spar and any adjacent surfaces between fin stations 66.31 and 71.31 (see Figure 2). \n\n\t(c)\tIf any crack is discovered on the vertical fin spar as a result of the inspection specified in paragraphs (b)(3) or (b)(4) of this AD, replace the vertical fin spar assembly with an airworthy vertical fin spar assembly before further flight. \n\n\t(d)\tAn 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, Rotorcraft Certification Office, FAA. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Rotorcraft Certification Office. \n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\nFigure 4 \n\n\n\tNOTE 2: Informationconcerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Rotorcraft Certification Office. \n\n\t(e)\tSpecial flight permits may be issued in accordance with sections 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. \n\n\t(f)\tThis amendment becomes effective on May 28, 1998.

On September 17, 1997, the FAA issued priority letter AD 97-20-09, applicable to Bell-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 and SW205 helicopters, which requires modification and inspections of the vertical fin spar. That priority letter AD was prompted by two accidents involving in-flight failures of the tailboom vertical fin spars (vertical fin spars) on Model TH-lL and UH-1B helicopters. One other accident occurred on a Model 205A-1 helicopter which is of similar type design. One of the accidents resulted in a fatality. As a result of those accident investigations, the FAA determined that a large number of high-power events can cause fatigue cracks which will cause the vertical fin spar to fail. This condition, if not corrected, could result in in-flight failure of the vertical fin spar and subsequent loss of control of the helicopter.Since the issuance of that priority letter AD, the FAA has determined that additional helicopter models are affected by the same unsafe condition. \n\n\tSince an unsafe condition has been identified that is likely to exist or develop on other Bell-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 of a similar type design, this AD supersedes priority letter AD 97-20-09 to add the Model SW205A-1 helicopters and the Utah State University UH-1H helicopters to the applicability of this AD. The short compliance time involved is required because the previously described critical unsafe condition can adversely affect the structural integrity of the helicopter. Therefore the inspections and modification are required within 8 hours time-in-service and this AD must be issued immediately. \n\n\tSince a situation exists that requires the immediate adoption of thisregulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days. \n\n\tThe FAA estimates that 68 helicopters of U.S. registry would be affected by this proposed AD, that it would take approximately 2.5 work hours per helicopter for the initial modification and inspection, 200 work hours to replace the vertical fin spar, and that the average labor rate is $60 per work hour. Required parts would cost approximately $8,000 per helicopter to replace the vertical fin spar. Based on these figures, the total cost impact of the proposed AD on U.S. operators is estimated to be $1,370,200 to modify the vertical fin, conduct an initial inspection, and replace the vertical fin spars on all helicopters in the U.S. fleet. \n\nComments Invited \n\n\tAlthough this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded bynotice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications should identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed. \n\n\tComments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the RulesDocket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket. \n\n\tCommenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket No. 97-SW-35-AD." The postcard will be date stamped and returned to the commenter. \n\n\tThe regulations adopted herein will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. \n\n\tThe FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES." \n\nList of Subjects in 14 CFR Part 39 \n\tAir transportation, Aircraft, Aviation safety, Safety. \n\nAdoption of the Amendment \n\tAccordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows: \n\nPART 39 - AIRWORTHINESS DIRECTIVES \n\t1. The authority citation for part 39 continues to read as follows: \n\tAuthority: 49 U.S.C. 106(g), 40113, 44701. \n\n§ 39.13 (Amended) \n\t2. Section 39.13 is amended by adding a new airworthiness directive (AD), Amendment 39-10521, to read as follows: