AD 95-22-09

This amendment supersedes an existing airworthiness directive (AD), applicable to Boeing Defense and Space Group Helicopter Division (Boeing) Model 234 series helicopters, that currently requires inspections of the forward and aft transmission first stage sun and spiral bevel ring gear bolted connection (bolted connection). This amendment requires a revision to the inspection intervals and criteria used during these inspections, as well as adds a visual inspection of the pinion and spiral bevel ring gear. This amendment is prompted by reports that certain of the affected helicopters have been discovered with loose nuts on the bolted connection more frequently than was anticipated in the previous AD. The actions specified by this AD are intended to prevent wear of the spiral bevel ring gear flange surface, failure of the bolted connection, transmission failure, and subsequent loss of control of the helicopter.

Final rule

95-22-09 BOEING DEFENSE AND SPACE GROUP HELICOPTER DIVISION: Amendment 39-9417. Docket No. 92-ASW-01-AD. Supersedes AD 84-22-04, Amendment 39-4943.

Applicability: Model 234 series helicopters, with forward rotor transmission, part numbers (P/N) 234D1200-2, -3, or -4, or aft rotor transmission, P/N 234D2200-3 or -4, 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 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 (c) 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 describedin 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.

Compliance: Required as indicated, unless accomplished previously.

To prevent wear of the spiral bevel ring gear flange surface, failure of the bolted connection, transmission failure, and subsequent loss of control of the helicopter, accomplish the following:

(a) For helicopters that perform six or more landings, ground-air-ground cycles, or external load lifts per hour, or any combination thereof, conduct the following:

(1) Within the next 10 hours time-in-service (TIS) after the effective date of this AD, or prior to the accumulation of 150 hours TIS since installed or since the last disassembly of the spiral bevel ring gear bolted connection, whichever occurs later, accomplish the following:

(i) Conduct a Spectrometric Oil Analysis Program (SOAP) sample inspection in accordance with the applicable maintenance manual.

(ii) Visually inspect the pinion and spiral bevel ring gear teeth for scuffing. If scuffing is found, remove both the pinion and the first stage sun and spiral bevel ring gear assemblies, disassemble the gear assemblies, inspect them in accordance with the applicable overhaul manual, and replace unairworthy parts.

(iii) Perform a bolt torque inspection of the bolted connection in accordance with the applicable maintenance manual.

(2) Repeat the inspections required by paragraph (a)(1) at intervals not to exceed 50 hours TIS if no nuts in the bolted connection rotate at a torque below 350 in.-lb.

(3) Repeat the inspection required by paragraph (a)(1) at intervals not to exceed 25 hours TIS if no more than two nuts in the bolted connection rotate at a torque below 350 in.-lb., but above 275 in.-lb.

(4) Replace the transmission with an airworthy transmission prior to further flight if three or more nuts in the bolted connection rotate at a torque below 350 in.-lb., or if any nut rotates at a torque at or below 275 in.-lb.

(5) Conduct supplementary SOAP sample inspections at intervals not to exceed 25 hours TIS after the last SOAP sample inspection.

(b) For helicopters that perform less than six landings, ground-air-ground cycles, or external load lifts per hour, or any combination thereof, conduct the following inspections:

(1) Within the next 50 hours TIS after the effective date of this AD, or prior to the accumulation of 500 hours TIS since installed or since the last disassembly of the spiral bevel ring gear bolted connection, whichever occurs later, accomplish the following:

(i) Conduct a SOAP sample inspection in accordance with the applicable maintenance manual.

(ii) Visually inspect the pinion and spiral bevel ring gear teeth for scuffing. If scuffing is found,remove both the pinion and the first stage sun and spiral bevel ring gear assemblies, disassemble the gear assemblies, inspect them in accordance with the applicable overhaul manual, and replace unairworthy parts.

(iii) Perform a bolt torque inspection of the bolted connection in accordance with the applicable maintenance manual.

(2) Repeat the inspections required by paragraph (b)(1) at intervals not to exceed 300 hours TIS if no nuts in the bolted connection rotate at a torque below 350 in.-lb.

(3) Repeat the inspections required by paragraph (b)(1) at intervals not to exceed 100 hours TIS if no more than two nuts in the bolted connection rotate at a torque below 350 in.-lb, but above 275 in.-lb.

(4) Replace the transmission with an airworthy transmission prior to further flight if three or more nuts in the bolted connection rotate at a torque below 350 in.-lb., or if any nut rotates at a torque at or below 275 in.-lb.

(5) Conduct supplementary SOAP sample inspections at intervals not to exceed 50 hours TIS after the last SOAP sample inspection.

NOTE 2: Boeing Helicopters Service Bulletin No. 234-63-1010, Revision 4, dated January 31, 1992, pertains to this AD. Boeing 234-2 Maintenance Manual, section 63-25-50, pertains to this AD. Boeing 234-5 Overhaul Manual pertains to this AD.

(c) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used when approved by the Manager, New York Aircraft Certification Office. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, New York Aircraft Certification Office.

NOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the New York Aircraft Certification Office.

(d) Special flight permits may be issued in accordance with sections 21.197and 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.

(e) This amendment becomes effective on December 6, 1995.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 84-22-04, Amendment 39-4943 (49 FR 44093, November 2, 1984), which is applicable to Boeing Model 234 series helicopters, was published in the Federal Register on August 19, 1992 (57 FR 37481). That action proposed to require, within 10 hours time-in-service (TIS) or prior to the accumulation of 150 hours TIS for helicopters that conduct six or more landings, ground-air-ground cycles, or external load lifts per hour, or any combination thereof: (1) an initial Spectrometric Oil Analysis Program (SOAP) sample inspection; (2) a visual inspection of the pinion and spiral bevel ring gear teeth for scuffing; (3) an initial bolt torque inspection of the bolted connection; and (4) thereafter, repetitive inspections at 25 hours TIS or 50 hours TIS depending on the torque values present on the nuts of the bolted connection when the previous inspection was conducted. Additionally, that action proposed to require, within 50 hours TIS or prior to the accumulation of 500 hours TIS for helicopters that conduct less than six landings, ground-air-ground cycles, or external load lifts per hour or any combination thereof: (1) an initial SOAP sample inspection; (2) a visual inspection of the pinion and spiral bevel ring gear teeth for scuffing; (3) an initial bolt torque inspection of the bolted connection, and (4) repetitive inspections at 100 hours TIS or 300 hours TIS depending on the torque values present on the nuts of the bolted connection when the previous inspection was conducted.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the one comment received.

The commenter requests an increase in the TIS before the initial inspections from 150 to 200 hours TIS, and from 50 to 100 hours TIS between the repetitive inspections, and deletion of the proposed requirement for a SOAP inspection. The commenter states that with the repairs they have made and by using improved lubricants, their experience shows that the interval between inspections can be extended. The commenter also states that SOAP inspections are already being performed; therefore, a SOAP inspection should not be required. The FAA neither concurs with increasing the initial nor repetitive inspection intervals, nor does it concur in the commenter's position that SOAP inspections should not be required. After an analysis of the manufacturer's recommendations and the affected helicopter usage, the FAA has determined that helicopters involved in operations that require constant power changes such as logging, heavy lift operations, or several ground-air-ground cycles for each flight hour are more likely to be subject to the nut loosening or gear teeth scuffing conditions and at a faster rate. Therefore, inspection intervals are spaced such that early detection of any unsafecondition or unairworthy part is more likely to occur.

After careful review of the available data, including the comment noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed, except for reorganizing and editorial changes.

The FAA estimates that 7 helicopters of U.S. registry will be affected by this AD, that it will require 100 SOAP and 100 torque inspections per year per helicopter, and that it will take approximately 2 work hours with a crew of 2 per helicopter to accomplish the 50 hour TIS inspection, and 1 work hour with 1 person per helicopter to accomplish the SOAP sample inspection. The average labor rate is $60 per work hour. Based on these figures, the total cost of the AD on U.S. operators is estimated to be $210,000 per year.

The 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.

For the reasons discussed above, I certify that this action (1) is not a " significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."

List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Safety.

Adoption of the Amendment
Accordingly, 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:

PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 USC 106(g), 40101, 40113, 44701

39.13 - [Amended]
2. Section 39.13 is amended by removing Amendment 39-4943 (49 FR 44093, November 2, 1984), and by adding a new airworthiness directive (AD), Amendment 39-9417, to read as follows: