On November 28, 2001 the FAA issued Emergency AD 2001-24-51 for MDHI Model 600N helicopters which requires, within 5 hours TIS, inspecting both upper tailboom attachments, nutplates and both angles for a crack or thread damage and repairing or replacing any cracked or damaged part before further flight. Also required is replacing the upper RH bolt with a new bolt, and if the upper RH bolt is broken, replacing the three remaining bolts with airworthy bolts before further flight. Adding a washer to each bolt and modifying both upper access covers are also required. Thereafter, at intervals not to exceed 25 hours TIS, inspecting the upper tailboom attachments and repairing or replacing any cracked part before further flight is required. That action was prompted by the discovery of a cracked bolt on a helicopter. Further inspection revealed cracking on bolts and attachments on several other helicopters. This condition, if not corrected, could result in failure ofa tailboom attachment, loss of the tailboom, and subsequent loss of control of the helicopter.
The FAA has reviewed MD Helicopters, Inc. Service Bulletin SB600N-036, dated November 2, 2001 (SB). The SB describes procedures for inspecting the tailboom attach fittings and repairing damaged fittings. In addition to those procedures, the FAA has determined that if one bolt is broken, all four bolts must be replaced. Also, we have determined that a 25-hour TIS repetitive inspection of the tailboom attachments is required.
Since the unsafe condition described is likely to exist or develop on other MDHI Model 600N helicopters of the same type design, the FAA issued Emergency AD 2001-24-51 to prevent failure of a tailboom attachment, loss of the tailboom, and subsequent loss of control of the helicopter. The AD requires the following:
Within 5 hours TIS:
Remove the tailboom fairing, tailboom, and both upper tailboom attachment access covers.
Using a light and a 10 x orhigher magnifying glass, inspect for a crack or damage:
Both upper tailboom attachments and nutplates. If a crack or thread damage is found, replace any cracked or damaged attachments or nutplates with an airworthy part before further flight.
Both angles. If a crack is found on the RH angle, before further flight, install a new clip. If a crack is found on the left-hand angle, before further flight, replace or repair the angle.
Replace the upper RH tailboom attachment bolt with a new bolt. If the upper RH bolt is found broken, before further flight, also replace the three remaining bolts.
Add a washer to each bolt.
Modify both upper access covers.
At intervals not to exceed 25 hours TIS, using a borescope, through the hole in each upper access cover, inspect the upper tailboom attachments for a crack. Repair or replace any cracked part with an airworthy part before further flight.
The actions must be accomplished in accordance with the SB described previously. The short compliance time involved is required because the previously described critical unsafe condition can adversely affect the structural integrity and controllability of the helicopter. Therefore, the previously stated actions are required within 5 hours TIS, and thereafter at the specified time intervals, and this AD must be issued immediately.
Since it was found that immediate corrective action was required, notice and opportunity for prior public comment thereon were impracticable and contrary to the public interest, and good cause existed to make the AD effective immediately by individual letters issued on November 28, 2001 to all known U.S. owners and operators of MDHI Model 600N helicopters. These conditions still exist, and the AD is hereby published in the Federal Register as an amendment to 14 CFR 39.13 to make it effective to all persons.
The FAA estimates that 33 helicopters of U.S. registry will be affected by this AD. It will take approximately 2 work hours per helicopter to perform the inspections, 8 work hours per helicopter to replace the bolts, if necessary, and 20 work hours to repair an angle, if necessary. The average labor rate is $60 per work hour. Required parts will cost $50 for each inspection, $200 to replace the bolts on each helicopter, and $100 to repair an angle. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $41,050 ($28,050 to inspect and replace the bolts on each helicopter and $13,000 to repair 10 helicopters).
Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice 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.
Comments 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 in the Rules Docket 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.
Commenters wishing the FAA to acknowledge receipt of their mailed comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement ismade: "Comments to Docket No. 2001-SW-57-AD." The postcard will be date stamped and returned to the commenter.
The regulations adopted herein will not have a substantial direct effect 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, it is determined that this final rule does not have federalism implications under Executive Order 13132.
The 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.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, 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 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding a new airworthiness directive to read as follows: