That action was prompted by two accidents that occurred in Australia and Israel that were attributed to failure of a blade. Investigation revealed that corrosion from water penetration initiated a fatigue crack in a blade. Information from the accident
investigations revealed that the cracked blades manifested an increase in helicopter vibration. Following a trackandbalance of the blades, the vibrations would go back to normal for a short time and then slowly increase again until blade failure occurred. That condition, if not corrected, could result in a fatigue crack, blade failure, and subsequent loss of control of the helicopter.

Since issuing that AD, several commenters have called regarding the following issues:

These changes justify issuing this superseding AD instead of publishing Emergency AD 20040652 as a Final Rule in the Federal Register.

Since an unsafe condition has been identified that is likely to exist or develop on other Robinson Model R22 helicopters of the same type design, this AD supersedes AD 20040652 to require:

The short compliance time involved is required because the previously described critical unsafe condition can adversely affect the controllability and structural integrity of the helicopter. Therefore, the previously stated actions are required within a short timeframe and this AD must be issued immediately.

Since a situation exists that requires the immediate adoption of this regulation, 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.

The FAA estimates that this AD will affect 923 helicopters of U.S. registry. Trackandbalancing the blades, revising the component history card and maintenance manual, determining the age of each blade, and replacing blades, if necessary, will take approximately 11 work hours per helicopter to accomplish at an average labor rate of $65 per work hour. Required parts will cost approximately $25,000 (for 2 blades) per helicopter. Based on these figures, we estimate the total cost impact of the AD on U.S. operators to be $7,584,945, assuming that most blades currently in service reach the TIS retirement life before reaching the calendar retirement life, and that at most, 277 helicopters will need their blades replaced.

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
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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 FAApublic contact concerned with the substance of this AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a selfaddressed, stamped postcard on which the following statement is made: ``Comments to Docket No. 2004SW15AD.'' 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, 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 39AIRWORTHINESS 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 (AD), Amendment 3913803, to read as follows:
20041909 Robinson Helicopter Company: Amendment 3913803. Docket No. 2004SW15AD. Supersedes Emergency AD 20040652, Docket No. 2004SW01AD.

Applicability: Model R22series helicopters, with a main rotor blade (blade), part number (P/N) A0161 or A0162, installed, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent a fatigue crack, blade failure, and subsequent loss of control of the helicopter, accomplish the following:
(a) Within 10 hours timeinservice (TIS) or 30 days, whichever occurs first, for helicopters with blades, P/N A0162, that are 5 or more years old, or have 1,000 or more hours TIS, trackandbalance the blades. If an abnormal increase in vibration occurs within 5 hours TIS after the last track and balance, before further flight, replace the blades with airworthy blades, P/N A0162, that are less than 10 years old and have less than 2,200 hours TIS, or airworthy blades, P/N A0164, that are less than 12 years old and have less than 2,200 hours TIS.
(b) Within 10 hours TIS or 30 days, whichever occurs first, for helicopters with blades, P/N A0161, replace the blades with airworthy blades, P/N A0162 or A0164.
(c) Within 10 hours TIS or 30 days, whichever occurs first, determine the age of each blade:
(1) For a zerohour TIS (new) blade delivered with an
Airworthiness Approval tag, the time begins on the date stated on that tag. For a blade older than 9 years that predates the use of the Airworthiness Approval tag and was delivered as a new blade with a ``yellow tag,'' the time begins on the date stated on that tag. Any subsequent yellow tag issued for a blade after the blade was placed into service is not valid for determining the original manufacture date.
(2) For a new blade that has neither an Airworthiness Approval tag nor a yellow tag because it was delivered on a factorynew helicopter, the time begins on the date stated on the original Airworthiness Certificate as documented in the aircraft maintenance records.
(3) For a new blade installed on an overhauled helicopter, the time begins on the date the helicopter was returned to service after overhaul as documented in the aircraft logbook or work report. (4) For all other blades, the time begins on the date of manufacture. This date can be obtained from the manufacturer by providing them the serial number and part number.
(d) Within 10 hours TIS or 30 days, whichever occurs first, for helicopters with blades, P/N A0162, replace the blades with airworthy blades on or before reaching 2,200 hours TIS or 10 years, whichever occurs first.
(e) Within 10 hours TIS or 30 days, whichever occurs first, revise the component history card or equivalent maintenance record for blades, P/N A0162, by adding a 10year retirement life to the current 2,200 hours TIS retirement life.
(f) Revise the Airworthiness Limitations section of the applicable maintenance manual by adding a new retirement life of 10 years to the current 2,200 hours TIS retirement life for blades, P/N A0162.

Note: Robinson Model R22 Maintenance Manual, dated January 16, 2004, contains the revised Airworthiness Limitations section. (g) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Contact the Los Angeles Aircraft Certification Office, Transport Airplane Directorate, FAA, for information about previously approved alternative methods of compliance.
(h) Special flight permits will not be issued.
(i) This amendment becomes effective on October 7, 2004.

Issued in Fort Worth, Texas, on September 16, 2004. David A. Downey,
Manager, Rotorcraft Directorate, Aircraft Certification Service. [FR Doc. 0421269 Filed 92104; 8:45 am]
BILLING CODE 491013P

FOR FURTHER INFORMATION CONTACT Fred Guerin, Aviation Safety Engineer, FAA, Los Angeles Aircraft Certification Office, Airframe Branch, 3960 Paramount Blvd., Lakewood, California 90712, telephone (562) 6275232, fax (562) 6275210.