Since the issuance of that NPRM, we were notified that a crack was found on another T/R blade, P/N 212010750105 FM, installed on a Bell Model 412EP helicopter. The crack was discovered while the helicopter was on the ground during a scheduled visual inspection. The T/R blade is now being examined at the manufacturer's field investigation lab. The crack is located approximately in the center of the TR blade span and extends across the majority of the chord. The T/R blade had accumulated 2,076 hours TIS. Because P/N 212010750105 FM was not included in the applicability of the NPRM, and because a crack growth analysis using the striation count data from one of the failed T/R blades predicted a crack propagation rate of approximately 77 hours TIS from damage initiation to blade failure, we will withdraw that NPRM and issue this AD as a Final rule; request for comments. This AD contains the proposed requirements from the NPRM; however, we've included additional P/Ned blades and made other changes based on the comments to the NPRM. In response to the NPRM we received several comments from 4 commenters; the manufacturer, the Canadian National Defence Headquarters, and 2 individuals.

Two commenters suggest changing the compliance time for the proposed actions. One of the commenters suggests changing the proposed initial inspection from 25 hours TIS or 15 days to 25 hours TIS or 30 days and changing the recurring inspection from 25 hours TIS or 15 days to 25 hours TIS or 30 days. The other commenter believes that a visual inspection before the first flight of each day would be adequate and that a limit of 10 hours between visual inspections in any one day could be added. The same commenter states that it is not always practical (e.g. carrying a suitable safe ladder for conducting an adequate inspection and carry passengers) and might also be hazardous (e.g. doing an inspection from an offshore oil field platform where there is no ladder or stand available or where there is restricted space and the possibility of high wind speeds) to do a visual inspection before each engine start. Finally, one commenter, the manufacturer, states that it is impractical to require inspection of the T/R blades before each flight or engine start unless we are referring to a groundlevel visual inspection because a ladder, which is not available in the field, would be required for a handson inspection. It recommends an
[[Page 24860]]
inspection in accordance with the maintenance manual. The manufacturer further recommends an inspection for more than just ``cracks'', that is, any damage beyond limits in accordance with the published schedule and requirements in the maintenance manual.

We concur with the recommendation to change the initial and recurring inspections from 25 hours TIS or 15 days to 25 hours TIS or 30 days. The 15day interval was originally proposed because a corrosion pit was the initiation point for one of the failures and that interval is consistent with FAA advisory material relating to the detection of corrosion. Since the proposal was published, we have reevaluated the need for the interval and determined that a 30day interval is adequate for this inspection and the AD is revised accordingly. We do not concur that a visual inspection before the first flight of each day would be adequate and that a limit of 10 hours between visual inspections in any one day should be added. Additionally, we do not agree with the manufacturer that a 60day interval would be appropriate because of the quick degradation in the T/R blade strength. However, we do agree that it is not always practical to require a detailed visual inspection of the T/R blades using a ladder before each flight or engine start. The proposed owner/ operator (pilot) check was only intended to be a ``walk around'' check to detect any large cracks. Although the Canadian commenter states that their inspection from the ground is not considered effective, we have received reports that two cracked blades were discovered during checks performed from the ground. The initial and recurring inspections performed by a mechanic are detailed, upclose inspections.

One commenter also suggests that instead of requiring a mandatory daily log book entry stating compliance with the AD that ``the blade inspection be made a required preflight checklist item with no daily log book entry required.'' If a logbook entry is required, the commenter suggests that it be a separate entry made at the time the 25 hour is signed off. We have determined that this critical check needs to be mandated. This determination is based on the critical nature of this failure and that the length of a crack is predicted to grow quickly once it is detectable based on the service history of these T/R blades. All required inspections, including the pilot checks specifically approved by this AD, must be recorded at the time they are performed. That recording evidences that the required AD actions have been performed. If it is not recorded, the aircraft is not in compliance with the AD and is unairworthy.

In addition to comments regarding the inspection times and types, the manufacturer provided other comments to the NPRM. Those comments and our responses follow:
Comment Response The AD lists a 1991 Model 212 with a The cracked T/R blade in .75'' crack * * * that Bell questions question is found in the FAA since they have no conclusive service difficulty database. technical data on it. They also An approximate 8inch crack question our references to a 77 hour was found in the T/R blade crack propagation from striation count installed on a Bell Model 212 and state that the 77 hour value is helicopter during a daily actually from a crack growth analysis inspection. The crack was that simply includes striation count located 20.25 inches inboard data. Bell also states that they are from the tip of the T/R blade aware of only 4, not 8, existing running through a .75 inch M205Bs that are of FAA certified long smooth dent. The part configuration. number of the T/R blade was 212010750105 with a total time of 423 hours. We agree with the comment about the reference to the 77 hour crack propagation and the number of existing M205B helicopters and have revised this AD accordingly. The listed tail rotor dash numbers While the standard Model 204B appear to be incorrect. The Model 204B helicopter may not use this does not use the 212010750 tail particular T/R blade, the 212 rotor blade and there also appears to 010750 T/R blade may be on a be several of the later dash numbers modified Model 204B helicopter missing from various models. that does use this blade. To assure that we have covered all affected blades, the applicability now encompasses all affected dashnumbered T/R blades.
Recommend changing areas called out for Agree with this change and have special attention to Stations 25.0 to revised this AD accordingly. 35.0 (both sides) for damage/corrosion
and include inboard blade butt area
surrounding balance weights/screws for
cracks.
There have not been eight reported A crack in a blade makes that failures, there have been three. All blade unable to safely perform others are reported cracks in the its intended function. Thus, blade skin, not ``failures.'' The term there are now 9 T/R blades ``failure'' can be misleading. that meet that criteria. Bell objects to our statement in the As we understand this objection NPRM that ``The requirements of the by the manufacturer, it proposed AD would be interim actions believes that a redesigned until either a more rigorous blade is unnecessary and that inspection is developed or a new blade the current inspections are that is more damage tolerant is adequate. We do not agree. designed.'' Bell states ``Although we Based on the fracture are in concept discussions with DND, analysis, once the crack completion and certification of this reaches a size that is blade is many months away and could be detectable by inspection, it misleading to the commercial is predicted to grow quickly. community.'' Therefore, for the affected T/ R blades, it is critical to find a crack or damage that could lead to a crack at the earliest opportunity. The service history of these affected T/R blades has shown that the current inspections are inadequate to reveal these cracks before blade failure. One T/R blade failed and another one cracked because of manufacturing damage on the inside of the T/R blade. That damage was not initially detectable by external inspection. Another T/R blade failed during flight due to cracking that initiated from a corrosion pit in the leading edge spar that was too small to be readily detected. Therefore, replacing the affected T/R blades with a redesigned, more damage tolerant T/R blade is anticipated as terminating action for the requirements of this AD.

Another commenter, the Canadian National Defence Headquarters, views the proposed actions as a ``good first step'' but offers several recommendations. Those recommendations and our responses follow: [[Page 24861]]
Recommendation Response ``Promulgate to other aviation Our standard practice is to regulation agencies worldwide because send our ADs to aviation there are many more airframes affected authorities with which we have than the `388 helicopters of U.S. a bilateral agreement. In registry'.'' turn, it is then at their discretion whether or not to follow up with similar action. Adjust the inspection frequency as a We agree that the risk of function of the operations incurring damage in the T/R environment, e.g., a 12.5 hours blade would be less for those inspection frequency using the 10x helicopters operated on paved magnification (noting that deployments landing fields versus ``harsh of small numbers of aircraft take the & rough'' landing fields. minimum support equipment required) Defining and enforcing such an visual inspection for operations using inspection interval, however, ``harsh & rough'' landing fields and would be difficult because an interval of 25 hours inspection for helicopters operate in so many paved landing fields. varied environments. We believe the commet to use a 10 power magnifying glass may be a typographical error because the Canadian National Defense uses a 2power magnifying glass and a good source of light every 12.5 hours TIS for the visual inspection of the T/ R blades on their Model 412CF helicopters. Regardless, we have determined that a 25hour TIS inspection using a 3x or higher magnifying glass is best for the overall safe operation of these helicopters in the U.S.
Specify that the visual check be We do not believe that further carried out by an appropriately information regarding who can qualified person. carry out this visual check is necessary. The visual check is only intended to detect a largescale crack and we believe an owner/operator (pilot) is qualified to perform this ``walkaround'' function.
Define what constitutes a ``bright The illumination levels are light''. historically not given for visual inspections that are mandated by an AD. We believe what constitutes a bright light can be adequately determined by the individuals who are qualified to do the inspection. We also did not want to create additional calibration and recordkeeping requirements.
Implement damage mapping as a means to Inspection of the T/R blade increase detectability of new damage records and recording any and decrease the maintenance burden. damage found within the repair limits are in the maintenance instructions for the T/R blade inspection on the applicable helicopters. These steps are currently in the applicable maintenance procedures. Operators are free to implement such mapping if they believe it will reduce their maintenance burden. Carry out a Type 1, Method C, Level III We believe the requirement to dyepenetrant inspection in cases use of a 10power magnifying where difficulties are encountered in glass is adequate. determining the presence of a crack by
visual inspection.

We have reviewed the following Bell documents:

This unsafe condition is likely to exist or develop on other helicopters of these same type designs. Therefore, this AD is being issued to detect damage to a T/R blade that could lead to cracking of a T/R blade and subsequent loss of control of the helicopter. This AD requires:

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.

We estimate that this AD will affect 384 helicopters of U.S. registry. There
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are approximately 184 Model 205A and 205A1 helicopters, 4 Model 205B helicopters, 101 Model 212 helicopters, 80 Model 412, 412CF, and 412EP helicopters, and 15 modified Model 204B helicopters. Each visual check will take .125 hours, each visual inspection will take .5 hours, and 6 hours to remove and replace each T/R blade assembly, if necessary. The average labor rate is $80. Replacement parts will cost $11,243 for each T/R blade assembly. Based on these figures, the estimated cost impact of the AD for all of the affected models will be $1,828,855 assuming an average of 600 hours TIS per year for each helicopter resulting in 365 visual checks, 24 inspections, and 5 T/R blade assembly replacements for the total fleet.

Comments Invited

This AD is a final rule that involves requirements that affect flight safety and was not preceded by notice and an opportunity for public comment; however, we invite you to submit any written data, views, or arguments regarding this AD. Send your comments to an address listed under ADDRESSES. Include ``Docket No. FAA20080490; Directorate Identifier 2008SW26AD'' at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the AD. We will consider all comments received by the closing date and may amend the AD in light of those comments.

We will post all comments we receive, without change, to http:// www.regulations.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this AD. Using the search function of our docket Web site, you can find and read the comments to any of our dockets, including the name of the individual who sent the comment. You may review the DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 1947778).

Regulatory Findings

We have determined that this AD will not have federalism implications under Executive Order 13132. This AD 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.

For the reasons discussed above, I certify that the regulation:

1. Is not a ``significant regulatory action'' under Executive Order 12866;

2. Is not a ``significant rule'' under the 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.

We prepared an economic evaluation of the estimated costs to comply with this AD. See the AD docket to examine the economic evaluation. Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, Section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, ``General requirements.'' Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

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 to read as follows:
20081003 Bell Helicopter Textron: Amendment 3915509. Docket No. FAA20080490; Directorate Identifier 2008SW26AD.

Applicability

The following model helicopters, with the specified tail rotor blade assembly (T/R blade) installed, certificated in any category: With T/R blade, part number (P/ Helicopter model N)
204B, 205A, 205A1, 212, 412, 412CF, 212010750(all dash numbers). and 412EP.
205B................................... 212010750(all dash numbers). 212015501(all dash numbers). 210.................................... 210010001(all dash numbers). 212010750(all dash numbers). Compliance

Required as indicated.

To detect any damage in a T/R blade, prevent cracking of a T/R blade leading to failure from static overload, and subsequent loss of control of the helicopter, accomplish the following:
(a) Before each start of the engines, visually check both sides of each T/R blade for a crack. An owner/operator (pilot) holding at least a private pilot certificate may perform this visual check and must enter compliance with this paragraph into the aircraft maintenance records in accordance with 14 CFR 43.11 and
91.417(a)(2)(v).
(b) Within 25 hours timeinservice (TIS) or 30 days, whichever occurs first, unless accomplished previously, and thereafter at intervals not to exceed 25 hours TIS or 30 days, whichever occurs first:
(1) Clean each T/R blade by hand using a mild degreaser and water to remove soot and grime on both sides of the blade using a coarse, loosely woven cotton cloth in a spanwise direction. Use a cloth with a color that contrasts with the color of the T/R blade so that a snag will be visible.
(2) Using a 3power or higher magnifying glass and a bright light, visually inspect the T/R blade skins, leading edge spar, doublers, grip plates, and trailing edge for a crack, corrosion (may be indicated by blistering, peeling, flaking, bubbling, or cracked paint) and any other damage (including a nick, scratch, or dent). See Figure 1 of this AD. Pay particular attention to both sides of the T/R blade in the area located 16 to 26 inches from the T/R blade tip (blade station 25 to 35the T/R blade tip is located at blade station 51) and to the inboard blade butt area near the attachment of the external balance weights
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and screws. Also pay particular attention to any blade surface that was snagged by the cloth, as that may be an indication of a crack or paint chip that could lead to corrosion.
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[GRAPHIC] [TIFF OMITTED] TR06MY08.182
BILLING CODE 491013C
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(3) If any blistering, peeling, flaking, bubbling, or cracked paint is detected, remove the paint from the affected area and visually inspect the affected area for corrosion or a crack using a 10power or higher magnifying glass. If any corrosion is found, measure the depth of the corrosion (a digital optical micrometer is one tool that can be used for this measurement).
(4) If a nick, scratch, or dent is found, visually inspect for a crack using a 10power or higher magnifying glass and measure the depth of the damage (a digital optical micrometer is one tool that can be used for this measurement).
(c) Before further flight:
(1) Replace any T/R blade that has a crack with an airworthy blade.
(2) Replace any T/R blade that has any corrosion, nick, scratch, dent, or other damage that exceeds any maximum repair limit with an airworthy blade.

Note 1: The maximum repair limits are specified in the applicable maintenance manual.
(3) Repair or replace with an airworthy blade any T/R blade that has any corrosion, nick, scratch, dent or other damage that is within the maximum repair limits.

Note 2: The repair procedures are specified in the applicable maintenance manual and component repair and overhaul manuals. (d) 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 Manager, Rotorcraft Certification Office, Rotorcraft Directorate, FAA, ATTN: Michael Kohner, Aviation Safety Engineer, Fort Worth, Texas 761930170, telephone (817) 2225447, fax (817) 2225783, for information about previously approved alternative methods of compliance.
(e) This amendment becomes effective on May 21, 2008.

Issued in Fort Worth, Texas, on April 22, 2008.
Mark R. Schilling,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service. [FR Doc. E89790 Filed 5508; 8:45 am]
BILLING CODE 491013P

FOR FURTHER INFORMATION CONTACT Michael Kohner, Aviation Safety Engineer, FAA, Rotorcraft Directorate, Rotorcraft Certification Office, Fort Worth, Texas 761930170, telephone (817) 2225447, fax (817) 222 5783.