1 [Federal Register: May 6, 2008 (Volume 73, Number 88)] [Rules and Regulations] [Page 24858-24864] From the Federal Register Online via GPO Access [wais.access.gpo.gov] [DOCID:fr06my08-4]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2008-0490; Directorate Id entifier 2008-SW-26-AD; Amendment 39-15509; AD 2008-10-03]

RIN 2120-AA64

Airworthiness Directives; Bell Helicopt er Textron Model 204B, 205A, 205A-1, 205B, 210, 212, 412, 412CF, and 412EP Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthine ss directive (AD) for the specified Bell Helicopter Textron (Bell) model helicopters. This action requires certain checks and inspections of each tail rotor blade assembly (T/R blade) at specified intervals and repairing or replacing, as applicable, any unairworthy T/R blade. This amendm ent is prompted by three failures of a T/R blade occurring during flight and a recent incident of a cracked T/R blade discovered during a scheduled visual inspection. The actions specified in this AD ar e intended to detect damage to a T/R blade that could lead to cracking of a T/R blade and s ubsequent loss of contro l of the helicopter.

DATES: Effective May 21, 2008.
Comments for inclusion in the Rules Docket must be received on or before July 7, 2008.

ADDRESSES: Use one of the following addresses to submit comments on this AD:

• Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.

• Fax: 202-493-2251.

• Mail: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.

• Hand Delivery: U.S. Department of Transporta tion, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Av enue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. You may get the service information identified in this AD from Bell Helicopter Textron, Inc., P.O. Box 482, Fort Worth, Texas 76101, te lephone (817) 280-3391, fax (817) 280-6466. Examining the Docket: You may examine the doc ket that contains the AD, any comments, and
other information on the Internet at http://www.regulations.gov, or in person at the Docket2 Operations office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Operations office (telephone (800) 647- 5527) is located in Room W12-140 on the ground floor of the West Building at the street address stated in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT: Michael Kohner, Aviation Safety Engineer, FAA, Rotorcraft Directorate, Rotorcraft Certific ation Office, Fort Worth, Texas 76193-0170, telephone (817) 222-5447, fax (817) 222-5783.

SUPPLEMENTARY INFORMATION: A proposal to amend 14 CFR pa rt 39 to include an AD for the specified model helicopters wa s published in the Federal Re gister as Docket No. FAA-2006- 26219, Directorate Identifier 2004-SW-49-AD on November 2, 2006 (71 FR 64484). That Notice of Proposed Rulemaking (NPRM) was prompted by eight reports of fatigue cr acking of T/R blades
installed on Bell Model 212 and 412 helicopters (three failures on the Bell Model 212 and five failures on the Bell Model 412) with a blade a ssembly, part number (P/N) 212-010-750-009, -105,
and -107. Six of the cracks initiate d between blade stations 30 to 33.5; one crack initiated at blade station 21.9; and one crack initia ted at blade station 27.6. Three of these T/R blades failed during flight and all were installed on Be ll Model 412 series helicopters. In one of the in-flight failures, the T/R blade failed due to a fatigue cr ack that initiated in the blade sk in from a nick .060 inches long by .008 inches deep. The initial damage was above th e maximum allowable damage limit for the bladeskin provided in the maintenance manual. That failed blade had accumulated 1,478 hours time-inservice (TIS). In another in-flight failure, a sec tion of the T/R blade separated from the helicopter during cruise flight at 5,500 feet. The helicopter was reported to ha ve violently turned down and to the left. The helicopter ''leveled out'' at approx imately 1,000 feet before setting down in the water.
The blade failed due to a cracked st ainless steel leading edge spar th at originated from a corrosion pit .001 inches deep. The corrosion area extended .003 in ches along the surface of the origin location. That blade had accumulated 4,643 hours TIS. In the third in-flight failure, sanding on the spar and chem-milling was found during a post-accident investig ation. The crack had initiated at blade station 21.9 and the blade had accumulated 1,232 hours TIS. Al so, the following blades were found cracked:

Model Year P/N 212-
010-750- Hours
TIS Blade
Station (in.) Crack Length (in) Initial Damage Part and Type Initial Damage Size

212 1973 -009 3,224 32.2 6.5 Skin – Corrosion .030 in. wide

212 1985 -009 279 31.5 13.0 Spar – Manufacturing
Notch .090 in. wide

212 1991 -105 423 30.8 8.0 Skin – Non Sharp Dent .75 in. long

412 1990 -009 3,876 27.6 8.0 Skin – Corrosion Unknown

412 1996 -105 1,235 30.0 8.3 Skin – Scratch .45 in. long by .005 in. deep

The NPRM proposed to require the following interim actions until either a more rigorous inspection is developed or a new blade that is more damage tolerant is designed:

• Before each start of the engines, visua lly checking each T/R blade for a crack;

• Within 25 hours TIS or 15 days, whichever occurs fi rst, and thereafter at intervals not to exceed 25 hours TIS or 15 days, whichever o ccurs first, cleaning and visually inspecting each T/R blade for a crack, corrosion, nick, scratch, or dent using a 3-power or higher magnifying gl ass and a bright light;3 • If certain damage is found, in specting for a crack or corrosion using a 10-power or higher magnifying glass and measuring the depth of any damage; and

• Before further flight, replacing any cracked T/R blade and repair ing or replacing any otherwise unairworthy T/R blade. Since the issuance of that NPRM, we were notif ied that a crack was found on another T/R blade, P/N 212-010-750-105 FM, installed on a Bell Model 412EP helicopter. The crack was discovered while the helicopter was on the gr ound during a scheduled visual inspection. The T/R blade is now being examined at the manufacturer's field investig ation lab. The crack is located approximately in the center of the TR blade span and extends acro ss the majority of the chord. The T/R blade had accumulated 2,076 hours TIS. Because P/N 212- 010-750-105 FM was not included in the applicability of the NPRM, and beca use a crack growth analysis usi ng the striation count data from one of the failed T/R blades predicted a crack pr opagation 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 c ontains the proposed requirement s 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 comm ents from 4 commenters; the manufacturer, the
Canadian National Defence Hea dquarters, and 2 individuals. Two commenters suggest changing the complia nce time for the proposed actions. One of the commenters suggests changing the proposed initial in spection from 25 hours TIS or 15 days to 25 hours TIS or 30 days and changing the recurring insp ection from 25 hours TIS or 15 days to 25 hours TIS or 30 days. The other commenter believes that a vi sual 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 al so be hazardous (e.g. doing an inspection from an offshore oil field platfo rm where there is no ladde r or stand available or where there is restricted space a nd the possibility of high wind speed s) to do a visual inspection before each engine start. Finally, one commenter, th e manufacturer, states th at it is impractical to require inspection of the T/R blades before each flight or engine start unless we are referring to a ground-level visual inspection because a ladder, which is not available in the field, would be required for a hands-on inspection. It recommends an inspect ion in accordance with the maintenance manual.
The manufacturer further r ecommends 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 recurr ing inspections from 25 hours TIS or 15 days to 25 hours TIS or 30 days . The 15-day 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 de tection of corrosion. Since the proposal was published,
we have reevaluated the need for the interval and determined that a 30-day interval is adequate for this inspection and the AD is revi sed accordingly. We do not concur th at 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 60-day 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 visu al inspection of the T/R blades using a ladder before each flight or engine start. The proposed ow ner/operator (pilot) check was only
intended to be a ''walk around'' check to detect any large cracks. Although the Canadian commenter states that their inspectio n from the ground is not considered effec tive, we have received reports that
two cracked blades were disc overed during checks performed from the ground. The initial and recurring inspections performed by a mechanic are detailed, up-close inspections. One commenter also suggests that instead of requiring a mandatory da ily 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 commente r suggests that it be a separate entry made at th e time the 25 hour is signed off. We have determined that this critical check4 needs to be mandated. This determination is based on the critical nature of th is 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, includi ng the pilot checks specifically approved by this AD, must be recorded at the time they are perfor med. That recording eviden ces 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 inspec tion 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 .75” crack ... that Bell questi ons since they have no conclusive technical data on it. They also question our references to a 77 hour crack propagation from striatio n count and state that the 77 hour value is actually from a crack growth analysis that simply includes striation
count data. Bell also states that they are aware of only 4, not 8, existing M205Bs that are of FAA certified configuration. The cracked T/R blade in question is found in the FAA service difficulty database. An approximate
8-inch crack was found in the T/R blade installed on a Bell Model 212 helicopter during a daily inspection. The crack was located 20.25 inches inboard from the tip of the T/R blade running through a .75 inch long smooth dent. The part
number of the T/R blad e was 212-010-750-105 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 appear to be
incorrect. The Model 204B does not use the
212-010-750 tail rotor blade and there also appears to be several of the later dash numbers missing from various models. While the standard Model 204B helicopter may not use this particular T/R blade, the 212-010-750 T/R blade may be on a modified Model 204B helicopter
that does use this blade. To assure that we have
covered all affected blad es, the applicability now encompasses all affected dash-numbered T/R
blades.

Recommend changing areas called out for special attention to Stations 25.0 to 35.0 (both sides) for damage/corrosion and include inboard blade butt area surrounding balance weights/screws for cracks. Agree with this change and have revised this AD accordingly.

There have not been eight reported failures, there have been three. All others are reported cracks in the blade skin, not “failures.” The term “failure” can be misleading. A crack in a blade makes that blade unable to safely perform its intended function. Thus, there are now
9 T/R blades that meet that criteria.5 Bell objects to our statement in the NPRM that “The requirements of the proposed AD
would be interim actions until either a more rigorous inspection is developed or a new blade that is more damage tolerant is designed.” Bell states “Although we are in concept discussions with DND, completion and certification of this blade is many months away and could be misleading to the commercial community.” As we understand this objection by the manufacturer, it believes th at a redesigned blade is unnecessary and that the current inspections are adequate. We do not agree. Based on the fracture analysis, once the crack reaches a size that is detectable by inspection, it is predicted to grow quickly. 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 recomm endations. Those recommendations and our responses
follow:

Recommendation Response

“Promulgate to other aviation regulation agencies worldwide because there are many
more airframes affected than the “388 helicopters of U.S. registry.” ” Our standard practice is to send our ADs to aviation
authorities with which we have a bilateral agreement. In turn, it is then at their discretion whether or not to follow up with similar action.

Adjust the inspection frequency as a function of the operations environment e.g., a 12.5 hours inspection frequency using the 10x magnification (noting that deployments of
small numbers of aircraft take the minimum support equipment required) visual inspection for operations using “harsh & rough” landing fields and an interval of 25 hours inspection for paved landing fields. We agree that the risk of incurring damage in the
T/R blade would be less for those helicopters operated on paved landing fi elds versus "harsh & rough" landing fields. De fining and enforcing such an inspection interval, however, would be difficult because helicopters operate in so many 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 2-power magnifying glass and a good source of light every 12.5 hours TIS fo r the visual inspection
of the T/R blades on thei r Model 412CF helicopters. Regardless, we have determined that a 25-hour TIS inspection using a 3x or hi gher magnifying glass is best for the overall safe operation of these helicopters in the U.S.6 Specify that the visual check be carried out by an appropriately qualified person. We do not believe that further information regarding who can carry out this visual check is necessary. The visual ch eck is only intended to detect a large-scale crack and we believe an owner/operator (pilot) is qualified to perform this
“walk-around” function.

Define what constitutes a “bright light.” The illu mination levels are historically not given for visual inspections that ar e 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 increase detectability of new damage and
decrease the maintenance burden. Inspection of the T/R blade records and recording any 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 dyepenetrant inspection in cases where difficulties are encountered in determining the presence of a crack by visual inspection. We believe the requirement to use of a 10-power magnifying glass is adequate.

We have reviewed the following Bell documents:

• Operations Safety Notice OSN 205-02-37, OSN 205B-02-10, OSN 212- 02-39, OSN 412-02-25, OSN 412CF-02-05, and OSN UH-1H-II-02-3, dated August 27, 2002. These Operations Safety Notices apply to all owners and operators of Bell 205, 205B, 212, 412, 412CF, and UH-1H-II helicopters and were written to remind operators of the following:

• The importance of accomplishing a complete inspecti on of the T/R blades at specified inspection intervals;

• That the blades must be cleaned in order to pe rform an adequate visual inspection to determine their condition; and

• That maintenance manuals and component repair and overhaul manuals are to be consulted for damage limits and repair criteria as required.

• Alert Service Bulletin No. 412CF-03-20, dated Fe bruary 6, 2003, which applies to Model 412CF helicopters and provides in structions for doing a visual inspecti on of certain T/R blades immediately and every 25 hours TIS in accordance with the Model 412CF maintenance ma nual and instructions for sending the affected tail rotor blade to DND ''Calgary Supply Center '' for refinishing and
reidentification.

• Bell Maintenance Document C-12-146-000/MF- 001, Mod 4, dated February 12, 2004, which applies to Model 412CF helicopters a nd specifies a tail rotor blade da mage records check and a visual inspection for dents, nicks, cracks, paint chips, or blisters using a 2-power magnifying glass and a good source of light in specified areas of the tail rotor blades (reference 64-00-00, section 64-38, page 42). This unsafe condition is likely to exist or de velop on other helicopters of these same type designs. Therefore, this AD is bei ng 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:7 • Before each start of the engines, visually check ing each T/R blade for a crack. An owner/operator (pilot) holding at least a private pilot certificat e may perform this visual check and must enter compliance with paragraph (a) of this AD into the aircraft maintenance records in accordance with 14 CFR 43.11 and 91.417(a)(2)(v). A pilot may do this check because it requires no special tools and can be performed equally well by a pilot or a mechanic.

• Within 25 hours TIS or 30 days, whichever occu rs first, unless accomplished previously, and
thereafter at intervals not to exceed 25 hours TIS or 30 days, whichever occurs first, cleaning and visually inspecting the T/R blade skins, leading edge spar, doublers, grip plat es, 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) using a 3x or hi gher magnifying glass.

• If certain damage is found, in specting the affected area using a 10-power or higher magnifying glass and measuring the depth of the damage.

• Before further flight, repairing or replacing, as applicable, any una irworthy T/R blade. The short compliance time involved is required because a cr acked or damaged T/R blade creates an unsafe condition that can adversely affect the structural integrity and controllability of the helicopter. Therefore the required actions within the specified short time intervals require that this AD be issued immediately.
Since a situation exists that requires the immediate adopti on of this regulation, it is found that notice and opportunity for prior publ ic 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 helicop ters of U.S. registry. There are approximately 184 Model 205A and 205A-1 helicopters, 4 Model 205B helicopters, 101 Model 212 helicopters, 80 Model 412, 412CF, and 412EP helicopters, and 15 modi fied Model 204B helicopters. Each visual check will take .125 hours, each visual inspecti on will take .5 hours, and 6 hours to remove and replace each T/R blade assembly, if necessary. The average labor ra te is $80. Replacement parts will cost $11,243 for each T/R blade assembly. Based on th ese 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 chec ks, 24 inspections, and 5 T/R blade assembly replacements for the total fleet.

Comments Invited

This AD is a final rule that involves requirement s that affect flight safe ty and was not preceded by notice and an opportunity for publ ic 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 N o. FAA-2008-0490; Directorate Iden tifier 2008-SW-26-AD'' at the beginning of your comments. We specifically invi te 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, withoutchange, 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 se arch function of our docket Web site, you can find and read the comments to any of our dockets, including the na me of the individual who sent the comment. You may review the DOT's complete Privacy Act Statement in the Federal Register published on Ap ril 11, 2000 (65 FR 19477-78).

Regulatory Findings

We have determined that this AD will not ha ve federalism implications under Executive Order
13132. This AD will not have a substantial direct eff ect on the States, on the relationship between the national Government and the States, or on the di stribution of power and responsibilities among the various levels of government.8 For the reasons discussed above, I certify that the regulation: 1. Is not a ''significant regulator y action'' under Executive Order 12866; 2. Is not a ''significant rule'' under the DOT Re gulatory 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 und er the authority described in Subt itle VII, Part A, Subpart III, Section 44701, ''General requirements.'' Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in ai r 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 becau se it addresses an unsafe condition that is likely to exist or develop on products iden tified 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 Av iation 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.

§ 39.13 [Amended]

2. Section 39.13 is amended by adding a new airw orthiness directive to read as follows:9 

### FAA
Aircraft Certification Service 

## AIRWORTHINESS DIRECTIVE

www.faa.gov/aircraft/safety/alerts/ www.gpoaccess.gov/fr/advanced.html

2008-10-03 Bell Helicopter Textron: Amendment 39-15509. Docket No. FAA-2008-0490;
Directorate Identifier 2008-SW-26-AD.

Applicability

The following model helicopters, with the speci fied tail rotor blade assembly (T/R blade) installed, certificated in any category:

Helicopter Model With T/R Blade, Part Number (P/N)

204B, 205A, 205A-1, 212, 412, 412CF, and 412EP 212-010-750- (all dash numbers)

205B 212-010-750- (all dash numbers) 212-015-501- (all dash numbers)

210 210-010-001- (all dash numbers) 212-010-750- (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 contro l 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 certific ate may perform this visual check and must enter compliance with this paragraph into th e aircraft maintenance records in accordance with 14 CFR 43.11 and 91.417(a)(2)(v).

(b) Within 25 hours time-in-service (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 de greaser and water to remove soot and grime on both sides of the blade using a coarse, loosely wove n cotton cloth in a spanwi se 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 3-power or higher ma gnifying 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, fl aking, 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 in ches from the T/R blade tip (blade station 25 to 35–the 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 and screws. Also pay particular a ttention to any blade surface that was snagged by the cloth, as that may be an indication of a cr ack or paint chip that could lead to corrosion.10 1. Pitch Horn Blade Bolts
2. Blade Grip Bolt Holes
3. External Balance Weights
4. Doubler
5. Trailing Edge
6. Skin
7. Honeycomb Core
8. Tip Block
9. Balance Screws
10. Spar
11. Grip Plate
12. Drain Hole Doubler
13. Butt Block
14. Inner Grip Plate
15. Tip Closure

T/R Blade Assembly Figure 1

(3) If any blistering, peeling, flaking, bubbling, or cracked paint is detected, remove the paint from the affected area and visually inspect the aff ected area for corrosion or a crack using a 10-power or higher magnifying glass. If any corrosion is f ound, 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, visual ly inspect for a crack us ing a 10-power 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).11 (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 corrosi on, nick, scratch, dent, or other damage that exceeds any maximum repair limit with an airworthy blade.

Note 1: The maximum repair limits are speci fied 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 w ithin the maximum repair limits.

Note 2: The repair procedures are specifi ed in the applicable maintenance manual and component repair and overhaul manuals.

(d) To request a different method of complian ce or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Contact th e Manager, Rotorcraft Certification Office, Rotorcraft Directorate, FAA, ATTN: Michael Kohne r, Aviation Safety Engineer, Fort Worth, Texas 76193-0170, telephone (817) 222-5447, fax (817) 222- 5783, 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. E8-9790 File d 5-5-08; 8:45 am]