[Federal Register Volume 73, Number 88 (Tuesday, May 6, 2008)]
[Rules and Regulations]
[Pages 24858-24864]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-9790]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2008-0490; Directorate Identifier 2008-SW-26-AD;
Amendment 39-15509; AD 2008-10-03]
RIN 2120-AA64
Airworthiness Directives; Bell Helicopter 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 airworthiness 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 amendment 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 are intended 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.
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 Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue, 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,
telephone (817) 280-3391, fax (817) 280-6466.
Examining the Docket: You may examine the docket that contains the
[[Page 24859]]
AD, any comments, and other information on the Internet at http://www.regulations.gov, or in person at the Docket 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 Certification Office,
Fort Worth, Texas 76193-0170, telephone (817) 222-5447, fax (817) 222-
5783.
SUPPLEMENTARY INFORMATION: A proposal to amend 14 CFR part 39 to
include an AD for the specified model helicopters was published in the
Federal Register 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
cracking 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 assembly, part number (P/N) 212-010-750-009, -
105, and -107. Six of the cracks initiated between blade stations 30 to
33.5; one crack initiated at blade station 21.9; and one crack
initiated at blade station 27.6. Three of these T/R blades failed
during flight and all were installed on Bell Model 412 series
helicopters. In one of the in-flight failures, the T/R blade failed due
to a fatigue crack that initiated in the blade skin from a nick .060
inches long by .008 inches deep. The initial damage was above the
maximum allowable damage limit for the blade skin provided in the
maintenance manual. That failed blade had accumulated 1,478 hours time-
in-service (TIS). In another in-flight failure, a section of the T/R
blade separated from the helicopter during cruise flight at 5,500 feet.
The helicopter was reported to have violently turned down and to the
left. The helicopter ``leveled out'' at approximately 1,000 feet before
setting down in the water. The blade failed due to a cracked stainless
steel leading edge spar that originated from a corrosion pit .001
inches deep. The corrosion area extended .003 inches 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 investigation. The crack had initiated at
blade station 21.9 and the blade had accumulated 1,232 hours TIS. Also,
the following blades were found cracked:
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Blade Crack
Model Year P/N 212-010- Hours TIS station length Initial damage part Initial damage size
750- (in.) (in.) and type
--------------------------------------------------------------------------------------------------------------------------------------------------------
212................................. 1973 -009 3,224 32.2 6.5 Skin--Corrosion........ .030 in. wide.
212................................. 1985 -009 279 31.5 13.0 Spar--Manufacturing .090 in. wide.
Notch.
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.
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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, visually checking each
T/R blade for a crack;
Within 25 hours TIS or 15 days, whichever occurs first,
and thereafter at intervals not to exceed 25 hours TIS or 15 days,
whichever occurs first, cleaning and visually inspecting each T/R blade
for a crack, corrosion, nick, scratch, or dent using a 3-power or
higher magnifying glass and a bright light;
If certain damage is found, inspecting 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
repairing or replacing any otherwise unairworthy T/R blade.
Since the issuance of that NPRM, we were notified 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 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 212-010-750-105 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 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
[[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 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
detection 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 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 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 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, up-close 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:
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Comment Response
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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 8-inch 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
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 While the standard Model 204B
appear to be incorrect. The Model 204B helicopter may not use this
does not use the 212-010-750 tail particular T/R blade, the 212-
rotor blade and there also appears to 010-750 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 dash-numbered 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.
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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]]
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Recommendation Response
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``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 2-power 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 25-hour
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
large-scale crack and we
believe an owner/operator
(pilot) is qualified to
perform this ``walk-around''
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
dye-penetrant inspection in cases use of a 10-power 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:
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 inspection of
the T/R blades at specified inspection intervals;
That the blades must be cleaned in order to perform 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 February 6,
2003, which applies to Model 412CF helicopters and provides
instructions for doing a visual inspection of certain T/R blades
immediately and every 25 hours TIS in accordance with the Model 412CF
maintenance manual 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 and
specifies a tail rotor blade damage 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 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:
Before each start of the engines, visually checking 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 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 occurs 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 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) using a 3x or higher
magnifying glass.
If certain damage is found, inspecting 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 unairworthy T/R blade. The short compliance time
involved is required because a cracked 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 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
[[Page 24862]]
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 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. FAA-2008-0490; Directorate
Identifier 2008-SW-26-AD'' 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 19477-78).
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
0
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
0
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]
0
2. Section 39.13 is amended by adding a new airworthiness directive to
read as follows:
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 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, 205A-1, 212, 412, 412CF, 212-010-750-(all dash numbers).
and 412EP.
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 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 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 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 3-power 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 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
[[Page 24863]]
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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[[Page 24864]]
(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
10-power 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 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).
(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 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 Filed 5-5-08; 8:45 am]
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