Document ID: FAA-2013-0725-0004
Agency: faa
Document Type: Rule
Title: Airworthiness Directives: Maule Aerospace Technology, Inc. Airplanes
Posted Date: 2013-12-16T05:00Z

[Federal Register Volume 78, Number 241 (Monday, December 16, 2013)]
[Rules and Regulations]
[Pages 76035-76040]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2013-29682]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2013-0725; Directorate Identifier 98-CE-01-AD; 
Amendment 39-17690; AD 98-15-18 R1]
RIN 2120-AA64

Airworthiness Directives; Maule Aerospace Technology, Inc. 
Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: We are revising Airworthiness Directive (AD) 98-15-18 that 
applies to certain Maule Aerospace Technology, Inc. Models M-4, M-5, M-
6, M-7, MT-7, MX-7, MXT-7, and M-8 airplanes that are equipped with 
rear wing lift struts, part number (P/N) 2079E, and/or front wing lift 
struts, P/N 2080E. AD 98-15-18 required repetitively inspecting certain 
wing lift struts for internal corrosion and replacing of any wing lift 
strut where corrosion was found. Since we issued AD 98-15-18, we were 
informed by the manufacturer that Model MXT-7-420 airplanes are no 
longer in existence, are no longer type certificated, and should be 
removed from the Applicability section. We were also informed that 
paragraph (b) in AD 98-15-18 had been misinterpreted and caused 
confusion. This AD removes Model MXT-7-420 airplanes from the 
Applicability section and clarifies the intent of the language in 
paragraph (b) of AD 98-15-18. This AD also retains all other 
requirements of AD 98-15-18. We are issuing this AD to correct the 
unsafe condition on these products.

DATES: This AD is effective January 21, 2014.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of January 26, 
1996 (61 FR 623, January 9, 1996).

ADDRESSES: For service information identified in this AD, contact Maule 
Air, Inc., 2099 GA Hwy 133 South, Moultrie, Georgia 31768; telephone: 
(229) 985-2045; fax: (229) 890-2402; Internet: http://www.mauleairinc.com/pdf/servicebulletins/service_bulletin_11_old.pdf. You may review copies of the referenced service information at 
the FAA, Small Airplane Directorate, 901 Locust, Kansas City, Missouri 
64106. For information on the availability of this material at the FAA, 
call (816) 329-4148.

[[Page 76036]]

Examining the AD Docket

    You may examine the AD docket on the Internet at http://www.regulations.gov by searching for and locating it in Docket No. FAA-
2013-0725; or in person at the Docket Management Facility between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD 
docket contains this AD, the regulatory evaluation, any comments 
received, and other information. The address for the Docket Office 
(phone: 800-647-5527) is Document Management Facility, U.S. Department 
of Transportation, Docket Operations, M-30, West Building Ground Floor, 
Room W12-140, 1200 New Jersey Avenue SE., Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: Gregory ``Keith'' Noles, Aerospace 
Engineer, FAA, Atlanta Aircraft Certification Office, 1701 Columbia 
Avenue, College Park, Georgia 30337; phone: (404) 474-5551; fax: (404) 
474-5606; email: gregory.noles@faa.gov.

SUPPLEMENTARY INFORMATION: 

Discussion

    We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR 
part 39 to revise AD 98-15-18, Amendment 39-10669 (63 FR 39018, July 
21, 1998), (``AD 98-15-18''). AD 98-15-18 was also reissued with a 
correction on September 18, 1998 (63 FR 51520, September 28, 1998). AD 
98-15-18 applied to the specified products. The NPRM published in the 
Federal Register on August 13, 2013 (78 FR 49207). The NPRM proposed to 
retain all requirements of AD 98-15-18, remove Model MXT-7-420 
airplanes from the Applicability section, and clarify our intent of 
required actions if the seal on a sealed wing lift strut is ever 
improperly broken.

Comments

    We gave the public the opportunity to participate in developing 
this AD. We received no comments on the NPRM (78 FR 49207, August 13, 
2013) or on the determination of the cost to the public.

Conclusion

    We reviewed the relevant data and determined that air safety and 
the public interest require adopting this AD as proposed except for 
minor editorial changes. We have determined that these minor changes:
     Are consistent with the intent that was proposed in the 
NPRM (78 FR 49207, August 13, 2013) for correcting the unsafe 
condition; and
     Do not add any additional burden upon the public than was 
already proposed in the NPRM (78 FR 49207, August 13, 2013).

Costs of Compliance

    We estimate that this AD affects 1,196 airplanes of U.S. registry.
    We estimate the following costs to comply with this AD. However, 
the only difference in the costs presented below and the costs 
associated with AD 98-15-18 is the change in the labor rate from $65 
per hour to $85 per hour.

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                Cost on U.S.
            Action                    Labor cost           Parts cost    Cost per product        operators
----------------------------------------------------------------------------------------------------------------
Inspection of the wing lift     11 x $85 per hour =                $40   $975 per          $1,166,100 per
 struts.                         $935 per inspection                      inspection        inspection cycle.
                                 cycle.                                   cycle.
----------------------------------------------------------------------------------------------------------------

    We estimate the following costs to do any necessary replacements 
that will be required based on the results of the inspection. We have 
no way of determining the number of airplanes that might need these 
replacements:

                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                  Action                      Labor cost per wing lift strut     Parts cost per    product per
                                                                                wing lift strut  wing lift strut
----------------------------------------------------------------------------------------------------------------
Replacement of the wing lift strut........  5 work-hours x $85 per hour = $425            $500             $925
----------------------------------------------------------------------------------------------------------------

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.

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 this AD:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866,
    (2) Is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979),
    (3) Will not affect intrastate aviation in Alaska, and
    (4) 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.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA amends 14 CFR part 39 as follows:

[[Page 76037]]

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. The FAA amends Sec.  39.13 by removing Airworthiness Directive (AD) 
98-15-18, Amendment 39-10669 (63 FR 39018, July 21, 1998), and adding 
the following new AD:

98-15-18 R1 Maule Aerospace Technology, Inc.: Amendment 39-17690; 
Docket No. FAA-2013-0725; Directorate Identifier 98-CE-01-AD.

(a) Effective Date

    This AD is effective January 21, 2014.

(b) Affected ADs

    This AD revises AD 98-15-18, Amendment 39-10669 (63 FR 39018, 
July 21, 1998), which superseded AD 95-26-18, Amendment 39-9476 (61 
FR 623, January 9, 1996.)

(c) Applicability

    This AD applies to the following Maule Aerospace Technology, 
Inc. airplanes, all serial numbers, identified in figure 1 of 
paragraph (c) of this AD, that are:
    (1) Equipped with original equipment manufacturer (OEM) Maule 
Aerospace Technology, Inc. rear wing lift struts, part number (P/N) 
2079E (or FAA-approved equivalent part numbers), and/or front wing 
lift struts, P/N 2080E (or FAA-approved equivalent part numbers), 
excluding airplanes equipped with four Maule sealed lift struts, P/N 
2200E and P/N 2201E, which are identified by two raised weld spots 
on the upper end of the strut just below the serial number plate. 
Removal of the upper cuff is needed to locate the weld spots; and
    (2) certificated in any category.

                               Figure 1 to Paragraph (c) of This AD--Applicability
----------------------------------------------------------------------------------------------------------------
 
----------------------------------------------------------------------------------------------------------------
                                                     Models
----------------------------------------------------------------------------------------------------------------
Bee Dee M-4            M-4                    M-4C                   M-4S                   M-4T
M-4-180C               M-4-180S               M-4-180T               M-4-210                M-4-210C
M-4-210S               M-4-210T               M-4-220                M-4-220C               M-4-220S
M-4-220T               M-5-180C               M-5-200                M-5-210C               M-5-210TC
M-5-220C               M-5-235C               M-6-180                M-6-235                M-7-235
M-7-235A               M-7-235B               M-7-235C               MT-7-235               MX-7-160
MX-7-180               MX-7-180A              MX-7-180B              MX-7-235               MX-7-420
MXT-7-160              MXT-7-180              MXT-7-180A             M-8-235
----------------------------------------------------------------------------------------------------------------

(d) Subject

    Joint Aircraft System Component (JASC)/Air Transport Association 
(ATA) of America Code 57, Wings.

(e) Unsafe Condition

    (1) The subject of this AD was originally prompted by reports of 
corrosion damage found on the wing lift struts. We are revising AD 
98-15-18, Amendment 39-10669 (63 FR 39018, July 21, 1998), because 
of reports that the language in paragraph (b) had been 
misinterpreted and caused confusion. Since we issued AD 98-15-18, we 
were informed by the manufacturer that Model MXT-7-420 airplanes are 
no longer in existence, are no longer type certificated, and should 
be removed from the Applicability section. This AD removes Model 
MXT-7-420 airplanes from the Applicability section and clarifies the 
intent of the language in paragraph (b) of AD 98-15-18, which is 
being removed by this AD.
    (2) This AD clarifies the FAA's intention that if a sealed wing 
lift strut assembly is installed as a replacement part, the 
repetitive inspection requirement is terminated only if the seal is 
never improperly broken. If the seal is improperly broken, then that 
wing lift strut becomes subject to continued repetitive inspections. 
We did not intend to promote drilling holes into or otherwise 
unsealing a sealed strut. This AD retains all the actions required 
in AD 98-15-18 and does not add any actions over that already 
required in AD 98-15-18. This AD does not add any additional burden 
to the owners/operators of the affected airplanes.
    (3) We are issuing this AD to detect and correct corrosion on 
the front and rear wing lift struts, which could cause the wing lift 
strut to fail. This failure could result in the wing separating from 
the airplane.

 (f) Paragraph Designation Changes to AD 98-15-18

    Since AD 98-15-18, Amendment 39-10669 (63 FR 39018, July 21, 
1998), was issued, the AD format has been revised, and certain 
paragraphs have been rearranged. As a result, the corresponding 
paragraph identifiers have changed in this AD, as listed in the 
following table:

   Table 1 to Paragraph (f) of This AD--Revised Paragraph Identifiers
------------------------------------------------------------------------
                                     Corresponding  requirement  in this
     Requirement in AD 98-15-18                       AD
------------------------------------------------------------------------
             paragraph (a)                        paragraph (h)
          paragraph (a)(1)                     paragraph (i)(1)
       paragraph (a)(1)(i)                  paragraph (i)(1)(i)
      paragraph (a)(1)(ii)                 paragraph (i)(1)(ii)
          paragraph (a)(2)                     paragraph (i)(2)
       paragraph (a)(2)(i)                  paragraph (i)(2)(i)
      paragraph (a)(2)(ii)                 paragraph (i)(2)(ii)
          paragraph (a)(3)                     paragraph (j)(1)
  paragraph (a)(4) and (c)                     paragraph (j)(2)
             paragraph (b)                              Removed
------------------------------------------------------------------------

(g) Compliance

    Unless already done (compliance with AD 98-15-18, Amendment 39-
10669 (63 FR 39018, July 21, 1998)), do the following actions within 
the compliance times specified in paragraphs (h) through (j) of this 
AD, including all subparagraphs. Properly unsealing and resealing a 
sealed wing lift strut is still considered a terminating action for 
the repetitive inspection requirements of this AD as long as all 
appropriate regulations and issues are considered, such as static 
strength, fatigue, material effects, immediate and long-term 
(internal and external) corrosion protection, resealing methods, 
etc. Current FAA regulations in 14 CFR 43.13(b) specify that 
maintenance performed will result in the part's condition to be at 
least equal to its original or properly altered condition. Any 
maintenance actions that unseal a sealed wing lift strut should be 
coordinated with the Atlanta Aircraft Certification Office (ACO) 
through the local airworthiness authority (e.g., Flight Standards 
District Office). There are provisions in paragraph (k) of this AD 
for approving such actions as an alternative method of compliance 
(AMOC).

 (h) Remove Wing Lift Struts

    At whichever of the compliance times specified in paragraphs 
(h)(1), (h)(2), or (h)(3) of this AD that occurs later, remove the 
wing lift struts following the INSTRUCTIONS section in PART I of 
Maule Service Bulletin (SB) No. 11, dated October 30, 1995. Before 
further flight after the removal, do the actions in one of the 
following paragraphs (i)(1), (i)(2), (j)(1), or (j)(2) of this AD, 
including all subparagraphs.
    (1) Upon accumulating 2 years time-in-service on an OEM Maule 
wing lift strut, P/N 2079E and/or P/N 2080E;
    (2) Within 3 calendar months after September 9, 1998 (the 
effective date retained from AD 98-15-18, Amendment 39-10669 (63 FR 
39018, July 21, 1998)); or
    (3) Within 2 years after the last inspection done in accordance 
with AD 95-26-18, Amendment 39-9476 (61 FR 623, January 9, 1996) 
(which was superseded by AD 98-15-18).

 (i) Inspect Wing Lift Struts

    Before further flight after the removal required in paragraph 
(h) of this AD, inspect

[[Page 76038]]

each wing lift strut following paragraph (i)(1) or (i)(2) of this 
AD, including all subparagraphs, or do the wing lift strut 
replacement following one of the options in paragraph (j)(1) or 
(j)(2) of this AD.
    (1) Inspect each wing lift strut for corrosion and perceptible 
dents following the INSTRUCTIONS section in PART I of Maule SB No. 
11, dated October 30, 1995.
    (i) If no corrosion is visible and no perceptible dents are 
found on any wing lift strut during the inspection required in 
paragraph (i)(1) of this AD, before further flight, apply corrosion 
inhibitor to each wing lift strut following the INSTRUCTIONS section 
in PART I of Maule SB No. 11, dated October 30, 1995. Repetitively 
thereafter inspect each wing lift strut at intervals not to exceed 
24 calendar months following the procedures in paragraph (i)(1) or 
(i)(2) of this AD, including all subparagraphs.
    (ii) If corrosion or perceptible dents are found on any wing 
lift strut during the inspection required in paragraph (i)(1) of 
this AD or during any repetitive inspection required in paragraph 
(i)(1)(i) of this AD, before further flight, replace the affected 
wing lift strut with one of the replacement options specified in 
paragraph (j)(1) or (j)(2) of this AD. Do the replacement following 
the procedures specified in those paragraphs, as applicable.
    (2) Inspect each wing lift strut for corrosion following the 
procedures in the Appendix to this AD. This inspection must be done 
by a Level 2 or Level 3 inspector certified using the guidelines 
established by the American Society for Non-destructive Testing or 
the ``Military Standard for Nondestructive Testing Personnel 
Qualification and Certification'' (MIL-STD-410E), which can be found 
on the Internet at http://aerospacedefense.thomasnet.com/Asset/ MIL-
STD-410.pdf.
    (i) If no corrosion is found on any wing lift strut during the 
inspection required in paragraph (i)(2) of this AD and all 
requirements in the Appendix to this AD are met, before further 
flight, apply corrosion inhibitor to each wing lift strut following 
the INSTRUCTIONS section in PART I of Maule SB No. 11, dated October 
30, 1995. Repetitively thereafter inspect each wing lift strut at 
intervals not to exceed 24 calendar months following the procedures 
in paragraph (i)(1) or (i)(2) of this AD, including all 
subparagraphs.
    (ii) If corrosion is found on any wing lift strut during the 
inspection required in paragraph (i)(2) of this AD or during any 
repetitive inspection required in paragraph (i)(2)(i) of this AD, or 
if any requirement in the Appendix of this AD is not met, before 
further flight after any inspection in which corrosion is found or 
the Appendix requirements are not met, replace the affected wing 
lift strut with one of the replacement options specified in 
paragraph (j)(1) or (j)(2) of this AD. Do the replacement following 
the procedures specified in those paragraphs, as applicable.

 (j) Wing Lift Strut Replacement Options

    Before further flight after the removal required in paragraph 
(h) of this AD, replace the wing lift struts following one of the 
options in paragraph (j)(1) or (j)(2) of this AD, or inspect each 
wing lift strut following paragraph (i)(1) or (i)(2) of this AD, 
including all subparagraphs.
    (1) Install OEM Maule P/N wing lift struts (or FAA-approved 
equivalent part numbers) that have been inspected following the 
procedures in either paragraph (i)(1) or (i)(2) of this AD, 
including all subparagraphs, and are found to be airworthy. Do the 
installations following the INSTRUCTIONS section in PART II of Maule 
SB No. 11, dated October 30, 1995. Repetitively thereafter inspect 
the newly installed wing lift struts at intervals not to exceed 24 
calendar months following the procedures in either paragraph (i)(1) 
or (i)(2) of this AD, including all subparagraphs.
    (2) Install new Maule sealed wing lift struts, P/N 2200E or P/N 
2201E, as applicable (or FAA-approved equivalent part numbers) 
following the INSTRUCTIONS section in PART II of Maule SB No. 11, 
dated October 30, 1995. Installing one of these new sealed wing lift 
strut assemblies terminates the repetitive inspection requirements 
in paragraphs (i)(1) or (i)(2) of this AD, including all 
subparagraphs, for that wing lift strut assembly.

 (k) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Atlanta ACO, FAA, has the authority to approve 
AMOCs for this AD, if requested using the procedures found in 14 CFR 
39.19. In accordance with 14 CFR 39.19, send your request to your 
principal inspector or local Flight Standards District Office, as 
appropriate. If sending information directly to the manager of the 
ACO, send it to the attention of the person identified in the 
Related Information section of this AD.
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the local flight standards district office/certificate holding 
district office.
    (3) AMOCs approved for AD 98-15-18, Amendment 39-10669 (63 FR 
39018, July 21, 1998) and AD 95-26-18, Amendment 39-9476 (61 FR 623, 
January 9, 1996) are approved as AMOCs for this AD.

 (l) Related Information

    For more information about this AD, contact Gregory K. Noles, 
Aerospace Engineer, FAA, Atlanta ACO, 1701 Columbia Avenue, College 
Park, Georgia 30337; phone: (404) 474-5551; fax: (404) 474-5606; 
email: gregory.noles@faa.gov.

(m) Material Incorporated by Reference

    (1) The Director of the Federal Register approved the 
incorporation by reference (IBR) of the service information listed 
in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.
    (2) You must use this service information as applicable to do 
the actions required by this AD, unless the AD specifies otherwise.
    (3) The following service information was approved for IBR on 
January 26, 1996 (61 FR 623, January 9, 1996).
    (i) Maule Service Bulletin No. 11, dated October 30, 1995.
    (ii) Reserved.
    (4) For Maule Aerospace Technology, Inc. service information 
identified in this AD, contact Maule Air, Inc., 2099 GA Hwy 133 
South, Moultrie, Georgia 31768; telephone: (229) 985-2045; fax: 
(229) 890-2402; Internet: http://www.mauleairinc.com/pdf/servicebulletins/service_bulletin_11_old.pdf.
    (5) You may view this service information at Small Airplane 
Directorate, 901 Locust, Kansas City, Missouri 64106. For 
information on the availability of this material at the FAA, call 
(816) 329-4148.
    (6) You may view this service information that is incorporated 
by reference at the National Archives and Records Administration 
(NARA). For information on the availability of this material at 
NARA, call 202-741-6030, or go to: http://www.archives.gov/federal-register/cfr/ibr-locations.html.

Appendix to AD 98-15-18 R1

Procedures and Requirements for Ultrasonic Inspection of Maule Wing 
Lift Struts

Equipment Requirements

    1. A portable ultrasonic thickness gauge or flaw detector with 
echo-to-echo digital thickness readout capable of reading to 0.001-
inch and an A-trace waveform display will be needed to do this 
inspection.
    2. An ultrasonic probe with the following specifications will be 
needed to do this inspection: 10 MHz (or higher), 0.283-inch (or 
smaller) diameter dual element or delay line transducer designed for 
thickness gauging. The transducer and ultrasonic system shall be 
capable of accurately measuring the thickness of AISI 4340 steel 
down to 0.020-inch. An accuracy of  0.002-inch 
throughout a 0.020-inch to 0.050-inch thickness range while 
calibrating shall be the criteria for acceptance.
    3. Either a precision machined step wedge made of 4340 steel (or 
similar steel with equivalent sound velocity) or at least three shim 
samples of same material will be needed to do this inspection. One 
thickness of the step wedge or shim shall be less than or equal to 
0.020-inch, one shall be greater than or equal to 0.050-inch and at 
least one other step or shim shall be between these two values.
    4. Glycerin, light oil, or similar non-water based ultrasonic 
couplants are recommended in the setup and inspection procedures. 
Water-based couplants, containing appropriate corrosion inhibitors, 
may be utilized, provided they are removed from both the reference 
standards and the test item after the inspection procedure is 
completed and adequate corrosion prevention steps are then taken to 
protect these items.
     NOTE: Couplant is defined as ``a substance used between 
the face of the transducer and test surface to improve transmission 
of ultrasonic energy across the transducer/strut interface.''
     NOTE: If surface roughness due to paint loss or 
corrosion is present, the surface should be sanded or polished 
smooth before testing to assure a consistent and smooth surface for 
making contact with the transducer. Care shall be taken to remove a 
minimal amount of structural material. Paint repairs may be 
necessary after the inspection

[[Page 76039]]

to prevent further corrosion damage from occurring. Removal of 
surface irregularities will enhance the accuracy of the inspection 
technique.

Instrument Setup

    1. Set up the ultrasonic equipment for thickness measurements as 
specified in the instrument's user's manual. Because of the variety 
of equipment available to perform ultrasonic thickness measurements, 
some modification to this general setup procedure may be necessary. 
However, the tolerance requirement of step 13 and the record keeping 
requirement of step 14, must be satisfied.
    2. If battery power will be employed, check to see that the 
battery has been properly charged. The testing will take 
approximately two hours. Screen brightness and contrast should be 
set to match environmental conditions.
    3. Verify that the instrument is set for the type of transducer 
being used, i.e. single or dual element, and that the frequency 
setting is compatible with the transducer.
    4. If a removable delay line is used, remove it and place a drop 
of couplant between the transducer face and the delay line to assure 
good transmission of ultrasonic energy. Reassemble the delay line 
transducer and continue.
    5. Program a velocity of 0.231-inch/microsecond into the 
ultrasonic unit unless an alternative instrument calibration 
procedure is used to set the sound velocity.
    6. Obtain a step wedge or steel shims per item 3 of the 
Equipment Requirements. Place the probe on the thickest sample using 
couplant. Rotate the transducer slightly back and forth to ``ring'' 
the transducer to the sample. Adjust the delay and range settings to 
arrive at an A-trace signal display with the first backwall echo 
from the steel near the left side of the screen and the second 
backwall echo near the right of the screen. Note that when a single 
element transducer is used, the initial pulse and the delay line/
steel interface will be off of the screen to the left. Adjust the 
gain to place the amplitude of the first backwall signal at 
approximately 80% screen height on the A-trace.
    7. ``Ring'' the transducer on the thinnest step or shim using 
couplant. Select positive half-wave rectified, negative half-wave 
rectified, or filtered signal display to obtain the cleanest signal. 
Adjust the pulse voltage, pulse width, and damping to obtain the 
best signal resolution. These settings can vary from one transducer 
to another and are also user dependent.
    8. Enable the thickness gate, and adjust the gate so that it 
starts at the first backwall echo and ends at the second backwall 
echo. (Measuring between the first and second backwall echoes will 
produce a measurement of the steel thickness that is not affected by 
the paint layer on the strut). If instability of the gate trigger 
occurs, adjust the gain, gate level, and/or damping to stabilize the 
thickness reading.
    9. Check the digital display reading and if it does not agree 
with the known thickness of the thinnest thickness, follow your 
instrument's calibration recommendations to produce the correct 
thickness reading. When a single element transducer is used this 
will usually involve adjusting the fine delay setting.
    10. Place the transducer on the thickest step of shim using 
couplant. Adjust the thickness gate width so that the gate is 
triggered by the second backwall reflection of the thick section. If 
the digital display does not agree with the thickest thickness, 
follow your instruments calibration recommendations to produce the 
correct thickness reading. A slight adjustment in the velocity may 
be necessary to get both the thinnest and the thickest reading 
correct. Document the changed velocity value.
    11. Place couplant on an area of the lift strut which is thought 
to be free of corrosion and ``ring'' the transducer to surface. 
Minor adjustments to the signal and gate settings may be required to 
account for coupling improvements resulting from the paint layer. 
The thickness gate level should be set just high enough so as not to 
be triggered by irrelevant signal noise. An area on the upper 
surface of the lift strut above the inspection area would be a good 
location to complete this step and should produce a thickness 
reading between 0.034-inch and 0.041-inch.
    12. Repeat steps 8, 9, 10, and 11 until both thick and thin shim 
measurements are within tolerance and the lift strut measurement is 
reasonable and steady.
    13. Verify that the thickness value shown in the digital display 
is within  0.002-inch of the correct value for each of 
the three or more steps of the setup wedge or shims. Make no further 
adjustments to the instrument settings.
    14. Record the ultrasonic versus actual thickness of all wedge 
steps or steel shims available as a record of setup.

Inspection Procedure

    1. Clean the lower 18 inches of the wing lift struts using a 
cleaner that will remove all dirt and grease. Dirt and grease will 
adversely affect the accuracy of the inspection technique. Light 
sanding or polishing may also be required to reduce surface 
roughness as noted in the Equipment Requirements section.
    2. Using a flexible ruler, draw a \1/4\-inch grid on the surface 
of the first 11 inches from the lower end of the strut as shown in 
Maule Air, Inc. Service Bulletin No. 11, dated October 30, 1995, as 
applicable. This can be done using a soft (2) pencil and 
should be done on both faces of the strut. As an alternative to 
drawing a complete grid, make two rows of marks spaced every \1/4\ 
inch across the width of the strut. One row of marks should be about 
11 inches from the lower end of the strut, and the second row should 
be several inches away where the strut starts to narrow. Lay the 
flexible ruler between respective tick marks of the two rows and use 
tape or a rubber band to keep the ruler in place. See Figure 1.
    3. Apply a generous amount of couplant inside each of the square 
areas or along the edge of the ruler. Re-application of couplant may 
be necessary.
    4. Place the transducer inside the first square area of the 
drawn grid or at the first \1/4\-inch mark on the ruler and ``ring'' 
the transducer to the strut. When using a dual element transducer, 
be very careful to record the thickness value with the axis of the 
transducer elements perpendicular to any curvature in the strut. If 
this is not done, loss of signal or inaccurate readings can result.
    5. Take readings inside each square on the grid or at \1/4\-inch 
increments along the ruler and record the results. When taking a 
thickness reading, rotate the transducer slightly back and forth and 
experiment with the angle of contact to produce the lowest thickness 
reading possible. Pay close attention to the A-scan display to 
assure that the thickness gate is triggering off of maximized 
backwall echoes.
     NOTE: A reading shall not exceed .041 inch. If a 
reading exceeds .041 inch, repeat steps 13 and 14 of the Instrument 
Setup section before proceeding further.
    6. If the A-trace is unsteady or the thickness reading is 
clearly wrong, adjust the signal gain and/or gate setting to obtain 
reasonable and steady readings. If any instrument setting is 
adjusted, repeat steps 13 and 14 of the Instrument Setup section 
before proceeding further.
    7. In areas where obstructions are present, take a data point as 
close to the correct area as possible.
     NOTE: The strut wall contains a fabrication bead at 
approximately 40% of the strut chord. The bead may interfere with 
accurate measurements in that specific location.
    8. A measurement of 0.024 inch or less shall require replacement 
of the strut prior to further flight.
    9. If at any time during testing an area is encountered where a 
valid thickness measurement cannot be obtained due to a loss of 
signal strength or quality, the area shall be considered suspect. 
These areas may have a remaining wall thickness of less than 0.020-
inch, which is below the range of this setup, or they may have small 
areas of localized corrosion or pitting present. The latter case 
will result in a reduction in signal strength due to the sound being 
scattered from the rough surface and may result in a signal that 
includes echoes from the pits as well as the backwall. The suspect 
area(s) shall be tested with a Maule ``Fabric Tester'' as specified 
in Maule Air, Inc. Service Bulletin No. 11, dated October 30, 1995.
    10. Record the lift strut inspection in the aircraft log book.

[[Page 76040]]

[GRAPHIC] [TIFF OMITTED] TR16DE13.000

    Issued in Kansas City, Missouri, on November 22, 2013.
Earl Lawrence,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. 2013-29682 Filed 12-13-13; 8:45 am]
BILLING CODE 4910-13-P