[Federal Register Volume 63, Number 251 (Thursday, December 31, 1998)]
[Rules and Regulations]
[Pages 72132-72137]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-34384]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 96-CE-72-AD; Amendment 39-10972; AD 99-01-05]
RIN 2120-AA64
Airworthiness Directives; All Airplane Models of The New Piper
Aircraft, Inc. (formerly Piper Aircraft Corporation) That Are Equipped
with Wing Lift Struts
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
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SUMMARY: This amendment supersedes Airworthiness Directive (AD) 93-10-
06, which currently requires repetitively inspecting the wing lift
struts and wing lift strut forks for cracks or corrosion on all
airplane models of The New Piper Aircraft, Inc. (Piper) that are
equipped with wing lift struts, and replacing any strut or fork found
cracked or corroded. This AD clarifies certain requirements of AD 93-
10-06, eliminates the lift strut fork repetitive inspection requirement
on the Piper PA-25 series airplanes, incorporates models inadvertently
omitted from AD 93-10-06, and requires fabricating and installing a
placard on the lift strut. This AD results from reports, questions, and
information received from the field on AD 93-10-06, which show a need
to clarify and add information that will more fully achieve the safety
intent of that AD. The actions specified by this AD are intended to
prevent in-flight separation of the wing from the airplane caused by
corroded wing lift struts or cracked wing lift forks, which could
result in loss of control of the airplane.
DATES: Effective February 8, 1999.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of February 8, 1999.
ADDRESSES: The service bulletins referenced in this AD may be obtained
from The New Piper Aircraft, Inc., Customer Services, 2926 Piper Drive,
Vero Beach, Florida 32960. Copies of the instructions to the Jensen
Aircraft STC's may be obtained from Jensen Aircraft, Inc., 9225 County
Road 140, Salida, Colorado 81201. Copies of the instructions to the F.
Atlee Dodge STC may be obtained from F. Atlee Dodge, Aircraft Services,
Inc., P.O. Box 190409, Anchorage, Alaska 99519-0409. This information
may also be examined at the Federal Aviation Administration
[[Page 72133]]
(FAA), Central Region, Office of the Regional Counsel, Attention: Rules
Docket No. 96-CE-72-AD, Room 1558, 601 E. 12th Street, Kansas City,
Missouri 64106; or at the Office of the Federal Register, 800 North
Capitol Street, NW, suite 700, Washington, DC.
FOR FURTHER INFORMATION CONTACT: William O. Herderich, Aerospace
Engineer, FAA, Atlanta Certification Office, One Crown Center, 1895
Phoenix Boulevard, suite 450, Atlanta, Georgia 30349; telephone: (770)
703-6084; facsimile: (770) 703-6097.
SUPPLEMENTARY INFORMATION:
Events Leading to the Issuance of This AD
A proposal to amend part 39 of the Federal Aviation Regulations (14
CFR part 39) to include an AD that would apply to all Piper airplane
models equipped with wing lift struts was published in the Federal
Register as a notice of proposed rulemaking (NPRM) on April 23, 1998,
(63 FR 20143). The NPRM proposed to supersede AD 93-10-06, Amendment
39-8586 (58 FR 29965, May 25, 1993), which currently requires
repetitively inspecting the wing lift struts and wing lift strut forks
for cracks or corrosion, and replacing any strut or fork found cracked
or corroded. The NPRM proposed to retain the requirements of
repetitively inspecting the wing lift struts and wing lift strut forks
for cracks or corrosion, and replacing any strut or fork found cracked
or corroded. The proposed NPRM would also clarify certain requirements
of AD 93-10-06, eliminate the lift strut fork repetitive inspection
requirement on the Piper PA-25 series airplanes, incorporate airplane
models inadvertently omitted from the applicability of AD 93-10-06, and
require installing a placard on the lift strut. Accomplishment of the
inspections specified in the NPRM would be required in accordance with
Piper Service Bulletin (SB) No. 528D, dated October 19, 1990, or Piper
SB No. 910A, dated October 10, 1989; or the Appendix to the proposed
AD.
Accomplishment of the installation as specified in the NPRM would
be required in accordance with one of the following:
--The maintenance manual for original equipment manufacturer (OEM) wing
lift struts or new sealed wing lift strut assemblies as referenced in
Piper SB 528D, dated October 19, 1990, or Piper SB No. 910A, dated
October 10, 1989;
--F. Atlee Dodge Instructions No. 3233-I for Modified Piper Wing Lift
Struts (STC SA4635NM), dated February 1, 1991; or
--Jensen Aircraft Installation Instructions for Modified Lift Strut
Fittings, which incorporates the following pages:
------------------------------------------------------------------------
Pages Revision level Date
------------------------------------------------------------------------
1 and 5..................... Original Issue...... July 15, 1983.
2, 4, and 6................. Revision No. 1...... March 30, 1984.
a and 3..................... Revision No. 2...... April 20, 1984.
------------------------------------------------------------------------
The NPRM was the result of reports, questions, and information
received from the field on AD 93-10-06, which show a need to clarify
and add information that will more fully achieve the safety intent of
that AD.
Interested persons have been afforded an opportunity to participate
in the making of this amendment. Due consideration has been given to
the two comments received.
Comment Disposition
Both commenters request that the FAA reference Univair Aircraft
Corporation lift strut assemblies in the AD. Univair holds a parts
manufacturer approval (PMA) for parts that are identical to the
improved design Piper lift strut assemblies referenced in the NPRM.
The FAA does not concur. FAA policy is to not reference PMA parts
in AD's, unless the FAA determines that the unsafe condition applies to
the PMA parts. If these Univair parts are installed, then the actions
of this AD would not apply because the parts are an FAA-approved
equivalent to the improved design Piper lift strut assemblies that,
when installed, eliminate the repetitive inspection requirement of the
AD.
No changes have been made to the AD based on these comments.
The FAA's Determination
After careful review of all available information related to the
subject presented above, the FAA has determined that air safety and the
public interest require the adoption of the rule as proposed except for
minor editorial corrections. The FAA has determined that these minor
corrections will not change the meaning of the AD and will not add any
additional burden upon the public than was already proposed.
Cost Impact
The FAA estimates that 22,000 airplanes in the U.S. registry will
be affected by this AD, that it will take approximately 8 workhours per
airplane to accomplish the initial inspection, and that the average
labor rate is approximately $60 an hour. Based on these figures, the
total cost impact of this AD on U.S. operators is estimated to be
$10,560,000, or $480 per airplane.
These figures are based only on the cost of the initial inspection
and do not account for the costs of any repetitive inspections. The FAA
has no way of determining how many repetitive inspections each owner/
operator will incur over the life of the airplane. The FAA also has no
way of determining how many airplanes have improved design wing lift
struts and forks installed. This will eliminate the requirements of
this AD, and thus reduce the cost impact of this AD upon the public.
AD 93-10-06 currently requires the same actions as proposed in this
document. The only differences between AD 93-10-06 and this AD are the
addition of ultrasonic methods as an option for accomplishing the
inspections, the elimination of the requirement of inspecting the lift
strut forks on Piper PA-25 series airplanes, the addition of certain
airplane models equipped with Piper lift strut assemblies, the addition
of the requirement of installing the ``NO STEP'' placard on the wing
lift struts, and editorial corrections and additions for clarification
purposes.
Regulatory Impact
The regulations adopted herein will not have substantial direct
effects on the States, on the relationship between the national
government and the States, or on the distribution of power and
responsibilities among the various levels of government. Therefore, in
accordance with Executive Order 12612, it is determined that this final
rule does not have sufficient federalism implications to warrant the
preparation of a Federalism Assessment.
For the reasons discussed above, I certify that this action (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); 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. A copy of the final evaluation prepared for this
action is contained in the Rules Docket. A copy of it may be obtained
by contacting the Rules Docket at the location provided under the
caption ADDRESSES.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.
[[Page 72134]]
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration amends part 39 of
the Federal Aviation Regulations (14 CFR part 39) as follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by removing Airworthiness Directive
(AD) 93-10-06, Amendment 39-8536 (58 FR 29965, May 25, 1993), and by
adding a new AD to read as follows:
99-01-05 The New Piper Aircraft, Inc.: Amendment 39-10972; Docket
No. 96-CE-72-AD; Supersedes AD 93-10-06, Amendment 39-8536.
Applicability: The following model and serial number airplanes,
certificated in any category:
------------------------------------------------------------------------
Models Serial numbers
------------------------------------------------------------------------
TG-8 (Army TG-8, Navy XLNP-1)................ All serial numbers.
E-2 and F-2.................................. All serial numbers.
J3C-40, J3C-50, J3C-50S, (Army L-4, L-4B, L- All serial numbers.
4H, and L-4J), J3C-65 (Navy NE-1 and NE-2),
J3C-65S J3F-50, J3F-50S, J3F-60, J3F-60S,
J3F-65 (Army L-4D), J3F-65S, J3L, J3L-S, J3L-
65 (Army L-4C), and J3L-65S.
J4, J4A, J4A-S, and J4E (Army L-4E).......... 4-401 through 4-1649.
J5A (Army L-4F), J5A-80, J5B (Army L-4G), All serial numbers.
J5C, L-14, AE-1, and HE-1.
PA-11 and PA-11S............................. 11-1 through 11-1678.
PA-12 and PA-12S............................. 12-1 through 12-4036.
PA-14........................................ 14-1 through 14-523.
PA-15........................................ 15-1 through 15-388.
PA-16 and PA-16S............................. 16-1 through 16-736.
PA-17........................................ 17-1 through 17-215.
PA-18, PA-18S, PA-18 ``105'' (Special), PA- 18-1 through 18-8309025,
18S ``105'' (Special), PA-18A, PA-18 ``125'' 189001 through 1809032,
(Army L-21A), PA-18S ``125'', PA-18AS and 1809034 through
``125'', PA-18 ``135'' (Army L-21B), PA-18A 1809040.
``135'', PA-18S ``135'', PA-18AS ``135'', PA-
18 ``150'', PA-18A ``150'', PA-18S ``150'',
PA-18AS ``150'', PA-18A (Restricted), PA-18A
``135'' (Restricted), and PA-18A ``150''
(Restricted).
PA-19 (Army L-18C), and PA-19S............... 19-1, 19-2, and 19-3.
PA-20, PA-20S, PA-20 ``115'', PA-20S ``115'', 20-1 through 20-1121.
PA-20 ``135'', and PA-20S ``135''.
PA-22, PA-22-108, PA-22-135, PA-22S-135, PA- 22-1 through 22-9848.
22-150, PA-22S-150, PA-22-160, and PA-22S-
160.
PA-25, PA-25-235, and PA-25-260.............. 25-1 through 25-8156024.
------------------------------------------------------------------------
Note 1: This AD applies to each airplane identified in the
preceding applicability provision, regardless of whether it has been
modified, altered, or repaired in the area subject to the
requirements of this AD. For airplanes that have been modified,
altered, or repaired so that the performance of the requirements of
this AD is affected, the owner/operator must request approval for an
alternative method of compliance in accordance with paragraph (f) of
this AD. The request should include an assessment of the effect of
the modification, alteration, or repair on the unsafe condition
addressed by this AD; and, if the unsafe condition has not been
eliminated, the request should include specific proposed actions to
address it.
Compliance: Required as indicated in the body of this AD, unless
already accomplished.
To prevent in-flight separation of the wing from the airplane
caused by corroded wing lift struts or cracked wing lift strut
forks, which could result in loss of control of the airplane,
accomplish the following:
Note 2: The paragraph structure of this AD is as follows:
Level 1: (a), (b), (c), etc.
Level 2: (1), (2), (3), etc.
Level 3: (i), (ii), (iii), etc.
Level 4: (A), (B), (C), etc.
Level 2, Level 3, and Level 4 structures are designations of the
Level 1 paragraph they immediately follow.
(a) For all affected airplane models, within 1 calendar month
after the effective date of this AD or within 24 calendar months
after the last inspection accomplished in accordance with AD 93-10-
06 (superseded by this action), whichever occurs later, remove the
wing lift struts in accordance with Piper Service Bulletin (SB) No.
528D, dated October 19, 1990, or Piper SB No. 910A, dated October
10, 1989, as applicable, and accomplish one of the following (the
actions in either paragraph (a)(1), (a)(2), (a)(3), (a)(4), or
(a)(5); including subparagraphs, of this AD):
(1) Inspect the wing lift struts for corrosion in accordance
with the ``Instructions'' section in Part I of either Piper SB No.
528D, dated October 19, 1990, or Piper SB No. 910A, dated October
10, 1989, as applicable.
(i) If no perceptible dents (as defined in the above SB's) are
found in the wing lift strut and no corrosion is externally visible,
prior to further flight, apply corrosion inhibitor to each strut in
accordance with whichever of the above SB's that is applicable.
Reinspect the lift struts at intervals not to exceed 24 calendar
months and accomplish any of the requirements of paragraph (a) of
this AD, including all subparagraphs.
(ii) If a perceptible dent (as defined in the above SB's) is
found in the wing lift strut or external corrosion is found, prior
to further flight, accomplish one of the installations (and
subsequent actions presented in each paragraph) specified in
paragraphs (a)(3), (a)(4), or (a)(5) of this AD.
(2) Inspect the wing lift struts for corrosion in accordance
with the Appendix to this AD. The inspection procedures in this
Appendix must be accomplished by a Level 2 inspector certified using
the guidelines established by the American Society for Non-
destructive Testing, or MIL-STD-410.
(i) If no corrosion is found that is externally visible and all
requirements in the Appendix to this AD are met, prior to further
flight, apply corrosion inhibitor to each strut in accordance with
whichever of the above SB's that is applicable. Reinspect the lift
struts at intervals not to exceed 24 calendar months and accomplish
any of the requirements of paragraph (a) of this AD, including all
subparagraphs.
(ii) If external corrosion is found or if any of the
requirements in the Appendix of this AD are not met, prior to
further flight, accomplish one of the installations (and subsequent
actions presented in each paragraph) specified in paragraphs (a)(3),
(a)(4), or (a)(5) of this AD.
(3) Install original equipment manufacturer (OEM) part number
wing struts (or FAA-approved equivalent part numbers) that have been
inspected in accordance with the specifications presented in either
paragraph (a)(1) or (a)(2) of this AD, and are found to be airworthy
according to the inspection requirements included in these
paragraphs. Thereafter, inspect these wing lift struts at intervals
not to exceed 24 calendar months in accordance with the
specifications presented in either paragraph (a)(1) or (a)(2) of
this AD.
(4) Install new sealed wing lift strut assemblies, part numbers
as specified in Piper SB No. 528D and Piper SB No. 910A (or FAA-
approved equivalent part numbers) on each wing as specified in the
Instructions section in Part II of the above-referenced
[[Page 72135]]
SB's. These sealed wing lift strut assemblies also include the wing
lift strut forks. Installation of these assemblies constitute
terminating action for the inspection requirements of both
paragraphs (a) and (b) of this AD.
(5) Install F. Atlee Dodge wing lift strut assemblies in
accordance with F. Atlee Dodge Installation Instructions No. 3233-I
for Modified Piper Wing Lift Struts (Supplemental Type Certificate
(STC) SA4635NM), dated February 1, 1991. Thereafter, inspect these
wing lift struts at intervals not to exceed 60 calendar months in
accordance with the specifications presented in paragraph (a)(1) or
(a)(2) of this AD.
(b) For all affected airplane models, except for Models PA-25,
PA-25-235, and PA-25-260, within the next 100 hours time-in-service
(TIS) after the effective date of this AD or within 500 hours TIS
after the last inspection accomplished in accordance with AD 93-10-
06 (superseded by this action), whichever occurs later, remove the
wing lift strut forks, and accomplish one of the following (the
actions in either paragraph (b)(1), (b)(2), (b)(3), (b)(4), or
(b)(5); including subparagraphs, of this AD):
(1) Inspect the wing lift strut forks using FAA-approved
magnetic particle procedures.
(i) If no cracks are found, reinspect at intervals not to exceed
500 hours TIS provided that the replacement requirements of
paragraphs (b)(1)(ii)(B) and (b)(1)(ii)(C) of this AD have been met.
(ii) Replace the wing lift strut forks at whichever of the
following is applicable:
(A) If cracks are found on any wing lift strut fork: Prior to
further flight;
(B) If the airplane is equipped with floats or has been equipped
with floats within the last 2,000 hours TIS and no cracks are found
during the above inspections: Upon accumulating 1,000 hours TIS on
the wing lift strut forks or within the next 100 hours TIS,
whichever occurs later; or
(C) If the airplane has not been equipped with floats within the
last 2,000 hours TIS and no cracks are found during the above
inspections: Upon accumulating 2,000 hours TIS on the wing lift
strut forks or within the next 100 hours TIS, whichever occurs
later.
(iii) Replacement parts shall be of the same part numbers of the
existing part (or FAA-approved equivalent part numbers) and shall be
manufactured with rolled threads. Lift strut forks manufactured with
machined (cut) threads shall not be utilized.
(iv) The 500-hour TIS interval repetitive inspections are still
required when the above replacements are accomplished.
(2) Install new OEM part number wing lift strut forks (or FAA-
approved equivalent part numbers). Reinspect and replace these wing
lift strut forks at the intervals specified in paragraphs (b)(1)(i),
(b)(1)(ii), (b)(1)(iii), and (b)(1)(iv), including all
subparagraphs, of this AD.
(3) Install new sealed wing lift strut assemblies, part numbers
as specified in Piper SB No. 528D and Piper SB No. 910A (or FAA-
approved equivalent part numbers) on each wing, as specified in the
Instructions section in Part II of the above-referenced SB's.
(i) This installation may have ``already been accomplished''
through the actions specified in paragraph (a)(4) of this AD.
(ii) No repetitive inspections are required after installing
these sealed wing lift strut assemblies.
(4) Install Jensen Aircraft wing lift strut fork assemblies as
specified in the STC's presented in the paragraphs that follow, as
applicable, in accordance with Jensen Aircraft Installation
Instructions for Modified Lift Strut Fittings, which incorporates
the following pages:
------------------------------------------------------------------------
Pages Revision level Date
------------------------------------------------------------------------
1 and 5..................... Original Issue...... July 15, 1983.
2, 4, and 6................. Revision No. 1...... March 30, 1984.
a and 3..................... Revision No. 2...... April 20, 1984.
------------------------------------------------------------------------
No repetitive inspections are required after installing these Jensen
Aircraft wing lift strut fork assemblies; however, repetitive
inspections of the lift strut are required as specified in paragraph
(a)(1), (a)(2), or (a)(3) of this AD:
(i) For Models PA-12 and PA-12S airplanes: STC SA1583NM;
(ii) For Model PA-14 airplanes: STC SA1584NM;
(iii) For the Models PA-16 and PA-16S airplanes: STC SA1590NM;
(iv) For the Models PA-18, PA-18S, 189001 PA-18 ``105''
(Special), PA-18S ``105'' (Special), PA-18A, PA-18 ``125'' (Army L-
21A), PA-18S ``125'', PA-18AS ``125'', PA-18 ``135'' (Army L-21B),
PA-18A ``135'', PA-18S ``135'', PA-18S ``135'', PA-18AS ``135'', PA-
18 ``150'', PA-18A ``150'', PA-18S ``150'', PA-18AS ``150'', PA-18A
(Restricted), PA-18A ``135'' (Restricted), and PA-18A ``150''
(Restricted) airplanes: STC SA1585NM;
(v) For the Models PA-20, PA-20S, PA-20 ``115'', PA-20S ``115'',
PA-20 ``135'', and PA-20S ``135'' airplanes: STC SA1586NM; and
(vi) For the Model PA-22 airplanes: STC SA1587NM.
(5) Install F. Atlee Dodge wing lift strut assemblies in
accordance with F. Atlee Dodge Installation Instructions No. 3233-I
for Modified Piper Wing Lift Struts (STC SA4635NM), dated February
1, 1991.
(i) No repetitive inspections of the wing lift strut forks are
required when these assemblies are installed.
(ii) This installation may have ``already been accomplished''
through the actions specified in paragraph (a)(5) of this AD.
(c) If holes are drilled, in either one of the scenarios
presented in paragraphs (c)(1) and (c)(2) of this AD, to attach
cuffs, door clips, or other hardware, inspect the wing lift struts
at intervals not to exceed 24 calendar months using the procedures
specified in paragraphs (a)(1) and (a)(2), including all
subparagraphs, of this AD:
(1) Wing lift strut assemblies installed in accordance with
(a)(4) or (b)(3) of this AD; or
(2) F. Atlee Dodge wing lift strut assemblies installed in
accordance with paragraph (a)(5) or (b)(5) of this AD.
(d) For all affected airplane models, within 1 calendar month
after the effective date of this AD or within 24 calendar months
after the last inspection accomplished in accordance with AD 93-10-
06 (superseded by this action), whichever occurs later, and
thereafter prior to further flight after the installation of any
lift strut assembly, accomplish one of the following:
(1) Install ``NO STEP'' decal, Piper part number (P/N) 80944-02,
on each wing lift strut approximately 6 inches from the bottom of
the struts in a way that the letters can be read when entering and
exiting the aircraft; or
(2) Paint the statement ``NO STEP'' approximately 6 inches from
the bottom of the struts in a way that the letters can be read when
entering and exiting the aircraft. Use a minimum of 1-inch letters
using a color that contrasts with the color of the airplane.
(e) Special flight permits may be issued in accordance with
sections 21.197 and 21.199 of the Federal Aviation Regulations (14
CFR 21.197 and 21.199) to operate the airplane to a location where
the requirements of this AD can be accomplished.
(f) An alternative method of compliance or adjustment of the
initial or repetitive compliance times that provides an equivalent
level of safety may be approved by the Manager, Atlanta Aircraft
Certification Office (ACO), One Crown Center, 1895 Phoenix
Boulevard, suite 450, Atlanta, Georgia 30349.
(1) The request shall be forwarded through an appropriate FAA
Maintenance Inspector, who may add comments and then send it to the
Manager, Atlanta ACO.
(2) Alternative methods of compliance approved in accordance
with AD 93-10-06, Amendment 39-8536, are considered approved as
alternative methods of compliance for this AD.
Note 3: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Atlanta Aircraft Certification Office.
(g) The inspections required by this AD shall be done in
accordance with Piper Service Bulletin No. 528D, dated October 19,
1990, and Piper Service Bulletin No. 910A, dated October 10, 1989.
The installation required by this AD shall be done in accordance
with F. Atlee Dodge Installation Instructions No. 3233-I for
Modified Piper Wing Lift Struts (Supplemental Type Certificate (STC)
SA4635NM), dated February 1, 1991, and Jensen Aircraft Installation
Instructions for Modified Lift Strut Fittings, which incorporates
the following pages:
------------------------------------------------------------------------
Pages Revision level Date
------------------------------------------------------------------------
1 and 5..................... Original Issue...... July 15, 1983.
2, 4, and 6................. Revision No. 1...... March 30, 1984.
a and 3..................... Revision No. 2...... April 20, 1984.
------------------------------------------------------------------------
This incorporation by reference was approved by the Director of the
Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part
51. The service bulletins referenced in this AD may be obtained from
The New Piper Aircraft, Inc., Customer Services, 2926 Piper Drive,
Vero Beach, Florida 32960. Copies of the instructions to
[[Page 72136]]
the Jensen Aircraft STC's may be obtained from Jensen Aircraft, 9225
County Road 140, Salida, Colorado 81201. Copies of the instructions
to the F. Atlee Dodge STC may be obtained from F. Atlee Dodge,
Aircraft Services, Inc., P.O. Box 190409, Anchorage, Alaska 99519-
0409. Copies may be inspected at the FAA, Central Region, Office of
the Regional Counsel, Room 1558, 601 E. 12th Street, Kansas City,
Missouri, or at the Office of the Federal Register, 800 North
Capitol Street, NW, suite 700, Washington, DC.
(h) This amendment supersedes AD 93-10-06, Amendment 39-8536.
(i) This amendment becomes effective on February 8, 1999.
Appendix to AD 99-01-05; Amendment 39-10972; Docket No. 96-CE-72-AD
Procedures and Requirements for Ultrasonic Inspection of Piper 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 accomplish
this inspection.
2. An ultrasonic probe with the following specifications will be
needed to accomplish 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 accomplish 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 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
Piper Service Bulletin No. 528D or 910A, 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
[[Page 72137]]
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 Piper Service Bulletin No. 528D or 910A.
10. Record the lift strut inspection in the aircraft log book.
BILLING CODE 4910-13-P
[GRAPHIC] [TIFF OMITTED] TR31DE98.002
Issued in Kansas City, Missouri, on December 22, 1998.
Michael Gallagher,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. 98-34384 Filed 12-30-98; 8:45 am]
BILLING CODE 4910-13-C
