[Federal Register Volume 64, Number 132 (Monday, July 12, 1999)]
[Proposed Rules]
[Pages 37465-37470]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-17553]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-CE-13-AD]
RIN 2120-AA64


Airworthiness Directives; The New Piper Aircraft, Inc. J-2 Series 
Airplanes That are Equipped With Wing Lift Struts

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes to adopt a new airworthiness directive 
(AD) that would apply to certain The New Piper Aircraft, Inc. (Piper) 
J-2 series airplanes equipped with wing lift struts. The proposed AD 
would require repetitively inspecting the wing lift struts for dents 
and corrosion and the wing lift strut forks for cracks; replacing any 
strut found with corrosion or dents, or forks with cracks; and 
repetitively replacing the wing lift strut forks. The proposed AD would 
also require incorporating a ``NO STEP'' placard on the lift strut. The 
proposed AD is the result of the Federal Aviation Administration (FAA) 
inadvertently omitting the J-2 series airplanes from the applicability 
of AD 99-01-05. The actions specified by the proposed AD are intended 
to prevent in-flight separation of the wing from the airplane caused by 
wing lift struts with dents or corrosion or wing lift forks with 
cracks, which could result in loss of control of the airplane.

DATES: Comments must be received on or before September 8, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Central Region, Office of the Regional Counsel, 
Attention: Rules Docket No. 99-CE-13-AD, Room 1558, 601 E. 12th Street, 
Kansas City, Missouri 64106. Comments may be inspected at this location 
between 8 a.m. and 4 p.m., Monday through Friday, holidays excepted.
    Service information that applies to the proposed 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 F. Atlee 
Dodge supplemental type certificate (STC) may be obtained from F. Atlee 
Dodge, Aircraft Services, Inc., P.O. Box 190409, Anchorage, Alaska 
99519-0409. Copies of the instructions to the Jensen Aircraft STC's may 
be obtained from Jensen

[[Page 37466]]

Aircraft, Inc., 9225 County Road 140, Salida, Colorado 81201. This 
information also may be examined at the Rules Docket at the address 
above.

FOR FURTHER INFORMATION CONTACT: Mr. William O. Herderich, Aerospace 
Engineer, FAA, Atlanta Aircraft Certification Office, One Crown Center, 
1895 Phoenix Boulevard, suite 450, Atlanta, Georgia 30349; telephone: 
(770) 703-6084; facsimile: (770) 703-6097.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications should identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report that summarizes each FAA-public contact concerned 
with the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket No. 99-CE-13-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Central Region, Office of the Regional Counsel, Attention: 
Rules Docket No. 99-CE-13-AD, Room 1558, 601 E. 12th Street, Kansas 
City, Missouri 64106.

Discussion

    AD 99-01-05, Amendment 39-10972 (63 FR 72132, December 31, 1998), 
currently requires the following on certain Piper airplanes that are 
equipped with wing lift struts:

--Repetitively inspecting the wing lift struts for dents and corrosion 
and the wing lift strut forks for cracks; replacing any strut found 
with corrosion or dents, or forks with cracks; and repetitively 
replacing the wing lift strut forks;
--Incorporating a ``NO STEP'' placard on the lift strut; and
--Providing the option of installing certain wing lift strut and wing 
lift strut fork assemblies, as terminating action for repetitive 
inspection and replacement requirements.

    AD 99-01-05 superseded AD 93-10-06, Amendment 39-8586 (58 FR 29965, 
May 25, 1993). The following describes the differences between AD 93-
10-06 and AD 99-01-05:

--AD 99-01-05 clarifies certain requirements of AD 93-10-06;
--The requirement of AD 93-10-06 of repetitively inspecting the lift 
strut forks on the Piper PA-25 series airplanes was deemed unnecessary 
by AD 99-01-05;
--AD 99-01-05 incorporates airplane models inadvertently omitted from 
AD 93-10-06;
--AD 99-01-05 requires fabricating and installing a placard on the lift 
strut; and
--The J-2 series airplanes were included in the Applicability of AD 93-
10-06, but omitted from the Applicability of AD 99-01-05.

The FAA's Determination

    After examining the circumstances and reviewing all available 
information related to the incidents described above, the FAA has 
determined that:

--The J-2 series airplanes were inadvertently omitted from AD 99-01-05;
--The actions of AD 99-01-05 should apply to the J-2 series airplanes; 
and
--AD action should be taken to prevent in-flight separation of the wing 
from the airplane caused by wing lift struts with dents or corrosion or 
wing lift forks with cracks, which could result in loss of control of 
the airplane.

Explanation of the Provisions of the Proposed AD

    Since an unsafe condition has been identified that is likely to 
exist or develop in other Piper J-2 series airplanes of the same type 
design that are equipped with wing lift struts, the FAA is proposing AD 
action. The proposed AD would require repetitively inspecting the wing 
lift struts for dents and corrosion and the wing lift strut forks for 
cracks; replacing any strut found with corrosion or dents, or forks 
with cracks; and repetitively replacing the wing lift strut forks. The 
proposed AD would also require installing a placard on the lift strut, 
and would provide the option of installing certain wing lift strut and 
wing lift strut fork assemblies, as terminating action for repetitive 
inspection and replacement requirements.

Cost Impact

    The FAA estimates that 91 airplanes in the U.S. registry would be 
affected by the proposed AD.
    It would take approximately 8 workhours per airplane to accomplish 
the proposed initial inspection, and the average labor rate is 
approximately $60 an hour. Based on these figures, the total cost 
impact of the proposed initial inspection on U.S. operators is 
estimated to be $43,680, or $480 per airplane. These figures are based 
only on the cost of the proposed initial inspection and do not take 
into account the costs of any repetitive inspections. The FAA has no 
way of determining how many repetitive inspections each owner/operator 
would incur over the life of the airplane.
    It would take approximately 4 workhours per airplane to accomplish 
the proposed initial wing lift strut fork replacements, and the average 
labor rate is approximately $60 an hour. Fork assemblies cost 
approximately $110 each and four are required for each airplane. Based 
on these figures, the total cost impact of the proposed initial wing 
lift strut fork replacements on U.S. operators is estimated to be 
$61,880, or $680 per airplane.
    Airplane operators who do not incorporate the improved design wing 
lift strut assemblies would have to repetitively replace the wing lift 
strut forks. The FAA has no way of determining how many airplanes do 
not have the improved design wing lift strut assemblies installed and 
would need repetitive strut fork replacements.

Regulatory Impact

    The regulations proposed herein would 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 
proposal would 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) if

[[Page 37467]]

promulgated, 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 draft regulatory 
evaluation prepared for this action has been placed 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, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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 adding a new airworthiness directive 
(AD) to read as follows:

The New Piper Aircraft, Inc.: Docket No. 99-CE-13-AD.

    Applicability: J-2 series airplanes, serial numbers 500 through 
1975, certificated in any category; that are equipped with wing lift 
struts.

    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 wing lift struts with dents or corrosion or wing lift 
forks with cracks, 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) Within 1 calendar month after the effective date of this AD 
or within 24 calendar months after the last inspection accomplished 
per AD 93-10-06, whichever occurs later, remove the wing lift struts 
in accordance with Piper Service Bulletin (SB) No. 528D, and 
accomplish one of the following (the actions in either paragraph 
(a)(1), (a)(2), (a)(3), or (a)(4), including subparagraphs, of this 
AD):
    (1) Inspect the wing lift struts for perceptible dents (as 
defined in the service bulletin referenced below) and corrosion in 
accordance with the ``INSTRUCTIONS'' section in Part I of Piper SB 
No. 528D, dated October 19, 1990.
    (i) If no perceptible dents 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 the SB 
referenced above. Reinspect the lift struts at intervals not to 
exceed 24 calendar months.
    (ii) If a perceptible dent 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) or (a)(4) 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 
the SB referenced above. Reinspect the lift struts at intervals not 
to exceed 24 calendar months.
    (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) 
or (a)(4) 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 (or FAA-approved equivalent part 
numbers), on each wing as specified in the INSTRUCTIONS section in 
Part II of the above-referenced SB. These sealed wing lift strut 
assemblies also include the wing lift strut forks. Installation of 
these assemblies constitutes terminating action for the inspection 
and replacement requirements of both paragraphs (a) and (b) of this 
AD.
    (b) 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, whichever is later, remove the wing lift strut forks and 
accomplish one of the following (the actions in either paragraph 
(b)(1), (b)(2) or (b)(3); including subparagraphs, of this AD):
    (1) Inspect the wing lift strut forks for cracks 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 after the 
effective date of this AD, 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 after the effective 
date of this AD, 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 (or FAA-approved equivalent part 
numbers), on each wing as specified in the INSTRUCTIONS section in 
Part II of the above-referenced SB.
    (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.
    (c) If holes are drilled in wing lift strut assemblies installed 
in accordance with (a)(4) or (b)(3) 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) or (a)(2), including all subparagraphs, of this 
AD.
    (d) Within 1 calendar month after the effective date of this AD 
and thereafter prior

[[Page 37468]]

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 
utilizing 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 and repetitive compliance times that provides an equivalent 
level of safety may be approved by the Manager, FAA, Atlanta 
Aircraft Certification Office (ACO), One Crown Center, 1895 Phoenix 
Boulevard, suite 450, Atlanta, Georgia 30349. The request shall be 
forwarded through an appropriate FAA Maintenance Inspector, who may 
add comments and then send it to the Manager, Atlanta ACO.

    Note 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Atlanta ACO.

    (g) 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, 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. These documents may be examined at the FAA, Central Region, 
Office of the Regional Counsel, Room 1558, 601 E. 12th Street, 
Kansas City, Missouri.

Appendix to Docket No. 99-CE-13-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.

[[Page 37469]]

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 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

[[Page 37470]]

[GRAPHIC] [TIFF OMITTED] TP12JY99.032



    Issued in Kansas City, Missouri, on July 2, 1999.
Marvin R. Nuss,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-17553 Filed 7-9-99; 8:45 am]
BILLING CODE 4910-13-C