[Federal Register Volume 63, Number 78 (Thursday, April 23, 1998)]
[Proposed Rules]
[Pages 20143-20148]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-10749]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-CE-72-AD]
RIN 2120-AA64


Airworthiness Directives; All Models of The New Piper Aircraft, 
Inc. (Formerly Piper Aircraft Corporation) Airplanes 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 supersede Airworthiness Directive 
(AD) 93-10-06, which currently applies to all models of The New Piper 
Aircraft, Inc. (Piper) airplanes equipped with wing lift struts. AD 93-
10-06 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 proposed 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. This action 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. The 
actions specified by the proposed 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: Comments must be received on or before July 1, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (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. Comments may be inspected at this location 
between 8 a.m. and 4 p.m., Monday through Friday, holidays excepted.
    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 also 
may be examined at the Rules Docket at the address above.

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:

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. 96-CE-72-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. 96-CE-72-AD, Room 1558, 601 E. 12th Street, Kansas 
City, Missouri 64106.

Discussion

    AD 93-10-06, Amendment 39-8586 (58 FR 29965, May 25, 1993), 
currently requires the following on Piper airplane models equipped with 
wing lift struts: 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. AD 93-10-06 provides the option of 
installing certain lift struts and forks as terminating action for the 
repetitive inspection requirement. Accomplishing the actions required 
by AD 93-10-06 is in accordance with Piper Service Bulletin No. 528D, 
dated October 19, 1990, or Piper Service Bulletin No. 910A, dated 
October 10, 1989, as applicable.
    AD 93-10-06 resulted from reports of corroded wing lift struts and 
cracked wing lift strut forks on several Piper airplanes.

Actions Since Issuance of Previous Rule

    AD 93-10-06 requires inspecting the wing lift struts in accordance 
with Piper Service Bulletin (SB) No. 528D, dated October 19, 1990, and 
Piper SB No. 910A, dated October 10, 1989. These SB's specify these 
inspections using a Maule ``fabric tester.'' After reviewing data 
submitted with requests from operators of the affected airplanes for 
alternative inspection methods, the FAA has determined that an 
alternative non-destructive inspection method for the wing lift struts 
is available through the use of ultrasonic equipment. The FAA worked 
with a research facility to develop ultrasound inspection procedures 
for the wing lift struts.
    The FAA inadvertently mandated the inspections of the lift strut 
forks on Piper PA-25 series airplanes through AD 93-10-06. Lift strut 
fork inspections are not necessary for Piper PA-25 series airplanes. In 
addition, the FAA inadvertently omitted certain models equipped with 
lift struts. These models (referenced in Piper SB 528D) are equipped 
with lift strut assemblies of the same type design and therefore should 
be subjected to the repetitive inspection requirement of AD 93-10-06.
    Piper equipped all of the affected airplanes with a ``No Step'' 
placard on the wing lift struts. The reason for this placard is to 
assure that no person steps on the wing lift struts and puts excessive 
pressure on the struts, which could result in fatigue failure. The 
intent was to include in AD 93-10-06

[[Page 20144]]

the requirement of installing this placard or painting the words ``No 
Step'' on the wing lift struts during any replacement required by that 
AD. The FAA inadvertently left that requirement out, and will include 
that provision in this proposed AD.
    The FAA has also received numerous calls from owners/operators of 
the airplanes affected by AD 93-10-06 in which clarification to the AD 
was requested. The FAA is keeping this information in mind in drafting 
the proposed AD.

The FAA's Determination

    After examining the circumstances and reviewing all available 
information related to the incidents described above, the FAA has 
determined that AD action should be taken to prevent in-flight 
separation of the wing from the airplane caused by corroded wing lift 
struts or cracked wing lift forks.

Explanation of the Provisions of the Proposed AD

    Since an unsafe condition has been identified that is likely to 
exist or develop in Piper airplane models of the same type design that 
are equipped with wing lift struts, the FAA is proposing an AD that 
would supersede AD 93-10-06. The proposed AD would 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. This proposed AD 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.

Cost Impact

    The FAA estimates that 22,000 airplanes in the U.S. registry would 
be affected by the proposed AD, that it would take approximately 8 
workhours per airplane to accomplish the proposed initial inspection, 
and that the average labor rate is approximately $60 an hour. Based on 
these figures, the total cost impact of the proposed 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 would 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 would eliminate the requirements of 
the proposed AD, and thus reduce the cost impact of the proposed 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 the proposed 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 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 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 14 
CFR part 39 of the Federal Aviation Regulations 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:

The New Piper Aircraft, Inc.: 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.     

[[Page 20145]]

                                                                        
PA-18, PA-18S, PA-18 ``105'' (Special), PA-    18-1 through 18-8309025, 
 18A, PA-18 ``125'' (Army L-21A), PA-18S        189001 through 1809032, 
 ``125'', PA-18AS ``125'', PA-18 ``135''        and 1809034 through     
 (Army L-21B), PA-18A ``135'', PA-18S           1809040.                
 ``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 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 provided no perceptible dents or external corrosion is found.
    (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 provided no 
external corrosion is found and all of the requirements included in 
the Appendix of this AD are met.
    (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 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) 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 paragraphs, 
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.

[[Page 20146]]

    (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.......  July 15, 1983.        
                                 Issue..........                        
2, 4, and 6....................  Revision.......  Mar. 30, 1984.        
                                 No. 1..........                        
a and 3........................  Revision.......  Apr. 20, 1984.        
                                 No. 2..........                        
------------------------------------------------------------------------

No repetitive inspections are required after installing these Jensen 
Aircraft wing lift strut fork assemblies; however, repetitive 
inspections 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 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.
    (h) This amendment supersedes AD 93-10-06, Amendment 39-8536.

Appendix to 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.''
    <bullet> 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.

[[Page 20147]]

    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 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.

    <bullet> 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.

    <bullet> 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.


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[GRAPHIC] [TIFF OMITTED] TP23AP98.005



    Issued in Kansas City, Missouri, on April 16, 1998.
Michael Gallagher,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. 98-10749 Filed 4-22-98; 8:45 am]
BILLING CODE 4910-13-P