[Federal Register Volume 60, Number 13 (Friday, January 20, 1995)]
[Proposed Rules]
[Pages 4119-4131]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-1427]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 92-CE-63-AD]


Airworthiness Directives; Piper Aircraft Corporation PA-25 Series 
Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Supplemental notice of proposed rulemaking (NPRM); Reopening of 
the comment period.

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SUMMARY: This document proposes to revise an earlier proposed 
airworthiness directive (AD) that proposed repetitively inspecting the 
wing forward spar fuselage attachment assembly for cracks or corrosion 
on certain Piper Aircraft Corporation (Piper) PA-25 series airplanes, 
and replacing or repairing any cracked or corroded part. Since issuance 
of the proposal, a second incident where the wing separated from one of 
the affected airplanes while in flight prompted the Federal Aviation 
Administration (FAA) to issue AD 93-21-12 (priority letter and 
subsequent Amendment 39-8763) to require a one-time inspection of the 
wing forward spar fuselage attachment assembly on these PA-25 series 
airplanes, with appropriate repair or replacement. The proposed action 
would retain this initial inspection, and propose a repetitive 
inspection. The actions specified by the proposed AD are intended to 
prevent possible in-flight separation of the wing from the airplane 
caused by a cracked or corroded wing forward spar fuselage attachment 
assembly.

DATES: Comments must be received on or before March 27, 1995.

ADDRESSES: Submit comments in triplicate to the FAA, Central Region, 
Office of the Assistant Chief Counsel, Attention: Rules Docket No. 92-
CE-63-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.
    Information that relates to the proposed AD may be inspected at the 
Rules Docket at the address above.

FOR FURTHER INFORMATION CONTACT:
Christina Marsh, Aerospace Engineer, FAA, Atlanta Aircraft 
Certification Office, Campus Building, 1701 Columbia Avenue, suite 2-
160, College Park, Georgia 30337-2748; telephone (404) 305-7362; 
facsimile (404) 305-7348.

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. 92-CE-63-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 Assistant Chief Counsel, 
Attention: Rules Docket No. 92-CE-63-AD, Room 1558, 601 E. 12th Street, 
Kansas City, Missouri 64106.

Discussion

    A proposal to amend part 39 of the Federal Aviation Regulations (14 
CFR part 39) to include an AD that would apply to certain Piper PA-25 
series airplanes was published in the Federal Register on September 8, 
1993 (58 FR 47227). The action proposes to require repetitively 
inspecting the wing forward spar fuselage attachment assembly for 
cracks or corrosion, and replacing or repairing any cracked or corroded 
part.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the eight comments received from two commenters.
    One commenter (referred to as Commenter No. 1 hereon) states that 
the wings must be removed from the fuselage in order to properly 
inspect the wing forward spar fuselage attachment assembly. The FAA 
concurs, and this was the intent of the proposal. The FAA has specified 
removal of the wings in the supplemental NPRM to eliminate any 
confusion regarding this matter.
    Commenter No. 1 recommends a one-time inspection of the assembly, 
consisting of removing the wing forward spar fuselage attach fitting 
from the fuselage structure. The FAA does not concur with this 
recommendation. The [[Page 4120]] wing forward spar fuselage attach 
fitting is an integral part of the tubular fuselage attach cluster, and 
the FAA believes that rewelding this part to the original structure 
after removal for inspection would present a safety problem. The 
proposal is unchanged as a result of this comment.
    Commenter No. 1 also states that Appendix D in part 43 of the 
Federal Aviation Regulations (14 CFR part 43, Appendix D) describes the 
scope and detail of an annual and 100-hour time in-service (TIS) 
inspection, and that this inspection includes the same area as that 
specified in the proposal. The FAA acknowledges that 14 CFR part 43, 
Appendix D, does address the area of the proposed inspection, but does 
not specify removing the wings to accomplish the proposed wing forward 
spar fuselage attachment inspection. The FAA has determined that wing 
removal must be accomplished in order to detect cracks or corrosion in 
this assembly. The proposal is unchanged as a result of this comment.
    Another commenter (referred to as Commenter No. 2 hereon) 
recommends that the mechanic saturate the attach bolts with penetrating 
oil to facilitate removal because they are extremely difficult to 
remove. The FAA concurs that these bolts could be difficult to remove 
and has added a NOTE to the proposal to recommend this idea.
    Paragraph (b) of the proposal specifies: ``thoroughly clean around 
the wing forward spar fuselage attachment fittings with water (only).'' 
Commenter No. 2 states that water will not properly remove all chemical 
residues. The FAA concurs and has removed this statement from the 
proposal. The proposed inspection would require preparation to remove 
paint to ensure a proper inspection surface.
    Commenter No. 2 also recommends inspections every two years and any 
time the wings are removed. The original proposal did not include 
Commenter No. 2's inspection compliance recommendation because of the 
inspection criteria available. Since that time, the FAA has established 
ultrasonic inspection procedures. Confidence in these inspection 
procedures has allowed the FAA to extend the proposed compliance time 
to two years and incorporate these procedures into the proposal.
    In addition, Commenter No. 2 recommends alternate inspection 
procedures of magnaflux or x-ray. The FAA believes that magnaflux and 
x-ray are not viable inspection alternatives because of the design and 
location of the wing forward spar fuselage attachment fitting. For this 
reason, the proposal is unchanged as a result of this comment.
    Commenter No. 2 suggests that the FAA require only a one-time 
inspection to those airplanes that have incorporated Supplemental Type 
Certificate (STC) SA501SW. The FAA does not concur with this 
suggestion. STC SA501SW does not require modification to the wing 
forward spar fuselage attachment fittings, and, therefore does not 
relate to the proposal. The proposal is unchanged as a result of this 
comment.
    No comments were received concerning the FAA's determination of the 
cost upon the public.
    Since issuance of the proposal, the FAA became aware of a similar 
accident on a Piper Model PA-25-150 airplane. This airplane had accrued 
over 5,000 hours TIS. Because of the wide variation in hours TIS 
accrued on the two airlines involved in the referenced accidents (over 
10,000 and over 5,000), the FAA determined that immediate initial 
inspections were required on all Piper Models PA-25-150, PA-25-235, and 
PA-25-260 airplanes, and issued AD 93-21-12, Amendment 39-8763 (58 FR 
65104, December 13, 1993). This AD requires inspecting (one-time) the 
wing forward spar fuselage attachment assembly for cracks or corrosion, 
and replacing or repairing any cracked or corroded part.
    After examining the circumstances and reviewing all available 
information related to the accident described above, the FAA has 
determined that the one-time inspection required by AD 93-21-12 should 
be repetitive and the comment period for the initial proposal should be 
reopened to allow the public additional time to comment on this 
proposed action.
    Since an unsafe condition has been identified that is likely to 
exist or develop in other Piper PA-25 series airplanes of the same type 
design, the proposed AD would require repetitively inspecting the wing 
forward spar fuselage attach fittings for cracks or corrosion, and 
replacing or repairing any cracked or corroded part.
    The compliance time for the proposed AD is presented in calendar 
time instead of hours TIS. The FAA has determined that a calendar time 
for compliance is the most desirable method because the unsafe 
condition described by the proposed AD is caused by corrosion. 
Corrosion can occur on airplanes regardless of whether the airplane is 
in service or in storage. Therefore, to ensure that corrosion is 
detected and corrected on all airplanes within a reasonable period of 
time without inadvertently grounding any airplanes, a compliance 
schedule based upon calendar time instead of hours TIS is proposed.
    The FAA estimates that 1,272 airplanes in the U.S. registry would 
be affected by the proposed AD, that it would take approximately 30 
workhours per airplane to accomplish the proposed 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 $2,289,600. This figure is based on the assumption that 
no affected airplane owner/operator has accomplished the proposed 
inspections. This figure also does not reflect the cost of repetitive 
inspections. The FAA has no way of determining how many repetitive 
inspections a particular owner/operator may incur.
    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 Rule 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:

    [[Page 4121]] Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 
49 U.S.C. 106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing AD 93-21-12, Amendment 39-
8763 (58 FR 65104, December 13, 1993), and by adding a new AD to read 
as follows:

Piper Aircraft Corporation: Docket No. 92-CE-63-AD. Supersedes AD 
93-21-12, Amendment 39-8763.

    Applicability: Models PA-25-150, PA-25-235, and PA-25-260 
airplanes (all serial numbers), certificated in any category.
    Compliance: Required within the next 12 calendar months after 
the effective date of this AD, unless already accomplished, and 
thereafter at intervals not to exceed 24 calendar months (except as 
noted in paragraph (h) of this AD).
    To prevent possible in-flight separation of the wing from the 
airplane caused by a cracked or corroded wing forward spar fuselage 
attachment assembly, accomplish the following:
    (a) Gain access to the left and right wing forward spar fuselage 
attach fittings by removing the screws retaining the wing fairing. 
Dismantle the wing fillet by removing the screws on the aft edge top 
and bottom and removing the wing fairing (see Figure 1 of the 
Appendix to this AD).
    (b) Remove the wing attach bolts and wing. Remove paint from the 
wing forward spar fuselage attachment fittings and surrounding 
areas; do not sand blast because it may obscure surface indications.

    Note 1: Saturation of the bolts with a penetrating oil may 
facilitate removal.

    (c) Visually inspect the wing forward spar tubular fuselage 
attach cluster for damage (cracks, corrosion, rust, or gouges). 
Prior to further flight, repair or replace any damaged tubular 
member with equivalent material in accordance with FAA Advisory 
Circular (AC) No. 43.13-1A, Acceptable Methods, Techniques, 
Practices--Aircraft Inspection and Repair.
    (d) Inspect (using both dye penetrant and ultrasonic procedures) 
the wing forward spar fuselage attach fitting assembly, part numbers 
(P/N) 61005-0 (front spar fitting assembly) and 61006-0 (front spar 
fitting) for Model PA-25-150; and P/N 64412-0 (front spar fitting 
assembly) and 64003-0 (front spar fitting) for Models PA-25-235 and 
PA-25-260, for corrosion and cracks in accordance with the Appendix 
to this AD.
    (1) If any corrosion is found that meets or exceed the 
parameters presented in the Appendix to this AD or any cracks are 
found, prior to further flight, replace the forward spar fuselage 
tubular attach cluster with serviceable parts as specified in the 
Appendix to this AD.
    (2) The inspection procedures in the Appendix of this AD, except 
for the dye penetrant inspection procedures, must be accomplished by 
a Level 2 inspector certified using the guidelines established by 
the American Society for Non-destructive Testing, or MIL-STL-410 or 
equivalent. A mechanic with at least an Airframe license may perform 
the dye penetrant inspection.
    (e) Replacement parts required by this AD shall be of those 
referenced and specified in either Figures 3a and 3b, 4a and 4b, or 
5a and 5b (as applicable), included as part of the Appendix of this 
AD.
    (f) Prime and paint all areas where parts were replaced or where 
paint is bubbled or gone. Use epoxy paint and primer, and, after 
paint has cured, rust inhibit the entire area.
    (g) Reinstall all items that were removed.
    (h) If a new cluster is installed into the fuselage frame, 
repetitive inspections are not required until five years after the 
replacement date on the respective fuselage side. This cluster may 
be replace every five years as an alternative to the repetitive 
inspections.
    (i) 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.
    (j) 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), Campus Building, 1701 Columbia Avenue, 
suite 2-160, College Park, Georgia 30337-2748. 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 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Atlanta ACO.

    (k) Appendix 1 of this AD may be obtained from the Atlanta ACO 
at the address specified in paragraph (j) of this AD. This document 
or any other information that relates to this AD may be inspected at 
the FAA, Central Region, Office of the Assistant Chief Counsel, Room 
1558, 601 E. 12th Street, Kansas City, Missouri.

Appendix--Procedures and Requirements for Wing Forward Spar 
Attachment Assembly Inspection of Piper PA-25 Series Airplanes

Equipment Requirements

    1. A portable combination ultrasonic flaw detector with both an LED 
thickness readout and an A-trace with thickness gate display.
    2. An ultrasonic probe with the following: a 15 MHz 0.25-inch 
diameter with a 0.375-inch plastic delay line. An equivalent permanent 
delay line transducer that provides adequate sensitivity and resolution 
to measure a 0.050-inch steel shim can also be used.
    3. Three steel shims within the range of 0.050 to 0.100 inches are 
required. To ensure proper calibration, the steel shims should be 
smooth and free of dirt. In order to verify the shim thickness, use a 
calibrated micrometer to measure the steel shims.
    4. Either glycerin, 3-in-1 oil, or equivalent ultrasonic couplants 
are used to conduct this test set-up and inspection. Water-based 
couplants are not permitted because of the possibility of initiating 
long-term corrosion of the wing forward spar fuselage attachment 
fittings.

    Note: Couplant is defined as ``a substance used between the face 
of the transducer and test surface to improve transmission of 
ultrasonic energy across this boundary or interface.''

    Note: If surface pitting is found on either side of the fitting 
ears, lightly sand the surface to obtain a smooth working surface. 
Removal of surface irregularities such as pits, rust, scale, and 
paint will enhance the accuracy of the inspection technique.

Instrument Calibration

    1. Turn the instrument power on and check the battery charge 
status. The instrument should have at least 40-percent of available 
battery life. The screen brightness and contrast of the display screen 
should match the environmental conditions (i.e., outside sunlight or 
inside a hangar).
    2. Depending on the ultrasonic instrument used, select or verify 
the single element transducer setting from the probe selection menu. If 
a removable delay line is used, unscrew the plastic delay line from the 
transducer. Add couplant to the base of the delay line, then reattach 
the delay line.
    3. Obtain steel shims with known or measured thickness at or near 
0.050, 0.075, and 0.100 inches. At least one steel shim shall be 
greater than 0.095 inches, one less than or equal to 0.050 inches, and 
one between these two values. Place the probe on the thickest steel 
shim using couplant. Adjust the gain setting to increase the backwall 
signal from this steel shim. An A-trace will appear on the screen and a 
thickness readout will appear on the display. The signal on the screen 
from left to right shows: the initial pulse, the delay line (the front 
surface of the steel shim) and the backwall echo of the steel shim. A 
second and third multiple backwall echo may also be seen on the A-
trace. Enable the thickness gate. Adjust the thickness gate to initiate 
at the delay line to steel shim interface and terminate at the first 
backwall echo.
    4. Place the probe on the thinnest steel shim using couplant. 
Adjust the damping, voltage and pulse width to obtain the maximum 
signal response and highest resolution on this steel shim. These 
settings can vary from probe to probe and are somewhat dependent on 
operator preferences.
    5. To stabilize the interface synchronization, adjust the 
electronic [[Page 4122]] triggering (blocking gate) to approximately 
three quarters of the distance between the initial pulse and the delay 
line interface echo. The thickness gate should initiate at the delay 
line interface echo and terminate at the first backwall echo.
    6. Depending on the instrument and probe, select positive half-wave 
rectified signal display or negative half-wave rectified signal 
display. This selection should give the best signal display on the 
thinnest steel shim. Select the interface synchronization. This 
selection automatically starts the thickness gate at the delay time 
corresponding to the tip of the plastic delay line.
    7. Couple the probe to the thickest steel shim using couplant. 
Adjust the range so the A-scan display reads from 0.000 to 0.300 
inches. Several multiple backwall echoes will disappear from the 
screen.
    8. Adjust the thickness gate to trigger on the first return signal. 
If instability of the gate trigger occurs, adjust the gain and/or 
damping to stabilize the thickness reading. A thickness readout should 
be present on the screen and near the known steel shim thickness.
    9. Adjust the velocity to 0.231 inches/microseconds. The thickness 
reading should be the known steel shim thickness. Couple the transducer 
to the thinnest steel shim. If the thickness readout does not agree 
with the known thickness, adjust the fine delay setting to produce the 
known thickness. Re-check the thickest step. If the readout does not 
indicate the correct thickness re-adjust the fine delay setting. After 
this adjustment is made, record the thickness values for each of the 
steel shims on a set-up sheet.
    10. Calculate the percent error for each measured steel shim. The 
maximum allowable percent error should not exceed 3-percent.

Inspection Procedures

    1. Add couplant to the outside inspection surface (Refer to Figures 
3a, 4a and 5a, as applicable). Add the appropriate gain to obtain the 
backwall echo from the inspection surface. If the gain setting is 
adjusted, re-check the thickness values on the steel shims. To assure 
proper coupling to the test sample, twist the probe clockwise and 
counter-clockwise (with a 45-degree twist) and maintain contact with 
the test surface. During the articulation of the probe, observe the A-
trace on the screen and stop the probe twist at the point of adequate 
back surface signal amplitude to trigger the thickness gate on the 
first half-cycle. Measure and record the thickness. Repeat the above 
process at eight equally-spaced locations around the surface. The weld 
bead near the spar cluster may be hard to access. Find a suitable 
location near the weld and measure the thickness.
    2. Add couplant to the inside inspection surface (Refer to Figures 
3a, 4a and 5a, as applicable). Add the appropriate gain to obtain the 
backwall echo from the inspection surface. To assure proper coupling to 
the test sample, twist the probe (clockwise and counter-clockwise with 
a 45-degree twist). During the articulation of the probe, observe the 
A-trace on the screen and stop the probe twist at the point of adequate 
back surface signal amplitude to trigger the thickness gate on the 
first half-cycle. Measure and record the thickness. Repeat the above 
process at eight equally-spaced locations around the surface.
    3. If a thickness reading in any one of the eight locations from 
paragraph 1. of the Inspection Procedures section (outside section 
surface) is .085-inch or less for the PA25-150 Model or .055-inch or 
less for the PA25-235 and PA25-260 Models, or if a thickness reading in 
any one of the eight locations from paragraph 2. of the Inspection 
Procedures section (inside section surface) is .055-inch or less for 
the PA25-150 Model or .085-inch or less for the PA25-235 and PA25-260 
Models, prior to further flight, replace the forward spar fuselage 
tubular attach cluster with serviceable parts in accordance with FAA AC 
No. 43.13-1A, Acceptable Methods, Techniques, Practices--Aircraft 
Inspection and Repair. This procedure requires the following:
    a. Provide for the alignment of the airframe with an appropriate 
alignment fixture in accordance with FAA AC No. 43.13-1A, Acceptable 
Methods, Techniques, Practices--Aircraft Inspection and Repair.
    b. Cut the tubular members as referenced and specified in Figure 2 
and either Figures 3a and 3b; Figures 4a and 4b; or Figures 5a and 5b, 
as applicable.
    c. Fabricate a cluster using all applicable part numbers referenced 
in Figures 3b, 4b, or 5b, as applicable; and
    d. Splice the new cluster into the fuselage frame.

Dye Penetrant Inspection

    Inspect the wing forward spar fuselage attach fitting assembly for 
cracks using FAA-approved dye penetrant methods. If any cracks are 
found, prior to further flight, replace the forward spar fuselage 
tubular attach cluster with serviceable parts in accordance with FAA AC 
No. 43.13-1A, Acceptable Methods, Techniques, Practices-Aircraft 
Inspection and Repair. This procedure requires the following:
    1. Provide for the alignment of the airframe with an appropriate 
alignment fixture in accordance with FAA AC No. 43.13-1A, Acceptable 
Methods, Techniques, Practices-Aircraft Inspection and Repair.
    2. Cut the tubular members as referenced and specified in Figure 2 
and either Figures 3a and 3b; Figures 4a and 4b; or Figures 5a and 5b, 
as applicable.
    3. Fabricate a cluster using all applicable part numbers referenced 
in Figures 3b, 4b, or 5b, as applicable; and
    4. Splice the new cluster into the fuselage frame.

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    Issued in Kansas City, Missouri, on January 12, 1995.
Barry D. Clements,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. 95-1427 Filed 1-19-95; 8:45 am]
BILLING CODE 4910-13-C