Airworthiness Directives; Piper Aircraft Corporation PA-25 Series Airplanes

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]

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