DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2017-1059; Product Identifier 2017-CE-035-AD]
RIN 2120-AA64

Airworthiness Directives; Piper Aircraft, Inc. Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Supplemental notice of proposed rulemaking (SNPRM); reopening
of comment period.

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SUMMARY: The FAA is revising an earlier proposal for certain Piper
Aircraft, Inc. (Piper) Models PA-28-140, PA-28-150, PA-28-160, PA-28-
180, PA-28-235, PA-32-260, and PA-32-300 airplanes. This action revises
the notice of proposed rulemaking (NPRM) by including a revision to the
manufacturer's service information, including an additional inspection
method, and removing the requirement to install the access panel. The
FAA is proposing this airworthiness directive (AD) to address the
unsafe condition on these products. Since the actions in the revised
service information would impose an additional burden over those in the
NPRM, the FAA is reopening the comment period to allow the public the
chance to comment on these changes.

DATES: The comment period for the NPRM published in the Federal
Register on November 7, 2017 (82 FR 51583), is reopened.

The FAA must receive comments on this SNPRM by September 18, 2020.

ADDRESSES: You may send comments, using the procedures found in 14 CFR
11.43 and 11.45, by any of the following methods:

Federal eRulemaking Portal: Go to https://www.regulations.gov. Follow the
instructions for submitting comments.

Fax: 202-493-2251.

Mail: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC 20590.

Hand Delivery: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC 20590, between 9 a.m. and 5 p.m.,
Monday through Friday, except Federal holidays.

For service information identified in this SNPRM, contact Piper
Aircraft, Inc., 2926 Piper Drive, Vero Beach, Florida 32960; telephone:
(772) 567-4361; internet: www.piper.com. You may view this service
information at the FAA, Airworthiness Products Section, Operational
Safety Branch, 901 Locust, Kansas City, Missouri 64106. For information
on the availability of this material at the FAA, call (816) 329-4148.

Examining the AD Docket

You may examine the AD docket on the internet at https://www.regulations.
gov by searching for and locating Docket No. FAA-2017-1059;
or in person at Docket Operations between 9 a.m. and 5 p.m.,
Monday through Friday, except Federal holidays. The AD docket contains
this SNPRM, the regulatory evaluation, any comments received, and other
information. The street address for Docket Operations is listed above.
Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT: Dan McCully, Aerospace Engineer, FAA,
Atlanta ACO Branch, 1701 Columbia Avenue, College Park, Georgia 30337;
telephone: (404) 474-5548; fax: (404) 474-5606; email:
william.mccully@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to send any written relevant data, views, or
arguments about this proposed AD. Send your comments to an address
listed under the ADDRESSES section. Include "Docket No. FAA-2017-1059;
Product Identifier 2017-CE-035-AD" at the beginning of your comments.
The FAA will consider all comments received by the closing date and may
amend this proposed AD because of those comments.

Except for Confidential Business Information as described in the
following paragraph, and other information as described in 14 CFR
11.35, the FAA will post all comments we receive, without change, to
https://regulations.gov, including any personal information you
provide. The FAA will also post a report summarizing each substantive
verbal contact it receives about this proposed AD.

Confidential Business Information

Confidential Business Information (CBI) is commercial or financial
information that is both customarily and actually treated as private by
its owner. Under the Freedom of Information Act (FOIA) (5 U.S.C. 552),
CBI is exempt from public disclosure. If your comments responsive to
this NPRM contain commercial or financial information that is
customarily treated as private, that you actually treat as private, and
that is relevant or responsive to this NPRM, it is important that you
clearly designate the submitted comments as CBI. Please mark each page
of your submission containing CBI as "PROPIN." The FAA will treat
such marked submissions as confidential under the FOIA, and they will
not be placed in the public docket of this NPRM. Submissions containing
CBI should be sent to Dan McCully, Aerospace Engineer, FAA, Atlanta ACO
Branch, 1701 Columbia Avenue, College Park, Georgia 30337; telephone:
(404) 474-5548; fax: (404) 474-5606; email: william.mccully@faa.gov.
Any commentary that the FAA receives which is not specifically
designated as CBI will be placed in the public docket for this
rulemaking.

Discussion

The FAA issued an NPRM to amend 14 CFR part 39 by adding an AD that
would apply to certain serial-numbered Piper Models PA-28-140, PA-28-
150, PA-28-160, PA-28-180, PA-28-235, PA-32-260, and PA-32-300
airplanes. The NPRM was published in the Federal Register on November
7, 2017 (82 FR 51583). The NPRM was prompted by reports of significant
corrosion found in an area of the main wing spar not easily accessible
for inspection. The NPRM proposed to require installing inspection
access panels in the lower wing skin near the left and the right main
wing spars (if not already there), inspecting for corrosion,
and taking all necessary corrective actions if corrosion is found.

Actions Since the NPRM Was Issued

Since the FAA issued the NPRM, Piper revised its service
information to add a minimum thickness dimension for the top inboard
wing skin and to include procedures for reapplying corrosion preventive
compound if removed during the inspection. The FAA is incorporating
these revised procedures into the proposed AD. Also, at the request of
some commenters, the FAA has replaced the proposed requirement to
install access panels for the visual inspection with optional access
methods: The use of existing access panels, installation of access
panels, accessing the area during a concurrent inspection, or using a
borescope through existing holes or openings.

Comments

The FAA gave the public the opportunity to comment on the NPRM. The
following presents the comments received on the NPRM and the FAA's
response to each comment.

Requests Regarding the FAA's Justification of the Unsafe Condition

The Airline Owners and Pilots Association (AOPA) and five
individual commenters requested that the FAA provide more information
about the events surrounding the two damaged airplanes that prompted
this proposed AD. Specifically, the commenters asked about the history,
climate, storage, location, and operating conditions of the two damaged
airplanes. AOPA further requested that the FAA publish its Small
Airplane Risk Assessment (SARA) of the unsafe condition.

Four commenters requested that the NPRM be withdrawn as not
warranted or not justified as an unsafe condition.

The FAA agrees to provide additional information about the events
that prompted the NPRM. One of the subject airplanes is a Model PA-28-
140 registered in Chile, on which severe corrosion of the left-hand
main spar assembly was discovered during maintenance to add a wing
inspection panel. Corrosion damage of a similar extent was found in the
same location on a Model PA-28-161 registered in Scotland. The Model
PA-28-161 airplane had inspection access panels installed, but the
airplane had not been properly inspected. As FAA regulations do not
require owners to maintain records of an airplane's operating history,
the information requested by the commenters about the climate, storage,
and operating conditions of these airplanes is unknown.

The corrosion observed on the subject wing spars penetrated through
more than 25 percent of the cross sectional area, to the extent that
failure was imminent, and therefore qualified as a Primary Structure
Hazard Level 5 under the FAA's SARA process. A subsequent Corrective
Action Review Board determined that the similarity, extent, and
location of the corrosion in the subject airplanes poses a safety
concern requiring corrective action for airplanes with wings of a
similar design. The airplanes listed in the applicability of the
proposed AD have wings with the same cross sectional member, shape, and
material, and thus are subject to this same unsafe condition. The FAA
limited applicability to models of an older design that did not include
wing inspection access panels because of the likelihood that corrosion
has been overlooked. The FAA has not changed this proposed AD based on
these comments.

Request To Allow Borescope Inspection Instead of Installation of Access
Panels

Over thirty commenters requested the proposed AD allow a borescope
inspection method instead of installing access panels in the wing skin.

The commenters stated that the borescope inspection method is a
more cost-effective and less invasive option than the purchase and
installation of the Piper access panel kit. The borescope inspection
method also mitigates damage risk to the airplane structure associated
with cutting the wing skin to install the Piper kit. Several commenters
requested the proposed AD require installing smaller inspection holes
to facilitate a borescope inspection. Other commenters stated, in some
cases, existing access points such as inspection panels, removeable
fairings, and lightening holes provided adequate access to conduct a
borescope inspection.

The FAA agrees with allowing a borescope inspection method instead
of requiring the installation of access panels in the wing skin. This
SNPRM removes the proposed requirement to install the access panels.
Due to the many variations and types of inspection openings possible on
different model airplanes, it is not feasible for the FAA to specify
access options for each particular airplane. As a result, the FAA has
not changed the proposed AD to require smaller inspection holes.
Instead, the SNPRM proposes four options for gaining access to the
inspection area, including using a borescope through existing access
points.

Request To Access Inspection Area During Wing Tank Removal

Six commenters requested the proposed AD allow access to the
inspection area by removing the wing tank.

The FAA agrees and has changed this proposed AD to allow inspection
during concurrent maintenance, such as when the wing tank has been
removed, as an option for gaining access to the inspection area.

Request for a Definitive Corrosion Removal Parameter

William Goebel and Robert Nelson requested the FAA remove the
requirement to inspect for "any evidence of corrosion" and instead
provide criteria or a quantifiable measurement of unacceptable
corrosion. The commenters stated that the wording in the NPRM is vague
and will unnecessarily require corrective action and subsequent
material thickness measurements for minor surface corrosion

The FAA disagrees. Even with minor corrosion removal, the thickness
of the affected structure must be verified for remaining strength. The
criteria in the service information for determining the minimum
acceptable thickness of the wing components are based on actual
remaining strength computations for each component of the wing
structure. While some elements of the spar can sustain liberal material
removal and retain adequate strength without additional reinforcement,
other elements can sustain little or no reduction in thickness before
strength is compromised and repair is required. The FAA has not changed
the corrective action requirements for corrosion based on these
comments.

Request for Clarification of the Required Inspection Area

Andrew Durbin and Michael Dieck requested the FAA clarify the areas
to be inspected, as the instructions in Piper Service Bulletin No.
1304, dated August 23, 2017, are vague and contradictory and contain
errors.

The FAA agrees that the inspection area described in Piper Service
Bulletin No. 1304, dated August 23, 2017, is open to misinterpretation.
The FAA has changed the proposed AD to include specific inspection
areas.

Request Local Fabrication of the Inspection Access Panels

Donald Morris and Raymond Stone requested that the proposed AD
allow local fabrication of the inspection panels as an alternative to
purchasing the specified kit from Piper. One of these commenters
requested the AD include the materials and dimensions of the parts in
the kit so mechanics can fabricate these parts. The commenters stated
the inspection access panels require no special tooling or methods to
fabricate and are within the capability of most mechanics, and local
fabrication could save time and money for owners. Robert Nelson agreed
it should not be necessary to purchase the parts from Piper.
The FAA partially agrees. The FAA has changed the proposed AD to
remove the requirement to install access panels. Instead, this SNPRM
proposes to allow other methods of accessing the inspection area.
Because the proposed AD no longer requires installation of the Piper
kit, the commenters' request is no longer necessary.

Request for Exemption From Compliance

Kenneth Vida asked whether the proposed AD would apply to their
airplane. The commenter stated that the wings of the PA-28-180C were
removed and no corrosion found on the wing spars or the pocket in the
airframe. The wings were reinstalled in the summer of 2016 and the
airplanes resumed operating in April of 2017. The FAA infers that the
commenter is requesting credit for a prior maintenance event. Ross
Tracey requested that airplanes that have been inspected as specified
in Piper SB No. 1006 within the last two years be exempt from the
proposed AD.

The FAA disagrees. Piper SB No. 1006 specifies inspecting the spar
structure "behind the fuel tank," which is outboard of the inspection
area in the proposed AD. Accomplishment of SB No. 1006 alone would not
satisfy compliance with the proposed AD.

The FAA has revised the proposed AD to allow credit for prior
inspections performed in accordance with Piper Service Bulletin No.
1304, dated August 23, 2017, under certain conditions. For operators
who seek credit for other methods, under the provisions of paragraph
(j) of this AD, the FAA will consider requests for approval of an
alternative method of compliance (AMOC) if sufficient data is submitted
to substantiate that the method provides an acceptable level of safety.

Request To Update the Costs of Compliance

Five commenters, including AOPA, requested the FAA update the cost
of complying with the proposed AD. These commenters stated that pricing
for the Piper kit of $175 in the Cost of Compliance section is too low.
One of these commenters requested that the cost estimate include the
cost of applying a protective coating to the inspection panels to match
the airplane's existing exterior coating.

The FAA partially agrees. This SNPRM updates the cost of the access
panel kit, which is now proposed as an optional installation and not a
required installation. The cost analysis in AD rulemaking actions
typically includes only the costs associated with complying with the
AD. Accordingly, the FAA is not including the cost of applying a
matching protective coating because that activity is not required to
comply with any portion of the proposed AD.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Piper Service Bulletin No. 1304A, dated August 14,
2018. The service bulletin contains procedures for installing an
inspection access panel in the lower wing skin near the left and the
right main wing spars, if not already there, inspecting for corrosion,
and, if corrosion is found, taking all necessary corrective actions.
The service bulletin also contains procedures for applying corrosion
prevention and for verifying that the top inboard wing skin thickness
meets or exceeds the minimum thickness after corrosion is removed. This
service information is reasonably available because the interested
parties have access to it through their normal course of business or by
the means identified in the ADDRESSES section.

FAA's Determination

The FAA is proposing this AD because it evaluated all the relevant
information and determined the unsafe condition described previously is
likely to exist or develop in other products of the same type design.
Certain changes described above expand the scope of the NPRM. As a
result, the FAA determined that it is necessary to reopen the comment
period to provide additional opportunity for the public to comment on
this SNPRM.

Proposed Requirements of This SNPRM

This SNPRM would require inspecting the left and right main wing
spar for corrosion, and, if corrosion is found, taking all necessary
corrective actions.

Differences Between This SNPRM and the Service Information

Piper SB No. 1304A, dated August 14, 2018, provides the
manufacturer's procedures for installing access panels on the lower
skin of the left wing and the right wing for easier access to the left
and right main wing spar. This SNPRM does not propose a requirement to
install the access panels but would allow the installation as an option
to access the inspection area.

Costs of Compliance

The FAA estimates that this SNPRM would affect 11,476 airplanes of
U.S. registry.

The FAA estimates the following costs to comply with this SNPRM:

Inspection Costs

Installation of Access Panels

This proposed AD does not require the installation of the access
panels for the visual inspection; however, it allows the installation
of the panels, as one of four options, to access the inspection area.

On-Condition Costs

The extent of damage found during the required inspection could
vary significantly from airplane to airplane. The FAA has no way of
determining how much damage may be found on each airplane, the cost to
repair damaged parts on each airplane, or the number of airplanes that
may require repair.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to
issue rules on aviation safety. Subtitle I, section 106, describes the
authority of the FAA Administrator. Subtitle VII: Aviation Programs
describes in more detail the scope of the Agency's authority.

The FAA is issuing this rulemaking under the authority described in
Subtitle VII, Part A, Subpart III, section 44701: General requirements.
Under that section, Congress charges the FAA with promoting safe flight
of civil aircraft in air commerce by prescribing regulations for
practices, methods, and procedures the Administrator finds necessary
for safety in air commerce. This regulation is within the scope of that
authority because it addresses an unsafe condition that is likely to
exist or develop on products identified in this rulemaking action.

Regulatory Findings

The FAA determined that this proposed AD would not have federalism
implications under Executive Order 13132. This proposed AD would not
have a substantial direct effect 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.

For the reasons discussed above, I certify this proposed
regulation:

(1) Is not a "significant regulatory action" under Executive
Order 12866,

(2) Will not affect intrastate aviation in Alaska to the extent
that it justifies making a regulatory distinction, and

(3) Will not have a significant economic impact, positive or
negative, on a substantial number of small entities under the criteria
of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.

The Proposed Amendment

Accordingly, under the authority delegated to me by the
Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.

Sec. 39.13 [Amended]

2. The FAA amends Sec. 39.13 by adding the following new airworthiness
directive (AD):