[Federal Register Volume 77, Number 180 (Monday, September 17, 2012)]
[Rules and Regulations]
[Pages 56993-57001]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2012-22529]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2011-0639; Directorate Identifier 2011-CE-016-AD;
Amendment 39-17169; AD 2012-17-06]
RIN 2120-AA64
Airworthiness Directives; Piper Aircraft, Inc. Airplanes
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final rule.
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SUMMARY: We are adopting a new airworthiness directive (AD) for certain
Piper Aircraft, Inc. Models PA-24, PA-24-250, and PA-24-260 airplanes.
This AD was prompted by reports of cracks developing in the stabilator
horn assembly. This AD requires replacement of the stabilator horn
assembly and/or repetitive inspections of the stabilator horn assembly
for corrosion or cracks, as applicable. Corrosion or cracks could lead
to failure of the stabilator horn. Consequently, failure of the
stabilator horn could lead to a loss of pitch control in flight. We are
issuing this AD to correct the unsafe condition on these products.
DATES: This AD is effective October 22, 2012.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in the AD as of October 22,
2012.
ADDRESSES: For service information identified in this AD, contact Piper
Aircraft, Inc., 2926 Piper Drive, Vero Beach, Florida 32960; telephone:
(772) 567-4361; fax: (772) 978-6573; Internet: http://www.newpiper.com/company/publications.asp. You may review copies of the referenced
service information at the FAA, Small Airplane Directorate, 901 Locust
St., 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 http://www.regulations.gov; or in person at the Docket Management Facility
between 9 a.m. and 5 p.m., Monday through Friday, except Federal
holidays. The AD docket contains this AD, the regulatory evaluation,
any comments received, and other information. The address for the
Docket Office (phone: 800-647-5527) is Document Management Facility,
U.S. Department of Transportation, Docket Operations, M-30, West
Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE.,
Washington, DC 20590.
FOR FURTHER INFORMATION CONTACT: Gregory K. Noles, Aerospace Engineer,
FAA, Atlanta Aircraft Certification Office, 1701 Columbia Avenue,
College Park, Georgia 30337; phone: (404) 474-5551; fax: (404) 474-
5606; email: [email protected].
SUPPLEMENTARY INFORMATION:
Discussion
We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR
part 39 to include an AD that would apply to the specified products.
That
[[Page 56994]]
NPRM published in the Federal Register on June 22, 2011 (76 FR 36395).
That NPRM proposed to require replacement of the stabilator horn
assembly and/or repetitive inspections of the stabilator horn assembly
for corrosion or cracks, as applicable.
Comments
We gave the public the opportunity to participate in developing
this AD. The following presents the comments received on the proposal
and the FAA's response to each comment.
Support for the Proposed Initial Inspection
Comments from Kristin Amelia Winter, Charles Parker, Carl
Schoolcraft, Dave Fitzgerald for the International Comanche Society
(ICS), Hans Neubert for the ICS, Brian Kotso, and John F. Murray were
supportive of the AD's requirement for an initial inspection.
We did not change this final rule AD action based on these
comments.
Request FAA To Withdraw NPRM (76 FR 36395, June 22, 2011) Due to
Adequacy of External Inspections
Phil Ciholas requested we reconsider the NPRM (76 FR 36395, June
22, 2011) requirements and noted that even the most severe horn
cracking reported (propagated through the part to an exterior surface
and was visually detectable without disassembly) had not resulted in
complete horn failure or the severity of loss of control postulated in
the justification for the AD. The commenter stated that no loss of
control incidents or accidents have ever been documented that can be
attributed to this failure mode. Given the statistical distribution of
cracks reported, the ability of existing external inspections to detect
cracks prior to complete failure of the horn, and the lack of any
actual complete failures; the commenter felt the internal inspection
requiring disassembly is unwarranted on most aircraft, especially
recent serial number aircraft, unless there is other evidence of
potential issues observed on a particular aircraft. We infer the
commenter requested to withdraw the current proposal.
We disagree with the request to withdraw the NPRM (76 FR 36395,
June 22, 2011). A cracked stabilator horn coupled with the aircraft
flight envelope conditions could create an unsafe scenario even though
there has not been an in-flight event. A cracked stabilator horn
reduces the aircraft's structural load limits.
We did not change this final rule AD action based on these
comments.
Request To Clarify Applicability (Affected Part Numbers (P/Ns) and
Configurations)
David Ray Fitzgerald, Robert (no last name given), Patrick D.
Donovan, Edward P. Horan, Steven Fischer, Phil Ciholas, Dave Fitzgerald
for ICS, Daniel Jacob Katz, Arthur John Beyer, Hans Neubert for the
ICS, Brian Kotso, John F. Murray, and Dennis Boykin requested we
clarify the applicability to clearly state the affected horn P/Ns and
clarify whether other current and future horns (supplemental type
certificates (STC), and so forth) are/will be affected. The commenters
noted that the text of the proposed AD did not clearly state the
affected part numbers.
Robert (no last name given), Steven Fischer, Daniel Jacob Katz,
Hans Neubert for ICS, and John F. Murray also requested we address the
configuration of Models PA-24, PA-24-250, and PA-24-260 airplanes using
the same horn but installed with thicker torque tubes used on the
Models PA-24-400, PA-30, and PA-39 airplanes as the proposed AD did not
currently make mention of this configuration. They requested we
consider excluding the airplanes configured with the thicker torque
tubes from the applicability or including them as terminating action.
Phil Ciholas, Arthur John Beyer, and Dennis Boykin requested we
address potential material and process changes during production of the
Models PA-24, PA-24-250, and PA-24-260 airplanes, amending the NPRM (76
FR 36395, June 22, 2011) to apply to only those aircraft that have
experienced issues.
Dennis Boykin noted that the manufacturing cycle between the
original castings (about 1957) and the final production in 1972 of the
Model PA-24-260 airplane precluded the requirement to ensure that
similar castings, raw materials, and processes were in place, not just
a similar design. Dennis Boykin was not aware of any Model PA-24-260
airplane's stabilator horn that has been separated, inspected, and
found deficient.
We partially agree with the commenters. We agree with clarifying
the affected P/Ns because the issue is specific to the combination of
the P/N and models in the original NPRM (76 FR 36395, June 22, 2011).
However, we disagree with excluding aircraft with the thicker torque
tube installed or making the installation of the thicker torque tube a
terminating action. No documentation has been supplied to provide
approval for the installation of thicker torque tubes on the Models PA-
24, PA-24-250, or PA-24-260 airplanes, and the torque tube is not the
only contributing factor to the unsafe condition. The FAA has
determined the condition is likely to exist or develop in other
products of the same type design. We have insufficient data to show
that airplanes modified with the thicker torque tube do not have the
unsafe condition.
We also disagree with excluding stabilator horns manufactured later
in the production cycle. We have no record of castings, raw materials,
and/or processes changing significantly enough to provide justification
to exclude those airplanes from this AD action.
If an owner/operator submits substantiating data to support the
installation of the thicker torque tube as an alternative method of
compliance (AMOC) to this requirement, the FAA will review and consider
all AMOC requests we receive provided they follow the procedures in 14
CFR 39.19 and this AD.
We changed the AD's applicability in this final rule AD action to
include the horn P/N.
Request To Lower Torque Value for Horn Installation
Lawrence La Beau, Charles Parker, Eric Paul, Tom Veatch, Ivan R.
Wilson, Patrick D. Donovan, Ken E. Shaffer, Patric Barry, John Trudel,
Carl Schoolcraft, Phil Ciholas, Dave Fitzgerald for the ICS, Andrew
Detsch, Hans Neubert for the ICS, Brian Kotso, John F. Murray, and
Allan H. Bieck requested that the AD state an appropriate lower shear
nut torque value for the bolts common to the stabilator horn and torque
tube. Phil Ciholas requested we add horn deformation limits as a way to
control the installation torque and related stress corrosion cracking.
Charles Parker, Eric Paul, Tom Veatch, Ivan R. Wilson, Patric Barry,
John Trudel, Dave Fitzgerald for the ICS, Hans Neubert for the ICS, and
Brian Kotso requested we consider an initial inspection and
reinstallation with the lower torque value as terminating action for
the AD. Eric Paul and John F. Murray requested we lower the torque
value of the stop collar bolts. Phil Ciholas requested we consider
switching to shear nuts when any work is done on the joint.
The commenters stated over-torque is the root cause of the stress
corrosion condition and the procedure does not clearly require a lower
torque value. None of the commenters provided justification for the use
of stop collar bolts separate from the horn bolts or for the shear
nuts.
We agree with adding the installation torque value for the bolts
common to the horn and torque tube into the AD
[[Page 56995]]
procedures because it is a factor in mitigating the unsafe condition.
We will also coordinate with the airplane's manufacturer on clarifying
the airplane maintenance manual procedures for torque of these bolts.
However, we disagree with adding an initial inspection and
reinstallation of the torque tube with the lower torque value as
terminating action for the AD. Although the torque value is a
contributing factor, it is not the only factor (others are balance arm
interference fit, basic material susceptibility, and corrosion
potential).
No sufficient correlation has been established between the torque
value and deformation and subsequent stress corrosion cracking.
Consequently, we disagree with adding horn deformation limits as a way
to control the installation torque and related stress corrosion
cracking.
We disagree with mandating a lower torque value of the stop collar
bolts or mandating a switch to shear nuts when any work is done on the
joint. The stop collar bolts did not contribute to the unsafe
condition, and we cannot mandate actions through an AD that are
unnecessary to correct the unsafe condition. There is no current data
for approval to change the configuration to shear nuts.
We changed the AD by adding the installation torque value for the
bolts common to the horn and torque tube into the AD procedures.
Request To Use Thicker Torque Tube With Horn
Lawrence La Beau, Randy Black, Anonymous, Donald Dummer, Albert
Powers, Steven Fischer, Stewart Campbell, Miller Duffield Einsel,
Robert, Eric Paul, Tom Veatch, Patric Barry, John Trudel, Edward P.
Horan, Carl Schoolcraft, Steven Fischer, Phil Ciholas, Dave Fitzgerald
for the ICS, Daniel Jacob Katz, Hans Neubert for the ICS, Lawrence E.
Pride, Jim Ritter, Brian Kotso, and John F. Murray noted thicker torque
tubes discovered during the ICS' survey targeted inspections at the
horn. This survey was beyond the current maintenance program. The
commenters cited the thicker torque tube could lessen the potential for
stress corrosion cracking due to horn deformation. Robert, Steven
Fischer, Daniel Jacob Katz, Hans Neubert for ICS, and John F. Murray
requested we address the configuration of Models PA-24, PA-24-250, and
PA-24-260 airplanes with the subject horn but installed with thicker
torque tubes.
We do not agree with the commenters. We disagree with authorizing
the installation of the thicker torque tube. No documentation has been
supplied to provide approval for installation of the thicker torque
tube configuration on any airplanes affected by this AD.
The FAA will review and consider any AMOC to support the
installation of the thicker tube provided it follows the procedures in
14 CFR 39.19 and this AD.
We did not change this final rule AD action based on these
comments.
Request To Provide for a Terminating Action to the Repetitive
Inspections
Kristin Amelia Winter, Lawrence Zubel, Charles Parker, Randy Black,
Donald Dummer, Steven Fischer, Stewart Campbell, Miller Duffield
Einsel, Eric Paul, Tom Veatch, Ivan R. Wilson, Patric Barry, Steven
Fischer, Phil Ciholas, Dave Fitzgerald for the ICS, Daniel Jacob Katz,
Hans Neubert for the ICS, Jim Ritter, Brian Kotso, and John F. Murray
requested a terminating action to the repetitive inspections. All the
commenters proposed various actions (that is, use of lower installation
torque value, installation of a thicker torque tube, installation of
replacement horn by way of Australian Civil Aviation Safety Authority
(CASA) CASA Supplemental Type Certificate (STC) SVA 532, and
terminating action based on additional data collected during the
inspections) with varying levels of supporting data.
We disagree because no proposed terminating action eliminates all
the contributing factors to the unsafe condition. The individual
proposed actions have been addressed in other requested changes to the
AD. The inspection or replacement programs will manage the issue to an
acceptable level of risk.
We will consider proposals for a terminating action as an AMOC
provided the procedures of 14 CFR 39.19 and this AD are followed.
We did not change this final rule AD action based on these
comments.
Request To Credit for Previous Compliance
Commenters David Charles Meigs, Randy Black, Steven Fischer, Hans
Neubert for the ICS, and Brian Kotso noted that operators have
typically been allowed credit for previous compliance in AD actions.
All commenters requested provision for credit when compliance to the
requirements has already been accomplished.
We agree that credit should be given when compliance to the
requirements has already been done. The AD already allows for such
credit by stating ``unless already done'' in paragraph (f) of the AD.
As long as the requirements of the AD are followed, credit is
available. Any other actions taken would need to be submitted as an
AMOC following paragraph (h) of the AD.
We did not change this final rule AD action based on these
comments.
Request To Clarify the AD Applicability to Replacement Parts
Commenters David Charles Meigs, Randy Black, Steven Fischer, Hans
Neubert for the ICS, Brian Kotso stated that the AD applicability is
not clearly defined in terms of both the susceptible horn part number
and the affected models. Several commenters request clarification of
the AD applicability to replacement parts, particularly the horn in
CASA STC SVA 532.
We partially agree with clarification on the applicability because
the focus of this AD is the horn P/N as discussed in the previous issue
``Request To Clarify Applicability.'' We disagree with specifically
addressing the CASA STC because the STC is still under review for FAA
validation and not all design issues have been addressed at this point.
Any action relating the STC to the AD will be documented during the FAA
review of the CASA STC.
As discussed previously, we changed the AD's applicability to
include the horn P/N.
Request To Increase Initial Compliance Time
Patric Barry and Phil Ciholas expressed concerns with the
availability of parts and shop capacity. The commenters requested an
increase in the initial compliance time.
We disagree with the commenters. The unsafe condition must be
addressed in a timely manner. The FAA will consider AMOCs following the
procedures in 14 CFR 39.19 and this AD to address any potential parts
availability or shop capacity issues.
We did not change this final rule AD action based on these
comments.
Request To Change Units of Compliance Times
Commenters Randy Black, Patrick D. Donovan, Carl Schoolcraft, Hans
Neubert for the ICS, John F. Murray, and Allan H. Bieck requested
changing compliance time criteria. Patrick D. Donovan, Hans Neubert for
the ICS, and John F. Murray asked that only calendar time be used for
compliance times. Carl Schoolcraft and Allan H. Bieck requested that
only TIS be used for compliance times. The commenters noted that stress
corrosion cracking (SCC) is a time-related function and not TIS. Carl
Schoolcraft noted the calendar time limit to be arbitrary and to have
no
[[Page 56996]]
bearing on the condition of the horn. Allan H. Bieck commented TIS is
what puts strain on the horn, not idle calendar time while the aircraft
sits in a hangar.
We disagree with eliminating the calendar time compliance. Calendar
time is a key factor in SCC. We also disagree with removing the
operational time (TIS) requirement as corrosion in the torque tube is a
contributing factor, and the established actions for the corrosion
currently have both a calendar and TIS requirement. We will retain our
compliance time using both calendar time and TIS.
We did not change this final rule AD action based on these
comments.
Request To Eliminate the Repetitive Inspection Requirement
Kristin Amelia Winter, Charles Parker, Albert Powers, Ken E.
Shaffer, John Trudel, Dave Fitzgerald for the ICS, Phil Ciholas, and
Brian Kotso requested eliminating the repetitive inspection
requirement. Commenters justify eliminating the repetitive inspections
by stating the cracks do not appear to be time or use related, there is
low or no history of cracking in the fleet, there have been no
catastrophic horns failures in service, and there is potential for
terminating action.
We do not agree because SCC is inherently time-related and
indirectly driven by operational usage. Not all aircraft will crack,
and those that do will not crack at the same time. SCC has several
contributing factors that add to the variability. For instance, typical
fatigue cracking includes scatter factors on the order of four to
determine the appropriate intervals to take action. While high-time
aircraft with no cracking is useful data, it does not eliminate the
need for action. As for the volume of findings, the quantity compared
to the entire fleet size is low. However, when measured against the
quantity of valid inspections performed, the find rate is as high as 20
percent.
It is also true that no parts have failed catastrophically in
flight and the findings have been during the ICS' survey targeted at
the horn. Note that this survey was beyond the current required
maintenance program. A cracked horn coupled with the aircraft flight
envelope conditions could still create an unsafe scenario even though
there has not been an in-flight event. In fact, the service history
provides evidence of extensive cracking on both sides of the torque
tube bore leading to the potential unsafe condition. As discussed in
other responses to commenter requests, no proposed terminating action
eliminates all the contributing factors to the unsafe condition. The
inspection or replacement programs will manage the issue to an
acceptable level of risk.
We did not change this final rule AD action based on these
comments.
Request To Change Inspection Intervals
Eric Paul, Ivan R. Wilson, Patrick D. Donovan, Patric Barry, Carl
Schoolcraft, Phil Ciholas, Dave Fitzgerald for the ICS, Andrew Detsch,
John F. Murray, and Allan H. Bieck requested an increased repetitive
interval from 100 hours to 200 hours, 500 hours, 1,000 hours, or 2,000
hours.
Patrick D. Donovan, Patric Barry, and Dave Fitzgerald for the ICS
noted that taking half of the average discovery time (stated as 4,000
hours TIS) should be a reasonable approach to establish a repetitive
interval. Ivan R. Wilson and Jim Ritter also referenced the long
service history of the fleet (approximately 50 years and several
thousand hours). Andrew Detsch asserted that the cracks occurred later
in the service life or did not grow. Arthur John Beyer provided
information that they inspected the component twice near 4,000 TIS at
an interval of 4 years and 264 hours with no cracking observed at
either inspection. Han Neubert recommended establishing intervals based
on a study of 2014-T6 behavior under stress corrosion to define stress
and environment thresholds similar to a provided report about stress
corrosion susceptibility, Time Exposure Studies on Stress Corrosion
Cracking of Aluminum 2014-T6, 2219-T87, 2014-T651, 7075-T651, and
Titanium 6Al-4V, dated June 1, 1973 (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730009798_1973009798.pdf). Charles Parker, Arthur
John Beyer, and Jim Ritter requested justification for the current
intervals.
We partially agree with adjusting the repetitive interval from 3
years to 5 years because it would align with the rationale for the
existing 10-year or 1,000-hour interval and other guidance used to
establish the intervals. There is no need to decrease the interval to
200 hours as the AD provides an interval of 500 hours.
We disagree with increasing the repetitive interval beyond 500
hours for several reasons. We must consider many factors to define an
appropriate inspection interval.
The first factor, the design safety requirement, does not allow
strength degradation below design ultimate value or stiffness
degradation for flutter. Advisory Circular (AC) 23-13A, Fatigue, Fail-
Safe, and Damage Tolerance Evaluation of Metallic Structure for Normal,
Utility, Acrobatic, and Commuter Category Airplanes, dated September
29, 2005, (http://rgl.faa.gov/Regulatory--and--Guidance--Library/
rgAdvisoryCircular.nsf/list/AC%2023-13A/$FILE/ac23-13A.pdf) describes
how ensuring no detectable cracks within the operational life of the
aircraft through an appropriate inspection interval meets the design
requirement. The existing findings of cracks do not meet these
requirements. Simply, the aircraft is not certificated to meet
airworthiness standards with a known crack.
A ``detectable'' size for a crack is a value established for the
specific inspection method in a specific application. The discovered
cracks had far exceeded detectable size before they were found during
the targeted inspections. This is due in part to no targeted
inspections until discovery of corrosion issues on the attached torque
tube several years ago. Following the approach in AC 23-13A, the
estimated service history would provide a test life of approximately
4,000 hours, then apply a scatter factor of approximately 4, yielding
1,000 hours. Again, this should be for detectable cracks that do not
degrade the strength and stiffness. An additional factor of 2
(providing two inspection opportunities) could be applied to cover that
portion, yielding an inspection at 500 hours. Note, this is only an
example to show the reasonableness of the proposed interval based on
service data. The interval is driven primarily by calendar time using a
similar approach.
The second factor is the probabilistic nature of cracking. While
some high-time or aged aircraft do not exhibit cracking, we expect this
in the distribution and is insufficient rationale to shorten the
interval. For example, the data point of a 4-year/264-hour interval is
useful, but many more data points would be necessary to support an
increased interval.
The third factor is associated with service history and the
existing intervals for related issues on the stabilator control system.
For the attached torque tube, Piper Aircraft, Inc. Service Bulletin No.
1160, dated December 26, 2005, specifies a 10-year repetitive
inspection for corrosion. Also for the tube, Special Airworthiness
Information Bulletin CE-04-88, dated September 15, 2004, (http://
rgl.faa.gov/Regulatory--and--Guidance--Library/rgSAIB.nsf/0/
77fc29bb15c8a85b8625721f0052ecb4/$FILE/CE-04-88.pdf) specifies a 3-year
or 500-hour repetitive inspection, and AD 74-13-03 (41 FR 17371, April
26, 1976) requires a 3-year or 500-hour repetitive inspection. These
issues are
[[Page 56997]]
corrosion-related and corrosion is a factor in the SCC of the horn.
The assertion that cracks occurred later or early in service and
then did not grow has no supporting data to use in establishing
intervals.
The FAA reviewed the report provided by Hans Neubert, Time Exposure
Studies on Stress Corrosion Cracking of Aluminum 2014-T6, 2219-T87,
2014-T651, 7075-T651, and Titanium 6Al-4V, dated June 1, 1973, (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730009798_1973009798.pdf). While additional work could be coordinated if funding
is available, we must first manage the known condition. The report
already alludes to the fact that aluminum 2014-T6 is particularly
susceptible to SCC which invalidates the assumption that aluminum 2014-
T6 would have equivalent behavior to other test material. There is no
true stress corrosion threshold (similar to a fatigue endurance limit)
for aluminum 2014-T6. Additional work would be required to validate the
stresses from all contributing factors once any type of threshold was
tested.
We changed the repetitive interval for inspected parts in paragraph
(g)(1) of the AD from 3 years to 5 years.
Request To Reconsider the Requirement for Repetitive Inspection of the
Assembly
Kristin Amelia Winter, Steven Fischer, George Edward White, Patric
Barry, Carl Schoolcraft, Dave Fitzgerald for the ICS, Andrew Detsch,
Arthur John Beyer, Jim Ritter, and John F. Murray requested we
reconsider the requirement for repetitive, intrusive inspection of the
assembly. The commenters were concerned that repetitive disassembly and
re-assembly of the structure could introduce new risks from wear,
assembly errors, etc.
We disagree with the commenters. While we agree that there are
potential risks with the repeated inspection, the current issue is a
higher risk and we must address the known unsafe condition. The need
for a repetitive inspection has been addressed elsewhere in this final
rule AD action. Installation of the new parts would minimize the stated
risk of repeated disassembly and reassembly and achieve the maximum
interval of 10 years or 1,000 hours.
We did not change this final rule AD action based on these
comments.
Request To Allow Alternative Inspection Methods
George Edward White, Patrick D. Donovan, Patric Barry, Phil
Ciholas, and Dave Fitzgerald for the ICS requested allowance for
alternative, less intrusive, inspection methods such as X-ray, magnetic
particle inspection, or bolt torque and measured torque tube
deformation. The commenters reasoned that the alternative inspection
methods could avoid disassembly and reassembly.
We do not agree with this request because:
X-ray does not provide a sufficiently high probability
(reliability) of detection for cracks at sizes needed to control the
unsafe condition.
Magnetic particle inspection is for magnetic materials and
would not be appropriate for the aluminum horn.
While the bolt torque value or torque tube deformation
could be a partial indicator, it is not a full measure of all the
contributing factors. The viability of such a method would also be
affected by manufacturing variability (machining, drawing tolerances,
and so forth) making it difficult to build an appropriate model to
ensure an adequate inspection method.
We did not change this final rule AD action based on these
comments.
Request To Clarify What the AD Requires
Dave Fitzgerald for the ICS requested we clarify the statement in
the summary of the NPRM (76 FR 36395, June 22, 2011) of what parts are
being replaced.
We agree with the commenter that it is important to clearly state
what parts are required in the AD action.
We changed the summary of the final rule to require replacement of
the stabilator horn assembly and/or repetitive inspection of the
stabilator horn assembly, as applicable.
Request To Allow Re-Use of Inspected Horns
Ivan R. Wilson, Patrick D. Donovan, Carl Schoolcraft, Andrew
Detsch, and John F. Murray requested a change in compliance time to
allow inspected parts to have the same inspection interval as new
replacement parts. Carl Schoolcraft also requested the option of
installing serviceable parts in lieu of new parts.
We agree with allowing used parts as replacement parts provided
they have been inspected before installation and found free of cracks
(serviceable) and they continue the repetitive inspection option in
this AD. However, we disagree with allowing the same interval on used
inspected replacement parts as on new replacement parts because a
single penetrant inspection method does not provide the same confidence
level for a crack-free part as a new part does. Such an inspection
could not reliably detect sufficiently small cracks; therefore, an
approach similar to damage tolerance requiring multiple inspections is
warranted.
We added language to:
Clarify compliance and procedures for the replacement of
the stabilator horn assembly with a serviceable stabilator horn
assembly, provided it is inspected before installation and found free
of cracks or corrosion and continues with the repetitive inspections
required for a used part; and
Clarify the initial inspection for owner/operators who may
have already installed a used serviceable stabilator horn assembly on
their airplane.
Request To Validate and/or Revise the Cost Estimate
Randy Black and Arthur John Beyer requested we validate and/or
revise the cost estimate. One commenter ordered parts including a new
horn, new torque tube, new bearings, and new hardware estimated at
$1,500 for only the parts cost. Another commenter noted the cost on
U.S. operators does not include subsequent inspections.
We do not agree with this request because the parts cost only
includes those parts required by the AD actions (the horn assembly).
Optional parts, such as the tube, are not mandated and not required in
the associated cost. Repetitive inspections are not included in AD cost
estimates as it cannot be determined which option an owner/operator may
choose, or the number of times the action(s) may be executed on an
individual aircraft.
We did not change this final rule AD action based on these
comments.
Request To Have Manufacturer Show Ability To Meet Parts Demand
Commenters Bob Rosansky, Patrick D. Donovan, Patric Barry, John
Trudel, and Phil Ciholas are associated with this request. Some
commenters requested that the airplane manufacturer demonstrate the
ability to meet the parts demand before the AD is issued. One commenter
requested time to create a parts supply for the replacement horn from
the Australian CASA STC SVA 532. Several commenters estimated that it
might require one year or more for the manufacturer to provide the
required parts and are concerned that the manufacturer's parts ordering
system will be unable to meet the demand. The request for the CASA-
approved horn is to alleviate the AD actions.
We do not agree because the manufacturer has told the FAA they can
support the parts requirements for this AD. This AD is necessary to
address an
[[Page 56998]]
unsafe condition. If parts availability becomes a problem, the FAA will
consider AMOC requests and determine whether they provide an acceptable
level of safety when they are submitted following the procedures in 14
CFR 39.19 and this AD. The AD initial compliance time should provide
sufficient time to create a parts supply.
The AD is not addressing the CASA-approved horn since the horn is
not FAA-approved at this time.
We did not change this final rule AD action based on these
comments.
Request To Change Compliance Time Because Quality Issues Might Occur
Patrick D. Donovan, Patric Barry, and John Trudel requested changes
to the compliance time based on possible quality issues in
manufacturing or delivering required parts. The commenters referenced
instances where the manufacturer supplied parts that did not meet/
specifications or delivered the wrong part numbers.
We do not agree because if non-conforming parts or the wrong parts
are distributed by the manufacturer, then the problem will be addressed
through the current regulations, including potential AD action. The FAA
cannot address this problem unless it occurs and is appropriately
reported.
We did not change this final rule AD action based on these
comments.
Request To Have Manufacturer Provide Parts Kit
Randy Black suggested the manufacturer combine the replacement horn
into a kit with the torque tube and noted that a combined kit would
provide a convenience to owners/operators.
We disagree because the additional parts beyond the horn assembly
are not required by this AD because they are not necessary to address
the unsafe condition.
We did not change this final rule AD action based on these
comments.
Request To Have FAA Directly Notify Owners/Operators of the NPRM (76 FR
36395, June 22, 2011)
Dennis Boykin stated the FAA failed to send the NPRM (76 FR 36395,
June 22, 2011) to him. The commenter stated he was not notified of the
NPRM by the FAA, but by the type club. We conclude that the commenter
requested direct notification of the NPRM.
We disagree with the request. The FAA does not mail NPRMs.
Effective March 1, 2010, the FAA stopped mailing paper copies of ADs.
We have continued to fax and/or use the US Postal Service to mail
Emergency ADs. To continue receiving ADs at no cost, please subscribe
to our GovDelivery email service by visiting the Regulatory and
Guidance Library home page (http://rgl.faa.gov). For those desiring
paper copies, we will continue to provide the AD Biweekly, which is a
paid subscription of all ADs issued in the Federal Register over the
previous 2-week period. The AD Biweekly is printed and mailed by the
Government Printing Office (GPO). Contact the GPO directly at phone:
(202) 512-1806 to subscribe.
We did not change this final rule AD action based on these
comments.
Request To Include Reporting Requirement and Analysis of Data To Refine
AD
Kristin Amelia Winter, George Edward White, Patrick D. Donovan,
Arthur John Beyer, Hans Neubert for the ICS, and Dennis Boykin
requested adding a reporting requirement with subsequent use of the
data to evaluate (or eliminate) the inspection intervals and to
evaluate potential terminating actions. Two of the commenters requested
the reporting be provided to both the FAA and ICS. One commenter also
requested a provision for rescinding the AD or extending the inspection
intervals based on the number of non-findings, especially if a new part
is installed. Finally, one commenter proposed to exclude the Model PA-
24-260 and evaluate it at a later date.
The commenters noted that the initial inspection cycle would
provide three years of time to collect and evaluate the data which
would allow the FAA and interested parties an opportunity to formulate
a more narrowly targeted AD that would better balance the cost with the
hoped for improvement in airworthiness and hence safety. Lastly, it
would provide the data necessary to design and obtain approval of an
AMOC or STC that effectively addresses this unsafe condition and
terminates any final recurring AD.
We disagree with adding a reporting requirement. Based on the
Paperwork Reduction Act, a reporting requirement must meet the
following conditions:
Help develop a corrective action;
Determine the scope of the problem and how adequate the
Design Approval Holder's corrective actions are; and
Avoid unsafe consequences if we do not collect the
information.
To eliminate the repetitive inspections and develop a terminating
action depends on a combination of factors. The following three factors
would require a re-design to eliminate the repetitive inspections:
Balance arm interference fit, basic material properties, and use of a
thicker torque tube previously discussed. Lowering the installation
torque value was addressed earlier. Reduction of corrosion potential is
currently addressed via repetitive inspections as discussed below. As
all major contributing factors are not eliminated, reporting would not
provide sufficient information to eliminate the inspections or directly
provide terminating action.
Any individual or group is free to work independently to coordinate
data collection supporting a potential concept as an AMOC or design
change (STC).
We also disagree with evaluating the Model PA-24-260 airplane only
in the future because that model meets the regulatory requirement where
the unsafe condition is likely to exist or develop in other products of
the same type design.
We did not change this final rule AD action based on these
comments.
Request To Have FAA Determine Status of Type Certificate Holder
Patric Barry and John Trudel expressed concern that the
manufacturer 's engineering/design work on the corrective action and
parts supply issues are evidence of abandonment of the responsibilities
of a type certificate holder. We conclude the commenters requested the
FAA determine the status of the type certificate holder.
We disagree with this request. The manufacturer met its obligation
as a type certificate holder by working with the FAA and industry to
generate a corrective action program addressing the unsafe condition.
Based on these comments, we made no change to the AD action.
Request To Require Inspection of the Torque Tube Assembly/Control Horn
Hans Neubert for the ICS commented that the reason that the torque
tube assembly/control horn has not been previously inspected for cracks
is due to the fact there is no prior manufacturer requirement to
inspect. We infer the commenter requested the FAA require inspection of
the torque tube assembly/control horn.
We agree with the commenter. There was not a known need for
inspection of the assembly. With discovery of the unsafe condition, a
program is now being put into place.
Based on these comments, we made no change to the AD action.
[[Page 56999]]
Request To Make Piper Aircraft, Inc. Service Bulletin No. 1189, dated
April 29, 2010, Only Advisory for the AD
Hans Neubert for the ICS recommended that this service information
be considered as advisory only to the corrective action. The commenter
stated that the preliminary and final versions of the service
information were based on an industry magazine article and were without
substantiating data, field service history, or engineering evaluation.
We disagree because the FAA independently evaluated all available
data. We incorporated the intent of this service information into the
AD, with the exception of adjustments to the applicability and
compliance time.
We did not change this final rule AD action based on these
comments.
Request To Incorporate Corrosion Preventive Measures in the AD
George Edward White recommended incorporation of corrosion
preventive measures into the AD. The commenter noted known corrosion
issues on the adjacent torque tube.
We disagree because corrosion preventive measures are already
covered by the following documents and are not necessary to address the
unsafe condition identified in this AD:
Piper Aircraft, Inc. Service Bulletin No. 1160, dated
December 26, 2005, at http://www.piper.com/Company/Publications/SB%201160%20Stab%20Torque%20Tube%20Assy%20Insp.pdf;
Special Airworthiness Information Bulletin CE-04-88, dated
September 15, 2004, at http://rgl.faa.gov/Regulatory--and--Guidance--
Library/rgSAIB.nsf/0/77fc29bb15c8a85b8625721f0052ecb4/$FILE/CE-04-
88.pdf;
AD 74-13-03, Amendment 39-2588 (41 FR 17371, April 26,
1976), at http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/5CBFDEAB5E2AC41586256E1200498F02?OpenDocument&Highlight=74-13-03;
AC 43.13-1B, Acceptable Methods, Techniques, and
Practices--Aircraft Inspection and Repair, at http://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.information/documentID/99861; and
AC 43-4A, Corrosion Control for Aircraft, at http://
rgl.faa.gov/Regulatory--and--Guidance--Library/rgAdvisoryCircular.nsf/
list/AC%2043-4A/$FILE/AC%2043-4a%20.pdf.
Based on these comments, we made no change to the AD action.
Request To Require Inspection of the Tail of the Aircraft
Patric Barry stated that periodically opening up the tail of the
aircraft for inspection may be beneficial, suggesting that routine
servicing of the entire area should be included in this AD. Dave
Fitzgerald for the ICS stated that opening up the tail area for service
of the trim drum, torque tube bearings, and associated areas is
beneficial as part of normal maintenance, but is not part of this AD
since the AD addresses the horn and torque tube and not associated
components.
We agree that maintenance of the trim drum, torque tube bearings,
and associated areas is important but disagree with including it in
this AD action. These components are not directly related to the unsafe
condition so are not part of this AD.
We did not change this final rule AD action based on these
comments.
Conclusion
We reviewed the relevant data, considered the comments received,
and determined that air safety and the public interest require adopting
the AD with the changes described previously and minor editorial
changes. We have determined that these changes:
[Agr]re consistent with the intent that was proposed in
the NPRM (76 FR 36395, June 22, 2011) for correcting the unsafe
condition; and
Do not add any additional burden upon the public than was
already proposed in the NPRM (76 FR 36395, June 22, 2011)
We also determined that these changes will not increase the
economic burden on any operator or increase the scope of the AD.
Costs of Compliance
We estimate that this AD affects 3,100 airplanes of U.S registry.
We estimate the following costs to comply with this AD:
Estimated Costs
----------------------------------------------------------------------------------------------------------------
Cost per Cost on U.S.
Action Labor cost Parts cost product operators
----------------------------------------------------------------------------------------------------------------
Stabilator horn assembly 12 work-hours x $85 Not applicable...... $1,020 $3,162,000
inspection. per hour = $1,020
----------------------------------------------------------------------------------------------------------------
We estimate the following costs to do any necessary replacements
that would be required based on the results of the proposed inspection.
We have no way of determining the number of airplanes that might need
this replacement:
On-condition Costs
----------------------------------------------------------------------------------------------------------------
Cost per
Action Labor cost Parts cost product
----------------------------------------------------------------------------------------------------------------
Stabilator horn assembly replacement......... 12 work-hours x $85 per hour = $572 $1,592
$1,020.
----------------------------------------------------------------------------------------------------------------
According to the manufacturer, some of the costs of this AD may be
covered under warranty, thereby reducing the cost impact on affected
individuals. We do not control warranty coverage for affected
individuals. As a result, we have included all costs in our cost
estimate.
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.
We are 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
[[Page 57000]]
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
This AD will not have federalism implications under Executive Order
13132. This AD will 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 that this AD:
(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),
(3) Will not affect intrastate aviation in, and
(4) 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.
Adoption of the Amendment
Accordingly, under the authority delegated to me by the
Administrator, the FAA amends 14 CFR part 39 as follows:
PART 39--AIRWORTHINESS DIRECTIVES
0
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]
0
2. The FAA amends Sec. 39.13 by adding the following new airworthiness
directive (AD):
2012-17-06 Piper Aircraft, Inc.: Amendment 39-17169; Docket No. FAA-
2011-0639; Directorate Identifier 2011-CE-016-AD.
(a) Effective Date
This AD is effective October 22, 2012.
(b) Affected ADs
None.
(c) Applicability
This AD applies to the following Piper Aircraft, Inc. airplanes,
certificated in any category:
(1) Model PA-24, serial numbers (S/Ns) 24-1 through 24-3687,
with horn part number (P/N) 20397-00 (assembly P/N 20399) installed;
(2) Model PA-24-250, S/Ns 24-1 and 24-103 through 24-3687, with
horn P/N 20397-00 (assembly P/N 20399) installed; and
(3) Model PA-24-260, S/Ns 24-3642 and 24-4000 through 24-5034,
with horn P/N 20397-00 (assembly P/N 20399) installed.
(d) Subject
Joint Aircraft System Component (JASC)/Air Transport Association
(ATA) of America Code 27: Flight Controls.
(e) Unsafe Condition
This AD was prompted by reports of cracks developing in the
stabilator horn assembly. We are issuing this AD to detect and
correct corrosion or cracks in the stabilator horn assembly.
Corrosion or cracks could lead to failure of the stabilator horn.
Consequently, failure of the stabilator horn could lead to a loss of
pitch control in flight.
(f) Compliance
Comply with this AD following Piper Aircraft, Inc. Service
Bulletin No. 1189, dated April 29, 2010, within the compliance times
specified in this AD, unless already done (does not eliminate the
repetitive actions of this AD).
(g) Inspection/Replacement
(1) When a new stabilator horn assembly has been installed
(during production or replacement) and the stabilator horn assembly
reaches a total of 1,000 hours time-in-service (TIS) or 10 years
after installation, or within the next 100 hours TIS after October
22, 2012 (the effective date of this AD), whichever occurs later, do
one of the following actions:
(i) Initially inspect the stabilator horn assembly for corrosion
or cracks. Repetitively thereafter inspect at intervals not to
exceed 500 hours TIS or 5 years, whichever occurs first.
(ii) Replace the stabilator horn assembly with a new stabilator
horn assembly. When the new stabilator horn assembly reaches a total
of 1,000 hours TIS after replacement or within 10 years after
replacement, whichever occurs first, you must do one of the actions
in paragraph (g)(1) of this AD.
(iii) Replace the stabilator horn assembly with a used
serviceable stabilator horn assembly that has been inspected before
installation and found free of cracks or corrosion. Repetitively
thereafter inspect at intervals not to exceed 500 hours TIS or 5
years, whichever occurs first.
(2) When a used serviceable stabilator horn assembly that has
been inspected before installation and found free of cracks or
corrosion has been installed and the stabilator horn assembly
reaches a total of 500 hours TIS or 5 years after installation, or
within the next 100 hours TIS after October 22, 2012 (the effective
date of this AD), whichever occurs later, do one of the following
actions:
(i) Initially inspect the stabilator horn assembly for corrosion
or cracks. Repetitively thereafter inspect at intervals not to
exceed 500 hours TIS or 5 years, whichever occurs first.
(ii) Replace the stabilator horn assembly with a new stabilator
horn assembly. When the new stabilator horn assembly reaches a total
of 1,000 hours TIS after replacement or within 10 years after
replacement, whichever occurs first, you must do one of the actions
in paragraph (g)(1) of this AD.
(iii) Replace the stabilator horn assembly with a used
serviceable stabilator horn assembly that has been inspected before
installation and found free of cracks or corrosion. Repetitively
thereafter inspect at intervals not to exceed 500 hours TIS or 5
years, whichever occurs first.
(3) If you do not know the total hours TIS on the stabilator
horn assembly, within the next 100 hours TIS after October 22, 2012
(the effective date of this AD) do one of the actions required in
paragraph (g)(1)(i), (g)(1)(ii), (g)(1)(iii), (g)(2)(i), (g)(2)(ii),
or (g)(2)(iii) of this AD.
(4) If any corrosion or cracks are found during any of the
inspections required in paragraph (g)(1)(i), (g)(1)(iii), (g)(2)(i),
or (g)(2)(iii) of this AD, before further flight, you must replace
the stabilator horn assembly as specified in paragraph (g)(1)(ii),
(g)(1)(iii). (g)(2)(ii), or (g)(2)(iii) of this AD, as applicable.
(5) For the bolts common to the torque tube and stabilator horn,
install the nuts using a torque of 120-145 in.-lbs. for the actions
required by paragraphs (g)(1), (g)(2), or (g)(3) of this AD.
Note 1 to paragraph (g) of this AD: The stated torque value of
120-145 in.-lbs. includes friction drag from the nut's locking
element, which is assumed to be 60 in.-lbs. The installation torque
can be adjusted according to the actual, measured friction drag. For
example, if the friction-drag torque is measured to be 40 in.-lbs.
(20 in.-lbs. less than the assumed value of 60 in.-lbs.), then the
installation torque will be adjusted to be 100-125 in.-lbs. of
torque.
(6) You may at any time replace the stabilator horn assembly
with a new stabilator horn assembly, provided no corrosion or cracks
were found during an inspection that would require replacement
before further flight. When the new stabilator horn assembly reaches
a total of 1,000 hours TIS after replacement or within 10 years
after replacement, whichever occurs first, you must do one of the
actions in paragraph (g)(1) of this AD.
Note 2 to paragraph (g) of this AD: Piper Aircraft, Inc. Service
Bulletin No. 1160, dated December 26, 2005; Special Airworthiness
Information Bulletin CE-04-88, dated September 15, 2004, at http://
rgl.faa.gov/Regulatory--and--Guidance--Library/rgSAIB.nsf/0/
77fc29bb15c8a85b8625721f0052ecb4/$FILE/CE-04-88.pdf; and AD 74-13-
03, Amendment 39-2588 (41 FR 17371, April 26, 1976), are related to
this AD action. For the attached torque tube, you may consider
combining that inspection with the requirements of this AD.
(h) Alternative Methods of Compliance (AMOCs)
(1) The Manager, Atlanta Aircraft Certification Office (ACO),
FAA, has the
[[Page 57001]]
authority to approve AMOCs for this AD, if requested using the
procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19,
send your request to your principal inspector or local Flight
Standards District Office, as appropriate. If sending information
directly to the manager of the ACO, send it to the attention of the
person identified in the Related Information section of this AD.
(2) Before using any approved AMOC, notify your appropriate
principal inspector, or lacking a principal inspector, the manager
of the local flight standards district office/certificate holding
district office.
(i) Related Information
For more information about this AD, contact Gregory K. Noles,
Aerospace Engineer, FAA, Atlanta ACO, 1701 Columbia Avenue, College
Park, Georgia 30337; phone: (404) 474-5551; fax: (404) 474-5606;
email: [email protected].
(j) Material Incorporated by Reference
(1) The Director of the Federal Register approved the
incorporation by reference (IBR) of the service information listed
in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.
(2) You must use this service information as applicable to do
the actions required by this AD, unless the AD specifies otherwise.
(i) Piper Aircraft, Inc. Service Bulletin No. 1189, dated April
29, 2010.
(ii) Reserved.
(3) For Piper Aircraft, Inc. service information identified in
this AD, contact Piper Aircraft, Inc., 2926 Piper Drive, Vero Beach,
Florida 32960; telephone: (772) 567-4361; fax: (772) 978-6573;
Internet: http://www.piper.com/company/publications.asp.
(4) You may view this service information at the FAA, Small
Airplane Directorate, 901 Locust St., Kansas City, Missouri 64106.
For information on the availability of this material at the FAA,
call (816) 329-4148.
(5) You may view this service information that is incorporated
by reference at the National Archives and Records Administration
(NARA). For information on the availability of this material at
NARA, call (202) 741-6030, or go to: http://www.archives.gov/federal-register/cfr/ibr-locations.html.
Issued in Kansas City, Missouri, on August 20, 2012.
John Colomy,
Acting Manager, Small Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 2012-22529 Filed 9-14-12; 8:45 am]
BILLING CODE 4910-13-P