DEPARTMENT OF TRANSPORTATION
FEDERAL AVIATION ADMINISTRATION
14 CFR Part 39
[Docket No. FAA-2007-27862; Directorate Identifier 2007-CE-036-AD] RIN
2120-AA64
AIRWORTHINESS DIRECTIVES; Thrush Aircraft, Inc. (Type Certificate Prev-
iously Held by Quality Aerospace, Inc. and Ayres Corporation) Model
600 S2D and S2R (S-2R) Series Airplanes
AGENCY: Federal Aviation Administration (FAA), Department of Transportat-
ion (DOT).
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: We propose to supersede Airworthiness Directive (AD) 2006-07-15,
which applies to Thrush Aircraft, Inc. Model 600 S2D and S2R (S-2R) series
airplanes (type certificate previously held by Quality Aerospace, Inc. and
Ayres Corporation). AD 2006-07-15 currently requires repetitive
inspections of the \1/4\-inch and \5/16\-inch bolt hole areas on the wing
front lower spar caps for fatigue cracking; replacement or repair any wing
front lower spar cap where fatigue cracks are found; and reporting of any
fatigue cracks found to the FAA. AD 2006-07-15 also puts the affected
airplanes into groups for compliance time and applicability purposes.
Since we issued AD 2006-07-15, FAA analysis reveals that inspections are
not detecting all existing cracks and shows the incidences of undetected
cracks will increase as the airplanes age. Consequently, this proposed AD
would retain the actions of AD 2006-07-15 and impose a life limit on the
wing front lower spar caps that requires replacement of the wing front
lower spar caps when the life limit is reached. This proposed AD would
also change the requirements and applicability of the groups discussed
above and remove the ultrasonic inspection method. We are proposing this
AD to prevent wing front lower spar cap failure caused by undetected
fatigue cracks. Such failure could result in loss of a wing in flight.
DATES: We must receive comments on this proposed AD by July 6, 2009.
ADDRESSES: Use one of the following addresses to comment on this proposed
AD:
Federal eRulemaking Portal: Go to http://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 proposed AD, contact Thrush
Aircraft, Inc., 300 Old Pretoria Road, P.O. Box 3149, Albany, Georgia
31706-3149. The service information is also available on the Internet at
www.thrushaircraft.com.
For Further Information, Contact One of the Following:
--Cindy Lorenzen, Aerospace Engineer, ACE-115A, Atlanta Aircraft Certific-
ation Office, One Crown Center, 1895 Phoenix Blvd., Suite 450, Atlanta,
Georgia 30349; telephone: (770) 703-6078; facsimile: (770) 703-6097;
e-mail: cindy.lorenzen@faa.gov; or
--Keith Noles, Aerospace Engineer, ACE-117A, Atlanta Aircraft Certific-
ation Office, One Crown Center, 1895 Phoenix Blvd., Suite 450, Atlanta,
Georgia 30349; telephone: (770) 703-6085; facsimile: (770) 703-6097;
e-mail: gregory.noles@faa.gov.
SUPPLEMENTARY INFORMATION:
COMMENTS INVITED
We invite you to send any written relevant data, views, or arguments
regarding this proposed AD. Send your comments to an address listed under
the ADDRESSES section. Include the docket number, "FAA-2007-27862;
Directorate Identifier 2007-CE-036-AD" at the beginning of your comments.
We specifically invite comments on the overall regulatory, economic,
environmental, and energy aspects of the proposed AD. We will consider all
comments received by the closing date and may amend the proposed AD in
light of those comments.
We will post all comments we receive, without change, to http://
www.regulations.gov, including any personal information you provide. We
will also post a report summarizing each substantive verbal contact we
receive concerning this proposed AD.
DISCUSSION
HISTORY OF AD ACTIONS
An accident in which the wing on a Thrush S2R series airplane separated
from the airplane in flight prompted us to issue AD 97-13-11. The
following presents the sequential AD history on this subject to date:
AD 97-13-11, Amendment 39-10071 (62 FR 36978, July 10, 1997), required
(until superseded by AD 97-17-03) inspecting certain areas of the wing
front lower spar caps for fatigue cracks, replacing any wing front lower
spar cap where fatigue cracks were found, and reporting any fatigue cracks
to the FAA.
AD 97-17-03, Amendment 39-10195 (62 FR 43926, August 18, 1997), superseded
AD 97-13-11. AD 97-17-03 corrected a model designation and retained the
actions of AD 97-13-11.
AD 2000-11-16, Amendment 39-11764 (65 FR 36055, June 7, 2000), superseded
AD 97-17-03. AD 2000-11-16 changed the inspections required in AD 97-17-03
to repetitive, added airplanes to the Applicability section, changed the
initial compliance time for all airplanes, and arranged the affected
airplanes into six groups based on usage and configuration.
AD 2003-07-01, Amendment 39-13097 (68 FR 15653, April 1, 2003), superseded
AD 2000-11-16. AD 2003-07-01 added airplanes manufactured with a similar
design to the Applicability section and added an additional repair option.
AD 2006-07-15, Amendment 39-14542 (71 FR 16691, April 4, 2006), superseded
AD 2003-07-01. AD 2006-07-15 increased the inspection frequency of Groups
1, 2, 3, and 6 airplanes and lowered the initial inspection time of Group
2 airplanes based on analysis of crack report data compiled from the
previous ADs.
EVENTS THAT INITIATED THIS PROPOSED AD
All of the ADs listed above required submitting reports to the FAA anytime
a fatigue crack was found on a wing front lower spar cap. Recent analysis
of the data from those reports and other historical and statistical data
indicate the current inspections are not completely addressing the unsafe
condition.
Specifically, the data indicate a risk that some airplanes in the Thrush
fleet may currently have undetected fatigue cracks in the steel spar cap
using the existing inspection program. Airplanes with cracks in the wing
front lower spar caps are unable to meet ultimate strength requirements,
which could lead to a wing failure. As the incidences of cracking
increase, which has occurred in the Thrush airplanes, the chance of an
existing crack not being detected during an inspection increases.
FAA ANALYSIS
The FAA used a risk-based probability analysis to determine the risk of
fatigue cracks occurring in the wing front lower spar cap on Model 600 S2D
and S2R (S-2R) series airplanes. This analysis indicates the risk to the
pilot and the public is too great to allow the continuation of the
repetitive inspections as the only method to ensure the safety of these
airplanes. The actions in this proposed AD are necessary to assure the
continued airworthiness of these airplanes.
We analyzed data obtained from reports of 117 fatigue cracks found on the
wing front lower spar caps on these airplanes since 1997. The analysis of
the crack reports led to our determination to consider imposing a life
limit on the wing front lower spar caps. We have confidence in the
accuracy of the reports submitted by the owner/ operators, Airframe and
Powerplant (A&P) mechanics, and Level 2 and 3 non-destructive inspectors.
Anyone with documented evidence of owner/ operators, inspectors, or A&P
mechanics on behalf of the owner submitting inaccurate crack reports or
not submitting crack reports to the FAA should send that evidence to their
local FAA Flight Standards District Office.
We have a documented occurrence of a fatigue crack that went undetected
for at least two inspection cycles. The crack grew until the wing front
lower spar cap was completely severed, which is considered a failure even
though the wing stayed attached to the airplane. The "big butterfly" plate
and the lower splice plate, part numbers (P/Ns) 20211-09 and 20211-11
respectively, installed on this airplane as an optional modification
helped keep the wing together; however, the plates are not designed to
carry all of the possible flight loads in the event a spar cap is severed.
Installing stronger "big butterfly" plates is beneficial because it
reduces stress in the wing front lower spar caps. The reduced stress slows
the crack growth rate in the spar cap. This slower crack growth rate in
airplanes equipped with "big butterfly" plates allows for less frequent
inspections. Even though P/Ns 20211-09 and 20211-11 reduce stress in the
wing front lower spar caps and slow the crack growth rate, the plates will
not handle all possible flight loads once the spar cap is severed. Any
known cracks must still be repaired.
Thrush Aircraft, Inc. has developed Custom Kit No. CK-AG-41, Revision A,
dated March 8, 2007. This kit includes parts and procedures for replacing
both wing front lower spar caps with new wing front lower spar caps, P/Ns
20207-15 and 20207-16, new inboard spar webs and doublers, and new,
thicker "big butterfly" plate and lower splice plate, P/Ns 94418-5 and
94418-7 respectively.
Airplanes that have Custom Kit No. CK-AG-41, Revision A, installed in its
entirety will have lower stresses in the spar cap, which will delay the
initiation of fatigue cracks and slow the fatigue crack growth rate
allowing for less frequent inspections. A life limit would remain the same
even after Custom Kit No. CK-AG-41, Revision A, is installed in its
entirety. If additional fatigue testing and analysis is completed on this
configuration in the future, a life limit may be adjusted.
Our analysis showed the wing front lower spar caps will all crack due to
fatigue. In determining the maximum time allowed for life limits, we gave
consideration to the following:
Reliability of the significant amount of crack data on the Thrush fleet;
Existence of the on-going inspection program for the wing front lower spar
caps; and
Allowance of credit for time the airplanes operated with lower horsepower
radial engines and were later modified by installing a turbine engine, a
higher horsepower radial engine, or larger hopper.
We could not consider the following when determining life limits:
Individual airplanes operated at lower weights; and
Individual airplanes operated at lower G loads.
To consider these factors, individual airplanes would need to have
recorded data for every flight since the wings were installed showing the
weight and recorded Gs throughout each flight, along with fatigue analysis
and tests using this data.
In addition, we could not consider the effect of the following modificat-
ions when determining life limits:
Kaplan splice blocks installed;
"Big butterfly" plates and lower splice plates installed;
Winglets installed; or
Cold work process on the bolt holes performed.
We do not have service information to calculate the effect of these modif-
ications, and accurate fatigue test data or fatigue analysis data
supported by tests has not been provided to us for these configurations.
If we receive accurate fatigue substantiation data for airplanes with
these modifications, we may allow changes to life limits by an alternative
method of compliance.
There is evidence of sharp, uneven edges on the spar cap bolt holes that
resulted from the manufacturing process in Group 5 airplanes. Five fatigue
cracks have been reported on Group 5 airplanes, and our analysis concludes
fatigue cracks will occur on all these airplanes. Premature fatigue cracks
begin when there is a crack starter, such as an uneven edge. At this time,
there is no rework method to address the condition of these wing front
lower spar caps with uneven bolt hole edges. Once the original wing front
lower spar caps are replaced, a higher life limit for wing front lower
spar caps without uneven bolt hole edges may be used.
Initial compliance times for replacement of the wing front lower spar caps
would be based on risk analysis that allows for compliance scheduling. For
any of the affected airplanes that may exceed any life limits, the
compliance time range would be based on total hours time-in-service
(TIS), which would address those high-usage airplanes first. Graduated
compliance times would help alleviate grounding of airplanes due to the
limited supply of wing front lower spar caps, while still addressing the
increased risk for high-usage airplanes.
LONG-TERM CONTINUED OPERATIONAL SAFETY
Repeated loads and the resulting stresses in the metal lead to fatigue.
Over time, these stresses cause the metal to wear out and cracks will form
in these airplanes even when operated within the approved limitations and
envelope. Higher stresses in the wing front lower spar cap, caused by
pulling excessive Gs and/or operating over the design weight of the
airplane, will accelerate metal fatigue. Metal will also fatigue more
quickly when operated in a wet or corrosive environment, which exists when
dispensing agricultural chemicals or dropping fire retardants or water.
Any type of inspection method may be affected by the reliability of the
equipment used, the inspection procedure used, the environment in which
the inspection is done, the quality of the calibration reference standard
used, and various human factors, such as the knowledge, skill, experience,
and dexterity of the inspector. Because of all these variables, most
inspection results, while very good, are not always 100-percent accurate.
Over time, the probability of failing to detect a crack increases due to
these variables, which increases the risk to the safety of these
airplanes.
Studies of the factors leading to inspection inaccuracy and their effect
on a variety of inspection methods, including magnetic particle
inspections and eddy current inspections, have been done by the National
Aeronautics and Space Administration (since 1973 for the Space Shuttle
design), the United States Air Force, and the FAA. These studies show
variability in inspection results that are inherent to any measurement
process.
We received a report of cracks not being detected in the Thrush wing front
lower spar cap using the ultrasonic method because of the configuration of
the joint. Our records indicate that ultrasonic inspections are no longer
being used in the field. This inspection method should be removed. If
ultrasonic inspections are no longer allowed for these inspections, the
availability of inspection facilities should not be affected because the
two inspection facilities certified for ultrasonic inspections are also
certified for eddy current inspections.
As wing front lower spar caps accumulate hours TIS beyond the time when
cracks have been found on other products of the same type design, the
likelihood of fatigue cracks occurring in these wing front lower spar caps
increases. Many of the affected airplanes have wing front lower spar caps
that have been in service well past the number of hours TIS when cracks
have been appearing on wing front lower spar caps in other products of the
same type design. FAA statistical analysis of the crack data indicates the
risk of a wing failure occurring is becoming very high for these
airplanes.
RECLASSIFICATION OF AIRPLANE GROUPS
A recent review of the manufacturer's build record data shows some
airplanes were placed in incorrect Groups and one airplane was
inadvertently left out in the previous ADs. Our review shows that Model
S2R-T34 airplanes, serial numbers (S/Ns) T34-147 through T34-167, were
built with wing front lower spar caps identical to Group 2 airplanes;
these airplanes should be reclassified from Group 1 to Group 2. Model S2R
-G10 airplane, S/N G10-137, is currently included in Group 4 airplanes but
was built identical to Group 2; this airplane should be reclassified into
Group 2. We inadvertently omitted Model S2R-T34 airplane, S/N T34-170,
from AD 2006-07-15; that airplane should be included in Group 2. We
inadvertently listed Model S2R-T34 airplane, S/N T34-225, in both Group 2
and Group 4 airplanes in AD 2006-07-15; it should be in Group 2 only.
Model S2R-G1 airplane, S/Ns G1-107, G1-108, G1-109; Model S2R-G10
airplane, S/Ns G10-139 and G10-142; and Model S2R-T34 airplanes, S/Ns T34
-236, T34-237, and T34-238, were built identical to Group 5; these
airplanes should be in Group 5. No airplanes were built to the configurat-
ion previously identified as Group 4; Group 4 should be removed.
RELEVANT SERVICE INFORMATION
The following service information was included in AD 2006-07-15 and will
be included in this proposed AD:
--Ayres Corporation Service Bulletin No. SB-AG-39, dated September 17,
1996;
--Ayres Corporation Custom Kit No. CK-AG-29, dated December 23, 1997; and
--Quality Aerospace, Inc. Custom Kit No. CK-AG-30, dated December 6, 2001.
The new service information for this proposed AD is Thrush Aircraft, Inc.
Custom Kit No. CK-AG-41, Revision A, dated March 8, 2007.
FAA'S DETERMINATION AND REQUIREMENTS OF THE PROPOSED AD
We are proposing this AD because we evaluated all information and
determined the unsafe condition described previously is likely to exist or
develop on other products of the same type design. This proposed AD would
supersede AD 2006-07-15 with a new AD that would:
Retain the actions of AD 2006-07-15;
Add life limits for the wing front lower spar caps;
Lower the initial and repetitive inspection times for Group 5 airplanes;
Correct some airplane Group classifications;
Add an airplane to the Applicability section; and
Remove the use of ultrasonic inspection methods.
The initial compliance time for all airplanes would be at least an
additional 500 hours TIS after the effective date of the proposed AD for
replacement of the wing front lower spar caps. Calculated from actual
flight hour data from 285 S2R series airplanes, 500 hours TIS equates to
the average yearly operational time. The proposed compliance schedule
should give owner/operators enough time to schedule the replacement of the
wing front lower spar caps.
Although not required in this proposed AD, we recommend installing "big
butterfly" and lower splice plates, P/Ns 20211-09 and P/N 20211- 11, or
Thrush Aircraft, Inc. Custom Kit No. CK-AG-41, Revision A, since they
increase the strength of the wing beyond the minimum safety standards.
This proposed AD would require you to use the service information
described previously to perform these actions.
COSTS OF COMPLIANCE
We estimate that this proposed AD would affect 808 airplanes in the U.S.
registry, including those airplanes affected by AD 2006-07-15.
We estimate the following costs to do each proposed inspection:
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TOTAL COST PER TOTAL COST ON U.S.
LABOR COST PARTS COST AIRPLANE OPERATORS
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3 work-hours x
$80 = $240.... $525 $765 $618,120
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We estimate the following costs to do cold work of bolt holes for the
repair that may be required based on the results of the proposed
inspection. We have no way of determining the number of airplanes that may
need such repair:
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TOTAL COST PER
LABOR COST PARTS COST AIRPLANE
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1 work-hour x $80 = $80.... $100 $180
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We estimate the following costs to do any reaming of outer holes to
\5/16\-inch diameter for the repair that may be required based on the
results of the proposed inspection. We have no way of determining the
number of airplanes that may need such repair:
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TOTAL COST PER
LABOR COST PARTS COST AIRPLANE
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1 work-hour x $80 = $80..... None............. $80
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We estimate the following costs to do any drilling and reaming of outer
holes and adding three holes to install a Kaplan splice block for the
repair that may be required based on the results of the proposed
inspection. We have no way of determining the number of airplanes that may
need such modification:
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TOTAL COST PER
LABOR COST PARTS COST AIRPLANE
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65 work-hours x $80 = $5,200.. $4,400 for splice $10,200
block and $600
for hardware.
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We estimate the following costs to do the proposed optional installation
of Thrush Aircraft, Inc. Custom Kit No. CK-AG-41, Revision A, dated March
8, 2007. This kit may be used to do any necessary wing front lower spar
cap replacement that would be required based on the results of the
proposed inspection or that would be required based on reaching the
proposed life limit:
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TOTAL COST PER
LABOR COST PARTS COST AIRPLANE
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300 work-hours x
$80 = $24,000... $40,000 $64,000
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We estimate the following costs to do any necessary wing front lower spar
cap replacement that would be required based on the results of the
proposed inspection or by the wing front lower spar cap reaching the
proposed life limit:
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LABOR COST PER PARTS COST PER
WING FRONT LOWER WING FRONT LOWER TOTAL COST TOTAL COST ON U.S.
SPAR CAP SPAR CAP PER AIRPLANE OPERATORS
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200 work-hours x
$80 = $16,000... $8,000 Each spar cap replace- $38,784,000
ment = $24,000.
Two spar caps per
airplane = $48,000.
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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 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.
INITIAL REGULATORY FLEXIBILITY ANALYSIS
INTRODUCTION AND PURPOSE OF THIS ANALYSIS
The Regulatory Flexibility Act of 1980 (Pub. L. 96-354) (RFA) establishes
"as a principle of regulatory issuance that agencies shall endeavor,
consistent with the objectives of the rule and of applicable statutes, to
fit regulatory and informational requirements to the scale of the
businesses, organizations, and governmental jurisdictions subject to
regulation." To achieve this principle, the RFA requires agencies to
solicit and consider flexible regulatory proposals and to explain the
rationale for their actions to assure that such proposals are seriously
considered." The RFA covers a wide-range of small entities, including
small businesses, not-for-profit organizations, and small governmental
jurisdictions.
Unless the FAA can certify that a proposed rule will not have a
significant economic impact on a substantial number of small entities, the
FAA is required to prepare an initial regulatory flexibility analysis
(IRFA) as described in Sec. 603 of the RFA. Such an analysis must include
(1) a description of the reasons for the agency's action; (2) a statement
regarding the objectives and legal basis for the proposed rule; (3) an
estimate of the number of small entities that will be affected by the
proposed rule; (4) a description of the projected recordkeeping,
reporting, and other compliance costs; (5) a statement regarding any
potential duplication, overlap, or conflict with all other relevant rules;
and (6) a description of any significant alternatives that may minimize
the significant economic impact of the proposed rule on small entities.
Based on the following analysis, the FAA concludes that this proposed rule
will have a significant economic impact on a substantial number of small
entities.
REASONS ACTION BY THE FAA IS BEING CONSIDERED
A series of ADs, beginning in 1997 and culminating in AD 2006-07-15 in
2006, addressed the issue of fatigue cracking of the wing front lower spar
caps in Thrush Aircraft, Inc. (Thrush) Model 600 S2D and S2R (S-2R) series
airplanes (type certificate previously held by Quality Aerospace, Inc. and
Ayres Corporation). This type of fatigue cracking, if not addressed, could
result in catastrophic wing failure. The original 1997 AD was issued after
an accident on an S2R series airplane in which the wing separated from the
airplane in flight. Requirements of inspection and possible replacement
were changed in 2000 to repetitive inspections and possible replacement.
In 2006, the inspection rate was doubled after a completely severed spar
cap was found on one of the affected airplanes and the FAA noted that it
was working with Thrush to develop a future terminating action. Analysis
indicated that an undetected crack had existed during the previous two
repetitive inspections of that spar cap.
Subsequent FAA analysis has shown that spar cap fatigue cracking has
increased as the fleet has aged, and will continue to increase.
Consequently, the incidences of undetected cracks will increase,
increasing the probability of catastrophic wing failure. The FAA has
concluded that repetitive inspections, as required since the 2000 AD, are
insufficient by themselves to ensure the safety of these airplanes and,
accordingly, in this proposed AD the FAA proposes spar cap life limits to
address this safety issue.
OBJECTIVES OF, AND LEGAL BASIS FOR, THE PROPOSED RULE
The FAA is issuing this rulemaking under the authority set forth in 49
U.S.C. 44701(a)(5), which mandates the Administrator prescribe regulations
for practices, methods, and procedures 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 the
airplanes identified in this AD.
DESCRIPTION OF THE SMALL ENTITIES THAT THE PROPOSED RULE WILL APPLY AND AN
ESTIMATE OF THEIR NUMBER
This proposed rule would potentially affect 808 U.S. registered and
operated Thrush Model 600S2D and S2R (S-2R) series airplanes.\1\ In
conducting this analysis, the FAA reviewed data from the FAA Registry
(Registry) to determine how many of the affected Thrush airplanes are
registered and operated by small entities. The Registry indicates that
these 808 airplanes are owned by 546 separate entities in agricultural
aviation. Although the Registry does not record financial or business data
about the registered owners of aircraft, and such data for these entities
are not readily available elsewhere, it appears that most, if not all, of
the 546 entities are engaged in crop dusting, spraying, and seeding
operations. These activities are classified in North American Industry
Classification System (NAICS) industry, NAICS 115112--Soil Preparation,
Planting, and Cultivating (including Crop Dusting, Crop Spraying). The
concentration of these entities in a single NAICS industry reflects the
specialized nature of agricultural airplanes with restricted airworthiness
certificates. Furthermore, several of these entities were classified in
the Standard Industrial Classification (SIC) equivalent of NAICS 115112 by
http://www.manta.com. Although a few of these entities may also be engaged
in firefighting, which is classified in NAICS 115310--Support Activities
for Forestry (including Forest Fire Suppression), the FAA is unable to
identify any of these entities as being principally engaged in
firefighting. The Small Business Administration (SBA) small business
classification for NAICS 115112 is $6.5 million in business receipts, and
$16.5 million in business receipts for NAICS 115310. Only one entity in
this sample appears to have business receipts over $6.5 million, and no
entity has business receipts in excess of $16.5 million. Using the total
number of airplanes owned as a size criterion, the FAA selected a sample
of 41 of the largest affected entities, and found median sales shown by
http:// www.manta.com to be just $250,000 annually. Firms in agricultural
aviation appear to be inherently of small size. Accordingly, the FAA
estimates that 545 small entities will be affected by this proposed rule.
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\1\ FAA Registry, http://www.faa.gov/licenses_certificates/aircraft_cert-
ification/aircraft_registry/releasable_aircraft_download. Data down-
loaded on 4/14/08.
--------------------------------------------------------------------------
DESCRIPTION OF THE PROJECTED REPORTING, RECORDKEEPING, AND OTHER COMPL-
IANCE REQUIREMENTS OF THE PROPOSED AD
The proposed AD does not impose any additional reporting or recordkeeping
requirements beyond those required by the 2006 AD. The proposed rule would
retain the requirements of AD 2006-07-15 and impose a life-limit on the
wing front lower spar caps, which would require operators of affected
airplanes to replace the wing front lower spar caps when the life-limit is
reached.
The estimated compliance cost varies widely by airplane submodel; from a
cost of zero for the more than 200 older airplanes that we estimate will
retire \2\ before the life-limit on their wing front lower spar caps is
reached, to a cost of $320,000 (5 replacements at $64,000 per replacement)
for two airplanes. Individual airplane compliance costs will likely result
in costs to the small entities that own these airplanes. The exact cost
will vary, depending on the number of affected Thrush airplanes owned by
the entity and the specific compliance cost for each airplane. The
ownership table below shows the variation in the number of owners with
particular numbers of airplanes. The table shows that almost 75% of the
546 individual owners have only one affected airplane, and more than 90%
of owners have no more than two affected airplanes. The average (mean)
number of affected airplanes held is 1.48, while the median number held is
just 1.00, so the median airplane cost is equivalent to the median owner
cost.
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\2\ As fully analyzed in the "Cost of Compliance" section of this proposed
rule, the FAA estimates that the airplanes affected by this proposed
rule retire at age 40.
NUMBER OF THRUSH AD OWNERS HAVING PARTICULAR NUMBERS OF AFFECTED AIRPLANES
--------------------------------------------------------------------------
NUMBER OF AFFECTED
AIRPLANES HELD BY NUMBER OF OWNERS CUMULATIVE %
SINGLE OWNER
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1 406 74.4
2 86 90.1
3 26 94.9
4 13 97.3
5 7 98.5
6 2 98.9
7 2 99.3
8 1 99.5
9 2 99.8
13 1 100.0
--------------------------------------------------------------------------
Total.... 808 546
Mean..... 1.48
Median... 1.00
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Source: FAA Registry. Data downloaded on 4/18/08.
In the "Cost of Compliance" section of this proposed AD, the FAA estimates
total cost (undiscounted) to be $37.1 million and the present value cost
to be $25.2 million. The FAA estimates that 545 of the 546 airplanes
affected by this proposed AD are small firms, and, in fact, 98.8% of the
proposed AD's estimated cost is attributed to small entities. The
following documents and analyzes the impact of this cost on the
substantial number of small firms identified in this proposed AD.
ECONOMIC IMPACT ON SMALL ENTITIES
Because the Registry does not collect financial or business data on these
entities, and such data is not readily available elsewhere, the FAA also
used Census Bureau size distribution data to assess the economic impact on
small firms. The FAA used data from the 2002 Census since this is the
latest Census for which size distribution by business receipts is readily
available. These data are available in a special Census compilation for
the SBA.\3\ The FAA used the data for NAICS 115112--Soil Preparation,
Planting, and Cultivating (including Crop Dusting, Crop Spraying), but did
not use the data for NAICS 115310-- Support Activities for Forestry
(including Forest Fire Suppression) since, as noted above, a very high
percentage of the affected small firms, if not all, meet the
classification standard of NAICS 115112. Moreover, the size distribution
of NAICS 115310 appears to be similar to that of NAICS 115112. The
concentration of the affected airplanes in one NAICS industry, noted
above, makes the use of Census data feasible and appropriate.
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\3\ Small Business Administration, Office of Advocacy. http://www.sba.gov/
advo/research/us_rec02.txt.
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The relevant Census data are provided in the table below:
2002 CENSUS DATA FOR NAICS 115112--SOIL PREPARATION, PLANTING, AND
CULTIVATING (INCLUDING CROP DUSTING, CROP SPRAYING)--SMALL SIZE CLASSES
--------------------------------------------------------------------------
MEASURE TOTAL $0- $100,000- $500,000- $1,000,000- $5,000,000-
$99,999 $499,999 $999,0000 $4,999,999 $10,000,000
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Firms...... 2336 509 992 412 394 29
Percentage
of firms... ..... 21.8% 42.5% 17.6% 16.9% 1.2%
Upper bound
percentile. 21.8% 64.3% 81.9% 98.8% 100.0%
Est. Rec-
eipts($000).$1,531,004 $25,681 $257,447 $286,462 $772,401 $189,013
Receipts/
Firm($).... $655,396 $50,454 $259,523 $695,296 $1,960,409 $6,517,690
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Source: "Firms" and "Est. Receipts" from Small Business Administration,
Office of Advocacy. http://www.sba.gov/advo/research/us_rec02.txt.
The table shows the number of firm and business receipt data for the five
smallest size classes of NAICS 115112 that encompass the size range of the
firms affected by this proposed AD. In the "Percentage of firms" row, for
each size class, the FAA calculates that class's number of firms as a
percentage of the total number of firms in the five size classes.
Cumulating this percentage from the smallest to largest size class
establishes the "Upper bound percentile"--the cumulated percentage of
firms of business receipt size ranging up to the upper bound of the size
class.
The proposed AD's cost for the firms at the upper bound percentiles is
then estimated as the corresponding percentiles in the estimated firm
- level compliance cost data. In order to assess the economic impact of
the proposed AD, these costs are calculated as a percentage of the Census
data upper bounds. For example, the upper bound percentile for the 100-500
thousand dollar size class is 64.3%, so the NAICS 115112 firms at that
percentile are estimated to have $500,000 business receipts of $500,000.
As shown in the table below, the FAA then determined the estimated
compliance cost of firms at the same percentile in the compliance cost
data to be $61,754. The FAA assumes these firms are the same so the
percentage cost impact (Proposed AD Cost/Firm Size) is 12.4%. This
procedure assumes the size distribution of the 808 firms affected by the
proposed AD have a distribution similar to the overall distribution of the
small firms in NAICS 115112. It also assumes there is a perfect rank
correlation between the size of the affected firms and the firms'
compliance cost. While the latter assumption is certainly not the case,
any deviation from such perfect correlation can only increase the impact
of the proposed AD because smaller firms will have larger costs.
Accordingly, the FAA's determination that the proposed AD will have a
significant impact on a substantial number of small entities is
unaffected.
ECONOMIC IMPACT OF THRUSH AD ON SMALL FIRMS
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ESTIMATED FIRM
SIZE (CENSUS PROPOSED AD CUMULATIVE
PROPOSED AD FIRM PER- BUREAU RECEIPTS COST/FIRM SIZE NUMBER OF FIRMS
COST TO FIRM CENTILE UPPER BOUND) (PERCENT)
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$0......... 21.8th $100,000 0.0 119.2
$61,754.... 64.3rd 500,000 12.4 351.5
$91,335.... 81.9th 1,000,000 9.1 447.9
$273,734... 98.8th 5,000,000 5.5 540.2
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The above table shows a zero-cost impact on a firm at the 21.8th
percentile. This result reflects the estimate in the "Cost of Compliance"
section of this proposed AD that more than 200 older airplanes will retire
before their spar cap life-limits are reached. As already mentioned, the
proposed AD cost for a firm at the 64.3rd percentile is $61,754, which as
a percentage of estimated firm size (size class upper bound) is 12.4% of
annual business receipts. This impact declines to 9.1% for a firm at the
81.9th percentile and to 5.5% for a firm at the 98.8th percentile. As a
result, the overall pattern is zero impact for the smallest of the small
firms, owners of the oldest airplanes, but a highly positive impact for
the medium-sized small firms. In percentage terms, this impact falls for
the largest small firms, but remains at a substantial level. While the FAA
can make no definitive inference on the impact of the proposed AD on firms
between the 21.8th and 64.3rd percentiles, the FAA notes the cost varies
from 9.1% up to 12.4% of annual business receipts for 96 firms between the
81.9th and 64.3rd percentiles and from 5.5% to 9.1% for 92 firms between
the 98.8th percentile and the 81.9th percentile. These estimated
percentage impacts are substantial and therefore, the FAA concludes that
this proposed AD will have a significant impact on a substantial number of
small entities.
DUPLICATIVE, OVERLAPPING OR CONFLICTING FEDERAL RULES
There are no Federal rules that duplicate, overlap, or conflict with this
proposed AD.
SIGNIFICANT ALTERNATIVES TO THE PROPOSED AD
The FAA considered relying on repetitive inspections as the sole safety
method, but given that the past required repetitive inspections have not
fully addressed this critical safety issue, the FAA has determined that a
part life limit is also necessary. A life limit on the wing front lower
spar caps is the only available sufficient action presently known to the
FAA. Consequently, there are no significant viable alternatives to the
proposed AD.
REQUEST FOR COMMENTS
The FAA has determined that this proposed rulemaking will have a
significant economic impact on a substantial number of small entities. The
FAA requests comments with supporting justification regarding this
determination.
INTERNATIONAL TRADE IMPACT ANALYSIS
The Trade Agreement Act of 1979 prohibits Federal agencies from
establishing any standards or engaging in related activities that create
unnecessary obstacles to the foreign commerce of the United States. The
statute does not consider legitimate domestic objectives, such as safety,
as unnecessary. The statute also requires consideration of international
standards and, where appropriate, that they be the basis for U.S.
standards. The FAA is issuing this proposed AD because of a known safety
problem and, therefore, the proposed AD is not considered an unnecessary
obstacle to international trade.
UNFUNDED MANDATES REFORM ACT ASSESSMENT
Title II of the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4)
requires each Federal agency to prepare a written statement assessing the
effects of any Federal mandate in a proposed or final agency rule that may
result in an expenditure of $100 million or more (adjusted annually for
inflation with the base year 1995) in any one year by State, local, and
tribal governments in the aggregate, or by the private sector. The Act
deems such a mandate to be a "significant regulatory action." The FAA
currently uses an inflation-adjusted value of $136.1 million.
This proposed AD does not contain such a mandate.
REGULATORY FINDINGS
We have 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 that the proposed regulation:
1. Is not a "significant regulatory action" under Executive Order 12866;
2. Is not a "significant rule" under the DOT Regulatory Policies and Proc-
edures (44 FR 11034, February 26, 1979); and
3. Could have a significant economic impact on a substantial number of
small entities under the criteria of the Regulatory Flexibility Act.
We prepared a regulatory evaluation of the estimated costs to comply with
this proposed AD and placed it in the AD docket.
EXAMINING THE AD DOCKET
You may examine the AD docket that contains the proposed AD, the
regulatory evaluation, any comments received, and other information 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 Docket Office (telephone (800) 647-5527) is
located at the street address stated in the ADDRESSES section. Comments
will be available in the AD docket shortly after receipt.
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 removing Airworthiness Directive (AD)
2006-07-15, Amendment 39-14542 (71 FR 16691, April 4, 2006), and adding
the following new AD: