[Federal Register Volume 59, Number 35 (Tuesday, February 22, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-3840]
[[Page Unknown]]
[Federal Register: February 22, 1994]
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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39
[Docket No. 92-CE-57-AD; Amdt 39-8835; AD 94-04-15]
Airworthiness Directives: Twin Commander Aircraft Corporation
Models 500, 560A, 560E, 680, 680E, and 720 Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
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SUMMARY: This amendment adopts a new airworthiness directive (AD) that
applies to certain Twin Commander Aircraft Corporation (Twin Commander)
Models 500, 560A, 560E, 680, 680E, and 720 airplanes. This action
requires inspecting the wing front spar lower cap (spar cap) for
interference, fretting, or corrosion between the firewall flange and
spar cap flange at Wing Station (WS) 96, and clearing any interference,
repairing any fretting or corrosion damage, and replacing any cracked
spar cap. Reports of two of the affected airplanes have cracked spar
caps at WS 96 prompted this action. The actions specified by this AD
are intended to prevent failure of the wing structure caused by a
cracked spar cap at WS 96.
DATES: Effective April 12, 1994. The incorporation by reference of
certain documents listed in the regulations is approved by the Director
of the Federal Register as of April 12, 1994.
ADDRESSES: Service information that applies to this AD may be obtained
from the Twin Commander Aircraft Corporation, 19003 59th Drive, NE.,
Arlington, Washington 98223. This information may also be examined at
the Federal Aviation Administration (FAA), Central Region, Office of
the Assistant Chief Counsel, room 1558, 601 E. 12th Street, Kansas
City, Missouri 64106; or at the Office of the Federal Register, 800
North Capitol Street, NW., suite 700, Washington, DC.
FOR FURTHER INFORMATION CONTACT:
Mr. Mike Pasion, Aerospace Engineer, FAA Northwest Mountain Region,
1601 Lind Avenue SW., Renton, Washington 98055-4056; telephone (206)
277-2594; facsimile (206) 227-1181.
SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal
Aviation Regulations to include an AD that applies to certain Twin
Commander Models 500, 560A, 560E, 680, 680E, and 720 airplanes was
published in the Federal Register on June 30, 1993 (58 FR 34950). The
action proposed to require inspecting the spar cap for interference,
fretting, or corrosion between the firewall flange and spar cap flange
at WS 96, and clearing any interference, repairing any fretting or
corrosion damage, and replacing any cracked spar cap. The proposed
inspection and repair, if applicable, would be accomplished in
accordance with Twin Commander SB No. 212, dated November 3, 1992.
Interested persons have been afforded an opportunity to participate
in the making of this amendment. Due consideration has been given to
the nine comments received.
Seven commenters concur with the proposal as written.
One commenter, the Civil Aviation Authority of Australia (CAA),
states that the proposal should require an eddy current inspection of
the spar cap. The CAA questions whether fretting and corrosion are the
sole contributors to fatigue damage to WS 96, or if these merely
aggravate what is already a fatigue-sensitive location. The CAA goes on
to state that, if a crack can start from a corrosion pit as small as
0.006 inches (as happened on a Swedish airplane), then there is a good
chance that even a clean airplane will crack over time. Also, the CAA
states that, if a fatigue crack has started at the base of a corrosion
pit, the blending of the corrosion will smear over the crack and
conceal it from the dye penetrant inspection (which is called for in
the SB), and that an eddy current inspection is the only method for
detection of this crack. The FAA does not concur. The proposal relates
to fretting that may occur because interference between a firewall
stiffener and the forward flange of the lower spar cap. It would
require action for fatigue cracks found as a result of this
interference and fretting. Fretting does have a synergistic
relationship with corrosion and fatigue, and its existence greatly
accelerates fatigue crack growth. The FAA has received no reports of
fatigue cracks in the affected area that were not a direct result of
fretting. Also, the spar cap at WS 96 is extremely difficult to inspect
using eddy current methods because of other structures in the area
interfering with placement of the eddy current probe. Dye penetrant
inspections are used extensively in the aviation industry and have
proved very reliable in detecting cracks. The proposed AD is unchanged
as a result of this comment.
Another commenter, the Twin Commander Aircraft Corporation states
that owners/operators should have their airplanes inspected regardless
of whether the spar cap has been replaced because interference may even
exist on a new spar. The FAA concurs that interference may exist if a
new spar is installed, unless it was installed in accordance with
replacement procedures obtained from the manufacturer through the
Manager, Seattle Aircraft Certification Office (as specified in
paragraph (a)(3) of the proposed AD). The Seattle Aircraft
Certification Office has not issued any of these procedures to airplane
owners/operators; therefore, no airplane has the spar cap replaced in
accordance with paragraph (a)(3) of the proposal and the proposal would
affect all of the airplanes listed under the Applicability section. The
proposed AD is unchanged as a result of this comment.
After careful review of all available information including the
comments referenced above, the FAA has determined that air safety and
the public interest require the adoption of the rule as proposed except
for minor editorial corrections. The FAA has determined that these
minor corrections will not change the meaning of the AD nor add any
additional burden upon the public than was already proposed.
The FAA estimates that 332 airplanes in the U.S. registry will be
affected by the proposed AD, that it will take approximately 20
workhours per airplane to accomplish the required inspection, and that
the average labor rate is approximately $55 an hour. Parts to
accomplish the required inspection cost approximately $20. Based on
these figures, the total cost impact of the inspection specified in
this AD on U.S. operators is estimated to be $371,840. One airplane
owner has already accomplished the required inspection, and found no
damage or cracks.
In addition, if the required inspection reveals cracks, or
corrosion that exceeds certain limits, replacing the spar cap would be
required at a cost of approximately $100,000, parts and labor included.
An airplane affected by this AD could have a compliance cost as low as
approximately $1,120 (labor + parts) if no cracks, interference, or
corrosion damage is found during the inspection, and as high as
approximately $101,120 (inspection + spar cap replacement) if the
operator replaces the spar cap.
Based on these airplanes having an expected average remaining
operating life of 10 years or 15 years, the annualized compliance cost
would range between:
If only inspecting the spar cap at WS 96 is necessary for
airplanes with an average remaining operating life of 10 years:
$1,120 x 0.14349 (10-year capital recovery factor at a 7 percent
interest rate)=$168 annualized cost;
If only inspecting the spar cap at WS 96 is necessary for
airplanes with an average remaining operating life of 15 years:
$1,120 x 0.11434 (15-year capital recovery factor at a 7 percent
interest rate)=$126;
If replacing the spar cap is necessary for airplanes with
an average remaining operating life of 10 years: approximately
$101,120 x 0.15349 (capital recovery factor at a 7 percent interest
rate)=$15,520; or
If replacing the spar cap is necessary for airplanes with
an average remaining operating life of 15 years: approximately
$101,120 x 0.11434 (capital recovery factor at a 7 percent interest
rate)=$11,562.
The required AD's from Dockets No. 92-CE-43-AD (for Models 500,
560A, 560E, 680, 680E, and 720) and No. 92-CE-58-AD (for Models 685,
690, 690A, and 690B) will also affect certain airplanes included in
this AD. The compliance costs of these other required AD's would add to
the cost discussed above. However, replacing the spar cap would only be
required once, so the $100,000 replacement cost, if required, would be
a one-time action.
The Regulatory Flexibility Act of 1980 (RFA) was enacted by
Congress to ensure that small entities are not unnecessarily or
disproportionally burdened by government regulations. The RFA requires
government agencies to determine whether rules would have a
``significant economic impact on a substantial number of small
entities,'' and, in cases where they would, conduct a Regulatory
Flexibility Analysis in which alternatives to the rule are considered.
FAA Order 2100.14A, Regulatory Flexibility Criteria and Guidance,
outlines FAA procedures and criteria for complying with the RFA. Small
entities are defined as small businesses and small not-for-profit
organizations that are independently owned and operated or airports
operated by small governmental jurisdictions.
The 331 U.S.-registered airplanes affected by the required AD that
have not complied with Twin Commander SB No. 212, dated November 3,
1992, are owned according to the following breakdown: 196 by
individuals, 2 by U.S. government agencies, 7 by states or local
governments, and 126 by other entities. Six entities own 2 airplanes
each.
The FAA cannot determine the sizes of all the affected non-
individual owner entities nor the relative significance of the costs
estimated above. Because of these uncertainties, no cost thresholds for
significant economic impact can be reasonably determined. Based on the
possibility that this AD could have a significant impact on a
substantial number of small entities, the FAA conducted a regulatory
flexibility analysis. A copy of this analysis may be obtained by
contacting the Rules Docket at the location provided under the caption
``ADDRESSES''.
The regulations adopted herein will not have substantial direct
effects on the States, on the relationship between the national
government and the States, or on the distribution of power and
responsibilities among the various levels of government. Therefore, in
accordance with Executive Order 12612, it is determined that this final
rule does not have sufficient federalism implications to warrant the
preparation of a Federalism Assessment.
For the reasons discussed above, I certify that this action (1) is
not a ``significant regulatory action'' under Executive Order 12866;
(2) is significant under DOT Regulatory Policies and Procedures (44 FR
11034, February 26, 1979) because of substantial public interest; and,
(3) may have a significant economic impact on a substantial number of
small entities. The FAA has conducted an Initial Regulatory Flexibility
Determination and Analysis and has considered alternatives to this
action that could minimize the impact on small entities. A copy of this
analysis may be obtained by contacting the Rules Docket at the location
provided under the caption ``ADDRESSES''. After careful consideration,
the FAA has determined that the required action is the best course to
achieve the safety objective of returning the airplane to its original
certification level of safety.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration amends 14 CFR part
39 of the Federal Aviation Regulations as follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C.
106(g); and 14 CFR 11.89
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new AD to read
as follows:
94-04-15 Twin Commander Aircraft Corporation: Amendment 39-8835;
Docket No. 92-CE-57-AD.
Applicability: The following model and serial number airplanes
that do not have the wing front spar lower cap replaced in
accordance with procedures specified in paragraph (a)(3) of this AD,
certificated in any category:
------------------------------------------------------------------------
Model Serial No.
------------------------------------------------------------------------
500.............................. 618 through 750.
560A............................. 231 through 450.
560E............................. 433 through 750.
680.............................. 242 through 658.
680E............................. 623 through 750.
720.............................. 501 through 750.
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Compliance: Required within the next 50 hours time-in-service
after the effective date of this AD, unless already accomplished.
To prevent failure of the wing structure caused by a cracked
wing front spar lower cap at Wing Station (WS) 96, accomplish the
following:
(a) Inspect the wing front spar lower cap of each wing for
corrosion or interference between the firewall flange and spar
flange in accordance with the ACCOMPLISHMENT INSTRUCTIONS section of
Twin Commander Service Bulletin (SB) No. 212, dated November 3,
1992.
(1) If any interference is found between the firewall flange and
spar flange, prior to further flight, clear this interference in
accordance with the ACCOMPLISHMENT INSTRUCTIONS section of Twin
Commander SB No. 212, dated November 3, 1992.
(2) If any corrosion damage is found, prior to further flight,
repair any corrosion damage to the wing front spar lower cap in
accordance with the ACCOMPLISHMENT INSTRUCTIONS section of Twin
Commander SB No. 212, dated November 3, 1992.
(3) If any cracks are found, prior to the further flight,
replace the wing front spar lower cap in accordance with replacement
procedures obtained from the manufacturer through the Manager,
Seattle Aircraft Certification Office (ACO), at the address
specified in paragraph (c) of this AD.
(b) Special flight permits may be issued in accordance with 14
CFR 21.197 and 21.199 to operate the airplane to a location where
the requirements of this AD can be accomplished.
(c) An alternative method of compliance or adjustment of the
compliance time that provides an equivalent level of safety may be
approved by the Manager, Seattle ACO, FAA, Northwest Mountain
Region, 1601 Lind Avenue SW., Renton, Washington 98055-4056. The
request shall be forwarded through an appropriate FAA Maintenance
Inspector, who may add comments and then send it to the Manager,
Seattle ACO, FAA, Northwest Mountain Region.
Note: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO, FAA, Northwest Mountain Region.
(d) The inspection and repair required by this AD shall be done
in accordance with Twin Commander Service Bulletin No. 212, dated
November 3, 1992. This incorporation by reference was approved by
the Director of the Federal Register in accordance with 5 U.S.C.
552(a) and 1 CFR part 51. Copies may be obtained from Twin Commander
Aircraft Corporation, 19003 59th Drive, NE., Arlington, Washington
98223. Copies may be inspected at the FAA, Central Region, Office of
the Assistant Chief Counsel, Room 1558, 601 E. 12th Street, Kansas
City, Missouri, or at the Office of the Federal Register, 800 North
Capitol Street, NW., suite 700, Washington, DC.
(e) This amendment (39-8835) becomes effective on April 12,
1994.
Issued in Kansas City, Missouri, on February 14, 1994.
Barry D. Clements,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. 94-3840 Filed 2-18-94; 8:45 am]
BILLING CODE 4910-13-4
