[Federal Register Volume 62, Number 160 (Tuesday, August 19, 1997)]
[Proposed Rules]
[Pages 44096-44099]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-21873]


========================================================================
Proposed Rules
                                                Federal Register
________________________________________________________________________

This section of the FEDERAL REGISTER contains notices to the public of 
the proposed issuance of rules and regulations. The purpose of these 
notices is to give interested persons an opportunity to participate in 
the rule making prior to the adoption of the final rules.

========================================================================


Federal Register / Vol. 62, No. 160 / Tuesday, August 19, 1997 / 
Proposed Rules

[[Page 44096]]


=======================================================================
-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95-CE-92-AD]
RIN 2120-AA64


Airworthiness Directives; Twin Commander Aircraft Corporation 
500, 600, and 700 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: This document proposes to adopt a new airworthiness directive 
(AD) that would apply to Twin Commander Aircraft Corporation 500, 600, 
and 700 series airplanes. The proposed action would require installing 
access holes in both wing leading edges and repetitively inspecting the 
forward attach brackets and straps for cracks. Reports of cracks in the 
wing to fuselage attachment brackets and straps, wing station (WS) 24, 
and fuselage frames prompted the proposed action. The actions specified 
by the proposed AD are intended to detect cracks at the wing to 
fuselage attach points, which, if not detected and corrected, could 
cause structural failure and loss of control of the airplane.

DATES: Comments must be received on or before October 24, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Central Region, Office of the Assistant Chief 
Counsel, Attention: Rules Docket No. 95-CE-92-AD, Room 1558, 601 E. 
12th Street, Kansas City, Missouri 64106. Comments may be inspected at 
this location between 8 a.m. and 4 p.m., Monday through Friday, 
holidays excepted.
    Service information that applies to the proposed AD may be obtained 
from Twin Commander Aircraft Corporation, P.O. Box 3369, Arlington, 
Washington, 98223; telephone (360) 435-9797; facsimile (360) 435-1112. 
This information also may be examined at the Rules Docket at the 
address above.

FOR FURTHER INFORMATION CONTACT: Jeffrey Morfitt, Aerospace Engineer, 
FAA, Seattle Aircraft Certification Office, 1601 Lind Ave. S.W., 
Renton, Washington, 98055-4056; telephone (425) 227-2595; facsimile 
(425) 227-1181.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications should identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report that summarizes each FAA-public contact concerned 
with the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket No. 95-CE-92-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Central Region, Office of the Assistant Chief Counsel, 
Attention: Rules Docket No. 95-CE-92-AD, Room 1558, 601 E. 12th Street, 
Kansas City, Missouri 64106.

Discussion

    There have been 14 reports of cracking at the wing leading edge 
spar and fuselage attach point in recent years on certain Twin 
Commander 500, 600, and 700 series airplanes. Two Australian airplanes 
out of the 14 were reported to have extensive cracking in the wing 
leading edge spar, the wing station (W.S.) 24 rib, the fuselage station 
(F.S.) 100 frame, and in the attachment brackets between the kick 
fitting and the leading edge spar. Further investigation found 12 other 
Twin Commander airplanes with similar cracking. In addition, Twin 
Commander Models 690D and 695A airplanes were found to have adjacent 
detail cracking while undergoing full scale fatigue tests. The Twin 
Commander Models 690D and 695A airplanes are currently inspected in the 
wing structure under Airworthiness Directive (AD) 95-12-23 which 
mandates the procedures and actions in Twin Commander Service Bulletin 
No. 213, dated July 24, 1994. This proposed action would cover 
additional series airplanes as well as require repetitively inspecting 
and modifying the wing leading edge by installing access holes for 
thorough access to the fatigued areas.

Relevant Service Information

    Twin Commander has issued Service Bulletin (SB) No. 223, dated 
October 24, 1996 as amended by Revision Notice No. 1, dated May 8, 
1997, which specifies installing access holes in both wing leading 
edges, inspecting for cracks, and replacing or repairing any cracked 
part and continuing to repetitively inspect.

The FAA's Determination

    After examining the circumstances and reviewing all available 
information related to the incidents described above, the FAA has 
determined that AD action should be taken to detect cracks at the wing 
to fuselage attach points, which, if not detected and corrected, could 
cause structural failure and loss of control of the airplane.

Explanation of the Provisions of the Proposed AD

    Since an unsafe condition has been identified that is likely to 
exist or develop in other Twin Commander 500, 600, and 700 series 
airplanes of the same type design, the proposed AD would require the 
following actions:

[[Page 44097]]



----------------------------------------------------------------------------------------------------------------
                                                  A                        B                        C           
----------------------------------------------------------------------------------------------------------------
Part I...............................  Installing access holes  If cracked, prior to     If no cracks, repeat   
                                        in left and right wing   further flight,          the inspection at     
                                        leading edges and        replacing the brackets   regular intervals     
                                        inspecting forward       and straps or            until cracks are      
                                        attach brackets and      repairing the part       found, then accomplish
                                        straps for cracks..      with an approved         PART II.              
                                                                 repair scheme. Then                            
                                                                 accomplish PART II of                          
                                                                 this AD.                                       
Part II..............................  Inspecting for cracks    If cracked, prior to     After repairing or     
                                        on both wing leading     further flight,          replacing the damaged 
                                        edge close-outs, upper   replacing any cracked    part, continuing to   
                                        & lower return flange    part or repairing the    inspect at regular    
                                        radius, fuselage frame   part with an approved    intervals.            
                                        where tee bracket        repair scheme.                                 
                                        attaches, inboard side                                                  
                                        of attach bracket and                                                   
                                        frame tee bracket.                                                      
Part III.............................  Inspecting fuselage      If cracked, prior to     If no cracks, repeating
                                        station (f.s.) 100 for   further flight,          the inspection at     
                                        cracks.                  repairing with an        regular intervals     
                                                                 approved repair          until cracks are      
                                                                 scheme, and continuing   found, then           
                                                                 to inspect at regular    accomplishing PART III
                                                                 intervals.               B of this AD.         
----------------------------------------------------------------------------------------------------------------

    Note: Models 520 and 560 airplanes only are excluded from 
installing the wing leading edge access holes and inspection 
proposed in PART I of the above table.
    Note: Models 690C and 695 airplanes are excluded from the 
proposed inspection in PART III in the above table.

Cost Impact

    The FAA estimates that 1,887 airplanes in the U.S. registry would 
be affected by the proposed AD, that it would take approximately 82 
workhours for PART I; 100 workhours for PART II (if required); and 7 
workhours for PART III per airplane to accomplish the proposed action. 
The average labor rate is approximately $60 an hour. Parts cost 
approximately $410 for PART I and approximately $450 for PART II (if 
required) per airplane. Based on these figures, the total cost impact 
for PART I would be $5,330 per airplane, PART II (if required) would be 
$6,450 per airplane, and PART III would be $420 per airplane. The U.S. 
fleet cost is estimated to be $11,127,650, or $5,950 per airplane if no 
damage is found; and $23,021,400 for the U.S. fleet, or $12,200 per 
airplane if damage is found. For purposes of estimating the cost of the 
proposed AD, the FAA is presuming that none of the owners/operators of 
the affected airplanes have accomplished any of the actions on any of 
the affected airplanes. In addition, the cost impact does not take into 
consideration the costs of the repetitive inspections. The FAA has no 
way of determining the number of repetitive inspections that may be 
incurred over the life of the airplane.

Regulatory Flexibility Act Economic Analysis

    Because the estimated cost for the proposed inspection and possible 
repairs are expensive, the FAA conducted a Cost Analysis and Initial 
Regulatory Flexibility Determination and Analysis for the proposed AD.
    The Regulatory Flexibility Act of 1980 (RFA) was enacted by 
Congress to assure that small entities are not unnecessarily and 
disproportionately burdened by Government regulations. The RFA requires 
agencies to review rules that may have a ``significant economic impact 
on a substantial number of small entities,'' and, in cases where they 
would, to conduct a Regulatory Flexibility Analysis in which 
alternative actions are considered.
    FAA Order 2100.14A, Regulatory Flexibility Criteria and Guidance, 
defines ``significant economic impact'' as an annualized net compliance 
cost, adjusted for inflation, which is greater than a threshold cost 
level for defined entity types. A ``substantial number'' is defined as 
a number that is at least eleven and that is more than one-third of the 
small entities subject to a proposed rule, or any number of small 
entities subject to a rule which is substantial in the judgment of the 
rulemaking official. Small entities are defined as small businesses, 
small not-for-profit organizations which are independently owned and 
operated, or airports operated by small governmental jurisdictions.
    With limited information available to airplane specific costs, a 
range of per airplane costs can be estimated by constructing 
hypothetical low- and high-cost scenarios. These scenarios are based on 
three general presumptions: first, that these airplanes have 
accumulated 6,000 hours TIS, and will be subject to the proposed AD 
within the next 100 hours TIS; second, that all of these airplanes are 
at the minimum and maximum extremes of annual TIS (200 or 300 hours), 
remaining operating life (10 and 20 years), and the extent of cracking 
(no cracking or cracking in the inspected areas); and third, that these 
airplanes are of the model types incurring either the lowest or highest 
costs.
    The total low-cost scenario in 1997 dollars would be $5,570 ($4,805 
discounted) per airplane over 10 years, with $5,330 of the costs 
incurred in the first year. The annualized cost (again over 10 years) 
would be $641 per airplane.
    The total high-cost scenario in 1997 dollars would be $25,285 per 
airplane ($16,487 discounted) over 30 years, with $15,865 of the costs 
incurred in the first year. The annualized cost (again over 30 years) 
would be $1,556.
    The proposed AD would affect approximately 1,464 airplanes, of 
which 366 are owned by individuals, 38 are owned by federal and state 
agencies, and 847 are owned by 697 separate entities. Of the 697 
entities, 1 entity owns 28 airplanes, 3 entities own between 10 and 12 
airplanes, 19 separate entities own between 3 and 9 airplanes, thirty-
two entities own 2 airplanes, and 642 entities own 1 airplane. The FAA 
cannot determine the size of all 697 owner entities, or the type of 
business each entity is engaged in. The FAA also cannot conclusively 
determine the costs of this AD. For illustration purposes, it was 
calculated that the proposed AD would have hypothetical annualized 
costs between $641 (the low-cost scenario) and $1,556 (the high-cost 
scenario) per airplane. Due to the uncertainties involved with these 
calculations, as well as with the ownership information, no 
determinations can be made regarding ``significant economic impact on a 
substantial number of small entities.''
    The FAA has considered three alternatives to this proposed AD: (1) 
take no federal action and rely on voluntary compliance with the Twin 
Commander Service Bulletin No. 223. The FAA finds this alternative 
unacceptable because of the consequences that could result; (2) mandate 
inspecting fewer parts, and at longer intervals in the areas where the 
wings attach to the fuselage. This

[[Page 44098]]

alternative is unacceptable because less stringent inspections could 
fail to locate cracking in key parts of the airplane for too long a 
period of time; (3) defer Federal action pending review of additional 
data to determine whether to require the specified inspections. This 
alternative is unacceptable because evidence already exists of cracking 
in the wing and fuselage at the attach points which would be considered 
structural failure.
    Consequently, the FAA is unable to conclusively make an economic 
impact evaluation based on information available.

Regulatory Impact

    The regulations proposed herein would not have substantial direct 
effects on the States, on the relationship between the national 
government and the States, or on the distribution of power and 
responsibilities among the various levels of government. Therefore, in 
accordance with Executive Order 12612, it is determined that this 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and (3) if promulgated, 
could have a significant economic impact, positive or negative, on a 
substantial number of small entities under the criteria of the 
Regulatory Flexibility Act (a determination was not able to be made). A 
copy of the draft regulatory evaluation prepared for this action has 
been placed in the Rules Docket. A copy of it may be obtained by 
contacting the Rules Docket at the location provided under the caption 
ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
part 39 of the Federal Aviation Regulations (14 CFR part 39) as 
follows:

PART 39--AIRWORTHINESS DIRECTIVES

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

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


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding a new airworthiness directive 
(AD) to read as follows:

Twin Commander Aircraft Corporation: Docket No. 95-CE-92-AD.

    Applicability: Models 500, 500A, 500B, 500S, 500U, 520, 560, 
560A, 560E, 560F, 680, 680E, 680F, 680FL, 680FLP, 680FP, 680T, 680V, 
680W, 681, 685, 690, 690A, 690B, 690C, 690D, 695, 695A, 695B and 720 
airplanes (all serial numbers), certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
modified, altered, or repaired in the area subject to the 
requirements of this AD. For airplanes that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (f) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.
    Compliance: Required as indicated in the body of this AD, unless 
already accomplished.
    To prevent cracks at the wing to fuselage attach points, which, 
if not detected and corrected, could cause structural failure and 
loss of control of the airplane, accomplish the following:
    (a) For all models except Models 520, 560, 690C and 695, 
accomplish the actions in the following table in accordance with the 
Compliance section and PART I, II, and III of the ACCOMPLISHMENT 
INSTRUCTIONS sections of Twin Commander Aircraft Corporation (Twin 
Commander) Service Bulletin (SB) No. 223, dated October 24, 1996 as 
amended by Revision Notice No. 1, dated May 8, 1997:

----------------------------------------------------------------------------------------------------------------
                                                  A                        B                        C           
----------------------------------------------------------------------------------------------------------------
PART I...............................  Upon the accumulation    If cracked, prior to     If no cracks are found,
                                        of 6,000 hours total     further flight,          repeat inspection at  
                                        time-in-service (TIS)    replace the brackets     1,000 hour (hr.)      
                                        or within the next 100   and straps or repair     intervals until cracks
                                        hours TIS, whichever     the part by an           are found, replace the
                                        occurs later, install    approved repair scheme   cracked part or repair
                                        access holes in left     (see paragraph (b) of    by an approved repair 
                                        and right wing leading   this AD). Then,          scheme (see paragraph 
                                        edges and inspect the    accomplish PART II of    (b) of this AD), then 
                                        forward attach           this AD.                 accomplish PART II.   
                                        brackets and straps                                                     
                                        for cracks.                                                             
                                       (Accomplish in           (Accomplish in           (Accomplish in         
                                        accordance with PART I   accordance with PART I   accordance with PART I
                                        of Compliance Section    of Compliance Section    of Compliance Section 
                                        in Twin Commander SB     in Twin Commander SB     in Twin Commander SB  
                                        223, dated Oct. 24,      223, dated Oct. 24,      223, dated Oct. 24,   
                                        1996 as amended by       1996 as amended by       1996 as amended by    
                                        Revision Notice No. 1,   Revision Notice No. 1,   Revision Notice No. 1,
                                        dated May 8, 1997.)      dated May 8, 1997.)      dated May 8, 1997.)   
PART II..............................  Inspect for cracks at    If cracked, prior to     After repair or        
                                        the wing leading edge    further flight,          replacement is        
                                        close-outs, upper &      replace any cracked      accomplished, continue
                                        lower return flange      part or repair the       to inspect at 6,000   
                                        radius, fuselage frame   part with an approved    hr. intervals.        
                                        where tee bracket        repair scheme (see                             
                                        attaches, inboard side   paragraph (b) of this                          
                                        of attach bracket and    AD). If no cracks are                          
                                        frame tee bracket.       found, continue to                             
                                                                 repetitively inspect                           
                                                                 at 1,000 hour TIS                              
                                                                 intervals.                                     
                                       (Accomplish in           (Accomplish in           (Accomplish in         
                                        accordance with PART     accordance with PART     accordance with PART  
                                        II of Compliance         II of Compliance         II of Compliance      
                                        Section in Twin          Section in Twin          Section in Twin       
                                        Commander SB 223,        Commander SB 223,        Commander SB 223,     
                                        dated Oct. 24, 1996 as   dated Oct. 24, 1996 as   dated Oct. 24, 1996 as
                                        amended by Revision      amended by Revision      amended by Revision   
                                        Notice No. 1, dated      Notice No. 1, dated      Notice No. 1, dated   
                                        May 8, 1997.)            May 8, 1997.)            May 8, 1997.)         

[[Page 44099]]

                                                                                                                
                                       For pressurized          If cracked, prior to     If no cracks, repeat   
                                        airplanes, at 6,000      further flight, repair   inspection at 1,000   
                                        hr. total TIS or         with an approved         hr. intervals until   
                                        within the next 100      repair scheme (see       cracks are found, then
                                        hours TIS whichever      paragraph (b) of this    accomplish PART III B 
                                        occurs later, inspect    AD), and continue to     of this AD            
                                        fuselage station         inspect at 1,000 hr.                           
                                        (F.S.) 100 for cracks.   intervals.                                     
PART III.............................  For non-pressurized      (Accomplish in           (Accomplish in         
                                        airplanes, at 12,000     accordance with PART     accordance with PART  
                                        hr. total TIS or         III of Compliance        III of Compliance     
                                        within the next 100      Section in Twin          Section in Twin       
                                        hours TIS whichever      Commander SB 223,        Commander SB 223,     
                                        occurs later, inspect    dated Oct. 24, 1996 as   dated Oct. 24, 1996 as
                                        F.S. 100 for cracks..    amended by Revision      amended by Revision   
                                       (Accomplish in            Notice No. 1, dated      Notice No. 1, dated   
                                        accordance with PART     May 8, 1997.)            May 8, 1997.)         
                                        III of Compliance                                                       
                                        Section in Twin                                                         
                                        Commander SB 223,                                                       
                                        dated Oct. 24, 1996 as                                                  
                                        amended by Revision                                                     
                                        Notice No. 1, dated                                                     
                                        May 8, 1997.)                                                           
----------------------------------------------------------------------------------------------------------------

    (b) Obtain an FAA-approved repair scheme from the manufacturer 
through the Manager of the Seattle Aircraft Certification Office at 
the address specified in paragraph (f) of this AD.
    (c) For Twin Commander Models 520 and 560 airplanes, upon the 
accumulation of 6,000 hours total TIS or within the next 100 hours 
TIS whichever occurs later, accomplish PART II of the table in 
paragraph (a) of this AD. Accomplish PART III in accordance with the 
compliance times in the above table of paragraph (a). These models 
are excluded from the wing leading edge access hole installation in 
PART I of the table in paragraph (a) of this AD.
    (d) For Twin Commander Models 690C and 695 airplanes, accomplish 
PARTS I and II in accordance with the compliance times in the above 
table of paragraph (a). These Models are excluded from PART III of 
the table in paragraph (a) of this AD.
    (e) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the airplane to a location where 
the requirements of this AD can be accomplished.
    (f) An alternative method of compliance or adjustment of the 
initial or repetitive compliance times that provides an equivalent 
level of safety may be approved by the Manager, Seattle Aircraft 
Certification Office, 1601 Lind Ave. 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 Aircraft Certification Office.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle Aircraft Certification Office.

    (g) All persons affected by this directive may obtain copies of 
the document referred to herein upon request to Twin Commander 
Aircraft Corporation, P.O. Box 3369, Arlington, Washington 98223; 
telephone (360) 435-9797; facsimile (360) 435-1112; or may examine 
this document at the FAA, Central Region, Office of the Assistant 
Chief Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri 
64106.

    Issued in Kansas City, Missouri, on August 12, 1997.
Michael Gallagher,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. 97-21873 Filed 8-18-97; 8:45 am]
BILLING CODE 4910-13-P