[Federal Register Volume 60, Number 84 (Tuesday, May 2, 1995)]
[Proposed Rules]
[Pages 21471-21473]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-10711]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 95-CE-20-AD]


Airworthiness Directives; Twin Commander Aircraft Corporation 
680, 681, 690, and 695 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes to adopt a new airworthiness directive 
(AD) that would apply to certain Twin Commander Aircraft Corporation 
(Twin Commander) 680, 681, 690, and 695 series airplanes. The proposed 
action would require installing a placard warning the pilot to observe 
turbulent air penetration speeds. Two accidents involving Model 690 
airplanes where the affected airplanes encountered turbulence while 
descending at high speeds prompted the proposed action. The actions 
specified by the proposed AD are intended to prevent structural damage 
to the airplane caused by excessive turbulence, which could result in 
loss of the airplane.

DATES: Comments must be received on or before June 28, 1995.

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-20-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. [[Page 21472]] 
    Service information that applies to the proposed AD may be obtained 
from the Twin Commander Aircraft Corporation, 19010 59th Drive, N.E., 
Arlington, Washington 98223. This information also may be examined at 
the Rules Docket at the address above.

FOR FURTHER INFORMATION CONTACT: Mr. Mike Pasion, Aerospace Engineer, 
FAA, Northwest Mountain Region, 1601 Lind Avenue S.W., Renton, 
Washington 98055-4056; telephone (206) 227-2594; facsimile (206) 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-20-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-20-AD, Room 1558, 601 E. 12th Street, 
Kansas City, Missouri 64106.

Discussion

    Two Twin Commander Model 690C airplanes were recently involved in 
accidents where the pilot encountered excessive turbulence while 
descending at high speeds. In both of these accidents the airplane was 
lost. Wind gusts associated with turbulence can result in increased 
loads on the wing, resulting in possible airplane structural damage and 
loss of the airplane.
    Reducing airspeed in turbulence reduces the effect of these gust-
induced loads during turbulence. Maintaining airspeed at Turbulent Air 
Penetration speed or Maneuvering speed provides an increase in 
structural margin when encountering turbulence. Operating the airplane 
at Maneuvering speed is the safest speed for flight in turbulence. 
Turbulent Air Penetration and Maneuvering speeds are both well below 
the red-line limits of the maximum operating limit speed (<SUP>VMO/
<SUP>MMO).
    Twin Commander has issued Service Bulletin No. 220, dated February 
1, 1995, which re-emphasizes the importance of reducing airspeed before 
descending into known turbulence or reducing airspeed immediately upon 
entering unexpected turbulence on the following airplanes:

------------------------------------------------------------------------
                    Models                             Serial No.       
------------------------------------------------------------------------
680T and 680V.................................  1473 through 1720.      
680W..........................................  1721 through 1850.      
681...........................................  6001 through 6072.      
690...........................................  11001 through 11079.    
690A..........................................  11100 through 11344.    
690B..........................................  11350 through 11566.    
690C..........................................  11600 through 11735.    
690D..........................................  15001 through 15042.    
695...........................................  95000 through 95084.    
695A..........................................  96000 through 96100.    
695B..........................................  96201 through 96208.    
------------------------------------------------------------------------

This service bulletin also references a placard and airplane flight 
manual/pilot operating handbook (AFM/POH) revisions to advise airplane 
operators of target speeds for operation during turbulence.
    After examining the circumstances and reviewing all available 
information related to the accidents described above including the 
referenced service information, the FAA has determined that AD action 
should be taken to prevent structural damage to the airplane caused by 
excessive turbulence, which could result in loss of the airplane.
    Since an unsafe condition has been identified that is likely to 
exist or develop in other Twin Commander 680, 681, 690, and 695 series 
airplanes (specific models and serial numbers presented above) of the 
same type design, the proposed AD would require incorporating a placard 
and AFM/POH revisions that warn the airplane operator of the importance 
of observing the Turbulent Air Penetration and Maneuvering speeds. The 
following kits include the placard and AFM/POH revisions:

------------------------------------------------------------------------
                Kit No.                          Model affected         
------------------------------------------------------------------------
SB220-1...............................  680T.                           
SB220-2...............................  680V.                           
SB220-3...............................  680W.                           
SB220-4...............................  681.                            
SB220-5...............................  690.                            
SB220-6...............................  690A.                           
SB220-7...............................  690B.                           
SB220-8...............................  690C.                           
SB220-9...............................  690D.                           
SB220-10..............................  695.                            
SB220-11..............................  695A.                           
SB220-12..............................  695B.                           
------------------------------------------------------------------------

    The FAA estimates that 566 airplanes in the U.S. registry would be 
affected by the proposed AD, that it would take approximately 1 
workhour per airplane to accomplish the proposed action, and that the 
average labor rate is approximately $60 an hour. Parts cost 
approximately $38 per airplane. Based on these figures, the total cost 
impact of the proposed AD on U.S. operators is estimated to be $55,468. 
This figure is based on the assumption that no affected airplane owner/
operator has incorporated the placard and AFM/POH revisions included 
with the applicable SB220 kit. Twin Commander has informed the FAA that 
no kits have been distributed to the owners/operators of the affected 
airplanes.
    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, 
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. A copy of the draft regulatory evaluation 
prepared for this action has been placed in the Rules 
[[Page 21473]] 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. 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 a new AD to read as follows:

Twin Commander Aircraft Corporation: Docket No. 95-CE-20-AD.

    Applicability: The following airplane models and serial numbers, 
certificated in any category.

------------------------------------------------------------------------
                    Models                             Serial No.       
------------------------------------------------------------------------
680T and 680V.................................  1473 through 1720.      
680W..........................................  1721 through 1850.      
681...........................................  6001 through 6072.      
690...........................................  11001 through 11079.    
690A..........................................  11100 through 11344.    
690B..........................................  11350 through 11566.    
690C..........................................  11600 through 11735.    
690D..........................................  15001 through 15042.    
695...........................................  95000 through 95084.    
695A..........................................  96000 through 96100.    
695B..........................................  96201 through 96208.    
------------------------------------------------------------------------

    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 use the authority 
provided in paragraph (c) of this AD to request approval from the 
FAA. This approval may address either no action, if the current 
configuration eliminates the unsafe condition, or different actions 
necessary to address the unsafe condition described in this AD. Such 
a request should include an assessment of the effect of the changed 
configuration on the unsafe condition addressed by this AD. In no 
case does the presence of any modification, alteration, or repair 
remove any airplane from the applicability of this AD.

    Compliance: Required within the next 50 hours time-in-service 
after the effective date of this AD, unless already accomplished.
    To prevent structural damage to the airplane caused by excessive 
turbulence, which could result in loss of the airplane, accomplish 
the following:
    (a) Install the placard (to the windshield centerpost) and 
incorporate the airplane flight manual/pilot operating handbook 
(AFM/POH) revisions that are included with the kits presented below. 
The placard and AFM/POH revisions provide warnings to the airplane 
operator of the importance of observing the Turbulent Air 
Penetration and Maneuvering speeds:

------------------------------------------------------------------------
                Kit No.                          Model affected         
------------------------------------------------------------------------
SB220-1...............................  680T.                           
SB220-2...............................  680V.                           
SB220-3...............................  680W.                           
SB220-4...............................  681.                            
SB220-5...............................  690.                            
SB220-6...............................  690A.                           
SB220-7...............................  690B.                           
SB220-8...............................  690C.                           
SB220-9...............................  690D.                           
SB220-10..............................  695.                            
SB220-11..............................  695A.                           
SB220-12..............................  695B.                           
------------------------------------------------------------------------

    Note 2: Twin Commander Service Bulletin No. 220, dated February 
1, 1995, relates to the subject of this AD, and references the SB220 
service kits specified above.

    (b) Special flight permits may be issued in accordance with 
Secs. 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.
    (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 Aircraft Certification Office 
(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.

    Note 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (d) All persons affected by this directive may obtain copies of 
the document referred to herein upon request to the Twin Commander 
Aircraft Corporation, 19010 59th Drive, NE., Arlington, Washington 
98223; 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 April 26, 1995.
Henry A. Armstrong,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 95-10711 Filed 5-1-95; 8:45 am]
BILLING CODE 4910-13-U