TDATA NOTE: In the original copy of this AD,  the  FAA  omitted  Figure 7.
            The FAA issued a correction to include the figure.  This  copy
            reflects the correction.

(a) EFFECTIVE DATE

This AD is effective September 6, 2011.

(b) AFFECTED ADS

AD 2010-21-18,  Amendment 39-16478,  is related to the subject of this AD.

(c) APPLICABILITY

This AD applies to Cessna Aircraft Company (Cessna) Models 337, 337A (USAF
02B), 337B,  337C, 337D,  337E, T337E,  337F, T337F,  337G, T337G,  M337B,
F337E, FT337E, F337F,  FT337F, F337G, and  FT337GP  airplanes, all  serial
numbers, that:

(1) Are certificated in any category; and

(2) Are or have ever been modified by  Flint Aero, Inc.  Supplemental Type
    Certificate (STC) SA5090NM.

(d) SUBJECT

Joint Aircraft System Component (JASC)/Air Transport Association (ATA)  of
America Code 57; Wings.

(e) UNSAFE CONDITION

This AD was prompted  by a review of  installed Flint Aero, Inc.  wing tip
auxiliary fuel tanks, STC SA5090NM. We  are issuing this AD to detect  and
correct damage in the  wings and to prevent  overload failure of the  wing
due to the installation of the STC. Damage in the wing or overload failure
of the wing could  result in structural failure  of the wing, which  could
result in loss of control.

(f) COMPLIANCE

Comply  with  this  AD  within  the  compliance  times  specified,  unless
already done.

(g) REQUIRED ACTIONS

(1) Within the next 50 hours time-in-service (TIS) after September 6, 2011
    (the effective date of this AD)  or  within 30 days after September 6,
    2011 (the  effective date  of this  AD), whichever  occurs first, do a
    general and focused inspection of the left and right wing for internal
    and  external damage  at wing  stations (WSTA)  150 and  177.  Do  the
    inspections following Appendix 1 of this AD.

(2) After the  inspection  required  in  paragraph (g)(1) of this AD if no
    damage was  found and  before the  modification required  in paragraph
    (g)(5)  of  this AD  is  incorporated, anytime  severe  and/or extreme
    turbulence is encountered during flight,  before the next flight do  a
    focused inspection of the wing for damage following steps 1, 2, 3,  4,
    7, and 10 in Appendix 1 of this AD. Also inspect for signs of distress
    in the  upper front  spar in  the area  around WSTA  150 and  177. The
    definition of severe and extreme turbulence can be found in table  7-1
    -9 of the FAA Aeronautical Information Manual (AIM). You may obtain  a
    copy           of          the           FAA          AIM           at
    http://www.faa.gov/air_traffic/publications/atpubs/aim/.

(3) For  airplanes  that  have  not  had  the  modification  specified  in
    paragraphs (g)(4) and  (g)(5) incorporated, within  the next 50  hours
    time-in-service (TIS) after September  6, 2011 (the effective  date of
    this AD) or within 30 days after September 6, 2011 (the effective date
    of this AD),  fabricate  a  placard (using at least 1/8-inch  letters)
    with the  following words  and install  the placard  on the instrument
    panel within the pilot's clear view:

(i) "MAINTAIN  AT  LEAST  12  GAL  OF  FUEL IN EACH WING TIP FUEL TANK FOR
    AIRPLANE WEIGHTS BETWEEN 3,400 LBS AND 4,330 LBS."

(ii) "MAINTAIN FULL FUEL  IN EACH WING  TIP FUEL TANK FOR AIRPLANE WEIGHTS
     AT OR ABOVE 4,330 LBS."

(4) If damage or signs  of  distress  are  found  during  the  inspections
    required in paragraphs  (g)(1) and (g)(2)  of this AD,  before further
    flight do the following:

(i) Repair  all  damaged  and  distressed  parts  following  FAA  Advisory
    Circular   (AC)  43.13-1B,   Chapter  4,   which  can   be  found   at
    http://rgl.faa.gov/;

(ii) Incorporate the modification reinforcement specified  in  Flint Aero,
     Inc. Service Bulletin FA2, Rev 2, dated April 8, 2011, or Flint Aero,
     Inc. Service Bulletin FA2, Rev 3, dated May 3, 2011, following  Flint
     Aero, Inc. Drawing FA2, Rev A, dated April 8, 2011;

(iii) Remove the placard specified in paragraph (g)(3) of this AD;

(iv) Fabricate  a  new placard (using at least 1/8-inch letters) with  the
     following  words  and install  the  placard on  the  instrument panel
     within the pilot's clear view: "MAINTAIN  AT LEAST 12 GAL OF FUEL  IN
     EACH WING TIP FUEL TANK FOR AIRPLANE WEIGHTS AT OR ABOVE 4,330  LBS";
     and

(v) Incorporate  the  information  from  Appendix 2 of this  AD  into  the
    Limitations section  of the  Flint Aero,  Inc. Airplane  Flight Manual
    Supplement.

(5) If no damage or  signs of distress  are  found  during the inspections
    required in paragraphs (g)(1) and  (g)(2) of this AD, within  the next
    100 hours TIS after September 6, 2011 (the effective date of this  AD)
    or within  12 months  after September  6, 2011  (the effective date of
    this AD), whichever occurs first, do the following:

(i) Incorporate the  modification  reinforcement  specified in Flint Aero,
    Inc. Service Bulletin FA2, Rev 2, dated April 8, 2011, or Flint  Aero,
    Inc. Service Bulletin FA2, Rev  3, dated May 3, 2011,  following Flint
    Aero, Inc. Drawing FA2, Rev A, dated April 8, 2011;

(ii) Remove the placard specified in paragraph (g)(3) of this AD;

(iii) Fabricate a  new  placard (using at least 1/8-inch letters) with the
      following  words and  install the  placard on  the instrument  panel
      within the pilot's clear view: "MAINTAIN AT LEAST 12 GAL OF FUEL  IN
      EACH WING TIP FUEL TANK FOR AIRPLANE WEIGHTS AT OR ABOVE 4,330 LBS";
      and

(iv) Incorporate  the  information  from  Appendix 2 of this AD  into  the
     Limitations section of  the Flint Aero,  Inc. Airplane Flight  Manual
     Supplement.

(6) You may incorporate the  modification reinforcement specified in Flint
    Aero, Inc. Service Bulletin FA2, Rev 2, dated April 8, 2011, or  Flint
    Aero, Inc. Service Bulletin FA2,  Rev 3, dated May 3,  2011, following
    Flint Aero, Inc. Drawing FA2, Rev A, dated April 8, 2011, at any  time
    after the inspection  required in paragraph  (g)(1) of this  AD but no
    later than the compliance time  specified in paragraph (g)(5) of  this
    AD as long as no cracks were found. As required in paragraph (g)(4) of
    this AD,  the modification  reinforcement must  be incorporated before
    further flight if damage or signs of distress are found.

(h) ALTERNATIVE METHODS OF COMPLIANCE (AMOCS)

(1) The Manager, Los Angeles Aircraft Certification Office (ACO), FAA, has
    the authority  to approve  AMOCs for  this AD,  if requested using the
    procedures found  in 14  CFR 39.19.  In accordance  with 14 CFR 39.19,
    send  your  request  to  your  principal  inspector  or  local  Flight
    Standards  District  Office, as  appropriate.  If sending  information
    directly to the manager  of the ACO, send  it to the attention  of the
    person identified in the Related Information section of this AD.

(2) Before using any approved  AMOC,  notify  your  appropriate  principal
    inspector, or lacking a principal inspector, the manager of the  local
    flight standards district office/certificate holding district office.

(i) RELATED INFORMATION

For  more  information about  this  AD, contact  Dara  Albouyeh, Aerospace
Engineer, FAA, Los Angeles ACO, 3960 Paramount Blvd., Lakewood, CA  90712;
phone: (562) 627-5222; fax: (562) 627-5210; e-mail: dara.albouyeh@faa.gov.

(j) MATERIAL INCORPORATED BY REFERENCE

(1) You  must  use  the  following  service  information to do the actions
    required by this AD, unless  the AD specifies otherwise. The  Director
    of the Federal Register approved the incorporation by reference  (IBR)
    under 5  U.S.C. 552(a)  and 1  CFR part  51 of  the following  service
    information on September 6, 2011:

(i) Flint Aero, Inc. Service Bulletin FA2, Rev 2, dated April 8, 2011;

(ii) Flint Aero, Inc. Service Bulletin FA2, Rev 3, dated May 3, 2011; and

(iii) Flint Aero, Inc. Drawing FA2, Rev A, dated April 8, 2011.

(2) For service information identified in  this  AD,  contact  Flint Aero,
    Inc., 1942  Joe Crosson  Drive, El  Cajon, CA  92020; phone: (619) 448
    -1551; fax: (619) 448-1571; Internet: http://www.flintaero.com.

(3) You may review  copies  of  the  referenced service information at the
    FAA, Small Airplane  Directorate, 901 Locust,  Kansas City, MO  64106.
    For information on the availability of this material at the FAA,  call
    (816) 329-4148.

(4) You  may  also  review  copies  of  the  service  information  that is
    incorporated  by  reference  at  the  National  Archives  and  Records
    Administration (NARA).  For information  on the  availability of  this
    material at an NARA facility, call 202-741-6030, or go to
    http://www.archives.gov/federal_register/code_of_federal_regulations/i
    br_locations.html.

APPENDIX 1 TO AD 2011-15-11

GENERAL AND FOCUSED INSPECTION PROCEDURES

Perform a  general and  focused inspection  of the  wing for  internal and
external damage from wing station (WSTA)  23 to the wing tip. The  general
inspection must be performed in  accordance with 14 CFR 43.15(c),  using a
checklist  that  includes at  least  the scope  and  detail of  the  items
contained in Appendix  D of 14  CFR part 43.  The focused inspection  must
include the items listed below.  Remove all wing access panels  to conduct
the inspections. Do these inspections following the manufacturer's service
information  and  any other  appropriate  guidance, such  as  FAA Advisory
Circular  (AC)  43.13-1B Acceptable  Methods,  Techniques, and  Practices-
-Aircraft   Inspection  and   Repair.  AC   43.13-1B  can   be  found   at
http://rgl.faa.gov/.

Focused inspection items to look for:

(1) Wrinkles in upper wing skins,  from the outboard edge on the fuel tank
    access covers (WSTA 150  or 177) to the  WSTA 222 (See View  B, Figure
    3).

(2) Wrinkles in the upper wing skins  from WSTA 55 to 66,  adjacent to the
    booms (See View E, Figure 6).

(3) Cracking of the upper wing skins.  Pay  particular  attention  to  any
    wrinkles,  the radius between stiffeners  at WSTA 150 (under fuel tank
    covers), and unreinforced access holes (See View B, Figure 3).

(4) Working (smoking) rivets outboard of the wing tank access covers.

(5) Fasteners with less than two diameters edge distance.

(6) Fasteners with less than four diameters center to center spacing.

(7) Looseness of attachments of the tip extension to the wing and wing tip
    to wing extension when pushing up and down on the tip.

(8) Any signs of distress along both front and rear spars, particularly in
    the area around WSTA 177.

(9) Inspect under any repairs to the upper skins, particularly in the area
    just outboard of the fuel tank access covers as these may be  covering
    up existing damage.

(10) Inter-rivet buckling of  the  stringers attached to the upper surface
     skin, outboard of the fuel tank access covers (See View F, Figure 7).

(11) Inspect rib at WSTA 222 for damage. Trimming of the rib may have been
     done to  allow installation  of fuel  lines (See  View A,  Figure 2).
     Repair in accordance with  AC 43.13-1B, Chapter 4,  paragraph 4-58(g)
     and  Figure  4-14,  or  by  using  another  FAA-approved  method that
     restores equivalent strength of the wing rib.

(12) Inspect and identify screws,  installed in tapped (threaded) holes in
     metal substructure, used to attach wing tips, stall fences, fuel  and
     electrical components,  and access  doors. For  tapped holes,  remove
     fastener and open up the diameter to provide a smooth bore hole,  for
     the smallest oversize fastener, using close tolerance holes noted  in
     AC 43.13-1B,  paragraph 7-39  or other  FAA-approved scheme. Maintain
     minimum 2 x fastener diameter edge distance and 4 x fastener diameter
     center to center spacing. Select and install new, equivalent strength
     or stronger, fasteners with nuts/collars in accordance with AC  43.13
     -1B, Chapter 7 and AC  43.13-2B, paragraph 108 or other  FAA-approved
     repair. New fasteners  must not have  threads in bearing  against the
     sides of the holes.

(13) Inspect wing skins for unreinforced cutouts. (See View C, Figure 4).

(14) Inspect the upper spar cap  horizontal  flanges  for  open holes (See
     View D, Figure 5).

                        ILLUSTRATION (Figure 1)

                        ILLUSTRATION (Figure 2)

                        ILLUSTRATION (Figure 3)

                        ILLUSTRATION (Figure 4)

                        ILLUSTRATION (Figure 5)

                        ILLUSTRATION (Figure 6)

                        ILLUSTRATION (Figure 7)

APPENDIX 2 TO AD 2011-15-11

Airworthiness Limitations for the Flint Aero, Inc. Airplane Flight  Manual
Supplement.

"MAINTAIN AT LEAST 12 GAL OF FUEL IN EACH WING TIP FUEL TANK FOR  AIRPLANE
WEIGHTS AT OR ABOVE 4,330 LBS."

Issued in Kansas City, Missouri, on July 14, 2011. Earl Lawrence, Manager,
Small Airplane Directorate, Aircraft Certification Service.

FOR FURTHER INFORMATION CONTACT:  Dara Albouyeh, Aerospace Engineer,  FAA,
Los Angeles Aircraft Certification Office, 3960 Paramount Blvd., Lakewood,
CA   90712;  phone:   (562)  627-5222;   fax:  (562)   627-5210;   e-mail:
dara.albouyeh@faa.gov.