Wing Structure; Wingtip Extensions

Wing Structure; Wingtip Extensions

At this time, the airworthiness concern is not an unsafe condition that would warrant airworthiness
directive (AD) action under Title 14 of the Code of Federal Aviation Regulations (14 CFR) part 39.
Focused inspection items to focus on:
Aviation Safety
CE-10-20 R1
May 12, 2010
SUBJ: Wing Structure; Wingtip Extensions
This is information only. Recommendations aren’t mandatory.
This revised special airworthiness information bulletin (SAIB) alerts owners and operators of Cessna
Models 336, 337, and F337 (Reims) series airplanes with wingtip extensions of actions that
should enhance the safety of your airplane.
This revision is a result of comments received from individuals and other airworthiness authorities. It
corrects a typographical error, adds to the list of models potentially affected, and adds to the list of
focused inspections.
This SAIB is based on preliminary investigation findings from a fatal accident involving a Cessna
Model T337G. The airplane experienced separation of a six-foot section of the outboard right wing.
This airplane had been modified with an STC for extended wingtips. It also had an additional STC
for winglets. For more information on the accident, see the NTSB preliminary report ERA10FA140.
The subsequent investigation revealed there have also been reports from the field of wrinkled skins,
working rivets, cracks, and loose wing tips. The FAA notes that following service information has
been issued.

Cessna Service Newsletter SNL06-6, FAA Approved Supplemental Type Certificates (STC’s)
and FAA-PMA Approved Parts
Aviation Enterprises Wing Extension Service Letter AE01-11-00

After reviewing the above data, we recommend that you do the following:
1. Review and adhere to all published airspeed and maneuvering limitations for the modified
airplane. Look for excessive “bowing” of the tip extensions in flight.
2. Perform a one-time general inspection of the wings for internal and external damage from Wing
Station (WSTA) 23 to the wing tip within the next 100 hours time-in-service (TIS). Remove all
wing access panels to conduct the inspection. Areas to focus on are listed below. Do this
inspection following the appropriate manufacture’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.

3. In the case of multiple STC installations on the same aircraft, make sure the following
determination, noted on the STC certificate, has been made: "This approval should not be
extended to aircraft of this model on which other previously approved modifications are
incorporated unless it is determined that the interrelationship between this change and any of
those other previously approved modifications will introduce no adverse effect upon the
airworthiness of that aircraft."
Under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.), the Office of
Management and Budget (OMB) has approved the information collection contained in this
SAIB, and assigned OMB Control Number 2120-0731.
This is an on-going investigation, we request that if any damage if found, notify us at the
address for the Atlanta Aircraft Certification Office listed below. Please include as much
information as possible, including “N” number, model number, serial number, list of STC
modifications, TIS on aircraft and wing extension, physical description of damage (location,
length, orientation, parts cracked, etc.), and if possible, pictures of the damage.
Wrinkles in upper wing skins;
Cracking of the upper wing skins. Pay particular attention to any wrinkles, the radius
between stiffeners at Wing Station (WSTA) 150 (under fuel tank covers), and
unreinforced access holes;
Smoking rivets at the rib near the inboard aileron hinge (WSTA 162);
Missing fastener hardware, particularly for attachment of the tips;
Excessive looseness of attachments of the tip extension to the wing and wing tip to wing
extension when pushing up and down on the tip;
Any signs of distress along both front and rear spars, particularly in the area around
WSTA 177;
Unusual repairs to the upper skins, particularly in the area of WSTA 150-162, and
Inter-rivet buckling of the stringers attached to the upper surface skin, outboard of the fuel
tank access covers.

William O. Herderich, Aerospace Engineer, Atlanta Aircraft Certification Office, 1701 Columbia
Avenue, College Park, GA 30337; telephone: (404) 474-5547; fax: (404) 474-5605; email:
This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
Charles A. Emering, Principal Avionics Inspector, FAA Teterboro FSDO-25, Park 80 West, Plaza
One, 250 Pehle Avenue, Suite 003, Saddle Brook, NJ 07663; telephone (201) 556-6600 Ext. 263; fax:
(201) 556-6623; email: This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
For Related Service Information Contact
Aviation Enterprises, 4099 Brick Church Pk, Whites Creek, TN 37189; telephone: (615) 585-7765;
fax: (615) 865-9164; Internet:
Flint Aero Inc., Gillespie Field, 1942 Joe Crosson Drive, El Cajon, CA 92020; telephone: (619)
448-1551; fax: (619) 448-1571; Internet:
Cessna Aircraft Company, P.O. Box 7704, Wichita, Kansas 67277; telephone: (800) 423-7762 or
(316) 517-6056; Internet:

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