Aircraft
Certification Service Washington, DC U.S. Department of Transportation Federal Aviation Administration
AIR-22-15
June 15, 2022
This is information only. Recommendations
aren’t mandatory.
Introduction
This Special Airworthiness Information Bulletin advises owners,
operators, maintenance technicians, and inspectors of an airworthiness
concern on True Flight Holdings, LLC (True Flight) Model AA-1, AA-1A,
AA-1B, AA-1C, AA-5, AA-5A, and AA-5B airplanes, specifically the
importance of inspecting the bondlines on the airplane, including the
bondlines on the wings and aft fuselage.
At this time, the FAA has determined that the airworthiness concern is
not an unsafe condition that would warrant airworthiness directive (AD)
action under Title 14 of the Code of Federal Regulations (14 CFR) part
39.
Background
Following an accident involving a True Flight Model AA-5 airplane in
January 2021, the FAA issued AD 2021-14-12 on July 12, 2021, which
applies to Model AA-1, AA-1A, AA-1B, AA-1C, and AA-5 airplanes. AD
2021-14-12 requires a one-time inspection for bondline corrosion and
delamination of the horizontal stabilizer, including the attachment
point of the elevator. The accident airplane’s elevator partially
separated from its attachment to the horizontal stabilizer, which
resulted in flutter of the elevator and near loss of pitch control.
This airplane was later found to have severe bondline corrosion and
delamination in certain areas, including the outboard rib of the
horizontal stabilizer and the trailing edges of the elevator trim tabs.
The damage can readily be seen in Figure 1, below.
The FAA has received reports of other True Flight model airplanes
(those referenced in the Introduction section), which share similar
bonded construction, exhibiting damage similar to the accident
airplane. Although AD 2021-14-12 requires inspections of the area
attributed to the accident, all bonded structures should be inspected.
Bonding of structure requires strict controls to ensure a secure bond;
and while this bond should remain secure for a long time, as airplanes
age and are exposed to the environment, there is the possibility of
weakening of and damage to this bond. If the structure is compromised,
the airframe may not be able to support the required operational loads.
Because of this, it is critical to regularly inspect the bondlines of
the entire airplane.
Inspection of bondlines is specified in the model specific maintenance
manuals at annual or 100-hour inspections. Details can be found in the
“Servicing” chapter for AA-1, AA-1A, AA-1B models, or the “Time Limits
– Maintenance Checks” chapter for the Model AA-1C, AA-5, AA-5A, and
AA-5B airplanes. At a minimum, the instructions specify, “Inspect
bondlines for any indication of damage, peeling or cracks.” Further
details are provided in the following subsections titled, “Bondline
Damage, Inspection Procedures and Repair.”
True Flight Aerospace, LLC introduced Service Bulletin SB-195, Revision
A, dated June 1, 2021, (SB-195A) to address this bondline delamination
issue. SB-195A specifies enhanced inspection instructions that cover
the whole airplane structure at every annual inspection. The
instructions cover inspection of whole airplane bondlines for
delamination and interiors of surfaces for corrosion, corrosion
treatment, and reference to bondline and corrosion repair instructions
as needed. While SB-195A is not mandatory, the FAA believes the
inspection methodology is beneficial to aid the airplane owner or
maintenance personnel in detecting the issues described herein.
Skin delaminations are typically found on trailing edges of control
surfaces, but can occur along the flanges of wing or stabilizer spars,
other externally accessible bondlines, and can also occur along
less-obvious internal bondlines. Close attention should be paid to
obvious joint separation, corrosion along edges, hairline cracks in
joints, and a bulging surface along an internal bondline (such as a rib
not being visible on the outside of the skin). All potential
indications of bondline damage should be further investigated in
accordance to the model specific service information. This would
typically involve a basic tap test with a coin along the area in
question, listening for a hollow sound, or a more advanced tap hammer
device. If there is any doubt or the area cannot definitively be
cleared an internal inspection should be performed.
Please note that this SAIB is unrelated to a previously addressed issue
with the FM-123 bonding agent, commonly known among owners as “Purple
Passion”, used in production of certain airplanes. Inspection of bonded
structure is critical regardless of the materials used, and is
especially so as age and environmental factors tend to degrade the
integrity of the structure over time.
Recommendations
The FAA recommends that the actions outlined in the affected airplanes’
maintenance manual, as well as SB-195A, be followed at the earliest
opportunity and at the annual or 100-hour inspections.
For Further Information Contact
Fred Caplan, Aviation Safety Engineer, Atlanta ACO Branch, FAA, 1701
Columbia Avenue, College Park, GA 30337; phone: (404) 474-5507; email:
frederick.n.caplan@faa.gov.
For Related Service Information Contact
True Flight Aerospace, LLC, 2300 Madison Highway, Valdosta, GA 31601;
phone: (229) 242-6337; email: Info@TrueFlightAerospace.com.