DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2021-1017; Product Identifier AD-2021-00495-A]
Airworthiness Directives; True Flight Holdings LLC Airplanes
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Proposed rule; withdrawal.
SUMMARY: The FAA is withdrawing a notice of proposed rulemaking
that proposed to adopt a new airworthiness directive (AD) for all True
Flight Holdings LLC Model AA-1, AA-1A, AA-1B, AA-1C, AA-5, AA-5A, and
AA-5B airplanes. The NPRM was prompted by the report of an accident of
an airplane with bondline corrosion and delamination of the horizontal
stabilizers. The NPRM proposed to require inspecting the wings,
fuselage, and stabilizers for bondline separation, corrosion, and previous
repair. The NPRM also proposed to require repairing or replacing parts
and applying corrosion inhibitor as necessary. Since issuance of the
NPRM, the FAA has determined that there is not an unsafe condition, but
instead incorrectly followed maintenance procedures. Accordingly, the
NPRM is withdrawn.
DATES: As of April 14, 2022, the proposed rule, which published
Federal Register on December 1, 2021 (86 FR 68171), is withdrawn.
Examining the AD Docket
You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-1017; or in person at
Docket Operations between 9 a.m. and 5 p.m., Monday through Friday,
except Federal holidays. The AD docket contains this AD action, any
comments received, and other information. The street address for Docket
Operations is U.S. Department of Transportation, Docket Operations, M-
30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue
SE, Washington, DC 20590.
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: email@example.com.
The FAA issued AD 2021-14-12, Amendment 39-21639 (86 FR 36491, July
12, 2021) (AD 2021-14-12), for True Flight Holdings LLC Model AA-1, AA-
1A, AA-1B, AA-1C, and AA-5 airplanes. AD 2021-14-12 was prompted by an
accident involving a Model AA-5 airplane that occurred on January 19,
2021. During flight, the outboard elevator attach bracket on the
horizontal stabilizer detached, causing loss of elevator control and
significant damage to the airplane. An investigation identified
corrosion and delamination of the airplane skin bondlines around the
area of the horizontal stabilizer where the elevator attach bracket was
attached. Multiple field reports identified additional instances of
corrosion and delamination of skin bondlines around the horizontal
stabilizer and other primary structures.
AD 2021-14-12 stated that Model AA-1, AA-1A, AA-1B, AA-1C, and AA-5
airplanes have horizontal stabilizers that are similar in design and
use the same metal-to-metal bonding process. While the bond adhesive
remains structurally sound throughout the aging process, factors such
as corrosion and freezing moisture may compromise the structural
integrity of some of the bond joints. This can lead to delamination of
the skin from the primary structure. The FAA determined that a more
thorough inspection was necessary to reliably identify corrosion and
delamination of bondlines in these critical areas, including the
horizontal stabilizer. As a result, AD 2021-14-12 requires a one-time
inspection of the horizontal stabilizers, paying particular attention
to the bondlines, for cracks, buckles, corrosion, delamination, rust,
or previous repair.
The FAA issued an NPRM that proposed to amend 14 CFR part 39 by
adding an AD for all True Flight Holdings LLC Model AA-1, AA-1A, AA-1B,
AA-1C, AA-5, AA-5A, and AA-5B airplanes. The NPRM published in the
Federal Register on December 1, 2021 (86 FR 68171). In the NPRM, the
FAA proposed to require a repetitive inspection of the wings,
stabilizers, and aft fuselage for bondline separation, corrosion, and
previous repair. While AD 2021-14-12 requires only inspecting the
bondlines on the horizontal stabilizers, in the NPRM, the FAA proposed
to require inspecting all of the bondlines on the airplane, including
the bondlines on the wings and aft fuselage. In the NPRM, the FAA also
proposed to add Model AA-5A and AA-5B airplanes to the applicability
due to the similar bonded construction of all models.
The original decision to pursue corrective action was based upon
multiple field reports, including direct observation of two airplanes,
of issues related to inspection of bonded structure. The first was the
originating accident airplane, and the second was another same model
airplane located in the same hangar as the first airplane. Both of
these airplanes exhibited damage (bondline delamination) in an area
believed to be the source of the accident, at the attachment of the
elevator bearing to the horizontal stabilizer. The construction in this
area is similar among the applicable models in AD 2021-14-12. The issue
specific to this area was addressed in AD 2021-14-12.
The FAA proposed the NPRM to address inspection for bondline
delamination on the entire airplane based on an understanding that
standard maintenance actions were insufficient to detect an issue.
Because more models than those covered by AD 2021-14-12 share a similar
bonded construction for the airplane as a whole, the NPRM proposed to
also apply to True Flight Holdings LLC Model AA-5A and AA-5B airplanes.
The FAA received comments from 41 commenters. The commenters were
the Aircraft Owners and Pilots Association (AOPA), the Grumman Owners
Pilots Association (GOPA), Fortnight Aviation Maintenance, and many
individual airplane owners and pilots.
All commenters opposed the NPRM. Most commenters stated that the
actions proposed in the NPRM are already addressed by existing
maintenance practices or included in maintenance documents such as the
Grumman maintenance manual, the annual inspection checklist, service
bulletins, and AD 2021-14-12. The commenters noted that the January
2021 accident resulted from poor maintenance practices and failure to
adequately follow these existing procedures, not from any fault with
the procedures themselves. For this reason, some commenters requested
the FAA withdraw the NPRM due to lack of supporting data and issue a
special airworthiness information bulletin (SAIB) instead.
Several commenters requested that the FAA remove Model AA-5, AA-5A,
and AA-5B airplanes from the applicability because these models have a
different design than the accident airplane. Many commenters noted that
the proposed AD is overly broad because the delamination issue is
limited to pre-1977 models manufactured with a ``purple glue'' for
adhesive. AOPA, GOPA, and a few individuals stated the proposed
requirement to tap test all bondlines on the airplane annually would
damage the paint and lead to corrosion. Lastly, AOPA, GOPA, and two
individuals requested the FAA increase its estimated labor rate of $85
The FAA agrees that the instructions in the airplane maintenance
manual are sufficient to detect the type of damage that is believed to
have led to the originating accident, as well as similar damage on the
rest of the airplane. The FAA further agrees that the original findings
were not indicative of an unsafe condition, but instead indicative of
incorrectly followed maintenance procedures. Based on this assessment,
the proposed inspection in the NPRM would exceed what is sufficient to
detect the main issue of bondline delamination. The FAA has determined
that additional AD action is not warranted and the proposal should be
The FAA acknowledges the comments unrelated to whether there is an
unsafe condition. However, because the FAA is withdrawing the NPRM,
those commenters' requests are no longer necessary.
Withdrawal of the NPRM constitutes only such action and does not
preclude the FAA from further rulemaking on this issue, nor does it
commit the FAA to any course of action in the future.
Since this action only withdraws an NPRM, it is neither a proposed
AD nor a final rule. This action, therefore, is not covered under
Executive Order 12866 or the Regulatory Flexibility Act.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Safety.