Less than four months later, the FAA notified the general aviation community of plans to issue an airworthiness directive calling for inspections of Grumman American-family AA–5 and AA–1 aircraft to address potential separation of upper and lower skin surfaces of horizontal stabilizers.
Two months later—extremely fast by the usual timelines—AD 2021-14-12, covering an estimated 1,113 airplanes, took effect as the FAA dispensed with customary notice and public comment procedures in accordance with steps it can take “upon a finding of good cause.”
Airworthiness directives are legally enforceable FAA regulations issued “to correct an unsafe condition in a product.” Some ADs require only inspections of suspect components and on-condition repairs of any found defective, while others mandate a fix, a part replacement, placard, or other remedy immediately or within a prescribed amount of time. An aircraft not in compliance with an AD may not be legally airworthy, and actions taken to comply or determine an AD’s applicability to a particular aircraft should be recorded in the aircraft’s maintenance records. You can check for ADs applicable to aircraft you fly on the FAA website (faa.gov/regulations_policies/airworthiness_directives).
The “good cause” the FAA cited was easy to spot by a pilot flying an aircraft off the right wing of the accident airplane, an American AA–5. The pilot advised the occupants of the stricken aircraft that its elevator was “flapping in the wind.”
The flight instructor aboard the AA–5 had already taken over flying from the student pilot after they had felt the “large shock,” and was struggling to maintain control as the airplane pitched and rolled and the control column shook violently.
Thinking that there had been an engine malfunction, the instructor “applied carburetor heat, reduced the throttle to idle, and slowed to the airplane’s best glide speed, which was 80 mph, and executed the engine failure checklist from memory. He circled left looking for a suitable field in which to perform an emergency landing and declared a mayday three times to the air traffic control tower” in Leesburg.
“Both occupants identified several possible landing spots,” but after receiving the report from the airborne observer (who now became a chase airplane for the AA–5) he added power and flew to a landing in Leesburg. On landing, the nose pitched down and struck the runway, according to the NTSB’s preliminary report.
A post-accident examination revealed that “the left elevator was partially separated, with the outboard portion of it well below the position of the horizontal stabilizer.”
The FAA determined that “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 instances of similar corrosion surfaced from subsequent field reports, raising concerns for models with similar stabilizer designs and the same elevator attachment methods. The FAA concluded from the field reports that it would take more thorough inspections to “reliably identify corrosion and delamination of bondlines in these critical areas” and make any needed fixes. Making that finding legally enforceable called for an AD.
The several compliance timelines permitted for the horizontal stabilizer inspections were shorter than the amount of time needed to seek public comment on a proposed AD and publish a final rule in the Federal Register, so the FAA deemed the usual procedure “impractical” and proceeded to implement the AD on a fast track.