As expected, the FAA has published an Airworthiness Directive for 800-series Hawkers equipped with Aviation Partners (API) winglets. The AD, to take effect July 2, calls for operators flying 800-series Hawkers with API winglets to comply with the API service bulletin SBH-13-001 issued in May by installing a placard in the cockpit and a page in the flight manual limitations section that limit maximum altitude to 34,000 feet.

According to the FAA, “This AD was prompted by reports of several instances of severe vibration and wing/aileron oscillations. We are issuing this AD to prevent vibration and wing/aileron oscillations, which could cause structural damage or lead to divergent flutter, and result in loss of integrity of the wing, loss of control of the airplane, and in-flight breakup.”

API COO Hank Thompson previously told AIN that the company has examined the oscillation problem using finite element modeling and developed a fix that involves rebalancing the Hawker’s ailerons. API planned to flight-test the solution, after which the fix will be available to operators so they can remove the 34,000-foot limitation.

The AD requires operators to install the placard and insert the page into the limitations section of the AFM within 45 days of the effective date. The AD does not apply to winglet-equipped Hawkers modified by Hawker Beechcraft or Beechcraft.