Following a rash of reports of incorrect altitude and airspeed indications by Avidyne Entegra EXP5000 primary flight displays, the FAA yesterday issued an Airworthiness Directive requiring the addition of cockpit placards and aircraft flight manual/pilot operating handbook operating limitations until affected displays can be repaired. The AD–which affects King Airs fitted with the Alliant cockpit retrofit, Piper Meridians and several other models–identifies by serial number 487 affected PFDs that are known to have been sent to the Avidyne service center in Melbourne, Fla., for air-data system upgrades and other maintenance between November and February. The FAA said Avidyne has traced the airspeed and altitude errors to a manufacturing defect with an air-data unit assembly but so far has been unable to determine the root cause. Once it does, repairs will be made under warranty, according to an Avidyne statement. In the meantime, IFR flight with any PFD that is exhibiting the errors is prohibited starting on the AD’s effective date of April 10. According to the FAA, these errors “could result in airspeed/altitude mismanagement or spatial disorientation of the pilot with consequent loss of airplane control, inadequate traffic separation or controlled flight into terrain.”