AD 2010-05-10 75 FR 9753

We are adopting a new airworthiness directive (AD) for certain Hawker Beechcraft Corporation (type certificate previously held by Raytheon Aircraft Company) Models B300 and B300C airplanes. This AD requires you to inspect the terminal board on the circuit card rack assembly to determine if the correct bus bar is installed and replace if necessary. This AD also requires you to do an operational check of the left and right pitot heat annunciators for proper operation and take corrective action as necessary. This AD results from reports of the left and right pitot heat annunciators not illuminating for an inoperative pitot heat condition. We are issuing this AD to detect and correct installation of an incorrect bus bar, which could result in failure of the pitot heat annunciators to illuminate. This failure could lead to the pilot being unaware that moisture has frozen on the pitot tube(s) and cause erroneous flight instrument indication.