Summary
We propose to adopt a new airworthiness directive (AD) for certain Hawker Beechcraft Corporation (type certificate previously held by Raytheon Aircraft Company) Models B300 and B300C airplanes. This proposed AD would require you to inspect the terminal board on the circuit card rack assembly to determine if the correct bus bar is installed. This proposed AD would also require you to replace the bus bar if necessary and inspect the left and right pitot heat annunciators for proper operation. This proposed AD results from reports of the left and right pitot heat annunciators not illuminating for an inoperative pitot heat condition. We are proposing 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.