The FAA has published a Special Airworthiness Information Bulletin on Honeywell (King) GPS units, including the KLN94 and KLN90B commonly installed in Beech airplanes.

This Special Airworthiness Information Bulletin advises you of an airworthiness concern regarding a missed GPS Non-Precision Approach (NPA), which may be caused by the Honeywell GPS sensor when no backup navigation system is available on flights greater than 5 hours. The FAA recommends that the pilot assure that he/she is prepared to revert to an alternative means of navigation appropriate to the flight if the above situation occurs. At this time, the FAA has determined that this airworthiness concern is not an unsafe condition that would warrant airworthiness directive (AD) action.

For more information read the SAIB.