BY-122, BY-124 and after; BZ-1 and after
The King Air 250 is equipped with composite propeller blades. The propeller heat system heats the propeller blades anytime the Propeller Heat switch is in either AUTO or MANUAL position, whether in flight or on the ground. If the Propeller Heat system is left ON on the ground for just a few seconds without the engines running, severe damage to the propeller blades and boot will occur (see photo). There are CAUTION statements in the Pilot’s Operating Handbook Supplement and the Information for Continued Airworthiness for the propellers.
It is imperative that anyone turning ON the Battery Master Switch makes sure that the Propeller De-Ice switch is in the OFF position as part of the power on procedures. This practice will prevent inadvertently having the propeller heat ON anytime the engines are not running.
The propeller de-ice system can be tested for maintenance, but it is important that maintenance personnel do not exceed the 10 second limit.
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