Page 15 - Volume 13 Number 2

A prop lead that went bad and had passed the turn-by- hand test.
When this spring-loaded switch is toggled and held in place, the prop heat timer is bypassed. Now, the prop heat on both props runs simultaneously.
With the dual-segment systems, the Manual switch stays in the center position until you push it up and hold it to heat the inboard segments of both props; then toggle it down and hold it to heat the outboard segments of both props.
Unfortunately, whether you have single or dual- segment prop heat, the Manual Prop Deice bypasses the amp gauge, so you can’t rely on the gauge to verify that the manual mode is working. But if the ice slams go away, you’ll know the Manual switch did the trick (or you are no longer in icing conditions). Either way, you’ll be squawking prop heat when you get on the ground.
Summary
Ice slams are never a good thing. Either the prop heat was turned on too late, there’s a malfunction in the prop heat system, or you’ve gotten yourself into icing conditions so heavy that the system just can’t handle it.
Better to be safe than sorry. Test your prop heat on the next ground run. Keep your eye on that gauge and allow sufficient time for several cycles. Address low or zero cycles before flying into potential icing conditions.
If you report a low cycle to a shop and they come back with “unable to duplicate discrepancy” or tell you that your low cycle is “within limits,” you should tactfully suggest a closer look at those deice leads. Some mechanics don’t understand the extreme conditions endured by these leads. All they know is to turn the prop and feel the boots for heat.
Prop leads are the prime suspects if there’s a low cycle. Brush blocks can also be the culprit. Occasionally the prop timer goes bad; that will give you ice slams. Beyond that, you need a good mechanic to troubleshoot the problem to full conclusion. The idiosyncrasies of brush
FEBRUARY 2019
block installation and alignment and the vagaries of mechanical or electronic prop heat timers is what he or she is all about.
As for my pilot friend, following my advice he returned to the shop and had them do a pull test on each prop lead. Guess what? They found a bad one – a lead that passed the hand-turning test. The pilot decided to have all the prop leads replaced as a precautionary measure.
I propose a toast: Here’s to hot props in cold weather!
Fly safely. KA
Dean Benedict is a certified A&P, AI with nearly 45 years’ experience in King Air maintenance. He’s the founder and former owner of Honest Air Inc., a “King Air maintenance boutique” (with some Dukes and Barons on the side). In his new venture, BeechMedic LLC, Dean consults with King Air owners and operators on all things King Air related: maintenance, troubleshooting, pre-buys, etc. He can be reached at dr.dean@beechmedic.com or (702) 773-1800.
KING AIR MAGAZINE • 13