Page 14 - Volume 13 Number 2

So, even though the prop brush blocks looked like they had some time left in them, they wore down much faster after the prop was overhauled.
Ultimately, I reversed my earlier practice and installed new prop brush blocks whenever props came back from overhaul. I then noticed that new brush blocks together with fresh slip rings often lasted the full six years between prop overhauls (depending on hours flown, of course).
Regarding the problem of the pilot who called me, I remembered that his props had been overhauled recently. So, in addition to checking the prop leads carefully, I suggested he have the shop check the brush blocks and verify good contact with the slip rings. Brush blocks that are on their way out can create intermittent prop heat performance. When they wear out completely, they make zero contact and you get a zero cycle.
When the spring-loaded Manual switch is toggled and held in place, the prop heat timer is bypassed and the prop heat runs on both props simultaneously.
Manual Prop Deice
Let’s say you are mid-flight, you get some prop ice slinging against the nose so you check your amp gauge and find a zero cycle. It could be a brush block issue, or it could be a problem with the prop heat timer. That is the time to use the Manual mode.
12 • KING AIR MAGAZINE
FEBRUARY 2019