Page 29 - Dec 2022

for heat there is. The larger props on the 300-series take about 7 amps per blade.
I believe I am correct in stating that all four-blade King Air propellers use the Hot Prop system. With a single heating element per blade, it now sends current to one propeller for 90 seconds, then the other side for 90 seconds before it repeats. A complete heat cycle for the inner/ outer style requires two minutes: 30 seconds per section times four sections. The newer Hot Prop style requires three minutes: 90 seconds per side. But here’s the rub: Ice was shed from only one-half of the boot originally. Now it’s shed from the entire boot. It is my experience and opinion that the nose of the fuselage tends to exhibit more ice “dings” with the more modern system. Oh well, it’s simply a fact of life.
With their four-blade propellers, the later 200s (and all members
of the 300-series) replace the three-position inner/outer switch with a two-position switch labeled “Manual.” It is spring-loaded to remain in the down, off position and is held up by a finger of the pilot’s right hand for about a minute and a half when being used. The idea is to then wait until some prop vibration is felt and then hold it up again. Once again, current for the manual system is not displayed on the prop de-ice ammeter but the two loadmeters now show an easily observed 8% increase.
I’ll finish with an idea that is definitely not FAA-approved, yet I have it on good authority that it works like a charm. Got a big rubber band? If you use it to hold the Manual switch in the Up position – maybe hook it to a post light on the instrument panel – then the propeller de-ice system truly becomes an anti-ice system. No
90-second accumulation to fling against the nose! Of course, we are using twice the current that the auto system would use but I believe the two generators can handle it quite easily. KA
King Air expert Tom Clements has been flying and instructing in King Airs for over 50 years and is the author of “The King Air Book” and “The King Air Book II.” He is a Gold Seal CFI and has over 23,000 total hours with more than 15,000 in King Airs. For information on ordering his books, contact Tom direct at twcaz@msn.com. Tom is actively mentoring the instructors at King Air Academy in Phoenix.
If you have a question you’d like Tom to answer, please send it to Editor Kim Blonigen at editor@blonigen.net.
DECEMBER 2022
KING AIR MAGAZINE • 27