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“ ... it never hurts to double check these cold weather items to make sure they are ready to go when you really need them.”
while the other is in the cockpit operating the system and monitoring the gauges. Although recommended by the maintenance manual, I’ve seen this test fall short on many occasions.
I’ve also written articles regarding prop heat and problems with this test specifically. See “Prop Heat” in the February 2019 issue and “Heated Argument – More on Prop Heat” in the April 2019 issue [Volume 13, Numbers 2 and 4 respectively].
Testing your prop heat in flight requires a clear understanding of the type of system installed in your King Air and keeping a keen eye on your prop amp gauge.
FCU Heat: This tube located inside the engine cowl connected to the fuel control carries compressor discharge air (P3 air) which is super hot. This is the least crucial of the external heat items due to the extremely hot air running through it – freezing is highly unlikely. In fact, King Airs with 60-series PT6s (such as 300s, 350s and those with a 60-series Blackhawk mod) do not have FCU heat.
In 200s, the FCU heat comes on when the condition levers are moved forward. The same is true for later model 90s. Earlier 90 models have an FCU heat switch for each engine in the cockpit.
The only time a malfunction of FCU heat becomes an issue is in reverse or in an over-torque situation. FCU heat is checked at every Phase Inspection.
Battery Off
As a friendly reminder, after checking all these items, don’t forget to turn your battery off. It’s easy to overlook this when you are poking around your aircraft and not following a preflight or postflight checklist. After years of waking up at midnight and wondering if I left a battery
FEBRUARY 2024
switch on, I came up with a surefire remedy. When working on a King Air with a dual bus system, I leave the beacon switch in the “on” position. The flashing beacon is a constant reminder that the battery is on.
Try it yourself. As you get ready to leave the hangar and you look back at the aircraft on your way out the door, if that beacon is still going, you will happily turn your battery off and be thrilled you didn’t drain it dead. When I’m working on a King Air with a triple feed bus, I use the nav lights as my “battery reminder” since the beacon bus is not powered with the battery on. KA
Dean Benedict is a certified A&P, AI with 50 years of experience in King Air maintenance. He was an inaugural inductee to the King Air Hall of Fame. He’s the founder and former owner of Honest Air Inc., a “King Air maintenance boutique” (with a sprinkling of Dukes, Barons & Bonanzas). Currently, with BeechMedic LLC, Dean and his wife, Lisa, consult with King Air owners and operators on maintenance issues, troubleshooting and pre-buys. Dean performs Expert Witness work on request. He can be reached at dr.dean@beechmedic.com or 702-524- 4378.
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