Page 27 - March 2023

statement that, on first reading, makes no sense: “For takeoff, Generator Load must not exceed 30% with air conditioning on, nor 50% with air conditioning off.” Since the condenser blower operates whenever AC is operating with the nose gear extended, and since this blower uses about 50 amps, it seems that the generator load would be higher, not lower, with AC on. Right? Yes, that is correct ... but it’s not what the restriction is addressing.
The engine is subject to three things that can cause available takeoff power to be less than optimal even though the engine itself is fine: (1) Cowling inefficiencies, caused by ice vane deployment; (2) Compressor shaft load or drag caused by the need to drive the AC’s compressor (on the right engine); and (3) Compressor shaft load caused by generator load (on both engines). If we have little electrical load – no electric heater or windshield heat in use – then we can abide the AC drag and still have sufficient power available to the propeller to meet takeoff power design criteria. However, if the generators are working their guts out, then we don’t have enough “leftover” power to load up the compressor with the AC’s compressor drag.
To summarize then, the 300’s requirement to not use engine anti-ice for takeoff when OAT is above +10°C is based not on oil cooling concerns but instead is based on eliminating the cowling inefficiencies that could lead to inability to meet the Minimum Takeoff Power target torque.
For all of the other King Air models – 90-series, 100-series – you, like the 300-series, have no tie- in between ice vane deployment and oil cooling. If you have a three-blade propeller, especially if it’s combined with the original “Chin” style of cowling, there is no concern about FOD due to ground debris even with the ice vanes retracted. On the other hand, four blade props combined with the pitot cowl – F90-1s, C90As and after – have
enough FOD potential that engine anti-ice ON while on the ground is strongly recommended.
But consider this: Leaving the ice vanes up on a four-blade 200 or any member of the 300-series is asking for FOD ... leading to a very expensive repair. But having the ice vanes down on your B90 causes no problems whatsoever. If you, like many pilots, fly a variety of King Air models, then there is absolutely nothing wrong with making “Ice Vanes down for all Ground Ops” your SOP (Standard Operating Practice). Are ITTs affected? Is engine starting affected? No! The only negative associated with this procedure is forgetting to retract them when taking the runway and hence not being able to attain your target minimum takeoff power.
I’ll leave you with this thought, readers: Forgetting to retract the ice vanes for takeoff may not be as bad as you think it is. Why? Because the ram air loss at takeoff speed –
100 knots? – is a whole lot less than what you are used to seeing when you pull those ice vane handles out (or activate the switches) before entering that cloud deck below you while in a descent doing 200+ knots. You dig? Groovy, man! 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.
Main wheel & brake/ Rodas e freios principais
Kit P/N 199-90
Together, we can support all your King Air braking needs, one landing at a time.
Juntos podemos apoiar todas as suas necessidades de freio King Air, um pouso de cada vez.
The following King Air 90 models are now certified under European approval EASA #10039114 and Brazilian approval ANAC #9210-04:
Os seguintes modelos King Air 90 são agora certificados sob aprovação europeia EASA No10039114 e aprovação brasileira ANAC No9210-04:
• 65-90 • B90 • C90-1 • C90B • C90GTi • 65-A90 • C90 • C90A • C90GT • C90GTx
1-800-BRAKING (1-800-272-5464) Visit our website to see our full list of King Air conversion kits and more
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MARCH 2023
KING AIR MAGAZINE • 25