Page 22 - Nov23

ASK THE EXPERT
Cold Weather Ground Operations
by Tom Clements
It won’t be long before Old Man Winter is holding much of the country in his icy grasp, so it’s an appropriate time to review how to warm up the cabin most effectively after engine start. Operators of the King Air model 90, A90 and B90 have only two choices: Either select auto or manual heat on the Cabin Temp Mode rotary selector switch. If your auto mode works well, you will probably use that position. If it is rather unreliable – and that is quite common in these older birds – then “man heat” is the position to select. In either case, the combustion heater should activate and turn a minor amount of kerosene into a major amount of cabin heat, pronto!
The vast majority of King Airs now use bleed air as their source of incoming cabin air – eliminating the supercharger that is found on 90s, A90s and B90s – and supplement this source of heated air with an electric heater of some type. Let’s discuss the options.
There are still pilots who are somewhat lazy in their approach to bleed air ... leaving the left and right switches on at all times, summer and winter, including during startup and shutdown. I am happy that this lazy technique
20 • KING AIR MAGAZINE
is disappearing and being replaced with a much more correct and scientific approach. It has been found that bleed air flow control packages (flow packs) tend to experience some oil mist contamination when they are on at startup and shutdown. This is because the labyrinth-style bearing seals in PT6 engines do not seal well until the engine is running and producing internal air pressure; so now most King Air pilots are turning off the flow packs before shutdown and not turning them on until the next start is completed.
NOVEMBER 2023