Page 20 - Volume 12, Number 3

night!) so usually just a few seconds elapse before the Normal grids join with the Ground Max.
I sometimes teach that the Ground Max heat grids are like the portable little electric heater you plug into the outlet to help the furnace heat that chilly winter bathroom. It has no tie-in whatsoever to the house thermostat or heating system but rather operates in a totally independent fashion. When you position the electric heat switch to GND MAX, it’s like you plugged in the portable heater ... it operates, period. But the Normal Grids are indeed tied into the environmental system and don’t waste energy until the heat of the bleed air – which must come into the cabin for pressurization anyway – is fully exploited.
The electric heat switch is held in the GND MAX position by an electromagnet that is only energized when the appropriate squat switch is activated ... weight on wheels. When we lift off at takeoff, this “independent” member of our heating system says good-bye. Even with mediocre bleed air flow, GND MAX will not be needed in flight.
And if you were to forcably hold the electric heat switch to the GND MAX position once airborne, then what? The answer, for you few trivia buffs, is that doing so will indeed cause the Ground Max grids to operate ... but the
Normal grids, if operating, will shut off! A landing gear uplock switch – not the Squat switch – prevents all eight grids from operating when the gear is retracted.
Remember when I mentioned the burning smell? That can be scary for the passengers so a trick I use is to burn off the lint and dirt periodically by running each heater element for a minute or so on a deadhead cruise leg. To do so, (1) make sure the Lock Out items are off, (2) position the mode selector to MAN HEAT, (3) place the electric heat switch to the
center, NORM position (or verify that it is already there), and (4) verify that the loadmeters jump up and the smell begins. After a minute or so, reach over and hold the heater switch up to GND MAX and keep it there for a minute or so to burn off the other grids. Now let go of the heater switch and return the mode selector to AUTO.
By the way, where should you leave the heater switch on warm days? NORM or OFF? It really makes no difference. Realize that in NORM the Normal heater grids never operate until the Bypass Valves get to the full-hot position. So, in this position the normal heater is just available to operate, not actually operating. On hotter days, it will never be requested by the automatic heating system.
ADF Tuning
What the heck does ADF Tuning have to do with heater operation?! Absolutely nothing!
I decided to use the remaining article space to throw in a little trick that you may not have been taught. This trick applies only to the Collins Pro Line II tuning heads, the ones that were the standard before Pro Line 21 came along around 2005. The ADF tuning control – like the COMM and NAV control heads – allow a frequency to be dialed into the bottom, Standby window and then it is flip-flopped with the active frequency by momentarily
tapping the little transfer switch up and releasing it.
But do you realize that these heads offer an active tuning option? By depressing the little white button just below the tuning knobs for two seconds or longer, the frequency in the Standby window is replaced with dashes and now the upper, active frequency is tuned directly.
Last week I was flying from Houston back to Phoenix on a Sun- day in LJ-1190, a sweet 1988 C90A with these types of avionics, and the NFL Conference playoff games
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