HFD,
The place to go for info is the CAAIP - CAP562
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Mad Jock,
If something is U/S. The Avionics Engineer can a) Re-rack the box or b) Replace the box or in some cases swap the #1 and #2 boxes. Each of the options involves removing a box from the rack and putting a box back into the rack. Replacing unserviceable items is not dangerous. Re-racking done properly is a common standard maintenence procedure.
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unfazed,
Ask yourself - if the radios kept the cockpit nice and toasty why would they have installed a heater?
If you never use the heater for fear of Co I would recomend that you get yourself one of those Co detectors and watch out for a black dot while you and your equipment enjoy the heat.
You are correct about Co but hypothermia can be just as deadly!
Regards,
DFC