With regard to the DME. Pilots should keep the DME off when they do not require it i.e. in the circuit. The reason is that DME stations have a capacity limit and when that limit is reached they stop stations at the greatest distance (affected by power) from obtaining information. This means that while you blast round the circuit with the DME blazing out the distance from some VOR/DME, the poor sod at the limit of the range may not get a DME indication when they need it because you are.
When it comes to drying out the avionics - turn up the heater! Many avionics faults are fixed by re-racking the equipment - moisture on the contacts. Turning up the heat or taking the aircraft to a better climate will help the avionics even when switched off.
Now to the biggest load of cobblers.
Could the person who thinks that the compass will only read correctly when the pitot heat and every bit of electrical equipment is on please tell me how they can tell what direction the aircraft is pointing after an in-flight electrical failure?
The Airworthiness procedures require that -
The most adverse combinations of electrical loads must not cause deviation in
excess of 2° (5° for light aircraft).
When completing a compass swing, electrical equipment, e.g. radio, instruments and pitot tube heaters, should be
switched on
to ascertain that there are no adverse effects on the compass.
Thus having the pitot heat on or off will have little effect. Since most light aircraft pitot heats are powered by DC then even having the cable passing by the compass, there would be no change in effect by having the switch on or off.
Do those pilots who require the pitot heat to be on so that the compass is reliable ensure that the instrument pannel light in the compass is also on and serviceable?
Next time someone trotts out that kind of rubbish, ask them if they had 4 dummies wearing david clarkes in the C172 so that the efects of 8 magnets waving round the cabin was checked during the compass swing!
Regards,
DFC