Electronics design error
Hello all,
As an experienced electronics engineer I have to say the there are many electronics design errors when interfacing modern digital electronics, especially with the digital inputs.
Typically a digital input (ON/OFF) input is implemented by using a pull-up resistor and a grounding switch (or a pull-down resistor with a switch to voltage).
I believe that A350 engine control digital inputs have too high impedance. The control inputs should not change the state with coffee or other liquid spilled on/in the the switches. This applies to all reliable electronics design.
Moisture or any liquid stuff can cause leakage current between any terminals. But if the design is robust (ie impedance is low enough) there is no effect in the ON/OF state because a possible leakage current is minimal compared to the intended ON/OFF signal. If a pull-up design is used the pull-up resistor value should be low enough to win a possible leakage current caused by some liquid.
Furthermore, all the input circuitry, switches etc should be tested with high humidity and with possible liquid spill.
I hope Airbus engineers, and all other manufacturers are reading this, because this is extremely critical and it can't be solved with software!
Best Regards,
A concerned electronics engineer/private pilot in Finland