system study, analysis and touble shooting
Eight years ago, nearing the end of my flying career, I was finaly thaught how to study a "system" in an aircraft ...
1. Look at the main "power" part of the system : where is the power coming from, what are the normal and abnormal flowspaths of power (power could be electrical, hydraulic, pneumatic ... or even "manual")
2. Look at the controlling circuit(s) : how is the power activated, regulated, diverted, cancelled ...
3. Look at the indictors circuit(s)
4. Look at interaction with other systems ...
This is a very usefull way to simplify system diagrams! Just use 3 colors to "mark" the diagrams line and components ...
A good way do diagnose troubles ...
So quick in the Spannair RAT cause!
a) we have power ... so the power circuit is ok (there are no dedicated indicators, but we can feel the heat, use the aircraft ammeters, or a technician ammeter/voltmeter/ohmmeter standard tool).
b) So the problem must lies within the controlling circuit. What is the controlling circuit made off? That infamous relay!
Bingo!
c) How can we make sure ? See what other system are controlled by this relay ... So easy to test the TOWS ... Double Bingo!