DA 42 electrical circuit structure / redundancy
Posted: Mon Apr 27, 2020 10:38 am
Hello,
I find the DA 42 electrical system relatively poorly explained in the POH, the diamond training handouts and by the instructor.
In particular, no explanations are given about the failure modes, the redundancy etc.
Given the reliance of the engines on electrical power, I find this particularly important.
Some of the questions I ask myself :
- You have two main bus (LH and RH), both connected to the battery bus via breakers
* what is the point of the LH/RH BUS design ?
* having both LH/RH voltage indications on the G1000 is thus most of the time useless as they are physically connected. You would have a different reading only if a circuit breaker pops. Correct ?
* What level of protection the breakers between busses provide ? Do you have a possible scenario where a short on the RH bus kills it, but thanks to the breaker the LH BUS would remain good ?
* would it be desirable in some situations to voluntarily split the system by pulling a breaker ? (probably not as it is not in the checklists...)
- The red electric master control switch commands three key relays :
* Battery to battery bus
* LH alternator connection to LH BUS
* RH alternator connection to RH BUS
Thus it looks as a single point of failure. But is it ? is there any likelihood of such a switch failing ?
- Has there ever been a total electrical failure on a DA42 ? (leaving aside the crash of the plane which took off with an empty battery and which led to the ECU backup batteries introduction)
Thanks a lot for your answers !
I find the DA 42 electrical system relatively poorly explained in the POH, the diamond training handouts and by the instructor.
In particular, no explanations are given about the failure modes, the redundancy etc.
Given the reliance of the engines on electrical power, I find this particularly important.
Some of the questions I ask myself :
- You have two main bus (LH and RH), both connected to the battery bus via breakers
* what is the point of the LH/RH BUS design ?
* having both LH/RH voltage indications on the G1000 is thus most of the time useless as they are physically connected. You would have a different reading only if a circuit breaker pops. Correct ?
* What level of protection the breakers between busses provide ? Do you have a possible scenario where a short on the RH bus kills it, but thanks to the breaker the LH BUS would remain good ?
* would it be desirable in some situations to voluntarily split the system by pulling a breaker ? (probably not as it is not in the checklists...)
- The red electric master control switch commands three key relays :
* Battery to battery bus
* LH alternator connection to LH BUS
* RH alternator connection to RH BUS
Thus it looks as a single point of failure. But is it ? is there any likelihood of such a switch failing ?
- Has there ever been a total electrical failure on a DA42 ? (leaving aside the crash of the plane which took off with an empty battery and which led to the ECU backup batteries introduction)
Thanks a lot for your answers !