Originally Posted by
RandomPerson8008
Student pilot question:
If one were to experience an electrical failure(battery and alternator) in an R44, would you would lose (among other thing such as lights & radios):
(I understand that one should be forewarned of this by the alternator warning light, and that you would have at least 10-15 minutes before depleting the battery assuming some non-essential items were turned off)
1) Governor
2) Tachometers
3) Low RPM warning system
If you lose both battery AND alternator you will lose EVERY electrical system and device in the R44 (any variant) EXCEPT the magnetos. No governor. No tach's. No low RPM warning system. All gone except the mag's.
Studying the electrical diagram in the pilot's operating handbook, it appears that there is power for the Tachs and Low RPM warning system through the magnetos & clutch switch?
That is incorrect.
The electrical schematic that Robinson provides is almost worthless because it does not provide any detail of the circuitry or switching in a number of important components, most notably all relays. IMHO, as both a pilot and an electrical engineer, this is unforgivably stupid. You therefore have to infer how it all works from the rest of the POH, which you can do, but it's a PITA.
That said, the clutch, engine tach and rotor tach have two sources of power, which are combined on what is effectively an "essential systems bus", although it is not implemented as an actual bus. The electrons don't care, though! This is done in the clutch switch for the clutch, and by means of a diode isolator for the tach's. The two sources are the main bus via the master radio relay (in the version of the diagram--it sure as hell isn't an electrical schematic--which you posted) and a direct connection to the battery via contacts on the clutch switch which are closed when the clutch is activated (regardless of how poorly drawn the diagram is at the battery relay).
The design intent is that if you have an electrical fire in flight and perform the emergency procedure, which includes turning off both the battery and alternator switches, then you will still have the clutch and tach's remaining even when you do that because the battery will almost certainly last for the very few moments it takes to "land immediately". You will lose the governor and low rotor RPM warning system and that is explicitly noted in the POH emergency procedure. Obviously when certifying the helicopter it was judged a worthy trade-off to keep the clutch and tach's operating under these conditions. Certainly it is for the clutch.
Will these two systems remain powered with the loss of battery and alternator? I did not think the magnetos were capable of powering anything other than the spark plugs.
Again, those systems, and all other systems, will be gone if both battery and alternator are kaput. The mag's only run the ignition system, as you correctly surmise.
It appears that the rotor brake and rotor brake light continue with magneto/ignition system power as well?
No, those are fed power from the main bus via a circuit breaker, as is that connection to the clutch switch. Again, the Robinson diagrams are junk because they do not label inputs and outputs.
How about the clutch actuator? Diagram seems to show magneto power to it too. I can't imagine there would be sufficient power to move the clutch actuator without the battery or alternator.
Negative. See above.
Thanks in advance. Please go easy, I am a mere student pilot and my instructors rarely have time to answer my questions outside the helicopter.
You need to find some new instructors ASAP. Knowledge of aircraft systems is important, and they should be teaching you this. If they are not teaching you this, what else are they not teaching you? You don't know what you don't know!