This morning I was doing a short IFR hop to Hannover EDDV when alternator 1 stopped charging. The SR22 has tow batteries, two alternators and the busses are called main and essential.
I did advise ATC asking for expedited landing. The weather was supposed to be BKN012 but clouds were a bit lower than that.
At about 10V on battery 1 (main bus) the autopilot, transponder and also the radios stopped working. GPS was gone too but the receivers for NAV continued to function.
While I was on the localizer inbound 09L I was picking up ice at -2C. ATC had cleared me already down to 2000’ for the short way to the localizer.
As my radio was out but I was aligned with the runway I continued and landed without any further trouble. The firefighters had their lights on but kept their vehicles stationary. I was greeted by a follow-me that arrived a bit late. My radio came back to life and was able to talk to ground.
After I parked a guy from the fire fighters wanted me to sign a form and the guy from “Luftaufsicht” (government) started to asked questions about the ice and the presumed VFR flight. I responded “IFR flight” and he went away :-)
I’m on the phone. Maybe I write a bit more later today. Main takeaway is: below 10V the electric plane gets interesting.
What seems completely mad:
- what is the second alternator here for ? Dead weight ? :-)
- why the essential bus doesn’t keep one radio and one gps alive ? Seems odd to me
This is quite a confidence biting event about redundancy.
PS: What about your turbocharger ?
PetitCessnaVoyageur wrote:
What seems completely mad:
I agree. Either something is very wrong with some component in there, or the setup is flawed by design. If there is something wrong with one system, there should be a way to turn it off.
That sounds like you are lucky to have landed so relatively “uneventful”, could have come out worse.
My takeaway from my IR training is that an ALT1 failure in IMC in a Cirrus with the old (Avidyne) electrical system is always an emergency situation. In VMC it is “Land as soon as practical”. You need to do some serious load shedding as per the checklist, with some things that I really wouldn’t want to miss in real IMC (like the de-ice system or MFD).
In the “new” (Perspective) Cirrus, it is more or less a non-event. We had discussed this topic here before:
http://www.euroga.org/forums/maintenance-avionics/5262-sr22-g2-2206-alt-1-failure?page=6#post_92410
One good recommendation that I got in training was to study the electrical system in order to know what is connected to which bus. There is a good online course from Cirrus (it costs a few bucks, I think $80), but I have only seen the one for the Perspective. But there are also free training videos like these.
Non-Perspective:
Perspective:
Difficult to say without knowing which “generation”. I suspect G2. The Cirrus electrical system started out as a simple emergency alternator and backup battery. Even in the G3/G5 perspective, the layout shows this heritage (especially the unusual BAT2 power routing), but is of almost no consequence.
Simplified description
If you lose ALT1, the BAT1 starts to drain, and after some time you are down to NAV/COM1 and the PFD. If you lose ALT2 you lose nothing, ALT1 just powers all busses, and is powerful enough to do that.
The G3/G5 is similar in general lay-out, but with a completely different outcome
so if you lose ALT1 and drain BAT1 in a G3 perspective or later, you only use the yaw damper, airconditioning and landing light, nothing else. If you lose ALT2 you lose nothing.
Posts crossed. I really like the videos – nice and practical, and a lot better than the awful POH diagrams.
They miss one point, though – the BAT2 is NOT connected to the essential dist bus as shown, it is connected to the essential bus which is connected to the essential dist bus, which means there are TWO circuit breakers between these. But that would only be relevant in exotic circumstances.
Coming back to the case, what bothers me is that immediately you had to explain yourself to a government official as to why you did what you did (instead of being asked if you are OK and if they can help you somehow). I suppose in some countries you would even be charged for the fire fighters lights and ready state as well.
Such attitude makes safety decisions mentally more difficult because the thought that you have to explain and write a lot of paper is always in the back of your mind. Once I made a go-around at Donaueschingen EDTD and I was immediately (during the go-around run) asked by the tower in an unpleasant and impolite voice “Why did you make a go-around?”. Well, because I am a pilot and my approach was not safe enough.
I notice how this involuntarily creeps in my head when approaching a big airport like Zurich where a go-around of a small Piper might cause issues for airliners. I try to fight it on a conscious level and tell myself that safety is more important then a go-around of an A320 but still it’s an unpleasant feeling for me.
Vladimir wrote:
Once I made a go-around at Donaueschingen EDTD and I was immediately (during the go-around run) asked by the tower in an unpleasant and impolite voice “Why did you make a go-around?”.
I think I can guess what happened there. EDTD gets a lot of IFR training traffic from Switzerland, which usually involves multiple low approaches. If you have planned multiple approaches, the controllers want to know in advance that you are coming so they can fit you in, or tell you to go elsewhere if there are already too many others doing the same thing. So here maybe the tower controller falsely assumed you had come to do practice approaches without saying so. But of course in a professional environment like the USA, I don’t think you would get such a reaction, so you are right to be put off. It’s important to remember that controllers are humans too and try to explain yourself in a neutral voice whenever it’s briefly possible. But you are right – since they have the privilege of sitting in a warm and comfy chair on the ground and I am in the air, I will always tell them what I need if it’s really necessary – like you probably did on that occasion too.
These officials are there to enforce the rules, and it doesn’t seem that they overstepped their competences here. So on this occasion, I don’t really see a problem with their behaviour.
Coming back to the electrical failure, I find it weird that the autopilot stopped working, since it is fed from the essential bus on your plane. COM1 as well, I wonder if the fact that the audio panel is fed from the Main distribution bus 1 played a role there – but then it wouldn’t make sense to have COM1 but not be able to use it without the audio panel. @Stephan_Schwab Do you regularly check during pre-flight that the flap position light is out when you switch on just BAT1?
I found one more interesting presentation on the non-Perspective electrical system: http://slidegur.com/doc/3321097/avidyne-sr-22electrical-system
Cobalt wrote:
They miss one point, though – the BAT2 is NOT connected to the essential dist bus as shown, it is connected to the essential bus which is connected to the essential dist bus, which means there are TWO circuit breakers between these.
You are right. Here is the correct diagram for the Perspective plane: http://sierraskyport.com/wp-content/uploads/2015/06/ElectricalSR22.pdf
Rwy20 wrote:
EDTD gets a lot of IFR training traffic from Switzerland, which usually involves multiple low approaches.
I was the only airplane in the circuit and on the frequency, flying VFR and had declared I was going to make a full stop. EDTD has information only, so he didn’t even have to take care of traffic or clearances. I just told him “Approach was not stable” and didn’t comment any more.
PetitCessnaVoyageur wrote:
PS: What about your turbocharger ?
It got replaced by a new one. Spanish mechanic at Sabadell LELL did a very good job including applying mouse milk to all the important bits of the exhaust.
