I was looking at a Cirrus SR20 the other day, it has a Continental IO360, the standby generator is driven from the usual vacuum pump take-off (rear of starter motor), the main generator is driven by a specially mounted pulley attached behind the propeller instead of below the mags. The whole installation looks very neat.
What kind of "user interface" (if any) does the installation have?
All these vac pump ones seem to do only about 20A which, while plenty to drive most avionics, probably can't drive the pitot heat at the same time.
Was it a factory install or a later mod?
Peter, I only had a cursory look at the Cirrus but from what I saw it was the original fit, I don't know how the standby generator is to be used but I would suggest as the primary instruments are 2 'television' screens it would sufficient to drive these for a while. Perhaps a Cirrus driver could tell us how long they've got before they have to land after a battery failure. Having removed the cowling I was impressed by the neatness of the engine bay compared to that of say a Turbo Arrow.
I'm in the early stages of approving exactly that product on my Norwegian client's modified 182. I am getting varying answers from Transport Canada as to the certification expectations. I will be going for an EASA STC on the installation after that. I also have a DA-40 client for the same mod. I'll keep the Euro GA group informed.
I did install and operate the earlier version of this on a Cessna 207, and was very pleased with the product. It's even better now. Bill and TJ at B&C are delightful, and endlessly helpful to get along with.
Pilot DAR - I would guess that to fit this 'standby' alternator to an existing aircraft would probably come into the realms of a major mode (well certainly in EASA land). Do you know if the switch to 'standby' is automatic on failure of the main generator or does it have to be pilot 'induced'. I suppose on a Continental you could fit the standby to the pulley mechanism behind the prop as per the Cirrus and leave main generator where it is.
The standby alternator runs continuously and is driven by an accessory drive at the back of the engine. It has a voltage regulator set point that is below the standard 28.5 volts, probably around 26 volts and automatically comes on when the Buss voltage drops to this level. It will annunciate that it is on and flash if current is above 20 amps. The pilot has about 5 minutes to shed load to the 20 amps. My guess is that it would run all the avionics on a typical 28 volt installation and probably also be able to power the pitot heat if needed. The pitot heat draws about 5 amps or less.
It is definitely considered a major modification and many many have been installed with field approvals. I would contact B&C for assistance in getting it approved as a field approval. BTW, it is an excellent system. The Beechcraft Bonanza A36 made it standard equipment.
It has a voltage regulator set point that is below the standard 28.5 volts, probably around 26 volts and automatically comes on when the Buss voltage drops to this level
That's really clever, and simple.
The pilot has about 5 minutes to shed load to the 20 amps
What happens if he doesn't do anything?
Am I right that these alternators need the battery to be connected?
The "not yet certified" (possibly "never to be certified") GAMI one doesn't need a battery; they appear to modulate the field current fast enough to give out a constant 28V.
The pitot heat draws about 5 amps or less.
Mine is about 10A, but apart from that 20A would be enough to power more or less everything in my TB20, enroute.
I would be really interested in pursuing this. I have a couple of installs to do this summer (both minor mods) and after that I will be ready to swallow another one... I would need a contact in the USA willing to present the 337 Field Approval on my behalf 
The TB20 does have an unused vac pump drive.
How much work would be involved in removing the KI256, dumping the entire vacuum system, and replacing it with an electric version? Castleberry make an exact replica of the KI256 but electric; I already have it on the RHS, operating as a dumb backup electric AI.
Practically - not a lot. Legally - horrendous!
Can you elaborate?
This is where the benefits of uncertified (LAA) aircraft really start to come into their own. In my Falco I have twin glass screens, auto-pilot fully coupled, (I have a GNS430W which when installed, will allow me to fly hands-off GPS approaches), electric back-up AI (no pitch), on-screen AOA and no vacuum system. I am considering installing a VPX pro, a device that controls all of the electric consumers without CBs or relays (except u/c) and can display all the relevant consumption on my screen, the back-up alternator, a blood oxygen level sensor/O2 sensor. ALL of this can be achieved for around £15-20k using brand new kit (Ok, the GNS430W is secondhand) that is of an equal or higher quality than certified equipment and will leave me with a far better equipped aircraft than most. Each of my screens has its own internal back-up battery that lasts up to one hour. With the VPX pro an alternator failure simply means that I can see all of the consumers displayed on screen and eliminate un-necessary consumers as required to get within the 20A available. This would mean that my flight could continue to my destination.
