From: "Stephen Izett stephen.izett@gmail.com" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] Re: CofA
Date: Mon, 14 Jan 2019 19:42:51 +0800
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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Message-Id: <D8774870-6415-4EC4-B58B-EBDC6857447C@gmail.com>

Thanks Charlie
I=E2=80=99m going to look into installing OV protection. Good insurance =
at the price.

Steve

> On 14 Jan 2019, at 8:37 am, Charlie England ceengland7@gmail.com =
<flyrotary@lancaironline.net> wrote:
>=20
> You're probably right about the not-instant voltage increase if =
there's a regulator failure, but it would likely get to 20V pretty =
quickly. I guess it's a personal comfort zone thing. But here's a story =
about a former a/c partner, who was considered one of the best =
commercial pilots / instructors in our area. He was landing a very =
expensive twin and had a gear-up landing. He later said that he was =
distracted during the final approach & touchdown by trying to =
communicate while the horn was blaring in his headset.
>=20
> I figure that if he could miss a warning, I can, too.
>=20
> On the question of how much OV the various components can handle, I =
don't know, but I don't really want to find out. With big transorbs and =
zeners getting so cheap, I have pondered the installation of a current =
limiting resistor & zener type device at the power input of the more =
critical and expensive stuff. But I did install OV protection, so it =
would be kind of like expecting two related failures in one flight.
>=20
> Charlie
>=20
> On 1/13/2019 6:00 PM, Stephen Izett stephen.izett@gmail.com wrote:
>> Hi Charlie
>>=20
>> Yes in relation to Aeroelectric, and I did a load analysis.
>> I was only going to rely on an over voltage alarm from the dynon, =
believing that OV wasn=E2=80=99t such a problem for modern automotive =
alternators, but given its electrically dependant perhaps the risk =
should be mitigated by a crowbar
>> What is the risk of over voltage from a modern automotive alternator =
and what happens next. Ive read various thoughts?
>> I thought the EC3, EM3, pumps, coils and injectors would survive 20v =
for time enough to put it on the ground.
>>=20
>> Appreciate the feedback.
>>=20
>> Steve
>>=20
>>=20
>>=20
>>=20
>>=20
>>=20
>>=20
>>> On 14 Jan 2019, at 12:39 am, Charlie England ceengland7@gmail.com =
<flyrotary@lancaironline.net> wrote:
>>>=20
>>> On 1/13/2019 9:23 AM, Charlie England ceengland7@gmail.com wrote:
>>>>=20
>>>> On Sun, Jan 13, 2019 at 9:00 AM Stephen Izett =
stephen.izett@gmail.com <flyrotary@lancaironline.net> wrote:
>>>> Hi there people
>>>>=20
>>>> We are in the process of getting the Certificate of Airworthiness =
for our Glasair powered by Renesis 4 port.
>>>>=20
>>>> Our AP is questioning the electrical system and wondering if we =
should have redundant supplies in case of electrical system failure.
>>>> Can any of you make comments on risk or preferred systems.
>>>>=20
>>>> Our setup has one automotive 40amp alternator and two HC20 (PC680 =
equivalent) paralleled (two batteries are used due to physical location) =
and mounted in tail for W&B and to keep cool.
>>>>=20
>>>> My planning was:
>>>> 1. Keep battery cool
>>>> 2. Replace every two years
>>>> 3. Battery Failure modes:
>>>>         Open circuit cell - Alternator and second battery do the =
job (No indication that one battery has failed)
>>>>         Short Circuit cell - Battery voltage drops and overcharges =
??
>>>> 4. Alternator failure modes:
>>>>         Open Circuit - Low current and Low voltage alarm with 30min =
electrical reserve capacity
>>>>         Short Circuit - Charge circuit fuse blows then same as open =
circuit
>>>>=20
>>>> I understood that a shorted cell was very low risk in AGM=E2=80=99s =
if not overheated.
>>>> I thought creating redundancy may introduce other failure modes.
>>>>=20
>>>> Appreciate any feedback.
>>>> Steve
>>>>=20
>>>> Hi Steve,
>>>>=20
>>>> Are you signed up for the Matronics Aeroelectric List, and do you =
have a copy of the Aeroelectric Connection book? If not, then stop, do =
not pass go, and do both. Those issues are pretty well hashed out there.
>>>>=20
>>>> Now to specifics. Have you done a load analysis for your plane? If =
not, you might be a bit surprised at how much current can get sucked up =
by modern homebuilts, especially running automotive style injection. =
FWIW, 55-60 amp alternators are available for very little money (at =
least here in the USA) and likely will weigh no more than your 40A =
model. The higher output models will be running a lot farther from their =
max output (think heat).
>>>>=20
>>>> Failure modes: I'd agree that properly maintained, the battery is =
one of the least likely things to have a catastrophic failure. =
Alternators, not so much, though modern ones are pretty tough. You left =
out one failure mode: overvoltage due to regulator failure. That is the =
one that presents the biggest risk, because it can take out everything =
electrical in the a/c. There are simple protections for it, which result =
in the same plan B as your other failure modes: get on the ground within =
30 minutes. Some have tested battery life in VFR a/c using Tracy's =
engine controller & minimal airframe electrical loads, & saw around =
35-40 minutes life with a PC-680 size SLA battery.
>>>>=20
>>>> More later; time for breakfast.
>>>>=20
>>>> Charlie
>>>>=20
>>> Ok, refueled.
>>>=20
>>> The 'simple protections' mentioned earlier are an overvoltage =
detection module that monitors bus voltage and if it gets too high, has =
the power to shut down the alternator. B&C Specialty used to sell a =
little 'crowbar' module that did this job. It's fairly simple to =
fabricate your own, or you can buy something 'off the shelf' that can =
work in a similar manner. ex:
>>> https://www.tomtop.com/p-e1021.html
>>>=20
>>> Here in the USA, inspectors have accepted single alt, single =
battery, but most don't even question it; it's 'experimental'. But if =
you accept the premise that odds of multiple failures in a single flight =
*extremely* unlikely, and battery failures are almost always 'graceful' =
(meaning gradual and detectable), then the battery becomes the backup =
for the alternator. It's our job to decide how long we need that backup =
to last in operation, and to do our due diligence in maintaining the =
battery in good condition. That does mean doing capacity testing, =
because battery power and battery capacity are not the same thing. A =
very unhealthy battery can start an engine, but might have very reduced =
capacity to keep the electronics alive for the expected time. In my =
mind,  the biggest risk is the battery's variable capacity as it ages.
>>>=20
>>> I chose to add a 2nd identical alternator (~10 lb weight penalty), =
and my wiring architecture has my engine functions on one bus and the =
rest of the plane on a separate bus. Either bus can feed the other if =
there's a power feed issue to a bus (bad switch or contactor), and the =
engine will continue to run if the master must be turned off ('smoke in =
the cockpit' scenario).
>>>=20
>>> Charlie
>>>=20
>>> 	Virus-free. www.avast.com
>>=20
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>=20
>=20
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>=20
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