ssvoysky(at)gmail.com
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 Posted: Fri Jun 02, 2017 9:47 am Post subject: Generator failure/ loss of electrical power |
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The generator was replaced today and "generator failure" light no longer comes ON. Hope it is a permanent fix. Thanks everyone for helping me out.
[quote] On May 13, 2017, at 3:04 AM, Yak-List Digest Server <yak-list(at)matronics.com> wrote:
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Total Messages Posted Fri 05/12/17: 10
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Today's Message Index:
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1. 10:18 AM - Generator failure/ loss of electrical power (Serge Svoysky)
2. 12:16 PM - Re: Generator failure/ loss of electrical power (Roger Kemp)
3. 12:36 PM - Re: [Non-DoD Source] Generator failure/ loss of electrical power (Bitterlich, Mark G CIV NAVAIR, WD)
4. 12:43 PM - Re: Generator failure/ loss of electrical power (Pedro Cerveira Pinto)
5. 03:20 PM - Re: [Non-DoD Source] Generator failure/ loss of electrical power (Roger Kemp)
6. 05:07 PM - Re: Generator failure/ loss of electrical power (A. Dennis Savarese)
7. 05:31 PM - Re: [Non-DoD Source] Generator failure/ loss of electrical power (A. Dennis Savarese)
8. 06:04 PM - Re: Generator failure/ loss of electrical power (Cerveira Pinto)
9. 06:41 PM - Re: Generator failure/ loss of electrical power (A. Dennis Savarese)
10. 07:55 PM - Yak 55M Throttle Cable (Jason .)
________________________________ Message 1 _____________________________________
Time: 10:18:57 AM PST US
From: Serge Svoysky <ssvoysky(at)gmail.com>
Subject: Generator failure/ loss of electrical power
Hello all,
Looking for advice on the following situation- everything looked normal on the
ground; "generator failure" on idle, but went away with RPM increase, proceeded
to take off and got "generator failure" right away on departure. Landed to check
on the ground again, all looked normal, departed, light came on. Decided
to go for a short flight, started losing all electrical equipment one by one starting
with the radio, but got it all back on final approach when power was reduced.
Worked fine (no light, charge as usual) on the ground.
I'd appreciate for any help!
YAK52 in NJ
Thanks,
serge
________________________________ Message 2 _____________________________________
Time: 12:16:30 PM PST US
Subject: Re: Generator failure/ loss of electrical power
From: Roger Kemp <f16viperdoc(at)me.com>
What was your voltage meter doing? Was it the "GenFault" light that came on and
at what %RPM were you getting the light.
Doc
Doc
Sent from my iPad
> On May 12, 2017, at 12:16 PM, Serge Svoysky <ssvoysky(at)gmail.com> wrote:
>
>
> Hello all,
> Looking for advice on the following situation- everything looked normal on the
ground; "generator failure" on idle, but went away with RPM increase, proceeded
to take off and got "generator failure" right away on departure. Landed to
check on the ground again, all looked normal, departed, light came on. Decided
to go for a short flight, started losing all electrical equipment one by one
starting with the radio, but got it all back on final approach when power was
reduced. Worked fine (no light, charge as usual) on the ground.
>
> I'd appreciate for any help!
> YAK52 in NJ
>
> Thanks,
> serge
>
>
>
________________________________ Message 3 _____________________________________
Time: 12:36:14 PM PST US
From: "Bitterlich, Mark G CIV NAVAIR, WD" <mark.bitterlich(at)navy.mil>
Subject: RE: [Non-DoD Source] Generator failure/ loss of electrical
power
I am assuming we are dealing with a stock Russian generator system.
It appears that the generator light is telling you the truth. The first thing
I would suggest is that you keep a close eye on the volt/amp meter. Some YAK-52's
have a meter that only shows current, and some have the meter with a button
on it that allows you to also check voltage. Which do you have?
This meter tells you a lot about what is going on with your system. You should
be running checks and looking at readings anytime you have a generator light
issue.
The generator light is controlled by the MAIN CONTACTOR RELAY on the Combined Device
DMR-200 relay assembly. When the MAIN CONTACTOR closes, the generator
light goes OUT. When that MAIN CONTACTOR OPENS the generator light comes on.
So what appears to be happening in your case, is that when power is increased,
the generator is working, and the MAIN CONTACTOR closes. Generator power has
to be above battery voltage for the main contactor to close. So the generator
voltage is there, the main contactor closes and everything is working.
After take-off, the main contactor opened, we do not know why yet but it was not
over-voltage, because that trips out a small breaker which has to be reset
to get power back. Since you did not have to reset anything, it was not over-voltage.
However, if the generator voltage dropped, the main contactor would
open, the light would come on, and I suspect this is what happened.
What is worse is that it is clearly apparent that you battery condition is very
bad. When you lost the generator, the battery should have powered your whole
aircraft for at least 30 minutes!
So first things first, put a hand held volt meter on your batteries (engine not
running) and check the voltage when you turn on the Master and verify that your
battery voltage maintains 22-24 volts or so. If the voltage starts dropping
to something like 19 or lower, you have weak and/or bad batteries. Replace
them. The Russian system reverse current relay RELIES on you having good batteries.
Period end of story. If you have weak batteries, all kinds of bad things
happen, and it appears from your story that you might very well have stumbled
into that condition.
Once we get past the battery, the next issues is your generator system. If you
are lucky, you will have a meter installed in the aircraft that shows voltage,
but that is BUSS voltage. It will not tell you what the generator is doing
when the GEN LIGHT IS ON.
The generator light can come on the way you are describing if you have a bad generator,
a bad voltage regulator, or a bad Combined Device Relay. As I said,
make sure you have good batteries before you proceed to the next step!
Take the cover off the generator that provides access to the generator wiring.
First check that you don't have a loose nut on the wires. It can happen and
cause intermittent output, which would cause this exact gripe. Moving on, connect
a volt-meter to the + and - wires. PLUS AND MINUS, so they won't just
fall off because you are going to start the engine with these wires on, with the
meter back in the cockpit. You can put the cowling back on if you want. Start
the engine and verify that once you are above idle, the voltage stabilizes
at about 28 VDC. Run the engine up quickly to as high as you can holding the
brakes. Be safe. The voltage should stay rock steady at 28 VDC. Depending
on exactly what it does will tell us if it is a bad generator, or bad voltage
regulator.
Mark
--
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