Viperdoc
Joined: 19 Apr 2014
Posts: 484
Location: 08A
|
 Posted: Fri May 12, 2017 2:20 pm Post subject: [Non-DoD Source] Generator failure/ loss of electrical pow |
 |
|
Good gouge Mark. Knew you would surface on this topic.
Doc
Sent from my iPad
[quote] On May 12, 2017, at 2:33 PM, Bitterlich, Mark G CIV NAVAIR, WD <mark.bitterlich(at)navy.mil> wrote:
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
--
| | - The Matronics Yak-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Yak-List |
|
_________________
Viperdoc |
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
