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Avionics cut-off (Read 2965 times)
Ricardo Rodrigues
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Avionics cut-off
Feb 11th, 2011, 12:15pm
 
Hi!

I bought the fantastic CS727 on the Christmas promotion and I'm very pleased with it except for one thing... I know it's a known problem, but I'm getting my avionics shut-off in mid flight, a few minutes after takeoff (or sometimes still while taxiing), then I do a "Reload Aircraft", they come alive again and remain through the rest of the flight.
I've even added the "electric_always_available=1" line to the Electrical section of the .cfg, without apparent success. The Cessna's avionics in my default flight are also turned on.
I wonder I might be doing something wrong (right after all the 3 engines are up running and stabilized, I turn all the BUS, TIE, GEN switches up, Ess Power to Gen1, then shut APU off and that's all I can think of).

Any suggestions on here? Smiley

Thanks in advance! Wink
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TurbofanDude
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Re: Avionics cut-off
Reply #1 - Feb 11th, 2011, 1:33pm
 
Well, make sure the default battery and avionics are turned on. If you assign a key to the default battery, you can work the 727 battery with the default battery. I noticed  that using the Saitek panels.
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Markoz
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Re: Avionics cut-off
Reply #2 - Feb 11th, 2011, 1:50pm
 
Hi Ricardo.

I had a similar problem last year. I had electric_always_available=1 as well. I still lost them after about 30 minutes.

LOU kindly answered my problem here: http://www.captainsim.org/yabb2/YaBB.pl?num=1267897624/15#15 and in the replies that follow.
I was able to remove that line from the aircraft.cfg and I have never lost the avionics during a flight since.

Hope this helps.

Mark
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Mark Fletcher


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Ricardo Rodrigues
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Re: Avionics cut-off
Reply #3 - Feb 11th, 2011, 11:39pm
 
First of all, thanks for your help!

I've been reading Lou's posts (which are of great value and I adored to read BTW) attentively, alongside with CS' checklist, guess I did everything I read but still no dice. Embarrassed
At a first stage I kept standing on the ground running on APU power only, for something like 20 minutes if not more, and the 727 behaved very well (GPS always on states it was all fine), then I proceeded to a climb out and a few minutes after take off... avionics down again.
Here's a screenshot with the electrical panel status at the moment of the shut down (even battery life seems to be ok Undecided).


Also tried a keystroke for "Master Battery" and yet again, nothing at all.

Many thanks again! Wink
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Re: Avionics cut-off
Reply #4 - Feb 12th, 2011, 1:23am
 
Hi Ricardo.

The main difference between my settings and yours, from what I see in your image, is: In the bottom right of the image (see attached image), I see that you have the AC Meters Selector switch is set to BUS TIE. I set mine set to either GEN1, GEN2 or GEN3 (usually the same GEN# that my Essential Power Selector switch is set to). Try changing that to see how it works out.

If none of this works. Try pressing CTRL+E (MSFS default engine start) while in flight, this will usually bring back your avionics. That is what I did originally, until I sorted this problem out.

Hope this helps.

Mark
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Mark Fletcher


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LOU
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Re: Avionics cut-off
Reply #5 - Feb 12th, 2011, 3:30am
 
Ricardo,

Having the meter selector in Bus-Tie or any other position would make no difference since it's only a meter to read the various positions.
The essential power selector is the switch that keeps the essential bus powered. It must be on an operating generator. Normally, it would be kept on the number three generator so as to even out the load. You would never select essential to the number two generator unless it was the only operating generator because load bus two powers the F/O's instruments and essential powers the Captain's instruments. That would be putting all your eggs in one basket.

I have never had a loss of electrical power or loss of avionics in any CS plane.

I noticed in your screen shot that the ground power was still connected...were you in flight? If so that would be a very long power cable!  Grin
I also noticed that your battery volts look a bit low, but since the 727 had a pulsing charger it could have been going through a cycle. In any event I doubt that would be your problem.

Unless you have some failure programed into FSX I don't know why you are loosing radio power. Are you using some cold and dark start-up?

When I select a CS plane from the FSX main start menu, the plane comes up with the engines running and a canned amount of fuel and payload. I can then just go and fly. If I want to do a complete cold start I use this default CS aircraft with engines running and stock payload. Then I shut down the engines and turn off all the various systems including the battery. Then I save this plane and can load it any time and any place and use it to do my cold and dark start. That's just the way I do it, and it works for me.

When I wrote that old description of the F/E electrical panel I may have confused Mark by using different names for the various switches.

FIELD - GFR or generator field relay or generator relay - turns the generator on and off
MAIN - MGR or main generator relay - connects the generator to its load bus
Bus Tie - BTR or bus tie relay - allows one generator to power all load buses or more than one generator to connect together and share loads.

Hope you can keep the radios running.

Lou
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Markoz
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Re: Avionics cut-off
Reply #6 - Feb 12th, 2011, 7:08am
 
Thanks Lou.

I did not know that the best setting for the Essential Power Selector switch normally goes on GEN3 (I could have overlooked it in you instructions).
Nor did I know that the AC Meters Selector switch is "only a meter to read the various positions". I shall do my best to remember these in future!

Mark
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Mark Fletcher


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Ricardo Rodrigues
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Re: Avionics cut-off
Reply #7 - Feb 12th, 2011, 1:24pm
 
Many thanks for your replies!

Lou, my default flight is set to the C172 in Cold & Dark, everything off except for the avionics switch.
The ground power indicator light is actually off, although it appears to be lit. Grin

What I do, step-by-step when I start a flight with the 727 is, first of all, turn off window heat, pitot heat, packs, hyd pumps and all that sort of thing. Then I power up the battery, close all three BUS TIE*, turn APU on and when EGT stabilizes close APU GEN and FIELD, ESS PWR set to APU, Hyd B pumps on, packs on, etc (also turn to max the GEN frequency knobs)... then when it comes to start the engines turn packs and galley power off, get the engines started then follow the procedure for GENs' power setup as you describe on Mark's topic.

*- I'm a bit confused on how should the BUS TIE be handled, as the checklists tell to close all them three, and the fact that the BUS TIE causes the electrical power to be provided by one generator alone (if I understood correctly from your post). Should the BUS TIE be closed or tripped? Closed for one generator alone and tripped for the others?

Mark, Ctrl+E does the trick Wink, better than the "aircraft reload" which can cause some pain under workloaded circumstances. Grin

Thanks again Lou and Mark! Wink
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LOU
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Re: Avionics cut-off
Reply #8 - Feb 12th, 2011, 7:26pm
 
Ricardo wrote:
What I do, step-by-step when I start a flight with the 727 is, first of all, turn off window heat, pitot heat, packs, hyd pumps and all that sort of thing. Then I power up the battery, close all three BUS TIE*, turn APU on and when EGT stabilizes close APU GEN and FIELD, ESS PWR set to APU, Hyd B pumps on, packs on, etc (also turn to max the GEN frequency knobs)... then when it comes to start the engines turn packs and galley power off, get the engines started then follow the procedure for GENs' power setup as you describe on Mark's topic.

*- I'm a bit confused on how should the BUS TIE be handled, as the checklists tell to close all them three, and the fact that the BUS TIE causes the electrical power to be provided by one generator alone (if I understood correctly from your post). Should the BUS TIE be closed or tripped? Closed for one generator alone and tripped for the others?


Why don't you try loading the default CS 727 from the Aircraft select menu, then shutting everything down and saving the result in FSX as 727-cold-and-dark. It's just a thought since I don't know what the Cessna 172 C&D puts into the save.

One thing that bothers me is the fact that there are no master radio switches on the 727 overhead panel. You need to have these switches so you can really turn off the captain's radios in the event of an electrical fire. If the avionics switches are left on the battery will transfer power to the captain's radio bus. The battery system in the 727 has the battery bus, the battery transfer bus and the hot battery bus. The hot battery bus is powered whenever the battery is installed in the plane. It powers stuff like the PA and the fire bottle buttons. When external power is connected the battery charger is powered and charges the battery. Normal A.C. power powers the battery as well through the T.R.'s (transformer rectifiers) that make 28 volt D.C. and thus keep the battery charged. If you were to kill all power to the 727 and left the essential radio bus turned on the battery would die. So to truly be cold and dark you need to be able to turn off the essential radio master switch as well.

Each engine driven generator is able to produce 54 KW for 10 mins and 36 KW continuous. The APU generator is the same as the engine driven generators, except it is rated at 54 KW continuous because it is better cooled. DON'T turn the frequency knobs to max - keep them around the middle. The AC system needs 400 cycle power +/- a few cycles. Here is how the generators are handled during engine start...
All fields and Bus Ties are closed.
1. - APU is supplying electrical power to the aircraft.
2. - Turn off packs to reduce electrical load (pack fans) and air load to start engines. Duct pressure should read around 40 PSI.
3. - Start engine one. As engine comes up to idle check AC meters to engine one and look for 115 volts and 400 cycles. Adjust CSD to obtain 400 cycles.
4. - Move the Essential power switch to the number one engine generator.
5. - Close Main Generator Relay (middle switch). This action will trip the APU generator off and connect the engine one generator to power the plane. The same would happen if you were using ground power. Closing the MGR on generator will trip other power sources.
6. - Start next engine. Move meter selector to that engine and observe volts and freqs.

Here is where it gets complicated. Until now only one power source was connected to the aircraft. The bus ties were used to connect the load buss in series. Just like a power strip with several outlets and items plugged in to them - it is still one power source providing all the power. When you start the second engine generator and connect it to the aircraft you are using more than one power source and something special happens. The bus ties now become part of the Sync-Bus and a whole different system of control comes into play.

With just one power source generator protection consisted of overload protection and high or low voltage protection with wide latitude in the limits. Look at the meters gauge for voltage and frequency. The limits are the full scale of either gauge. This all changes when you connect the second generator. Now the bus ties change protection and become a Sync-Bus. A very complicated electrical system comes into action and load sharing of the generators starts. Now the two generators work together and attempt to equalize their loads. The limits on voltage and frequency variation are lessened because of this paralleling of generators. Overload protection changes and other faults related to the sync-bus come into the system.

So to answer your question about the bus ties. In normal operation all the bus ties should be closed (lights out). This will allow ground power or APU power to flow through the bus ties to their load buss.

OK, now you asked for it! Here is a look at the 727 electrical system.



I made some notes on the drawing along generator one.

From the generator moving up you have the field relay switch (GFR) - this turns the generator on and off by using residual voltage of the permanent magnet field to build up the voltage from around 15 volts to 115 volts.

Next is the generator relay or main generator relay (MGR). This connects the generator to the load bus. Essential power is supplied before the MGR.

Next is the bus tie relay (BTR). This connects the generator to the sync bus.

Had enough? It is a somewhat complicated system and you would need to study the system for some time to be able to understand what is happening to all the electrons.  Tongue

Here is a link to a page with 727 information. http://www.tecat.ca/B-727_Electrical.htm

Does this help? or is it too much.

Lou




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Re: Avionics cut-off
Reply #9 - Feb 12th, 2011, 7:40pm
 
Hi Lou and Ricardo.

If you look at the very bottom of the 727-100 Cold-n-Dark (KSEA), there is a lot of this sort of thing:

[CaptainSim]
AZ231Pos_click=1
AZ232Pos_click=1
GENERAL_LIGHT_TEST=0
ENG_GS_001_LIGHT_ON=0
FIRE_GS_002_LIGHT_ON=0
FIRE_GS_003_LIGHT_ON=0
FIRE_GS_004_SW2_ON=0
GS_005_BTN_POS=0
FIRE_GS_006_SW2_POS=0
FIRE_GS_007_SW2_ON=0
GS_008_BTN_POS=0
FIRE_GS_009_LIGHT_ON=0
FIRE_GS_010_SW2_ON=0

I haven't counted them, but I'd say well over 100 of those lines. Every time you save a flight with the 727, it puts all those lines in there. So I think that turning off any the extra switches, could get saved in the state you put them. Well worth a try.

With the Avionics Master Switch (or should I say lack of) I created a keyboard shortcut command to turn it on or off (CTRL+SHIFT+A).
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Mark Fletcher


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Ricardo Rodrigues
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Re: Avionics cut-off
Reply #10 - Feb 17th, 2011, 1:33am
 
Hi again, Mark!
Sorry for the late reply.

Made a new test, and saved the flight as you said, so I could compare [CaptainSim] values with the cleared for takeoff pre-saved flight (copying the Cold 'n Dark values to my default Cessna's flight won't make the 727 100% C&D as it should), and I found a disturbing asymmetry.

On my saved .flt, I'm getting
Gen_1_breaker_closed=0
Gen_2_breaker_closed=0
Gen_3_breaker_closed=0

and on the pre-saved cleared for takeoff they read
Gen_1_breaker_closed=1
Gen_2_breaker_closed=1
Gen_3_breaker_closed=1

besides some other differences concerning electrical system, which I can't "decode" by naked eye. Grin

Also under the engine parameters there are these values:
LeftMagneto=False
RightMagneto=False
GeneratorSwitch=False

On the other file they are all set to "true". This may index the "magnetos" (or equivalent, if there is such thing for a jet engined aircraft) are somehow turning off, and hence the generators will go out too. Undecided

Many thanks again for your efforts, Mark! Wink
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Re: Avionics cut-off
Reply #11 - Feb 17th, 2011, 1:44am
 
Hi Ricardo.

I haven't gone into it in depth. It was something I noticed when I opened the file using notepad. The key to understanding it all is to know what they do. That could take quite some time to decipher (I counted 800+ lines), so I doubt I will do it anytime soon.

Mark
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Mark Fletcher


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Re: Avionics cut-off
Reply #12 - Feb 17th, 2011, 11:35pm
 
Ricardo,   I had the same problem.   What I found was that even though all the switches on the engineer panel are set correctly i was still losing power to the avionics shortly after take off.   What I have found is that I needed to set-up a keyboard command for the Generator toggle switch.   Once you load the aircraft, toggle the command once (you will not see a switch move)  then the aircraft keeps power to the avionics after all of your generators are running
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Re: Avionics cut-off
Reply #13 - Feb 18th, 2011, 6:22am
 
Hi Ricardo and DrJ1.

When I start with the 727-100 Cold-n-Dark (KSEA), I just use the checklist, prepare my aircraft as usual. Once everything is done and I have started the engines, all is fine.

When I first started using the CS727, I had problems with the avionics dropping out after about 15 - 30 minutes. I used the electric_always_available=1 until I questioned Lou about this problem (see my first reply). Since then, I no longer use electric_always_available=1 and I have not lost power to the avionics since.

Mark
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Mark Fletcher


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Ricardo Rodrigues
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Re: Avionics cut-off
Reply #14 - Feb 18th, 2011, 7:51pm
 
Hum... it rings a bell now.
As you (Mark) are loading and starting your flights from the CS727 pre-saved flight, it means that the, so to say, FSX's default generator system is switched on and hence, correctly set for how CS 727 should be. If you check the Cold-n-Dark.flt, under engine parameters, you'll notice that for every 3 engines, the GeneratorSwitch command is set to "true". As the 727's switches do not seem to be directly connected to FSX "default" electrical systems, FSX won't reckon the generators as "switched on". In other words, if I set my default Cessna with generator on, then when loading the 727 all will be fine. Wink See what I mean?

Now I can almost say I found the deal. Grin

Thanks a lot DrJ1 for lighting things up here and yet again, Mark, for your tireless and precious help! Smiley
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