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APU won't start after cranking it?


Huesudo
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I found that I can't start the APU after cranking it.

 

I've looked more into it and recorded a track.

 

First I start the APU just fine, then shut it down, then start it again.

After that, i shut it down and then try to crank it with the fuel shut off.

It wont start normally after that. It looks like it tries but doesn't manage.

 

Am I doing something wrong?

mi8_apu.trk

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I found that I can't start the APU after cranking it.

 

I've looked more into it and recorded a track.

 

First I start the APU just fine, then shut it down, then start it again.

After that, i shut it down and then try to crank it with the fuel shut off.

It wont start normally after that. It looks like it tries but doesn't manage.

 

Am I doing something wrong?

 

Could the battery be drained? Watch the voltmeter/ammeter and see the constraints to check for in the manual posted elsewhere. It's easy to suck the batteries dry after a fews starts if you don't recharge them (rotor RPM high enough and main transformers/rectifiers on or at least start the APU generator)

 

By the way there is (used to be?) a bug where the APU generator ammeter doesn't work - shows zero current all the time.

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Could the battery be drained? Watch the voltmeter/ammeter and see the constraints to check for in the manual posted elsewhere. It's easy to suck the batteries dry after a fews starts if you don't recharge them (rotor RPM high enough and main transformers/rectifiers on or at least start the APU generator)

 

By the way there is (used to be?) a bug where the APU generator ammeter doesn't work - shows zero current all the time.

 

I've done some testing with the APU and the batteries, and it doesn't seem to be the problem.

 

Its more like, if I try to crank the APU or forget to turn on the fuel pumps when I try to start it, it will become stuck in the start process.

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It seems in this most recent patch, the battery voltage doesn't go down after starting the APU. Beforehand, the batteries (depending on weather) would be between 19-21 VDC after starting the APU the first time, down from 24. Starting a second time is possible on rare occasion (if it was warm out), though if it fails, the voltage would then be down to 12-14 VDC with no chance after that. Now, it goes right back up to 24 once the APU is up, even after starting the APU twice.

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I agree with you, my description was just another 'oddity' in APU function in the recent beta. I described in a thread (before this one) the problem where I can start the APU from a cold state and just leave it on for maybe 15-20 minutes, when the generator ability of the APU suddenly fails (observed when the generator is turned on, as witnessed by the voltage and amperage gauges abruptly zeroing out), but the APU still remains on so you can still crank the engines.

 

However, if I turn the APU off after that event happens and try to turn it on again, it won't work (even using, as you said, external power). I can start a mission in the air and after a certain time (maybe that same roughly 20 minutes) I can't start the APU up there, either. So, oddities are definitely afoot, the APU has become strange in many ways..


Edited by Strekaya
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  • 2 months later...

Any news on this issue? I cannot restart APU once I turned it off. I tried to take care of the loads on battery and electrical system when turning the heli on and off, but no chance.

 

Since it seems that in DCS there is no chance to get a report of system failures (why?), I tried to use autostart to get an analysis and it said "ai-9 not ready to start engine".

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I've found that, with the APU running, if you look at the DC power panel on the right, put the rotary in STBY GEN and the DC voltmeter reads 0, the APU probably won't start again after stopping it.


Edited by Huesudo
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Tested APU again. After engaging STBY GEN and having a load of ~ 100Am with only pumps and inverters running the STBY GEN quits after 30 seconds or so and load is zero. After that it's not possible to restart the APU at all.

 

Run AI-9, connect it to the grid, not including absolutely no customers. Ammeter shows a significant load on the generator, about 70 A. I repeat, consumers are turned off. Now turn off any of the batteries, but only one, because something, if you disable the two batteries, harvested AI-9. This play in life, it should continue to run. We look at the current meter with one battery is disconnected, the load falls to 20-30 A. It turns out this picture of a weak battery, put a strain on the AI-9. In life, is not it, the battery of the AI-9 is not charged. The most interesting thing then - let the AI-9 work for 5-10 minutes. with one connection acc. Load falls, battery charging is simulated by AI-9. AI-9 in this case is working properly without tripping. In minutes, you can connect a second 5 acc. without the fear that AI-9 off. And after 5 minutes after charging the second battery simulation. , The load on the ammeter no more than 40-50 A. It is safe to connect the drive, the load on the AI-9 in the normal range of not more than 55A. You can then make any inspection and connection equipment, problems with AI-9 will be gone. You can now disconnect both battery AI-9 will continue to work without any problems. It turns out that the problem in the batteries. And of course, incorrect implementation of charging acc. from AI-9.Akkumulyatory charged only when connected rectifiers working with generators or aerodrome AC power. And here yet implemented such a desired, high current for charging acc. AI-9 from the load to the generator AI-9 for charging two acc. removes it from the system. Batteries should not create any problems generator AI-9.

Do you want to simulate launch and test equipment from AI-9, disconnect one battery, AI-9 would work just fine, will not be switched off.

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Thx a lot, Alexandr! That answers a lot of questions. I tried every scenario you explained and it worked perfectly well. Now that I understand that because of incorrect implementation in the sim the batteries are getting charged by the AI-9 GEN, I can deal with the problem.

 

Do you know if the development of the electrical system is still going on? Ground operation and preparation is more then half of a successful flight as you will know.

 

It reminds me a lot of the time in the good old Project Tupolev's brilliant TU-154m in FS9 and it's electrical system, where you had to take care not to overload the APU GEN, while testing autopilot systems etc. It has its charm for sure.

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Thx a lot, Alexandr! That answers a lot of questions. I tried every scenario you explained and it worked perfectly well. Now that I understand that because of incorrect implementation in the sim the batteries are getting charged by the AI-9 GEN, I can deal with the problem.

 

Do you know if the development of the electrical system is still going on? Ground operation and preparation is more then half of a successful flight as you will know.

 

It reminds me a lot of the time in the good old Project Tupolev's brilliant TU-154m in FS9 and it's electrical system, where you had to take care not to overload the APU GEN, while testing autopilot systems etc. It has its charm for sure.

 

Yes, I know that BeiSimTek doing now correcting errors in the electrical system MI-8 MTV. I hope that soon everything will work properly!

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