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 Post subject: Re: Possible bug?
PostPosted: Mon Jan 16, 2012 2:12 pm 
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When i changed the temp to 25 while in an already loaded scenario, she started too, but if i ended the flight, set the temp to 25 in the scenario manager, and then loaded the flight, i couldn't start it. 8)


It had something to do with changing the oil, i made it into a situation, where no oil change was effective, the engine was cranking, and i was priming from time to time, couldn't do anything, cold&dark didn't work, hangar didn't work.

I don't know anymore, how the plane can start on lower OAT, but refuse to start on higher but still low OAT, humidity of the air maybe ?


Last edited by Caldemeyn on Mon Jan 16, 2012 2:54 pm, edited 1 time in total.

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 Post subject: Re: Possible bug?
PostPosted: Mon Jan 16, 2012 2:36 pm 
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Caldemeyn wrote:
When i changed the temp to 25 while in an already loaded scenario, she started too, but if i ended the flight, set the temp in the scenario manager, and then loaded the flight, i couldn't start it. 8)

This shouldn't have an effect, but I'll test it later when I have time.


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It had something to do with changing the oil, i made it into a situation, where no oil change was effective, the engine was cranking, and i was priming from time to time, couldn't do anything, cold&dark didn't work, hangar didn't work.

Hanger didn't work? Please explain.

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 Post subject: Re: Possible bug?
PostPosted: Mon Jan 16, 2012 2:37 pm 
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Meant, a "complete rebuild" :mrgreen: + battery charge, of course trolley connected all the time.


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 Post subject: Re: Possible bug?
PostPosted: Tue Jan 17, 2012 1:59 pm 
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Have you tested this scenario Mr. Cody ? i spent nearly half an hour, trying to start the damned thing 8) again to no avail.


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 Post subject: Re: Possible bug?
PostPosted: Tue Jan 17, 2012 3:16 pm 
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The V1.2 core requires quite generous priming (at least on my computer). In V1.0 I used to start the engine with max 12 strokes for anything below +5 deg Celsius. With 1.1, I didn't need any priming at all. Now, I need 12 strokes for +5 and around 20 for -10 deg C. Yet, some claim they start engines with just 12 strokes at -29 deg C. I wonder how they do it...

I definitely cannot get MkI to start with 12 strokes in -10 deg C. It typically coughs just once or twice (if even that much) and stalls immediately thereafter, even if I keep priming it extra strokes in addition to those 12 I gave it prior to starting the cranking. If I give it 16 strokes, I occasionally manage to get it alive. 18 strokes, it's already pretty likely.

MkII is in a way a bit easier on the primer since the Coffman starter gives higher rpm for that short duration of time it keeps spinning so around 16 strokes is already a pretty sure catch, especially if I give the final stroke or two during the cranking to guarantee a finer mist of fresh fuel to the manifold (though I don't know if the "freshness" of the primer is modeled or not, I still tend to do it because that's what I'd do if I operated a real engine).

And for the record: I have both main mags on, and starter mag on MkI, I have rich mixture, both fuel cocks open not only during starting but also during priming, and I have my throttle opened a bit more than just cracked open, around 1/3.

But, I'm not really annoyed by it. It might actually be more real if it requires more than 12 strokes in subzero conditions. It would actually make no sense at all if it required 12 strokes at +5 and the requirement wouldn't increase as you go subzero. I'm just wondering why some people (Cody for example) manage to get it running at -29 deg C without increasing priming even a little bit from what would be required for a cool-but-not-truely-cold environment. But that's not my problem. If it's a problem, it's their's. :p


___


I'm more annoyed by the pneumatic bug not being fixed even in 1.2 update. It's become even more frustrating with the improved start-up behaviour with v1.2. If you start with pneumatic tank unpressurized, start the engine underprimed, or for any other reason manage to stall the engine immediately after first coughs... enter the pneumatic bug: the pneumatic engine driven pump will CONTINUE to pump air into pneumatic tank even after engine as come to a stop. And it will continue hissing until the tank is fully pressurized.


Last edited by whiic on Tue Jan 17, 2012 3:28 pm, edited 1 time in total.

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 Post subject: Re: Possible bug?
PostPosted: Tue Jan 17, 2012 3:24 pm 
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whiic wrote:
The V1.2 core requires quite generous priming (at least on my computer). In V1.0 I used to start the engine with max 12 strokes for anything below +5 deg Celsius. With 1.1, I didn't need any priming at all. Now, I need 12 strokes for +5 and around 20 for -10 deg C. Yet, some claim they start engines with just 12 strokes at -29 deg C. I wonder how they do it...

I definitely cannot get MkI to start with 12 strokes in -10 deg C. It typically coughs just once or twice (if even that much) and stalls immediately thereafter, even if I keep priming it extra strokes in addition to those 12 I gave it prior to starting the cranking. If I give it 16 strokes, I occasionally manage to get it alive. 18 strokes, it's already pretty likely.

MkII is in a way a bit easier on the primer since the Coffman starter gives higher rpm for that short duration of time it keeps spinning so around 16 strokes is already a pretty sure catch, especially if I give the final stroke or two during the cranking to guarantee a finer mist of fresh fuel to the manifold (though I don't know if the "freshness" of the primer is modeled or not, I still tend to do it because that's what I'd do if I operated a real engine).

And for the record: I have both main mags on, and starter mag on MkI, I have rich mixture, both fuel cocks open not only during starting but also during priming, and I have my throttle opened a bit more than just cracked open, around 1/3.

But, I'm not really annoyed by it. It might actually be more real if it requires more than 12 strokes in subzero conditions. It would actually make no sense at all if it required 12 strokes at +5 and the requirement wouldn't increase as you go subzero. I'm just wondering why some people (Cody for example) manage to get it running at -29 deg C without increasing priming even a little bit from what would be required for a cool-but-not-truely-cold environment. But that's not my problem. If it's a problem, it's their's. :p


___


I'm more annoyed by the pneumatic bug not being fixed even in 1.2 update. It's become even more frustrating with the improved start-up behaviour with v1.2. If you start with pneumatic tank unpressurized, start the engine underprimed, or for any other reason manage to stall the engine immediately thereafter first coughs... enter the pneumatic bug: the pneumatic engine driven pump will CONTINUE to pump air into pneumatic tank even after engine as come to a stop. And it will continue hissing until the tank is fully pressurized.




Please try to start it at 30 deg F, its closer to 0 C, also isn't it strange, that when you are giving it 12 strokes, and then prime it more, it won't start, but if you give 16 immediately ,it can catch, where is the fuel going, also i too didn't have a problem with starting at -29 deg C. khy khy :mrgreen: with normal oil 8)


Also, what annoys me is the starter switch jumping away when close to catching :wink:


Last edited by Caldemeyn on Tue Jan 17, 2012 3:26 pm, edited 1 time in total.

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 Post subject: Re: Possible bug?
PostPosted: Tue Jan 17, 2012 3:26 pm 
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My subzero starts have been at around -10 deg C. Does it really take more priming on -10 deg C than +5 deg C... but less priming for -29 deg C than -10 deg C? Then it would definitely be odd.

Considering engine timers got reset along with the update, now it's probably the best time to do some destructive testing which might/will damage the engine:
So, I did a test at -85 deg C (-121 Fahrenheit)... and it started with not more than 12 strokes.

Requires more testing to conclude how priming requirement relates to temperature because -85 deg C is definitely out of realistic temperature envelope.


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 Post subject: Re: Possible bug?
PostPosted: Tue Jan 17, 2012 3:29 pm 
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Yes, the difference exists, the close to 0 C temps are the hardest to start in now, and priming when starter is already pushed doesn't give much, if anything.


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 Post subject: Re: Possible bug?
PostPosted: Tue Jan 17, 2012 4:31 pm 
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I tried +1 deg C with -2 dew point and primed 11 strokes with 2 extra during cranking. Fired on first try. No problem there for me. -10 deg C is bitchy but if I extrapolate operations manual from 12 strokes at +5 to what might be reasonable for -10 deg C, it usually starts on first try with 16-20 strokes. So IMO the inaccuracies don't come obvious until you use ridiculously low temperature (to which real Merlins weren't designed to operate in). Between +30 and -10 it seems to be OK on my system configuration.

Some stats for MkI:
+1 OAT, -2 dew, around 12 strokes
-8 OAT, -12 dew, 16-20 strokes
- 85 OAT, -90 dew, around 12 strokes (Mark II, invalid for comparison)
- 90 OAT, -95 dew, around 14 strokes

So far not tested: since -8 deg C seems a bitchy temperature for me, I could try keeping temperature a constant and vary dew point to see if it affects start-up.

My method of priming:
Priming done prior to cranking (except maybe for the last two strokes). Priming whilst cranking, starting with a dry manifold, isn't good since you'd end up cranking very long prior to getting 12 strokes done, plus while you crank the weak fuel mist will end up in cylinders and exhaust unburned (too weak to burn) ... therefore when you reach 12 strokes, there still is no fuel in the intake manifold. So prime at least to recommended number of strokes minus one or two strokes (maximum), if you want to continue priming while cranking. Likewise, if it doesn't catch within first ~5-10 seconds, it'll probably not catch at all even if you kept cranking and priming it for the rest of the day. Stop the starter, give 5-10 shots more (adding to any residual fuel that might already be there) and start cranking again. Alternatively stop cranking, let it sit for several minutes and prime it as you would prime a dry engine, using recommended number of priming strokes.

EDIT: invalidated MarkII result from list of start-up tests.


Last edited by whiic on Tue Jan 17, 2012 4:49 pm, edited 1 time in total.

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 Post subject: Re: Possible bug?
PostPosted: Tue Jan 17, 2012 4:44 pm 
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Of course, what i meant, that if you will give it a reasonable priming ( 12 strokes) and then it won't start, anymore priming when the starter is pushed will not have much effect.

Will test those figures you privided, thanks. 8)


Edit: Started 8), however i still am not sure, where did all this fuel i primed in my previous attempts went, for example -5 degress C 12 strokes, no start, and half an hour of cranking and priming, where does it go ?

All of this seems strange, these temps, all of it, for example, that i need to give it almost the same, or even more quantity of fuel, if it only budge a little, if not, i can do this all day. 8)


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 Post subject: Re: Possible bug?
PostPosted: Tue Jan 17, 2012 5:22 pm 
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Caldemeyn wrote:
Started 8), however i still am not sure, where did all this fuel i primed in my previous attempts went, for example -5 degress C 12 strokes, no start, and half an hour of cranking and priming, where does it go ?

There's no mystique about that. It goes into the engine, and out of the engine (unburnt). Why? Because you keep cranking it and in keeps sucking it and exhausting it while you crank, even if it doesn't catch.

If you need a superrich mixture for start-up (and you do for -5 deg C) you need to stop the engine for priming or you'll never get a superrich mixture as it keeps leaning out due to cranking. Cranking pumps air into the engine and along with the air, the fuel mist from the primer also ends up into the cylinders (and out of the cylinders). If it wasn't like that engine could never catch. It merely shows AccuSim abides to real-life physics.

Now the only potential primer related bug may be (or may not be) at temperatures between -10 deg C to -95 deg C... but I don't think there was that type of weather in England even prior to global warming. At least, not since the last ice age. :p


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 Post subject: Re: Possible bug?
PostPosted: Tue Jan 17, 2012 5:27 pm 
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The unused fuel goes out through exhaust pipes ? well i thought of that, but dismissed it, thanks.


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 Post subject: Re: Possible bug?
PostPosted: Thu Jan 19, 2012 5:04 am 
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tip

hold gas handel closed

so you dont prime for notting:P


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