Below 2000lbs fuel + negative G's = flameout?
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The AB doesn’t matter only the G’s do. I just tested it again. Fuel Flow Rate at idle 800 and I managed to cause a flameout again at just below 2000lbs. I only wrote about the AB to remove the excess fuel faster to get below the 2000 mark.
OK just a language issue then as the way it was written sounded like you were doing this test at 2k fuel in AB which is just a little crazy. As long as the engine feed knob is in normal this shouldn’t be a thing. The two fuel pumps in the reservoir tanks will easily keep the engine running at 800 PPH regardless of inverted or negative G…
I’ll do more testing tomorrow but in the meantime maybe you can answer these two questions: are the RSVR tanks supposed to be the last tanks to be drained or not? What’s the significance of the 2000 lbs mark?
Yes the reservoir tanks are the last to empty. L3crusader covers the significance of 2k fuel is and this would be BMS only. The real deal won’t do that at your stated 800 PPH if the engine feed knob is in normal. If it is in the off position it would certainly flame out but that wouldn’t be limited to 2k fuel but at any fuel quantity remaining.
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So I checked. This is a peculiarity of the D model, I believe
Essentially, in normal conditions, the engine is fed equally from the FWD and AFT circuit. However, the D model has around 1000lbs less in the FWD circuit compared to the AFT circuit, because of that pesky backseat.
The result is that in a low fuel situation (like around 2000 lbs), the FWD reserve is not full anymore, when the AFT full reserve is still full and has 1000 lbs more in the main AFT tank to back it up.
As a result, in neg Gs, what happens in the code now is that the FWD tanks being not full and with neg Gs, the FWD pump ingests air (because fuel is displaced to the top of the tank) and that causes a flameout.
So the code works as intended, but to be extra sure, I’m asking a specialist to see if our modeling of the situation when only one of the 2 pumps ingests air is correct.
First of all thank you for digging into the code that quickly Just my luck that I ended up testing something related to the fuel systems while flying the F-16D model which seems to have that quirk IRL too but seriously the level of detail is just mind blowing! You guys rock!
Since I couldn’t sleep I also went ahead and created my own test mission with the F-16CM Block 50 (the plane I flew that made me investigate flameouts in the first place) and the Block 52 just to be sure. It seems to be working correctly with those two. No flameout above 1000lbs! I must’ve dropped below the threshold in my campaign mission without realizing (I was concentrating on getting back to the tanker during a turn) and then in order to investigate the issue ended up with the D model… at least I’ve learned a lot about the fuel systems!
Thank you all for helping out!
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Ditto on the level of detail and effort that went into these features…
I asked for this in the last iff thread, a bit tongue in cheek, not thinking it would happen.
4.34 has blown me away, and I’ve barely started to dig into it!
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4.34 has blown me away, and I’ve barely started to dig into it!
Indeed. This is a very good time to be a BMS pilot.
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As a result, in neg Gs, what happens in the code now is that the FWD tanks being not full and with neg Gs, the FWD pump ingests air (because fuel is displaced to the top of the tank) and that causes a flameout.
So the code works as intended, but to be extra sure, I’m asking a specialist to see if our modeling of the situation when only one of the 2 pumps ingests air is correct.
So I did ask, and that wasnt actually correct. If one of the pump ingests air, the volume of air actually fed will be negligible compared to the other pump’s fuel output.
Correction is easy enough
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How about on engine side? I seem to recall that there are negative G limitations on the oil sumps for some engines/variants - is that also included/already in there?
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if I remember corectly if inverted more than 30s HYS/OIL may lights up. But no real engine limitation. Is not implemented in game.
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That’s at least start…thanks.
One would think that if you continued with the OIL lights up for some time that you might eventually get a bearing failure…and/or engine fire. Something maybe worth looking into for the future?
I like the fuel management thing…that’s cool!
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One would think that if you continued with the OIL lights up for some time that you might eventually get a bearing failure…and/or engine fire. Something maybe worth looking into for the future?
Already asked … No idea if it will/could be done.
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Another failure to understand how the res tanks feed. If you go to engine feed off and go inverted or negative G you are removing most, if not all, of the systems ability to feed the engines. That you should be able to duplicate at any fuel load and would be the normal response to an abnormal input.
Or from BMS1F-16CM-1 Page 123 in reference to the engine feed knob.
“With the knob in OFF none of the pumps work and fuel transfer occurs only via gravity and siphoning action. During heavy manoeuvring or negative G the engine may flame out.”
And a failure tot Read the post correctly. But thanks for the use of more words to say the same thing
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It surprises me to note the tendency of some people to show how much they think they know while disrespecting other people that are trying to help. If some common manners would be used it would make this forum a less toxic place.
Apologies for derailing this topic for a bit./Rant off
Snowman
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Already asked … No idea if it will/could be done.
I’d think a simple timer would be sufficient…then…ENGINE FIRE! Oh well…I can wait.
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And a failure tot Read the post correctly. But thanks for the use of more words to say the same thing
Well actually if you read the post, Stubbies is correcting your post, NOT saying the same thing.
So I guess we can agree there has been a failure to read the post correctly. Id like to second your call for more common manners and respect, but Id also like to point out that before you leap to your own defense, Stubbies has pointed out that turning the ENG FEED system OFF means you will get flameout at any fuel condition with negative Gs or heavy maneuvering.
With low fuel in the reservoir tanks, it starts to matter less whether the ENG FEED knob is OFF or NORM, as negative Gs or violent maneuvering is likely to uncover the connection into the FFP anyway - regardless of how you pump into the reservoirs, if the reservoirs are low then it doesnt matter how you pump into there.
While you’ve suggested it is caused by the ENG FEED knob being OFF, the actual cause is the less than full reservoir tanks.
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Hi Blu3wolf,
I agree with what you are writing. I am fully aware of the fact that if you switch engine feed off you will experience a flameout at any fuelstate when pushing neg G. My post was meant as a suggestion for the OP to check.
Because my experience is that in order to help someone it usually pays off to do these checks. (It solves 80% of the cases). The flameout could e.g. also be a simple coincidence in the timing, resulting in more ore less the same fuelstate.
And to be clear: i did not suggest the check because i thought the OP had absolutely no understanding of the fuel system, but because we are humans
Anyway: lesson learned for me (Just not on the topic at hand, but more about human nature)
I will enjoy the cool additions of this update
Greetings Snowman