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Engine Failure

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Re: Engine Failure

Postby ORZMUD » Wed Apr 24, 2019 12:42 am

I think that was associated with idle approach VS full throttle takeoff and cruise throttle.


Now that you mentioned, it makes sense.

No, we model low oil from repeated use. I think we add some random water also.

We don't record all the properties associated with these two systems (oil and carb ice) but we do record coughing, and it was definitely an event associated with coughing. It got severe right as the engine shut off. I looked at the property tree and didn't notice enough of a change in oil pressure or EGT to think it was oil related. But it appears that we don't record the icing numbers only the engine status.


I'll appreciate any heading/direction as to where to start looking to add those values in the log

That's why that carb heat is there and is to be used on approach if there is any doubt about conditions. Really, always use it on a long approach is a good rule of thumb I think.


I'll add this to my pre-flight checklist. Thanks!

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Re: Engine Failure

Postby ORZMUD » Wed Apr 24, 2019 12:44 am

wkitty42 wrote in Tue Apr 23, 2019 7:20 pm:looks like it would be a good idea to add additional numbers to the recordings so these types of things can be replayed and analyzed thoroughly...


Totally agree, it will make it easier from the troubleshoot/support pov.

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Re: Engine Failure

Postby wlbragg » Wed Apr 24, 2019 2:01 am

You can add the following two signals to Aircraft/c172p/Systems/flight-recorder/components/engine.xml

Code: Select all
    <signal>
        <type>float</type>
        <property type="string">/engines/active-engine/carb_ice</property>
    </signal>

    <signal>
        <type>float</type>
        <property type="string">/engines/active-engine/carb_icing_rate</property>
    </signal>


So Aircraft/c172p/Systems/flight-recorder/components/engine.xml will look like this...

Code: Select all
    <!-- ============================================================== -->
    <!-- State                                                          -->
    <!-- ============================================================== -->

    <signal>
        <type>int</type>
        <property type="string">/controls/engines/active-engine</property>
    </signal>

    <signal>
        <type>bool</type>
        <property type="string">/engines/active-engine/exhaust</property>
    </signal>

    <signal>
        <type>bool</type>
        <property type="string">/engines/active-engine/cranking</property>
    </signal>

    <signal>
        <type>bool</type>
        <property type="string">/engines/active-engine/running</property>
    </signal>

    <signal>
        <type>bool</type>
        <property type="string">/engines/active-engine/crash-engine</property>
    </signal>
    <signal>
        <type>bool</type>
        <property type="string">/engines/active-engine/kill-engine</property>
    </signal>
    <signal>
        <type>bool</type>
        <property type="string">/engines/active-engine/killed</property>
    </signal>

    <signal>
        <type>bool</type>
        <property type="string">/engines/active-engine/crashed</property>
    </signal>

    <signal>
        <type>bool</type>
        <property type="string">/engines/active-engine/coughing</property>
    </signal>

    <signal>
        <type>float</type>
        <property type="string">/engines/active-engine/carb_ice</property>
    </signal>

    <signal>
        <type>float</type>
        <property type="string">/engines/active-engine/carb_icing_rate</property>
    </signal>

    <!-- ============================================================== -->
    <!-- Controls                                                       -->
    <!-- ============================================================== -->


That should give you the icing numbers needed in the future.

That's a quick lesson as to how to add information you want recorded. Beware they must be valid properties and not just a nasal variable to work correctly. You must make sure they are of the correct tpye, ir: int, float, bool, etc.
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Re: Engine Failure

Postby ORZMUD » Wed Apr 24, 2019 2:36 am

Thanks!
Will add it on my setup.
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Re: Engine Failure

Postby ORZMUD » Wed Apr 24, 2019 5:34 am

I started a new session and right after starting the engine it started to sputter again.
Saved the fgtape to this location:

http://www.saaib.net/file/c172p-20190423-201213.fgtape

I let the engine run in this state for a couple of minutes, then I disabled the "Complex engine procedures and failures" which immediately had the engine back to normal operation.

While playback of the fgtape I opened the Debug/Browse Internal Properties/engines/active-engine during the sputtering phase and after it recovers and couldn't see any much difference, other than the oil-pressure-psi constantly and slowly dropping, max RPM achieves below 1500.

The values of carb_ice and carb_icing_rate barely change.

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Re: Engine Failure

Postby psyduck » Fri Dec 01, 2023 1:02 pm

wlbragg wrote in Tue Apr 23, 2019 6:17 pm:Engine sputtering in the c172p in FlightGear is caused by one of two things that I know of, carb icing or low oil. Either can cause engine failure if your have the "Complex engine procedures and failures" checked. A long slow approach is where you would be more likely to experience icing in the carburetor. "Save state between sessions" isn't necessary for the oil to get low, I think that only requires "Complex engine procedures and failures".



on the cessna 172 when there is no more fuel (only 9 pounds remaining in each tank), the engine sputting but don't stop.


i have never experimented icing carburetor in FG :shock: . tried multiple times.

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Re: Engine Failure

Postby wkitty42 » Fri Dec 01, 2023 2:57 pm

psyduck wrote in Fri Dec 01, 2023 1:02 pm:on the cessna 172 when there is no more fuel (only 9 pounds remaining in each tank), the engine sputting but don't stop.

the c172p does model the whole tank and fuel... by that i mean that in a tank, there is always some fuel that cannot be used... so if you have a 50gallon tank with a 3gallon unusable portion, only 47gallons can be used... at that point, the craft is basically out of fuel... how long it can sputter after that point, i have no idea... ISTR some bit of discussion way back when this work was done... something in relation to the use of a very small tank as the carb fuel bowl and how it fills from the tank... as long as there's some fuel getting in the bowl, the engine may be able to sputter along... depending on the flow, i think...
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: Engine Failure

Postby psyduck » Fri Dec 01, 2023 6:26 pm

wkitty42 wrote in Fri Dec 01, 2023 2:57 pm: so if you have a 50gallon tank with a 3gallon unusable portion, only 47gallons can be used... at that point, the craft is basically out of fuel... how long it can sputter after that point, i have no idea...


unlimited. its' a bug. :wink:
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Re: Engine Failure

Postby wkitty42 » Fri Dec 01, 2023 7:17 pm

wlbragg will know more about it since they wrote that code (i think)...

other than that and to be sure, you are not using --enable-fuel-freeze are you?
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: Engine Failure

Postby wlbragg » Fri Dec 01, 2023 7:56 pm

What happens if you start the aircraft and lower the fuel sliders to 1.7 lb or .3 gal, or all the way to 0, does the engine stop? I just tried it on the current development version and it most certainly ran out of gas. What version of the c172p are you running?

@wkitty42 I did not write the original fuel code. I did add the integral tanks and coded the logic for switching tank type.

As stated previously, the sputtering is typically caused by the carb icing. I don't know that I ever tested it to the point of it freezing enough to stall the engine though.
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Re: Engine Failure

Postby wkitty42 » Fri Dec 01, 2023 8:48 pm

wlbragg wrote in Fri Dec 01, 2023 7:56 pm:@wkitty42 I did not write the original fuel code. I did add the integral tanks and coded the logic for switching tank type.

ahhhh! i knew you had something to do with some tanks on the craft ;)
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
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Re: Engine Failure

Postby psyduck » Sat Dec 02, 2023 3:28 pm

wkitty42 wrote in Fri Dec 01, 2023 7:17 pm:wlbragg will know more about it since they wrote that code (i think)...

other than that and to be sure, you are not using --enable-fuel-freeze are you?


no.
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Re: Engine Failure

Postby wlbragg » Sat Dec 02, 2023 5:04 pm

What happens if you start the aircraft and lower the fuel sliders to 1.7 lb or .3 gal, or all the way to 0, does the engine stop? I just tried it on the current development version and it most certainly ran out of gas. What version of the c172p are you running?


:BUMP:
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Re: Engine Failure

Postby psyduck » Sat Dec 02, 2023 9:23 pm

it's the base 172p .

if i lower the fuel sliders, the engine stop.
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Re: Engine Failure

Postby wlbragg » Sat Dec 02, 2023 11:01 pm

Have you looked in the GUI Debug under consumables fuel and watched the fuel flow as the slider got close to the end? Or watched the fuel and payload settings menu to see if it does indeed stop reducing the fuel amount?

it's the base 172p .

If you really want help, I need to know the version number, "the base version" is not a version number, it doesn't tell me anything. If it is the base aircraft that comes with the simulation, then what version of FlightGear is it? There are thousands of possible variations that you could be using.

There was a version of the aircraft, don't remember off the top of my head which one though, there was a bug that kept the float bowl from completely emptying out thus the aircraft would never run out of gas. That was fixed long ago, but maybe you have that version.
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