One of my reasons for getting into RC is my interest in electronics...it seems to me that there is alot you can do to add to a plane that you can make yourself...

My question, not knowing how this works, may sound dumb...

I know you cant reliably check absolute fuel level as the plane moves, but is it possible to check the fuel pressure. Im not sure how this works, but i know that in racing, the fuel is given as the pressure, since the motion would mess up a traditional reading...is this possible in a plane?

My idea is simple...i know most people just time their flights...but im always looking for different ways to do somthing...and i thought why not have an on-board monitor that reads the pressure, and when its drops to a predetermined point, you would be signaled by means of a low-voltage LED Strobe on the outside of the plane somewhere...

If thats not possible...i would probably do something for an onboard timer that alerts you in a similar way...

Before you say its overcomplicating something, i know....i know....i know.... but the materials would be light weight, isolated from the radio gear, and simple...not to mention a little cool....

No you can't check fuel like that from what i know, but the timer thing is something you should do with your watch, most flights only last 15 minutes and your ready to put the plane down by then most the time

Yes, you could do what you suggest by fitting some kind of level transducer in the tank and hooking it up to some onboard electronics.

You are unlikely however to be able to get off the shelf components to do this so you would need to fabricate most of the stuff yourself. You would also have a lot more things to go wrong.

I can't see that would be of any practical use in flying the model though. As newbtoRC says, mostly you are ready to land before your tank is empty.


Terry

Like I said, im not so much doing all of this for practical purposes...as I am just to make something somewhat usefull...

I guess ill stick to making my voltage checker (with loading) ....

Anywho...just ideas...

I'm not aware of any method to monitor fuel levels, but don't let that discourage you. One of the best parts of being an electronis hobbyist is to figure how to solve a problem. I wouldn't rely on the pressure method, though, as most fuel tanks are pressurized by the exhaust, so pressure would be relatively constant at a given throttle setting regardless of fuel level and would rise and fall with the throttle setting. Let us know what you come up with!

The best way to tell how much fuel you have left is what has been said above, just time it on your watch. i always forget to time it so i use the following method.
1. fill the tank untill it will take no more
2. fly until the engine quits and you have to bring it in for deadstick.
as soon as the fan on the front stops turning i know exactly how much fuel is in the tank (none) lol
thats why the irishman got killed flying his plane. he got cold and turned off the fan

My fuel level indicator is my prop... it stops when my tank is empty, and I know it's time to bring it in.

But seriously, I have thought it would be nice to get some telemetry back from the plane... RX batt voltage, fuel level, altitude, airspeed, etc. Here's a system that gives you some of these, although I don't think it does fuel level...

http://www.eagletreesystems.com/Seagull/seagull.html

yeah but look at how much it costs. i think it is a good idea also but i guess we have to way up the cost vs the benefits maybe it will not cost as much in a year or two then i may consider getting something like that

if you are using a three line set up i think you can do this. for the refueling line, make it long enough so that you can hold your plane vertical on its nose and hold the end of the line above the tank. where the fuel goes up to should be the level of the tank. of course there will be some capillary action but minimal. that should give you some level of fuel reading. this will work as long as the tank is not pressurized so for Y.S. engines, you need to release the pressure first.

so if you are using a two line setup maybe you can set up one tube for that specific purpose. however, it is important to note that you have to release the tank pressure as well as take out the fuel dimple for it to work.

while theoretically you can do this with the plane level as well and the refueling tube vertical, i think the reading will not be accurate.

Pretty neat idea if you could come up with something. [8D]

If you just want to see the fuel level of your plane while it's on the ground, to me the easiest solution would be to make a clear viewing port for your fuel tank, and get a clear or translucent tank. Make a hole in the fuse on one or two sides of the tank and cover it with some clear covering or packing tape.

I'm considering doing that with my next PVC fuse SPAD... just need to drill a hole with a hole saw on a couple of sides of the fuse where the tank sits, and then cover it with some clear packing tape. More than one hole should let more light in, so you can see the fuel level through a translucent tank a little better...

Why not build a capacitance type fuel indicator like used in fullscale jets. Tank probes are needed. What happens is you have 2 die-electrics. Fuel and air. As fuel goes down, capacitance changes due to the change in die-electrics. Make a trigger circuit to alert you somehow when a certain capacitance is achieved.

Complicated? yes. tedious? yes. cool? yes. practical? not for RC applications.
My TX has a timer that turns on when I advance the throttle. I havent run out of fuel in flight in a long time.

Good luck!
Sean

rjm,
As has been said, the majority of our tanks are pressurized by the exhaust, so a pressure switch probably won't be feasible.

The fuel also sloshes around a lot when flying, so I guess you'd need to design baffles for a tank to stop that from happening. Of course your fuel gauge wouldn't work very well when inverted.
Dennis-