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Building and Flying Related Boards › miniMax, Hi-Max, and AirBike General Discussions
Fuel pressure warning
11 posts
radfordcSeptember 5, 2019, 9:32pm
After recently having to do a precautionary landing due to a clogged fuel filter I decided to install this simple warning system to prevent this problem recurring.  This system includes a pressure switch that turns on when fuel pressure falls to 2 psi or below and an indicator lamp to alert you of the low pressure problem.  In practice, the warning lamp will come on giving you enough time to land safely.

The components are....
- Honeywell pressure switch, 2 psi, Normally Closed (NC)
- 12 volt panel lamp
- two position toggle switch
- 1/4" barbed tee brass fitting
- 1/4" barbed to 1/8" female NPT fitting
- short length of 1/4" ID fuel line


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radfordcSeptember 8, 2019, 7:16pm
Installed the pressure switch between the fuel pump and a carb.


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radfordcSeptember 8, 2019, 7:17pm
Installed the lamp and switch.  When the switch is up the lamp is lit until the fuel pressure exceeds 2 psi.


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TreeTopsTomSeptember 9, 2019, 1:05am
Charlie,  NICE!
One ?
If the switch is OFF, the lamp will NOT be able to light? correct?
What if you forget to turn the switch on (I know) , OR accidentally in flight it is turned off?
IE: shouldn't the power to the lamp be through some non inflight interruptible source (Like the main ignition switch) OR should the switch have one of those protective covers on it? Like the RED & Blue switches on this panel.
Just throwing it out there. Not meaning to throw  wrench in the turbo fan.           TTT


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Max SSDRSeptember 9, 2019, 10:15am
Quoted from radfordc After recently having to do a precautionary landing due to a clogged fuel filter I decided to install this simple warning system to prevent this problem recurring.  .....


Hi Radford C, I hope you don't mind but I've copied your Low Fuel Warning system and a couple of photos onto the UK Minimax FB page (with credit to you!)?  Here: https://www.facebook.com/groups/MinimaxUK/

I think it's an excellent idea.
radfordcSeptember 9, 2019, 3:58pm
Yes, if the switch is Off the warning lamp won't light.  That is why I put the switch next to the ignition switches....when I flip the ignitions on, I also turn on the warning light.  This gives a "self test" feature....I see the light come on before cranking the engine and see the light go out as soon as the engine starts.  At the end of the flight I see the lamp come on as soon as the engine shuts down and then I turn the lamp off so as to not drain the battery.

I've though about other "hands off" ways to do it and haven't come up with anything yet.
radfordcSeptember 26, 2019, 9:13pm
Tested the plane today after the new fuel system changes.  Everything worked as expected.  Nice day to fly for a change.


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Greg DoeSeptember 27, 2019, 3:54am
BEAUTIFUL!
radfordcSeptember 27, 2019, 7:07pm
Flying yesterday, I noticed that something had changed in how the engine ran.  Ever since I've had this engine it's had a quirk...it would not hold a steady rpm between 5500 and 5900.  If you were above 5900 and reduced the throttle slightly the rpm would immediately drop to under 5500.  Likewise if you slowly increased the throttle the rpm would jump to over 5900.

With the new fuel filter this doesn't happen!  It holds any rpm perfectly.  Obviously the old filter was causing a problem all along.
TreeTopsTomSeptember 29, 2019, 6:47am
Nice when things work out like that Charlie.
That's a beautiful airplane by the way. I was looking REAL HARD at that exact
kit quite a few years back. Cool to see a buzzard flying around in one.       TTT  
JGlassFNPOctober 8, 2019, 12:42pm
Great work! One can never have to much redundancy built into their aircraft.