REFLECTOR: Re: Reflector Digest, Vol 9, Issue 68-Fuel Feed-blinking low fuel warning

[Jim Sower]

Yes. Nearly every car with a low-fuel warning has one. Most I believe, 
are photoelectric sensors. I know a guy who has one in his fuel line 
that lights when his tank runs dry.
A really nice thing to have around ... Jim S.

Tom Martino wrote:

> Isn’t there a simple on/off fuel sensor that can be installed? “ON” 
> when fuel touches it, and “OFF” when fuel drops below a certain level? 
> Like the sensors in RV water tanks?
>
> -----Original Message-----
> *From:* Carruth, Joel L [mailto:joel.l.carruth at lmco.com]
> *Sent:* Friday, February 18, 2005 7:34 AM
> *To:* Velocity Aircraft Owners and Builders list
> *Subject:* RE: REFLECTOR: Re: Reflector Digest, Vol 9,Issue 68-Fuel 
> Feed-blinking low fuel warning [heur]
>
> Jeepers! I’ve been listening to the problems with unporting, greasing 
> the o-rings, false sump indications over 10K, and “no way” of knowing 
> what situation your fuel is in, and frankly it leaves me a little 
> worried about my future fuel system!!! On one hand, I tend to agree 
> with Scott Baker and don’t change the design, but on the other, you 
> all have convinced me that there is room for some tweaking! I just 
> don’t believe in guessing about my fuel condition.
>
> In particular, I plan to do away with the float switch and install a 
> fuel-level sensor in the sump. Secondly, a simple flow switch in each 
> line from the mains would give you vital information about which way 
> the fuel is going! This wouldn’t be an expensive flow meter, but a 
> simple flow switch with indicator. I think Omega sells these for 
> around $130 each. Two switches, plus the fuel-level sensor would take 
> the guess work out of fuel management and allow the pilot to make 
> corrections as needed… before the fan goes quiet!!
>
> ’96 SEFG
>
> */Joel Carruth/*
>
> Lockheed Martin
>
> JSF - Pilot System Software
>
> W: (817) 763-4337
>
> Fax: (817) 777-8378
>
> joel.l.carruth at lmco.com
>
> ------------------------------------------------------------------------
>
> *From:* reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] 
> *On Behalf Of *Jim Sower
> *Sent:* Thursday, February 17, 2005 9:02 PM
> *To:* Velocity Aircraft Owners and Builders list
> *Subject:* Re: REFLECTOR: Re: Reflector Digest, Vol 9, Issue 68-Fuel 
> Feed-blinking low fuel warning
>
> <... The only way I could see that happening is if the flow from the 
> mains is somehow restricted due to inadequate venting, and that the 
> fuel pump is pulling fuel out the sump tank and the sump vent line is 
> letting in air into the sump lowering the fuel level. ...>
>
>
>       *Bingo!!*
>
> And once your sump fuel level falls low enough to light the low fuel 
> light, you never know how much usable fuel you have until that light 
> goes out. The mains might be providing 95% of demand in which you'll 
> make it home with a gallon or two in the sump. Then again, they might 
> be only providing 50% of demand in which case you flame out in under 
> an hour. If the strakes are only providing 25% of demand, you've got 
> about half an hour of fuel.
> And you have NO WAY of knowing which situation you're in until either 
> you get where you're going and LOOK at the sump, or the fan goes quiet.
>
> Go ahead and ask me how I know this ... Jim S.
>
>
> Chuck Harbert wrote:
>
> To John Dibble:
>
> This is very strange that it only occurs intermittingly at high 
> altitudes, unless it is just a intermittent bad electrical connection 
> or switch. Do you have the same type of low fuel switch that I have ( 
> mine is green and floats in the sump tank)? I installed mine on the 
> pilot side of the sump near the top. I didn't quite understand your 
> description and thot maybe it was a different type switch. Are you 
> sure the warning light itself isn't just loose in it's socket?
>
> I'm trying to understand what changes at higher altitude that would 
> affect the low fuel switch. The only thing I could think of was that 
> atmospheric pressure drops, so the sump tank could possibly expand a 
> little I guess. Do you have a sump tank vent line and the main tank 
> vent lines per plans?
>
> I'm assuming that you have pretty much ruled out the possibility that 
> the sump tank is partially emptying and that the low fuel switch is 
> working properly? The only way I could see that happenning is if the 
> flow from the mains is somehow restricted due to inadequate venting, 
> and that the fuel pump is pulling fuel out the sump tank and the sump 
> vent line is letting in air into the sump lowering the fuel level.
>
> Chuck H
>
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