fuel gauge for Jabiru

[jetjr]

Could always use the low fuel float setup Jabiru use ?

Float switch through header tank wall hooked to light on dash

Install then drain tank i til it lights up, measure whats left until its empty

I reckon install was simple too, cut a small hole and glass in a new plate with switch in it

[naremman]

Just to be unhelpful -

 

The best fuel gauge for flying is:

 

Sight (dip stick or level tube) and a stop watch, combined with knowing your fuel consumption/hr for the operation type envisaged.

 

Unlike the host of elctro/mechanical systems - very unlikely to give a false reading

 

Skippy,

 

Whilst I am happy to endorse the general sentiment of you comments, any Victa Airtourer pilot will be happy to point out one of the exceptions.

 

The "donkey dick" fuel gizmo to determining (guessing) fuel contents in the fuel bladder of any Airtourer gives any pilot about to launch off no great degree of confidence what so ever. Coupled with an original fuel gauge not renown for the slightest degree of accuracy, fuel in/fuel required assumes a critical importance.

 

The ATSB focused on the Airtourer fuel quantity issue following a couple of notable bingles where no/low fuel had some devastating results.

 

I replaced the original fuel gauge in my Airtourer with a VDO automotive unit many years ago, and whilst not accurate over the entire tank range, it lets me have confidence when I am down to 20 litres, and gets me thinking being on the deck could be a good option.

 

Every aircraft will have its quirks. The challenge for us as pilots is to make ourselves familiar with them on the deck before launch rather than making it an in flight encounter.

 

I am reminded of a mate who built a lovely little Jodel and was part of a gaggle of WA Jodels heading to Mangalore in the early 1980's. His fuel gauge was a cork at the end of a piece of wire in the fuselage tank. They were doing a Caiguna to Ceduna leg which was going to stretch the legs of the Jodel. Not long after take off the cork and wire parted company giving a zero fuel indication. As time wore on concern mounted. and some close formation ensued on similar model Jodels attempting to work out their fuel status. All landed safely.

[Old Koreelah]

My Fuel Mizer has been totally reliable (after being set to tank dipstick readings). An extra precaution: switching tanks every half hour.

Have had fuel flow problems from negative tank pressure- caused by incorrect design of wingtip fuel vents.

[skippydiesel]

Skippy,

 

Whilst I am happy to endorse the general sentiment of you comments, any Victa Airtourer pilot will be happy to point out one of the exceptions.

.....................................................................

Ts time wore on concern mounted. and some close formation ensued on similar model Jodels attempting to work out their fuel status. All landed safely.

 

Thank you for your kind words.

 

In my case I have "calibrated" my automotive style fuel gauge by:

First stick a curved strip of paper on the outside of your gauge.glass

Determining max usable fuel - not hard just use your auxiliary pump to pump the last bit of usable fuel into a container. Then drain remaining fuel into a measuring/calibrated flask. The resultant (sump) figure should be subtracted from full/max fuel.

With tank empty & power on (gauge live) using a texter, mark position indicated by pointer on paper.

Using your measuring flask (or any other method of adding accurate quantities of fuel) add known quantities (I use 10 L increments). Mark position indicated by gauge pointer for each 10 L added. repeat until full fuel.

Subtract sump fuel from total fuel added for max usable fuel.

Checking calibration accuracy can then be done at each subsequent fuelling when known quantities are being added.

 

My fuel gauge has remained accurate for 10 years now however I am careful to only use it as a back up to my fuel consumption/time calculations.

 

For many years my fuel consumption calculator gauge worked remarkably well. This is no longer the case. Despise all my efforts I seem to be unable to restore consistent/accurate function - This gauge will be replaced in the not to distant future. This gauges accuracy "drift" is a good example of why a pilot should never rely on a single device for something as critical as fuel/flight time remaining.

[facthunter]

Why do you add fuel from the completely empty situation and mark that position? In an earlier post I advocated leaving the unuseable there and adding from that. Then you are always indicating fuel available to use which I think would be more useful. You are correct about not relying on ONE instrument or method.. Gauges are generally not recognised as an only source.. IF a gauge is not accurate or reliable it's not of great value. Many aircraft fuel gauges are poor at doing the job. Nev

[Markdun]

Bruce, Radiant make a cheap fuel gauge with a sender attached to the outside of a fibreglass tank. In my view you can’t have too much fuel remaining info, but if you are down to the last 10litres ie. the dregs, you ought to be finding a place to land rather than looking at a fuel gauge.

I was flying a delivery of a Tecnam from WA to the east coast and we had that very long leg from Kalgoorlie to Forest with a forecast of some headwind. It was an unknown aircraft to me so I figured the resistive analogue fuel gauges and the digital fuel flow s as rough guides only, particularly so as I had to have the LAME that ‘fixed’ the fuel tank leak by removing the evidence of the leak by cleaning the fuel stain, re-do the job. On filling the aeroplane for the first time I was rewarded with an avgas shower getting into the left seat. Anyway, on the flight to Forest every 15 minutes I did a quick calculation of estimated fuel burned and fuel remaining from our 100l full tanks at Kal and compared this to the 3 gauges on the panel and my flight plan. All pretty much correlated. It would have been nice if the previous owner had connected the RS232 serial output from the GPS to the fuel flow meter so I could have played a bit with airspeed to find the lowest fuel burn per nm. The owner/passenger in the right seat was a bit amused; there were plenty of airstrips to land at, but having to flag down a train and organise a refuel would take weeks. We arrived at Forest with over 35l remaining, mainly due to true airspeed cancelling out the light headwind.

[skippydiesel]

Why do you add fuel from the completely empty situation and mark that position? In an earlier post I advocated leaving the unuseable there and adding from that. Then you are always indicating fuel available to use which I think would be more useful. You are correct about not relying on ONE instrument or method.. Gauges are generally not recognised as an only source.. IF a gauge is not accurate or reliable it's not of great value. Many aircraft fuel gauges are poor at doing the job. Nev

Fair comment/advice Nev - I guess I thought it important to know total capacity and usable/unusable fuel. Your way would have arrived at a similar knowledge base without the need to know unusable fuel. Either way - it is important information for any pilot to know o their aircraft.

[Downunder]

The owner/passenger in the right seat was a bit amused; there were plenty of airstrips to land at, but having to flag down a train and organise a refuel would take weeks.

You'd be amazed the number of times the Forrest caretaker has had to run some jerry cans down the railway line road to aircraft and helicopters making precautionary landings at one of those strips......

Depending on how rutted and muddy the road is, you wouldn't be there too long...

[Bruce Tuncks]

My tank is the same as wideblue's I reckon. It is FRP, about 3mm thick. It is about 20mm off the fuselage skin so there is room underneath. In fact the outlet hose goes under the tank.

Yes I would like a warning at the 20 liter mark. I would toss up between an ultrasonic gauge and another 2 warnings, say at 10 and 5 liters.

There is a regulation about having 40mins of fuel as reserve and this is the 10 liters. At 5 liters left, you are really in "land right now" territory.

Over 20 liters, the level in the tank is visible and a gauge is not really necessary.

[Bruce Tuncks]

How do you connect those "liquid level " senders to an indicator light? I like the look of them , but as has been said, they may not work on avgas.

The reversing camera is a good idea too. My new car has one and I like it. It sure saves trying to swivel your neck through 180 degrees. Putting one behind the tank means that luggage in front might block it. If you put it too close to the tank it might not focus enough.

[RFguy]

Bruce, which particular liquid level sensor ? a liquid sensor with a go /no go output can have it wires taken back to the instrument panel, and can drive an LED, or an LED and a small relay if you need a aux set of relay contacts to also feed a single 'summary alarm ' light. And LEDs are available as you know in many colours, and many spray angles. Alot of the very bright LEDS only spray over a narrow angle (built in lens) .

 

* Don't forget, if you send the 12V down to the sensor , be sure to fuse that wire with its own fuse, or at least PTC, suitably rated for the cable and the sensor.

Always assume the possibility of the cable being crimped against a bit of metal, or the sensor going short circuit . The high temp aircraft wire can get rather hot at rating*.

 

Sometimes it is (also) useful to know if the fuse has blown. an LED and resistor across the fuse will light if the fuse is blown.

For low current scenarios I usually use Polyswitches (PTC fuse) to protect for a sensor short circuit. That PTC might be on an existing circuit... depends.... but you also want a fuseable fuse somewhere, just they take a long time to blow if the short circuit is not quite a short. . Fuses are for stopping fires. Rating them is always tricky. Take a look sometime at a standard fast blow fuse datasheet on how long it actually takes to blow for a specified overload.

Edited September 7, 2020 by RFguy

[RFguy]

have a look at page 3 of 4 of this fuse datasheet. this is a standard, glass fast blow.

https://au.mouser.com/datasheet/2/643/ds-CP-5sf-5sfp-series-1313110.pdf

 

a 5A fuse takes ~ 100 seconds to blow at 8 amps, 10 seconds to blow at 10 amps, 1 second at 20 amps

 

A ceramic loaded fuse usually is faster to blow for a specific overload current.

general info :

 

https://www.littelfuse.com/~/media/automotive/catalogs/littelfuse_fuseology.pdf

[Garfly]

Then there's Radiant's new ultrasonic model:

 

https://lp.constantcontactpages.com/cu/7QBAzef/RADIANTPFP?source_id=fc1cc74e-5377-4aaf-9298-78dcd33a6737&source_type=em&c=iDrHblELZk9dW8HwJWq32vXEb7Kfh8k7TUcXE5aaGdW2-EcGqeETHg==

[RFguy]

Have built many ultrasonic water tank sensors, they are highly dependent on the speed of sound in a changing atmosphere. but for something like this, where a few mm wont matteer for a tall tank, no big deal.

10 years ago I came up with a sensor that lives on the bottom of the tank and bounces off the surface liquid/air boundary. Patent applied for, provision grant but I never followed it up as the business that was involved in went a different direction. Why transmit through the fuel, and bounce off the air fuel boundary ? because the speed of sound in the liquid doesnt change much.

[Garfly]

RFguy, when Radiant claim as one of their ultrasonic probe's advantages:

 

"Features include: Small, aerodynamic size facilitates top mounting on fuel tank"

 

What do you think they mean? What's the point of its being aerodynamic? Are they suggesting wing-top use?

[RFguy]

yes wing top use, or fuel cap replacement ?

note: "Room temperature measurement precision: ±1 cm - so not really suited to shallow tanks.

"Temperature compensated" yes- must be, but the thing is the temperature inside the wing will be quite different to that outside the wing. and depends on how they measure the temperature of the air in the tank.....

[Bruce Tuncks]

Yep, that radiant thing looks good but it is too expensive for me. there is an Arduino ultrasonic thing too at about ten percent of the radiant price. Mind you, a ready-made thing would be a lot less work. And a meter on the panel would look good.

RF guy, the liquid level sender I was thinking of would be like the XKC-Y25-T12V which describes itself as a " non-contact liquid level switch"

You can buy 3 of them for about $30 from banggood. Would these each drive a led on the panel? I would imagine one at 20 litres, one at 10 and one at 5 or 6.

How do they work?

[RFguy]

How do they work ? depends. They may sense the presence of a dielectric , or they may sense a change of dielectric, or they may sens ea change in reflected IR light. could be any of those in a cheapie.

 

A dielectric in this case is anything other than air. like a liquid. if the FRP is too thick, it wont see the change.

you can get them for $10 in singles in the link I previously posted here. maybe buy one, see how it goes.