Fuel Gauge for Lower Tank

[boleropilot]

g'day All - with the trip to Cooktown still being planned and 0455 still having work done, I decided to look at a fuel gauge for the lower tank

 

the unit I bought is quite a nice (fully adjustable) unit with a 2 inch gauge, which I have mounted in the dash directly between the ASI and Altimeter - looks nice there, and I can't miss it

 

with my fuel system being set up with the top tank draining into the bottom one, the way it will work is that the gauge needle will start to move when the top tank is empty and the bottom one is starting to reduce

 

from that point I will consider that I have no more than one hour to fly to be safe and will set my timer accordingly

 

the gauge assembly was only $24 from eBay, the alloy plate to allow fitting of the sender unit in the valley at the top of the tank will be considerably more - it is being made locally (in the old Drifter factory!)

 

anybody interested in photos or more info, feel free to ask, happy to post more details here

 

Cheers

 

Dave aka BP

 

 

[boleropilot]

 

 

[boleropilot]

oops

 

 

[farri]

oops

G`Day BP, Better?

 

 

You have a new engine, WOW! which is it? At this point do you know how many liters per hour it`s likely to burn and what`s the capacity of the lower tank, please?

 

Frank.

 

 

[Bruce Tuncks]

That's just what I want for my Jabiru SK. But I'm asking a lot, the gauge has to be accurate at the empty end with a non-moving sender ( capacitance type I think ) plus I'm a cheapskate.

 

A vertical tube going into the fuel tank from the top. if fed by air, would build up pressure till it blew bubbles and then the pressure would stabilize at the fuel reading. Has this ever been done?

 

 

[boleropilot]

hey Frank - the engine is a blue head 582-99, 300 hours from new at a training school then refurbished/checked over by Richard Eacott - strangely, one of the pistons was slightly flatted on top, so he replaced both with a 'good pair' he had...

 

I would have to look up the capacity of the lower tank, 20 litres I think - tiny problem is the outlet to the pump being at the back - so if you're low on fuel, and you do a steep approach.....oops again!

 

as per figures I have been given before (I never tested mine) the consumption figure is 15 litres/hour, but that takes into account taxi and climbout - in cruise it should be about 12 ?

 

BP

 

 

[M61A1]

The later belly tanks hold about 40l, about 15 of which is unusable. Best putting in a transfer pump and feed the engine from the top tank where the engine pick up almost every last drop. That is also good on a trip, so that if you hole your belly tank on takeoff from a rough strip, you won't lose all your fuel.

 

 

[Head in the clouds]

That's just what I want for my Jabiru SK. But I'm asking a lot, the gauge has to be accurate at the empty end with a non-moving sender ( capacitance type I think ) plus I'm a cheapskate.A vertical tube going into the fuel tank from the top. if fed by air, would build up pressure till it blew bubbles and then the pressure would stabilize at the fuel reading. Has this ever been done?

Yes, it's the standard way of determining the head/make-up rate of a borehole.

 

 

[Head in the clouds]

The later belly tanks hold about 40l, about 15 of which is unusable. Best putting in a transfer pump and feed the engine from the top tank where the engine pick up almost every last drop. That is also good on a trip, so that if you hole your belly tank on takeoff from a rough strip, you won't lose all your fuel.

15 litres unusable? i.e. 37% seems a bit much. Maybe you meant 1.5lts?

 

I agree about pumping up to the top tank and feeding the engine from there, that's how my Drifter was. My main concern is the pressure in the bottom tank. If the top feeds unrestricted to the bottom tank then when the top tank is full there's a head of about 700ml, that's quite a tall tank so the internal pressure in the lower tank will be quite high. Then apply 6G and you're looking at a head of 6x700 = 4.2m! Those belly tank tops are just glued to the bottom half and I don't think they were ever intended to take that kind of pressure. You'd want to use 'very' decent fuel lines and connectors too, for the same reason. And any bulging of the lower tank could break the mounting straps or their attachments.

 

At the least, it would pay to pressure test the system by filling both tanks and also filling a 4m high tube connected to the breather perhaps and check that the bottom tank can take the pressure.

 

 

[M61A1]

I've had engine surge due to starvation with a nose down attitude on decent with 15 litres in the belly tank. If you keep the nose up then you can use probably down to 1.5l.

 

 

[Kiwi]

Here is a photo of my fuel gauge for the bottom tank.

 

 

Works great.

 

 

[boleropilot]

yeah, great for young fellas with good eyesight...my poor old eyes always had a problem reading that little mirror on my left wheel cover - maybe I just should upgrade to a bigger mirror...

 

bp

 

 

[farri]

hey Frank - the engine is a blue head 582-99, BP

Dave, The only bottom tank I`m aware of holds 40 lts... I decided to drain the top tank into the bottom and take the fuel from the bottom; the first thing I did when I got my tank way back when was to modify the outlet hose barb; I took the barb out, sweated the strainer off if, soldered it onto a copper pipe, cut the pipe the correct length so that the pick-up point would be in the center of the tank and soldered the other end onto the barb, this increased the amount of usable fuel with a nose down attitude but wouldn`t overcome starvation when the fuel quantity got low enough... I never once let it get low enough and never had a problem with my setup.

 

I ran my grey head 582 with the standard carby jest they came with and I was using an average 12 lts phr! When doing cross country, I would flight plan for 14 lts phr.

 

Frank.

 

 

[boleropilot]

hey K1W1, do you know the quantities of the two tanks ? also, what is your setup for connecting the two tanks - I can't see me flying more than 2 or 3 hours on the trip to Cooktown...gonna put 2 x 10s of fuel on the back seat

 

I was kinda fooling with the idea of a tap at the cockpit for choosing UP, DOWN, BOTH or OFF....a bit overkill, methinks

 

as far as the pickup point for the lower tank is concerned, the guys in the old Drifter factory have a lot of experience with fuel tanks so it wouldn't be hard to change it

 

on the subject of making changes, I (foolishly) bought a wonderful new battery for 0455 without checking the weight - it's 5.2 kg - now I am looking at similar output Lithium Polymer units that weigh less than 1 kg !!!

 

anybody used a Lithium battery? I know they have (had) a bad reputation in RC modelling, where (if mishandled) were prone to flying off across the workshop - on fire !!!

 

BP

 

 

[M61A1]

hey K1W1, do you know the quantities of the two tanks ? also, what is your setup for connecting the two tanks - I can't see me flying more than 2 or 3 hours on the trip to Cooktown...gonna put 2 x 10s of fuel on the back seatI was kinda fooling with the idea of a tap at the cockpit for choosing UP, DOWN, BOTH or OFF....a bit overkill, methinks

as far as the pickup point for the lower tank is concerned, the guys in the old Drifter factory have a lot of experience with fuel tanks so it wouldn't be hard to change it

 

on the subject of making changes, I (foolishly) bought a wonderful new battery for 0455 without checking the weight - it's 5.2 kg - now I am looking at similar output Lithium Polymer units that weigh less than 1 kg !!!

 

anybody used a Lithium battery? I know they have (had) a bad reputation in RC modelling, where (if mishandled) were prone to flying off across the workshop - on fire !!!

 

BP

The total is about 70-72 litres. I have 2 of these: 20 Litre Jerry Can - Liquid Containment Bladders & Liners – Fuel, Water, Petrol, Diesel, Water Storage both of them fit between the top tank and the brace. Although if you are using them for carrying fuel in flight, as opposed to using them to get fuel in town, a standard 20l plastic jerry fits well in the back seat secured by the harness, and usually comfortably hold 24l with some air gap.

Using a lithium battery will depend on whether or not it has built in charging circuits that can cope with the rotax clipped peak type regulator /rectifyer, as without it you will find yourself on fire fairly quickly.

 

 

[cherk]

on the subject of making changes, I (foolishly) bought a wonderful new battery for 0455 without checking the weight - it's 5.2 kg - now I am looking at similar output Lithium Polymer units that weigh less than 1 kg !!!

anybody used a Lithium battery? I know they have (had) a bad reputation in RC modelling, where (if mishandled) were prone to flying off across the workshop - on fire !!!

 

BP

No,No,No.....................NOT Lith.Poly.!!! (LiPo) LITHIUM IRON !!!!!! (LiFe)

 

 

[farri]

I was kinda fooling with the idea of a tap at the cockpit for choosing UP, DOWN, BOTH or OFF....a bit overkill, methinks BP

Maybe not overkill but I wouldn`t recommend it! just something else to go wrong.

 

I created a forced landing in my home built by mistakenly turning the wrong tap and cutting off the fuel! Once should have been enough, but no! I had to go and do it again! Second time at 1300` agl, this time I quickly realised what I`d done, no problem methinks, plenty of height and electric start, I turned the engine over a few times, didn`t start and the battery went flat! I forgot to prime the Carbies! Now I was committed to land.

 

Frank.

 

 

[Kiwi]

Hi Dave,

 

Top tank just over 30 litres and bottom tank 40 litres.

 

I plan on 20l per hour, and usually burn under 15 lph.

 

I know it can burn 20lph as that what I used going from Gatton to Boonah once while been chased by a thunderstorms.

 

I feed from the bottom tank, I know it goes quite on a glide approach at 8.2 litres but on climb out you can use almost all of the fuel.

 

Kiwi

 

 

[boleropilot]

thanks m8 - you wouldn't want to be chased by the storm we got here yesterday - you wouldn't have outrun that sucker - the rain was horizontal and we got 40mm in about 10 minutes

 

then we sat out on the (north facing) verandah and watched the lightning show for about an hour

 

re. fuel - if I plan on 60 litres usable I can expect 4 hours (in good conditions) = 220nm = about as far as I would want to go in one day anyway - most of the time I will be doing around 3/4 of that...

 

BP

 

hey Cherk - thanks m8 - will make sure it's LiFe - and I will check on the charging circuits too (thanks M61)