uesful fuel Cobra trike

[Gompou]

Hi
Can anybody help me on the useful amount of fuel in a cobra trike. I know that the tank take ruffly 83 liters, but how much will be useful.
Thanks
Gompou

[Kingfisher]

When you fly every drop is useful,
When you run out while flying, the 20L in the hanger is useless

[Triker]

If one can afford it, fill up
rather too much then too little

[Gompou]

Hi all
If you want to calibrate your fuel level sender, it help to know what is useful and what not.
This was the reason for the question. Seems like nobody relay knows, and on the official site there is no info either
Gompou

[bobthebuilder]

"Useful fuel" would be tank capacity, less the amount of fuel in the hoses, pump and filter.
An "ARB" value really, beacuse if you try to plan your fuel to the last drop, you really are living on the edge.

[Gompou]

Hi
The fuel in the tank are suck from the top.There is always a amount of fuel left over that are not suck from the tank. There is no way that all of the tank capacity( in my case 83 l) can be use.If you take a pipe and suck out the fuel from above, there is still fuel left in the tank. I drain the fuel at the water traps, the lowest point in the tank, and there were still 12 l in the tank.I don't want to plan the fuel to the last drop, but with the fuel units available today, you can decide what would be zero. this give you the chance to left say 10 l in the tank and regard that as empty.You do your planing from there. I am sorry if the question actually sounds like I want to find out how long I can stay in the air.
A few manufacturers actually give a amount that they consider as not useful, therefor my question.
Gompou

[JACO]

Gompou, as part of my testing on the toyota i installed in my cobra, the CAA wants to know what the usefull fuel cap is, and they suggest the following test :

> This is a field test to ensure the aircraft engine will get enough fuel to run properly,
even if the aircraft is in a steep climb or stall attitude.

> Empty the aircraft's fuel tank completely.
> Place the aircraft's nose at an angle 5 degrees above the highest anticipated climb angle.
> Make sure the aircraft is tied-down and choked.
> Disconnect the fuel line to the fuel injection spreader chamber.
> Add a known amount of fuel to the empty fuel tank.
> Start the fuel pump, collecting the fuel that is pumped out, so that it can be measured.
> Note the fuel pressure gauge.
> As soon as the fuel pressure drops below the minimum required pressure to keep
the engine running, stop the fuel pump.
> Subtract the amount of fuel collected from the initial quantity of fuel added to the tank.
This will give you the unusable fuel quantity.

I'll be doing this test very soon now, since i am allmost finish with my testing. Will relay the results to you.

Jaco

[Gompou]

Hi Jaco
Thank you very much for your reply. Please let me know when you complete the test.
By the way, what would you consider to be the highest climb angle?
The manual give the follow. Max angle of pitch 30 degrees
Fly safe
Gompou

[Tailspin]

A way to also determine what is usable.
When i setup the fuel gauge on my Sunbird i was told that the gauge should show empty when there is about 10% fuel left in the tank so on a 50L tank there should be about 5L still left in the tank - I still have a 10L headder tank so when my fuel gauge hits empty i know i have about 40min before i get into Big dwang and the motor will go quiet.

When i am flying the Trike i have a line that when the fuel gets there then i know it is time to land - there is enough fuel to get me at least another 15min before i seriously start to get that Pucker effect.
I have attatched a pic of the last flight i took - the fuel was on the Bingo Line and that means it is time to Land - anything after this is playing with a live handgranade It will bite you in the ASS.

[Gompou]

Hi Tailspin
Problem with the Cobra trike is that you can't see your tank from the outside,not even on the ground. Behind the side covers. Only way is with a reliable fuel gauge and to use the time you fly. Have a dip stick that I have calibrated myself that I use before a flight, and a fuel-flow meter while in flight.Is a bit of a hassle not to visibly see the level. Got a Flight 2 instrument panel and the fuel gauge is quit accurate after calibration. Will pump out all the fuel myself to detect what is useful and what not.At this stage it does not look if any Cobra pilot can give me a answer. That by itself is quit alarming, or perhaps thy are not on the site.
Fly safe
Gompou

[nicow]

Gompou
I keep my fuel tank full,and only show 70lt on the fuel gauge,then there's always 10lt spare.

[CHARLIE WHISKEY]

Gompou
My leftover in my tank is exactly 1.25 liters.
This was established by lifting the nose almost like JACO suggested at 5 deg and running it dry. Ja, "tot hy vrek".
I've stripped my cobra bare to reach the tank and then "gooi" fuel in until i reached the empty mark on my analog fuel instr. I't showed on the last red stripe - 11.5 liters was meausured.
This was not enough for me so I oppend the Tank and setted the Float valve untill I've got 21.25 Liters in the tank AND AN INDICATION ON THE LAST RED STRIPE.

So now I know I've got exactly 1.5 Hours of flying to sorce fuel.
It took me a Saterday and a half to establish,but I'm happy my indication is correct.

[Gompou]

Hi Charlie Whiskey
This was actually the answer I expected to get in the beginning. Thank you very much. Is in the prosses of testing my own. Will post results here. By doing this I think that you will be much safer, simply because now you know and can make a informed decision like you have done.
Fly safe
Gompou

[Gompou]

Hi
Did my test today. Just under one liter left when the engine stop.
Recalibrate my fuel gauge and I am happy now that I know.
Fly safe
Gompou

[African Grey]

Some info:

The Cobra utilises 2 Fuel pickups due to the tank shape and lower keel.

Many moons ago, while doing circuits at Klip River, the engine on my Cobra (ZU-CNE) stopped abruptly giving myself and student "Nag Apie" Eyes....

The one pickup was blocked and the one side of the tank was bone dry with about 12 Liters still on the other side of the tank

While 45 min is required by law, I there after always had 15 L as a reserve.

Cheers