Marty d's CH-701 build log

[skippydiesel]

2 hours ago, BrendAn said:

you can buy good electric petrol pumps cheap now. make yourself a trolley with a drum on it then no more holding cans up.

Couldn't agree more BrendAn. The Forum had this debate, what 2-3 years ago? Some good solutions/designs were offered then. Back then a suitable 12V,  vane pump and hoses could be had for about $80 (never had mine on a trolly/cart, so dont know the cost for this innovation).

 

The thought of those good old boys, teetering on a stand, while pouring even a 10 L fuel drum, into their high wing, makes my stomach turn.

 

PS: Still using my 10 year old Bunnings Aerospace plastic "jerry" cans. Cheapest I could find at the time - don't seem to be degrading in any way (fingers crossed)

Edited October 7 by skippydiesel

[bexrbetter]

This thing flying yet?

[Thruster88]

58 minutes ago, bexrbetter said:

This thing flying yet?

Hi Bex, Is your thing flying yet?

[Marty_d]

4 hours ago, bexrbetter said:

This thing flying yet?

Nah. But I did install the seatbelts recently, so it's even safer to sit in.

[onetrack]

Bex's revolutionary, world-beating aircraft design, is still in the investor rip-off stage. 😄

[facthunter]

He's NOT Robinson Crusoe there.  Nev

[Moneybox]

 

I can see light at the end of the tunnel, can't be too long now 😀

[Marty_d]

Help needed!

 

I'm at the point of testing the fuel system.  It'd be great to get some advice about how to go about this.

These are my thoughts so far:  (note - all filling of tank and back to containers through Mr Funnel to remove any contaminants)

 

Test 1:  From tanks to splitter

• Visual inspection of all fuel lines from tanks to carbs.
• Check of all quick release fittings to ensure engaged and open.
• Check tanks to ensure no debris/insects/whatever.
• Prepare aircraft (tyres to correct pressure, sitting level, towels on wing roots just in case of spill).
• L + R fuel taps off.
• Put an initial small amount (5 litres?) in each tank and check for any leaks from tanks to fuel taps.
• Cockpit fuel tap off.
• Turn L + R taps on and go under plane to check header tank fills correctly.
• Check for any leaks from header to cockpit tap.
• Disconnect line that runs from Rotax mechanical pump to the 5-way splitter.  Put the end in a new bucket with litre graduation marks.
• Turn cockpit fuel tap on.
• Check that fuel drains with no leaks into the bucket and time it to get flow rate.

Test 2:  To carb ends

 

      As above, plus:

• Increase amount of fuel to say 10L per tank (beware of bucket capacity while draining)
• Connect line back to the splitter but disconnect the carb ends; drain to 2 buckets
• Check for any leaks in the system - including in cockpit (line to fuel pressure gauge)

Test 3:  Electric pump

• Put 10L in each tank and open all taps.
• Test the electric fuel pump - measure flow to the buckets.
• Check that fuel is being delivered evenly to each carb end.

Test 4:  Fuel pressure gauge

• Reconnect carbs.
• Put 10L in each tank and open all taps.
• Check that the fuel pressure gauge on the panel is registering pressure.

Test 5: Full tanks

• Top tanks to full (without spilling)
• Check for leaks throughout entire system
• Check fuel pressure gauge
• Drain from header drain (lowest point in system) to fully drain.

 

Any thoughts?  What am I missing?  Is the testing order right?  Are there other tests I need to do? 

Is the full tank test really necessary?  (Just thinking - that's 77 litres of petrol, and both our cars are diesel...)

All assistance gratefully received.

 

Cheers, Marty

[IBob]

Marty, that seems very comprehensive. Just some notes:
1. My receiver tank developed a leak from one of the upper fittings: the tank came with fittings in place and I had omitted to check they were tight. The leak did not occur initially and required removal of some plastic round the fitting to remedy. Almost certainly a one-off, but I suggest checking for any dampness on or round the tank during initial trials.
2. The electrical aux fuel pump should give you at least 2PSI once the carbs are full. I did my initial engine runs without wings, with the fuel return line blanked off. Since the pump has a non-return valve, the system maintained the 2+PSI with the engine off when the pump was run then turned off. With wings on and the return line connected, engine off, the aux pump should still give you 2+PSI but this will drop to 0PSI once the pump is turned off: this indicates that your return orifice and pipe are clear and functioning correctly.

I did not top my tanks off, just used enough fuel to to flood the receiver tank etc and test for adequate flow. The aux pump delivered 1.2L/min.

Assuming you have the Savannah receiver tank (?), the early Savs had no tank vent there. The result was that small amounts of air could become trapped in the upper tank and would give false 'tank low' indications. Typically this would occur when climbing to altitude, as the trapped bubble expanded. Later Savs fixed this by running a vent line from the tank top to the upper LH wing tank.

 

[IBob]

While I can't claim to know about fuel systems on other types, it seems to me the 701/Savannah setup is well thought out and functions very nicely:
The 6L receiver tank with level switch buffers any momentary unporting of the wing tanks, while giving 15minutes of early warning of fuel exhaustion.
And the fuel return (via orifice) addresses the problem of vapour lock.

 

[Moneybox]

Maybe not what you're asking but what about checking calibration of the fuel gauge while you're at it?

[facthunter]

As far as I know In Basic aircraft, the only fuel gauge you can calibrate is one where the fuel level is marked on the side of the container and  drain all Useable fuel and add known amounts and mark it at intervals.. As a general rule fuel gauges cannot be relied upon to be that accurate and can NEVER be used as a determination of fuel on board at the commencement of a flight without other back up.  Nev

[Thruster88]

Calibration is done with a correction card, like a compass card. 1/4 =20litres etc.

[facthunter]

I'm sure we've all had fuel gauges where the LAST 1/2 disappears faster than the First half. (Hinged float arm).. In practical terms there's little you can do about it. With long thin wing fuel tanks, readings are all over the Place. You just rock the wings to see if there's still some fuel there.  Your main consideration is How much you started with. How long you have been in the air and what your proven fuel consumption IS.. Based on use in practice and recorded over a considerable period or the POH figures .   Nev

[Marty_d]

Actually don't have a fuel gauge.

Tempted to try those sensors that stick on the outside of the tank and have an LED when there's no liquid at that level.

Until then, it's a matter of calculation and of course the low fuel indicator when the header tank is the only fuel left (15 minute warning).

[Marty_d]

5 hours ago, IBob said:

Marty, that seems very comprehensive. Just some notes:
1. My receiver tank developed a leak from one of the upper fittings: the tank came with fittings in place and I had omitted to check they were tight. The leak did not occur initially and required removal of some plastic round the fitting to remedy. Almost certainly a one-off, but I suggest checking for any dampness on or round the tank during initial trials.
2. The electrical aux fuel pump should give you at least 2PSI once the carbs are full. I did my initial engine runs without wings, with the fuel return line blanked off. Since the pump has a non-return valve, the system maintained the 2+PSI with the engine off when the pump was run then turned off. With wings on and the return line connected, engine off, the aux pump should still give you 2+PSI but this will drop to 0PSI once the pump is turned off: this indicates that your return orifice and pipe are clear and functioning correctly.

I did not top my tanks off, just used enough fuel to to flood the receiver tank etc and test for adequate flow. The aux pump delivered 1.2L/min.

Assuming you have the Savannah receiver tank (?), the early Savs had no tank vent there. The result was that small amounts of air could become trapped in the upper tank and would give false 'tank low' indications. Typically this would occur when climbing to altitude, as the trapped bubble expanded. Later Savs fixed this by running a vent line from the tank top to the upper LH wing tank.

 

Thanks Bob.

I'll have to check the vent, not sure if mine has one on the header tank or not.

[fallowdeer]

AC90-89C.  Minimum fuel flow for pressurized fuel systems 125% of maximum consumption rate, 150% for gravity.  

A 912ULS will consume @ 28l/hr full throttle so you need a minimum of over 40l per hour, my build delivered over  60.

 

This test will need to be notated in the logs if your paperwork requirements are similar to that required in NZ, which are basically copied from the US FARs.

[Moneybox]

6 hours ago, Marty_d said:

Actually don't have a fuel gauge.

Tempted to try those sensors that stick on the outside of the tank and have an LED when there's no liquid at that level.

Until then, it's a matter of calculation and of course the low fuel indicator when the header tank is the only fuel left (15 minute warning).

 

I have a fuel gauge but I don't think I can dip the tank so I drained it, put ten litres in and took a photo of the gauge and then put another ten and did the same. I won't know until I get flying how the fuel consumption goes. I'm told it's 15-18L and hour. I have to take a look at prop adjustments because I opened the throttle for the first time the other day and it was heading beyond the red line. A mate (expilot) said just put the pitch adjustment on a couple of clicks but of course that won't work unless I have the time and remember to do it. I think there'll be a simple pitch adjustment but I haven't looked into it yet.

[rgmwa]

I don't know what prop or pitch adjustment method the Sportstar has, but on the RV-12 we're told to try to get the blades set to within 1/10 of a degree of each other. I use a digital level and bracket that clips onto the prop. 

[Moneybox]

 

This is my prop Kaspar KA-1/3PA 1600mm. The hand operated controller pushes the centre forward rotating the blades but I haven't found how to set the minimum pitch to prevent over maximum revs.

[Moneybox]

4 hours ago, rgmwa said:

I don't know what prop or pitch adjustment method the Sportstar has, but on the RV-12 we're told to try to get the blades set to within 1/10 of a degree of each other. I use a digital level and bracket that clips onto the prop. 

 

I guess you remove the prop and place it horizontal on a table? I was hoping for a simple threaded adjustment but I fear it might be a case of unscrewing those little cap screws clamping each blade. I can't find the info online so I might have to write to Kaspar.

[rgmwa]

My prop is a Sensenich ground adjustable and pitch is set while it’s on the plane. Your looks quite different but I’m sure someone here will know how to adjust it.