Marty d's CH-701 build log

[IBob]

I did not test my cooling system, but went looking for any leaks are drips following initial engine runs.

For fuel, the Facet pump has a non-return valve. I did my initial runs with wings off, so had the fuel return line blanked off, and that part of the system held pressure on the steam gauge after the pump had been run then turned off. (Incidentally, on normal prestart you are looking for that pressure to fall away quite promptly once the Facet pump is off: this tells you that the fuel return orifice is clear and doing it's job.)
I would be getting some gravity feed from wing height down into the receiver tank. Mine developed seepage from one of the tank top connectors and that wasn't evident until it began to wet the sides of the tank. So I would be looking hard at that area.

For the oil system, there is an essential Rotax priming procedure to push oil round the system after engine installation. This involves light pressurisation of the oil tank while turning the prop many times, and would allow you also to check for leaks.

[IBob]

I would not pressure test the wing tanks in situ, as they sit against the upper skin, and even minimal pressure will exert a considerable force, bugging out the top and the bottom of the tank.
I don't have the exact tank size, but eg: if it's 20" x 20" that's 400 sq inches. Give it 2PSI and that 800lb over that surface area....

[Marty_d]

Yes I wouldn't pressure test the tanks.  This is my question though, is it standard practice to pressure test the rest of the fuel system?

[Moneybox]

3 hours ago, Marty_d said:

Yes I wouldn't pressure test the tanks.  This is my question though, is it standard practice to pressure test the rest of the fuel system?

 

I doubt it but if it has an automotive type of pressure cap then and automotive coolant pressure tester would be an easy option. You only have to pressurise the system to the pressure stated on the cap.

 

Anywhere beyond the electric pump if you have one would be tested as soon as the pump is activated otherwise you could temporarily install an electric pump near the tank end so that all plumbing is tested.  

[Thruster88]

The best way to pressure test engine systems is to run the engine. This is what we do on all new or overhauled engine installations, aircooled lycons or liquid rotax. Have a second person double check all connections. First start cowl off have an observer. Stop engine check for leaks, repeat as necessary. 

[Marty_d]

Fantastic, thanks guys.

 

How about general logistics about starting... special equipment, ground etc?

 

What I mean is, my plane is currently in a farm shed.  The paddock in front of the shed slopes down slightly - there's no flat land.  Currently hosts a flock of duck.

My general plan is to roll the plane out til it's clear of the shed, shut the doors to avoid blowing everything around behind the plane, tie the main gear to trees/fenceposts, chock as well, put the wings back on and prep for starting.

 

Are there other considerations?  Is it best to peg down carpet under the plane or is that more of a risk than it's worth?  Guessing it's a good idea to rake away any gravel / sheep shit etc in front of and around the plane first also?

 

Any hints and tips would be appreciated, thank you.

 

 

[spacesailor]

The D. H. COMET was 'PRESSURE TESTED ' UNDER-WATER ', So as to hold the hull INTACT ! .

spacesailor

[rgmwa]

I wouldn't put carpet anywhere near the prop but definitely sweep away all the gravel from the area and anything else that's loose.  

[Blueadventures]

From your image face plane towards the big door. Have prop line just forward of the drain grate line.  Chock the wheels good, maybe even level up the lower main wheel. Add a double securing with rope or a strap to a secure point behind the plane so it does not travel forward when engine running.  This way you won't pick up any stones or rocks.

 

[Moneybox]

I was considering laying a bit of concrete or laying a area of artificial grass that is pegged down with sand laid in it. Here at Myrup, Esperance they have a circular patch of concrete, about 30m from the gravel airstrip, that looks like the top of a tank of some kind. It's about 3m across and does the job nicely.

Edited April 15 by Moneybox

[Marty_d]

5 hours ago, Blueadventures said:

From your image face plane towards the big door. Have prop line just forward of the drain grate line.  Chock the wheels good, maybe even level up the lower main wheel. Add a double securing with rope or a strap to a secure point behind the plane so it does not travel forward when engine running.  This way you won't pick up any stones or rocks.

 

Oh, thanks, but she's not in that shed. Up the road in a bigger one.

[Moneybox]

 

I realise now these are poured just for the purpose. Each taxi way has a runup pad like this.

[Marty_d]

Okay, it's a few months later, but finally ready to start the engine.  

Today with the help of some good friends I got the plane out of the shed, got the wings on and pounded in some star pickets to tie down to.

Tomorrow I will also tie the main gear back to a very solid post before trying a start.

I also made a control lock that I'm quite happy with.  That's locking up the rudder and elevators now, if the flaperons were attached it'd lock those too.  Will post photos of that later.

 

Any final words of advice?

 

[IBob]

Looking great, Marty!
I fired mine up with the cowls off, allows an observer to check for leaks during the initial run, I had a fuel leak at the splitter. Also for any pipework or wiring etc that is vibrating and requires further securing.

[facthunter]

Motors are best left inhibited.   Nev

[onetrack]

Marty, make sure you run the engine until the oil temperature is at normal operating range, where condensation is vapourised and removed from the engine internals. A huge amount of water is produced in the first few minutes of engine operation, and if any stays in the engine on shutdown, it will cause corrosion on any exposed steel components, after a further period of sitting around. 

 

One trick I learnt from some Americans is to leave a 100w incandescent globe lit up, under an engine sump, when an engine is left standing. The heat from the globe generates enough warmth to keep condensation at bay, especially where large temperature variations between night and day are experienced. This trick also works for keeping condensation off steel tools in cupboards and toolboxes.

[facthunter]

A gallon of Paraffinic fuel produces more than a gallon of water and you'll always get some in the Breather which in your case is the Oil return Pipe. Nev

[Marty_d]

Success! Well partial success.

First attempt I forgot the magneto switches, so it turned over for 5 seconds before I stopped. Luckily at that point I noticed fuel dribbling in the cabin from a loose hose clamp on the fuel pressure gauge.

A friend outside the plane also noticed fuel dripping from the lowest point - another loose connection on the header tank.

 

With these fixed, I tried again.

 

Engine started immediately and went to 2000 rpm. Tried throttling back to 1500 but it didn't drop much below 2000.

Then noticed the oil pressure hadn't risen so turned off.

 

Looks like I hadn't connected the wiring for oil pressure. Oil temp and CHT's were also zero so I will check those.

 

All that aside though, it was great to have it running! (And I did call "Clear prop!" just before the start of the video...)

 

 

[Blueadventures]

Nice, Better to run after start at 2,200 RPM or a little (2,300) faster; whatever seems smoother.  Below 2200 can lead to accumulated stress damage to gearbox clutches.

[Marty_d]

Thanks Mike!

 

Hey guys - question about the cooling system.

As per the manual I put 1.5 litres of coolant (50% green stuff, 50% demineralized water) in the metal reservoir with all the pipes coming out of it.

There's been no leaks in the system, no puddles under the plane, but even after today's run there's no coolant in the plastic overflow container (which has min/max lines).

Should I be worried about this? 

[IBob]

Excellent, Marty!
And Blueadventures is right. I think Rotax now reccomend initial warmup at 2200RPM, easing back to 2000RPM after some minutes. And mine always felt good at those cold to warm settings.
As for getting the oil temp up with a ground run, you may well have to blank off part of the radiator. The 912 is very slow to warm the oil regardless... 

[IBob]

Apologies if I've misunderstood:
You should have coolant already in the overflow, with the overflow pipe going down to the bottom of that.
I ran with my overflow about 50%full when cold.

As for this first run: you quite possibly had air in the system, so I would not expect to see coolant passing immediately into the overflow.

[Blueadventures]

1 hour ago, Marty_d said:

Thanks Mike!

 

Hey guys - question about the cooling system.

As per the manual I put 1.5 litres of coolant (50% green stuff, 50% demineralized water) in the metal reservoir with all the pipes coming out of it.

There's been no leaks in the system, no puddles under the plane, but even after today's run there's no coolant in the plastic overflow container (which has min/max lines).

Should I be worried about this? 

My method is fill engine and level will usually settle about 6 or so mm below the lip the cap seals to; I then fill the overflow / expansion tank to halfway between the low and high marks, plus this bottle needs a small hole in top cap and coolant line to engine at low point.

[Marty_d]

Thanks guys.

I will add more.

I don't know where the coolant went, as I said it was the recommended amount - but there's only a bit in the top metal reservoir, none in the plastic overflow, and the hoses all seem to be empty too.

And there's been no leaks.

[Blueadventures]

7 minutes ago, Marty_d said:

Thanks guys.

I will add more.

I don't know where the coolant went, as I said it was the recommended amount - but there's only a bit in the top metal reservoir, none in the plastic overflow, and the hoses all seem to be empty too.

And there's been no leaks.

Just add until full and record the quantity.  I take it your mixing water to concentrate??  I make sure I don't have more than 50% of the concentrate.  Also keep checking for any leak.  Most likely no leak just that your system needs more that 1.5 lts.