Help Wanted (with metal fuel line plumbing)

[Marty_d]

Oil pressure gauge on mine is electric from the sender on the motor.

Fuel pressure is still a pipe to the gauge though. 

@IBob, what size is the tube going from the reduced orifice to the fuel pressure gauge?

[IBob]

Marty, same size as the fuel return line orifice. I think we decided that is 0.35mm or thereabouts.

[facthunter]

THAT little feature really complicates things somewhat. Nev

[IBob]

How so, Nev?

 

[facthunter]

Because you have to take account of it  when flying with change tanks time and use fuel from the return tank if it's full and it you have a flowmeter it's less valid.  ALL this to keep a fuel. line cool. I like BOTH to be the tank selection on take off. Nev

[skippydiesel]

15 minutes ago, IBob said:

Thanks Skippy. I have a Facet Cube and no external bypass to that, so the Cube must allow free flow when not running: at a guess (and it is only a guess) perhaps when powered off the internals park themselves so as to allow free flow?

A minor detail with reference to your above diagram: ICP run the fuel pressure gauge via a small orifice, same as the return line. Presumably to limit the amount of fuel dumped in the cockpit if the gauge or plumbing spring a leak(?)

As I understand it the Facet (Boost) pump should remain open to through flow, when not energised(on) BUT should there be a malfunction and the pump cause a partial or total blockage,   the bypass will still slow fuel to be drawn by the mechanical/ engine pump (keeping the engine running).

 

In my case, I  don't seem to be getting sufficient flow ,under max engine power(low pressure reading), so hope that the addition of a bypass will  allow more fuel to the engine pump.

 

As for fuel pressure gauge - there is no need to have a capillary line, running from the fuel carburetor distributer, for pressure reading in the cockpit - can all be done using a 12 V pressure senor and a suitable gauge

 

[skippydiesel]

1 hour ago, old man emu said:

Ignore the measurement system  These parts are made to a standard. All you have to do is order the part by its designation, whether that be AN nnn-x, or MSnnnnnn, or even NASnnnnnn. 

 

It seems that the designation of aerospace components has changed again. This chart can help decipher designation codes: https://bandemfg.com/conversion.html 

 

So a the part called for in your manual is AN827, which changed its name to MS24396 and later, as it might be called for in a design done today, AS1036.

 

The 3/8" aluminium fuel line can be obtained from https://aeroflowperformance.com/af66-3000-3-8-alloy-hard-line-9-5mm, but Supercheap has it much dearer.

Thanks for that OME.

 

Just had a quick brown of the AirFlow very extensive  catalogue - WOW!!!

[skippydiesel]

Do you think this Ebay offering would do the fairing OK (claims to be 37 degrees)?

 

 $130 + $20 delivery https://www.ebay.com.au/itm/292610727741?hash=item4420f55f3d:g:DS0AAOxycD9TWPGM

[IBob]

19 minutes ago, facthunter said:

Because you have to take account of it  when flying with change tanks time and use fuel from the return tank if it's full and it you have a flowmeter it's less valid.  ALL this to keep a fuel. line cool. I like BOTH to be the tank selection on take off. Nev

All good points, and I wouldn't suggest it is without it's drawbacks.

 

Fortunately on the Savannah there are sight glasses on the inboard tanks (which is where the standard return goes to, RH).

 

And I can report this, on several occasions:
Prepare to start cold engine:
Turn on aux fuel pump, which runs at steady rate, watch fuel pressure rise  > 2PSI.
Turn off aux fuel pump, watch pressure fall (return line is clear).

Start engine etc and fly.
Land, taxi stop engine.
Prepare to restart warm/hot 5/10/15/20mins later:
Turn on aux fuel pump, which runs very rapidly for 5-10secs, then runs at steady rate and fuel pressure finally rises. Presumably expelling vapour via the fuel return (and carbs): vapour will pass through the return orifice much faster than liquid fuel, hence the rapid pump activity to start with, then the steady pump rate once all vapour is gone.

I have had this on a number of occasions, and I think it a very good feature in this type of aircraft. I would still not take off immediately, but I would say it goes a long way towards avoiding EFATO due to vapour lock.
 

 

[IBob]

17 minutes ago, skippydiesel said:

Thanks for that OME.

 

Just had a quick brown of the AirFlow very extensive  catalogue - WOW!!!

Skippy, I've been close to having a quick brown myself.......but more normally when flying.........😬

[Marty_d]

2 hours ago, IBob said:

Marty, same size as the fuel return line orifice. I think we decided that is 0.35mm or thereabouts.

Oh sorry, I meant the actual hose.  Yes the orifice is small but wondering what size line you run - 1/4 inch?

 

[IBob]

Cannot now recall, Marty, but that sounds about right: whatever fits at both ends.

[Blueadventures]

20 minutes ago, Marty_d said:

Oh sorry, I meant the actual hose.  Yes the orifice is small but wondering what size line you run - 1/4 inch?

 

Not sure if this answers you question; my return line is 3/16". Two reason can't mix up with the 1/4" from engine pump or to carbs, and cheaper to buy (only low volume returning to tank).  Cheers.

[facthunter]

The carburetter needle, float and bowl vent are quite capable of handling air bubbles . Fuel vapour is a function of excess Temperature and it disappears if the temp is lowered or the pressure increased. Using fuel to remove heat is hardly  a good way to do things. OIL and Paraffins are far less effective than water at removing heat. The problem is where the carbs and fuel lines are located. Heat rises and that's all above the motor. Isolation and insulation and Blast tubes of cold air would be better than having return lines and Bleed orifices in the main fuel supply. . Float carburetters should not be on a modern Aero engine but IF they are, then have them under or behind  the motor to keep them and the fuel feed lines cooler, shorter and more able to gravity feed.

[rgmwa]

2 hours ago, skippydiesel said:

Do you think this Ebay offering would do the fairing OK (claims to be 37 degrees)?

 

 $130 + $20 delivery https://www.ebay.com.au/itm/292610727741?hash=item4420f55f3d:g:DS0AAOxycD9TWPGM

Looks like a pretty decent set for the price. If it's 37 deg, should be fine. You can easily pay $250-$300 or more for a top brand.

 

Edit: Be careful. I zoomed in on the dies in the link and they have 45 deg stamped on them.

Edited May 3, 2023 by rgmwa

[IBob]

44 minutes ago, facthunter said:

The carburetter needle, float and bowl vent are quite capable of handling air bubbles . Fuel vapour is a function of excess Temperature and it disappears if the temp is lowered or the pressure increased. Using fuel to remove heat is hardly  a good way to do things. OIL and Paraffins are far less effective than water at removing heat. The problem is where the carbs and fuel lines are located. Heat rises and that's all above the motor. Isolation and insulation and Blast tubes of cold air would be better than having return lines and Bleed orifices in the main fuel supply. . Float carburetters should not be on a modern Aero engine but IF they are, then have them under or behind  the motor to keep them and the fuel feed lines cooler, shorter and more able to gravity feed.

Why is using fuel to remove heat hardly a good way to do things?

[Geoff_H]

I made an appropriate flaring tool and using a Bunnings gas lines and in the lathe made the end bit at the appropriate angle.  I have made an aluminium line for my air compressor, it holds 100psi air.  I will take pics and post them if anyone is interested.

Geoff

[facthunter]

A big flow will work but water would be a lot better (As a comparison). Fuel is used to cool the engine oil in JT8D P&W Jet motors  but that's a fair rate of flow through proper heat exchangers. HIGH POWER=s HIGH FLOW .More to cool the hotter oil like up to  A TONNE AN  HOUR. .  Nev

[facthunter]

Flaring AL tube doesn't do it for me. Sheet or thin AL  fatigues like mad and the flaring thins the metal I do a lot of flares on oil pipes for bikes and they give a lot of trouble. I only do them for originality.. Nev

[IBob]

The problem with lagging the fuel lines is that if they nevertheless become heat soaked, the only way to cool them is by running fuel through.
Blast tubes of cold air only work once you're running, and if you are heat soaked, the problem is already there.

 

It seems to me that most engines......most things.....contain compromises. Rotax certainly have those compromises, and in the case of the risk of vapour lock, I think they found a simple neat solution (albeit easier to build in than to retrofit).

[facthunter]

Do we not criticise Rotax because it is something super special apparently and no criticism is acceptable therefore. The court case that threatened the very existence of RAAus was concerning a 9 series Rotax crank issue. It's on CASA's files. (Ducks for cover).  Nev

Edited May 3, 2023 by facthunter

[IBob]

I've said my bit, Nev.

Sorry you seem to take it personally.
 

[Area-51]

Have just fitted a custom header tank with purge circuit and low level lamp on instrument panel to an airframe, and replumbed the entire fuel system with flexible braided teflon tubing and AN6 fittings; ended up being a real hassle free way to go and will last the life of the airframe... was sceptical when customer requested using this method but was pleasantly surprised in a good way.

 

Have also designed and hand fabricated hard plumbing in custom automotive; fuel, A/C, brakes, hp fluids.

 

Fabricating and bending hard lines is a real art; you really need to know your linear lengths for bends, and relative angles between bends too, and its all got to be calculated before making the first bend, otherwise stuff sometimes gets made again... and again... and again... stuff ups are great learning opportunities... matching siamese lines are the ducks guts of challenges.

 

Using a quality flaring tool is a must; otherwise don't even bother trying, all the work may amount to naught in the end otherwise.

 

Everything from EFI Solutions, available from Burleigh Heads store, or online store... very well priced and excellent quality materials; just measure, cut, put the end on...

 

the return restrictor i just used a thick nylon line, screwed the restrictor jet in and pushed it all down into the teflon line; a snug fit.

Edited May 3, 2023 by Area-51

[facthunter]

I Bob I haven't taken anything you said personally.. Nev

[skippydiesel]

21 hours ago, facthunter said:

Do we not criticise Rotax because it is something super special apparently and no criticism is acceptable therefore. The court case that threatened the very existence of RAAus was concerning a 9 series Rotax crank issue. It's on CASA's files. (Ducks for cover).  Nev

Nev - Where did, the sudden reference to Rotax 9's,  come from ? Bit "left field" my friend.

Edited May 4, 2023 by skippydiesel