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FloScan sensors; which model?

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frans(at)paardnatuurlijk.
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Posted: Mon Oct 06, 2008 11:17 pm Post subject: FloScan sensors; which model?

I'm about to finish the fuel system. Part of the installation are two floscan sensors. I have the 'A' models, suitable for a flow of 0.2 to 30 GPH. I just realised that although the consumption of the Rotax 914 is well within the lower part of the range of these sensors, the total flow is near, or possibly exceeding, the limits of these sensors. Near their upper limit, they exhibit a pressure loss of 2.6 psi, and since the pressure of the fuel-over-airbox is about 6 psi, this looks significant.



Has anyone used these sensors with a 914? Should I exchange them for the bigger sensors, which are capable of dealing with 60 GPH, and generally exhibit half the pressure loss?



Frans

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g-iani(at)ntlworld.com
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Posted: Tue Oct 07, 2008 12:47 am Post subject: FloScan sensors; which model?

Frans



G-IANI has the 914 and two Floscan 201A-6 sensors.  By the way the "A" tells

you it is the light weight aircraft model.  The B and C models have higher

flow capacity and weight a lot more.



At full boost the 914 takes 28 LITRES per hour so well within the rang of

the sensor.

Ian Rickard G-IANI XS Trigear, 200 hours

Europa Club Mods Rep (Trigear)

e-mail mods(at)europaclub.org.uk   

   or direct g-iani(at)ntlworld.com

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josok-e(at)ukolo.fi
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Posted: Tue Oct 07, 2008 1:09 am Post subject: FloScan sensors; which model?

Hi Frans,



The maximum consumption of a 914 is below 25 liters per hour. So whatever pressure loss occurs at 120 l/h is not important. The lower sensivity on the other hand is important, because running idle will bring the consumption close to the lower limit, and so introduce a fault in the fuel totaliser. The 914 has its own fuel pressure regulator, to compensate fuel pressure to airbox pressure. A slight drop in the feed line will be compensated for. 

I had a button to remove the input from the return Flow sensor from the fuel totaliser. In the checklist procedure after engine  start, pressing the button gave me a reliable impression of the state of the filters, pumps and lines. 



Regarards,



Jos Okhuijsen

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frans(at)paardnatuurlijk.
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Posted: Tue Oct 07, 2008 3:04 am Post subject: FloScan sensors; which model?

G-IANI wrote:

 	  Quote: 	
		   At full boost the 914 takes 28 LITRES per hour so well within the rang of

 the sensor.


	


If there were no return line, yes. But if the whole system pumps 120

litres per hour, the first flow sensor sees 120 litres passing, and the

one in the return line sees 92 liters passing. The consumption is then

28 litres indeed, but this is not what is actually flowing through the

sensors.



Hence my question whether the flow sensors are not a little bit on the

small side.



Frans

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frans(at)paardnatuurlijk.
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Posted: Tue Oct 07, 2008 3:05 am Post subject: FloScan sensors; which model?

josok wrote:

 	  Quote: 	
		   

 

 Hi Frans,

 

 The maximum consumption of a 914 is below 25 liters per hour. So

 whatever pressure loss occurs at 120 l/h is not important.


	


It is, because this is what could be flowing through the sensor at that

moment.



 	  Quote: 	
		   The lower

 sensivity on the other hand is important, because running idle will

 bring the consumption close to the lower limit,


	


If I understand it correct, the amount of fuel flowing through the

sensor is depending on the fuel pump, not the actual consumption of the

engine.



 	  Quote: 	
		   I had a button to

 remove the input from the return Flow sensor from the fuel totaliser.


	


Ah, and what did you see then? Of course this button did not change the

amount of fuel flowing, but the value you were seeing when pressing the

button would probably be a lot more than the acutal consumption of the

engine, right?



Frans

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davidjoyce(at)doctors.org
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Posted: Tue Oct 07, 2008 6:03 am Post subject: FloScan sensors; which model?

Frans, My 914 with JPI 450 and 2 Floscan 201 A6 (PN201-031-00) transducers 

actually consumes 30 l/hr at 164 knts/5500RPM/34.7in MP at 6500ft. Part of 

the testing to satisfy the PFA/LAA involed fuel flow tests by disconnecting 

the return hose and seeing how much came out with one or 2 pumps going. I 

can't find the work sheet with the precise figure, but I know the answer 

came out at something like 2 and a bit l/min and my inspector was entirely 

happy. The actual flow rate is of course regulated largely by the pressure 

release valve. My reading before fitting these transducers convinced me that 

they were the gold standard, fitted to the bulk of certified aircraft that 

have fuel flow systems. Regards, David Joyce, G-XSDJ

---

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frans(at)paardnatuurlijk.
Guest

Posted: Fri Oct 10, 2008 11:34 am Post subject: FloScan sensors; which model?

Today I finished the fuel system plumbing, so I decided to put some fuel in the tank and do some testing.



I can't run the engine yet as I have not finished the engine installation completely, but of course I can run the fuel pumps and measure the flow and pressure.



The fuel flow system, setup as a "sensor 1 minus sensor 2" installation, indicates zero fuel consumption, which is correct of course, as the engine is not running. However, if I connect the sensors individually, they indicate that 130 liters per hour is flowing, about the maximum these fuel flow sensors can handle. The fuel pressure is ok, according to the fuel pressure gauge I have installed.



With both pumps on (I have them in series) the flow increases to over 140 liters per hour, and the pressure goes slightly over the red line as indicated on the "fuel over airbox pressure" gauge. Do I have a problem here?



I still feel that the floscan sensors are used on the edge of their upper range, but so far the pressure loss does not seem to be significant. Actually I have a little too much pressure with both pumps running. The carbs don't spill any fuel though, so I guess it is ok. Any comments on this?



Frans

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rparigor(at)suffolk.lib.n
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Posted: Fri Oct 10, 2008 12:09 pm Post subject: FloScan sensors; which model?

Hi Frans 



"With both pumps on (I have them in series) the flow increases to over 140

liters per hour, and the pressure goes slightly over the red line as

indicated on the "fuel over airbox pressure" gauge. Do I have a problem

here?"



First off understand that Airbox pressure is in absolute terms. The

pressure coming out of a fuel pump if you measured it would be over

ambient pressure.



That said, I hope did not add confusion, but you really should follow

Rotax manual procedure to test if you have between ~2 and 5PSI over airbox

under worst condition. Worst condition of course would be when you are

flying in thin air where the fuel pump/s need to work overtime. 



Rotax simulation of thin air is to fool fuel pressure regulator into

thinking you are at a high altitude and you then need to be able to meet

minimum differential pressure.



OK this is the most critical meeting worst case for chance of not being

able to deliver fuel thus you will run out of fuel.



Next scenario is in thicker air. The fuel pressure regulator works based

on flow. It is calibrated based on a maximum amount of resistance return

flow of fuel will have going back to tank. If you increase resistance of

return flow, your regulator will be fooled into delivering a higher fuel

pressure over airbox pressure. Just a note, I was supplied with my Kit and

FWF 90 degree fittings that some were not too restrictive, some were poor

at best! A simple blow through test will tell the tale by the sound. Same

goes for straight nipple fittings, try not to use restricting fittings.



To answer your question as direct as I can---------perhaps.



Is your differential fuel pressure gauge really telling the proper tale?

Gauges are notorious for having error.

If you had parallel pumps, turning both on would in most cases blow well

above 5 PSI, Rotax does not recommend that, but plenty of folk seem to

have good results. I would be not tremendous concerned if next test I

mention proves the same under both circumstances.

Check your return line, better yet let fuel pressure regulator pee into a

pail with a non restrictive hose, if pressure within limits, then if you

reconnect your return line and pressure goes up, go after a less

restricting design.

Do test as per Rotax under worst case by cheating fuel pressure regulator

into thinking you are at altitude.



Good Luck.

Ron P.

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