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rowlandcarson(at)gmail.co
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 Posted: Thu Nov 28, 2013 3:51 am Post subject: sight gauge alternative |
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I was originally going to use Tony K's conditioning and display circuit. Tim Houlihan had planned to do the same, but we couldn't get the various bits to behave sensibly (RS-232 & Windows issues, as I remember). Tim switched allegiance to the MGL display device and got another friend to design a conditioning amplifier to interface the the RS sensor to it.
I've now adopted the same approach and attached are some PDFs and a JPEG that show what I did (op-amp circuit, stripboard layout, MGL wiring, sensor & amplifier in box). As it's not installed yet, I can't offer proof of function but I know Tim's works fine. The only potential problem is ram air pressure on the forward-facing tank vents causing change of reading with airspeed. I intend to avoid that by using Graham Singleton's vent arrangement.
in friendship
Rowland
| Rowland Carson ... that's Rowland with a 'w' ...
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grahamsingleton(at)btinte
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| Posted: Thu Nov 28, 2013 4:40 am Post subject: sight gauge alternative |
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Rowland
isn't my vent system effectively the same as the factory setup? There will still be a +ve pressure on the tank.
Graham
From: Rowland Carson <rowlandcarson(at)gmail.com>
To: Europa e-mail list list <europa-list(at)matronics.com>
Sent: Thursday, 28 November 2013, 11:50
Subject: sight gauge alternative
I was originally going to use Tony K's conditioning and display circuit. Tim Houlihan had planned to do the same, but we couldn't get the various bits to behave sensibly (RS-232 & Windows issues, as I remember). Tim switched allegiance to the MGL display device and got another friend to design a conditioning amplifier to interface the the RS sensor to it.
I've now adopted the same approach and attached are some PDFs and a JPEG that show what I did (op-amp circuit, stripboard layout, MGL wiring, sensor & amplifier in box). As it's not installed yet, I can't offer proof of function but I know Tim's works fine. The only potential problem is ram air pressure on the forward-facing tank vents causing change of reading with airspeed. I intend to avoid that by using Graham Singleton's vent arrangement.
in friendship
Rowland
| Rowland Carson ... that's Rowland with a 'w' ...
| <rowlandcarson(at)gmail.com (rowlandcarson(at)gmail.com)> http://www.rowlandcarson.org.uk
| Skype, Twitter: rowland_carson Facebook: Rowland Carson
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[img]cid:1.1268568744(at)web87704.mail.ir2.yahoo.com[/img]
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rowlandcarson(at)gmail.co
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| Posted: Thu Nov 28, 2013 5:11 am Post subject: sight gauge alternative |
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On 28 Nov 2013, at 12:40, GRAHAM SINGLETON wrote:
| Quote: | isn't my vent system effectively the same as the factory setup? There will still be a +ve pressure on the tank.
|
Graham - thanks for pointing that out. Until now, I hadn't noticed the forward-pointing section at the end of the ultimate vent in your diagram as posted here yesterday. I had assumed the vent would finish with a section pointing vertically down (somewhere in the flap root area?) so as to generate neither positive nor negative pressure, but probably cut off at an angle to prevent whistles.
in friendship
Rowland
| Rowland Carson ... that's Rowland with a 'w' ...
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peterz(at)zutrasoft.com
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| Posted: Thu Nov 28, 2013 5:39 am Post subject: sight gauge alternative |
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I would suggest updating the cct/system to work on proper differential pressures - then venting isn't an issue. Ideally it would also incorporate a g-sensor such that a prolonged turn doesn't affect the fuel level reading (assuming there is some shorter duration filtering to deal with turbulence), and a switch to select avgas/mogas densities. I was planning on implementing such a system when the time came. I was also planning on a vertical aluminum tube gauge on the outside of the tank containing a magnetic float which triggered external level switches lighting up a simple led gauge - as a backup and in lieu of the sight-gauge.
Cheers,
Pete
A239
On Thu, Nov 28, 2013 at 8:11 AM, Rowland Carson <rowlandcarson(at)gmail.com (rowlandcarson(at)gmail.com)> wrote:
[quote]--> Europa-List message posted by: Rowland Carson <rowlandcarson(at)gmail.com (rowlandcarson(at)gmail.com)>
On 28 Nov 2013, at 12:40, GRAHAM SINGLETON wrote:
> isn't my vent system effectively the same as the factory setup? There will still be a +ve pressure on the tank.
Graham - thanks for pointing that out. Until now, I hadn't noticed the forward-pointing section at the end of the ultimate vent in your diagram as posted here yesterday. I had assumed the vent would finish with a section pointing vertically down (somewhere in the flap root area?) so as to generate neither positive nor negative pressure, but probably cut off at an angle to prevent whistles.
in friendship
Rowland
| Rowland Carson ... that's Rowland with a 'w' ...
| <rowlandcarson(at)gmail.com (rowlandcarson(at)gmail.com)> http://www.rowlandcarson.org.uk
| Skype, Twitter: rowland_carson Facebook: Rowland Carson
| pictures: http://picasaweb.google.com/rowlandcarson
===========
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ooks.com" target="_blank">www.buildersbooks.com
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jan_de_jong(at)casema.nl
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| Posted: Thu Nov 28, 2013 6:04 am Post subject: sight gauge alternative |
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This is what I saved a few years ago as a message to self.
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jan_de_jong(at)casema.nl
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| Posted: Thu Nov 28, 2013 6:37 am Post subject: sight gauge alternative |
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Curious about Peter's density difference of mogas and avgas I found:
From
http://www.engineeringtoolbox.com/api-gravity-d_1212.html
I get: s.g. = 141.5 / (API + 131.5)
From
http://armyquartermaster.tpub.com/qm5203/qm52030011.htm
I get:
avgas API 60 - 76, s.g.: 0.682 - 0.739
mogas API 54 - 63, s.g.: 0.728 - 0.763
maximum + / - differences: + 11.8 %, -1.5 %
on average mogas is about 5 % heavier but there is overlap
Ranges may be tighter in current practice, would require more study.
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asarangan(at)gmail.com
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| Posted: Thu Nov 28, 2013 9:26 am Post subject: sight gauge alternative |
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Peter
By proper differential pressure I assume you meant on one side there
will be the fluid pressure, and on the other side there will be tank
air pressure. I gathered from Paul's email that he did exactly this by
running the tank vent line to the sensor, but still sees a lag during
climbs and descents. This is most likely due to the large tank volume
and the small diameter of the vent tube. So it would matter exactly
where the vent line is teed off to go to the sensor. Closer to the
tank is better. In any case, this delay is likely to be
inconsequential because most of the spam cans I fly are only required
to have a reliable level indicator when the tank is really empty.
On Thu, Nov 28, 2013 at 8:38 AM, Peter Zutrauen <peterz(at)zutrasoft.com> wrote:
| Quote: | I would suggest updating the cct/system to work on proper differential
pressures - then venting isn't an issue. Ideally it would also incorporate a
g-sensor such that a prolonged turn doesn't affect the fuel level reading
(assuming there is some shorter duration filtering to deal with turbulence),
and a switch to select avgas/mogas densities. I was planning on implementing
such a system when the time came. I was also planning on a vertical aluminum
tube gauge on the outside of the tank containing a magnetic float which
triggered external level switches lighting up a simple led gauge - as a
backup and in lieu of the sight-gauge.
Cheers,
Pete
A239
On Thu, Nov 28, 2013 at 8:11 AM, Rowland Carson <rowlandcarson(at)gmail.com>
wrote:
>
>
> <rowlandcarson(at)gmail.com>
>
> On 28 Nov 2013, at 12:40, GRAHAM SINGLETON wrote:
>
> > isn't my vent system effectively the same as the factory setup? There
> > will still be a +ve pressure on the tank.
>
> Graham - thanks for pointing that out. Until now, I hadn't noticed the
> forward-pointing section at the end of the ultimate vent in your diagram as
> posted here yesterday. I had assumed the vent would finish with a section
> pointing vertically down (somewhere in the flap root area?) so as to
> generate neither positive nor negative pressure, but probably cut off at an
> angle to prevent whistles.
>
> in friendship
>
> Rowland
>
> | Rowland Carson ... that's Rowland with a 'w' ...
> | <rowlandcarson(at)gmail.com> http://www.rowlandcarson.org.uk
> | Skype, Twitter: rowland_carson Facebook: Rowland Carson
> | pictures: http://picasaweb.google.com/rowlandcarson
>
> ===========
> ="_blank">www.aeroelectric.com
> ooks.com" target="_blank">www.buildersbooks.com
> et="_blank">www.homebuilthelp.com
> et="_blank">www.mypilotstore.com
> "_blank">www.mrrace.com
> ="_blank">http://www.matronics.com/contribution
> le, List Admin.
> ===========
> target="_blank">http://www.matronics.com/Navigator?Europa-List
> ===========
> http://forums.matronics.com
> ===========
>
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jan_de_jong(at)casema.nl
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| Posted: Thu Nov 28, 2013 10:57 am Post subject: sight gauge alternative |
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I don't know whether it was mentioned but the aircraft attitude will
always have an influence on the fuel level reading.
The less one succeeds in mounting the sensor right below the center of
the tank the larger the influence.
One could measure pitch and do calibrations at several values and
interpolate.
I think that goes too far.
I don't believe the shape and size of the vent has any influence - the
air in the vent line(s) hardly moves.
Regards,
Jan de Jong
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grahamsingleton(at)btinte
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| Posted: Thu Nov 28, 2013 11:26 am Post subject: sight gauge alternative |
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I don't believe the shape and size of the vent has any influence - the air in the vent line(s) hardly moves.
Regards,
Jan de Jong
But it does have a pressure. That's what we are measuring
Graham
From: Jan de Jong <jan_de_jong(at)casema.nl>
To: europa-list(at)matronics.com
Sent: Thursday, 28 November 2013, 18:57
Subject: Re: sight gauge alternative
--> Europa-List message posted by: Jan de Jong <jan_de_jong(at)casema.nl (jan_de_jong(at)casema.nl)>
I don't know whether it was mentioned but the aircraft attitude will always have an influence on the fuel level reading.
The less one succeeds in mounting the sensor right below the center of the tank the larger the influence.
One could measure pitch and do calibrations at several values and interpolate.
I think that goes too far.
I don't believe the shape and size of the vent has any influence - the air in the vent line(s) hardly moves.
-= (And Get Some AWESOME FREE Gifts!)http://www.matronics.com/contrsp; -Matt Dralle, List Admin.
[quote][b]
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jan_de_jong(at)casema.nl
Guest
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| Posted: Thu Nov 28, 2013 12:21 pm Post subject: sight gauge alternative |
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What you hope to measure is the difference in hydrostatic pressure caused by the "column" of fluid in the tank and the same "column" of air outside the tank.
Almost any connection from sensor to the top of the tank with not-moving air in it will do, just like with pitot, static and stall warner lines. Non-moving means no friction pressure drop.
Jan
On 11/28/2013 8:25 PM, GRAHAM SINGLETON wrote:
[quote]
I don't believe the shape and size of the vent has any influence - the air in the vent line(s) hardly moves.
Regards,
Jan de Jong
But it does have a pressure. That's what we are measuring
Graham
From: Jan de Jong <jan_de_jong(at)casema.nl> (jan_de_jong(at)casema.nl)
To: europa-list(at)matronics.com (europa-list(at)matronics.com)
Sent: Thursday, 28 November 2013, 18:57
Subject: Re: sight gauge alternative
--> Europa-List message posted by: Jan de Jong <jan_de_jong(at)casema.nl (jan_de_jong(at)casema.nl)>
I don't know whether it was mentioned but the aircraft attitude will always have an influence on the fuel level reading.
The less one succeeds in mounting the sensor right below the center of the tank the larger the influence.
One could measure pitch and do calibrations at several values and interpolate.
I think that goes too far.
I don't believe the shape and size of the vent has any influence - the air in the vent line(s) hardly moves.
-= (And Get Some AWESOME FREE Gifts!)http://www.matronics.com/contrsp; -Matt Dralle, List Admin.
> http://forums.matronics==================
[b]
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jan_de_jong(at)casema.nl
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| Posted: Thu Nov 28, 2013 1:46 pm Post subject: sight gauge alternative |
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Hi Graham,
I should have added: overpressure at the top of the tank will be applied
equally to both "columns" and have no influence on the measured difference.
(I am assuming that the overpressure does not measurably change the
density of the air "column").
Jan
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grahamsingleton(at)btinte
Guest
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| Posted: Thu Nov 28, 2013 10:42 pm Post subject: sight gauge alternative |
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You're right Jan, I didnm't think it through
Graham
From: Jan de Jong <jan_de_jong(at)casema.nl>
To: europa-list(at)matronics.com
Sent: Thursday, 28 November 2013, 20:39
Subject: Re: sight gauge alternative
--> Europa-List message posted by: Jan de Jong <jan_de_jong(at)casema.nl (jan_de_jong(at)casema.nl)>
Hi Graham,
I should have added: overpressure at the top of the tank will be applied equally to both "columns" and have no influence on the measured difference.
(I am assuming that the overpressure does not measurably chttp://nbsp; -Matt href="http://www.matronics.com/Navigator?Europa-List" target="_blank">============
[quote][b]
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grahamsingleton(at)btinte
Guest
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| Posted: Fri Nov 29, 2013 1:53 am Post subject: sight gauge alternative |
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Wonder what the difference between cabin pressure and fuel vent pressure is?
Graham
From: Jan de Jong <jan_de_jong(at)casema.nl>
To: europa-list(at)matronics.com
Sent: Thursday, 28 November 2013, 20:20
Subject: Re: sight gauge alternative
What you hope to measure is the difference in hydrostatic pressure caused by the "column" of fluid in the tank and the same "column" of air outside the tank.
Almost any connection from sensor to the top of the tank with not-moving air in it will do, just like with pitot, static and stall warner lines. Non-moving means no friction pressure drop.
Jan
On 11/28/2013 8:25 PM, GRAHAM SINGLETON wrote:
| Quote: |
I don't believe the shape and size of the vent has any influence - the air in the vent line(s) hardly moves.
Regards,
Jan de Jong
But it does have a pressure. That's what we are measuring
Graham
From: Jan de Jong <jan_de_jong(at)casema.nl> (jan_de_jong(at)casema.nl)
To: europa-list(at)matronics.com (europa-list(at)matronics.com)
Sent: Thursday, 28 November 2013, 18:57
Subject: Re: Europa-List: sight gauge alternative
--> Europa-List message posted by: Jan de Jong <jan_de_jong(at)casema.nl (jan_de_jong(at)casema.nl)>
I don't know whether it was mentioned but the aircraft attitude will always have an influence on the fuel level reading.
The less one succeeds in mounting the sensor right below the center of the tank the larger the influence.
One could measure pitch and do calibrations at several values and interpolate.
I think that goes too far.
I don't believe the shape and size of the vent has any influence - the air in the vent line(s) hardly moves.
-= (And Get Some AWESOME FREE Gifts!) http://www.matronics.com/contrsp; -Matt Dralle, List Admin.
> http://forums.matronics==================
|
[quote][b][b]follow" target="_blank" href="http://www.buildersbooks.com/">www.buildeblank" href="http://www.homebuilthelp.com/">www.homebuilthelp.com
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jan_de_jong(at)casema.nl
Guest
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| Posted: Fri Nov 29, 2013 2:28 am Post subject: sight gauge alternative |
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The maximum would be around 0.5 psi: the (pitot - static) differential pressure at 150 kts or so.
About as large as the hydrostatic pressure difference caused by a full tank.
So venting the pressure port for the "air column" to the cabin is a bad idea; it has to go to the top of the tank with no leaks or movement of air.
On 11/29/2013 10:52 AM, GRAHAM SINGLETON wrote:
[quote] Wonder what the difference between cabin pressure and fuel vent pressure is?
Graham
From: Jan de Jong <jan_de_jong(at)casema.nl> (jan_de_jong(at)casema.nl)
To: europa-list(at)matronics.com (europa-list(at)matronics.com)
Sent: Thursday, 28 November 2013, 20:20
Subject: Re: sight gauge alternative
What you hope to measure is the difference in hydrostatic pressure caused by the "column" of fluid in the tank and the same "column" of air outside the tank.
Almost any connection from sensor to the top of the tank with not-moving air in it will do, just like with pitot, static and stall warner lines. Non-moving means no friction pressure drop.
Jan
On 11/28/2013 8:25 PM, GRAHAM SINGLETON wrote:
| Quote: |
I don't believe the shape and size of the vent has any influence - the air in the vent line(s) hardly moves.
Regards,
Jan de Jong
But it does have a pressure. That's what we are measuring
Graham
From: Jan de Jong <jan_de_jong(at)casema.nl> (jan_de_jong(at)casema.nl)
To: europa-list(at)matronics.com (europa-list(at)matronics.com)
Sent: Thursday, 28 November 2013, 18:57
Subject: Re: sight gauge alternative
--> Europa-List message posted by: Jan de Jong <jan_de_jong(at)casema.nl (jan_de_jong(at)casema.nl)>
I don't know whether it was mentioned but the aircraft attitude will always have an influence on the fuel level reading.
The less one succeeds in mounting the sensor right below the center of the tank the larger the influence.
One could measure pitch and do calibrations at several values and interpolate.
I think that goes too far.
I don't believe the shape and size of the vent has any influence - the air in the vent line(s) hardly moves.
-= (And Get Some AWESOME FREE Gifts!) http://www.matronics.com/contrsp; -Matt Dralle, List Admin.
> http://forums.matronics==================
|
[/b][b]
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ptag.dev(at)tiscali.co.uk
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| Posted: Fri Nov 29, 2013 2:54 am Post subject: sight gauge alternative |
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Hi! Guys,
I’ve been sort of watching your deliberations and have a small contribution which may not be relevant but sufficiently important for me to speak up.
When you calibrate the fuel levels into any pressure sensing of the depth of fuel being measured remember to “allow for” the fact that when the aircraft is brim full the column of fuel above the tank top in the filler pipe appears to nearly double the depth of fuel being measured.
I used to have one of Tony K’s systems and so had great difficulty with fixing the “Full” reading to actually represent the tank top volume which greatly reduced the accuracy of the full range of readings. This is in no way intended a criticism of his transducer system, but more an illustration of my computer illiteracy !
For interest G-PTAG has no external tank vents but they actually pass into a collection bottle in the cabin top( with a drain back to tank pipe) and continue inside over the roof and down to exit near the port side flap hinge bracket. I have never had any issues with venting or loss of fuel on refuelling in any weather conditions or temperatures for my main Europa Tank or my long range aluminium tank.
Regards
Bob Harrison G-PTAG Rotax 914.
From: owner-europa-list-server(at)matronics.com [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of GRAHAM SINGLETON
Sent: 29 November 2013 09:53
To: europa-list(at)matronics.com
Subject: Re: sight gauge alternative
Wonder what the difference between cabin pressure and fuel vent pressure is?
Graham
From: Jan de Jong <jan_de_jong(at)casema.nl (jan_de_jong(at)casema.nl)>
To: europa-list(at)matronics.com (europa-list(at)matronics.com)
Sent: Thursday, 28 November 2013, 20:20
Subject: Re: sight gauge alternative
What you hope to measure is the difference in hydrostatic pressure caused by the "column" of fluid in the tank and the same "column" of air outside the tank.
Almost any connection from sensor to the top of the tank with not-moving air in it will do, just like with pitot, static and stall warner lines. Non-moving means no friction pressure drop.
Jan
On 11/28/2013 8:25 PM, GRAHAM SINGLETON wrote:
| Quote: |
I don't believe the shape and size of the vent has any influence - the air in the vent line(s) hardly moves.
Regards,
Jan de Jong
But it does have a pressure. That's what we are measuring
Graham
From: Jan de Jong <jan_de_jong(at)casema.nl> (jan_de_jong(at)casema.nl)
To: europa-list(at)matronics.com (europa-list(at)matronics.com)
Sent: Thursday, 28 November 2013, 18:57
Subject: Re: sight gauge alternative
--> Europa-List message posted by: Jan de Jong <jan_de_jong(at)casema.nl (jan_de_jong(at)casema.nl)>
I don't know whether it was mentioned but the aircraft attitude will always have an influence on the fuel level reading.
The less one succeeds in mounting the sensor right below the center of the tank the larger the influence.
One could measure pitch and do calibrations at several values and interpolate.
I think that goes too far.
I don't believe the shape and size of the vent has any influence - the air in the vent line(s) hardly moves.
-= (And Get Some AWESOME FREE Gifts!) http://www.matronics.com/contrsp; -Matt Dralle, List Admin.
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h&jeuropa
Joined: 07 Nov 2006
Posts: 645
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| Posted: Fri Nov 29, 2013 2:27 pm Post subject: Re: sight gauge alternative |
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We originally copied some of Tony K's idea using the pressure transducer and op amp he designed to get a 0-5 volt signal for our GRT EIS. It worked OK for several years but there was always a problem of RF from the com transmitter causing interference when transmitting.
We have now switched to Freescale (Motorola) integrated sensors, MPXV4006DP which provide a 0-5 volt output for 0 - .87 psi. They are a differential sensor so the liquid side is connected to the water drain pipe from the tank bottom and the other side is connected to the tank vent. They only require a 5 volt supply that we take directly from our EIS. We calculated that a full fuel tank will have a head of pressure equal to about .4 psi. So we programmed the EIS so that 0 - .4 psi gives an output of 0 - 100.
We have two of these sensors, one on the port (main) and one on the stbd (reserve). In our GRT Sport EFIS we made the fuel calibration scales so that each side goes from 0 - 3 gal and when there is 6 gallons in the tank so fuel is over the saddle, then both read the same. The calibrations are in level flight attitude.
We have a sight gauge behind the seat back that is calibrated in the taildown attitude (we have a mono). We use that to confirm at the end of the flight that fuel used determined by the fuel totalizer in the EIS/EFIS is correct. We also use the sight gauge to determine how much fuel to add.
We calibrated the sensors in level flight attitude so we have a in flight check that the fuel totalizer and actual fuel used is correct. The other purpose of these sensors is to give more confidence of how much fuel is aboard when the tank is getting empty.
We've had no problems with using sensors with flouorosilicone seals and autofuel (very seldom do we use 100LL). For our sight gauge we use Tygon SE200 which has a flouoropolymer tube inside conventional clear tygon tubing. This tubing does not discolor or degrade when exposed to gasoline. Use with single barbed fittings.
Jim & Heather
N241BW XS, Mono, 914 500 hours
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jan_de_jong(at)casema.nl
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| Posted: Fri Nov 29, 2013 3:05 pm Post subject: sight gauge alternative |
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Thank you. This seems to be the sensible solution. Temperature
compensation, gasoline compatible and inexpensive too. Without g-force
compensation but that is probably not so useful anyway. I am glad to
understand that the long lines between panel and sensor do not pick up
noticeable noise.
What kind of averaging time did you set the EIS input to?
Jan
On 11/29/2013 11:27 PM, h&jeuropa wrote:
| Quote: | We have now switched to Freescale (Motorola) integrated sensors, MPXV4006DP which provide a 0-5 volt output for 0 - .87 psi. They are a differential sensor so the liquid side is connected to the water drain pipe from the tank bottom and the other side is connected to the tank vent. They only require a 5 volt supply that we take directly from our EIS. We calculated that a full fuel tank will have a head of pressure equal to about .4 psi. So we programmed the EIS so that 0 - .4 psi gives an output of 0 - 100.
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Remi Guerner
Joined: 14 Dec 2010
Posts: 284
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| Posted: Sat Nov 30, 2013 4:44 am Post subject: Re: sight gauge alternative |
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Hi all,
I am following this post - and previous discussions on fuel flow sensors and fuel computers- with amusement as it seems to me that all this high tech stuff needs a lot of attention and may be less reliable than the old fashioned equipment they want to replace. It is true that float type fuel gauges in the typical wing fuel tank are not accurate nor reliable. This is mainly due to the flat shape of the tank were a small height error makes a big volume error. I remember when flying Cessnas the gauges were only rough indicators that there were some fuel on board, and were useless in flight as they were looking like windshield wipers at the lightest turbulence. The Europa fuel tank geometry, being all in height, makes it a lot easier to accurately gauge the fuel quantity. My aircraft was originally fitted with an Avelec capacitive gauge with a digital indicator. It was giving a false sense of a great accuracy due to the digital display, but the indication was varying with the type of fuel used. After about 200 hours it started to give random indications and finally failed completely. I decided to replace it with an old fashioned resistive, float type with an analog indicator. This Jaeger unit is used on Robin DR400 type certificated aircraft. I had to weld an extension to the oscillating arm to take into account the unusual height of the tank. The fuel quantity accuracy and repeatability are very good. They are not visibly affected by the attitude of the aircraft and when refueling I can predict the quantity to be added to top the tank by a few liters. Additionally there is a low fuel switch integrated into the probe system which illuminates a warning light when the fuel remaining is 1.5 liters. Then I know I had better to switch to the reserve side. My back up is my watch: flight time and a conservative calculation using the maximum cruise fuel flow. This system has been working fine for me for 10 years and 800 hours..... without any fancy electronic chip, computers etc...
Remi Guerner
F-PGKL
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jan_de_jong(at)casema.nl
Guest
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| Posted: Sat Nov 30, 2013 6:09 am Post subject: sight gauge alternative |
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Hi Remi,
The unspoken issue that fuels the discussion is the desire to avoid
cutting a hole in the tank. Ofcourse, Bob Harrison thinks a large hole
is of the essence to allow yearly cleaning..
Jan de Jong
On 11/30/2013 1:44 PM, Remi Guerner wrote:
| Quote: |
Hi all,
I am following this post - and previous discussions on fuel flow sensors and fuel computers- with amusement as it seems to me that all this high tech stuff needs a lot of attention and may be less reliable than the old fashioned equipment they want to replace. It is true that float type fuel gauges in the typical wing fuel tank are not accurate nor reliable. This is mainly due to the flat shape of the tank were a small height error makes a big volume error. I remember when flying Cessnas the gauges were only rough indicators that there were some fuel on board, and were useless in flight as they were looking like windshield wipers at the lightest turbulence. The Europa fuel tank geometry, being all in height, makes it a lot easier to accurately gauge the fuel quantity. My aircraft was originally fitted with an Avelec capacitive gauge with a digital indicator. It was giving a false sense of a great accuracy due to the digital display, but the indication was varying with the !
type of fuel used. After about 200 hours it started to give random indications and finally failed completely. I decided to replace it with an old fashioned resistive, float type with an analog indicator. This Jaeger unit is used on Robin DR400 type certificated aircraft. I had to weld an extension to the oscillating arm to take into account the unusual height of the tank. The fuel quantity accuracy and repeatability are very good. They are not visibly affected by the attitude of the aircraft and when refueling I can predict the quantity to be added to top the tank by a few liters. Additionally there is a low fuel switch integrated into the probe system which illuminates a warning light when the fuel remaining is 1.5 liters. Then I know I had better to switch to the reserve side. My back up is my watch: flight time and a conservative calculation using the maximum cruise fuel flow. This system has been working fine for me for 10 years and 800 hours..... without any fancy elec!
tronic chip, computers etc...
Remi Guerner
F-PGKL
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ptag.dev(at)tiscali.co.uk
Guest
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| Posted: Sat Nov 30, 2013 10:29 am Post subject: sight gauge alternative |
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Hi!Guys
Slight correction to that statement:-the large hole was for mounting the
fuel level probe but it was made sufficiently large to enable a mop out
annually because that is the only way you can know what is in there and
with the ethanol issue now a fact you can check out the water implication
for stress free flight!
Regards
Bob Harrison G=PTAG
--
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