|
-
POSTING RULES

-
Donate yearly (please).
-
Advertise in here!
-
Today's Posts
|
Insert Pics
|

06-08-2018, 07:42 AM
|
 |
|
|
Join Date: Feb 2010
Location: Gardnerville Nv.
Posts: 2,828
|
|
Quote:
Originally Posted by Flying Canuck
Well that wasn't a very productive night. I checked resistance between my firewall and the sender plate and got tiny numbers, so I can't see this being a ground issue. I pushed through the calibration for both tanks. The right tank stayed at the peak level until my 45L pour (out of 67L) when it jumped a lot. It stayed at the second level right through to full. The left tank never budged from 2.67V.
The one thing I managed to get was a calibrated dip stick, so at least I can tell how much fuel I have on the ground. I think my next step will have to be emptying the tanks and seeing if I can tell if the floats are free to move either with my inspection camera or by poking some hinge pin or something up through the drain. That's probably going to have to wait until after I do my first engine start on Saturday.
|
When you say tinny numbers can you verify you are getting < than .2 OHMs between your battery negative and the float mounting plate, and make sure the meter is not reading thousands, there should be the OHM symbol and not a (K) or an (M). 
__________________
7A Slider, EFII Angle 360, CS, SJ.
|

06-08-2018, 07:57 AM
|
 |
|
|
Join Date: Oct 2009
Location: Victoria, BC, Canada
Posts: 3,932
|
|
On my -6, when I bought it my float senders would only read from about 2/3 of the tank down to empty. It came with two automotive-style needle gauges and when I replaced them with a single MGL fuel gauge found it a little disconcerting that the level stayed at 72L per side for more than an hour's flying before jumping to somewhere just under 50L.
The Red Cube I installed along with the MGL gauge, however, has been bang on. Never more than 1L off when I re-fill.
I had to remove the senders and re-seal the covers due to leaky cork gaskets, when I put them back in I find that the readings are more capricious than they were... I wonder if the grounding resistance has changed enough that i'll need to re-calibrate. Still, the totalizer via the red cube remains spot on.
If I have to remove the covers again, i'll remove the senders permanently, and mount Red Cubes in each wing root. That would be more accurate than the floats, and would read accurately from full to empty.
__________________
Rob Prior
1996 RV-6 "Tweety" C-FRBP (formerly N196RV)
|

06-08-2018, 08:31 AM
|
 |
|
|
Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,147
|
|
Quote:
Originally Posted by Flying Canuck
Well that wasn't a very productive night. I checked resistance between my firewall and the sender plate and got tiny numbers, so I can't see this being a ground issue. I pushed through the calibration for both tanks. The right tank stayed at the peak level until my 45L pour (out of 67L) when it jumped a lot. It stayed at the second level right through to full. The left tank never budged from 2.67V.
The one thing I managed to get was a calibrated dip stick, so at least I can tell how much fuel I have on the ground. I think my next step will have to be emptying the tanks and seeing if I can tell if the floats are free to move either with my inspection camera or by poking some hinge pin or something up through the drain. That's probably going to have to wait until after I do my first engine start on Saturday.
|
This sounds very much like a stuck float, or with some resistance to movement, possibly due to debris from building becoming lodged in the rheostat arm. You might try putting about 4 gallons of fuel in the tank and rocking the wing back and forth to slosh it at the wing root, to force the float up and down quickly a few times and see if that frees it up. Other than that, you'll probably end up pulling the end plates open to get at the sender.
__________________
Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid 
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
|

06-08-2018, 08:49 AM
|
 |
|
|
Join Date: Apr 2012
Location: Collierville, TN (KFYE)
Posts: 1,433
|
|
Quote:
Originally Posted by Snowflake
On my -6, when I bought it my float senders would only read from about 2/3 of the tank down to empty. It came with two automotive-style needle gauges and when I replaced them with a single MGL fuel gauge found it a little disconcerting that the level stayed at 72L per side for more than an hour's flying before jumping to somewhere just under 50L.
The Red Cube I installed along with the MGL gauge, however, has been bang on. Never more than 1L off when I re-fill.i
I had to remove the senders and re-seal the covers due to leaky cork gaskets, when I put them back in I find that the readings are more capricious than they were... I wonder if the grounding resistance has changed enough that i'll need to re-calibrate. Still, the totalizer via the red cube remains spot on.
If I have to remove the covers again, i'll remove the senders permanently, and mount Red Cubes in each wing root. That would be more accurate than the floats, and would read accurately from full to empty.
|
My red cube is mounted just below my fuel distribution manifold so it sees exactly what goes into the engine. Almost every fill up, I compare what was pumped to what is predicted by the fuel flow and since I?ve calibrated everything carefully, the result is within 3/10 gal consistently. I do look at my fuel level displays but only as a secondary source of info.
__________________
RV-8 #81077 Super Slow Build
Dynon Skyview HDX, Titan IOX-370, Dual P-Mags, AFP FM200A FI, Whirlwind 200RV CS Prop
First Flight 11/20/2016
www.marksrv8.com
|

06-08-2018, 08:57 AM
|
 |
|
|
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,597
|
|
Quote:
Originally Posted by Snowflake
SNIP
If I have to remove the covers again, i'll remove the senders permanently, and mount Red Cubes in each wing root. That would be more accurate than the floats, and would read accurately from full to empty.
|
Good plan assuming you don?t have something like a tank sump valve leaking or when the line guy (if you don?t fuel the tanks yourself) shorts you.
The float senders are dirt simple and reliable.
Carl
|

06-08-2018, 09:43 AM
|
|
|
|
Join Date: Jan 2015
Location: Red Deer, Alberta, Canada
Posts: 387
|
|
Quote:
Originally Posted by bret
When you say tinny numbers can you verify you are getting < than .2 OHMs between your battery negative and the float mounting plate, and make sure the meter is not reading thousands, there should be the OHM symbol and not a (K) or an (M). 
|
If I recall correctly, I was seeing something close to .2 ohms - I was definitely on the ohms setting. The left tank might not have been that good, my multimeter was acting up and I was getting some fluctuations.
__________________
Claude Pitre
RV-9A #91081, C-GCPT
Dynon SkyView HDX, IO-320 and WW 200RV C/S. Flying as of August 6, 2018
Interactive map of all of my flights here
|

06-08-2018, 12:54 PM
|
 |
|
|
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
|
|
Quote:
Originally Posted by Snowflake
On my -6, when I bought it my float senders would only read from about 2/3 of the tank down to empty.
|
Pretty standard for all the RV's that have wing tanks. Because the senders are located in the most inboard bay of the tank, and with the dihedral angle there is fuel in the outboard portion of the tank that is higher than the highest point of the float, it will always require some fuel to be burned off before the float starts to lower.
Never been an issue because it is at the bottom of the gauge range that accuracy is important.
A poor ground connection of the sender flange to airframe ground is a very common cause of a fuel gauge not working properly (either during initial calibration of after some time in service). It is easy to check with an ohm meter (no point in adding ground wires, etc., without even checking to see if it is the problem).
A common cause of calibration error is not accounting for friction in the sender. This varies from one sender to the next when they are new so it sometimes doesn't cause a problem, but often times it does.
Think about the fact that in flight an airplane has vibration induced into it by the engine/prop (regardless of how smooth your engine runs). This vibration helps overcome any friction in the float senders. This vibration isn't present while doing a fuel gauge calibration. (Side note - When the military first started flying jet aircraft they discovered that many of the analog instruments were no longer accurate because the airplane was free of vibration. The had to artificially vibrate the panels)
When we do fuel calibrations in our shop, we do the fuel add, and then tap on the fuel tank skin with an open hand until the voltage wont change anymore. Add more fuel, and repeat. The value will often change quit a bit from what it is if you just pour in the fuel.
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.
Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
|

06-08-2018, 01:01 PM
|
 |
|
|
Join Date: Oct 2007
Location: In New Braunfels, ist das Leben schön!
Posts: 871
|
|
Quote:
Originally Posted by larrynew
I had one tank's float stick when I first tried the Skyview calibration pours. I ended up giving the round plate a few raps with a rubber hammer and it unstuck and has read accurately for 600+ hours. Guess it hadn't moved for a year or two while building and just needed a little coaxing.
|
What he said  . I try to check the easy, fast and cheap things first.
__________________
Larry New
RV-7A - Built, flying 900+ hrs
RV-10 - Built, flying 2.9 hrs
??? - RV-12, Subsonex
48 States in 7 Days!
VAF Paid - Annual Autodraft
|

06-08-2018, 04:10 PM
|
 |
|
|
Join Date: Jan 2010
Location: Southern Michigan
Posts: 1,966
|
|
I tested both my new senders with an ohm meter before I installed them in my modified ER quick build tanks. One was not at all happy and I was getting a small range of float arm swing with no reading at all. Close examination of the resistor part I found a stripe of some kind of black substance/coating on the part of winding where there was no electrical contact unless I pressed on the contact spring arm. I was able to clean it off with some acetone and and a Q-Tip and it tested fine after that. I have no idea what it was though and they were factory new.
__________________
David C.
Howell, MI
RV-10: #41686 Under Construction
RV-9A: #90949 Under Construction
RV-10: #40637 Completed/Sold 2016
Cozy MKIV:#656 Completed/Sold 2007
"Donor Exempt" but donated through Dec. 2020
|

06-08-2018, 05:15 PM
|
|
|
|
Join Date: Jan 2015
Location: Red Deer, Alberta, Canada
Posts: 387
|
|
Decided to play hooky from work this afternoon and go and try some of your suggestions. Glad I did because I arrived to find a very large blue ring on the floor and an overwhelming familiar smell. Probably should have tightened my fuel lines at the bottom of the valve better. I lost about 10L of AVGAS.
Anyways, armed with a new battery for my multimeter I checked and found the resistance between the sender plate and the firewall to be right around 0.2 ohms. I powered up my display to look at the calibration routine and then decided to check voltage on my senders, between the plate and the post. I found that matched what Skyview was seeing exactly. My conclusion from that is that adding a ground won't change anything. On a whim I removed some fuel from the right wing and checked the voltage again and it moved. I repeated the action and got the same reaction. Looks like the right side is fine. I completed the calibration on the right tank, it worked quite well. As expected, the readings topped out around 57L. I tried the left wing again and got zero movement through about 30L (right wing moved quite a bit in that range). I tried the tapping and rocking tricks to no avail. Either this sender is bad or it is jammed. I think my only recourse now is pulling it out, I'll try that in the morning.
Thanks for all of the great discussion and suggestions, it's certainly helped.
__________________
Claude Pitre
RV-9A #91081, C-GCPT
Dynon SkyView HDX, IO-320 and WW 200RV C/S. Flying as of August 6, 2018
Interactive map of all of my flights here
|
| Thread Tools |
Search this Thread |
|
|
|
| Display Modes |
Linear Mode
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
All times are GMT -6. The time now is 08:26 AM.
|