VM1000 fuel totalizer
Moderators: Rick, Lance Murray
- Rich
- 5 Diamonds Member
- Posts: 4604
- Joined: Mon Aug 30, 2010 12:40 pm
- First Name: Rich
- Aircraft Type: DA40
- Aircraft Registration: N40XE
- Airports: S39 Prineville OR
- Has thanked: 145 times
- Been thanked: 1185 times
Re: VM1000 fuel totalizer
The limit on the fuel gauge maximum is a consequence of the segmented tanks. The probe on each side can only read to the point where the inboard compartment is filled, at which point there is still room (for about ~3 gal.) in the outer compartment. There is a calibration process that needs to be performed on each side, and it's tedious. In addition I believe it's possible to subsequently remove/install the probes incorrectly such that the calibration is no longer accurate. In my case, the gauges are far more accurate in indicating how much fuel the tanks take to be filled than using the fuel computer REM number. I have a suspicion why, but need to gather more data, as my theory has a discrepancy I need to resolve.
I once ran a tank dry, Well, almost, as I chickened out after running it for about 10 minutes indicating 0 gallons on the gauge. Using the tank drain afterward I got about 1/2 gallon out of the tank.
I once ran a tank dry, Well, almost, as I chickened out after running it for about 10 minutes indicating 0 gallons on the gauge. Using the tank drain afterward I got about 1/2 gallon out of the tank.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
- Robodog
- 1 Diamond Member
- Posts: 7
- Joined: Mon Jul 15, 2019 12:56 pm
- First Name: Roger
- Aircraft Type: DA40
- Aircraft Registration: N263DS
- Airports: N51
- Colin
- 5 Diamonds Member
- Posts: 2006
- Joined: Sat Aug 21, 2010 8:37 pm
- First Name: Colin
- Aircraft Type: DA42
- Aircraft Registration: N972RD
- Airports: KFHR
- Has thanked: 319 times
- Been thanked: 527 times
Re: VM1000 fuel totalizer
There was a guy I used to follow who built an RB-6 and blogged about the process and his flights afterward. On a return from Mexico with his wife onboard he ran the left tank dry over Big Bear on their way home to Fullerton. His wife burst into tears when the engine stopped and he said it wasn't really possible to console her during the restart, descent and navigation of the complex Los Angeles airspace. But he said that they have a rule now that he'll only do that if he's alone in the plane.
Colin Summers, PP Multi-Engine IFR, ~3,000hrs
colin@mightycheese.com * send email rather than PM
http://www.flyingsummers.com
N972RD DA42 G1000 2.0 s/n 42.AC100 (sold!)
N971RD DA40 G1000 s/n 40.508 (traded)
colin@mightycheese.com * send email rather than PM
http://www.flyingsummers.com
N972RD DA42 G1000 2.0 s/n 42.AC100 (sold!)
N971RD DA40 G1000 s/n 40.508 (traded)
- Lance Murray
- 5 Diamonds Member
- Posts: 1163
- Joined: Tue Jul 06, 2010 11:25 pm
- First Name: Lance
- Aircraft Type: DA40
- Airports:
- Has thanked: 7 times
- Been thanked: 120 times
Re: VM1000 fuel totalizer
My VMS-1000 fuel gages are accurate within 1 gallons. My gages also only show 15 gallons max. That wasn't the case when I first got the airplane.
Steve wrote: ↑Tue Sep 24, 2019 3:05 pm Roger:
Your aircraft seems to be the rare exception with respect to VM1000 fuel gauge accuracy. After more than 16 years on the various Diamond Forums, almost everyone reports a high degree of accuracy and repeatability with the VM1000 capacitive gauges. They do have the weird characteristic of not reading the outboard tank quantity (in the 40 gallon DA40s), but you will get used to that. My aircraft reads a maximum of 15 gallons per side (which is the actual capacity of the inboard tank). In my case, the gauges have never been off as much as one gallon per side in almost 18 years of ownership. Typically, they are off less than 0.5 gallons per side. I never fully trust the gauges (thanks to my primary flight instructor in the Navy), and crosscheck visually when possible, calculate fuel burn using the fuel flow numbers and book burn values, and in general, probably fly around with more fuel than I really need.
It is possible that your probes need to be recalibrated...
Steve
- Rich
- 5 Diamonds Member
- Posts: 4604
- Joined: Mon Aug 30, 2010 12:40 pm
- First Name: Rich
- Aircraft Type: DA40
- Aircraft Registration: N40XE
- Airports: S39 Prineville OR
- Has thanked: 145 times
- Been thanked: 1185 times
Re: VM1000 fuel totalizer
Mine are like that, also. The left gauge tops out at 15 gallons, the right at 16. (Note that this is an almost 18-year old plane.) But once they start reading below these numbers, they're also accurate within the 1 gallon resolution. I could go through the calibration procedure again, but it's a really tedious process to correct a minor area of inaccuracy and is itself subject to error.Lance Murray wrote: ↑Fri Oct 18, 2019 5:34 am My VMS-1000 fuel gauges are accurate within 1 gallons. My gauges also only show 15 gallons max. That wasn't the case when I first got the airplane.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
- Rick
- 5 Diamonds Member
- Posts: 1575
- Joined: Tue Jul 06, 2010 10:09 pm
- First Name: Rick
- Aircraft Type: DA40
- Aircraft Registration: NONE
- Airports: KROA
- Has thanked: 107 times
- Been thanked: 297 times
Re: VM1000 fuel totalizer
I don't think you can "correct" this error via calibration. The failure to show the first 5 gallons on each side is due to the lack of fuel sensor in the outer tank. Remember, with the 40-gallon DA40's, each wing has a 15-gallon inboard tank (with a sensor) and a separate 5-gallon outboard tank (the one with the filler cap) with no sensor. So, there is no way to measure the first 5 gallons in that outer tank!Rich wrote: ↑Fri Oct 18, 2019 2:39 pmMine are like that, also. The left gauge tops out at 15 gallons, the right at 16. (Note that this is an almost 18-year old plane.) But once they start reading below these numbers, they're also accurate within the 1 gallon resolution. I could go through the calibration procedure again, but it's a really tedious process to correct a minor area of inaccuracy and is itself subject to error.Lance Murray wrote: ↑Fri Oct 18, 2019 5:34 amMy VMS-1000 fuel gauges are accurate within 1 gallons. My gauges also only show 15 gallons max. That wasn't the case when I first got the airplane.
Roanoke, VA (KROA)
- Rich
- 5 Diamonds Member
- Posts: 4604
- Joined: Mon Aug 30, 2010 12:40 pm
- First Name: Rich
- Aircraft Type: DA40
- Aircraft Registration: N40XE
- Airports: S39 Prineville OR
- Has thanked: 145 times
- Been thanked: 1185 times
Re: VM1000 fuel totalizer
When new, they topped at 17 gallons each. That's the documented behavior. There is fuel in the outer chambers before the inner chambers are completely full. And the chambers are not 15 and 5 gallons. From the AMM:Rick wrote: ↑Fri Oct 18, 2019 3:39 pmI don't think you can "correct" this error via calibration. The failure to show the first 5 gallons on each side is due to the lack of fuel sensor in the outer tank. Remember, with the 40-gallon DA40's, each wing has a 15-gallon inboard tank (with a sensor) and a separate 5-gallon outboard tank (the one with the filler cap) with no sensor. So, there is no way to measure the first 5 gallons in that outer tank!Rich wrote: ↑Fri Oct 18, 2019 2:39 pmMine are like that, also. The left gauge tops out at 15 gallons, the right at 16. (Note that this is an almost 18-year old plane.) But once they start reading below these numbers, they're also accurate within the 1 gallon resolution. I could go through the calibration procedure again, but it's a really tedious process to correct a minor area of inaccuracy and is itself subject to error.Lance Murray wrote: ↑Fri Oct 18, 2019 5:34 amMy VMS-1000 fuel gauges are accurate within 1 gallons. My gauges also only show 15 gallons max. That wasn't the case when I first got the airplane.
Each inboard chamber has a capacity of 52.6 liter (13.9 US gal) and each outboard chamber has
a capacity of 26.1 liter (6.9 US gal). The total fuel tank capacity of each wing is 78.7 liter
(20.8 US gal).
As a side note, I once drained one side as completely as I could and upon refilling, it took 20.9 gallons per the fuel delivery meter. The addition tenth is likely a consequence of the volume of the interconnecting hose.
Here is an exercise I did that approximates the volumes of different areas of the tanks, be it air or fuel. It's useful to illustrate the fueling of the outer chamber before the inner chamber is totally full.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
- Lance Murray
- 5 Diamonds Member
- Posts: 1163
- Joined: Tue Jul 06, 2010 11:25 pm
- First Name: Lance
- Aircraft Type: DA40
- Airports:
- Has thanked: 7 times
- Been thanked: 120 times
Re: VM1000 fuel totalizer
Can anyone explain why when the airplane was new it would show 17 gallons max indication but now it only shows 15 gallons max indication? Could this have had anything to do with the battery chip replacement?
Both numbers are still accurate after burning below that number. My current procedure is to burn a tank to 14 gallons, then switch tanks and burn that one down to 14 gallons. From that point I have an accurate 28 gallons on the gages.
Both numbers are still accurate after burning below that number. My current procedure is to burn a tank to 14 gallons, then switch tanks and burn that one down to 14 gallons. From that point I have an accurate 28 gallons on the gages.
- Thomas
- 4 Diamonds Member
- Posts: 229
- Joined: Tue Oct 19, 2010 6:20 pm
- First Name: Thomas
- Aircraft Type: DA40
- Aircraft Registration: D-ENMA 40.337
- Airports: LSZC BUOCHS SWITZERLAND
- Has thanked: 91 times
- Been thanked: 62 times
Re: VM1000 fuel totalizer
I do the same thing to have the correct indication with 28 gallons. I did replace the VM1000 Batt chip 3 yrs ago - but it had no effect. (2003 plane)
Thomas Bienz DA40-180 40.337 D-ENMA (sold 08/2022)
Home Airport LSZC Buochs Switzerland
Home Airport LSZC Buochs Switzerland
- Steve
- 5 Diamonds Member
- Posts: 1971
- Joined: Thu Aug 12, 2010 1:23 am
- First Name: Steve
- Aircraft Type: DA40
- Aircraft Registration: N432SC
- Airports: 1T7
- Has thanked: 85 times
- Been thanked: 503 times
Re: VM1000 fuel totalizer
No. The fuel indicator calibration data is stored in non-volatile memory in another IC. I have replaced the memory battery twice with no loss of calibration. The only "non-linear" behavior I've noted on my airplane is occasionally, after filling the tanks they read 14 gallons instead of the usual 15 on the ground. After a few minutes in the air, they will come up to 15 and stay there until I burn off just over 5 gallons a side.Lance Murray wrote: ↑Fri Oct 18, 2019 4:35 pm Can anyone explain why when the airplane was new it would show 17 gallons max indication but now it only shows 15 gallons max indication? Could this have had anything to do with the battery chip replacement?
I assumed that when I fill the tanks, some air bubbles may get trapped on the sensor, enough to slightly alter the capacitance of the probe. After flying a few minutes, the vibration of flight shakes them off the probe, and gives the accurate full reading.
Steve