Fuel Flow error

[malko05]

Hello,

I operate VL3 with skyview 1000. After 250 hours my fuel flow is wrong. It indicates 20 liters per hour instead of 17 liters per hour, which is the real consumption.
I never change the K factor witch is still 68000.
I checked all the fuel circuit, all is ok.

I don’t understand what’s happen, can you help me ?
Many thanks
François Gahide

 

[skysailor]

You need to adjust the K factor. It is derived with simple mathmatics. In your case, try changing the 68000 value to 57800.

17     (57800)
__ =   _____

20      68000

 

[malko05]

I understand that I could change the K factor. However I do not understand why, with no changes to my installation there is a variation of almost 20%!
Have you ever had a similar case?

 

[skysailor]

The K factor is an estimate of the number of pulses the sensor will produce for a given volume of fuel. Every sensor is actually different. Some brands test each sensor and label each with the tested value. This adds cost to the sensor. The Red Cube uses a standard value for all sensors produced which is why there is no calibration value on the sensor. The only mention of K factor from them is on the instructions.

You should start with the value they give you so that your fuel flow indications and computer can function. You are expected to calibrate the unit using known flow values either by pumping measured volumes into calibrated containers or simply refueling to the exact level after flights and measuring actual fuel replacement required. Use either of these methods to determine the actual K factor of your sensor and change the value in the EFIS accordingly. You should only have to set it this one time. From that point your fuel readings will be extremely accurate. This procedure must be repeated only if you replace the fuel flow sensor. If, for some reason you had to replace the EFIS screen but nothing else, putting the value you had determined in the new screen would allow the very accurate fuel measurement you had before the screen failed. The K factor will not change over time for a fuel flow sensor. Only if you replace the fuel flow sensor will you have to recalibrate and determine a new K factor.

The reason you need to change the K factor is that you have never calibrated the fuel flow sensor. Calibrate it this initial time and you will not have to do so again. Do not forget to back up your settings for the Dynon when you are done. It will save a lot of work and time if you ever need to replace a screen. The instructions to backup your system to the thumb drive are in the manual.