Request for ideas for fuel management in quadplane

ArduPlane VTOL Plane
1

Hi there!

I am Ivan from team Yonah. Our team’s end goal is to build an autonomous system (currently a quadplane) that we can use to help rural healthcare providers with transportation of cargo (up to 4kg) in support of their operations.

I am currently working on a fuel monitoring system for our quadplane, and would like to reach out to the community for help on some of the questions I have with regards to fuel management.

Here are some technical specifications of our quadplane & fuel monitoring system:

  • 30 kg MTOW
  • 100 km/h cruise speed
  • 4L fuel capacity
  • Using a variable resistor basedfloat sensor for fuel monitoring

Here are some of the queries I have:

1) How do you estimate fuel burn rate?

I understand that fuel burn rate should be quantified as flight duration (hours/ minutes) per unit of fuel and that it varies with local conditions e.g. temperature, altitude.

What are some of the ways through which you can derive a reliable estimate of fuel burn rate? Some of the ways I have identified are: conducting a short test flight; performing static ground tests; monitoring fuel consumption in-flight; --> eventually producing a fuel burn rate chart

2) How do you decide when to return to base?

Currently we are still conducting test flights via flying in circuits. Hence, it would be good to know the fuel level at which we should return to base.

I’m thinking this would be in the form of a guideline that goes: “return to base when fuel reaches ‘x’ %”

This would require calculations for how far the farthest point of the circuit is (in terms of time and distance) from base, and taking into account of a “personal minimum fuel percentage” that we should never go below.

Do you have experience on this and what recommendations would you make?

3) How do you reduce the noise in fuel level data?

Engine vibrations and aircraft banking have been observed to introduce noise into the fuel level data sent by the float based sensor (in the form of varying voltages) that we have currently deployed.

Do you have any recommendations for noise filters? Do you write these filters on your own?

4) Are there measures taken to safeguard against fuel gauge failure?

For example: always fill to full before flight; never exceed ‘x’ flight time?

Do you have recommendations as to what measures to take?

Thank you for taking the time to read my post! Any assistance is appreciated :slight_smile:

2

First off, I don’t have personal experience with this but this is how I would proceed if I had to do it.
Secondly, always stick with the principle: fuel on board = time in the air.

Depending on the engine and R/C control system, you could probably use the FrSky Gas Suite to measure actual fuel usage. Again, always remember FOB=TIA. From my perspective, I would lean more on time rather than distance.

When you do your own flight testing and fuel burn calibrations, always take note of temperature, due point, pressure, winds aloft (at least from weather forecast for that day), and MSL altitude of takeoff point. This way, you can establish a baseline that you could add or deduct a certain percentage against your estimated fuel consumption.

Well calibrated fuel level indicators are only accurate they’re level and unaccelerated condition, i.e. on the ground. Even with internal baffles, they only serve as visual cues. They tend to be inaccurate, especially at mid level.

Always jot down engine start or takeoff time and keep track of your time in the air.

Good luck.

3

Thank you @rollys for your suggestions!

Agree that “time in air” should be the quantity that should be used for decision making and hence should be investigated.

The FrSky Gas Suite is a product that we can definitely look into when we require more visibility on engine performance.

And noted that we should take note of temperature and other environmental conditions that may affect fuel consumption when generating baselines for fuel prediction

4

This guy has built a 2 tank system that has potential to do what you want. It’s also a cool video.