8665087083?profile=RESIZE_710xI am looking for a collaboration with a drone company to do a high altitude flight experience. We are starting a small company called Loweheiser, we are developing EFIs for small engines for UAVs. Right now we are developing a throttle body for an RCGF 15RE, and I also want to design one for the 10cc of this same brand. The 10cc is probably the smallest electronic fuel injection engine that has ever been made, At the moment the smallest engines we have worked on are the Saito FG-21 and the FG14, the FG14 has a 7mm throttle body!

Many clients ask me how high the EFI works. I tell them that the EFI can operate at any altitude that a fixed-wing UAV can reach. The absolute pressure sensor of the ECU can measure from 15 to 115 kPa, 15kPa are 60000m so it seems not a problem. We have tested at 2000m because it is the maximum we can reach in a few hours of travel, but I would like to test it in flight with higher altitude.
In my initial calculations I see that a normal plane could reach 10,000m without problems. A plane of about 2m wingspan and about 3kg of weight consumes less than 100w to maintain a cruise.

The 15cc engine has about 1.54Kw. The motor loses power linearly with the loss of density of the atmosphere The density of the atmosphere at 25ºC 0m (sea level) is 1.12720 kg / m3, the density of the atmosphere at -20ºC and 10000m is 0.453337kg / m3, that's 40% of the power of the engine at sea level. it is 600w, even introducing losses of another 50% due to propeller performances and other ineficiencies ... there is still 300w which is more than enough to fly at 10000m

Where can be done this high altitude challenge?
I am looking for a collaboration with a drone company who has experience in flying in an airspace where this test can be done and who can take permission from the concerned authorities. 

Best regard, jlcortex

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  • hi Frederic
    Yes, it is true, a propeller that thrusts well at sea level possibly has zero thrust at 10,000m. Right now I have no idea how to do these calculations.

    In my opinion we have to found a balance, a large propeller with a lot of pitch but that can still climb slowly at sea level.

    with electric planes it seems not problem, but using electric is easier because the motor has a much wider rpm range.

    There are a company interested in the project. They have a very nice 2.4m flying wing. They build composite airplanes at their facilities.
  • The back of the envelop calculation gives indeed around 100w ( mechanical ) for a level flight at 10Km in a stable air. One of the challenge is to be able to have enough mechanical power left at that altitude, because you will need a propeller design that has also some kind of efficiency at sea level. You will most likely need a large pitch to fly at a reasonable speed ( ~30m/s ) into thin air which is not too good to take off and climb when you are around max L/D ratio so slow and into thick air. Of course you can always imagine using variable pitch propeller but for such small engine it is a challenge on its own. my 2cents
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