# Hight altitude (between 2000m and 4000m ??? Thrust, lift force, witch motor, battery and propeller ???

I all, Arducoter thrust and lift force problems at hight altitude ???

My question is: My 3DR have to flight between MSL 2000M and 4000M for scientific missions (bio-diversity monitoring in Alp contest). I make the first test yesterday, and my 850kv + 10/4,5 prop and 3S 2600mAp 30-45c, where not enough to lift my drone at ALT MSL 1900m (at the end i brake some blades and ouch... ;-( . So i'm trying to find a solution like 4S and 12/4,5 or 11/4,7. I studying with "drive calculator" but no one as putting into the program the dates for it. On other hand i did not find precise datas about 880Kv and 12/4,5 and 11/4,7 propellers too proceed with calculations.

May somebody help me ? BRGDS Olivier.

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### Replies to This Discussion

I can't really help you much but I'm slightly interested in what you're trying to do...

So it couldn't even get off the ground...or you reached a certain altitude and it refused to go any higher?

I'm pretty sure if you go to 4S and the 880kvh motors it will be have so much power you won't have any issues at all.  Probably just the 4S batteries alone will make your problems disappear.  If that fails, try 5S!

I randy. Thanks for answering me.

It couldn't get off the ground and i destroyed 2 propellers ;.-(

It was also very unstable ... much more then at 200M MSL Alt ... I think this is normal without lift forces. The stabilizing system will not understanding what to do without thrust in poor air density !

Question:

Do you know somebody into our community with knowledge in "DriveCalculator" software ?? Seem very interesting to calculating the thrust lift autonomy batteries altitude temperature etc... But nobody put datas for our motors and prop's...

It would be fine if someone of "store.diydrone" put the data of 10/4,5 10/4,7 12/4,5 11/4,7 850kv and 880kv into http://www.drivecalc.de/ data base website. Do you have the direct contact of them?

BRGDS Olivier.

Olivier,

I'm very surprised you couldn't get off the ground..but i guess the air is a lot thinner.  You've tried flying it at a lower altitude and all is fine?  very interesting!

You know there's some data for the motors at the bottom of the purchase page in store.diydrones.com.

I do know those guys..they're just so busy..I'm not sure if they'll take on the suggestion when they have sooo many other things to do.  Maybe Jani would from the jDrones store..he's very into the motors..he spent a lot of time testing them.  I believe Jani's motors and the 3dr ones are very similar.

To be honest, I would have thought that the lift from the 3dr 850s and all other 850s would be pretty similar..but then..what do i know?!  I've never really looked into it.

Randy,

At 200m in Torino it was working quiet good but in mountain have a lot of difficulties to adjust the pitch. If i understand how it's working it's working in negative ... that mean less thrust when it try to adjust it stability!

At 2000m the atmospheric pressure is about 850hPa instead of 1013hPa at mean sea level. Air density at sea level is in ISA (International Standard Atmosphere) 1,225kg/m^3. That mean that at 2000m about 1,028kg/m^3 and a  factor is 0,83 for the thrust ... Then the problem is the reaction of the motors regarding to the air resistance/drag and propeller etc ...

I think that's a good idea to ask to Jani Jdrone.

Do you have his direct contact ? Any way i will contact him thought his web site.

Brgds Olivier.

This is a pretty interesting situation! I wonder if an adjustment to Stabilize_P would help in the stabilization in lower air densities?

I agree with Randy though, a 4s should do the trick.

Maybe you can add Jani as a friend and PM him on this site

Actually, Rate_P would probably make more sense in this situation

You're probably right that Rate_P also needs to be higher in lower air densities..that would make sense right? need to increase the engine speed more to get an equivalent amount of thrust.

Thanks guys, i will interesting myself to those Rate_P and/or Stabilize_P

Is there any topics/explanations about those way to configure them ?

BRGDS, Olivier.

There's a few wiki pages here.  I suspect they're not completely up-to-date but I think it's a start.

Basic principle is increase P until it wobbles, then back off 20%.

Just to be clear, adjusting these rates alone likely won't fix the problem if you don't have enough power to get off the ground (i.e. throttle is at full but you're still just sitting on the ground).  If you're getting off the ground but then flipping or wobbling, etc, then PIDs could fix the issue.

Good luck.

It will be done.

I order new 10/45 and 12/45. Today i will buy 4S's

I will make those experiences: at 2000m

1) 12/45 + 850Kv + 3S

1.1) 12/45 + 850Kv + 4S

2) 10/45 + 850Kv + 4S

3) if positive take off >>> working on "P"

3.1) if negative take off > ordering 880Kv + 10/47 11/47 props and make same experiences.

First i have to wait for the replacement destroyed props ;-(

I will be back to you after those experiences...

Olivier

Have your tried using a bigger prop like 14"?

Anyway, this calc might help:

http://www.ecalc.ch/xcoptercalc_e.htm

Hi Johnny, thanks for the link i will examinate this and then i'm back to you !

BRGDS Olivier.

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