I'm currently in Kenya, i've been here for about 7 months now as some of you may or may not know the Great rift valley runs through Kenya so it has areas that are quite high. Where I live it's ~2,000m (6,800ft) as a result of this altitude and coupled with the heat flight times are severely reduced and stability of flight is also an issue.

Does anyone have any thoughts to combat this? I have been told that the British army here use longer propellers on their (full size) helicopters and try to reduce the relative weight of the aircraft as much as possible. With that in mind I have attempted to use Phantom 2 9334 props rather than the stock 8" props without much success mainly I think to  my misunderstanding of what to set the gains at.

I have been told that you are supposed to lower the gains for larger props, but also increase gains at higher altitudes. Because of this in the following two tests I didn't change the gains at all... thinking perhaps mistakenly that it would balance out.

My first test involved 9334 carbon  fibre props. It actually seemed to result in greater stability overall. However, upon descending the Phantom appeared to fall into its own wash and practically fell out of the sky.

End result - http://instagram.com/p/u5ZwftQ2XM/

If it hadn’t clipped a tree I am sure I could have regained control, no such luck sadly.

I’ve since read that a lot of people have trouble with cf props due to their inflexibility and falling into ones own wash is quite a common problem. I should state that even with the stock 8” props at this altitude if you descend too fast you lose control pretty quickly in comparison to sea level where you can fly like a maniac and still maintain control.

As a result the next day (after literally breaking two of my toes recovering the phantom from a tree and the gimbal/gopro from a gutter) I ran a test with a set of Phantom 2 Vision 9334 props, these are plastic and have a great amount of flexibility which I have been told greatly improve their efficiency, for this test I selected a site a little farther from my house incase the mabati (corrugated iron) roof had had an effect on flight given it probably radiates a great amount of heat (you see pelicans riding the thermals above the house a lot).

These props turned out to be massively more powerful than the CF variant, maybe that has something to do with the way they can flex I’m not an expert. Regardless, from the recovered footage you can see that the Phantom was vibrating like crazy from the use of these props so much so that moments before take off the battery door popped open (which nobody noticed at the time) - after take off it was impossible to maintain control and the phantom simply continued to ascend or change course without concern for what the transmitted was instructing it to do.

Video of brief flight & fall - http://instagram.com/p/u8J0IYQ2VA/

Luckily the Phantom was caught by a nearby tree and didn’t disappear off into the stratosphere however it did fall for about 30’ without power and obliterate most of the propellers.

I would be inclined to think that these props would actually be the solution for greater flight time at this altitude due to how much lift they were producing, however ensuring that the Phantom remained in control and didn’t vibrate so much is an obvious problem. Given it refused to descend I assume the gains need increasing significantly so that it can correct itself inflight, or is this a misinterpretation on my part?

After both these crashes I took the Phantom to pieces to ‘resettle’ the   insides, give it a bit of love and it has had little ill effects from either crash which is great.. However, i’d like to avoid further crashing

If anyone has had any experience in this area it would be great to hear their input.

Gain settings for plastic 9334s or other ideas for increased flight time at altitude would be great.

Also, the cheaper hobbyking batteries here don’t seem to survive the heat perhaps, i’m not sure. But since being here i’ve gone through a number that have swelled beyond safe limits, or have had cells die. The only ones that seem unaffected are the stock phantom batteries.

Lake Naivasha and my house - https://www.dropbox.com/s/zoj4iy2hg3...00.09.png?dl=0
https://www.dropbox.com/s/0flqc6hoxc...06.09.png?dl=0
Kericho tea plantations - https://www.dropbox.com/s/uizvxedsw8...mg017.jpg
Lake Baringo - https://www.dropbox.com/s/o3b516r6cc...mg019.jpg
Mugie Dam - https://www.dropbox.com/s/n84bksjvy0...mg014.jpg

Non-aerial photos - http://instagram.com/err_ok

Also good information in this post from a user from Colorado living at 5000 ft!