Hi Mostafa,
It is me that ought apologise for spelling your user ID wrong in the first place.
However, your explanation is fine, I understand... thin air = thin ice!!!
as in not enough resistance to keep the fan spinning!
I believe high inertia is a good thing as it means it is easier to keep the blades RPM up.
On a mid sized model the rpm is about 1600, with the plan for this model, I reckon between 800 to 1000, probably made from carbon fibre and composite, which usually "windmill" quite well. That said, ceiling is not going to be more than 300 feet I guess..... DA more likely to be a temperature effect, but slight if at all at such altitudes. You need to see the damn thing and even at 1/4 scale, it gets quite small, very quickly! Mind, there are now on board GPS technologies that can bring it back to the start point, as these tend to work with the gyro stabilisation systems, potentially a welcome feature!
Thanks again, enjoy the lie down and just know you are enriching some one elses life!
Cheers,
Gaz