Hi,

I'm designing a mid to long-range (5-10km) UAV that needs to carry a payload with a mass <2.5 kg. It needs to stay up in the air for at least an hour. I know some of the components going into it, but I'm not sure about a lot of them. I also don't know what airfoil I should use. I understand aerodynamics, but I'm terrible with electronics. I need to figure out all the components before I can find a wing design. These are the problems problems that I have:

Airfoil:
- Requirements:
- Maneuvering speed at ~40 knots, Vne at ~60 knots.
- Predictable stall speed, preferably as low as possible.
- Low drag
- Not too thin

Electrical Components:
- Known:
- 3DR APM 2.6 Autopilot
- Ublox Neo 6m GPS / Magnetometer
- Hobbyking OrangeRx Open LRS 433 MHz 1W
- Airspeed Sensor
- Unknown:
- Battery? How much amperage + voltage would be good to power everything for 1+ hours?
- Motor? Climbing power isn't exactly an issue but I need to be able to fly in a headwind.
- BEC?
- ESC?

Oh, and I'm on a budget of $400 so don't go crazy :P

Thanks

If you know about aerodynamics, then you know that the airfoil requirements you're asking for can't be done. You'll have to make a choice between a wing that's forgiving and lands slowly versus efficient. Given the flight time you want, you'll probably have to go with a pretty hot airfoil and just deal with the negatives.

Which brings up piloting skills. The APM 2.6 is a very capable controller. I have one in my quad. But it can't do everything for you. You still have to be able to take off, fly, and land your vehicle with it. Yes, I'm aware that the APM has those features as autonomous functions. But they have to be programmed by someone who knows how the plane is supposed to fly. Also, sometimes they don't work. Sometimes the terrain isn't good enough for autonomous takeoffs and landings, and sometimes you'll lose your GPS lock and get a flyaway. A buddy of mine is really into drones now after a few years in RC, and he's watched pilots with $3000 drones take them home in trash bags because they thought they didn't need piloting skills to enjoy them. He's also watched a couple of guys not take their drones home at all because they had a flyaway and the owner wasn't even a good enough pilot to bring it back home and couldn't find the crash site. If you can't fly the plane without the autopilot, don't take off with it.

Power system choice will require calculations that go well beyond most hobby aeromodelers' knowledge. You'll have to calculate the total frontal area of the plane and its drag before picking a prop and choosing which motor Kv you need. Then you'll have to determine the amp draw you'll use and pick batteries from there. Of course, as you go with bigger batteries your drag will increase as weight increases. It gets complicated quickly. BTW, the kind of batteries you'd need to pull off a project like this will cost over $400 each by themselves, so you'll need to expand your budget considerably.

So having helped you as much as I can, I'm going to be a little bit critical of what you're doing now. First, if you don't have any design experience, you are biting off way more than you can chew. The high end commercial drones can accomplish the kind of flight times and speeds you are talking about, but none of the well established hobby grade autonomous planes can. An hour of flight time on an electric is a lot to ask. It would be a lot easier to do with gas power since the plane will lose weight as it goes. But even then you would be looking at a plane that's not pilot friendly at all. If you really want to learn how to design planes and work up to your goals, start with building one of the established designs and learn from it. You'll probably get 10 minute flight times out of it and will meet your budget. Second, you haven't said what this 2.5kg payload will be, but I assume some kind of camera equipment. Whatever it is, I hope you have enough sense to not do anything that could shed a bad light on the hobby. Drones have attracted a large number of morons to our hobby over the last few years who are inviting significant regulations for RC that have never existed before. Check the FAA regulations very thoroughly for RC and drone flight and also check your local laws. If you don't want to take that time or don't want to abide by those regulations to the letter, build a rover or boat to do autonomous operations with. Better yet, stick to video games for your entertainment. I don't say that to be mean to you, but rather to keep you from joining the ranks of those who make the news on a weekly basis.

I doubt anyone is going to come along that can top the most excellent answer that Jester just gave you. You might want to study this plane a little further. It flew across the Atlantic in 1998. I remember when it was written up in the model magazines. What a fantastic accomplishment. Here is a link to the model.

https://en.wikipedia.org/wiki/AAI_Corporation_Aerosonde

Their are lots of videos on youtube showing models flying over a mile high and through fog and cloud cover. There is no way a pilot or spotter can keep track of a model being flown like that. Its just plain irresponsible and dangerous. Not for the RC pilot but for any manned aircraft that may run into it.

There is already talk of bans on FPV equipment. I am not for banning anything but do think it should be regulated and the purchaser trained in responsible use. But if the FAA wants it banned you won't hear a peep out of me protesting the ban.

My buddy flies a homebuilt Falco all wood plane that cruises at between 180 and 200 knots. I can't imagine what it would be like to hit a model plane at that speed. Especially one like you are talking about that would surely weigh over 10+ pounds with a full payload. I am sure it would bring the plane down. And I believe its not a matter of if but when for this to happen. Let some people get killed and watch the rules and laws that are implemented.