Topic: After-Crash - what I wish I had known (also tips for stable flying)
Just a couple of tips for Drone noobs I learned the hard way.
[edit nov 19, 2011] - wanted to put this high on the post. Terrific site with way more good information about Drones than this little post. Go there read it. Read it again. Good info, well laid out. http://www.dronescapes.com/
Got my repaired AR Drone back the other day (great job with the repair, Parrot, thanks). I did what I think everyone does when they first open the box. I watched a couple of the videos and started flying immediately. Since I was an experienced RC airplane pilot, I thought I wouldn't need to get up to speed on the AR Drone. I was wrong.
First briefly, my crash was caused by sheer stupidity. It was cold outside (battery drains faster) and the Drone was about 60 feet in the air when the low-battery warning came on. I didn't land immediately and it did the emergency cutout. Dropped like a rock to the pavement. THe landing gear cracked at the center intersection, but I didn't notice. Tried to fly it later inside and it was erratic as hell, crashed it hard against a wall and that damaged the mobo. After that i just sent it in.
Ok, had it back for a week, flown every day and done what I should have done in the beginning, I've carefully "studied" how this thing works. Here are 3 quick tips for those who don't want to read the following long post:
1. FLAT TRIM. Always. Before EVERY flight. And in the your first day or so reduce your tilt angle to 5deg. You'll thank me.
2. Unplug Reset. Unplug Reset. Unplug Reset. Do it all the time, especially after a crash. I'm not talking about the reset button on the bottom. For some reason I've found that doesn't do enough to clear the memory. I unplug reset after every 3 flights, because I found that the more you take it off without resetting the more erratic it flies on each consecutive flight.
3. Indoors and outdoors, but especially indoors, make sure there is a big high-contrast pattern underneath the Drone before you take off. Carpet is NOT a high-contrast pattern. The Drone uses motion tracking with its underside camera to stabilize its X-Z position in space. It uses the on-board altimeter to stabilize its Y position, but that underside camera is too low-rez to track the pattern of a carpet. That's why you see people taking off from the box. They didn't make that "H" landing pad on the box to be cool, they made it, because it's the perfect pattern for the underside camera to see. This is very important to keep the Drone from drifting around the room over a carpet. In lieu of the box, take black tape and put a crosshair or just black strips here and there. It's that important.
Ok, now I'll go into a little more detail about flying the drone. You can't compare this to an RC Helicopter, it's not. It's a flying computer. It has Artificial Intelligence, it senses its environment and reacts to that environment. It's also incredibly well constructed. I don't think you can damage it at all in an empty carpeted room with 8ft ceilings no matter what happens. That fact alone makes it worth the nearly $300. There must have been a LOT of R&D crashes to get something light enough yet tough enough to handle a lot of crashes without any damage. The blades are really tough and flexible as is the landing gear. They don't shatter like normal RC planes or helicopters.
Please make your first flights indoors in a room that you've cleared out as much of the furniture as you can. Don't go outdoors for the first flights. Use default settings and then reduce the tilt (not the iPhone tilt, but the Drone tilt) to 5deg for indoors. I have no idea why the default for indoors is not the minimum 5deg.
On your first takeoffs just take it off, let it stabilize and land it. Letting it stabililize after takeoff is VERY IMPORTANT. Don't start flying it immediately. The manual says 10 sec. I say about 5 or 6, but the A.I. needs to evaluate the environment and get ready for your input. Get a feel for how that process goes. It's ever-so-slightly different on each takeoff so it's important that you get comfortable with pushing that takeoff and landing button and seeing what happens. Next do only elevation changes with the right control button. Take it up, take it down. Take it up, push land. Then take it up to the ceiling. Wait, look what happens when it gets near ceilings. Bang, it kind of goes out of control and hits the ceiling. Not sure why that happens, but it does. So you've learned an important lesson. DON'T FLY CLOSE TO A CEILING, it's not stable near ceilings.
Also, the videos show the Drones flying down hallways. I tried flying it down a narrow hallway and it started bouncing off the walls. Personally I think the same programming that makes it freak out at ceilings makes it freak out in narrow hallways. It likes open space. But I'm happy for someone to correct me on this point. Maybe I'm doing something wrong.
When you first go outside keep the indoor hull on for the first several flights. The perfect flying environment for outside flight is a wide flat field, no wind, with tall grass for cushion. The Drone is always "pinging" the ground with high frequency sonar to determine its height. So if you're flying over stairs or a section of split-level ground the Drone will follow the contour of the stairs/ground. For instance if you fly it over an 8ft retaining wall the Drone will plunge 8ft but not crash into the ground below. Try it, it's actually cool after you get your heart beating again.
The Default settings work well outside as long as you uncheck "Altitude Limited" and check "Outdoor Flight". If you're an experienced RC pilot you know that wind is your obsession. I flew RC ultralights and I couldn't fly over 4knots of wind. The AR Drone does not sense wind, but it does sense drift of the aircraft by the underside camera looking at patterns below it. So if the wind is pushing it sideways it says, hmmm, the user is not making me go sideways, why am I going sideways must be the wind, I'll tilt myself in the opposite direction until I stop drifting. That is freaking amazing! Watching it compensate for wind is worth the $300 in my book.
Ok, one of your first temptations outside is to turn the Drone around so that the camera is photographing you, the pilot, get some cool video of yourself. That's fine to do, but if you haven't flown RC planes before you have to get your mind around the fact that the controls are suddenly BACKWARDS, because it's facing you. Try to resist that temptation at first, because your corrections, especially as you get nervous are all going to make the Drone move opposite of what you want, and it ends up snowballing into a bad crashy. Hence why you don't take off the indoor hull for a while even outdoors.
I recommend always flying with the drone pointing in the direction of your body and just use the iPhone to move it back and forth left and right. If you turn the Drone, move your body behind it so the controls remain natural.
Get used to pressing the "Land" button to get the Drone down, even if your landing site is not perfect. Once you press that button you lose control of the Drone, but the A.I. on board is actually better than you are at making a safe landing.
When you get really good (and it takes a long time) you can fly it like an airplane by coordinating the yaw and the bank so that it's always looking forward and performing graceful turns like a plane. You rarely see that in videos, because it takes that much skill.
I use "FlightRecord" to get video from the Drone. I also use a 3Gs. On a 3Gs the video rate is probably 10fps, and when you're recording video the CPU overhead is pretty high, so the Drone is sluggish and control latency is high. I switched to my wife's 4g iPhone and video recording was like 18fps. Bottom line is, the faster the iPhone/iPad, the better the video. But I can't find any difference with the FreeFlight application between phones. Same response times.
Finally, NEVER CHARGE THE BATTS RIGHT AFTER FLYING. They may only feel warm, but lil-poly batts like to be as cold as possible before charging. Wait 15 minutes at least, they cool down pretty fast.
These tips are not intended to cover all aspects of flying, but just to keep you from crashing your new flying computer.
My last thoughts are this: It's BRILLIANT that Parrot made the iPhone software open-source. AR Pursuit is the first of cool software, and there's going to be a lot more. As phones get faster the apps are going to get cooler. But now I'm going to have to fly it with an iPad. Sigh.
One last thing. There's a great RC Groups forum for people who want to mod their Drone and get some incredibly detailed info on it.
Enjoy your flying, it's a very cool little gadget.