After numerous bench tests, re calibrations, and more bench tests I was finally brave enough to take my 3DR quad out for it's first flight -albeit tethered. I did some initial outdoor ground testing in which I brought the throttle up to the point of takeoff but noticed that the quad was showing a tendency of tilting forward and right so I killed the throttle, ran this test several times, and decided I didn't want to attempt the takeoff having no clue what might happen. So...
I threw together a quick test rig on nearby deserted swingset to evaluate what the quad would do when in the air. The video clip below shows the outcome... Without any stick input the quad wants to fly forward and to the right. I was able to counter it with stick movement and fly the quad around the rig without too much trouble but if I stopped countering the roll/pitch it would try and wander (this is evident in the video when you see it start to move sharply to one side).
I've ruled out motor rotation, wiring, and prop direction via another round of tests to verify everything's good. That leaves me suspect of:
I also found the following in a FAQ post:
"My copter yaws right or left 15° when I take off: Your Motors are not straight or your ESCs are not calibrated. Twist the motors until they are straight. Run the ESC calibration routine."
I've calibrated the ESC's many times over the learning process how often should I need to re calibrate them? As for motors not being straight... I've checked that they're secured properly to the frame, not sure what could be off.
I'll be continuing to test but thought I'd post my experience, my swingset test rig, and humbly ask for any pointers on what to look at.
My suspicions were correct. I proceeded to make sure all curves and mixes were set properly on my TX. Then Ran the er9x stick calibration on the TX.(main screen, hold down to get to radio setup, calibrate) Then I connected up mission planner and ran the TX calibration there. Just did a quick lift-off test in the living room and the quad made a very calm almost straight up 4in lift before I put her down. Much better than previous tests.
Andy, I know how scary all this is. I too struggled with my first flight. That's been about four months ago and I've been happy with flights since.
Be careful with your tether because it can "fight" your quad's stabilization. Think of it like a spinning bike wheel and precession forces. You want to keep it slack so you can really see what's going on. Make sense?
Here's how I've been 'getting a feel' for the quad before going airborne.
Before I explain that, I used to have problems lifting off from the ground (grass). First off, the landing gear (since abandoned) will catch and cause the quad to flip. And the propwash affects attitude near the ground. Not good. It seems that a quick, decisive liftoff is best for me. I prefer flying over grass since it's a whole lot softer if you "land hard."
Now I hold the quad by the top of the stack (I know, this is NOT SAFE) at waist height with my right hand and advance the throttle with my left hand until the quad begins to feel weightless. I can then hold it with only the lightest grip. If there are any weird tendencies, I easily notice. If all is OK, I just nudge it away and take over on the Tx while it 'floats away.' Works like a charm. Obviously, you need to lift your hand up and away from the props. Comprend?
Wear heavy leather glove like welder's gloves if you want to be safe. Just shake the glove off after you launch.
Now, my 3DR quad, 880kv, 12x3.8, is loaded with camera and weighs in at about 4 lbs., 2200g. I still do this hand launch. Maybe it comes from my many years of launching RC planes by hand like a javelin.
Part of the problem that I had in learning to fly my 3DR hex was in trying to lift off too slowly. Scared to break my $600 investment. Similar to Phil's method (which is more problematic in a hex than a quad), I do a preflight of the controls (just like in my Cessna) but since I can't see the ailerons, elevator and rudder, I hold he copter on the grass, bring the motors up, then feel which way the copter wants to move as I move the sticks. If I am OK with this, I throttle down, back up a few feet, and bring the throttle up. Not so gently that the VSI barely moves, but one-quarter to one-half throttle to get off the ground quickly. You'll learn how your throttle responds, but when you are about ten feet up, bring the throttle down until the copter is in a hover.
BTW - you will crash.
Buy another set of props, maybe a spare motor, and a replacement arm. But, have fun.... Don't get frustrated and threaten to sell the copter and give up. (Been there, done that). One day it will "click" and you will begin to have more confidence in your ability to fly.
Thanks guys! Finally had a chance to try out the re-calibrated quad outside and it flew really well.
I have a pretty aggressive throttle curve setup so it was quite easy to keep 15ft. off the ground and get a feel for moving her around in the air. The 3 months of SIM playing while my 3DR kit got delivered must be paying off.
Good to hear. You were smart to SIM. It will be interesting to hear about your progress.
None the less, like Steve suggests, order those spare parts 'cause there will be some 'hard landings.' Watch out for low batteries. Balance charge often. Do you have a battery alarm? Good luck!
The battery alarm is pretty much the only critical piece I don't have.
I got a big lost in the whole frsky + telemetry + er9x hacks vs. the APM voltage monitoring features... I was going to buy the frsky module: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=...
but it's been out of stock for a while. I guess the other option is to use the Attopilot
Do you have a recommendation? (other than to install it asap...)
With 15 or more flights in with my home-brew 3DR frame and 3DR electronics, I have found that for beginner type exercises - hovering, slow yaw, left/right roll flight, front/back pitch flight, etc, that the 9 minutes or so of concentration attunes your hearing to the reduction of rpm from the motors as the battery decays to non-function.
When the battery is near depletion, the quad simply starts a slow decay in altitude. Increases in throttle are somewhat ignored and you know then to control the descent.
If you have a timer on your TX, figure out how to set it in 'up count' mode and once off the ground trigger it. After depletion, note the time. Do this a few times to get a trend and then set the TX timer to count down preset to that time, or the next minute increment lower.
In short, I wouldn't worry about a battery monitor until you are ready to fly far enough away to not hear the motor rpms AND you need the extra juice to get back to a safe landing. You will have enough experience to gain before doing that. FPV? The systems usually have a battery monitor status in the data stream/display. FPV is definitely not a beginner topic.
I didn't add my AttoPilot until flight 10 or 12 and that was only to collect data in an effort to learn what I needed for more flight time. Having built mine 'heavy' for training purposes I knew weight is the first thing to fix.
She doesn't complain about my flying, I don't complain about her weight!
Congrats on a hovering flight!
In short, I wouldn't worry about a battery monitor until you are ready to fly far enough away to not hear the motor rpms AND you need the extra juice to get back to a safe landing.
Anything you can do would be good and of course as soon as you can. I use a Spektrum DX7s with the telemetry module to monitor voltage. But there's no way to set an alarm with it. You have to watch the display and that's really not the best way. I have my eyes on my copter and can't watch the display all the time. So I do set a countdown timer on Tx to alert me when I reach a safe time to start to land. Be sure to balance charge. A cell out of balance can cause a rapid drop in pack voltage. Not good!
I have a cheap battery alarm that connects to the balance connector. Get one with two horns that reviewers have called LOUD. Here's an example: HK Battery Alarm I can't seem to get to the US Warehouse today. Maybe storm has it knocked out.
On a related note, I've damaged props, motors, arms doing simple things. If you snag a leg in the grass the copter can flip and break a prop or knock a motor loose, bend the housing. I sometimes fly in my backyard with evil tree branches looming nearby. Copters and tree branches don't get along. Ouch!
[This post was started before seeing Starwalt's above. +Doug]
Phil, Thanks for the battery alarm link, that's a perfect "tide-me-over" until I upgrade my 9x to it's glorious FrSky telemetry display capabilities -at least I'll have some warning. I've yet to let her fly more than 20 feet away from me but I'm feeling my first adventure outside Stabilize Mode today... Perhaps a little loitering...
Hey as I'm having a very similar problem what exactly did you do to fix this issue?
For me, while the quad was tethered I was able to use the TX stick to neutralize the lean so I figured radio calibration was the simplest explanation and it was. Configure the sticks on your TX... then open mission planner and do the radio config there. That corrected the issue for me.