I finally got around to the X-8 maiden flight. Nice day, gentle breeze, batteries charged and ready to go. Things went as well as they could for a first flight. The plan was to take off in manual, trim things out, then try stabilize and maybe even RTL. Unfortunately when I switched to Stabilize the plane leveled then seemed unresponsive to my control inputs. I quickly switched back to Manual before it flew into the ground and continued to fly. I also had a few radio glitches for some reason which caused the APM to Failsafe to "Circle" mode. Is that normal? I should probably change that to RTL.
Here comes the bad news. My "helper" was to film the ground to air footage for this video. After the 6-7 minute 1st flight, I landed and he hit "Record", the whole flight the camera was on pause. WHAT! @*%$! Now my dilemma, the wind is picking up but I want some nice footage from the ground. It's getting too windy to hand hold both the radio and X-8 with one hand each so how about this, I'll have my helper hand launch the plane while I man the radio? After some brief instructions and a wind check, it was time for flight #2. As you will see from the beginning of the video, things did not go as planned. When he went to toss the plane he left his hand up and in the way and it was struck by the prop causing it to nose over into an uncontrollable dive.
So far the only damage I can find is both plywood wing flanges where the little screw goes through broke and I got a pitot tube full of mud. I didn't like the wing attachment set-up anyway so now I have a reason to fix them. By the way, he's alright and he only suffered a couple small scratches on his fingers. Very lucky!
Moral of the story is, don't be rushed to make a flight if ANY of the conditions aren't right, always make sure the cameras are rolling and don't put un-trained personnel on the end of expensive equipment.
Hope you enjoy and if anyone has any comments on the Stabilize non-control issue please let me know.
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T-Log- 2013-05-01%2009-46-24.tlog
Comments
@Adam
No changes were made to the setting other than checking the RTL altiude which was set at 0 feet! now set to 100'
That was a surprise, It came at me like an arrow as I was standing at the home position. . now it behaves OK. this is a X5 not an X8 so you may neeed some pid adjustments. ? I dont know.
@Dwgsparky- I'll give that a try. Did you have to change any of the max-min PID settings for auto modes like someone mentioned earlier?
I had the same issue with my X5, the solution is to fly staright and level at about cruise speed and note the angle that the HUD is showing. this is the +ve angle the wing needs to fly. Then set up the wing on a table and use blocks or books to set the plane to the same angle you saw in the HUD then perform a manual level . next flight the HUD will show roll and pitch at zero as the plane is flying correctly.
@Lloyd- Good tip on the leveling, I'll give that a try. I figured the Circle mode thing out when I watched the mission planner video back. My radio was going into Failsafe in a certian part of the field. I've also re-routed the way the antenna was layed out inside the plane better.
Also the latest version switches to circle for a short while as part of RTL I think.
That may explain the seemingly random elevon deflections as well as the attitude problem.
On my X8 initially stabilize would lose altitude very quickly and even loiter would too.
I had to level the plane in a fairly pronounced nose up attitude to overcome these problems.
I think what looks like level to the X8 on the ground is really quite a nose down attitude in flight.
I went through the radio calibration again yesterday after repositioning some equipment inside the plane. One thing I noticed is that on the ground, after initial power up with a good 3D GPS signal, the servos twitch all over when I switch into RTL mode. I even walked out always away from "Home" and tried it again to see if it would move the correct direction and take me home but nothing. Just random aileron deflections. Manual mode seems to work correct as does Stabilize although I probably need to adjust my max pitch and roll angles like U4eak stated above. In the video I try Stabilize 2 times and while it seems to level the plane, the plane just starts a slow desent into the ground causing me to swich back to Manual mode ASAP.
Any ideas on the twitching servos?
@Alex- Yes, this is the one I like and want to build.
Hi Adam
I have tried both Bungees and Catapults, both work well but they also have their own individual down sides/ problems. At the end of the day its your personal choice.
Good points for bungee:-
Relativly simple, Lower cost, fits most planes
Bad points for Bungee:-
Can be dangerous ...if the anchor point comes out of the ground, Reseting the launch into the wind can be a problem, Possibility of destroying an aircraft if the trim is wrong (i.e.new plane) or the wind changes at launch. once you press the trigger you are committed and the bungee will pull the plane even if its on the ground and damaged,
You need to make a strong attachment point to the plane. ( how do you know its strong enough??)
Good points for Catapult, very consistent and repeatable launch profile, Easy to turn the catapult into the wind if the direction changes. Ususally no modifications to the plane. No dragging the plane across the ground if there is a problem at launch, The plane is fully supported by the cradle during the launch and then when the plane leaves the cradle it is a glider and in a good flying attitude if the engine fails and it will return to earth just as a regular landing. No cords to tangle in the prop, no drag chute needed.
Bad points for Catapult. Higher initial cost, Can be tricky to transport. More parts to maintain than just a bungee and a ramp......
I value my hands and have had minor propstrike injuries in the past and I dont hand launch anymore...... ever.... its just not worth the risk!. If cost is a big issue then use the cheaper bungee with the associated risks or use a Catapult if you want to protect your investment in the plane and achieve repeatable results. If you are looking at using your UAV at sites where there may not be the traditional flying sites then the catapult gives much more versatility for operation,i.e side of the road,Farm tracks, small field, lawn of the house.etc. For me this is the best method.
The Catapult you see in the video of the earlier post is the prototype and is set up for the X5 and simular planes upt to about 1.5-2kg it is used with the motor OFF This is because the X5 propeller overlaps the inboard end of the Elevons and so you cannot push against the control surfaces.The motor only starts after the plane is clear of the cradle.
If you want to launch a X8 at say 5Kg then the X8 motor can run DURING the catapult launch and assist the catapult bungees. A few simple calculations are all that is needed. The Ramp and Cradle will support a 7.5 Kg plane with no problem.
We are about to offer these for sale in a few weeks with shipping from Canada. (no tax for USA) The cradle can be configured for most planes. more details soon.
Hi Adam,
Glad the crash was non fatal, I have had the non responsive problem in stabilise mode, the plane certainly is stable, but whatever you do, it matches it and straight on you go. No solution was found for my 60" wing after months of research & posts. Now have a Ruby Autopilot, stabilise, loiter & auto land done in a day, sweet.
APM is going on a quad.
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