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.
Google Earth file-2013-05-01%2009-46-24.tlog.kml
T-Log- 2013-05-01%2009-46-24.tlog
Comments
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.
@R.D.- Yes APM 2.5 with Power module. I'm powering plane with 2- 3300mah 4S batteries with a caslte creations 5 amp BEC on the output side for servo power.
@Gerard- Thanks for the bungee link, I'll look into it.
I built a bungee launcher and found that the best launcher is the one that is relatively simple, but does not topple over or otherwise fall apart when launching. PVC tubing is good material. A very good link is here:
http://www.rcgroups.com/forums/showthread.php?t=1459906
Things to look out for:
Your friend was really lucky on this prop strike. That could very easily have ended in a serious injury.
I missed the cutting out issue and yes, it could be contributing to a problem like that.
Just to clear, are you flying APM 2.5 with a 3DR power module?
Analyzing tlogs is much easier after Randy's tutorial video in the middle of THIS page.
-=Doug
@Dwgsparky- Thanks for the recommendations. I did level using the MP after boot up. We had saw horses and set the plane on them to level. The video overlay of the MP is not exact on timing so it may seem a little off. Yes, no more hand launching these big birds. I'll probably build a catapault. Love the one in the video, do you have link for purchase or more info?
Hi Adam
Congrats on the maiden flight, looks good.
One item I noticed is your APM needs to be re-leveled. If you watch the times you are flying straight and level and tehn observe the HUD the X8 is at about 8'positive . set the X8 up on a table and set it at that same angle then manually re-level the plane in the config page, Also check that the switch form manual to an auto mode transfewrs the trim adjustments . My X5 had the same issues, now fixed.
Regarding the prop strike.... there are several instances of propstrikes causing a lot of skin, muscle and nerve damage (some permanant ) from flying wings like the X5, X8 and many other types. If you must hand launch use a good glove for protection, I remove the top of the thumb for the Tx stick OR use a bungee OR a catapult like this one which will launch an X8 in total safety. https://www.youtube.com/watch?v=Eobl_iSa_cs ( Previous link was incorrect, Edited my Mod )It will soon be available for purchase.
Happy flying
Doug,
Where can I view the screen shot your posting above? You think this is why the motor was cutting out sparatically and not a radio or failsafe issue?
A little more graphing of the same tlog file...
...looks like the battery voltage started bad before the Vcc value. Vcc is checked inside the Arduino. We discussed this over in the AC thread HERE.
In the case of the AC code, a minor bug was keeping the Vcc recording from working. Yours is working.
-=Doug
Whoa... take a look at your Vcc as graphed below.
Is the posted tlog of the second flight or the first flight? (seems too short for the first flight).
The X axis is time in milliseconds (I think). The launch, besides the prop strike, may have been doomed because the Vcc was unstable at the 1000 mark.
-=Doug
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