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Permalink Reply by Richard on June 17, 2012 at 11:17am

Air Crash Investigations please!! 

Had my first explainable crash today with the Skywalker, using APM2, UK spec 3DR Radios. Range checks were fine, Switching between modes was fine.

i switched everything on at the field, leveled the plane, performed a 35MHz radio, and 3dr radio range check. 

Created a w/p file...

Took off in manual mode, flew to altitude, switched to auto, the plane then started following way-points, it got to number 3 (I had speech enabled so can verify this is correct) .. and before it got to number 4 it just flew off due west, i realized it was heading into the abyss, so switched back to manual mode to bring it back, flew it back above the home location, then switched to auto again, the plane did a bit of a wing wobble, and oscillated about 6 times, only slightly, from a 15 degree roll left, to a 15 degree roll right, then the plane started heading back to the same direction it was header for before. 

So i switched back to manual, tried to bring the plane back, it proceeded to go inverted, I was unable to recover and flew inverted into the ground on a 25 degree angle. 

It made a bit of a mess, Futaba reciever is knackered, should be fixable with some glue! wing and tail section is fine, the bands came off without any problems... 

Naturally I thought i'd view the log file, but upon connecting to the APM, it said that no dataflash card was found, so i took it out and put it back in, this didnt work, so i did a reset, and whilst clicking around I believe i deleted the files from the on board log card. After doing a reset, I have managed to get the APM2 to stop saying ' no data-flash card connected'.

So i guess the crash upset the APM2 a bit! but all seems to be fine, after connecting it back up.

I have made several successful flights with this APM. therefore i must have crashed due to something that i changed for these flights.. here are the differences......

• 3DR Radios were connected, but seemed to be working okay, I didn't use the laptop to perform any commands during the flight, I only used the 35mhz tx to change modes, and guide plane where necessary.
• Pitot Sensor was enabled

I cant see any of the above causing any errors, except interference between the GPS, 433mhz 3dr radio and 35mhz radio.

I have uploaded the tlog and rlog files, but cant seem to find whats wrong with them.... The flight starts about half way through ... 

Any help gratefully appreciated! 

The good news is that the camera that was in the wing survived...and i got some decent pics, very crisp at 1/1000th!

 

Attachments:

• 2012-06-17 14-39-38.tlog, 1.8 MB
• 2012-06-17 14-39-38.rlog, 1.4 MB

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ModeratorPermalink Reply by Gary Mortimer on June 17, 2012 at 11:45am

You know that you will only be able to use half of the images in a lawnmower pattern??

Those waypoints are far too close, unless you have really nailed your PIDs

Better to fly higher in a straight line and get that plot once.

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Permalink Reply by Richard on June 17, 2012 at 3:20pm

Hi Gary, I'll do fewer waypoints next time. Is there any reason I will only be able to use half of them? Is it because the plane will be taking pics at an angle at both ends?

I think the limit is 400ft in the uk,which is kind of annoying. I have read 150-200 meters is best optimum height to fly. The good news is that I think I now understand the limits of my camera and plane setup. I need to use 1/500 or above shutter to get decent pics,

Still trying to figure out the cause of the crash. Hmmm :-(

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Permalink Reply by R. D. Starwalt on June 17, 2012 at 1:13pm

I am sorry to hear of you mishap/crash. You are past due for some good luck.

In regards to the inverted event, did the aircraft roll to inverted flight? It sounds as though that was the case.

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Permalink Reply by Richard on June 17, 2012 at 3:14pm

It did roll inverted and almost stabilized itself inverted as well, couldn't roll out of it with the sticks, note to self, set auto pilot at 200m minimum!

The only trouble is the max altitude in the uk for rc is 400ft :-(. Fingers crossed I'll find the cause and have a few successful flights this week!

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Permalink Reply by Richard on June 18, 2012 at 3:07pm

The Skywalker is almost all glued back together, i am not sure it will take another crash! Thinking of making some sort of foam lined box for the APM and 3DR radios, should it crash again. I was fortunate that nothing broke. 

I would like some advice from fellow skywalker users....

Where do you mount the APM?

Where would you mount the 3DR radio?

And does it matter how close the 35mhz reciever is to the gps and 3dr radio? 

I am hoping to fly her again tomorrow if the weather is nice... may make an emergency parachute system until i am confident with the autopilot, and my building skills! In parallel to this I am making a scratch build airframe that can accommodate a nice roll gimbal...

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Permalink Reply by Richard on June 24, 2012 at 1:09pm

Update.. Another Crash  :-(

Well, not sure what happened tonight, but the Skywalker went into a spiral dive at a fair rate of knots whilst it was supposed to be following waypoints, it proceeded to go quite a long way in the wrong direction, I switched to stabilize, and it spiralled down and crashed good and proper, it was the first flight since the last repair. It seems there is a bit of a delay between switching modes, ie, from auto to stabilize. Anyway... It caused some serious damage... Unfortunately some of the pins are touching so i'm not going to plug it in,

Skywalker, completely trashed this time... Around £90 with postage and taxes

APM2 Board, £180

Ixus 80 Camera, got it form ebay for £40

5000mah battery quite badly damaged - £25

1300mah battery quite badly damaged - £11

Grand total - £346! 

And some pictures of course...

APM2 board - Pins quite badly damaged

Anyway, not losing heart, I am going to have a fresh start with some new equipment....I think I will try to build 2 setups, as when one crashes I can continue with the other one, Here are my thoughts,

New Airframes for testing purposes

2 x Easystar 2's - Cheaper to buy them as a kit fro the UK, as opposed to hobbyking version as shipping is expensive. I dont intend to use cameras on these, they are purely for APM purposes.

APM

Not sure what new autopilot to buy, Is it worth buying an APM2 again? has anyone any thoughts on how to house it a bit stronger, it's the most valuable part of the setup, It will be a few weeks before I have saved enough to buy new stuff. Does anyone reckon from the pic any of the board is salvageable? like the GPS maybe?

One step forward, 2 steps back! - Keep trying! 

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Permalink Reply by Richard on July 1, 2012 at 7:27am

APM2 maybe working, the pins have been straightened by a technically minded person! Hopefully it'll work, i've plugged it in and all sensors seem to be okay. Instead of wrecking another airframe,

I have taken Gary's advice and am using a flying wing for now, i used to crash this all the time and throw it back i the air with no damage...

The 3DR Radio is also installed and i will be using this form now instead of the USB Lead. If I can make 5 consecutive successful outings with no crashing, I will concentrate on the Airframe build.

I will sort the gimbal issues out on that airframe once its built. I am allowing plenty of room for camera rotation.

 

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Permalink Reply by R. D. Starwalt on July 1, 2012 at 8:15am

Good news on the APM2 and thank you for the update.

The usual kiss-of-death for those connectors is when they break off and they usually break off flush with the plastic that is closest to the pcb. I can count on less than one hand the number seen broken off and suspected that they could be sorted out.

I wish you Good Luck in the transition period.

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Permalink Reply by Richard on July 5, 2012 at 2:25pm

Update - Things have been moving a little slowly as we've had some bad weather here in the UK, but i did have a successful flight tonight with my home made 66 inch zagi. with no crashes.... Had to do a spot of PID tuning at the field, but all in all it worked well... the 3dr radios are great, no more plugging cables in!

Wing still in 1 piece...

Thats flight 1 of 5.. if i get 5 successful consecutive outings and flights, i will consider moving the APM2 into a more expensive airframe.... 

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Permalink Reply by James Kirkley on July 5, 2012 at 11:33pm

On your vibration issue and blurred pictures. There was one set of your pictures showing your large plane labled "tidying the wires" and "insuite camera". It looked like your camera was housed in a fixed internal box made with plywood or bulsa, with the camera pointing straight down through a hole in the fuselage. Maybe you could try to make that box a little larger and line it with bubble wrap, bottom, sides and top. Then lightly secure the camera with velcro straps over the top layer of bubble wrap.

I guess it's worth a try. I can see where even soft foam, like weather stripping, or those sheets thin foam packing material, still may have enough mass and stiffness to transfer vibration. But bubble wrap has a failry small mass, coupled with air cushions it may act more like a shock absorber.  I'm speaking about the thin bubble wrap available at office supply stores as well as the post office. Two of the common bubble thicknesses are 3/16(4.5mm) and 5/16 inch(7.8mm).

I'm not sure how a gantry can fix vibration and blurred pictures. It may keep the camera pointed straight down, but the vibration from the motor itself will still be transferred through the arms of the mount. Gyros can can make the plane fly smoother, or a camera point in the same direction, but they will do nothing to dampen motor vibrations that are happening at many thousands of RPM. This requires a true shock absorber. Of course, if the bubble wrap works as a shock absorber it should work equally well in the gantry configuration. Just use the bubble wrapped box to house the camera in the gantry setup.

If pristine bubble wrap isn't working, experiment by poping every other bubble. See if that improves the shock absorbtion. Make a couple of boxes, and make them removable, so you can easily swap them in and out to test the different setups held in by the the single set of velcro tabs in both the fixed internal configuration...or mounted to the gantry.

 

 

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Permalink Reply by James Kirkley on July 6, 2012 at 6:34am

If bubble wrap doesn't work try these to line your boxes:

At your home store get some insulation batting that looks like cotton candy. The only downside is that this may be irritating to the skin.

Along those same lines is the batting and fiberfill available at your fabric store. You want something that comes in sheets and isn't loose fiber. Explain what you need to someone, as there may be multiple locations in the store where material like this is available.

Or go to the bandage section of your Drug Store and look at the cotton bandage options. You probably want something that looks more like raw cotton than something that looks like fabric. But if you can find a pillowy enough fabric give it a shot.

There is also a cotton bandage available for horses hooves. It's a 1 pound roll 12" wide and 5 to 10 feet in length. It's readily available on the internet for $4 to $5.

Of course you can still attempt to find a soft enough compressible foam that will work, although foam is still one solid piece of material which works against vibration dampening.

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