I've been working for the last few weeks on developing a parachute recovery system for E382s to reduce the need for manual flying. I know from my own experience that any time a human is at the controls, the risk of crashing is significantly higher. Parachutes have been made for small aircraft before but they're often implemented in an expensive or complicated way. The idea here is to make a simple, working parachute that reduces the overall risk of damaging the aircraft, is simple to use and cheaper to install.

Building the parachute itself was pretty easy, I used this gore size calculator by Scott Bryce and just printed the gores out as patterns. I accidentally printed the pattern out on 8.5x11 instead of 11x17 so this parachute is actually only 22" diameter - much smaller than what it should be for this weight. The gores are cut out of black rip stop nylon and just sewn together. The lines are attached at 8 points, with the lines simply tied through button holes. The line I used is too thin to be sewn into the material but I prefer the thin line, made of kevlar, for its weight and size.

20130630_181911

Next I ran a few tests using some dummy mass at about the same weight as an E382, 1.70 kg, to see how quickly it would fall and if it would even open up properly. The first few tests were done with the parachute already pretty much deployed as it was from a pretty low altitude off my building's fire escape.

WeightToss1.Still001

 

I thought the speed it hit at was slow enough, despite the smaller chute size, to not significantly damage an airframe and decided to move on with the tests. So I attached the parachute to a light-weight (1.5kg) airframe to see how it would fall and if the wings would affect the speed significantly. Because of the smaller size of the parachute, the airframe was actually still had almost enough lift to fly itself. So as it fell and built up speed, it would begin to pull out of the dive, then the parachute would slow its horizontal movement and it would stall, then presumably repeat until it hit the ground. In a few of the tests, the parachute line also got caught under the horizontal stabilizer, further complicating the problem.

Plane2.Still001

Not wanting to call it a day, I pressed on to simulate the actual deployment. Ideally, the parachute would deploy on its own, be near the center of gravity and allow the plane to fall down roughly level and impact the ground on its belly. That all points to a deployment from on top of the wings, right in front of the motor. On the first try, I loosely packed the parachute on top of the wing and just tossed it. This allowed it to catch wind almost immediately which promptly pushed it straight back into the tail, where it lodged itself, allowing the plane to crash at high speed.

Plane123.Still001

But I tried again, packing the parachute more tightly so it would roll out past the tail in a compact ball before opening up and catching wind. That did the trick! The dive/stall issue is still there but that should be fixed with the next parachute build.

Plane4.Still001

 

All four tests above plus one more live deployment test on a flying plane are in the video below.

Would you ever use a parachute as your primary recovery mechanism? Why or why not?

Views: 6629

Comment by Maxime Carrier on June 30, 2013 at 6:59pm

I was thinking about using gun powder for fast deployment but we need to refill it every time and need some test to get good mixture, also we need a relay to trigger detonation. Anyone tried using 12g CO2 with electro-valve or spring/servo ?

Hearing the sound I'm surprised your air frame was not smashed ;) 


3D Robotics
Comment by Chris Anderson on June 30, 2013 at 7:09pm
Great post! Would a bigger parachute slow it down enough to avoid the stall/dive issue?
Comment by Sam on June 30, 2013 at 7:39pm

i don't like that sound either, but i love the idea!!!! what about gutting an air-soft gun for the CO2 system for fast parachute release?

Comment by Jeff Taylor on June 30, 2013 at 7:46pm

@Max I know I've seen someone using at least CO2 canisters for deployment somewhere, can't recall where at the moment. In the third test it was smashed! If you look frame by frame at the GoPro video of that hit you can see the nose temporarily disappear... Nothing a little tape couldn't fix though.

@Chris Thanks! Yes I think so - right now it's falling at as much as 6.8 m/s and at that weight I'm not surprised it's pulling up. The properly sized chute which I'll build soon should drop it to 4.5m/s or so, hopefully that's well below stall speed.

Comment by Stephen Gloor on June 30, 2013 at 8:26pm

Have a look at the Aeromapper for ideas - they have a parachute recovery:

http://aeromao.com/aeromapper_uav

This was a discussion a while ago:

http://diydrones.com/forum/topics/co2-parachute-system?xg_source=ac...

Comment by Matt on June 30, 2013 at 8:26pm

I would go for the gun powder release method. A small pill container that you can find at wolldy world, you can even get them on ebay. Drill a small hole into the bottom of hit, insert a 209 shotgun primer. Attach it to the bottom of a small cylinder, stuff the shoot in the cylinder, then just use some spring loaded mechanism/servo contraption to strike the primer. Of course you would have to use a flame retardant shoot. And you would have to get the amount of gun powder just right or risk blowing up the craft in mid air. I have done similar test such as these. You just need to make sure that you can control the path that the small explosion will take, presumably the path of least resistance into the shoot and pushing it out of it's container.

Comment by Matt on June 30, 2013 at 8:27pm

Now that I look back on my hastily typed reply. I can't spell worth crap! 

Comment by Rob Bartlett on June 30, 2013 at 8:36pm

I've had some success igniting Pyrodex (a Black Powder substitute) with electrical current applied to a small wad of steel wool.  That's how I plan to deploy my parachute once I get some time to work it out.  

I like that approach because it's stupid simple.  I considered relays, solenoids, etc and decided that it was just too complicated.  Steel wool never fails.

Comment by Matt on June 30, 2013 at 8:47pm

Can't go wrong with Pyrodex. I use it in everything.


Moderator
Comment by Nathaniel Caner on June 30, 2013 at 8:49pm

Once upon a time I used to be involved in Amateur Rocketry and we used to make our own igniters by dissolving ping pong balls, which are made of Nitro Cellulose, in Acetone then mixing that with our pyrotechnic charge (usually black powder). At this point we would strip two electrodes, take a piece of high resistance wire (Nichrome or similar) I used galvanized picture wire. I would wrap this around one electrode and short it out to the other then dip this assembly in the dissolved ping pong ball/BP mixture, hang and let dry.

Once dry they would provide a reliable pyrotechnic charge that was easily ignited with 12v in less than 1/4 second at about 12 Amps.

That said I think it's likely that this might be illegal in most areas to carry any kind of pyrotechnic on a model aircraft. I think Co2 would be a safer way to go.

I have also seen a rig where a servo released a pin that opened a panel in the casing holding the parachute allowing a rush of air that ejected the parachute.

There are a lot of ways to do it and that's part of the fun isn't it?

Regards,

Nathaniel ~KD2DEY

Comment

You need to be a member of DIY Drones to add comments!

Join DIY Drones

© 2019   Created by Chris Anderson.   Powered by

Badges  |  Report an Issue  |  Terms of Service