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: 6671


Developer
Comment by Randy on July 1, 2013 at 1:26am

I personally would much prefer the CO2 or servo based deployment mechanism.  I'm more on the arducopter side but if someone would come up with a nice reliable deployment method we could incorporate the code changes in so that it's triggered automatically when the copter senses that it's lost control (i.e. desired roll/pitch do not equal actual roll/pitch).

Comment by Austin Laws on July 1, 2013 at 2:56am
U need a bigger chute mine is 1.25m check out my video. Chute from ebay £25 not cheap but very gd. http://m.youtube.com/watch?v=MCY7IyOl0M0
Comment by Rob Bartlett on July 1, 2013 at 5:27am

Here's a cheap and simple method for constructing a parachute, from Experimental Airlines:

http://www.youtube.com/watch?v=kXqH3daEgAo

Comment by Stephen Gloor on July 1, 2013 at 5:31am

The best parachutes I found were these:

http://www.the-rocketman.com/chutes.html

They are for high power rocketry and include tables for descent rates.

Also there are these for UAVs

http://www.the-rocketman.com/model-recovery.html

Simple spring loaded ones might do the trick

Comment by Crashpilot1000 on July 1, 2013 at 9:58am

This has been done in several incarnations already. Here is something more sophisticated: http://ecilop.tv/data/video.phtml#Anchor--Eci-9028

Others with those "CD case Copters" just put the chute on top of that secured by rubber/released by servo.


Developer
Comment by Mark Colwell on July 1, 2013 at 10:28am

I recycled a large umbrella 56", it fits in a 3" plastic shell launched by airbag setup, Inverted bladder fills with gas pushing shell with parachute out at speed. Chute is packed accordion style allowing fast air fill. Shoots past props and tail. Bladder is kevlar cloth with vents to allow excess gas release at full deployment. I may use pyro 209 primer, as CO2 would be too heavy.

Comment by Crashpilot1000 on July 1, 2013 at 10:56am

Developer
Comment by Mark Colwell on July 1, 2013 at 11:09am

Works great! 5 meters! wow!

Comment by Ian on July 1, 2013 at 7:49pm

Pretty cool.  What about using a parachute as a break rather than just a recovery system?  I am working on a ground vehicle and I'm thinking of something along the lines of chutes used for drag racing.  Do you think the chute needs to be larger for that purpose?  Did you find any calculators for speed rather than just weight?  I would think the  chute doesn't need to be bigger per say, but the tension strength of the lines might be more important...


100KM
Comment by keeyen pang on July 1, 2013 at 8:35pm

A parachute recovery system will surely reduce the risk of damage during landing by a newly trained pilot. If we have an ideal landing area, then the autoland function is good enough to land the plane safely. But if the landing area is limited, manual landing is next to impossible for a new pilot. 

In my opinion. landing has become one of the major obstacle to make the low cost UAV system more accessible for the general user or researcher. They don't want to learn to fly RC as a hobby, they just want to use it as one of their tools. 

Therefore develop a functional, reliable and low cost parachute recovery system is very important. I hope Jeff will continue to refine his " prototype "

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