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Old Jul 14, 2011, 11:13 PM
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Dudley Dufort's Avatar
Rio Linda, CA
Joined Feb 2010
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I can't see it!

We've all done it; lost sight of our plane. Most often we reacquire before disaster strikes but occasionally some of us wind up with a plane in a bag.

I lost sight of my MXC at Montague. When we spotted it, it was in a steep dive on the cusp of terminal velocity. A moment later it exploded. I wish I could claim that this was the only time this has happened but over the years, I've kept the guys at R n R busy.

My latest experience got me to thinking about setting up a switch on the transmitter for those instances when the plane disappears. An "I can't see it" switch.

So here's my question; which surfaces what direction?

While talking with Dean, I recall him saying that those settings would differ with plane type. What might work on an MXC would be different for an SBXC. So, I guess I'm asking two questions since I fly both.

Dudley
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Old Jul 14, 2011, 11:57 PM
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Dudley
What is wrong with full up and full ruder left or right? I have done just that with my eagles and they go into a harmless spin making it easier to regain sight when at altitude. Try it at a comfortable altitude and see how it works
Jim
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Old Jul 15, 2011, 08:13 AM
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Colombia, Antioquia, Girardota
Joined Mar 2001
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Spinning the plane is one way to make it flash, others recommend looping the plane. It all depends how the plane does it, so it's important to try it out before it's needed.
If I lose sight of one my full-house planes, I simply apply full landing crow, i. e. flaps all the way down, ailerons up a bit (depending on the individual plane). This slows the plane and settles it into a slight nose-down descend. This buys time to search the sky. The longest it's taken me to re-aquire a glider this way was an eternity of probably 5 seconds.

Dieter Mahlein, ShredAir
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Old Jul 15, 2011, 10:11 AM
Master of the Wind
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United States, CA, San Jose
Joined Sep 2008
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Pulling the flaps dirtys up the profile and gives you more facets to view.
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Old Jul 15, 2011, 12:26 PM
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United States, CA, Diamond Springs
Joined Mar 2004
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Bill and I conducted some experiments with Super Supra. We have two alternatives, first being failsafe which is turn off the transmitter and the plane deploys landing flaps some down elevator and some rudder to put it into a large descending circle. The second method is to pull up elevator and loop it until re-acquiring visual.

Both work but there are possible problems in deploying failsafe too late with the glider at a high rate of speed. We havent had the guts to try it at high speed. Failsafe works at low speed though. For the second "Loop" method it would be necessary to gradually pull back on elevator in case the glider is in a dive and at high speed. Simply yanking on elevator would likely blow it up in that situation. That is probably how the Autonomous team lost their auto pilot SBXC a couple years back at Montague.

To test the loop method we put Super Supra in a dive, pulled up elevator all the way and she entered a series of loops that over time became a combination of big stalls and loops but she never entered a death spiral. We tested this several times for a couple minutes each test so I'm inclined to use the looping method. The big problem is having the discipline to realize you are in trouble and pull up elevator soon enough. That is surprisingly hard to do and there seems to be a natural tendency to keep searching and wait too long before going for the loop recovery.

Steve
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Old Jul 15, 2011, 05:34 PM
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USA, IL, Wheeling
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I'm thinking you should program a flight mode for this, and then dial in the longest delays possible to reduce the sudden stresses that might be imposed on the airframe ... lose sight, flip the switch and start scanning.

tk
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Old Jul 15, 2011, 06:50 PM
yyz
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For some interesting reading, Google "benign spiral mode".

Mike
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Old Jul 15, 2011, 09:10 PM
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San Diego, CA
Joined Aug 2004
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Quote:
Originally Posted by tkallev View Post
I'm thinking you should program a flight mode for this, and then dial in the longest delays possible to reduce the sudden stresses that might be imposed on the airframe ... lose sight, flip the switch and start scanning.

tk
I like that suggestion.
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Old Jul 16, 2011, 01:14 AM
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Joined Nov 2004
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I think these $2000+ birds need a switch activated 4' droque chute on a releaseable tether...for the times when 30 seconds pass without a sighting.

Of course that would add an extra 6 oz and cost an extra $4...but hey, insurance isn't cheap.
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Old Jul 16, 2011, 10:31 AM
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My SBXC save a glider technique is crow and the right stick in a lower corner. This works well if you don't delay too long.

Because of the flap hinging method on the MXC not alot of deflection is possible. For me it's 40 deg. max and usually settle on less to keep servo draw to a minimum.

Crow or full flaps and right stick in a corner will result in a spiral dive with VNE exceeded in a few seconds.Simply pulling right stick back and looping has worked dozens of times for me. Again not waiting too long is the key.

To become comfortable with any technique practice at your home field or before going on course.

Regards Dean
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Old Jul 16, 2011, 01:06 PM
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Lakewood, Colorado
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Quote:
Originally Posted by yyz View Post
For some interesting reading, Google "benign spiral mode".

Mike
I think one key to benign spiral mode is that the control surfaces are
free to move themselves (hands off the stick and rudder). That's generally not
possible with an R/C plane where the servos will hold the surfaces in place.

I also think one key to finding a lost sailplane in the sky is to make sure it doesn't
transit the sky horizontally quickly, and the benign spiral mode or similar doesn't
guarantee that. That's why some way to put it into a slow descent spin or
continuous loops seems to work best. I like continuous loops or stalls
(basically just holding full up elevator).

ian
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Old Jul 17, 2011, 02:08 PM
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United States, CA, Diamond Springs
Joined Mar 2004
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The number one visual aid when flying at extreme distance is a second pair of eyeballs. This has saved my teams glider many times. When flying at high altitude or cutting corners real deep we always make sure to have both sets of eyes glued to the plane. And even then we've lost it, usually due to the sun or turning out of a distant thermal head on to our location in the vehicle and the small frontal cross sectional area causes the plane to simply dissappear. So now I try to keep the angles in mind and when leaving a thermal that is well off the road I head at a connecting angle rather than straight at me. Once in cruise in the 10-15 degree cone overhead keeping sight of it is much easier.
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Old Jul 18, 2011, 11:37 AM
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I'm a big fan of the spin technique. Nothing grabs your attention better than an object that is oscillating and/or flashing in some way. Even if your plane is light blue and it's a cloudy day, you'll be much more likely to lock in on the movements provided by a spinning plane in my opinion. The other main advantage of this method is you won't end up flying further than the wind might carry you if you lose sight when traveling away from the field. Never do nothing with the sticks while trying to acquire visual. Full up would work too but I believe you have the best chance of spotting the plane when spinning.
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Old Jul 20, 2011, 03:51 AM
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Sydney
Joined Apr 2009
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I would plug for spinning the model down both because of the better chance of flashing and for the reduced drift with any wind, so that it will drop closer to the last reported position.
However many gliders do not have enough elevator to do a fully developed spin and could go into a spiral dive which could be fatal due to the speed build up. It will be even harder to induce on large XC models with their longer spans and higher inertia and they could be harder to pull out, so this would need to be explored carefully.
For cross country models - there is a strong case for having a special emegency flight mode which has been pretested to produce a fully developed spin. The elevator throw could be increased to ensure a full stall and aileron introduced on a delay for example.
As mentioned the pilot needs to not delay before making the decision - a minimum of 1-2 secs at most I would think.
On the rare occasion I was able to introduce a spin on one of my 2m's it dropped almost vertically at a reasonable rate and was spinning rapidly.
John
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Old Jul 20, 2011, 10:25 AM
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Keep in mind my comments are for the MXC and SBXC only which were the gliders that Dudley asked about. They are the only RC gliders that I have flown enough to comment on.

Regards Dean
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