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Old Oct 27, 2014, 12:03 PM
Registered User
United States, CA, Long Beach
Joined Oct 2014
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Need V-tail help

Does anyone no what would happen on a v-tail controlled by two servos if one of those servos failed?

During a preflight inspection i noticed one of my servos wasn't working. Unplug battery plugged back in and it starting working normal. Ground tested for a while, and it continued to work? ( I think you see where this is going)

Flew the plane, its a glider that I fly light acrobatics with. In the middle of a standard loop with plenty of glide speed (no motor) the glider went into a nasty spin that I have never experienced before with this glider. Was not able to recover. Hardly any damage though, which was amazing with how hard it went in.

Servo is very new spektrum digital.

Any ideas on the spin cause and/or what the servo issue might be.

Maybe I just stalled the tail (again I have done more aggressive maneuvers than what I was attempting when this happen with no issues). Servo was working when I got to plane.
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Old Oct 27, 2014, 01:55 PM
IT'S NOSE HEAVY!!!!!!!
cityevader's Avatar
United States, CA, San Jose
Joined Mar 2012
3,364 Posts
There'd be a bit of redundancy...sort of.
My planes have way less elevator throw than rudder.
One could possibly use rudder command to give a boost to the "half elevator"...assuming it was readily recognizable in the air which servo failed, and which way to hit the rudder, in order to get enough elevator control. It'd be kinda tricky depending on altitude.

Planes can stall/spin regardless of airspeed.

Easy answer...don't fly with questionable equipment...replace the servo and receiver.
Or...wait until it happens again (on the ground) and swap the servo leads. If the same servo is inop, replace it. If the other servo is inop, then replace rx.
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Old Oct 27, 2014, 02:28 PM
Registered User
Joensuu, Finland
Joined Mar 2002
1,630 Posts
If only one surface of a v-tail is moving, you will get both elevator and rudder effect regardless of what you are doing with the tx. For example, if the left surface stays neutral and you pull up elevator, you get nose up and left.
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Old Oct 27, 2014, 02:31 PM
IT'S NOSE HEAVY!!!!!!!
cityevader's Avatar
United States, CA, San Jose
Joined Mar 2012
3,364 Posts
For some reason, I was assuming it had ailerons (all my planes are aileron-ed), so it wasn't to big a deal in my head...but if a rudder/elevator plane, that would be more of an issue.
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Old Oct 27, 2014, 03:11 PM
Registered User
United States, CA, Long Beach
Joined Oct 2014
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yeah, plane has ailerons. It was such a violent stall and spin it was hard to see what might have been the cause. That's why I question the servo, but I don't have a lot of experience with V-tails. The plane is the Eflite allusive. Has a large v-tail, so maybe my elevator throw is too high. But like I said, I had a flight about an hour before the crash and was pushing the plane pretty hard, and even had a more experienced pilot fly and do some acrobatics just as testing the new planes abilities and no problems presented themselves. Its normal stall is level with nose down.
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Old Mar 09, 2015, 06:59 PM
a.k.a. Bob Parks
Glendale, AZ
Joined Jun 2008
2,499 Posts
Old thread, new response.

My V-Tail sailplane with its old DSM-2 rx and carbon mix fuse would loose signal and do that occasionally. It has always recovered before impact.

Switched to a better radio & problem was gone. The original rx did not have long antennae and had limited reception, before I extended the antennae by 62mm.

BP
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Old Mar 09, 2015, 07:10 PM
May the Wind Always be Good
Webster, Minnesota
Joined Feb 2007
524 Posts
If a Servo is not Working Right Get it out and Replace it before Flying ..They Just Do Not Fix Them Self ...
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Old Mar 10, 2015, 10:16 AM
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Belgium, Flemish Region, Oosterzele
Joined Dec 2001
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if the spin started near the top of the loop you have too much elevator throw...
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Old Mar 10, 2015, 01:51 PM
Registered User
Joined Oct 2004
766 Posts
No question , don't fly with any piece of equipment that even flinches . Cut the connector off right at the case so you won't be tempted to use it . Servos are cheap , the loss of a plane is not cheap.
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