Aerosonde UAV

[reinking]

Anyone care to comment on the tail structure of this vehicle?

"Aerosonde™ UAV. 2.9-m wingspan. 13-15 kg weight. The first unmanned aircraft to cross the North Atlantic"

aerosonde-uav-bg.jpg

aerosonde.jpg

I hope these images come through okay. If not see-
<http://www.aerosonde.com/aircraft/>
<http://cires.colorado.edu/~maurerj/class/UAV/aerosonde.htm>

[Sparky Paul]

Comment in what way?
I use that configuration a lot.

[Bg~]

Probably the most structurally efficient way to get elevator/rudder control given the twin booms.

[Sparky Paul]

The pusher motor keeps the sensors out of the exhaust wake.
Balancing the motor and booms needs a longer than usual front end, which permits more/heavier sensors instead of ballast.

[ghoti]

Two tail surfaces instead of three. One less tip vortix, reduced weight and drag, whether upright or inverted. I read that an inverted V-tail exhibits less cross coupling of controls than either upright or conventional type tail. Should be good for pattern planes and aerobats?

I made an inverted V-tail for my two boom/two motor slowstick. Well it made four short flights and crashed on he 5th. Never got back to more testing, but it was a raskel to fly. That says little about V-tails and a lot about my design and flying skills. Bill

[HELModels]

What is the advantage of having the narrowest part of the semi-spans at the apex of the tail? Is this because the drag where they meet each other is greater than where they meet the booms, so might as well minimize drag where it counts?

[Sparky Paul]

I don't know there's any advantage. I just like the looks.
Aerosonde doesn't taper theirs.

[davidfee]

I was thinking you could probably make a structural argument for the taper based on mass distribution and load paths, but I agree that for most models it's probably not a significant consideration.

[HELModels]

It all depends on what you expect from a model. If all you expect is for it to fly, then nothing matters much. I dont totally believe Sparky. :p He doesnt seem like the type to be real concerned with esthetics, but he is practical.
I think it is possible he has reduced interference drag at the junction of the 2 tails simply because the length of the junction is reduced. The reversed taper puts a greater majority of the tail area, for that taper ratio, out of the junction, which gots to be gooder.

Only notable on the aerosonde tail, in comparison, is that the tail has high aspect ratio and straight taper.

[RCAV8R13]

Anyone care to comment on the tail structure of this vehicle?

"Aerosonde™ UAV. 2.9-m wingspan. 13-15 kg weight. The first unmanned aircraft to cross the North Atlantic"

I hope these images come through okay. If not see-
<http://www.aerosonde.com/aircraft/>
<http://cires.colorado.edu/~maurerj/class/UAV/aerosonde.htm>
I would be glad to comment on the Aerosonde tail. IT SUCKS!
Now, before you say, "Who the heck are you? And why do think you know soo much?", let me introduce myself, I'm Kip Jackson, Isitus' test pilot. I have built and flown every Aerosonde Insitu has ever produced. I built and performed the take off of Laima, the Aerosonde that flew across the atlantic (as well as Millionare, Trumper and Piper, the Aeronsondes that didn't make it).
The original tail on the Aerosonde, was a noodle. The booms and the tails where too soft. We were deployed in Tofino, on Vancouver Island Canada. We had some problems with the airspeed indicator and I had to land twice at full gross on wet pavement. I ran out of up elevator each time I tried to flair and the plane would bounce off the runway before I could then flair and land and slide and slide and side. I think it slid for 100 yards on that wet pavement. After looking at the video it was apparent that the booms and tails were bending. Combined with the high gross weight and forward C.G., I just could not get the nose up.
I also don't like the way V tails fly. They tend to swish around the sky.
An inverted V tail does have a little yaw to roll coupling and both in the same direction, other than that.. I just don't like V tails.
Just my two cents.
Kip

[HELModels]

I dont doubt your first hand impression, but it reads like you were negatively impressed by structural flaws. I like the V-tail I built, but it too flew swooshy all over the place when it had a cracked boom. It handled like a wet noodle until I replaced the boom. It also sounds like your impression of a particular airplane lacking elevator authority should be attributed to design and flight configuratin only and not concept of a V-tail or A-tail.

I'm not defending aerosonde or V-tails necessarily, but just shooting the breeze here. Well, yeah I am defending v-tail concept a bit, just not aerosonde. Aside from the beginner problems I've experienced with my plane, the plus's of a 2 panel tail outweigh any quirks those who swear by conventional tails insist plague V's.

It all good from here. :)

[Sparky Paul]

The amount of drag due to the interference at the junction of the vees is micro ounces.
The effect of one shape over another would make itself known in flight only after a very long flight.
I don't make very long flights, so I do what works. :)
.
Boom bending is a major problem, regardless of the empennage configuration.
The down-load on the tail gets quite large with increasing airspeeds, and can force the entire tail down, which is a dive, which is usually terminal.
.
Kip's experience is the result of insufficient elevator authority more than anything. Booms that bend make themselves obvious by the dive problem.
On single boomed vee-tails, I've had the boom twist, so the vee at times resembles a conventional tail, less one half the the horizontal.
This can be amusing/not good.... depending on the plane.