TWIN-BOOM, V-TAIL, & FLYING WINGS
Dave
factor) :
1. Twin-Boom Fuselage
2. V-Tail
3. Flying Wing
Your Thoughts?
townes de wombat
>What are the cons/pros of (especially their contribution to stability
>factor) :
>
>1. Twin-Boom Fuselage
The Burnelli link below will give you some info. It seems that safety of
passengers in a crash is one of this configurations great pluses. Also
in the pre computer age they are easier to pilot than a Flying Wing. As
to all the Burnelli conspiracy guff, I don't know if it is valid or just
paranoia.
>
>2. V-Tail
See the link.
>
>3. Flying Wing
I read an article recently (on the net but I confess I didn't keep the
thing) that the FW is inherently instable. In those far off days pre
computer age the number of controls made them very difficult to handle.
Supposedly computerised flight controls could solve this problem making
the FW a viable design in the future..
>
>
>Your Thoughts?
Hope this helps. Undoubtedly other more technically minded and
knowledgeable (sic ?) souls can give you even more info.
>
>
Try these links.
http://www.aircrash.org/burnelli/index.htm
http://www.fatlion.com/sailplanes/vtail.html
http://www.airandspacemagazine.com/asm/Mag/Index/1997/JJ/teds.html
Jon
> What are the cons/pros of (especially their contribution to stability
> factor) :
>
> 1. Twin-Boom Fuselage
Extra drag for not much gain if any.
>
> 2. V-Tail
No gain whatsover, and problems with stability near the stall.
>
> 3. Flying Wing
reduced drag, reduced everything, tricky to keep stable in flight.
The only one that really works costs about USD$1 billion.
>
>
> Your Thoughts?
matt weber
de wombat) wrote:
>On Thu, 6 Jun 2002 13:57:31 +1000, "Dave" <n...@spam.com> wrote:
>
>>What are the cons/pros of (especially their contribution to stability
>>factor) :
>>
>>1. Twin-Boom Fuselage
>
>The Burnelli link below will give you some info. It seems that safety of
>passengers in a crash is one of this configurations great pluses. Also
>in the pre computer age they are easier to pilot than a Flying Wing. As
>to all the Burnelli conspiracy guff, I don't know if it is valid or just
>paranoia.
>>
>>2. V-Tail
>See the link.
The problem with the V-tail is structural loads are difficult to
calculate. It must have taken 30+ years to realize they were wrong in
the Beechcraft airframes, because the AD to fix it doesn't appear
until the late 1980's, but goes back to the first production models. A
number of V-tail aircraft were when for no obvious reason, the tail
plane came apart. The problem was recognized until someone finally put
strain gauges back there, and discovered the loads were a lot higher
then they were supposed to be.
>>
>>3. Flying Wing
>I read an article recently (on the net but I confess I didn't keep the
>thing) that the FW is inherently instable. In those far off days pre
>computer age the number of controls made them very difficult to handle.
>Supposedly computerised flight controls could solve this problem making
>the FW a viable design in the future..
Inherently unstable aircraft are likely to be the most efficient
airframes. We make platforms stable by putting drag in the right
places. Platforms that are unstable don't have enough drag in the
right places, but drag is clearly the enemy of air frame efficiency.
The Flying wing relied on a Minneapolis Honeywell autopilot to provide
some semblance of stability in flight, but as a bombing platform, by
all accounts, the prototype wasn't stable enough.
As you suggest however, fly by wire and computer control make all
sorts of things possible,such as high alpha low speed passes,
dramatially forward swept wings, as well as airplanes that don't look
especially like aircraft, like the F117....
Dennis Jensen
news:ds70guk79nd9pkghe...@4ax.com...
Done by F-15 quite a while back with no computer control.
> dramatially forward swept wings,
This is not an aerodynamic problem, but a structural one, as fluctuations in
wing AOA are positive feedback (the wing wants to twist more). That was
solved with composite materials, the aerodynamic issue per se is not a
problem (there were jet aircraft as far back as WW2 with forward swept
wings).
--
Dennis Jensen
Author of "The Flying Pigs"
http://www.ebooks-online.com/ebooks/search.asp
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Eric J. Whitney
> On Thu, 06 Jun 2002 23:30:06 GMT, townes4...@hotmail.com (townes
> de wombat) wrote:
>
> >On Thu, 6 Jun 2002 13:57:31 +1000, "Dave" <n...@spam.com> wrote:
> >
> >>What are the cons/pros of (especially their contribution to stability
> >>factor) :
> >>
> >>1. Twin-Boom Fuselage
> >
> >The Burnelli link below will give you some info. It seems that safety of
> >passengers in a crash is one of this configurations great pluses. Also
> >in the pre computer age they are easier to pilot than a Flying Wing. As
> >to all the Burnelli conspiracy guff, I don't know if it is valid or just
> >paranoia.
> >>
Twin booms have a number of disadvantages, including the increase in the
number of intersections between bodies (increasing drag), the overall wetted
area of the result, and the fact that they are generally slender, making
them heavier for the same load carrying capacity.
They are generally used when the designer wants to put something 'more
important' right bang where a normal fuselage would go, and often this
results in a much more capable design. They are sometimes used as just an
extension of (twin) engine nacelles, so that the number of external 'bumps'
is reduced (i.e. just continue the nacelle all the way back to the tail).
Good examples of twin boom aeroplanes (done for good reasons) are the P-38,
the Cessna 337, and the Pond Racer.
>
> >>2. V-Tail
> >See the link.
> The problem with the V-tail is structural loads are difficult to
> calculate. It must have taken 30+ years to realize they were wrong in
> the Beechcraft airframes, because the AD to fix it doesn't appear
> until the late 1980's, but goes back to the first production models. A
> number of V-tail aircraft were when for no obvious reason, the tail
> plane came apart. The problem was recognized until someone finally put
> strain gauges back there, and discovered the loads were a lot higher
> then they were supposed to be.
>
I wouldn't necessarily agree with this statement. Problems with Beech
aeroplanes (particularly the Bonanza and the Baron, and not just in the
tail) are not necessarily due to ignorance of the loads, but are often
caused by some rather 'light' structural design.
V-Tails have the advantage of again reducing the number of intersections
(and associated drag) and lowering the total required area for the
controls. On the down side, for manually controlled aeroplanes you must
design a 'mixer' unit that blends pitch and yaw together. Also, a question
arises when both controls are fully deflected... obviously one, the other,
or both has to have reduced effectiveness.
They are often used on UAVs due to the fact that the controls are rarely
fully defelected.
Good examples of V-tail aeroplanes are the Predator and Global Hawk UAV.
> >>
> >>3. Flying Wing
> >I read an article recently (on the net but I confess I didn't keep the
> >thing) that the FW is inherently instable. In those far off days pre
> >computer age the number of controls made them very difficult to handle.
> >Supposedly computerised flight controls could solve this problem making
> >the FW a viable design in the future..
> Inherently unstable aircraft are likely to be the most efficient
> airframes. We make platforms stable by putting drag in the right
> places. Platforms that are unstable don't have enough drag in the
> right places, but drag is clearly the enemy of air frame efficiency.
>
> The Flying wing relied on a Minneapolis Honeywell autopilot to provide
> some semblance of stability in flight, but as a bombing platform, by
> all accounts, the prototype wasn't stable enough.
>
> As you suggest however, fly by wire and computer control make all
> sorts of things possible,such as high alpha low speed passes,
> dramatially forward swept wings, as well as airplanes that don't look
> especially like aircraft, like the F117....
It is a widely held mistruth that flying wings are inherently unstable, and
they can be provided with positive stability. The main stable
ocnfigurations (with no added stability augmentation system required) are:
1) Straight wing with reflexed aerofoil section;
2) Swept back wing with washout;
3) Swept forward win with washin, and;
4) Straight wing with a diffuser tip.
Of course, you can choose to make your flying wing without natural
stability, provided you have a nice, sophisticated, multiply redundant SAS
connected to it.
The advantages of flying wings are that in the cruise they give very low
drag, and a 'blended' shape can often have generous internal space.
The down sides are that they don't generate very high maximum lifts (fitting
of flaps is problematic), the fin and rudder (if any) is difficult to locate
with a reasonable arm, and that the available centre of gravity range is
usually very small.
Good examples of flying wings are the Horton gliders, the Chance-Vought
Cutlass, the B-2, and Scott Winton's Facet Opal (although this aeroplane had
'marginal' stability).
Hope this all helps.
Eric Whitney
townes de wombat
eggzacterly. I believe, (and I'll not be emphatic about this stuff cos I
am not all that expert on such matters), that instability , to a degree,
is great for a fighter as it's very instability makes for enhanced
maneuverability which is good in a fighter but not so wonderful in a
bomber, that needs to be a stable platform. I guess then that too much
stability would ultimately give the thing the handling characteristics
of a brick.
Townes
Stealth Pilot
>What are the cons/pros of (especially their contribution to stability
>factor) :
>
>1. Twin-Boom Fuselage
>
narrow dia booms are poor structurally for the weight. move the
material out from the neutral axis about the distance of a typical
tailcone and it gets more efficient and you only need one boom.
no effect on stability.
>2. V-Tail
>
vtails wallow along. they dont have the crispness of control that a
normal cruciform tail has. the wallow, yawing actually, is enough to
make you seasick. only ever flown in a Davis DA2A to experience this.
the beechcraft bananna was famous for it.
>3. Flying Wing
>
can be made controllable by various tricks like reflexed trailing
edges. the cg position is critical. on some flying plank gliders it
was something like an inch or two from forward to aft cg position.
Stealth Pilot