
Burt Rutan’s Boomerang – Safety Through Asymmetry - inetsee
http://www.wired.com/autopia/2011/07/burt-rutans-boomerang-safety-through-asymmetry
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wickedchicken
Reminds me of the beautiful control theory concept of relaxed stability
(<http://en.wikipedia.org/wiki/Relaxed_stability>). You intentionally craft
instability in the system and use a controller to manipulate and exploit it,
seemingly gaining extra performance for little cost. Unfortunately this
doesn't even begin to scratch the surface of control theory but it's a neat
introduction to an interesting branch of mathematics/engineering most CS
people aren't aware of.

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mgns
I believe that's how modern fighter jets are designed, for exmaple JAS 39
Gripen <http://en.wikipedia.org/wiki/JAS_39_Gripen>

They deliberately make them unstable and can then utilize that to make turns
that are sharper than otherwise possible. The drawback is that they have to be
controlled by computers all the time. This led to a spectacular crash in
Stockholm in 1993 where luckily nobody was hurt.

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spitfire
The goal isn't actually to make the turns sharper. But to make the rolls
quicker.

If you can change between maneuvers faster than your adversary you can cause
him to be confused, giving you the advantage. This all comes from energy
maneuverability theory which is the theory that modern fighters are based on.

Build planes capable of fast transients and a natural buttonhook tendency.

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michaelw
I've been a fan of Burt Rutan since the VariEze first appeared on the cover of
Popular Science in 1974. Oh how I wanted to build one of those planes. Burt
Rutan has made more contributions to aerospace than anyone since Glenn
Curtiss.

This wikipedia article is certainly relevant
<http://en.wikipedia.org/wiki/Critical_engine> but I'm still not sure how the
Boomerang can be so stable that it requires no rudder input during takeoff.

My guess is that by having one engine further back he creates the equivalent
of the dihedral effect. If the plane starts to yaw in one direction. I have
nothing but intuition to support this idea :)

I would love to see a detailed explanation of how this plane is so stable.

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sambeau
Another beautiful piece of non-obvious design.

I instinctively look for symmetry in my designs (and my purchases too I
suspect).

I wonder if the reason it never 'took off' commercially was that people
instinctively disliked the lack of symmetry?

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biot
It seems like it didn't take off commercially because it was just never
pursued:

    
    
      > Like many of Rutan’s creative designs, the Boomerang never went
      > into production. There was never even a second example built.

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VladRussian
his another asymmetric <http://stargazer2006.online.fr/aircraft/ares.htm>

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ZoFreX
> Clements says the rudder pedals are rarely touched during flight, something
> unheard of for most pilots, especially those who fly small twin engine
> airplanes.

Is this really that unusual? In the Bulldog (which is very small and single-
engined) you can get away with not using the rudder at all during normal
flight.

Edit: Asked a friend who knows these things, it's not that unusual for a twin
engine to not need a lot of rudder, but also not a rule either.

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bfe
Best quote from this story, and how is it interpreted by different software
makers: "You’re just going to screw something up. Best thing is to take your
feet off the pedals and let it fly."

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bfe
I can't get over how fascinating this thing is. Makes the "gristleships" in
Alastair Reynolds's "Pushing Ice" all the more believable.

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andrewcooke
i think this must be more stable largely because the two engines are closer
together (effectively one "side boom" is moved to the centre).

couldn't you do even better with a push-me pull-me configuration? then power
would always be aligned correctly, whatever failed. perhaps that is less
efficient, since the pusher is in the wake of the puller? it wouldn't look so
fugly...

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kwantam
I'm pretty sure there's more to it than just that. For example, the difference
in power output between the two engines wouldn't be necessary if the enhanced
stability were due only to reduced distance between engines.

For example, the Blohm and Voss BV141, an experimental German aircraft, used
an asymmetric single engine design wherein the weight asymmetry was balanced
by the prop torque, which tends to cause yaw and generally needs to be trimmed
out on non-counter-rotating twins and single engine airplanes. [0]

With regard to push-pull config: the Cessna Skymaster was designed this way.
There are about 3000 of them flying around, including about 500 in military
service, according to Wikipedia [1].

Another amazing aircraft design that never caught on and had some of the
enhanced stability properties inherent in closer engine placement was the
Beechcraft Starship [2]. For my money, it's the most beautiful business
aircraft ever built, and it's got some seriously amazing aerodynamic features.
For example, since it uses a canard design, it's very hard to stall: the
canards will stall before the wings, which drops the nose, decreasing AoA and
increasing lift.

There's an amazing image of a Starship chasing a SpaceShipOne during a test
flight on the Wikipedia page.

[0] <http://en.wikipedia.org/wiki/Blohm_%26_Voss_BV_141>

[1] <http://en.wikipedia.org/wiki/Cessna_Skymaster>

[2] <http://en.wikipedia.org/wiki/Beechcraft_Starship>

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joe_bleau
One of the Starships was based at our local airport for a few years. Very
impressive looking aircraft. As I recall, it was a strange sounding beast;
much noisier than you'd expect. Haven't seen it around in quite some time,
though.

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gvb
See also the Piaggio Avanti. <http://www.piaggioaero.com/> One use to land at
the airport near me (I have not seen it in a while). It also had a very
distinctive sound (and was quite noisy).

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teamonkey
I first found out about the Piaggio Avanti when I downloaded X-Plane 9 for the
iPhone. The whole body creates lift and as a result it handles very
differently from other small aircraft.

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rdl
This is the kind of mechanical device where I could support patents,
especially for a ~5-10 year span.

