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Burt Rutan’s Boomerang – Safety Through Asymmetry

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Re: Burt Rutan’s Boomerang – Safety Through Asymmetry

#11

Post by andrewcooke »

kwantam wrote: post #7
andrewcooke wrote: post #3

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...

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…

you know, there is a difference between "largely" and "only".

Re: Burt Rutan’s Boomerang – Safety Through Asymmetry

#12

Post by 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.

Re: Burt Rutan’s Boomerang – Safety Through Asymmetry

#13

Post by spitfire »

mgns wrote: post #10
wickedchicken wrote: post #2

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 mathem…

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.

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.

Re: Burt Rutan’s Boomerang – Safety Through Asymmetry

#14

Post by joe_bleau »

kwantam wrote: post #7
andrewcooke wrote: post #3

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...

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…

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.

Re: Burt Rutan’s Boomerang – Safety Through Asymmetry

#15

Post by gvb »

joe_bleau wrote: post #14
kwantam wrote: post #7

Earlier quoted context omitted.

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…

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.

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).

Re: Burt Rutan’s Boomerang – Safety Through Asymmetry

#16

Post by [deleted] »

biot wrote: post #5
sambeau wrote: post #4

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?

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.

[deleted]

Re: Burt Rutan’s Boomerang – Safety Through Asymmetry

#17

Post by bfe »

mgns wrote: post #10
wickedchicken wrote: post #2

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 mathem…

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.

Yes, every modern fighter jet is engineered to be aerodynamically unstable and requiring intensive computer control just to be able to fly. It's part of the special sauce that lets them perform so deliriously ridiculously, and part of why the F-35 is the last human-piloted fighter jet. It's been beyond ludicrous for a long time now to maintain the assumption that a human pilot should be physically inside that thing.

Re: Burt Rutan’s Boomerang – Safety Through Asymmetry

#20

Post by teamonkey »

gvb wrote: post #15
joe_bleau wrote: post #14

Earlier quoted context omitted.

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.

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).

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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