On Wed, 5 Jan 2005 12:03:37 -0800, "Joel Kolstad"
wrote:

"Ed Price" wrote in message
news:gAdBd.6143$yW5.2@fed1read02...
We spend a lot of time now arguing about how well the computer model
replicates reality, and whether the math has enough variables accounted
for. Working models seem so old fashioned.

That's because they're so expensive to build. You'd probably never finish
designing something like a modern RF IC if all you could do was design it on
paper, build it, probe around a little to figure out what it 'really' does,
and repeat.

Likewise, few companies can afford to design the autopilot for a jet without
a great deal of simulation first. :-)


Hi Guys,

Back when I designed the UFDR for the 757/767, they were the first
airplanes designed entirely in software (conventional drafting went
the way of the Dodo). Today's 7E7 was entirely modeled in software if
I'm not mistaken.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Wed, 5 Jan 2005 12:03:37 -0800, "Joel Kolstad"
wrote:

"Ed Price" wrote in message
news:gAdBd.6143$yW5.2@fed1read02...
We spend a lot of time now arguing about how well the computer model
replicates reality, and whether the math has enough variables accounted
for. Working models seem so old fashioned.

That's because they're so expensive to build. You'd probably never finish
designing something like a modern RF IC if all you could do was design it
on
paper, build it, probe around a little to figure out what it 'really'
does,
and repeat.

Likewise, few companies can afford to design the autopilot for a jet
without
a great deal of simulation first. :-)


Hi Guys,

Back when I designed the UFDR for the 757/767, they were the first
airplanes designed entirely in software (conventional drafting went
the way of the Dodo). Today's 7E7 was entirely modeled in software if
I'm not mistaken.

73's
Richard Clark, KB7QHC


There's nothing wrong with doing a lot of modeling. OTOH, Boeing didn't go
from the computer model directly to production. Computer models don't do
very well in predicting the unexpected; things like digital designers
discovering the concept of parasitics ("There's nothing in my design that
generates 832 MHz!") or mechanical designers exploring the wonders of RF
stray coupling paths ("The RF gets from this compartment to that compartment
through a BOLT?!"

My initial point was that wondrous and amazing things can be proven through
software being pushed to the outer edges of its parameters. Before you
invest in several years of modeling, someone needs to take a whack at a
brassboard model to calibrate the sanity of the software.

Ed
wb6wsn

On Thu, 6 Jan 2005 04:21:19 -0800, "Ed Price" wrote:

OTOH, Boeing didn't go from the computer model directly to production.

Hi Ed,

That is arguably the goal if not the actual reality:

"As computers have become faster and more powerful in recent years,
we have been able to do a better job in modeling the entire airplane and
predicting the three-dimensional effects of the airflow around it,"
Cogan said. "The codes we have developed allow us to look at more
potential design options faster than ever before."

Indeed, Cogan said the process for developing airplanes today begins
with the computer model. The coding is so accurate that designers can
evaluate miniscule changes in a design to determine impacts on
aerodynamic efficiency, he added.

In fact, the accuracy of the coding has also focused the application of
another aerodynamics tool: wind tunnel testing.

In the '80s, the Boeing 767 team took more than 50 wing designs into
the wind tunnel to verify their designs, Cogan said. In the '90s, the
Boeing 777 team took 18 designs into the tunnel. "We were really not
verifying the designs as much as we were verifying that our computation
tools were accurate and looking at performance at the extreme operating
conditions, which the coding couldn't do," Cogan said.

"With the 7E7, we will take fewer than 12 wings into the tunnel," Cogan said.
"We are still proving our coding and testing the extremes.
The tunnel is a great tool but it's not very cost-effective.
So, being able to really focus on a few designs to get the data we need
is helping us be more cost-effective."

73's from Jet City,
Richard Clark, KB7QHC