Boeing design practice

I was at a supplier to Boeing last week and I was surprised to learn
that Boeing still designs in inches, at least for the mechanical
linkage parts this supplier makes. I think that would not only
significantly handicap them in locating suppliers but also handicap
their customers in locating and maintaining replacement parts.

I was less surprised to learn that the US military specs in inches
also.

Any Boeing engineers on board to confirm or deny this?

easy enough to confirm - but the problem isn't as simple as you might
think - metric dimensioning is one thing (easy enough to convert; 7.62mm =
3.00 inch, etc) but going TRUE metric is another - as a prime example, in
aluminiuum the material gages (thicknesses and strengths) don't directly
correspond to 'inch-pound" (otherwise known as "US Customary") values. this
presents a dimelma in that established databases of "allowables" (thos
values established and backed by YEARS of data collection and experience)
need to be "re-established" (as in "re-done"). This in and of itself isn't
DIFFICULT - "merely" extremely time consuming. Add to that the reluctance
on the part of US aerospace airframers (in general) to accept anything not
in "MIL-HBK-5" (the "approved by everyone" datatbase) - or whatever the
latest designation incarnation is - and the problem cascades. The last
attempt to make a "metric vehicle" is the Space Station - and even that was
dictated by the necessity to have INTERNATIONAL paticipation. Personally, I
would like to see the US aerospace industry "metricated" - the auto industry
did it YEARS ago for competetive reasons. practically, I don't expect it to
happen.

As yet another example - SAE aerospace specs use "inch-pound" as basic with
metric as "soft conversions". Many SAE automotive specs use metric as basic
with "inch pound as either "soft convert" or NON-EXISTANT (metric only - or
you can just go do the conversions yourself - or - what difference does it
make to have pounds in a metric designed spec?)

decrypt my e-mail (for e-mail outside Boeing) and send me a message if you
want more info

"Dick Locke" wrote in message
...
I was at a supplier to Boeing last week and I was surprised to learn
that Boeing still designs in inches, at least for the mechanical
linkage parts this supplier makes. I think that would not only
significantly handicap them in locating suppliers but also handicap
their customers in locating and maintaining replacement parts.

I was less surprised to learn that the US military specs in inches
also.

Any Boeing engineers on board to confirm or deny this?

On Tue, 16 Dec 2003 16:49:01 GMT, "DALing"
daling43[delete]-at-hotmail.com wrote:

easy enough to confirm - but the problem isn't as simple as you might
think - metric dimensioning is one thing (easy enough to convert; 7.62mm =
3.00 inch, etc) but going TRUE metric is another
It's not easy I agree. Tolerances are a special problem. .0005 inches
doesn't convert well.

I would expect, though, that threaded items like nuts and bolts would
be metric so that overseas customers don't have to get common
replacement hardware from the US or Burma (or the UK?).



as a prime example, in
aluminiuum the material gages (thicknesses and strengths) don't directly
correspond to 'inch-pound" (otherwise known as "US Customary") values. this
presents a dimelma in that established databases of "allowables" (thos
values established and backed by YEARS of data collection and experience)
need to be "re-established" (as in "re-done"). This in and of itself isn't
DIFFICULT - "merely" extremely time consuming. Add to that the reluctance
on the part of US aerospace airframers (in general) to accept anything not
in "MIL-HBK-5" (the "approved by everyone" datatbase)

Is that Mil HBK accepted in Europe?

I was told Airbus designs in metric, and I have to believe this gets
them a competitive advantage. Couldn't whatever spec they design to be
accepted here?


- or whatever the
latest designation incarnation is - and the problem cascades. The last
attempt to make a "metric vehicle" is the Space Station - and even that was
dictated by the necessity to have INTERNATIONAL paticipation. Personally, I
would like to see the US aerospace industry "metricated" - the auto industry
did it YEARS ago for competetive reasons. practically, I don't expect it to
happen.

As yet another example - SAE aerospace specs use "inch-pound" as basic with
metric as "soft conversions". Many SAE automotive specs use metric as basic
with "inch pound as either "soft convert" or NON-EXISTANT (metric only - or
you can just go do the conversions yourself - or - what difference does it
make to have pounds in a metric designed spec?)

decrypt my e-mail (for e-mail outside Boeing) and send me a message if you
want more info

How about I fax you on 8-1/2 by 11 paper so you can put it in a
three-hold binder (two more items not readily available outside of
North America....;-)

"Dick Locke" wrote in message
.. .
I was at a supplier to Boeing last week and I was surprised to learn
that Boeing still designs in inches, at least for the mechanical
linkage parts this supplier makes. I think that would not only
significantly handicap them in locating suppliers but also handicap
their customers in locating and maintaining replacement parts.

I was less surprised to learn that the US military specs in inches
also.

Any Boeing engineers on board to confirm or deny this?

Interesting post, I've often wondered when and if altimeters and ATC
instructions will be in metric, I believe Soviet aircraft - at least
military ones use metres rather than feet.

Colin.

--
Remove the 'old' to reply to me.

Watashi no tsuma wa nihon-jin desu!
Watashi no tsuma wa kawaii desu!

"Col" wrote in message
...
Interesting post, I've often wondered when and if altimeters and ATC
instructions will be in metric, I believe Soviet aircraft - at least
military ones use metres rather than feet.

I think this is mostly the good ol' installed-base probem.
Altimeters and such tend to be fairly long-lived pieces of
equipment - and how do you make a transition such as this
without forcing everyone, as of date X, to upgrade to the
new system or leave their planes on the ground?

Why do you think aviation still uses Antique Modulation
for all the comms?


Bob M.

Another good point Bob (AM), it was brought up in a documentary I saw about
a year ago, some pilots interviewed mentioned that they would prefer a
system whereby both pilot and tower could talk/listen at the same time.

Colin.

--
Remove the 'old' to reply to me.

Watashi no tsuma wa nihon-jin desu!
Watashi no tsuma wa kawaii desu!

Dick Locke wrote in message . ..
I was at a supplier to Boeing last week and I was surprised to learn
that Boeing still designs in inches, at least for the mechanical
linkage parts this supplier makes. I think that would not only
significantly handicap them in locating suppliers but also handicap
their customers in locating and maintaining replacement parts.

I was less surprised to learn that the US military specs in inches
also.

Any Boeing engineers on board to confirm or deny this?

Why is it a surprise? I am not in the aerospace industry but in
engineering nonetheless. What will force the US industries to adopt
metric? Only the market will. So far that has not happened.

Born and educated in the Orient, I was familiar with the SI system.
But having lived in the US for so long, I've already lost the feel for
the SI unit. For example, I know one lb of weight far better than one
newton. Similarly I have much better feel for one BTU than one KCal,
HP for Joule and so on. But does that mean when the market forces
change I will be doomed? I don't think so. Human are animal of habit
and we all have far greater ability to adopt than given credit for.
If and when the US industries are in no position to dominate in a
manner that switching to metric becomes necessary, they will do it in
order to survive. I wouldn't worry too much about it.

I have regained some feel for the SI length measurement since all my
cars are imports.

Boeing's modern cockpits contain a ft/meter switch so that the proper
altitude units will be displayed while in Russian or Red Chinese
airspace.

Mike Lechnar

Col wrote:

Interesting post, I've often wondered when and if altimeters and ATC
instructions will be in metric, I believe Soviet aircraft - at least
military ones use metres rather than feet.

Colin.

--
Remove the 'old' to reply to me.

Watashi no tsuma wa nihon-jin desu!
Watashi no tsuma wa kawaii desu!

Dick Locke wrote in message . ..
I was at a supplier to Boeing last week and I was surprised to learn
that Boeing still designs in inches, at least for the mechanical
linkage parts this supplier makes. I think that would not only
significantly handicap them in locating suppliers but also handicap
their customers in locating and maintaining replacement parts.

I was less surprised to learn that the US military specs in inches
also.

Any Boeing engineers on board to confirm or deny this?

Not Boeing, but one of their direct competitors.

The vast majority of the military aerospace industry still works
in the US system of inches and lbs. It is predominately because
the vast majority of the mechanical specs are still denominated in
those units. Mil-HDBK-5 which is the bible of aerospace structural
materials is all in those units. The reality is that we have
trouble getting metric unit based hardware. I was working with
some germans who had spec'ed a set of fairly common metric thread
fasteners. When I tried to get a dozen of them on our own,
we couldn't find a supplier. Oh, they'd MAKE us a set and have
'em to us in 6-8 weeks, but none on the shelf.

Sheet metal is still largely sold in gages based upon inches.
Structural materials are still sold by the pound. Standard
machine tools such as drill bits etc. are still all defined in inches.
The auto industry has largely converted, but there are still many
industries which work in US/imperial units. There is just little
incentive to convert. The US is a big market and the heavy industries
just don't export as much as others.

NASA has tried to force the issue for decades, but since they
were but a small slice of the larger government contracting industry,
we mostly just worked in inches and lbs and then converted the
documentation upon delivery. Truth is, it is no more complicated
than any other system. The trick of course, with any system, is
to stick to it. It is in the conversion that the errors creep in.

Dick Locke wrote in message . ..
I was at a supplier to Boeing last week and I was surprised to learn
that Boeing still designs in inches, at least for the mechanical
linkage parts this supplier makes. I think that would not only
significantly handicap them in locating suppliers but also handicap
their customers in locating and maintaining replacement parts.

I was less surprised to learn that the US military specs in inches
also.

Any Boeing engineers on board to confirm or deny this?

Not a Boeing engineer, but work in computer systems engineering
involving lots of suppliers and subcontractors.

If the supplier can't figure out the units of measure and convert them
from one system to another, I wouldn't want them for a supplier.
Fasterners, threads, etc are not a problem to obtain in either system
(metric/imperial-english). And, since so many are custom
manufactured, it really matters little what system of measure is used.