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#1
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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? |
#2
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Boeing design practice
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? |
#3
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Boeing design practice
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? |
#4
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Boeing design practice
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! |
#5
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Boeing design practice
"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. |
#6
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Boeing design practice
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! |
#7
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Boeing design practice
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. |
#8
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Boeing design practice
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! |
#9
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Boeing design practice
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. |
#10
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Boeing design practice
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. |
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