Agreed, but are all the subcontractors in this "international build-off" used to building in imperial units? :hmm:

it's mixing systems that causes issues

Aye .. the laddie speaks the truth ... I guess all engineers agonised for a term or so during their first undergraduate year coming to grips with 438,972 different systems of units of measure ..

.. mind you ... I was about 35 before I encountered the cheval (and had not the slightest idea what it was) .. I still am greatly confused as to why it isn't closer to the HP (at least, for those for whom size is important .. the English HP is bigger than the French) and as to 75kg.m/s, well that just about confuses me beyond comprehension ....

... then again, the Canadian French use CV for the English, rather than the French HP ... I think now .. I should just admit defeat ... give up and go to bed ..

The key thing is that everyone uses the same one.

Of course that is the answer to MFS' concern ... apologies if my imperfect attempt at humour caused me to be taken seriously .... I am rarely serious ..

are all the subcontractors in this "international build-off" used to building in imperial units

.. ah .. therein lies the empire whose name is QA ...

In Australia they regularly sell land in "perches" and size houses in "squares" - the salesperson could not tell me what a "square" was - well it is 100 square feet. Cannot recall what a perch is.

Feels a bit Dickensian.

And next, the cubic fortnight....???

As a linear measure, a perch (also rod, or pole) is 1/4 of a chain, which is 22 yards (cricket pitch length). A perch is therefore 22/4=5.5 yards or 16.5 feet.

As an acre is an area one chain by one furlong, I'd take a guess that as a unit of land, a perch might be 1/4 of an acre i.e. 1 perch by one furlong.

edit: just wikipediaed it, and a perch as a unit of area actually an area one rod by one rod (or indeed, one perch by one perch) so there are 160 perches to the acre. Another useful fact learned. I think we'll use perches for our next wing area non-dimensionalisation.

Metric fasteners in the US cost significantly more than their inch sized counterparts. Same materials, the tooling exists, the price is higher.

I've not found an anti-roll bar on any car from Europe, NA, or Asia that is manufactured to a metric size. Yet all of them specify the size in millimeters...gotta love the 25.4 millimeter bar.
Past first year, still find it outrageous and annoying.

The PS/SAE HP/DIN HP/CV/whatever stuff is not my idea of fun. Oddly enough, I haven't yet found the watt that isn't a watt. Am I not looking hard enough?

This idea that the units don't matter so long as the system is consistently applied also seems a bit weak to me. It is very easy for me to remember how the watt is defined. Its easy for me to relate it to units like the volt and ampere. It is considerably less easy and less accurate for me to do such mental gymnastics with whatever system of units. It would appear to me that the SI system and the technical units related to it are just plain better than the alternatives.

In any case, even if one doesn't care to admit that one system is inherently better than another, surely its obvious that multiple systems in use will cost lots of cash and time in order to avoid safety and quality problems.

Some thoughts ..

(a) all nonsense aside, life would be very much easier, and the system much safer, if we had ONE set of consistent, easily defined/derived units .. even if that would defeat the joys of in-house jargon etc ... and, of course, it doesn't matter an iota what ethnic origins such a system might have ...

(b) with mixed units, the PE folk are reasonably well off .. having been tortured in the initial undergraduate environment we all are quite comfortable with a rigorous application of units and unit to unit conversions ... however, for everyone else in the Industry, it is a recipe for disaster .. as shown by several well publicised events .. Gimli, for one.


Thread creep ... I've totally forgotten what the thread topic was ... a most wonderful aspect to PPRuNe is thread diversion and thread creep ... one picks up some gems of information along the way ...

Metric V Imperial
I have a memory of a Mars landing craft that hit the mars surface at mach 3 because 1 part of the team were working in meters and the other feet and the calculations didn't mix :ok:

here is the link http://en.wikipedia.org/wiki/Mars_Climate_Orbiter

Sorry for bringing the thread backto Earth with a bump but I'd love to know how Boeing are going to fix that little feature! Is it a hoax? Or have they got another one in build nearing completion?

Getting back to the main subject of this thread, this quote appears to come from someone close to the project, and can be found at this link, under the COMMENTS section:

http://www.thedigitalaviator.com/blog/?p=402

"I’ve heard the misalignment was caused by one of the fixtures used to hold the section, and not by the section itself, apparently it was causing a distortion and thereby the misalignment. Adjustments to the fixture resolved the problem and everything lined up. I believe the other problem is a fastener shortage and they have people running around like mad devils rounding up alternate suppliers. As you stated problems crop up as they progress, but nothing of a major concern. I have my invitation along with thousands of others, so I would assume the roll out on 7/8/7 will proceed as planned."

Seems to be sorted!

There was a link to a 'seattle times' article on flights website a few days ago in an article ref using the KC767 for the rollout rehearsal. In the article there was a lot more info , also a very serious witch hunt to find the employee who had posted the pics !!!!

AWG and AF both alive and well on the A380

On the subject of units - I am a PPL but like to keep a "watching" brief on the commercial forums (fora?).

Is it just history that the units in aviation are such a mix? as examples:
Altimeter settings in hectopascals (aka millibars) or inches of Hg
Altitude (in most place) in feet
Runway lengths in feet or metres
Distances in nautical miles

On light aircraft I have flown I have come acoss the following mixes of units :-
Fuel capacity in US gallons, litres, imperial gallons, kilos or pounds
Weight & balance in lbs and inch pounds, kilos and kilo cms
Air speeds in Knots, mph or Km/hour
Tyre pressures in lb/sq in or bar
Oil capacities in litres, US quarts, imperial pints
Boost in inches (of Hg?)

I know that a lot of these are "inherited" from the country of manufacture of the aircraft , but for safety and ease of use I have always been surprised that there is no standardisation.

It is just too easy to cock up a weight & balance calculation because of mixed units.

as examples:

.. ah ... music to an old engineer's ears ..... just like grandma's kitchen recipes .. a bit of this ... a bit of that ...

I guess that, eventually, we will find ourselves driven to a sensible metric system for all the sensible reasons which accrue ...

Why are they different, Choxolate?

Envy...and as a result, others have to be different.

Why envy?

Simply because, where aviation (in general) is concerned, the USA (and not to forget the UK in many areas) have more or less dominated the world for many many years in design and manufacture of aircraft, and others, are just so darn pi**ed off about this, that they just have to be 'different'.
Especially the 'metric' crowd, and those that follow it.:rolleyes:

The 'mass' (instead of 'weight') folks, or 'inches/feet is outdated' crowd will never be satisfied, and that is truly their collective problem...pure unadulterated envy, and their burden.

I really do have to laugh about this whole affair.

Blame the French - it usually works !! :ok:

That would be pretty much everyone, except USA, Burma, Liberia, and a few others, according to Wikipedia... :hmm:

Hence forth, all references to speed, be it in relation to aviation or not, should be made in furlongs per fortnight (fpf).

http://en.wikipedia.org/wiki/Fortnight

and also

http://en.wikipedia.org/wiki/List_of...of_measurement

for a bit of a laugh.

I have my invitation along with thousands of others, so I would assume the roll out on 7/8/7 will proceed as planned.

And while we're on the subject of multiple standards, will you be attending on 7th August or 8th July?

That is very very good! I like. :D:D

Again - getting back to the thread.....

So Boeing says it's the tooling eh? What is it they say about a 'bad' engineer always blaming his tools? :}