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Entirely and completely correct, I was speaking in generalities which is a bad thing, Es tut mir leid. the BAR at 100,000 Pa is NOT an accepted SI unit nor is it on the "accepted for use" non-SI units like the common units: Days (d); Minutes (min); Hours (h); the common angle units of Degrees, Minutes of Arc; and Seconds of Arc; for land the Hectare; the original metric Liter/Litre; and the metric Tonne. The SI does however say that while not "accepted" it is OK to use. As a result we hear/see a mix of hectoPascals, kiloPascals; and Bars except for the common weather guys who still report in atmospheric pressure in INCHES leaving out the "OF WHAT" part and many cases even the inches.1 bar does not equal 1 atmosphere. 1 atmosphere is, in fact, 1.01325 bar.
That mixture of units gives you two separate length measurements m and mm^2 in the numerator and denominator respectively. The reason it works and comes out in M (Mega - million) is because 1 meter = 1000 mm and 1 m^2 is 1000mm x 1000mm = 1,000,000 mm^2. For calculations to remain valid with answers in the correct units you need to stay within a particular system, in this case, the MKS system or Meter-Kilogram-Second system of units.mm for length units and N for force units
Ah yes how well I remember LUCAS, Lord of the DarkLucas electrics,
If you really stop and consider it the recurring nature of 12 is really astounding: A ruler has 12 subdivisions. The Romans also divided the foot into 12 divisions and the UNCIA was 1/12th of a Roman pound.. Produce like eggs. donuts, flowers, golf balls, beer, soft drinks ( a case is 24 cans), etc. are sold in dozens and grosses , pharmacists, jewelers, reloaders use the 12 ounce Troy pound as did the British Mint: 1 shillings = 12 pence and 20 shillings = 240 pence or 1 pound sterling. Consider our timing and dating system there are 12 months in the year, and our day is measured in 2 sets of 12 hours. The Babylonians had a 12 hour day. In geometry, a complete circle at 360 degrees is really just subsets of 12, i.e. a 360 degree circle consists of 30 sets of 12. The 12 signs of the zodiac. There were 12 apostles in the bible. You have four fingers with three joints each or a total of 12 jointsAlan Turing made a compelling argument that humans should adopt base 12 number system
And a meter is a mental device used for measuring a linear distance.
And speaking of the confusion of tools needed to work on today's "global" machinery, I remember maintaining a fleet of Netherlands manufactured Fokker F27s of varying vintages with RR Dart engines made from 1947 to 1977, with Dowty props of varying ages, Lucas electrics, Maxaret antiskid, and Goodyear and Dunlop brake assemblies. SAE and metric tools weren't enough. You had to have British Standard and Whitworth as well. Sometimes you would get an older Dart with newer accessories on it and you'd wind up using Whit, BS, and metric all on the same job. Newer combustion cans on an older engine might have "updated" hardware installed...or not.
Cheers,
Wes
Here in Canada, we have an extra confusion point. There is the original Imperial measurement system that was used up to the late 70's when we went metric, after the US proposed the change, but then they didn't. Then there is the US system that is an off-shoot of the Imperial system but with differences. As our major trading partner, almost everything is marked with both systems: grams/ounces ( but not Imperial ounces ); litres/gallons ( again, not Imperial gallons ).
Ain't life a female dog!
Chris
BZZZZT! WRONG!The F-27 was a British aircraft assembled in Holland.
BZZZZT! WRONG!
Designed by Fokker with financial aid from the Netherlands government, built by Fokker, it was British only to the extent of using Dart engines, Dowty props, Lucas electrics, Rootes cabin blowers, and Dunlop wheels and brakes.
I know, I worked with most of that stuff. We had for awhile a very early (1957) one that was still in BEA color scheme and was Brit all the away, even to the COM/NAV radios which we had to rip out because they wouldn't tune the .025 and .075 frequencies. The right engine on that one had a 3 digit serial number with a 1947 manufacture date, a carton full of logbooks, 80,000+ hours of flight time, and 11 different data plates from various Mk numbers that the engine had been modified to over its lifetime. It had been mounted on six different aircraft of five types in that time.And a lot of other British parts - Dowty landing gears, Redux bonding, Smiths Instruments, British cable tensioners, Brit fuel system components, choke heating, Brit oxgen and plumbing, pneumatics instead of hydraulics, etc, and at some operators even Brit radios. And don't forget the bicycle chains that the Brits love so much.
Personally, I use metric when 'scaling up' drawings when scratch-building balsa flying scale models. It's so MUCH easier doing 'metric math' – than fooling with dividing 1/32 inches Into 1/64 inch measurements. Lazy? No., smart!We do and we don't - in otherwords, it depends on where measurements are being applied.
In areas of technical production (military, automotive, etc.), we use metric.
In home building, food packaging, driving distances and speeds, etc., we use the old system
Do you model in 1/72 1/48 1/36 1/24?Personally, I use metric when 'scaling up' drawings when scratch-building balsa flying scale models. It's so MUCH easier doing 'metric math' – than fooling with dividing 1/32 inches Into 1/64 inch measurements. Lazy? No., smart!
It shouldn't be, from a pilot's perspective. All you're looking for is the number on approach. I fly a Tiger Moth in mph, a Nanchang in km/h and any GA aircraft in knots, never had any problem as e.g. approach speed is 60 in the Tiger - 150 in the 'chang.A Friend of mine made, mid '60s, the last course in piston fighters.
They started the flying school, he told me, with Piaggio's, whose instruments were metric.
Then with T-6, whose instruments were Imperial.
Then with Fiat G-59, whose instrument were metric again
and finally with P-51, whose instruments were Imperial...
Really a mess, He told me, so they painted red stripes everywhere indicating dangerous limits...
Only if getting out of one aircraft and into another of the same type with different gauges. Different aircraft already have different figures for critical speeds, so the numbers are different anyway. However, if you get out of a 172 with an MPH ASI, and into another 172 with an ASI in knots, that's when problems occur - some things the same, but not everything.Murphys law says that some poor sod is going to get his kph and mph mixed up and find themselves on the wrong side of fate.
It shouldn't be, from a pilot's perspective. All you're looking for is the number on approach. I fly a Tiger Moth in mph, a Nanchang in km/h and any GA aircraft in knots, never had any problem as e.g. approach speed is 60 in the Tiger - 150 in the 'chang.