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DocLightning
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Use Of Metric System In Aviation

Sun Apr 27, 2008 5:40 pm

So why are airspeeds given in kts? Why are altitudes given in hundreds of feet?

Wouldn't it make sense for the international aviation community to switch to Metric?

Wasn't the whole Gimli Glider incident an issue of Imperial vs. Metric?
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Acey559
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Use Of Metric System In Aviation

Sun Apr 27, 2008 5:51 pm

They do use metric in some parts of the world so most new airplanes are able to switch between feet and meters by the flick of a switch. Other planes have conversion charts. Otherwise, I don't know why some parts of the world use it and others don't.
 
f.pier
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Use Of Metric System In Aviation

Sun Apr 27, 2008 6:06 pm

All of us should use the metric international system, so we'd reduce mistakes.
Is it so hard to do?
 
MQTmxguy
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Use Of Metric System In Aviation

Sun Apr 27, 2008 6:09 pm

The way I understand it, back when the powers that be (ICAO?) were setting these global standards it was just a way of compromising between the various systems.
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Leskova
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Use Of Metric System In Aviation

Sun Apr 27, 2008 6:23 pm



Quoting F.pier (Reply 2):
All of us should use the metric international system, so we'd reduce mistakes.

We'd be able to reduce mistakes as well if everyone would use the imperial system... doesn't really matter whether the metric system is used or not - what does matter is that it's standardized.

Quoting F.pier (Reply 2):
Is it so hard to do?

Less a question of being hard or not - more a question of willingness...
Smile - it confuses people!
 
David L
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Use Of Metric System In Aviation

Sun Apr 27, 2008 6:32 pm

Yes, the metric system is tidier but half the aviation world changing from one system to another could be a problem. Aviation had nautical influences in its origins, hence the knots, nautical miles and feet. I guess the USA being so influential in western aviation, and therefore the UK, indirectly, has to take some of the blame.

Quoting DocLightning (Thread starter):
Wasn't the whole Gimli Glider incident an issue of Imperial vs. Metric?

It was an issue of converting from one system to another - it was just as likely to happen converting in the opposite direction.
 
Cubsrule
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Use Of Metric System In Aviation

Sun Apr 27, 2008 6:39 pm



Quoting F.pier (Reply 2):
All of us should use the metric international system, so we'd reduce mistakes.

How many mistakes has imperial vs. metric caused? And couldn't the carelessness that causes that sort of mistakes just as easily cause a dozen others even if we had a standardised system?
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DfwRevolution
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Use Of Metric System In Aviation

Sun Apr 27, 2008 6:47 pm

Quoting DocLightning (Thread starter):
Wasn't the whole Gimli Glider incident an issue of Imperial vs. Metric?

First, there were about two dozen mistakes that led to the incident. Not the least of which was confusion about the MEL for a 767-200.

Second, the mistake that led to the aircraft being loading with pounds of fuel versus kilograms of fuel took place while AC was in the process of switching their procedures over to metric. Certainly the switch to metric itself created the opportunity for an erroneous conversion factor to be used in the calculation.

Leskova is absolutely right IMO. The likelihood of unit errors is highest when working between different types of units. That's why standardization is important and aviation decided a long time ago to make imperial units the standard. I see no compelling reason to change, and history shows that making a switch would leave us more prone to incident.

[Edited 2008-04-27 11:48:10]
 
TGV
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Use Of Metric System In Aviation

Sun Apr 27, 2008 7:03 pm



Quoting DfwRevolution (Reply 7):
and aviation decided a long time ago to make imperial units the standard

Is it the case all around the world :

Quoting Acey559 (Reply 1):
They do use metric in some parts of the world so most new airplanes are able to switch between feet and meters by the flick of a switch.

Like Acey559 I though some parts of the world (Russia for example) were using the metric system in aviation.
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MQTmxguy
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Use Of Metric System In Aviation

Sun Apr 27, 2008 7:08 pm



Quoting DfwRevolution (Reply 7):
That's why standardization is important and aviation decided a long time ago to make imperial units the standard

Except that temperature is almost always in Celsius, weird how that one snuck through.
Well at least we can all take comfort in the fact that NW will never retire their DC-9s
 
DfwRevolution
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RE: Metric

Sun Apr 27, 2008 7:28 pm



Quoting TGV (Reply 8):
Like Acey559 I though some parts of the world (Russia for example) were using the metric system in aviation.

They do, but that's why they are called non-standard.
 
L-188
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RE: Metric

Sun Apr 27, 2008 7:28 pm

The answer is to go back to standard measures such as feet, inches and knots.

The metric system is a completely arbitrary system of measures and doesn't make sense. in fact the meter doesn't even equal up to what it is supposed to because they made a mistake in the distance between the poles when they figure it out. They just looked at the distance to the pole and split it up by a million. No science behind that at all.

The knot however is based on the circle and that makes sense since we live on a big sphere.

Just a bit of education about the knot. From my copy of "Navigation and Nautical Astronomy" but Dutton

The Nautical Mile(Sea mile) is a measure of distance, equalling 6080.27. Ths value was chosen because it is practically the length of one minute of arc of a meridian, or of one minute of arc of the equator.

That defintion made sense in 1942 when my copy was published and still does today.

There are 360 lines of latitute on the earth, which is oddly enough shaped as a 360 degree arc or circle if you prefer. Each of those lines is split up into 60 minutes of longiture which are 6080.27 feet long....on knot...how about that?
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TGV
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RE: Use Of Metric System In Aviation

Sun Apr 27, 2008 8:10 pm



Quoting L-188 (Reply 11):
The metric system is a completely arbitrary system of measures and doesn't make sense. in fact the meter doesn't even equal up to what it is supposed to because they made a mistake in the distance between the poles when they figure it out. They just looked at the distance to the pole and split it up by a million. No science behind that at all.

In reality the meter was based on the earth circumference divided by 40 000 000.

Quoting L-188 (Reply 11):
The knot however is based on the circle and that makes sense since we live on a big sphere.



Quoting L-188 (Reply 11):
There are 360 lines of latitute on the earth, which is oddly enough shaped as a 360 degree arc or circle if you prefer. Each of those lines is split up into 60 minutes of longiture which are 6080.27 feet long....on knot...how about that?

Well I don't see much difference in a system that has a unit (the meter) based on 1/40 000 000 of the earth circumference, and a system based on a unit (the nautical mile) which is 1/ 21 600 of the earth circumference.

As said above there is an arbitrary part here. But what I find far easier in the metric system is the relationship based on base 10 between the units, while having ratios of 12 between inch and foot, then 6080.27 between foot and nm does not make any sense to me.
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kalvado
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RE: Use Of Metric System In Aviation

Sun Apr 27, 2008 8:29 pm

I believe it's more about traditions, like flying, most of sea navigation is done in imperial, as far as I know.
As of right now, I believe there are 3 countries are still officially using Imperial, US, Burma, and I don't remember the third one.
Even without metric, there is enough mess in imperial system - just think nautical mile vs statue mile.

Moreover, there is no such thing as independent imperial system any more. All precision metrology is done in metric, and by now all imperial units are officially defined through metric: international foot is defined as 0.3048 meter, nautical mile is 1852 m, statue mile is 1609.344 and so on; it's not an approximation - it's the legal definition of imperial units.
 
flyb
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RE: Use Of Metric System In Aviation

Sun Apr 27, 2008 8:31 pm



Quoting L-188 (Reply 11):
The answer is to go back to standard measures such as feet, inches and knots.

The metric system is a completely arbitrary system of measures and doesn't make sense. in fact the meter doesn't even equal up to what it is supposed to because they made a mistake in the distance between the poles when they figure it out. They just looked at the distance to the pole and split it up by a million. No science behind that at all.

And the English way makes sense? It is a hard arguement to say that Metric is not a good standard, especially when you compare it to the English standard. Yikes! Glad that I didn't learn ft and pounds, but rather metres and kilos since that makes 1000X more sense.
 
Cubsrule
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RE: Use Of Metric System In Aviation

Sun Apr 27, 2008 8:42 pm



Quoting Flyb (Reply 14):
Yikes! Glad that I didn't learn ft and pounds, but rather metres and kilos since that makes 1000X more sense.

I can definitely get around both systems (I have a science degree and have lived in metric countries), and I've concluded that the ONLY factor that determines which system "makes more sense" is the system you grew up with.
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sccutler
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RE: Use Of Metric System In Aviation

Sun Apr 27, 2008 8:48 pm

There is no useful reason why the USofA has not changed to the metric system- when I was a kid in elementary school in 1965, we were taught the metric system, and were told that we'd be fully-converted by 1970. They got as far as putting up dual-unit signs on highways, etc., then for political reasons, the process faded.

And yet...

... most manufacturing in the US has, in fact, gone metric, for reasons of global competitiveness.

As for aviation, notwithstanding the foregoing, since nearly all aircraft are certified with performance tables, etc., in knots (and the nautical mile is not a ridiculous and dimensionless measure), there are compelling reasons of safety to retain them, and no compelling reason to change.
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FriendlySkies
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RE: Use Of Metric System In Aviation

Sun Apr 27, 2008 9:07 pm



Quoting SCCutler (Reply 16):
There is no useful reason why the USofA has not changed to the metric system- when I was a kid in elementary school in 1965, we were taught the metric system, and were told that we'd be fully-converted by 1970. They got as far as putting up dual-unit signs on highways, etc., then for political reasons, the process faded.

I thought a lot of it had to do simply with the cost of converting the entire US infrastructure to metric.
 
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GrahamHill
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RE: Use Of Metric System In Aviation

Sun Apr 27, 2008 9:29 pm



Quoting Cubsrule (Reply 15):
I can definitely get around both systems (I have a science degree and have lived in metric countries), and I've concluded that the ONLY factor that determines which system "makes more sense" is the system you grew up with.

Spot on!
"A learned fool is more foolish than an ignorant one" - Moliere
 
tdscanuck
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RE: Use Of Metric System In Aviation

Sun Apr 27, 2008 9:43 pm



Quoting DocLightning (Thread starter):
So why are airspeeds given in kts?

Nautical heritage of aviation.

Quoting DocLightning (Thread starter):
Why are altitudes given in hundreds of feet?

US & English dominance of early air travel.

Quoting DocLightning (Thread starter):

Wouldn't it make sense for the international aviation community to switch to Metric?

If you could convert everyone without any pain yes. But getting there from here is more trouble that it's worth.

Quoting F.pier (Reply 2):
All of us should use the metric international system, so we'd reduce mistakes.
Is it so hard to do?

Yes, it's that hard to do. There is an absolutely staggering amount of documentation, maps, plans, tooling, and design done in knots/feet/pounds.

Quoting L-188 (Reply 11):
The metric system is a completely arbitrary system of measures and doesn't make sense.

Arbitrary? Once cubic meter of water = 1 tonne. Almost everything else falls out of that. All conversions are 10 or 1. It's far less arbitrary than any other system of measurement.

Tom.
 
Ned Kelly
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RE: Use Of Metric System In Aviation

Sun Apr 27, 2008 10:03 pm

I always hate it when aviation TV programs like Air Crash Investigator quote altitudes in metric when most aircraft fly at altitudes in feet! Which prompts me to my question regarding Russia, do pilots in Russia for example fly at 10,000 metres instead of 30,000 feet, or do the fly at the metric equivalent of 30,000 feet which is 9144 metres? Can anyone answer this?
 
JayDub
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RE: Use Of Metric System In Aviation

Sun Apr 27, 2008 10:05 pm



Quoting Cubsrule (Reply 15):
I can definitely get around both systems (I have a science degree and have lived in metric countries), and I've concluded that the ONLY factor that determines which system "makes more sense" is the system you grew up with.

Ding, ding, ding...we have a winner.

They are both acceptable...and the same arguments for which system is "better" can be made on either side of the fence.
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gooner
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RE: Use Of Metric System In Aviation

Sun Apr 27, 2008 10:12 pm

I was bought up as a child with the imperial system but as i got older the metric system became nore prevelant.When i started my apprenticeship in engineering in 1975 it was unbelievable how many types of screw threads etc were used.I for one would use the metric system anytime.How many others on here remember £ s d before decimilisation.What a stupid way to have your money
 
Mir
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RE: Use Of Metric System In Aviation

Sun Apr 27, 2008 10:35 pm



Quoting L-188 (Reply 11):
The metric system is a completely arbitrary system of measures and doesn't make sense.

The length of a meter may be arbitrary, but the way the system works (base 10) is certainly not. It makes far more sense than does the imperial system.

Quoting Ned Kelly (Reply 20):
Which prompts me to my question regarding Russia, do pilots in Russia for example fly at 10,000 metres instead of 30,000 feet, or do the fly at the metric equivalent of 30,000 feet which is 9144 metres? Can anyone answer this?

When airplanes fly at metric altitudes, they separate by 300 meters. I can't say whether they would fly at 10,000 meters or not, but it would be a round (to the hundreds place) altitude like 9,700 meters or soemthing like that. They don't just convert every altitude level to exact meters and fly it.

Which leads to another reason for the imperial system to be used in altitude - 1,000 feet is a pretty good separation distance. 300 meters is good too, but in this rare case it's much easier to use the imperial system.

-Mir
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Zkpilot
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RE: Use Of Metric System In Aviation

Sun Apr 27, 2008 11:26 pm



Quoting DocLightning (Thread starter):
So why are airspeeds given in kts? Why are altitudes given in hundreds of feet?

Wouldn't it make sense for the international aviation community to switch to Metric?

Wasn't the whole Gimli Glider incident an issue of Imperial vs. Metric?

Kts are not imperial either... they are based upon nautical miles (which are completely different from imperial miles). Nautical miles are based on degrees of arc (of the earth).
The reason why aviation generally uses imperial measurements such as feet is that the USA and the UK were the 2 major powers that be in the initial development of aviation and in the USAs case it has continued this. Events like WWII where the USA produced huge numbers of aircraft for itself and allies of course entrenched that standard. If Germany had won the war then most certainly the world would all be using metric (one of the few things that they did right). As the USAs power and influence internationally is on the wane (China and India are on the rise), expect to see more pressure for the USA to change to metric... like Canada and almost the entire rest of the world.

Quoting Ned Kelly (Reply 20):
I always hate it when aviation TV programs like Air Crash Investigator quote altitudes in metric when most aircraft fly at altitudes in feet!

They do this because most people around the world use metric and don't really know how high 10,000 or 30,000ft really is (just that it is up there). They can comprehend metric distances however.

Quoting Mir (Reply 23):
The length of a meter may be arbitrary, but the way the system works (base 10) is certainly not. It makes far more sense than does the imperial system.

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DocLightning
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 1:04 am



Quoting L-188 (Reply 11):
The metric system is a completely arbitrary system of measures and doesn't make sense. in fact the meter doesn't even equal up to what it is supposed to because they made a mistake in the distance between the poles when they figure it out. They just looked at the distance to the pole and split it up by a million. No science behind that at all.

1m=100cm=1000mm=100,000µm
1g=1cc H2O=1/1000kg
1(Kg*m^2)/s^2=1n
1g=~10m/s^2

What doesn't make sense? I think that not being able to remember whether a fluid ounce is how much of a weight ounce and how imperial doesn't really measure mass, but weight and mis-uses it as mass.

Gah... Metric is far better.
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MrBrightSide
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 2:26 am

Currently live in US, and it is funny to drive next to a traffic sign showing San Francisco 25 mi / 40 km. So, there are some signs of duality in US.

But what does not make any sense is when in US I hear a word "ton" for measurement unit. And that same "ton" is 2240 lbs.... it's 1000 kilograms.  Wink

P.S. Metric system is a part of SI, or Système International d'Unités. And includes much more than meters.
P.P.S. Actually, its not so hard to switch... Farenheit vs. Celsius/Centigrade are much tougher thing to reconvert, but miles and feet into kilometers and meters... not so much. Times 1.6 or times 3 (estimate, but gives you a rough idea... and you won't be off by much  Wink
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Rafabozzolla
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 2:36 am

I agree that the system that makes sense is the one you can relate to. But the base 10 is surely a logical advantage of the metric system and, temperature wise, it makes far more sense to have freezing point at 0C that at 32F.
 
AC183
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 2:39 am

I was very amused when once as a kid when we were holidaying in the southern US, and stopped to pick something up at a grocery store when someone stopped and asked my dad how many ounces were in a quart. Of course Americans think in ounces and gallons, but don't have a clue there's a difference between US ounces and gallons and imperial ounces and gallons. So my Dad answered the question by giving far more information than the lady had been looking for, and probably left her more confused than before.

Another example - which is heavier, an ounce of feathers, or an ounce of gold? They're not necessarily the same - after all, gold is traditionally measured in troy ounces. Other examples abound of where there's possible confusion.

From my perspective the metric system gets rid of a lot of vagueness - there is no question what a millilitre is, or its relationship to other units of measure. However as a someone who works in a technical field in the HVAC industry, I'm very used to working in imperial units. I would say I'm more comfortable in fractional inches than millimetres. However I'm very good at conversions, and since I know metric quite well - it's just a matter of using it to get a feel for the numbers. Eventually I think metric will become the standard, but it will be a very slow process. Aviation will probably adopt it before the building components industries do. But between globalization, US engineers learning more metric in college, and the increasing amount of computerized equipment that can display in either unit of measure, the groundwork is being layed, so it's coming.
 
Cubsrule
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 2:44 am



Quoting AC183 (Reply 28):
But between globalization, US engineers learning more metric in college, and the increasing amount of computerized equipment that can display in either unit of measure, the groundwork is being layed, so it's coming.

"Hard" scientists in the US are learning exclusively metric in college these days... I suspect the engineers won't be far behind.
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sphealey
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 2:45 am



Quoting Rafabozzolla (Reply 27):
But the base 10 is surely a logical advantage of the metric system

Actually I would say both base 12 (even fractions of 1/2, 1/3, and 1/4) and base 16 (best for electronic calculation; might as well get used to our robot overlords) make more sense than base 10 in which many useful fractions are inconvenient.

sPh
 
Mir
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 2:59 am



Quoting Sphealey (Reply 30):
Actually I would say both base 12 (even fractions of 1/2, 1/3, and 1/4) and base 16 (best for electronic calculation; might as well get used to our robot overlords) make more sense than base 10 in which many useful fractions are inconvenient.

You might have a point if the whole imperial system was base 12, but it isn't. One foot is twelve inches, but one inch is divided into 16ths. And a mile is 5,280 feet. So how many inches in a mile? Or sixteenth inches? You'd need at least a pencil and paper to figure it out. Whereas going from millimeters to kilometers (1,000,000) can be done in one's head.

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
fxra
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 3:20 am



Quoting Ned Kelly (Reply 20):
I always hate it when aviation TV programs like Air Crash Investigator quote altitudes in metric when most aircraft fly at altitudes in feet! Which prompts me to my question regarding Russia, do pilots in Russia for example fly at 10,000 metres instead of 30,000 feet, or do the fly at the metric equivalent of 30,000 feet which is 9144 metres? Can anyone answer this?

The former Soviet Union (at least some fo them) and China are pretty much the ony regions of the world that are all metric. And the altitudes they use are usually something like 9600m or 7200m. When flying into these regions, there is a transition area where aircraft are moved from say FL300 to 9600m.

Quoting Mir (Reply 23):
When airplanes fly at metric altitudes, they separate by 300 meters. I can't say whether they would fly at 10,000 meters or not, but it would be a round (to the hundreds place) altitude like 9,700 meters or soemthing like that. They don't just convert every altitude level to exact meters and fly it.

Which leads to another reason for the imperial system to be used in altitude - 1,000 feet is a pretty good separation distance. 300 meters is good too, but in this rare case it's much easier to use the imperial system.

Recently China went to an RVSM system based on meters, I don't believe the Russians have migrated to an RVSM environment. So currently if you fly from ANC to PVG over Russian, you start off in Flight Levels based on feet, then transition to Meters before entering Russian airspace, and then after exiting Russian airspace into Chinese airspace, you transition to a Metric RVSM altitude. There is a significant amount of extra training for our crews flying international to make sure we are where we think we are. Add to it language barriers, it's demanding flying.

As a child of the 80's we were taught both metric and "imperial". I never really picked up the volume conversions for pints, quarts, gallons, etc... but I can get by with feet, inches, yards, and miles. And I'm also pretty good and doing mental conversions from feet to yards and pound to kilos. I can only hope my nieces and nephews growing up today are getting a move detailed explanation of SI versus the US measurements.

Back to aviation, I don't see the systems changing for the near future.

Quoting MrBrightSide (Reply 26):
But what does not make any sense is when in US I hear a word "ton" for measurement unit. And that same "ton" is 2240 lbs.... it's 1000 kilograms. Wink

I may be wrong, but 1 Ton (US) = 2,000 lbs. A metric ton (or as I alway see it written, tonne) is 1000KG, which as you points out is roughly 2,240lbs. So they're not exactly equal.

Quoting Zkpilot (Reply 24):
The reason why aviation generally uses imperial measurements such as feet is that the USA and the UK were the 2 major powers that be in the initial development of aviation and in the USAs case it has continued this. Events like WWII where the USA produced huge numbers of aircraft for itself and allies of course entrenched that standard. If Germany had won the war then most certainly the world would all be using metric (one of the few things that they did right). As the USAs power and influence internationally is on the wane (China and India are on the rise), expect to see more pressure for the USA to change to metric... like Canada and almost the entire rest of the world.

I doubt you'll see us Americans change in the near term (ie my lifetime), we seem to be head strong on being American and doing it our way dammit. Just as I don't expect to see China ever standardize it's aviation measurements to ICAO standards, just because they're Chinese.
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tdscanuck
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 3:24 am



Quoting MrBrightSide (Reply 26):
But what does not make any sense is when in US I hear a word "ton" for measurement unit. And that same "ton" is 2240 lbs.... it's 1000 kilograms.

That's "ton" vs. "tonne". Different things.

Tom.
 
banjo76
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 5:17 am

Since the metric system is as arbitrary as the the imperial systems I guess al of you guys, when designing parts of aircrafts still use the imperial system and go through the ton of conversion factors this system requires.
Have you ever worked with force/torque/work/power measurments and calculations with the imperial system?
Anybody of you can see it's much better to convert everything into metric system make calculations and at the end convert back to imperial (if you really want).
This is simply why the imperial system does not make any sense, and company governments should make efforts to kill this system. I know it takes time and money but having a unique system worldwide would be beneficial for everybody.
But converting US industry adopting metric standard would give too much of an advantage to European Companies that already manufacture fasteners, rings, screws bolts, washers, etc etc, in metric, and will flood the US isn't it?
If such decision was taken would you think that it would be wise to kill the metric and use the imperial.
I guess all of you know the answer.

And by the way, let's see which one makes more sense:
Imperial:
"give me that drill bit please", "which one the 17/64th or the 1/4", "the bigger please" ..... "uh"
Metric:
"give me that drill bit please", "which one the 6.75 or the 6.25", "the bigger please", "there you are", "thanks"
 
mbj2000
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 6:09 am

Interesting thing is, that the "imperial" system is not completely dead in some parts of Europe. In Germany for example, AFAIK they still use "Zoll" (inch) in the plumbing area...
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antonovman
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 6:34 am



Quoting MBJ2000 (Reply 35):
Interesting thing is, that the "imperial" system is not completely dead in some parts of Europe. In Germany for example, AFAIK they still use "Zoll" (inch) in the plumbing area...

I lived in Germany for 10 years and was astonished when i went to buy plumbing supplies and found them to be in 1/2 or 1/4 inch sizes, just like the UK.
The only problem was, i didnt know that "Zoll" meant "Inch" . I thought it was the "customs" having seen signs at the airport, and wondered what the sales guy was talking about
 Big grin
 
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flyingclrs727
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 7:11 am



Quoting Mir (Reply 31):
You might have a point if the whole imperial system was base 12, but it isn't. One foot is twelve inches, but one inch is divided into 16ths. And a mile is 5,280 feet. So how many inches in a mile? Or sixteenth inches? You'd need at least a pencil and paper to figure it out. Whereas going from millimeters to kilometers (1,000,000) can be done in one's head.

But a square mile is 640 acres which is also known as a section. It can be divided using base 10 or powers of base 2 without the use of fractions. That can be useful for dividing land among heirs. Liquid volumetric units are in powers of base 2 as are fractions of an inch. A pound is about the weight 16 fluid oz of water.

1 table spoon = 1/2oz = 2-1oz
1 ounce = 1 oz = 20oz
1 cup = 8oz = 23oz
1 pint = 16oz = 24oz
1 quart = 32oz = 26oz
1/2 gallon = 64oz = 26oz
1 gallon = 128oz = 27oz

For some reason the teaspoon doesn't follow this rule and is 1/3 of a table spoon.

Personally I find it easier to use SI units, but it's nearly impossible to find metric measuring cups and spoons in stores in the US. I have never seen cook books in the US use metric unitis.
 
TheSonntag
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 7:26 am

There are quite a lot of applications for which the use of the metric system makes sense, for others it does not...

I do not think that it would be useful for aviation. Not only because everybody is used to the existing system - why change something everybody is used to, if there is no real benefit in it - but also because the Meter is around 3 times a feet. In times of RVSM, it makes more sense to use smalller flight level numbers. With meter, you would get different numbers.

I do think, however, that kilogram and the like should be used, but this is mostly the case if I am correctly informed...
 
mbj2000
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 8:15 am



Quoting FlyingClrs727 (Reply 37):

1 table spoon = 1/2oz = 2-1oz
1 ounce = 1 oz = 20oz
1 cup = 8oz = 23oz
1 pint = 16oz = 24oz
1 quart = 32oz = 26oz
1/2 gallon = 64oz = 26oz
1 gallon = 128oz = 27oz

Wow, put this way the imperial system suddenly makes sense!  Smile
Thanks for this informative post and welcome to my RU list!
Like most of life's problems, this one can be solved with bending -- Bender Unit 22
 
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flyingclrs727
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 8:36 am



Quoting MBJ2000 (Reply 39):
Thanks for this informative post and welcome to my RU list!

Thanks, I was beginning to feel like Rodney Dangerfield.
 
BrianDromey
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 9:12 am



Quoting David L (Reply 5):
Yes, the metric system is tidier but half the aviation world changing from one system to another could be a problem.

Well in Ireland we changed from Miles/Hour to kilometers per hour one day and there were no serious problems. If the change is well publicised and people know the conversion factors then there is no major problem.

Quoting David L (Reply 5):
I guess the USA being so influential in western aviation, and therefore the UK, indirectly, has to take some of the blame.

The UK is very fond of imperial measurements. I think its more a political thing than anything else though.....

Quoting L-188 (Reply 11):
The metric system is a completely arbitrary system of measures and doesn't make sense. in fact the meter doesn't even equal up to what it is supposed to because they made a mistake in the distance between the poles when they figure it out. They just looked at the distance to the pole and split it up by a million. No science behind that at all.

To be fair I think the metric system is slightly easier to understand because of its realtionship with multiples of 10. Each unit is a multipliplication of the meter by a factor of 10, with the appropriate naming (eg nano, pico, mili, kilo, etc). This nomenclature can be used with any metric unit eg, volume, sound, etc.

Personally I find the metric system pretty easy to understand, but I grew up using both imperial and metric. In Ireland we have a weird relationship with both systems! Probably the best of both worlds. What is noticable is that a lot of trades now refer to things exclusively in "mills"(millimeters). Most likely because materials are now coming mesasured as metric as opposed to imperial, as are architects drawings.

Brian.
Next flights: MAN-ORK-LHR(EI)-MAN(BD); MAN-LHR(BD)-ORK (EI); DUB-ZRH-LAX (LX) LAX-YYZ (AC) YYZ-YHZ-LHR(AC)-DUB(BD)
 
Ferroviarius
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 10:11 am

Good morning,

as a matter of fact, it is ONLY the US and Lybia and Myanmar that have not officially adapted the metric system (source en.wikipedia.org, look up "metric system"). However, according to Wikipedia's article on the SI (Système International, it's not Lybia but Liberia).
In the UK, as far as I know, they are still allowed to in-officially use the imperial system (that was a psychological pre-condition for accepting the Lisboa treaty, which hopefully will form the basis for a European Constitution). During an interview on Swedish TV (SVT1) years ago, an Englishman on the streets of London answered to the journalist's question, why Britons still stick to the imperial system that it would not have been Napoleon who has won the war. Well, this might be an individual person's answer (he was serious about it).

Among other international institutions, the IUPAC regulates the use of units in Science (and there it's metric, only) and the legal systems in a large number of countries oblige the resp. countries' institutions to stick to IUPAC's rules. In the US, the NIST (http://www.nist.gov/) provides Even the NASA demands the use of metric units (and nevertheless, they lost the Mars Climate Orbiter because somebody didn't stick to the metric system). I am a physicist and to the physicists' everlasting ashameness, many of them are still using Ångström instead of 0.1nm and fermi instead of femtometer (where the latter is not such a problem since 1fermi = 1femtometer = 1*10^-15m = 1fm while the former is a problem since it involves two non ASCII characters, "Å" and "ö", which are not even displayed correctly in this form sheet while I am editing this text).


The big advantage of the metric system is that there are a lot of factors 10 in jumping between units, while the imperial system has a lot of different factors between the different units. Since we also all use the arabic system of numbers in the entire world, based on ten digits (0, 1, 2, 3, 4, 5, 6, 7, 8, and 9), the metric system matches our common system of numbers much better than the imperial system.


However, it would mean a considerable effort of the national economy of the US to radically switch to the metric system, so I fear there is little hope that this is going to happen in the near future.

The argument that the imperial units would be more natural is, emotionally, justified. However, the mismatch between our decadic system of numbers to the natural units to my mind is a more severe penalty than the mismatch between our "natural feelings" and our system of measurement.

Best,

Ferroviarius
 
Schtaiws
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 10:34 am

as an engineer i can't see how anyone can function effectively using imperial, SI is so straightforward...

as a pilot however i'd have a lot of trouble adjusting to metric, it'd take a while to get my head around...
 
sphealey
Posts: 286
Joined: Tue May 31, 2005 12:39 am

RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 10:56 am



Quoting Mir (Reply 31):
You might have a point if the whole imperial system was base 12, but it isn't.

I wasn't referring to the Imperial or ANSI measuring systems; I was speaking generically. The committee that designed what was then known as the metric system had free choice of whatever base they thought best and designed units based on that base. They chose decimal but that was not a given.

Quoting Mir (Reply 31):
Whereas going from millimeters to kilometers (1,000,000) can be done in one's head.

Only because you have been doing it since early childhood. If you had been doing base 12 arithmetic since then you would find it just as easy. In fact after only a semester of PDP-11 programming I had no problem doing base 8 in my head.

sPh
 
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GrahamHill
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 11:46 am



Quoting MBJ2000 (Reply 35):
Interesting thing is, that the "imperial" system is not completely dead in some parts of Europe. In Germany for example, AFAIK they still use "Zoll" (inch) in the plumbing area...

In France, we use the inch for PC monitors (not for TV screens, though...) and wheel rims.
"A learned fool is more foolish than an ignorant one" - Moliere
 
David L
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Joined: Tue May 18, 1999 2:26 am

RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 11:47 am



Quoting BrianDromey (Reply 41):
The UK is very fond of imperial measurements. I think its more a political thing than anything else though.....

I think it's just that not enough people think the change is worth the effort while in other other countries they did. It's what we're familiar with - it's the desire to stick to what we know rather than politics. What do we gain by using km/hr instead of mph? It's not as though foreign drivers could accidentally find themselves on UK roads (well, mainland UK, anyway)  Smile .

I don't feel strongly one way or the other. As someone else mentioned, we are mostly metric, e.g. in science and modern engineering. It's just a few areas that the general public use that tend to stick to imperial units, such as road speeds and approximate dimensions of their garden. for example. I was taught the metric system exclusively at school. If we needed to do any calculations regarding road speed, we might be more inclined to change but we don't.

Quoting Ferroviarius (Reply 42):
an Englishman on the streets of London answered to the journalist's question, why Britons still stick to the imperial system that it would not have been Napoleon who has won the war. Well, this might be an individual person's answer (he was serious about it).

Definitely an individual's answer.  Smile

Quoting Sphealey (Reply 44):
Quoting Mir (Reply 31):
Whereas going from millimeters to kilometers (1,000,000) can be done in one's head.

Only because you have been doing it since early childhood. If you had been doing base 12 arithmetic since then you would find it just as easy. In fact after only a semester of PDP-11 programming I had no problem doing base 8 in my head.

It's because everyone is educated in Base 10, because most of us have 10 digits on our hands. Multiplying and dividing by powers of ten only involves shifting the decimal point.
 
YWG747
Posts: 53
Joined: Mon Feb 11, 2008 2:19 am

RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 11:51 am

The metric system makes way more sense once you have learned it.
Everything fits equally. 1000 grams for one kilogram not like 16 ounces in a pound.
Now that is messed up
 
ShannoninAMA
Posts: 1211
Joined: Tue May 22, 2007 1:37 pm

RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 12:20 pm



Quoting FlyingClrs727 (Reply 37):

But a square mile is 640 acres which is also known as a section. It can be divided using base 10 or powers of base 2 without the use of fractions. That can be useful for dividing land among heirs. Liquid volumetric units are in powers of base 2 as are fractions of an inch. A pound is about the weight 16 fluid oz of water.

1 table spoon = 1/2oz = 2-1oz
1 ounce = 1 oz = 20oz
1 cup = 8oz = 23oz
1 pint = 16oz = 24oz
1 quart = 32oz = 26oz
1/2 gallon = 64oz = 26oz
1 gallon = 128oz = 27oz

Exactly. Its not like someone decided to chose random numbers. There is order involved in it. Either way...I think it really boils down to this -

Quoting Sphealey (Reply 44):

Only because you have been doing it since early childhood. If you had been doing base 12 arithmetic since then you would find it just as easy. In fact after only a semester of PDP-11 programming I had no problem doing base 8 in my head.

Shipwreck alert. Head on over to Airspaceonline.com.
 
beechnut
Posts: 551
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RE: Use Of Metric System In Aviation

Mon Apr 28, 2008 1:06 pm



Quoting DocLightning (Thread starter):
So why are airspeeds given in kts?

1 nautical mile = the distance of 1 minute of arc at the Earth's equator. Therefore, a very useful unit for navigation calculations back in the days when such things were calculated manually and distances were measured with a protractor on a map.

Beech

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