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Why doesn't aviation use standard (metric) units?

mh wrote:

furlongs/fortnight

Some units of measurement are application-specific, for example furlongs are only now used in horse racing. UK schools teach kilos for weight, but children still use the stone (14lb; 6.35kg) when weighing themselves. Fortnight seems to be going out of fashion, being replaced by “two weeks”… we could say “se’en night” instead of week

When you’re the only person using a unit it’s ok, as you just use the relevant number, e.g. manifold pressure in pièzes. When other people or ATC are involved it gets harder, e.g. altimeter in metres when others are in feet. I once heard an American pilot given the QNH in Europe ask “can I have that in inches?” It was funny, but you had to be there.

Recently reading War and Peace (translated) it needed some cross referencing as area is measured in versts, short distances in arshims and temperatures in degrees Réaumur. A bit annoying at times, but it definitely added to the experience.

There are loads of interesting archaic systems of measurement, but my personal favourite is the revolutionary calendar: today is Septidi 17 Frimaire in the year 227. Republican democracy and the metric system were imposed at gunpoint: maybe this is what aviation needs?

EGHP-LFQF-KCLW, United Kingdom

@alioth even for your planned intersteller travel (we are not yet there), you will have switch back for common man units to measure distance, scientists can’t just use speed of light these days: distances between galaxies is measued in Parsecs, wich relate to Earth/Sun angles and time, the name had its sucess as it sound along Persian/Greek Parsang: if you have an army, it would march 5 Persecs a day…

ESSEX, United Kingdom

Airborne_Again wrote:

I suggest we use Plack units.

I mean “Planck” of course…

ESKC (Uppsala/Sundbro), Sweden

pardon my ignorance but what the hell is a hectolitre?

UK, United Kingdom

Fenland_Flyer wrote:

pardon my ignorance but what the hell is a hectolitre?

100 liters

LDZA LDVA, Croatia

Emir wrote:

Fenland_Flyer wrote: pardon my ignorance but what the hell is a hectolitre?

100 liters

And same for hectopascals (hPa) = 100 pascals
(More SI prefix geeking at https://en.wikipedia.org/wiki/Metric_prefix#List_of_SI_prefixes)

Nympsfield, United Kingdom

When some change is applied to units of measure such as millibars to ??? (I forget what) and then to hectopascals, for whose benefit is this done? What was wrong with millibars for example? What is at all ambiguous about saying 1000 litres please? etc. I cannot imagine the changes come from actual pilots.

Last Edited by Fenland_Flyer at 30 Nov 16:16
UK, United Kingdom

Fenland_Flyer wrote:

When some change is applied to units of measure such as millibars to ??? (I forget what) and then to hectopascals, for whose benefit is this done? What was wrong with millibars for example? What is at all ambiguous about saying 1000 litres please? etc. I cannot imagine the changes come from actual pilots.

I would guess it is for the general benefit of society by reducing the number of different units used for the same things.

ESKC (Uppsala/Sundbro), Sweden

Airborne_Again wrote:

I would guess it is for the general benefit of society by reducing the number of different units used for the same things.

Point taken but as far as I can see there is often just a change of “label” so who does that benefit.? Millibars to Hectopascals as an example. Furthermore,who in the world decided on this change in particular?

UK, United Kingdom

It’s a bit of a strange addition to me as the litre is a non SI unit.

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