Menu Sign In Contact FAQ
Banner
Welcome to our forums

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

Off_Field wrote:

I’ve yet to hear someone suggest we switch from degrees to radians for flying, despite them being more sensible for other mathematics.

Believe it or not, but at the beginning of my PPL studies, I was forever converting angles to radians in my head, to visualise them, and to have an approximation of their sine/tangent/cosine. After a few months, I got used to degrees.

ELLX

When I do the above mentioned climb/descent/runway length/speed performance calculations (all in feet and minutes) I don’t convert to degrees, I use the gradient as-is, which is obviously for small angles the same as radians.

Given the relation to the common use of lat/long coordinates, Nm make quite a lot of sense. One thing I miss from the electronic maps on our various GPS devices is the lat/long markings on aeronautical charts. These facilitate mental distance and time to distance estimates, given the ready conversion to Nm and Kt.

If aviation (and maritime too) were to ever move away from Nm/Kt, then one should really start with the geo-coordinate mapping system so that any distance/speed units are related to that. But that would immediately impact all our nav databases.

LSZK, Switzerland

chflyer wrote:

One thing I miss from the electronic maps on our various GPS devices is the lat/long markings on aeronautical charts.

Garmin MFDs can display a lat/long grid, but indeed it seems that GNS & GTN units cannot.

ELLX

chflyer wrote:

Given the relation to the common use of lat/long coordinates, Nm make quite a lot of sense

So does the Gradian or gon (full circle = 400 degrees) with decimal subdivisions, combined with the metre.

A kilometre on a great circle is 1/100th gon (a centigon), giving the equivalent of a nautical mile being 1/60th of a degree.

But at that time, the seas were dominated by Britain, and it never caught on.

Biggin Hill

Emir wrote:

Exactly I really need explanation on how inch of feet or any unit is intuitive. All measures are men invented and whatever you learn to use in particular activity simply works.

If you want “natural”, try Planck units.

Last Edited by Airborne_Again at 01 Dec 22:15
ESKC (Uppsala/Sundbro), Sweden

Cobalt wrote:

So does the Gradian or gon (full circle = 400 degrees) with decimal subdivisions, combined with the metre.

So that could be the starting point for a change. How widespread is its use? Are any maps published with it? Almost everyone knows about lat/long. I wonder how many people have even heard of the gon, let alone make actual use of it. It would be a big job to get a world full of pilots and mariners to switch….. as indicated in this thread, momentum plays a major role in any attempt to change and that’s likely the primary answer to the subject question.

Last Edited by chflyer at 01 Dec 23:31
LSZK, Switzerland

The only “gon” I know is in “gone down the pub”

Administrator
Shoreham EGKA, United Kingdom

chflyer wrote:

So that could be the starting point for a change. How widespread is its use?

It is pretty much dead.

Biggin Hill

The Concorde flew, and although not a commercial success I think most will agree that it was an technical marvel. That despite the fact that the two manufacturing countries used different units for everything. So these problems can definitely be overcome.

On the other hand, there was the Gimli glider accident (pounds vs kgs of fuel-confusion), and I have also had a small number of tense moments as an instructor with pilots being used to fly in knots, now being checked out in an older aircraft of the same type, but with IAS in mph, making for slow approaces. KTs and MPH are close enough that the numbers were confused without the pilots noticing.

Last Edited by huv at 02 Dec 14:15
huv
EKRK, Denmark
Sign in to add your message

Back to Top