Comments on: Should aviation switch to the metric system ?

By: Vincent

Vincent — Sun, 26 Apr 2009 11:43:15 +0000

@Physics: I see that you already thought a lot about that. Being in the business of ATC systems, let me show you some of the problems typically relating to such a transition.

1) The whole system must be adapted at once, on both ATC and aircraft side. What to do with light aircraft without glass cockpits ? Two altimeters ? Altimeters with two scales ? Glass-cockpits shall not be an issue as they can be updated with a bi-units software, but there are still lot of aircraft flying with mechanical instruments… not to mention the backup instruments of glass-cockpits.

2) Controllers have to be trained and checked on new procedures, whatever the change. They go through theory and simulator sessions. ATCOs shortage is a common problem in Europe and getting them out of the normal roster for long training times can be complex.

3) If no serious safety advantage is demonstrated, no airline or air traffic authority will take the step. Being a nice thing from an engineering point of view does not means it brings any benefit.

4) All centers (and in Europe this means all centers from several ATC organisations) shall adapt at the same time, to make possible to exchange flights at pre-defined altitudes.

Finally, you can think of RVSM. This consisted in the addition of new flight levels, thanks to the increased accuracy of baro-altimeters. It took several years until sufficient aircraft were equipped and all ATC systems adapted… The rate of innovation in ATC is rather slow, but may be this will come. Not soon.

By: Physics

Physics — Sat, 25 Apr 2009 21:38:51 +0000

Well to minimize the disruption it would be best to do it when fewest pilots you the system. Which would be a winter during an economic downturn. Controllers change the areas they serve from time to time, possibly not often but does happen, so they need to relearn values for a specific location. It should be easy to implement in class A airspace before the rest since it is altimeter setting separated anyway. I think relearning values would at most be a few hours of ground school and possibly a written test and stressed on the regular flight review. On the controllers side is there any regular proficiency review or test or training anyway? I assume there is so it could be part of that. Charts are published on a few week cycle anyway so one day a new set would be metric only. For the dual use situation would be dangerous. The switch should be in the middle of the night on a normally quiet ATC day. Possibly have extra controllers for that night. I understand it would be tough for a few weeks but everyone would get used to it. We change the time twice a year and a few days are wacky, especial since Zulu is always constant. It might take some time to for the revised procedures to be created/converted but it would be an opportunity to possibly hire more people for a few months.

And no Vincent I am not a pilot but I would to be. I have at least six more years of University before I can even think of being a pilot. I live in USA so I might be making assumptions about the charts being republished and training. Thanks for the reply.

By: Vincent

Vincent — Sun, 19 Apr 2009 11:34:40 +0000

@Physics: from an equipment point of view this would indeed be an easy change… but you have to think of what is behind. The ATC software engineer in me is talking here. All systems should be adapted to metric system, all procedures and charts should be re-published, and air traffic controllers should be re-trained to the new values, even if the procedures remain the same. Can you imagine the change for a controller who knew for years that the ILS interception for a given airport is at 7′000 feet and that the minimum radar vectoring altitude in the area is 5′000 feet having to change all of that to meters ?

Not to mention the transition phase where ATC should be able to offer both metric and non-metric clearances ? What a mess…

By: Physics

Physics — Sun, 19 Apr 2009 04:39:27 +0000

With glass cockpits becoming popular a change won’t be as hard. It will be as easy as loading new firmware on the hardware side. Most pilots on earth already know how to use metric so maybe just a check out flight and a short exam over new procedures would do it along with regular recurrent training and flight reviews.

By: Paul

Paul — Wed, 02 Jul 2008 02:28:54 +0000

No, I saw it, I was just having some fun. I try and talk to my wife about this stuff and she just looks at me and says “how much time do you spend thinking about this? why don’t you do something productive like clean your desk” It’s nice to discuss something of meaning…

By: Yellowbird

Yellowbird — Tue, 01 Jul 2008 19:38:10 +0000

Paul,

Perhaps you didn’t see the tongue in my cheek? I guess the distance it protruded wasn’t noticeable enough to justify it’s use as the basis of a unit of measurement.

By: Paul

Paul — Tue, 01 Jul 2008 17:23:19 +0000

I understand your point but If we took your rationale we would still be telling time by the sundial. Human body parts obviously vary in length (how’s the joke go? Why do women make bad carpenters…”) and the speed of light and time is something pretty quantifiable and measurable. There is a known constant scientific standard. Besides, I like units of 10 a lot better than dividing things by 12, mulitplying by 3, multiplying by 1760, 5280 or whatever…don’t you? We vastly improved our methods of measuring, or should I say MOST of us have. We made the whole world speak english, maybe we should compromise and give them the metric system.

By: Yellowbird

Yellowbird — Tue, 01 Jul 2008 16:07:07 +0000

“It is seriously embarrassing that the leader of the free world bases it measurements on human body parts.”

No more so than the idea that we should base measurements on the distance light travels in 1⁄299,792,458 of a second in a complete vacuum.

I personally use the FFF (Furlong/Firkin/Fortnight) system and base all my flight planning on a cruising speed of 371197.2178780147 furlongs per fortnight

By: Paul

Paul — Mon, 30 Jun 2008 20:27:58 +0000

Did you know that there are only 3 countries in the ENTIRE WORLD that have NOT adopted the metric system? Liberia, Myanmar and the United States. That is messed up. The word “inch” means the same as the word “thumb” in some languages. The “foot” dates to 2575 B.C!!! It is seriously embarrassing that the leader of the free world bases it measurements on human body parts.