Up until the early 90's most instrumentation was mechanical and everyone had mechanical altimeters in either feet or metres, if you flew in a country with a different unit of height measurement you had a chart to convert the appropriate flight level from feet to metres and vise versa. You had to scramble if you did not have a convenient conversion chart that listed the equivalent Flight levels in either system. Some airplanes had a separate meter altimeter for reference (and safety). I've heard of pilots who flew to Russia without realizing they used metres, there was panic in the cockpit when they had to figure it out.
Nowadays everyone has "glass" cockpits where the instrumentation is displayed on a screen, you can now push a button (or soft button on new aircraft) that changes the display from metres to feet. A button also changes the pressure setting from inches mercury to hectopascals depending on which part of the world you operate in. When we fly in China we switch to metres, they give us an altitude, we set the required altitude in metres and the instrumentation displays everything in metres. Air Traffic control in Russia (and the former CIS states) also gives distances in kilometres while our displays still show nautical miles. Because the foot is a smaller size than the metre, it seems the world is transitioning more to foot Flight levels than metre Flight Levels because it more easily rounds to whole thousands. Eastern Europe used to be metric and is now feet. The default separation is now 1000 feet or 300 metres. If it gets closer, metres might become the default, but I doubt we'll be flying closer than 300 metres vertically in the near future, it's possible we might go to 200 metres (660 ft) vertically rather than 500 feet (150 m) with GPS altitude instead of barometric altitude. The closing speed of two aircraft going in opposite directions is roughly 2000 km/h! Mike Payne On 28/04/2012, at 15:37 , Kilopascal wrote: > This is something I was wondering about. If China, Russia, and Mongolia > define altitudes in metres, then it is reasonable to assume that planes > purchased or built for these countries would have their altimeters in metres > and no problem exists. But what happens when a plane from outside should fly > into their space and not have a metric altimeter, how are they handled? > > The same for, say a Chinese plane flying in feet territory. > > In each case, does the pilot tell ground control what units his altimeter is > calibrated in and then be given instructions in those units? Harmonizing > flight levels between countries using metres and those using feet makes sense > for safety reasons, but there is still the issue of instrumentation. > > I'm also wondering at what point Chinese influence will be strong enough to > force its neighbors to switch to metres and follow their lead. > > If the rest of the world were to adopt metric instrumentation eventually, > what do you think would be the most efficient and effective way to switch > over? > > > From: John M. Steele > Sent: Saturday, 2012-04-28 14:15 > To: Kilopascal > Subject: Re: wp176_en.pdf metric flying in China > > The "metric flying" is a bit of a crock. I couldn't find the detailed > document for China but did for Mongolia (same scheme) > http://www.aviationmanuals.com/references/2011-02/Mongolia_AIC-2011-03-en.pdf > > Look at sections 2.2-2.5. Process is: > Get assigned altitude in meters > Consult conversion chart > Fly in feet > > Aircraft MUST be equipped with and use their foot altimeter to fly in RVSM > space. Note in particular 2.5, your metric altimeter will lead you astray. > > Somehow, I expected metric altitude to be "more real." I don't entirely > understand it, but I think it is to minimize the altitude change for > commercial aircraft in high altitude cruise when crossing from foot-space. > > --- On Sat, 4/28/12, Kilopascal <[email protected]> wrote: > > From: Kilopascal <[email protected]> > Subject: wp176_en.pdf metric flying in China > To: "U.S. Metric Association" <[email protected]> > Date: Saturday, April 28, 2012, 1:42 PM > > Something of interest to those interested in metric in flying: > > http://legacy.icao.int/icao/en/assembl/a36/wp/wp176_en.pdf > > No virus found in this message. > Checked by AVG - www.avg.com > Version: 2012.0.1913 / Virus Database: 2411/4964 - Release Date: 04/28/12 >
