On Thursday, 17 January 2019 13:20:49 UTC, Chris B wrote:
On 17/01/2019 12:32, whisky-dave wrote:
On Thursday, 17 January 2019 10:57:00 UTC, Chris B wrote:
On 16/01/2019 13:27, whisky-dave wrote:
On Tuesday, 15 January 2019 17:41:18 UTC, Rod Speed wrote:
"whisky-dave" wrote in message
...
On Tuesday, 15 January 2019 16:23:34 UTC, Rod Speed wrote:
"whisky-dave" wrote in message





Why? Because the Americans felt comfortable with that, and the rest of the world followed!

Everything is in feet!


Actually the flight level abbreviation FL refers to the altitude in
thousands of feet but not everything is in feet.

Russia, China (and a few other places) use meters. For Older western
aircraft with mechanical displays this means a look up table for the
aircrew to see what altitude they should be at. (most modern electronic
displays can show ft or m)

If really interested the FAA document regarding some aspects of Chinese
airspace is here

https://www.faa.gov/air_traffic/sepa...1425125 5.pdf

Well that is an exciting read, but perhaps you can explain one thing.

For example; if an aircraft is cleared to
8900m and flies with the metre altimeter and
does not use the China RVSM conversion
table his actual altitude in feet would be
29,200 instead of 29,100. This compromises
the 1000ft vertical separation!

If china can sort it out whay can;t teh USA or the rest of the world.

Taking your second point first the rest of the world could choose to fly
in metres rather than feet, they just don't, and as it is now a very
small minority that use m you could argue that they should use feet.

But most of the world has gone metric. It's called metric airspace.


It says so here.

https://www.quora.com/In-aviation-wh...asured-in-feet

For most aircraft still flying with analog gauges, when flying into metric airspace, we use a simple conversion card on a clipboard. When Shanghai Control clears us to descend to 3600 meters, we check the card and descend to the equivalent: 11,800 feet.



As for your first point it all starts to get complicated. Aircraft
altitude is measured by air pressure,

Is that relivant and don;t they measure from sea level rather than land.


at low altitude the pressure drops
by about 1 millibar per 30 feet, At high altitude a 1 millibar pressure
drop represents a much bigger distance. Up until about 20 or 25 years
ago all high altitude aircraft were procedurally separated by 2000ft.
due to the decreasing accuracy at high altitude

The weather changes air pressure do so how does that affect the meters.


Due to the demand for high level flight routes (initially over the
Atlantic) there was a major exercise to reduce this separation to 1000ft
(Reduced Vertical Separation RVSM) - but this has very specific
requirements on the proven accuracy of the aircraft altitude (and other)
systems). If you cant meet the requirements you cant fly in RVSM airspace.

This RVSM which was initially only over the Atlantic has now spread to
worldwide - but complications arise when feet systems adjoin metric
systems.

So there are two system and not just feet like the americans like to use.



The detail answer to your query is given later in the paper.
=================================

Altitude/ Flight Level Clearances To prevent undesirable ACAS TA/RA
triggering in RVSM airspace and since most civil aircraft use FEET as
the primary altitude reference with a minimum selectable interval of 100
feet;
a) ATC will issue the Flight Level clearance in metres. Pilots shall use
the China RVSM FLAS table to determine the corresponding Flight Level in
feet. The aircraft shall be flown using the flight level in FEET.

b) Pilots should be aware that due to the rounding differences, the
metric readout of the onboard avionics will not necessarily correspond
to the cleared Flight Level in metres, however, the difference will
never be more than 30 metres.

Strand they don;t stat that in feet isnl.t it, if that rally is the defaault for the ROTW .


c) Aircraft equipped with metric and feet altimeters such as the Il-96,
Il-62, Tu-214 or Tu-154 shall use the feet altimeter in RVSM airspace.
If unable to use the feet altimeter, the operator shall contact the
China RVSM Program office and apply for special approval to operate into
China RVSM as described in China AIP section 9 (Contact information can
be found in section 9.4.3).

Outside of the RVSM FL band, metre altimeters may be used.


--
Chris B (News)