On Friday, October 16, 2015 at 2:20:18 AM UTC+3, Ramy wrote:
On Thursday, October 15, 2015 at 1:15:18 PM UTC-7, Ian wrote:
On 10/10/2015 12:20, Judy Ruprecht wrote:

7. SC3 Annex C Section 3.4 now allows a PR with pressure sensor (eg
Flarm) to have that pressure sensor ignored & the GPS altitude used.

This is the most significant change to the Sporting Code, for club
pilots, since the invention of GPS. Now it is possible to fly badges, up
to gold level, in any glider equipped with a Flarm. As the GPS altitude
can be used instead of the pressure altitude, there is no longer a
requirement for that Flarm to have a current calibration certificate for
the pressure sensor.

As many club pilots have access to club ships equipped with Flarm, they
can now arrive at their club on a weekend and go and fly badge flights
without first having to get hold of a calibrated FR - which might not be
readily available.

However the applicable country's National Association will have to do
their homework to put the necessary approvals in place to use Flarm as a
PR. This has already been done for a number of countries, and there are
sample approval documents for Flarm available in German, French and
English, which could easily be adapted by other country's National
Associations.

Sensibility is finally catching up with red tape...

Ian

Maybe I am missing something, but if GPS altitude can be used instead of pressure altitude, how can you verify that the pilot did not bust class A? The difference between pressure and GPS altitude can be close to 1000 feet near 18K. Same question goes for altitude gain and loss measurements.

GPS bounces around, especially in altitude due to not often having satellites near the zenith. But if you average it over 10 or 15 minutes then it's very accurate. if you're not moving.

Of course, gliders don't stay put for 10 or 15 minutes. But if you have a pressure altimeter then you know how much you went up and down at each GPS reading, even if the altimeter isn't calibrated or set to QNH. In fact you use the GPS to continuously calibrate the pressure altimeter. Whatever the average difference is between GPS and pressure attitude over the last 15 minutes, that's how much you should adjust the pressure altitude reading by. This compensates for both unknown QNH and unknown altimeter calibration at the same time.

That gives you accurate physical WGS84 altitude, which is perfect for task verification purposes of altitude gain or loss.

"Busting Class A" is a different matter as that's based on pressure level not actual altitude. For that, you need either a calibrated pressure altimeter (only), or your true altitude from the GPS+uncalibrated altimeter combo AND the area QNH.

(I don't know whether FLARM combines the GPS and pressure in the way described, but you'd certainly hope so .. it's not rocket science)