FlightAware Discussions

HBAL0328 Heading North

The balloons launched from Sioux Falls usually travel south/southeast. This one is heading northeast.

Note the difference between barometric and geometric altitude.

image

1 Like

That is unusually large. I wonder if it is an accuracy problem with the barometric altitude (accuracy typically drops as you get higher - one of the reasons that RVSM is limited to <= FL410)

1 Like

That 68k feet altitude is out of calibration range for barometric sensors, I think it’s just maxed out that sensor output :slight_smile:

This sensor has a lower limit of 15 kPa: https://www.apogeeinstruments.com/barometric-pressure-support/
From this table, the 15 kPa is happening at 45k feet, and at 70k feet there is only 4.5 kPa left:
https://www.avs.org/AVS/files/c7/c7edaedb-95b2-438f-adfb-36de54f87b9e.pdf

That would be a very strange choice of sensors for a balloon that goes that high.
While it’s not in RVSM any more, the level it’s displaying is sometimes used by other aircraft (military?)
Or is FL500 basically irrelevant?

No, some private jets can get up there. Gulfstreams, Citations, Learjets, etc can cruise at 50,000.

Aircraft Type: U2
Altitude (Barometric): 60,000 ft

Right now around 150 nmi north of SFO.

U2 doesn’t use the off-the-shelf sensors.

That sensor above was an example. Probably Gulfstreams have pressure sensors that work acceptable at 50k feet (they are usually lower though, 43-46k) , and that HBAL indicates 50k too, but 70k is a different animal.

PS: Just looking now, filtered above 47k feet, and below 65k, there is only ONE flying object - the HBAL0328