How would this work in practice?

Do I request (say) FL300, and somehow before I get there atc says “sorry, your ASE is too large today, maintain FL280”? Or do I ask atc “is my altimeter error acceptable today so that I can go to FL300” before I ask for such an altitude? What equipment suffix would I file? Can I file FL300 if I don’t know whether with today’s conditions I will be able to get it? If I cross a center boundary might their equipment be just different enough that one would allow me but one would boot me out of RVSM space?

While I like the theory, and I can see the change in the equipment rule language you are pointing out, it sure could use some FAA clarification to become practical.

I’d love for someone (else) to be the guinea pig.

But then I am a very simple man so this might be too practical.

How would this work in practice?

Do I request (say) FL300, and somehow before I get there atc says “sorry, your ASE is too large today, maintain FL280”? Or do I ask atc “is my altimeter error acceptable today so that I can go to FL300” before I ask for such an altitude? What equipment suffix would I file? Can I file FL300 if I don’t know whether with today’s conditions I will be able to get it? If I cross a center boundary might their equipment be just different enough that one would allow me but one would boot me out of RVSM space?

While I like the theory, and I can see the change in the equipment rule language you are pointing out, it sure could use some FAA clarification to become practical.

I’d love for someone (else) to be the guinea pig.

The problem with that approach is that if your error is caused by static port position, or other static source error, then all the altimeters, air data computers and encoders would all see the same error. ATC only knows your altitude by what the encoder says.

The problem with that approach is that if your error is caused by static port position, or other static source error, then all the altimeters, air data computers and encoders would all see the same error. ATC only knows your altitude by what the encoder says.

With geometric altitude reported by GPS via ADS-B, ATC can now know your real baro altitude EVEN IF your static system is messed up.

How? By converting GPS altitude to baro altitude in FAA computers.

So ATC can tell, in real time, if your mode C altitude and your true baro altitude are mismatched.

Which brings me back to a question I've asked a number of times, namely - why don't we just switch everyone to GPS altitude? Way more accurate, consistent across weather conditions, and reliable.

Seem to me the easiest way to be:

ME: Center N850VT, level FL280

ATC: N850VT, OAKLAND, we show you at FL27.7

ME: Roger Center correcting altimeter to FL27.7

ATC: Climb and maintain FL280

ME: Climb and maintain FL280, N850VT


But then I am a very simple man so this might be too practical.

The other problem is, you just admitted to a pilot deviation by being 300' off your assigned altitude on a recorded party line....

>>>The other problem is, you just admitted to a pilot deviation by being 300' off your assigned altitude on a recorded party line....<<<

Well not if this were the accepted practice under new RVSM rules.

The problem with that approach is that if your error is caused by static port position, or other static source error, then all the altimeters, air data computers and encoders would all see the same error. ATC only knows your altitude by what the encoder says.

Just curious, but isn’t gps altitude HAE?

Do FAA computers convert HAE to pressure altitude?

That seems to allow room for some error, given the number of variables involved in a PA reading. Flying a constant PA doesn’t necessarily keep you at a constant GPS altitude.

Just curious, but isn’t gps altitude HAE?

Do FAA computers convert HAE to pressure altitude?

That seems to allow room for some error, given the number of variables involved in a PA reading. Flying a constant PA doesn’t necessarily keep you at a constant GPS altitude.