Altimeter Setting at Certain Uncontrolled Airports

[CaptainMD]

Hello PE,

This question arises from the CAT-01 Flight: Non-towered to non-towered. When an airport (L52 or L88) does not report a METAR which provides the altimeter, what is the next best option to choose the altimeter setting for the departing and arriving field?

I read that using the altimeter from the next closest airport or regulated reporting station within 100 nm should be sufficient enough.

When I read sufficient enough, I get worried. So I thought that I would ask my PE friends.

Thanks and sorry if this question has been asked before.

[zerofay32]

On departure, you can use a close by altimeter or just set your Altimeter to read the field elevation. For arrival into the destination, really the only option is to set a nearby setting.

But don't sweat the small stuff. A setting difference of 0.01 is only 10 ft.

RW (or in VR I guess) it's actually pretty easy to visually guess when you are at pattern altitude and being VFR, there is no need for precise altitudes. In the sim it's a bit harder. Once you spend some time in the pattern, you get a good feel of what is should look like and not really even need the altimeter.

[Keith Smith]

If it feels less than precise, that's ok. You're flying VFR. Having a correct altimeter setting is critical when you're in IMC and or you're in airspace where ATC is separating you from other traffic. It's tough to do that if you are not effectively flying the altitudes they assign, however, in both of those cases, ATC will issue you an altimeter setting to begin with.

For your case, it's a 47nm flight, unlikely to result in massive altimeter setting changes. I would simply set the altimeter to match departure field elevation at Oceano, then compare it with the published altimeter setting for SBP (to verify your altimeter is functioning correctly). Then, I'd leave it like that and head to L88. If there was a source of altimeter data significantly closer to L88 than SBP, then I'd probably check that enroute and swap to it.

That's about the best you can do.

[CaptainMD]

Great information regarding this topic. I didn’t want to make my own assumption without checking with this great community.

Thanks for your time Andrew and Keith!