Not all airportscan be used as an alternate,why?
thank you

 

For the same reasons you couldn't land at your primary (plus a few extra)
Weather is below mins
Winds are out of limits
Radar is out of service
No weather reporting capability (or it breaks)
Approach requires DME and the DME is out of service
etc...

Basically if the airport is not equipped for IFR, you can't file there as an alternate in IFR (in IMC).

 

I think it's usually because the airport doesn't have a TAF report.

 

To be as useful as an alternate in really poor weather conditions, the alternate should have an approach with minimums equal or lower than the primary choice. They often do not, especially for general aviation aircraft destined to remote locations. You can't reasonably expect to go missed from the primary ILS to find another one a short distance away. A possible caveat to this nowadays would be GPS-WAAS approaches which are getting pretty common. They are as good as ILS and small airports often have them.

 

I think I heard somewhere there has to be a certified weather observer there for the airport to be approved for use as an alternate. Might be wrong, just remember hearing it.

 

It's been a while since I've read this stuff, but from what I can remember the airports primary NAVAID must also be monitored at all times for the airport to be used as an alternate.

 

Must have an approach other than one releying on GPS Nav.

 

As in ATIS, AWOS, ASOS...yes, because you don't want to press on in the soup to an alternate that is worse and no one knows it.

 

Papacharlie,

BlueSkiesAhead I think answered the question you were asking (not trying to offend the others-truly). The NAVAID needs to be monitored. I wish I had a reference to give you, but I'm serving in a sandy place shall we say, away from most of my flying books for the time being.

I remember being confused by this too, and my CFII didn't address this for me. So look in the upper left hand corner of your approach plate, and if there is an A inside the black triangle with an N/A it means that approach can't be used as an alternate at all-good wx forecasted or not.

You'd be surprised at some of the places that are unmonitored. A common airport I fly in and out of is Class D with Regional aircarrier service, but all it's approaches are considered 'unmonitored' so no filing these approaches as an alternate.

First make sure there is no N/A for that approach, then think about the weather mins e.g., 800-2 or 600-2 (or any nonstandard mins), how the winds will make or break a given approach, and having an approach other than just GPS.

Does that help?

 

A/NA , at least on gov. approach plates, means that the navaid is unmonitored and/or there is no weather reporting capabilities...