| Is AM used in Aircraft these days? I picked up an Attack 4 cheap | and could use it in my trainer if it's appropriate. I bought the kit for | the servos and batteries so the Radio and receiver are extra. Don't need | to use it unless it's ok to do so.
As Ed said, AM is still used and works fine. FM gives you better range, but AM still lets you go further than you can see the plane. I guess that FM should reject interference better, but in practice I haven't seen any real difference.
Many of the low end radios, especially on the 27 mhz and 75 mhz bands, are AM. They're still making lots of them today (mostly for cars, but there's some for planes too, especially for small park fliers.)
With any old radio, there's the danger that it's not narrowband, but I think all the Attack 4's are. There's probably a gold AMA sticker on the back -- if so, you're fine. If not, you might want to ask Futaba about it.
You say it's for use in a trainer? I have an Attack 4 radio, and I don't think it has a buddy box connector. So if that's your plan, forget it. And even if it does have a buddy box connector, it won't work with an FM radio -- you'll need to use another AM Futaba radio for the buddy box.
They haven't been made in a while, so the batteries are probably dead or dying. Replace them, or at least cycle them and see what kind of capacity they've got left.