RE: blizzard landing aid
Are you talking about using the ailerons as air brakes or spoilers?
If the DX5 is capable, there should be a listing in the mixes to program it in. Pretty simple to do. Works off a separate switch on your tx. You go in and slave one channel to a master channel, which means you need the ailerons on seperate channels on your receiver, no using a Y cable to hook up the ailerons.
If you have em Y'd together and you have an extra channel on your rx you're good to go. You'll have to go into the programming and master one channel, and slave the second channel to work the ailerons.
For the spoilers/airbrakes, you follow the same set up on master / slave if needed, or if the mix is already in there, you just assign the channels you are using for the ailerons.
Adjust the amount of throw on the master channel, then switch to the slave and adjust it the same. Assign a switch to operate it.
If you don't have an amount of throw from Multiplex, it's best to start out low, and try it out at least three mistakes high. See how it reacts, and adjust from there.