Unity Jet Wing Animations! Help!

Hello,

I am currently creating a small jet simulator and wing animations. I created all the animations in Blender and exported them into unity using FBX. All of the single animations work such as Up, Down, RollLeft, and RollRight; yet when I try to blend two of the animations together they only play half way, and are very glitchy. I will attach my current script in hope of some help. Thanks!

       (Note: I am trying to get the RollLeft animation and the Down animation to play at the same time.)

function Update () {

 if ( Input.GetKeyDown("a") )
 {
 
     animation.Play("Left");
     
 }    
 
 if ( Input.GetKeyDown("a") && Input.GetKey("w") || Input.GetKeyDown("w") && Input.GetKey("a") )
 {
 
     animation.Play("Left"); 
     animation.Blend("Down");
     animation["Down"].layer=2;
     animation["Down"].weight=0.5;
     
     
 }
 }