"Be going to" vs "would"

We use "would" when we talk about a simple statement of future fact, a voluntary action or express a promise in the past.

Past:  I will bring some wine to dinner
Present:  I would bring some wine to dinner.

Past:  I will send you the information    
Present:  I would send you the information.

Past:   I will call you when I arrive
Present:   I would call you when I arrive.

We use "was/were going to" when we had certain knowledge of the futur event (a firm plan or other assuring information)

Past: I am going to fly to Ney York on bussines
Present: I was going to fly to New York on bussines but I got sick.

Past:   I'm going to be an actor when I grow up
Present:   I was going to be an actor when I grown up.