Doch, doch wir verstehen uns schon!
Let me try this:
Aviatik is pronounced with a short A. Just A. Short. Ultra short!
Just a moment! Or do you mean the middle a?
Aviaaahtick. The middle a is long, the first a is short! The stress is on the second syllable!
Ä is a umlaut. It is not pronounced like A short/long or whatever. Ä is Ä. Like 'ey'. Short 'ey'.
Yours,
Hans