Is it necessary learn autocad before catia?

No 

You can beginning with catia without learning acad

Let me put it this way ... when I took CATIA it been a pre-requisite to know AutoCAD3 D

I personally would not have needed AutoCAD3D, since I already knew how to draw and why it is done in a certain way... meaning the concept of Isometric drawing in a2 D environment....

Also remember CATIA is totally different than drawing with AutoCAD...

I have not used CATIA for architectural drawings ... thought it is more used for the aircraft and car manufacturers for mechanical applications ... 

Yes. By practicing autocad clear the concept of 2D drawing & Drafting. catia is fully parametric software.

No, you can go for Catia without learning Autocad as both are not inter-related

thank you for invitation

I think yes

It is not necessary if you learn and practice catia properly but  if you know autocad then it is good for you to improve your skill.

For being good at concept and having confidence on making Sketch.

We need to learn Autocad firstly.

First of all divide the objectives to the staffs according to their ability and make it as a team work. After completing the team objective make understand the staff about their up's and down's in a comfortable manner. So that they can try to improve their performance in the coming objectives  

You need to have basic understanding of how to use AutoCAD

It is good for learning basic concepts but there are no similarities between AutoCAD and CATIA.

You can learn CATIA without learning AutoCAD.

Not at all, catia and autocad are for different purposes, a knowledge of autocad would just help you familiarise with the computer interface which is again a bit different in catia.

I learnt catia before autocad, there were no hassles involved.

Go for catia without worrying.