Master-Detail-Detail View for Mobile

I'm designing a mobile app that uses a master-detail-detail model. The first screen is a list of records from table A. The user can select on record and show the details of that record. Then there is a list of sub records from table B where the user can also select one record to have a look at the details.

Now for a web application the user interface isn't too difficult, but I'm not sure whether the design on the very limited space of a mobile phone is suitable. There are two navigation bars at the same time. One for level 1 (Table A) and one for level 2 (Table B).

Is this a good design or how could this be improved?

Here's a sketch: