This app was mentioned in 1 comment, with an average of 1.00 upvote
It's not too bad, as a sim it's more of a game but if you are limited to Android, it's cool.
There are other sims as well, while Leo's sim lacks Multirotors, the helis will help a great deal for flying multis however.
https://play.google.com/store/apps/details?id=leofs.android.free&hl=en
The desktop sims are the best as you can use your real controller and most have Multis these days, RealFlight is very good but not the cheapest.