[rosrun] Couldn't find executable named drone_gui

[paul3333]

I am using Ubuntu 14 with Indigo and made a catkin workspace, copied tum_ardrone in catkin_ws/src, ran rosupdate installed tum_ardrone as instructed in the README and then ran catkin_make.
I implemented the catkin_make command, but when I run the command rosrun tum_ardrone drone_gui, I get the following error:

ERROR: [rosrun] Couldn't find executable named drone_gui

Same happens for "rosrun tum_ardrone drone_stateestimation" and "rosrun tum_ardrone drone_autopilot" with respective errors.

The also could not find the according files in the installation folders.

Any help would be greatly appreciated!
Thanks,