Coming up to an instrument flying exam, or maybe you just want to brush up on your point to point navigation? Well, this is the app for you. HSI is a VOR/TACAN/LOC/NDB navigational training tool that you can take in your pocket. Initially developed for Australian advanced flying training, HSI will help you get your head around concepts like arcing and point to point navigation by providing an inexpensive, hassle free way to practice them to your hearts content, wherever you may be.