How a little HP-50g program mutated into an iPhone app


The program was developed by a pilot to do refueling calculations; the pilot was an engineer, and an experienced 48/49/50 user.

He generalized the program for other aircraft, taught himself programming for iOS, and ended up with a nice-looking application called Aviofuel.

Perhaps pilots and others familiar with such matters (and even with this particular app) will have comments. I think it's a nice and relevant story.

The mutation story is here:

The app is described here:


Very nice app, well done. This gives me something to look forward to do on lunch breaks this week: find out what these terms mean.


Very Neat. Thanks for sharing.

I am on a similar quest but only at the beginning of my App. We already had a mac book so that was not the hurdle is would be for many. Objective C is a bit strange for someone like me out of programming in C for a long time but the basic stuff is ok.

What I really need to find a way to do is mimic the multiple equation solver of the 50g which is no small task. All my equations will have closed form solutions so I don't have to do any iteration but just thinking of parsing and re-arranging equations programaticaly is a little daunting. But, I'm starting a chunk at a time with it and it really is pretty fun when I get the time to work on it.


Hello, I'm the AvioFuel developer.

I'm glad you liked the 'mutation' story. Thanks a lot for your comments.

I've been using the HP48/49/50 all these years for many pilot-related tasks, such as aircraft performance calculations, flight-time logging, flight planning, weight&balance calculations, and so on.

Nowadays I use the iPhone and the iPad. I still love my 50g, though. In fact, I use it a lot for app development.

If anyone here wants to play with AvioFuel, I can provide Promo Codes to download the app free of charge from the App Store. Feel free to contact me.



I spent my free time during the following months learning as much as could about Cocoa and Obj-C, reading blogs, tutorials, watching videos and reading books. I didn't even plan to release anything on the App Store. All I wanted was to take advantage of this little magical device for my own needs, to solve my own problems.

This is exactly where I am right now. My son keeps asking me if I'm still working on the that "app thing". I'm sure I have months and months ahead of me. The developer information online from Apple is pretty amazing but did you find any other resources particularly useful. I have a "theach yourself iPhone App developement in 24 Hours book" but I think it is a version old so I'm looking for other places to turn to for more recent information.

Thanks again for sharing!


The developer information online from Apple is pretty amazing but did you find any other resources particularly useful. I have a "theach yourself iPhone App developement in 24 Hours book" but I think it is a version old so I'm looking for other places to turn to for more recent information.

You can find two great iOS development courses on iTunes, both of them for free:

- Stanford University iPhone/iPad Development Course, by Paul Hegarty. <- This is a must-see. Download the slides from the course site and follow the lectures on iTunes. I learned a lot from this course. Link:

- Madison Technical College Advanced iPhone Development, by Dr. Brad Larson <- Also very good. It dives into more advanced topics. Larson is the author of Molecules and Pi Cubed, two great apps. Link:

Books (You can find most of them on Amazon):


Learning Objective-C on the Mac, by Mark Dalrymple and Scott Knaster -> My first Obj-C book. Great for beginners.

Cocoa Programming for Mac OSX for Dummies, by Erick Tejkowski -> I learned the basics of Cocoa with this one. Very good read, easy to follow.

Beginning iPhone Development, by Dave Mark and Jeff LaMarche -> My first iPhone development book. Very good. Easy read. It gives you a very good foundation.

iPhone App Development: The Missing Manual, by Craig Hockenberry -> It covers the whole app development process, from the beginning to the end. You'll need basic Cocoa Touch and Obj-C knowledge in order to get the most out of it.


Core Animation, by Marcus Zarra and Matt Long -> Teaches you everything about Core Animation on iOS. I strongly recommend it if you wanna give your app a distinctive touch.

Pro Core Data for iOS, by Michael Privat and Robert Warner -> Once you get enough experience with basic iOS development, you'll realize sooner or later that you need to use Core Data for everything but the most basics apps. I found Core Data a bit complicated and obscure at first. This book helped me a lot.

iPhone 3D: Developing Graphical Applications with OpenGL, by Philip Rideout -> If you plan to develop 3D graphics apps (or games), this is a must. It covers OpenGL ES with lots of examples. You'll need a good C++ foundation, though.


There are plenty of great sites about iOS development. I think and are both extremely useful for beginners.

Regards, and happy coding! :-)


Luis Thank you very much! I found out that there are several different Stanford classes in the iTunes store (different semesters). The first one I got was too old. Looks like the latest will require me to update the OS on our mac book pro.

But I hadn't found the Madison Technical College one.

That looks like a great collection of references. I'm already finding I want/need to do things I can't with the standard controls.

Funny you mentioned a good C++ background. I have a mediocre C++ at best :-) I'm old enough to have to take FORTRAN at school and tought myself C and a little C++ over the years.

But strangely enough, I have been developing industrial machinery controls for a long time and the Interface Builder is very much like the programs we use to develop for machinery.

Take Care

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