A few months back in this very column, I suggested that pilots should keep a “retired” smart phone in their aircraft as an all-in-one tool for various functions ranging from logbook entries to emergency communication (“The Best Multi-Tool for Your Homebuilt,” May 2022). Now I would like to suggest that your favorite smart device can be just as useful to aircraft builders. There are a variety of apps that can turn your mobile device into a helpful tool for constructing an airplane! They need to be built “straight and level” and also require that angles be measured on various structures.
Specifically, there is a need to utilize tools like levels, protractors and plumb bobs when building an aircraft. A protractor is required when checking deflection of the elevator, ailerons, rudder and flaps. The aircraft designer specifies what the minimum and maximum values are for these. How do you verify the travel of these surfaces? In the “old” days, a mechanical protractor was used to measure the angles achieved. As time progressed, digital levels and digital protractors became available to the builder. Now, this functionality is offered as an app for a smartphone. Typically, these apps are free—if you don’t mind the advertisements that can interrupt your work. For a few dollars more, the ads are removed. There’s also a level as part of the standard Apple OS for iPhone.
The functionality you should investigate in these apps includes a digital level, plumb bob, protractor (angle finder) and ruler. Other functions from related apps include a compass, altimeter and audio meter. It is not my purpose to recommend a specific brand of app. Try them all on for size—usually free. Everyone has their preferences when it comes to features and options. Critical features are included in nearly all of these tools, such as the ability to freeze your current readout with the press of a button. Also, the ability to establish a base angle reference (when not wanting true level) is standard.
Keep in mind that as an aircraft builder you will have other needs for these types of tools beyond setting and measuring control surface deflections. If you are required to set or measure the wing dihedral, then a good level is needed to get those few degrees on each side. Also, when setting up for weight and balance, it is important to level the aircraft to the designer’s specification. There are many other instances where leveling or angle finding is required when building an aircraft.
The accuracy of these instruments should be understood for best results. It would be a terrible thing to be off when it comes to critical measurements. The good news is that nearly all apps allow you to calibrate your new tool to some known standard. (A good bubble level for a reference is better than nothing!) The other odd issue I have noticed is that you need to be aware of any protrusions from your smartphone (like volume buttons, etc.) that are exaggerated by a protective case you may be using. The edge of your device is generally what is used to align it to the work that is being measured. I always take my phone out of the case so that I obtain a better flat edge. This situation will be self-evident when you first try your new electronic tool.
Search your app store using terms like “level” and “protractor” to find the apps that you should evaluate. Lots of choices will result and you should experiment, explore and enjoy some really amazing capabilities you may not have been aware of. On the level—plane and simple.