Air/Fuel Ratio Display

Great article on air/fuel ratio monitoring in the March 2019 issue. Is there a smaller version of the display unit available? Like the author, my panel is crowded, but I need to fit the unit into the panel somewhere.

—Jim Wright

Reinhard Metz responds: Unfortunately, I don’t know of any smaller units. In fact, most others are round displays, even bigger. This Ballenger unit is actually manageable, but was still too big for my liking. What I did, to some degree enabled by my being an electrical engineer, was to make a smaller display and connect it to the Ballenger unit, which is now buried in the back of my panel. This is relatively easy to do since the unit has a very straightforward industry-standard seven-segment LED display module that is available in a variety of sizes. So, I opened my unit up (voiding any warranty, but I’m OK with that), wired my smaller module in, and disabled their LED module. If you are inclined to do the same, it does require some careful circuit board trace cutting and soldering, an 11-lead cable, and then making up some kind of mounting and red clear plastic overlay. I still have not added auto dimming to the display, which will be useful as well.

Primer Switch Problem

Error Chain: Primed for a Problem” [April 2019] was a very good article. I agree with the author that the best fix was to replace the primer switch with a spring-loaded one.

Another thing that can be done with most glass panels is to have an indication on the screen when the fuel pump or primer is on. I have a Garmin G3X Touch in my IO-240-powered Kitfox that has multiple inputs for warnings, including four programmable ones. I have used the programmable inputs for “Starter,” “Fuel Pump,” “Battery” (for the EarthX battery warning), and “Alt Off” (if the B&C alternator trips off). These warnings are cheap insurance. Besides human errors, switches and solenoids can stick in the on position, and these warnings could save your bacon someday.

I have personally experienced a starter that didn’t disengage in a Cessna 206, and it destroyed the starter. Now I have a warning on my Kitfox to show if the starter were ever to stay engaged. The first thing I check after an engine start is “Starter Warning—Off.” I also confirm that the boost pump is off, both with the the G3X warning and the physical position of the switch.

You don’t need to have a glass panel to do this. You can install warning lights with something like bright LED lights to create an annunciator light or panel.

—Phil Nelson

Project Management

I’ve been using scheduling software since 1982, but due to what has probably been an extended period of locking up that portion of my brain, I hadn’t thought to apply it to building an E/A-B. After reading “Project Management for Builders” [June 2017] and preferring to spend my resources on flying hardware, I found ProjectLibre, an open source project scheduling program very similar in functionality to Microsoft Project, for those of you familiar with it.

—Alan Gideon


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