It is somewhat difficult to explain why human factors is important to flight test professionals–FTEs and experimental test pilots–and why it is important to the aerospace engineers that design airplanes in the first place. I want to use the ubiquitous ipod to illustrate one very small facet of the subject and its importance.
Let’s start with the original ipod touch. Look closely at the volume switch on the left side. I would describe it as a rocker switch–a single switch that pivots about a central fulcrum, kind of like a seesaw.
We use the same switch to turn the volume up or down. If I want to adjust the volume while I am running or driving, it is quite easy to do–all I have to do is feel along the edge of the ipod with my hand, without looking, until I find the switch. If I accidentally turn it down instead of up, this is easy to reverse.
Pressing the upper part of the switch turns the volume up and vice versa, so when we are using the switch while doing other things, it takes very little extra concentration to make it work as we think it should function.
This phrase is key to understanding human factors. Additionally, there might be other reasons to consider this design, e.g., fewer parts, only one hole in the case required, etc.
Now compare that to the volume controls on the second generation ipod touch pictured below. Here you can see two independent pushbuttons.
I can’t tell you the number of times that the audio in a Dave Ramsey podcast has changed from reasonable to really loud, forcing me to quickly change the volume. In my hurry, I pressed the first volume switch I could find and blasted my eardrums even more.
Several times, this has occurred when my ipod was in my a running wallet clipped to my waistband. In that moment, I don’t know the orientation of the ipod, so I cannot quickly reverse my action. My first instinct might be to move my finger left, finding nothing but cold metal instead of the down volume button.
I’ve found that my hand is not quite sensitive enough to detect the edges of the switch or the space in between the buttons when I am busy doing other things, like running or driving.
That simple illustration explains why I prefer the design of the rocker switch to the independent pushbuttons. You can see that it ties together the function of the control and the context in which the control is used. Add to these two the way the brain thinks, a field we know much about and still have much more to learn.
Together you can begin to see why human factors is taught to flight test engineers and test pilots at test pilot schools worldwide–it is the job of these specialists to make sure that the pilot flying the line does not have to think hard about the controls he uses, especially when time is critical and errors are deadly.
Want to know more about human factors? Here are 10 links to videos, references, photos, and stories about human factors and flight test.
Don’t just imagine your dreams–explore them, because we need you. The aerospace industry needs innovators. The flight test community is looking for the next Neil Armstrong, and that’s what this column is about, helping you take that next small step.
Thanks for reading Launch Your Flight Test Career #15. Send a message to @FlightTestFact on Twitter to ask questions about launching your flight test career.