I was on my way home tonight and had an interesting experience that I thought I would share.
I fly often between Springfield, Ohio and Chicago, Illinois. This is a pretty regular trip and I am familiar with how much fuel I can depart with out of Springfield, make the round trip to Chicago and still have plenty of fuel by the time I return. In fact, I can tell you that if I top off in Springfield before I leave, I’ll land with about 1000-1200 lbs of fuel when I land (depending on routing and the wind).
Well, I was about half way home on the last leg of this familiar round trip, when I looked up and noticed that something wasn’t making sense. Instead of the 1000 pounds I normally land with, the on-board FMS was calculating I would only have 600 lbs. It was also calculating nearly an hour of flight time left, when it should have been closer to 30 minutes. A little more investigating revealed that it was calculating the flight distance at 433 NM when the flight is only about 260 miles. Something wasn’t making sense.
It would have been easy at this point, to blow it off completely. To mutter something like, “I don’t know what its doing, hopefully it’ll fix itself before the next flight” or something along those lines. But it really bugged me that it wasn’t right and I kept looking for the answer.
Finally, after about 10 minutes of jogging through every single page and option, I found it. I had mistakenly selected the approach for a runway at my departure airport instead of at my arrival airport. In short, the FMS thought I was flying to my destination and then returning BACK to my departure airport to shoot the visual approach. To complicate matters further, I realized the cause of my mistake was easy to make, because both airports have a similar runway (Rwy 24). I had selected the visual approach for Rwy 24, not knowing I had selected it for the airport I had just departed instead of at my destination.
Once I selected the visual approach at the correct airport (my destination), the FMS “magically” corrected itself and showed both the appropriate time left, total distance and correct fuel load at landing.
After I finished laughing at myself, I realized that there was a VERY important lesson to be learned here. “If it doesn’t seem right, it probably isn’t.” I thought of the first lesson that I had learned in 8th grade computer class: GIGO, Garbage In – Garbage Out. Now I’m not saying, computers don’t act up on their own (I do own a PC) but it is important that we don’t blow off miscalculations and errors as simply computer error because more often than not, the error is ours alone.
Fly Safe (and look out for those operator errors)