Welcome to the Show

FOMs.  Every geophysical survey pilot's dread.  FOM stands for Figure of Merit.  Its a technical term for what is basically a flight to calibrate the data acquisition computer for the magnetic sensors.  Every manoeuvre of the airplane causes reading error in the magnetic sensors, so the Figure of Merit flight is the way we teach the computer to recognize the manoeuvres of the airplane and remove them from the equation, and then prove that the calibration was successful.  It involves flying a a box of 4 headings (usually N, S, E and W) and executing a number of pitch, roll and yaw manoeuvres to exacting standards.  The computer then learns to recognize these manoeuvres and remove them from the equation.  We then fly a second box doing essentially the same thing.  It is this second box that we call the Figure of Merit, which is the proof that the calibration was successful.

That's the theory.  Its always a highly delicate procedure requiring a high degree of precision from the pilots.  After that we land and then hand the data over to our processor/geophysicist who then determines if the calibration was successful to the degree that is stated in the job contract.  Even if we as the pilots do a good job flying the FOM, getting an acceptable result can still be a shot in the dark at times, and its not uncommon to have our first attempt fail for reasons that no one can explain.  Its a highly complex, mysterious algorithm the computer uses to compute the calibration values, and sometimes it just plain doesn't work very well in the real world.  To make matters worse, when its a government contract (like this one) the calibration standards are even higher, requiring a result value that is so demanding it is essentially random chance as to whether or not the computer will achieve it, even if all the conditions are perfect.

Ask how it all works and you'll see heads shake and shoulders shrug and hear words like "voodoo" and "magic", even from the experts.  One of our processors has started referring to it as "FOM theatre with Chad and Charles (other pilot)", because it always seems like a big show and no one knows how its going to end or when its going to be over.

Every survey pilot dreads them.  The manoeuvres themselves can be uncomfortable, like a nauseating roller-coaster ride, especially for the operators who are just the helpless passengers along for the ride.  I once did 3 FOMs in 1 day, in two different airplanes.  Even I could feel a tinge of nausea, and I DON'T get motion sick - EVER.  And then there's the fact that it requires such focus from the pilot to perform the manoeuvres correctly and with enough precision.  The whole nerve racking process of doing a flight and then waiting around to hear if the results passed or not can bring even the most steely eyed and confident pilots to their knees quivering with doubts about their ability as an airman and a survey pilot.  Its like taking an exam and having no idea how you did until you get your marks back.  Usually after we complete the FOM and are on our way back to land, the pilot and operator try to offer words of encouragement, "I think that was good, don't you?"

"Ya I'd say so, it looked good to me..."

But really we have no idea.  Not until we get the data back to the processor and he has time to look it over and do the math.  FOM theatre.  Its time.  Welcome to the show, and please take your seat.