Switch it Up

So for the time being I've switched off from the Navajo to fly the 206 for a few days while our regular 206 pilot is on vacation.  The 206 was just coming out of a 100 hr inspection in Gander, and the Navajo was just heading up to Gander for its 100 hr inspection, so I hitched a ride with my AME co-worker.  It was a pleasant 1 hr flight that would otherwise have been a 6 hour drive for me if the timing didn't work out perfectly like it did.

The job we have here for the 206 is only a tiny little one-flight'er.  Logistically speaking things have gone fairly smoothly so far.  My operator arrived, and by the next day the weather cleared up enough for us to get an FOM in.  The FOM was a pass on the first try fortunately, and by day 2 despite a little bit of bad weather in the morning we were airborne by 10:30 to go get the one and only survey flight done.  Five hours later, we touch back down in Gander - done and done.  While it was all well and good logistically speaking - not so much for my operator.  It must have been something he ate (or maybe my flying?) but he was sick the whole flight.  Not much fun for him, but he's a trooper, rather than wanting to go home, he toughed it out for the whole 5 hours and we got the job done.

The flight went by fairly fast for me.  The survey lines are quite short, so the constant turns keep me busy, and it was interesting scenery.  The north end of the block contained a lake that was very much cottage country.  I flew over a couple sitting out on the end of their dock enjoying the last sliver of summer.  Each time I went over they waved.  They seemed to enjoy the show, which is a change from our experience in Ireland where we had to deal with numerous complaints.

I forgot how sloppy that airplane is compared to the Navajo, or anything else really.  I guess all 206's are like that though.  In a previous post a few years ago I described a different 206 I flew as feeling like a "flying contraption" rather than a well refined airplane - I'd still stand by that statement.  It doesn't feel crisp at all like the low wing Pipers do.  Oh well, at least it looks good.  This spring it got a beautiful fancy new paint job which is a nice change from the stripped down bare metal fuselage is sported for a few years.

I'm glad this is a small job.  This Gander airport is ridiculous for general aviation.  The Shell FBO where we are parked does not have ground side access, so every time we want to go out to our airplane we have to call them, and then wait for them to come to the gate, let us in, and then escort us in our car over to the building.  It would drive me crazy if we had to do this for weeks on end for a large job.

That was yesterday.  Today we're waiting around for approval from our geophysicist to demobilize, or rather mobilize to our next job - in Wabush.  Unfortunately we're having issues booking a hotel room... apparently they always fill up during the week due to mining crews... not quite sure how we're going to work this one out...

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.

Mountain Turbulence

If there's one thing a survey pilot learns about first hand more than probably any other kind of pilot its turbulence associated with mountains.  The diagram below pretty much explains it better than I can.  Note there is turbulent air on both sides of the mountain, but the windward side tends to be updrafts, whereas the leeward side tends to be downdrafts.

The only time MOST pilots would experience this phenomenon is when flying over large mountains in strong winds, simply because there is usually no reason for the flight profile to cross over hills/mountains at a height of less than 1000 ft, and it takes a larger mountain and stronger winds for the turbulence to be felt that high above the peak.

For survey pilots, often our flight profile takes us over the peak as low as 100 ft above the surface.  In fact high peaks are often when we fly the lowest.  It doesn't take a large mountain to generate severe turbulence and down-drafts that close to the terrain, and that height leaves little margin to react to the down-draft or manoeuvre out of it, so its important that we always remain very aware of wind conditions, especially on the leeward side.  It wouldn't take much for a down-draft to drive us into the hill-side when we're climbing up the leeward side of a mountain.  Climbing up the windward side can also create different problems of an illusionary nature, simply because climbing the windward side means you're flying downwind, which can decrease your climb angle and carry you into the mountain even though it looks like you should clear it - but that's a discussion for another day.

I remember I cautioned one of our pilots (who shall remain nameless) about mountain flying once.  He was not new to being a pilot, in fact has more hours then me, but completely green to low level survey.  He dismissed my words confidently saying that he would be concerned about weather conditions, but not about terrain that doesn't move.  His statement exposed his inexperience with flying close to the ground and revealed a little of his ego in general, but it wouldn't have been fruitful for me to do anything but leave it at that.

This mountain turbulence has been a reoccurring issue for us throughout our time in Newfoundland because the terrain rises sharply to almost 1500 ft ASL right out of the ocean, and even though our survey block is mostly offshore, it overlaps land by about 3-5 km, so every line we fly involves either climbing up over the shoreline hills, or descending over it.  Today was no exception.  The weather was kind of a scuzzy overcast of about 4-5000 ft, isolated rain-showers, and a strong but mainly steady wind (at least over the water).  We're at a section of the block where the terrain rises out of a valley very steeply - almost vertically for 1800 ft.  Its quite a stunning vista actually, but not so much when you're bouncing around trying to keep the airplane level and on line.  It was once of those days where you pull your seatbelt as tight as it can go.

I did not take the pictures below, but I found them from a google search on a hiking website - they are the exact area we flew over today, right down to the canyon lake (bottom photo) which we ended up flying right over.  Anyone who can guess the exact area based on the pictures gets 100 points, which are redeemable towards recognition as a Canadian traveller and bragging rights.

 

So back to the story.  As we near the end of our line the mountain ridge looms in our windscreen.  Keeping the airplane on a laser-accurate flight line doesn't take the concentration that it used to when I first started flying survey, which is good because I can devote more of my cognitive abilities to deciding how to handle the approaching mountain.  Our grid actually ends about 3 km before the mountains in the top picture begin, which means we're tasked with either 1) making our turn-around inside a 3 km area, 2) climbing above the mountains and making our turn-around above them, or 3) crashing into the side of them.  Option 3 would make for a bad day, option 1 would be possible but very risky due to requiring high bank angles close to a wall of mountains, and in turbulence even, which is exactly when you DON'T want to be banking hard, which really only leaves option 2.

So today we were left only with the option to climb over the mountains to make our turn.  Under normal conditions I could have continued a straight over climb and clear the peak by a couple hundred feet, but in today's conditions that's not much margin to leave in case we experienced a heavy down-draft.  I elect to turn left and climb parallel to the hills until we're well clear of the peak, and then begin our right turn over the ridge and follow it back to re-intercept our line descending down over the ridge.  Its not the most time-efficient turn, but its the safest action.  Sure enough as I was paralleling the ridge on my way back to the line we experienced a small but steady down-draft right at the crest of the ridge.  In level flight at higher airspeeds it didn't end up being a factor and the airplane could handle it no problem, but encountered during the climb when airspeed is slow and the airplane is already approaching the maximum climb performance, it might have been a little hairier.

Luckily we were only faced with that condition for only the last 3 lines of the flight.  These ones in particular are short lines, and making efficient turns can really cut down on unproductive flight time.  Hopefully the winds on our next flight will be a little calmer, or in a different direction and we won't have to go out of our way so much.