Winter Surveying

Northern Quebec in late autumn was indeed a bad idea.  We spent over two weeks watching Low pressure system after Low pressure system pass over top of of us.  Rain, freezing rain, snow, winds, low cloud, you name it.  Finally about a week ago things started clearing enough for us to go flying.

These survey blocks are short lines, tightly spaced, in very jagged terrain, and with no drape file.  Very intensive flying.  A drape file is a file that's loaded into our navigation system to give us terrain guidance based on topographical data.  We fly lines in both directions to make a grid, and for data-quality reasons the line intersections between both directions have to cross at the same height.  So to make it easy on us, the drape file is like "draping" a blanket over the hills.  This gives us a vertical flight profile that follows the hilly terrain in a general fashion, crossing the small valleys smoothly and giving us an achievable climb gradient to get up the mountains within the aircraft's performance limitations.  Without drape guidance, we have to estimate ourselves what height we should be at any given time.  With practice and experience it can be done, but it is one more variable to stay on top of.

With the short lines it means we can do upwards of 60 lines every flight, which also means 60 turns.  Turns are similar to an IFR procedure turn - after exiting the block you make a 45° turn away from your next line, wait until you're a certain number of metres away from the line laterally, and then make a 180° back around the other way to intercept the line.  Generally turns take about 2 minutes, but if we're doing 60 turns a flight, for every ten seconds we can shave off in each turn, we can save ourselves 10 minutes over the course of the flight, so in these scenarios its highly beneficial to do what I'm going to call a "performance turn".  With performance turns we accomplish the entire turn in about 1 minute.  This is done by shortening each leg of the turn, and then instead of a 30-35° bank, we're banking as hard as 45-60°.  And we make the timing such that we roll out level on-line only seconds before entering the grid.  Its half science, half art to get the turns and timing perfect enough that you're not wasting time rolling out onto the line too far back, but not so close that you risk entering the block before you're lined up.  Its all based on hitting your key points:  At 90° to my line I should be at 900 metres cross-track - if I'm less I need to pull harder, more and I can relax the turn a bit.  60° to my line - 500 metres, 30° - 200 metres, and if I hit 20° and 100 metres I can start rolling out smoothly and I should end up wings level within +/- 30 metres of my line.  From there it takes only a few more seconds to fine tune it to less than a couple metres.  No more than a minute from exiting the grid to entering again on the next line.  Things happen fast.  This is high workload flying indeed.

Our day starts long before this however.  We leave our hotel rooms at 05:45 AM, its still dark.  We have limited daylight and we're trying to make use of the good weather and get two flights in today, but everything has to go perfectly - any delays and taking off for a second flight won't be practical.  We're shooting to be airborne by first light.  We have to fuel the airplane, brush off the 4 inches of snow that accumulated last night, unplug the two engine heaters and 1 cabin heaters and pull off the engine blankets, and then start up our base station so its logging atmospheric magnetic data (a requirement for a survey flight).

Our fuel drums are stuck in a pile of ice and snow.  We work away in the dark.  It takes two of us to wrestle each of the four 300 lb steel barrels out of the snow and get them on the ramp where we can roll them over to the airplane.  Even rolling them isn't easy today.  Two of the drums are dented so badly they don't roll very well.  I'm exhausted by the time we get them to the airplane, and my throat is hoarse from the exertion and sucking in -10° C air.  My foot also hurts - in the process of standing one of the drums up, I let it land on my foot.  I'm okay, but I'm already a little bit grumpy in the morning as it is, dropping a 300 lb drum on my foot doesn't help my mood.

I help get my colleague set up to fuel out of the first drum, and I start to brush the snow off the airplane. Its been cold enough that the snow easily brushes off, thank goodness.  The windshield is a different story.  We have to keep a space heater running inside the cabin to keep the survey gear warm, and as a result the snow that has fallen on the windshield has partially melted, and then frozen solid to the window.  Unlike a car windshield, our airplane windshield is plexi-glass, so we can't just scrape it off or we'll scratch it all up.  I climb into the cabin and position the space heater up at the front, pointing at the window.  Back to brushing.

Finally we're fuelled and the airplane is clean - off we go.  We're behind schedule now and the sky is bright morning, but we're airborne, the weather is clear, and the airplane is climbing like a homesick angel in the cold air.  Up until now the few flights we have been able to do have been through snow showers and moderate turbulence.  The kind of turbulence where you have to brace your palm against the throttle quadrant and adjust the leavers by pushing them at the base, lest a big bump causes you to yank on them.  Its a little bit smoother today however.

Three hours later.  We're churning out survey lines like a well-oiled machine.  I'm pulling hard through a "performance turn".  On this line in particular, in addition to watching the numbers on my digital display tick away like a slot machine on steroids and making sure I hit my key points, my neck cranes just a bit as I watch out my window.  There's a cliff scrolling by my windscreen from top to bottom as I crank the airplane around in a steep turn.  Its just a little cliff, peaking about 100' below my altitude so we'd clear it anyway if it wasn't already outside my turning radius, but its still an obstacle to keep in sight.

Rolling out on-line and entering the block, there's a small cliff we dive over and then skim a small lake at 230' agl.  Its starting to freeze over.  From there its up the side of a rocky 1000' mountain.  The pine trees start to thin out about halfway up as the soil gives way to exposed windswept rock.  Everything is covered in a blanket of white.  If I looked down to see some chipmunks and reindeer throwing tinsel on a tree I wouldn't bat an eye.  Most of the mountain is on my left side.  To my right I look down to the valley, spotted with lakes and carpeted by pine.  I glance at the mountain to my left every few seconds - this time not because its a hazard, but because I have remember/imagine what height we were at when we came cruising down the side of it on the lines running perpendicular to the ones we're flying now.  Remember we have to intersect lines at the same height, and we're working without a drape.

In the past my colleague and I have been known to engage in some good natured debating over what the proper height should be.  We have differing views on how a lot of things should be done actually, but we handle it in a humourous manor so in fact we get along quite well.  Its almost tradition now for whoever is riding shotgun at any particular moment to engage in some armchair aviating over what the proper drape height should be.  A guy's gotta get his two cents in.  Not much of that today though, we're both pretty busy and in the groove, not much talking is going on.

Four hours later.  We finish our last line, this block is finished, and our fuel will be running low soon, its time to head back.  There's more blocks to do however, and we're still entertaining the thought of getting two flights in.  We land, relieve ourselves, grab something to eat, and get right back to work fueling again.  This time our fuel drums are not only stuck in the snow, they're frozen solid to the ground under almost an inch of ice.  After much kicking, prying, chipping, and grunting we get them free, but that delay was the nail in the coffin for flight number 2.  By the time we get them free enough to roll over to the airplane we should have been almost ready to start the engines.  Time to call it a day.