Wednesday, July 09, 2008

I Pronounce Me Here

They've been telling me we are going to Nevada next. I was given a day off in which I didn't do much but swim laps in the (big! outdoor!) hotel pool, and draft flight plans for Reno and Las Vegas. There are other places in Nevada, but I figure if I know how to get to the big ones, I'll be able to figure out the way to Winnemucca. (The problem with that would be pronouncing it when I get there. Did you know I managed to pronounce Birmingham wrong!) And then they told me to fly to Salt Lake City. At least I can pronounce that.

That meant a two leg trip, one flat, one with mountains. The flat leg of the trip was the more difficult one, however, because the flat bits of the US are all about thunderstorms this time of year, and these ones had SIGMETs for hail. Unfortunately I can't find the bit of paper on which I scribbled that SIGMET because it didn't just slap down the symbol GR for hail, it spelled out the diameter in inches of the expected hail, and I don't want to exaggerate when I report the size, because it was a number that was sufficiently foreboding without exaggeration, but I can't remember it. It's a little like if someone told you there was a dangerous, angry poisonous spider in your bed, you might forget exactly how big they said it was. Most thunderstorms do have hail; it just doesn't always reach the ground. And thunderstorms have enough nasty components without hail. But when you consider that hail can be thrown out of the storm ten miles away from where the storm seems to be, and hail like that could damage my aircraft even without gusty winds, downdraughts and severe turbulence, you can see that was a no go. The thunderstorms are not air mass thunderstorms, formed pretty much daily over large flat hot areas with available water, but frontal thunderstorms. They are being caused by a fast-moving cold front that is lifting the hot moist air. That makes for a long, impassable line of storms. I have to go around. Not too far around, however, because there are air mass thunderstorms in the area, already topped to 60,000', about as high as they go at this latitude, to the south, and they are moving north. I'm running the gauntlet between two storm areas.

I pick some VORs as follow-the-dots points for a routing and file my flight plan, IFR because there's a lot of moisture associated with the cold front, even away from the convective areas. I took a few pictures of distant convective cloud, but they aren't very impressive because there's no sense of scale.

The flight goes well. The air traffic controllers are friendly and cooperative, offering me more direct routings and giving me information about the convection and rainfall they can see on their scopes. I cut the corner a little on my planned routing. It was conservative, allowing for the front to slow down, but it moved as forecast and I'm able to curl in behind it, going north in the wake of the storms. There is a lot of moisture left and one controller calls me to tell me he sees about fifty miles of light precipitation ahead on my route. I acknowledge that, I've just entered cloud, and tell him that it is smooth. He then comes right back and says "and then the fifty miles after that is moderate precipitation, let me know if you need any deviations." He must be practicing his comedy routine. I found it really funny that he told me about the light stuff, waited for my response and then told me there was heavier stuff to follow. He was pretty much exactly right, then the clouds thinned rapidly after the hundred miles had passed and the skies were clear for my landing in the middle of the country.

The FBO lends me a courtesy car that is parked on the inside of the security gate. I drive up to the gate, pick up a phone and tell them I want out. The stop sign immediately after the gate says not STOP but STOP HERE AND WAIT UNTIL GATE HAS CLOSED COMPLETELY. It's a smaller point size than your regular stop sign. Gas, washroom, food, weather and go: VFR this time because this leg will put me over my eight hours max IFR, and the weather is clear all the way to Salt Lake City. Yippee-kay-yay! On takeoff I'm cleared on course and to me requested altitude right away.

I put on the autopilot while I check out the scenery. The land is still flat, but not level. It's sloping up towards the continental divide. The GPS tells me that I'm crossing the Canadian River. I wonder what's Canadian about it. There's a North Canadian River, too. I have a notebook in which I write down things I want to blog about later, and I see that last month I crossed the Choctawhatchee River. You can't make up names like that.

I've been flying westbound at 8500' watching the ground get closer as it smoothly slopes up. I've also been kicked by light turbulence, chop as I call it in the PIREP I file after 50 miles of it. I wouldn't ordinarily file a PIREP for turbulence that was only light: I'm doing it because there was an AIRMET for moderate turbulence along my route. My PIREP might help the forecasters, or help someone make a decision to fly.

I could possibly reduce the turbulence by climbing higher, but I don't really want to. Eventually the time comes, however, to suck it up and climb. The upsucking is quite literal. Although US rules allow a pilot to fly without oxygen for unlimited periods up to 12,500, I have to obey the more stringent Canadian ones and suck oxygen through a tube for the entire duration over 10,000', if I'm to be there for more than 30 minutes. I can go high enough to go straight up and over all the mountains, but the power of one engine alone wouldn't give me a good safety margin if the other engine quit. I would keep flying on one, but I would drift down, and there might be no escape, no where to drift to, over these mountains. I will follow the line of a pass rather than skimming over the peaks. This route will also give me a better approach into Salt Lake than trying to dive bomb the city.

At this time let it be said that I hate this oxygen mask. It ought to be cool at fourteen thousand feet above sea level, but the OAT is 12 and with the sun blazing into the cockpit from clear skies it's like a greenhouse in here. Clamping a rubber mask over my nose and mouth does not improve the situation, nor does the transit through plastic hoses and rebreathing bag improve the flavour of the bottled oxygen. It's ironic that up here where the mountain air is probably the freshest in the country, I get to breathe out of a bag.

I also get to talk through a bag, with ATC having trouble understanding my routing because I sound like Darth Vader. I wonder idly if I'm suffering from carbon dioxide poisoning, or just going mad. I should buy one of those ear-clip things to see if I'm sufficiently oxygenated. I wonder if they have to poke you, in order to get to your actual blood. If so, I'd bleed all over it. Or do they just look at the colour of your ear, in which case they wouldn't work on dark-skinned people.

Here's me heading for an invisible pass in the mountains. You can't see it from this angle, but the road goes through it, and so did I. Wow, I didn't notice until I saw these pictures side by side in the preview how much clearer the air is for the mountain picture. The windshield has not been cleaned between the Canadian River picture and this one: it's the same flight.

After the pass the land became flatter, but not much lower. I overflew one ten-thousand foot plateau, wind-packed snow berms still visible along the top. The visibility is decreasing, but this is a good sign when your destination is at a lake. When the drier mountain air gives way to moister, cloudier air, that means you're almost at the lake. I fly into SLC from the south following ATC instructions to overfly the interstate. I've studied the airport diagram ahead of time and based on the ATIS and the runway lengths, I guess that I will be given runway 35 to keep me out of the way of the faster airliners. I can see the airport ahead. The freeway passes to the east of it. The controller tells me to follow the freeway and maintain 6000'. He will turn me for the runway about three miles back.

It is less than three miles diagonally to the threshold when I'm allowed to turn to land. I've already cooled my engines and slowed to the first stage of flaps, so now I chop the power and pull up the nose to get the speed down so I can dump gear and the rest of the flaps and plummet to the runway. High density altitude gives me a high groundspeed, but also a high descent rate, so I make it down to runway level as I reach the big 35. I've arrived.


Ed said...

If you're flying at moderate heights, less than 18 000 ft or so, can't you use a cannula rather than a mask? That is, one of those little plastic things with two tubes that go up your nose.

I've only ever used masks myself but some people I know who do a reasonable amount of glider flying in wave in Scotland swear by them.

As an experiment, one of the chaps from my club flew with a blood oxygen monitor clipped to his finger tip. His wife is a nurse who specialises in intensive care of premature babies so could borrow the monitor to play with. No blood needed to come out; it works on the transmission of light somehow though I never got a full enough for my scientific curiosity answer on the details of how.

majroj said...

Pulse oximeter is what you're looking at. Most are calibrated for index fingers without nail polish, but earlobes are what they used them on initially, so must be available.
I think our hostess talked about nasal cannulas before? They supply oxygen at 1 to 6 liters per minute, at mean sea level furnshing about 20% to 44% oxygen. Pilot masks can furnish 100% oxygen (not good for very prolonged periods), using the oxygen at a much higher rate (about 15 lpm; I don't work with pilot masks).

Thanks for "taking us along"!

Guy said...

I have a pulse oximeter that I bought from Sporty's. It's fairly pricey for something I don't use very often, but I was worried about altitude sickness when I started flying.

It just clips on your finger, no bleeding required. It shines an LED on your finger to measure your O2 saturation, and also reports your pulse rate.

Anonymous said...

Ref: 10,000 vs 12,500

Though you have a Canadian license and are flying a Canadian aircraft, you don't get to "When in Rome, do as the Romands do"?

In other words, is the 10,000 requirement to use O2 imposed by your company, or by a license requirement to follow the stricter of Canadian or local regulations?

Medic_9 said...

Pulse oximetery works by shining two different wavelengths of light through your finger (or earlobe) and then calculates the difference in wavelengths reaching the sensor on the other side. Hemoglobin is the part of your blood that carries oxygen molecules (most of them anyways, some can be free floating). Hemoglobin absorbs some of the light and the computer in the pulse oximeter calculates from that how much oxygen is in your blood. It's a painless application of light.

Carbon monoxide binds to hemoglobin more strongly than oxygen taking up spots for oxygen to be transported. That's why it's deadly. A pulse oximeter can't tell the difference between CO and CO2 though.