Thursday, July 16, 2009

On Again

A new day, a new decision. We'll fly to Fairbanks, clear customs, and then take commercial flights home while maintenance does a phase check and the replacement crew flies in. Someone must have factored in the airfares and that shifted the math. Airfares are relatively cheap in and out of Fairbanks, as they are for most big-city American destinations. We won't get to see the remote Alaskan spot we had hoped to visit, but the novelty would probably have run out before the work, and we will get to cross northwest into Alaska.

After I get that news, I go flying. If all goes well, this will be our last flight returning to this base -- although my Alaska charts still haven't arrived. Apparently this place has some sort of repellent force that prevents newspapers, courier deliveries, mail and airline passengers from arriving on time.

The last three METARs report cloud bases at 5900', 5800', and 5700', which is odd because I asked the specialist earlier and he said they didn't have a ceilometer. All cloud heights are estimates. How would they, in the absence of nearby mountains, determine a hundred foot difference just by estimation? On other days the bases have been given to the nearest thousand feet. I ask about it.

The answer is that today, because the clouds are all cumulus, they are reporting the bases not by visual estimation, but according to a formula. I understand. I know that formula. I didn't know anyone used it for anything other than written pilot examinations. Here's how it works: cumulus clouds are formed when rising air is cooled to its dewpoint by expansion. Rising air cools through adiabatic expansion at a rate of 3 degrees Celsius per thousand feet. The dewpoint decreases by about 0.5 degrees per thousand feet. Therefore the temperature approaches the dewpoint at a rate of 2.5 degrees per thousand feet. The reported surface temperature is 21 degrees and the surface dewpoint is 5.2 degrees. So at the surface the temperature is 21 - 5.2 = 15.8 degrees above the dewpoint. The temperature will reach the dewpoint 15.8/2.5 = 6.3 thousand feet above the aerodrome. (This doesn't match the earlier report because they have given me current temperature and dewpoint values and the temperature-dewpoint spread has evidently increased by a degree since they did their last calculation. Drop the temperature to 20 and do the same math and you get 5900'). METAR altitudes are given above aerodrome elevation, which is 1250', so I can expect bases to be at about 7500' above sea level, as displayed on my altimeter.

Another pilot hearing this conversation calls in to report bases at 7500'. Science! It works. Also don't you love Canada? We have formulae that combine degrees C with Imperial feet and we think it's just fine that way.

In Canada either a flight plan or a flight itinerary must be filed for a VFR flight of more than 25 nm. A flight plan is filed with Nav Canada but a flight itinerary can be filed with anyone responsible enough to report you missing. Commercial operations like mine generally file with company and when we inform ATC of this we say we are "on a company note." That shortcuts ATC asking if we want them to open our flight plan. In imitation of this practice, a small aircraft pilot taxiing out calls the FSS and says he is "VFR to Helmut on a note." He then decides that this needs more explanation, as the FSS knows he is a private owner and not a company, so he adds, "My wife."

Another pilot calls up "Looking for the airways to Ft. St. John." That's a non-standard way to ask for an IFR clearance, but seeing as the FSS probably has his clearance sitting there and is is waiting for him to call to ask for it, he could probably have said anything he liked and still received it. If you don't ask for it, they offer it, as when the tower says to a airline pilot after he makes a taxi call. "Grab your pen."

Then it's my turn. The wind is straight down runway 26 at 10 knots, so it's an easy taxi and take-off. As the airplane waddles up to altitude in the hot weather I call to report airborne, and my turn. The FSS does a shift change. It's a woman with an unfamiliar voice, and she comments to someone on air that she's just back after two weeks. I guess she's out of practice, because she keeps getting confused, forgetting which airplane is where, scrambling our types and needing constant position reports. I am ready with a position report whenever she calls me for one and make sure I am keeping track myself of where the other aircraft are.

Sarah said...

Hurrah? I have learned not to count on the trip until wheels up.

Can we hope for pictures on the way up or are/were/will-you-be still cameraless?

So you'll miss the North Slope.. maybe just as well, there's something ... strange in the water up there. cues twilight zone music...

Capt. Schmoe said...

Well, Aviatrix,I don't know what is in store for you. I just hope you start flying again real quick and that you share it with us.

Have a safe trip to Fairbanks.

Daniel said...

We use the same feet/degrees C over here in Europe, too.

nec Timide said...

And, as always, you can get a T-shirt.

When ever I talk to young people about flying, one of the first things they notice is the mixed units. But, as my high school physics teacher used to harp on, if you can't keep track of, and use the units, you can't hope to recognize an answer that has the decimal place in the wrong location. Mind you, in those days we used slide rules.

nec Timide said...

Maybe you should consider yourself lucky. You could have been eaten by the blob!

Aviatrix said...

How do you know we aren't flying support missions for the blob?

nec Timide said...

Ooooooooh! Interesting. A blob with air support.