Turbulence

My final stage check was scheduled for this afternoon.  This is a dry run for the practical test, and if I do well, they will let me take the actual checkride.  The surface wind at Dulles was forecast to be 10 gusting 20 knots, but the actual conditions at HEF turned out to be less than that.  It was another story at 3000 feet:  the wind speed was almost 50 knots.  When I arrived at the airport, my regular CFI had just returned from a lesson and he warned me that I would be tossed around.  Pilot Reports (PIREPs) confirmed that:

CJR UA /OV CSN/TM 1452/FL030/TP C182/WV 27040KT/TB MOD 030-020/RM COUPLE DOWNDRAFTS

I finished all of the computations for my cross-country flight plan with the current weather.  I had computed a +24 degree wind correction angle today, given the strong winds aloft: that's quite a crab.  The senior instructor performing the stage check pointed out clouds that appeared to be lenticular in shape, a clear indicator of strong turbulence.  As it was noon, the afternoon heating was just going to make it worse. So I opted to get the oral portion of the check done today, and I will fly tomorrow afternoon.

I learned a few new things today from the test (apologies for the long list--it is really for my own benefit as it helps me to remember if I type these things out):

1. The winds aloft forecast doesn't list the temperature at 3000 feet, my cruising altitude in this case, but they do at 6000 feet. I need that temperature for density altitude calculations, though. I usually estimate the temperature at 3000 feet by adding 6 degrees centigrade to the forecast temperature at 6000 feet (this assumes a -2 degree centigrade per thousand feet lapse rate).  The instructor said that the forecast temperature is usually wrong, and that I should just extrapolate from the actual observed surface temperature instead. Good to know.
2. The invisible 20nm outer ring of Class C airspace is where VFR pilots are encouraged to contact ATC for RADAR service (traffic advisories).  What I didn't know is that inside this ring, you are guaranteed to get RADAR service if you ask.  In most areas, VFR traffic advisories or flight following is provided on a workload-permitting basis by controllers, and they can refuse if they are too busy.  I've never been refused flight following, but I was dumped once on the way back from Charlottesville (the controller said, "RADAR service terminated. Squawk VFR. Frequency change approved.")
3. When trying to spot Class D airspace on a chart, look for the bracketed square containing the ceiling altitude of the surface area as this is clearly visible.  Sometimes the blue dashed boundary of Class D will be difficult to see when buried underneath Class C airspace markings as KNGU is here.
4. FAR 91.211 states that supplemental oxygen is required above 12,500 feet MSL (as in 12,500 feet not inclusive).  You can legally fly around all day at precisely 12,500 feet without supplemental oxygen.  Just as the Class E airspace begins at 1,200 feet AGL (the title of this blog, incidentally), Class G ends at 1199.99... feet.  I really need to study which regs are written as "up to but not including" before the test.  The lawyers just couldn't be consistent when writing these things.
5. During the practical test, I should say altitudes to the examiner just as I would to air traffic control over the radio ("one thousand two hundred" not "twelve hundred," and "flight level one eight zero" not "flight level one eighty"). Sounds more squared-away, I guess.
6. I had not seen the taxiway ending marker before.  I'm not usually stumped by signs, so I'll be sure to review them before the test.
7. It is my responsibility to remember to bring a hood--a view limiting device--with me on the flying portion of the checkride. I'll surely fail if I forget: this has actually happened at my school.
8. When picking a cruise RPM/power setting for the checkride flight plan, just keep it simple by choosing a round RPM number (e.g. 2200 RPM) and figure the power setting directly from a table entry in the pilot's operating handbook (POH).  I had done what I'd likely do in real life: start with a power setting of 65% and then interpolate the RPM from the POH based on the density altitude.

This hour of ground instruction was enjoyable. I'm looking forward to flying tomorrow.