Eddy Currents

I planned to give some night flight rides to friends and family
visiting this weekend. Winds during the day were steady at 8 or so at
MGW and ACG. I called the Connellsville (VVS) AWOS and it reported
winds calm after dark. So it looked like a good night to take a
pleasant joy ride.

Temps were hovering around 50 so no preheat required. The engine
started up immediately and I maintained a 1000-1100 RPM idle for a
while to get the engine up to operating temps.

After a suitable warm-up, I briefed my two passengers and rolled onto
23.

The ground roll felt fine and initial take off was normal -- but once
we hit 150' AGL the pleasant flight turned into a battle to stay
upright.

The topography near VVS is somewhat complicated with low level series
of hills known as the Pittsburgh plateau to the west and the
westernmost ridge of the Alleghenies immediately to the east (you can
hit that ridge if you don't turn soon enough after taking off from
14). The mountains run slightly west of south in a line towards West
Virginia.

This evening the rather light winds were being reported as variable
(all over, actually) by the AWOS. But what was really happening was
that a very strong wind was blowing from the south very close to the
ridge altitude (approximately 2500' MSL), and then rolling off the
ridge line. So what VVS AWOS was sensing and reporting were the
swirling eddie undercurrents (thus the generally west winds). The A36
is usually a very stable airplane, but in these conditions it was
taking full control deflection to remain upright. I apologized to the
passengers and told them we were heading back.

I continued climbing at 110 KIAS until about 2500' MSL (only about
1300' AGL) where it seemed a bit less turbulent. Once established
level I began a shallow 270 degree turn with the initial turn to the
west to keep us away from the direct lee of the ridge. While still
turbulent, it was less violent than what we had experienced on climb
out.

I considered landing on 14, but it is a shorter runway with no PAPI. I
decided I would take my chances on 5, given it is the longest runway
at VVS and that surface winds were variable, so there would be no
certainty of headwind or tailwind. I listened to the AWOS and the wind
direction was unpredictable, yet velocity never exceed 8 knots.

I trimmed the airplane for 85, but airspeed fluctuated between 80 and
100 on extended final. I was actually approaching runway 5 at about a
40 degree approach angle to stay as far from the ridge as long as
possible.

Once the runway environment was in sight and established, the PAPI
indicated high on the glideslope. But I wanted to come in somewhat
steep and fast to avoid ground turbulence. I decided to add flaps to
help steepen and slow the approach.

This worked out, and the steep descent at 80 KIAS brought me just shy
of the aiming point. I reduced power and flared flat. A final kick of
the rudder and we were straight and centerline. We touched down very
gently and maintained centerline on rollout, with minimal braking
required.

This night was nearly identical to my experience in the V a few months
ago -- wild, full-deflection turbulence with near smooth as glass
touchdown. I think the main issue when the wind is blowing from
between 060 and 190 is the strong sheer above the airport -- the
stronger the wind, the higher the eddy area. In really strong winds
(30 Kts), the AWOS is completely unreliable and the eddy currents
200-1000 AGL are nearly unflyable.

If I was going someplace, I would have turned west and climbed to at
least 8000 before picking up any heading between 030 and 180.

I only logged 0.5 tonight but it was quite a bit packed into that .5!

Dan
http://trainingforcfi.blogspot.com/