| Lying awake in
bed last night, I could here the Easterly wind whining past my
window. They say that Perth, Western Australia, is one of the
windiest cities on Earth. It sure is a crazy place to live if
one has an interest in free-flight model aeroplanes. We have to
travel 130 km to the flying field, which is basically a piece of
desert sand out in the wheat belt. The crazies here actually
held a National Championship at this site in December 2008. The
temperature was 43 C and the wind speed for most of the day
exceeded 9m/s. I didn’t even know that I could live in such
conditions, leaving my models in the car. We normally don’t fly
from early November thru to April, precisely because of these
strong Easterlies.
Whatever, my thoughts turned to a more amenable place, the turf
farm at Richmond in NSW. Bordered by a river and ridge on one
side, barbed wire fences and a RAAF base on the others, you
would think that was equally crazy. But in the many years that I
flew there, I cannot recall a time when it was too windy to fly.
I had a model cross the river, but none fell into it.
The thing is, I had plenty of opportunities to observe the
motions of the air. Here are some of my recollections, which I
hope you may find of interest.
An early winter morning arrival at the field was blessed with
dead calm air. There was no dew on the ground, as it was all
caught in the spider webs which formed a lace of beads literally
everywhere. I believe there is one spider for every 6 square
inches of the land surface of the Earth: the spiders on this
field sure lived up to that claim.
The air was cold. Starting the Rossi gave a blast of freezing
air onto my hands, quite painful in fact. The trajectory of the
model was very smooth, no turbulence at all: the glide down was
likewise very smooth, like sliding on glass. No thermals,
nothing at all.
As the day warmed up, this slowly changed. The spider webs
disappeared, the air near the ground warmed, and it became
necessary to open the needle a little each flight to stop the
development of a lean condition. An engine stop when using VIT
is not to be recommended! Interestingly, the model started to
rock a little as it glided down into the warming air. In fact,
there was a distinct height where the smooth glide broke down
into a rocking motion of the wings.
Above this layer, the air was still cold and smooth: below it,
turbulence was present.
I decided that this must be the “inversion layer” that I had
heard about. Later in the day, this layer got really high, and I
figured it must lie at the cloud base .
By mid afternoon, things really got lively. I could see from
time to time that wind blown circles formed in the grass as
thermals passed thru. There were upper level winds that had no
presence near the ground. At one time I noticed that the clouds
were blowing in 3 different directions! This was a problem as my
F1C had failed to D/T: chasing it in my car with no observer was
definitely hazardous. As a result I lost sight of it and that
was that for 2 years.
Then I got a phone call from a rather bemused farmer. He had
found a nice shiny Nelson 15 sitting in the middle of a pile of
weathered, fragmented balsa, all that remained of the model
after all that time in the open. He couldn’t figure how the
engine got to be there, so differently had the elements treated
the Nelson and model!
This turbulence below the inversion layer could be quite
extreme. My F1C was hit by lift on one wing only. It literally
rolled inverted, dived into a half loop and glided back in the
reverse direction! Seeing is believing.
Another time I was in Victoria at F/F contest, sitting back in
my folding armchair and watching the efforts of my colleagues
out on the flight line. One guy was working on his F1C, turning
to get something from his flight box. In the few moments his
back was turned, the model rose off the ground, into the air
about 2 feet, and then fell back, breaking the tail boom. What a
nasty air-God it is that does that with thermals!
Another time in Meckering, by young friend Denzyl had his Pink
Elephant A/2 D/T from about 600’. For some reason, this model
never did sink gracefully, but came down in a horrible spin that
always broke something, usually a wing tip. We spent most of the
comp repairing it in time for the next round. But on this
occasion, the model got down to just above tree height and went
into a flat spin. It stopped losing height, and just spun faster
and faster, like a Catherine wheel firework. This went on for a
full minute!! Then it crashed, situation back to normal!
On a more serious note, I have seen turbulence that could easily
deck a jet airliner. We had a C/L field in the approach path to
Perth domestic airport, very nice field it was too. One day I
was looking East for a jet to come, but what I saw was alarming.
A belt of trees lay in the flight path, and as I watched, there
was a commotion about 50 metres in diameter in the top of the
trees. Small branches were being ripped out of the top of the
trees and flying skyward. What luck that no airliner was going
low and slow through that lot!
The next time I was approaching my home in Balga from the
Eastern freeway. A mighty black cloud was settled over Balga,
and as I watched, a torrent of rain fell from it. Well, it
didn’t so much as fall, but plunged violently downwards. When it
hit the ground, it burst out sideways at ground level. So that
was what they mean by a downburst! No wonder big jets can get
hurled to the ground while landing, with that level of violence
in the atmosphere.
On a lighter note, while driving on the same section of freeway,
I saw a willy-willy crossing the road on a collision course with
my vehicle. Quickly I wound down the windows, allowing the
vortex to rage through my vehicle, messing up everything. Gee it
was good!
Another time I was enjoying an Airshow with a bunch of T6’s on
show. Again, I was sitting on my folding armchair, directly
behind a T6. Then it started up with a mighty roar, sending a
shower of stones and dead grass over me! Heroically, I clung to
my chair, refusing to move. Hey, I could be dead tomorrow. Here
was a really great piece of fun! I mean, how often do you get a
Warbird attack you?
Not quite as funny, I took my aged mother to the Bowral airshow.
This is a narrow strip, placing the spectators right up close to
the action. Suddenly a Spitfire roared down the strip, I swear
its prop tips only a metre from the ground. My poor mother clung
in despair to her chair, and bravely rode out the violent
passage. But then, not 5 minutes later, a MIG 15 did the same
thing. That was too much. My poor mum could take no more. “Take
me home”, she cried, her spirit broken.
Well, it seems to me that air we like to fly through is far from
placid at times. They say that good airmanship is knowing when
to fly, and when not to fly. I guess the best way to learn these
lessons is by listening to the old pilots. Not just listening,
but hearing!
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