For the week 24 - 28 October, I was duty instructor for Caboolture
Gliding Club's cross country week at Darling Downs Soaring Club.
Unfortunately the weather was rather uncooperative, even though we flew
every day. Thunder storms were the order of the day - with the storm on
Monday evening being a real whopper, dropping over 25mm of rain and
knocking out the power for nearly 24 hours.
All that rain made the black soil paddocks completely unlandable - when
we did get airborne on Tuesday afternoon, water glinted in almost every
furrow and there were visible runnels in many paddocks showing where the
water had gathered into spontaneous streams to run towards Oakey creek
and its tributaries. Each evening there were more thunderstorms in the
area - with the airfield fortunately only catching relatively minor
falls. Any ventures away from the airfield were going to have to be
conducted within final glide to a known landable airstrip!
All this rain and the associated wet paddocks also damped down the
thermal activity. To add to the fun, Oakey airbase was operating, which
restricted our airspace - a factor that became really significant on Friday.
On Thursday it appeared that an initial cross country rating flight
might be possible - so Gerard Reiter and I set off in the Grob. It was
extremely hard work - even just staying airborne - as the thermals were
weak, short lived and not going very high. Fortunately Caboolture pilots
are well used to this sort of conditions, coming from a strip close to
the coast. We made several abortive attempts to move upwind into the 15
to 20 kt headwind towards Dalby, each time having to scurry back to the
security of the airfield when the lift ran out. On a couple of occasions
we were able to find a good energy line that lead us onward but these
petered out and back we came.
After about an hour, we found a line marked by faint wisps of cloud that
took us towards Dalby and, beyond its end, there were clouds in range
upwind just outside Oakey's airspace. So we headed off across the blue.
There then ensued an interesting 5 minutes in quite weak lift where we
played "climb and drift" in weak bubbles on the edge of final glide into
Dalby before we contacted a reasonable (for the day) 3kt thermal. The
importance of switching to the Dalby CTAF frequency was underlined by
the announcement of the impending arrival of a military helicopter into
Dalby through the airspace we were struggling in!
Once we had sorted out exactly which road/railway line we should be
following out of Dalby (we are really lucky to have such a good example
of the importance of good pre-flight planning and map reading so close
by) we could start looking at how to get to Jimbour House and its
airfield. Looking north, the reasonable clouds were well west of our
desired track and it was ominously blue for some distance around Jimbour
itself. We headed for the clouds, taking the best lift as we found it.
As the wind was trending more northerly with height, we were still
mostly into wind on this leg, so progress was slow.
Moving too far west on this leg also had the disadvantage of taking us
away from George Lee's strip (about halfway between Dalby and Jimbour) -
so wherever possible we tried to find lift back towards the east.
Looking ahead, it seemed possible we might be able to time the short
lived clouds to reach Jimbour and after a while that was the case: we
had a safe final glide to Jimbour. As we pushed into the wind though the
wisps over Jimbour died and we found ourselves struggling to stay
airborne overhead the lovely long runway at Jimbour House.
After a long search, gaining 100ft here and there in tantalising short
lived bubbles to keep us airborne, we had a weak climb that gave us
final glide back to George Lee's strip (courtesy in no small part to the
tail wind). From there, the sky towards Dalby started to look better and
we were able to head down wind. There was a really good looking cloud
drifting out of Oakey's airspace right on the corner near Komomurra
Silos and we carefully skirted the corner and were rewarded by our best
climb (4kts) as we drifted south away from the airspace boundary. From
cloud base, McCaffrey Field was easily in range of a downwind final
glide and, as is always the case once you have final glide, we flew home
though large quantities of lift.
We had been airborne for over three hours - averaging about 40km/hr -
quite a marathon!
On Thursday evening a thunder storm passed between Dalby and the
airfield, but very little actually fell on the airfield. Haze domes and
wispy clouds were in evidence when Dave Muster and I launched in the
Grob - having sent a Nimbus 4 and a Duo Discus off as sniffers! The
importance of taking lift where we found it was demonstrated when we
didn't take a good thermal at about 1200ft on the launch and were pretty
quickly back on the ground. We relit and there then ensued one of the
more memorable struggles I have ever seen.
The wind had dropped off considerably compared to Thursday, but it
quickly became clear from the cloud patterns that there was a very
significant rain shadow that corresponded almost exactly to Glider South
Alpha (the segment of Oakey's airspace that was released to us): just on
our side of the railway line, good clouds formed up to drift slowly
north into Oakey's airspace whilst just south of the Jondaryan/Tipton
road (marking the southern border of Glider South Alpha) good clouds
decayed into rapidly fading wisps.
Glider South Alpha was predominantly a big blue hole.
We tried along the northern boundary, circling until we were driven away
by the northward drift towards the airspace boundary to scurry back to
the safety of the airfield. We tried along the energy lines of decaying
clouds near the southern boundary to the same end. We took thermals off
Formartin feed lot in the centre hoping to achieve a link to a could
closer to Dalby. In fact, we tried each route several times before
finally we were able to link sufficient height with the appearance of a
reachable cloud towards Dalby. It took us three hours to reach Dalby -
an awe inspiring 10km/hr average speed!
Once we had reached Dalby, we once again spent a few minutes finding the
right road/rail combination north to Jimbour. Following this road we
were able once again to stay in final glide to a landable strip and
arrived at Jimbour House where there were good clouds and we reached
cloud base. Back south towards Dalby, the effect of the rain shadow was
clear and we didn't have a strong tail wind to help us this time. We
took what clouds and wisps there were but arrived at Dalby only about
2,000ft above ground, searching over the airfield, town and surroundings
for something usable. We spent some time gathering together enough
height to push eastwards towards McCaffrey Field and then found another
climb just before entering Glider South Alpha.
This petered out before we had final glide home, though. So we pushed
eastwards, carefully watching our height to ensure we had final glide
back to Dalby. We found some good air before Formartin that buoyed us
along (but not up) and I could see we had achieved the barest of final
glides home. Between Formartin and the airfield was more lift and we
arrived at a comfortable circuit height, landing after a flight of
nearly 4 hours!
David and Gerard certainly earned their initial category cross country
ratings - and I think between us we can probably claim the two longest
initial cross country rating flights in the history of the club!
--
Robert Hart [EMAIL PROTECTED]
+61 (0)438 385 533 http://www.hart.wattle.id.au
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