Volume 32 No 4 Aug-Sept 1981.pdf - Lakes Gliding Club

e published In "Aero Revue" or "Technical Soaring" and witl be
collected in OSTIV Publication XVI, all under the edilorship ef
Cedric Vernon, Tl1lis being so, there is not much point in reviewing
them in detail, bul it is worth mentioning a few themes,
The strategy and tactics of cross-country flying continue to
intrigue the mathematicians. For example, given cloud streets at
some angle to one's desired track, what is the most efficient way of
using them? Mr de Joog from Eindhoven presented a neal solution,
but his device for pilots' use Itooked too complicated, And there is
the dolphin problem: how to extract the maximum energy from the
air when flying through thermals, or how to maximise the speed ,for
zero overall change in energy height, The difficIJlty here is that the
classical MacCready "best-speed-to-fly" ring implicitly assumes a
load factor of unity.' Not only is the Iload factor manifestly not unity
from time to time il one dolphins vigorOUSly, but it may be distinctly
advantageous to vary the load factor as well as the speed, For some
time it has been knowf'l that il pays to increase the load factor in
rising air (by performing a pull-up) andto decrease il in sinking air,
quite apart from the resulting speed changes. Obviously, load factors
differing significantly Irom unity cannot be sustained lor long
periods so vigorous pitching manoeuvres are really only suited to
traversing' fairly small patches 01 lift and s'ink.
There were several papers on Ihis theme, that of Wolfram Gol'1isch
of Akallieg MOnchen being particularly elegant and /:1fghly relevant
to practical flying. H'e proposed rules,Jor achieving near-QP,timum
results which do not require the powers 01 prophecy implicit in
some invest'igations, It is worth quoting from his paper:
"Two quantities must be introduced: the 'averaged speed' and
the 'averaged climb (or sink) rate', The rules for the pilot are as
follows:
"1. Adjust the average speed according to a speed command, as
indicated by an averaging total-energy-compensated variometer on
the MacCready ring,
"2, Perform load variation according to the actua'l variometer reading,
The speed, of course, oscillates but its average shall be maintained
according to rule 1.
"For practical reasons, the average TEe cllimb/sink rate may be
deriV1ld by electronically damping tile signal and ap:pl'yingo a large
time constant. The appropriate time constant remains 10 be
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This is all splendid stuff, so it was rather a pity that OSTlV was
musing on such matters at the university, some distance from the
aidield. We were enjoying a superb lectu re theatre, but it is mIJch
more satisfactory if Championships participants can drop in to hear
inte,resting papers.
The design of wing sections does not seem to have been finalised
by the wOrk of Wortmann and Eppler, Professor Boermans of Delft
explained the design and testing which went into Baer Selen's
ASW-19x, with its pneumatic turbu'lators (see "The Hardware, .."),
demonstrating a lavish application of talent and equipment. Armin
Quast of OFVLR, co-designer 01 the section 101' the ASW-22, spoke
further on suc,h matters and opined that little holes would become
widespread.
Talk of bug impacts
There was much talk of the effect of bugs on leading edges, Flapped
sections are more sensitive to bug contamination than the
un flapped variety and, moreover, show markedly different distr,ibulio!i1s
01 bug impacts. It was thought that Dick Johnson's simulated
bug patterns were not always correc!. Also, a Standard Class sail·
plane can be almost as good as a l'5m ship if both are heavily
splattered with squashed bugs,
My own contr,jbution related to the optimum centre of gravity
position tQ minimise overall energy losses, taking into aCCOl,lnt both
circling and straight flight. All will be revealed in a luture 8&G,
I must confess thall saw very. little of the meteorological papers,
preferring to stay at the airfield to hear Hans Werner Grosse talking
about his flig,hts in Australia and Ursula Hanle on aerobatics, illustrated
by a splendid film, On the afternoon I did attend the Mel
session, we had Professor Scorer of Imperial College - how pleasant
to see his interest in soaring revived - talking aboullhe spac,
ing of cloud streets, We'al'so saw some time-lapse satellite pictmes
which ,compressed' a day of convection cloud patterns into about a
minute,
Finally, there was a general conference (elections, rules, finance,
elc) and a magnificent closing. dinner, prepared by the current holders
of the German two-seater 500km speed record, in the elegant
surroundings of Schloss Neuhaus, Little speeches were made,
mainly to mark the resignations of Floyd Sweet and Joachim Kuettner
as sectiQn chairmen. We returned to the contestants'final party
at the airfield' to Hnd that they had dined rather less spendid Iy than
osnv.
As usual on such occasions. t,he renewal of old friendsh'ips and
the making of new ones was at least as important as the technical
con,tent of the papers; The whole Congress and our rather
per,ipheral exposure to the Championships was remarkably pleasani.
,All credit to those who worl< so hard to keep OSTIV ffomishing,
notably Manfred Reinhardt, Piero Morelli, Hans lacher and the
indefatigable Edilor Cedric Vernon,
OSTIV, by the way, stands fer "Organisation-Scientifique et
Technique Internationale du Vol a Voile", You, too, can parlicipate
in the intellectual aspects of soaring: for details 01 membership,
publications, etc, write to, OSTIV, clo OFVLR, 0-8031 Wessling,
West Ger/illany, RI
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AugustlSeptember 1981 187