23 April 2015
Rule changes ahead to tame model performance
by Sydney Lenssen
Should we celebrate how clever aeromodellers are at wringing the best
out of competition models, or do we need to change the rules of FAI
contests if we want to continue to enjoy contests?
The fact is that today’s models which depend on thermals, especially
those produced commercially almost ready to fly, have such high
performance that expert pilots can and often do score maximum points.
Contest winners are often just a point or two apart. The champion is
usually just a whisker ahead when he mounts the podium.
Why is this?
The duration task in F3B contests provides a simple example. The model
is launched by a strictly regulated limited power winch together with
a turnaround pulley set 200 metres away, and pilots fly in groups
aiming for a 10 minute flight and an accurate landing. Not so long
ago, in the usual tricky weather, achieving sufficient points to win
the slot, was not straightforward and required a skilled thermal
reader. But today most competitors score full marks and nobody gains
The two other F3B tasks are distance and speed. Again in distance, top
pilots manage to complete a large number of laps, flying at high speed
up and down the 150 metre course, rarely cutting too short in their
haste, and scores are pretty level if not as close as in duration.
Only in speed is there a significant difference between pilots, and
the score is a simple time, X seconds, with only one pilot flying at a
time. The contest is often won or lost in speed.
In free flight competitions, present day difficulties have many causes
in all classes, rubber, power models and gliders too. The prime
problem is that wide open spaces suitable for models which must by
their nature fly downwind, are becoming harder to find, and for the
qualifying rounds with two or three minute maxima as target, the model
is not likely to land inside the borders. In fly-offs with longer time
targets and sometimes half the competitors having qualified, the
problem is far worse.
But freeflight models today are full of technology, not only to
dethermalise the flight but to alter the geometry of the plane,
incidences of wing and tailplane, flaps on the wing and probably other
gadgetry to improve performance. The only blessing for a pilot such as
me is that the model carries a locator device to alleviate searching,
providing it doesn’t end up lodged in an old high tree!
Mike Woodhouse, chairman of BMFA’s free flight technical committee,
has summarised the problems in the April issue of AeroModeller, an
excellent and getting better magazine which I highly recommend.
His five points are:
Ever increasing performance of the models, both in absolute terms and
The pool of knowledge that has developed with respect to the
understanding of how our models fly.
Improvements in the technology that is now used.
Pressure on flying sites.
Increasing average age of the membership cohort.
He also urges that anyone considering changes or solutions should also
remember that “We are where we are, and we have to work from here, not
from where we might like to be.”
Last year I wrote about F3J competitions which in a short life - about
25 years - started as simple balsa, spruce and ply soarers lovingly
crafted by the modeller and towed by a single towman or bungee. Pilots
waited after the start buzzer to see who would launch first and
whether or not kinder air was found. Rare was the slot when everybody
flew the whole 10 minutes.
Today most of the models are manufactured with high skill and
excellence from exotic materials capable carrying high stresses with
limited distortion, with aerofoils and aerodynamic properties honed by
sophisticated computer programs and wind tunnel tests.
Even in still air, most of these models can fly out the 10 minute
slots and are strong enough to withstand a speared landing at speed
and high tension launches. Times of flights are measured to one tenth
of a second and the landing tapes are split near to the spot in 20 cm
intervals. Only in the fly-off rounds of 15 minutes is there much of a
chance to find a decisive difference between the skills of each pilot,
and if it is thermally the margins almost disappear.
Many F3J fanatics from around the world responded and that pleased me.
But there was little consensus. The strongest opinions favoured
introducing a maximum wingspan and minimum wing loading, and requiring
a five second launch window before the measured flight time is started
to reduce the current one or two second rocket launches.
The far younger sport of F3K, handlaunched gliders, is also finding
that in some of the tasks, the models have already reached such
outstanding performance that they are considering adding new tasks
which will result in wider score differences.
What to do about models which are too “good”
Over the coming weekend in Lausanne, CIAM, the aeromodelling section
of FAI will meet to try to sort out rule changes. The agenda for the
Plenary meeting which approves or rejects the recommendations of the
various specialist technical committees has 83 pages, of which 11
pages are devoted to rule proposals for freeflight models, five deal
with F3B changes and 11 pages have new rules for the F3K class
including three new tasks.
Because rule changes for each class are only allowed at two year
intervals, any changes for F3J will only emerge next year. Even when
changes are fully approved, they do not come into play until the start
of next year unless urgent safety matters are involved.
All the details of who has proposed the changes and the reasons are
available on the FAI website if you want to find the nitty gritty. But
to avoid this article running to dozens of pages, let me pick out the
main changes aimed at curtailing performance, widening score margins
and recognising the limitations imposed by the size of available
F3B rule changes
The biggest change for F3B is that the distance between the winch and
its turnaround pulley is to be reduced to 150 metres rather than the
200 metres which has ruled for several decades. This has been proposed
by Germany which almost certainly has more F3B competitors than any
They reason that nearly 90% of pilots fly ten minutes in neutral
conditions, and recently the speared landings - “stick landings” -
have found their way from F3J to F3B. They do not want to see ten
minutes increased as it extends the time required to run the contest
and most pilots will do it.
Other advantages to be gained by shorter towlines are that smaller
fields can be used and bad weather in the shape of low cloud or fog
will not be so restrictive.
F3K rule changes
Sweden has proposed that Task F is dropped, where pilots can launch up
to six times but each flight must be to a maximum of three minutes and
the three longest flights add up to the score, all within the 10
minutes of the task. The reasoning again is that this task produces
little or no separation.
First of the new tasks is named K (Lowest flight of two, Deuce) in
which the pilot has only two flights in a working time of seven or ten
minutes and the lowest time of the two counts as the final score. This
new challenge promises to be a certain method of widening margins. The
penalty for a bad flight is severe and must favour those pilots who
are consistent in reading kind air.
Second new task is Task L (Two flights, five minute maximum) where
each pilot must launch the model twice with a maximum flight of five
minutes, both flight times counting as the score in ten minute slot.
That is going to present a real challenge although the proposers USA
reckon that it is easier than Task K.
Then the third Task addition is M (Increasing time by 30 seconds, “Big
Ladder”). The model must be launched five times with the target time
starting with one minute and going up each time by a further 30
seconds to reach three minutes on the fifth flight. Unlike the
existing Ladder Task, the pilot does not need to achieve the target
before moving onto the next stage, but the time for each of the five
flights will be added to make the score. I suspect that introduction
of this type of ladder will not widen scores much, but the task should
The biggest and most important step in all types of freeflight models,
glider, rubber and piston power, is that variable geometry on the
models will not be allowed and changes of camber not permitted.
Why? The wish is to reduce the building complexity of models, to cut
the cost of models, to reduce the potential performance. Those
freeflighters flying for fun might be encouraged to compete if they
wish. The aim is to reduce the gap between the good flyer and the high-
Poland is proposing that the maximum length of launch cable should be
reduced from 50 to 40 metres. More puzzling for me is that Poland also
wants maximum duration of flight in the first round of the
preliminaries to increase from 3 minutes 30 seconds to four minutes
since subsequent rounds have three minute maxes.
The UK proposal is not to reduce the length of towline but to require
a minimum diameter of line of 1.75mm, which should reduce launch height.
In rubber, the new rule would reduce the maximum weight of the
lubricated rubber from 30 to 25 gm, a far cry from when I started
where weight of rubber often exceeded more than half the model’s
weight. Also the propeller must be released before the model leaves
the pilot’s hands, rather than the current javelin launch before the
prop rotates. Long gone are the days when the model was required to
rise off the ground.
For power models, both Poland and UK propose that the maximum duration
of the motor run goes down to four seconds rather than five, which
will take some precision timing. My first power model had an eye
dropper for the fuel, nobody bothered about the constituents of the
fuel, but we all had fun.
Now in each of the freeflight classes, the BMFA technical committee
has submitted a long well argued support for ambitious proposals. Let
me quote some parts of the bold plan. The only reason it might fail is
its complexity and commitment.
“The performance of F1 class freeflight models has reached a level
which now exceeds sensible limits. The UK believes that CIAM should
commit to a planned stepped change in performance reduction over a
period of five years. The CIAM bureau should mandate the F1
subcommittee to take action to implement the necessary changes.
“We have the situation of models out flying the sites available to us,
especially at flyoffs with up to 10 minute flights. We need a long
term plan to reduce perfomance, but without emasculating the class.
“We should also seek to reduce complexity and thus cost. The models
should be brought closer to the reach of the average sportsman and
reduce commercial involvement. The level of performance reduction
needed is 50% to enable a meaningful competition with around maximum
of 2.30 minutes and a model maximum performance of no more than four
Firm management will certainly be required if this approach is not to
damage the enthusiasm for each type of freeflight class. Should CIAM
go along with BMFA’s arguments and adopt the proposals, the
individuals involved will have a tough job to save the sport; annual
meetings of the bureau will not suffice I suspect.
In my view, the free flight classes are highlighting problems which
already beset all the thermal classes, F3B, J and K. Other more recent
electric classes will soon follow. Watch this space. Changes will
23 April 2015
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