Sydney Lenssen
23 April 2015
Sydney Lenssen

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 
or loses.

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 
flying sites.

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 
other nation.

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 
be fun.

Freeflight changes

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-
end expert.

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 

Sydney Lenssen

23 April 2015


Back to - Back to gossip index