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Radio
Control Model World - Nov '95
by
Stan Yeo
INTRODUCTION
I have
been flying radio controlled slope soarers for over 30 years. My
flying career pre-dates the venerable Veron Impala and Dave
Hughes Soarcerer. During this time I have introduced a considerable
number of people to the hobby. There is nothing more satisfying
than watching one of your 'pupils' complete the metamorphous from
raw beginner to accomplished slope pilot. As with all things before
this transition can take place there are a number of lessons / skills
to be learnt. The purpose of this article is to discuss briefly
what I consider are the properties of an ideal slope trainer and
the three most basic skills a budding slope pilot must acquire before
attempting solo landings if their current and future models are
to survive relatively intact on the slope beyond their maiden flights.
THE
MODEL
I always
recommend a rugged boxy rudder elevator model of 55 to 70 inches
span (1.5 to 1.75 metres) such as Chris Foss's Middle Phase,
The SAS Ace or the Phoenix Model Products Ab Initio
or Stage 2. I appreciate this may not be some peoples recommended
route to success but there are a number of reason for going along
this road, some of which are listed below:
1.
The models are generally very agile and manoeuvrable.
2.
If designed and built correct will take a lot of punishment and
are easily repaired.
3.
They allow the novice pilot to fly under supervision in a wide range
of conditions.
4.
They encourage the trainee to think through in advance what they
are going to do next (rudder control is not an instant control unlike
Ailerons and needs a certain amount of forward planning).
5.
They build confidence.
I know
some experienced flyers will disagree with this approach and would
advocate starting on an aileron model whilst others would recommend
a 2 metre 'floater'. I disagree with the 'aileron' approach for
a number of reasons the main ones being progress in the beginning
is much slower and requires much closer supervision but perhaps
more importantly, because the controls respond that much quicker,
it does not encourage such a disciplined approach to flying i.e.
thinking and planning ahead.
The
'floater' approach whilst not dismissed is not recommended as a
first model because of the limited range of conditions the model
can fly in and the limited teaching potential of the model. They
are however recommended as a compliment to the main trainer because
when the wind drops the 'floater' comes into its own. It is also
a more suitable model on which to develop thermalling skills and
conquer control reversal when flying towards yourself.
Model
flying is all about confidence and judgement. If the confidence
goes so does the judgement. Trying to start halfway up the ladder
or progress too quickly is a good way to undermine confidence and
extend the learning curve. All too often flyers discard their rudder
elevator trainers too soon with disastrous results. The R/E trainer
should not be abandoned until it can be flown in almost any conditions
with gay abandon, without crashing!
THE
SKILLS
The
three basic skills I have identified as the most crucial and the
ones that must be mastered before attempting a solo landing are:
1.
Being able to 'drive' the model forward in a shallow dive and at
the same time steer it in a straight line.
2.
Be able to execute tight, well co-ordinated, turns including flat
'eights'.
3.
Fly towards yourself and instinctively move the controls in the
correct direction i.e. be able to reverse the rudder (aileron) control
when the model is coming towards you.
Perhaps
a forth one should be included, that of being able to fly along
the ridge, close in, in light conditions using the wind to maintain
position relative to the slope.
1.
Driving Forward
This
is important because in general flying it is often necessary to
drive the model forward against the wind to make contact with the
best area of lift after launching, after an aborted landing attempt
or after being blown back during a turn or aerobatic manoeuvre.
It is also important during the final landing phase when the model
is turned into wind. Often at this critical moment the nose rises,
presenting the underside of the model to the wind and throwing it
into a deep stall from which there is seldom a recovery. It is also
important when building up speed to perform aerobatics. Here the
optimum dive angle must be maintained if speed is going to be built
up efficiently without too much loss of height.
One
reason that some flyers find this difficult, particularly Mode2
flyers (those who fly with the primary controls on the right hand
stick) is that the elevator stick is being held in a position against
the stick springs whilst at the same time moving the stick along
the rudder axis. Until the technique is perfected the elevator control
is inadvertently moved every time the rudder control is moved. The
technique here is to start off with the model pointing into wind
and put it into a very shallow dive and at the same time
gently steer it left and right. To terminate the exercise
face the model into wind and slowly release the down elevator until
the model resumes it's normal flying attitude. If the elevator is
released too quickly the excess speed will cause the model to stall.
If this starts to happen re-apply the elevator. This is all
part of the skill in driving forward. As stated previously, start
with a very shallow dive, this will minimise the speed build-up
and make it easier to end the drive forward. As you become more
proficient increase the dive angle. On a boxy rudder elevator model
the optimum dive angle will be around 30 degrees for maximum horizontal
forward speed. On a sleeker machine this angle will be nearer 15
degrees, any steeper, and whilst the model may be going faster it
is not going forward any quicker. In fact the forward speed will
start to decrease the steeper the dive becomes.
2.
Tight Turns
Like
the drive forward the tight turn is best built up to gradually i.e.
start with gentle turns that do not require any elevator input to
maintain level stable flight. With a good well co-ordinated rudder
elevator trainer it should be possible to initiate a gentle turn,
return the controls to neutral and watch the model complete 90%
of the turn without requiring further control input. Always start
at a safe height and a safe distance away from the slope. Tighten
the turn and see what happens. The nose starts to drop and the model
builds up speed (it is in a shallow spiral dive!). Stop the turn
and the model will go into a zoom climb due to the excess speed
built up. If this climb is not corrected in time with a dab of down
elevator the model will go into a deep stall. This often results
in complete loss of control for the raw beginner with the inevitable
results unless of course you have taken your guardian angel with
you.
Before
discussing the solution lets discuss the problem. The first action
when applying the rudder to initiate a turn is to cause the model
to bank. For the purposes of this article why and how this happens
is not relevant only that it does. The amount of bank is dependant
on the amount and how long the rudder is applied and secondary by
the wing dihedral angle. This is mentioned as very few novice flyers
relate rudder effectiveness to dihedral angle. As the model banks
the resultant lift develops a horizontal component and it this component
that 'pulls' the model around in a turn. Unfortunately as the model
banks the rudder starts to function as an elevator. This has the
effect of causing the nose to 'dig in' in the turn i.e. put the
model into a spiral dive. We all know that when an aeroplane is
in a dive it descends and gathers speed. The model will continue
in this dive as long as the rudder is applied and the model banked.
Neutralise the rudder, level the wings and the model suddenly has
excess flying speed, hence the zoom climb.
To
stop the zoom climb we must stop the speed building up in the first
instance by:
1.
As soon as the rudder starts to take effect gradually reduce the
applied rudder.
2.
At the same time slowly feed in a small amount of up elevator, just
sufficient to maintain the fuselage in its normal flying attitude.
The
secret lies in being able to recognise the normal flying attitude
of the fuselage, irrespective of the angle at which the model is
being viewed (orientation). You must build up a data bank in your
memory of the model in all sorts of attitudes so that you can automatically
recognise any one of them and maintain / make the appropriate control
inputs. This skill is only acquired by experience (stick time) and
in the early stages is often helped by mentally reminding yourself
during the manoeuvre what it is you are doing. Sounds silly I know
but when the model is coming towards you in an unfamiliar attitude
panic often sets in and raw instinct takes over invariably resulting
in the wrong control input.
Back
to the turn! Start practising with gentle turns and gradually build
up to very tight, highly banked, multiple turns. You should aim
to be able to complete consecutive full rudder, flat eight turns
and exit them without having to take recovery action!! Be responsive
to the airspeed of the model. In a tight turn the wings have to
work harder to produce the lift required to keep the model in what
we perceive as the normal flying attitude. If the model starts to
mush reduce the up elevator and open out the turn because if you
do not there is a danger of going into a spin or stalling into a
spiral dive. Always practice the turns at a safe height and distance
and initially under supervision. There is no substitute for height
and a forward position when recovering from an errant manoeuvre.
As a bonus you will find that being able to throw the model around
will increase your confidence no end which is why I introduce aerobatics
very early on when teaching someone to fly.
3.
Flying Towards Yourself
Learning
to fly towards yourself takes a little longer with a slope soarer
than a flat field model. Not because it is more difficult but simply
because, except for landing and ridge hugging in light lift the
model is invariably flying away from you. The first step in developing
this skill is to work out a strategy for automatically reversing
the steerage controls in your mind whenever the model is
flying towards you and practising it at home, preferably with the
help of a sympathetic friend! Remember it is only the steerage controls
(rudder and ailerons) that need to be reversed. Not the pitch (elevator)
control! How you remind yourself that left is right and right is
left is up to you but the mnemonics must be foolproof. One method
used to pick up a dropped wing is to move the control stick
in the direction of the down-going wing. Another for turning when
flying towards yourself is simply to repeat left is right or right
is left.
The
best way to practise is to fly the model as far away from the slope
as possible and then fly downwind directly towards yourself, initially
just keeping the wings level but later incorporating a series of
'S' turns. Always decide well in advance where and in which direction
your turn back into wind will be. The biggest danger in making this
turn is not normally in the direction of the turn but in making
the turn too late. I am often heard to say when giving tuition on
this aspect of flying "I don’t care what decision you
make but please make one!" Naturally on these
occasions there is usually some emphasis in my voice! Flying a slow
floater, in light lift, is an ideal way to learn this skill. Benign
conditions with plenty of thinking i.e. time to correct mistakes,
is the order of the day.
SUMMARY
In
writing this article I have deliberately avoided the aerodynamic
theory in an effort not to confuse the target reader. All this
article has attempted to do is help the ab initio pilot acquire,
with a little understanding, the three most basic skills needed
before attempting a solo landing. Practise the control inputs at
home and set flying targets on the slope. Remember practise makes
perfect.
FOOTNOTE
Should
you be interested and have access to back issues of this magazine
(if not they are available from Traplet Towers) a number of other
associated Prepare articles have been written, namely
Prepare - to Fly (Feb 95) to Land
(Jul 94) for Lift-off (Apr 94) for Slope Aerobatics
(Nov 95).
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