Control Model World - Nov '95
by Stan Yeo
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.
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
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
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 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
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
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 dont 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.
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.
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)