In July 2010 the South African television show
"Carte Blanche" visited Jonker Sailplanes and
produced an excellent documentary.
Take a look as the show host, Bonita Gorrie-Nuttall,
speaks with Attie, Uys, & Tienie Jonker and subjects
herself to a two-seater glider flight with Uys.
The documentary transcript:
Wilbur Wright described flight as: 'A sensation of
perfect peace mingled with an excitement that
strains every nerve to the utmost.'
Uys Jonker (Jonker Sailplanes): 'You almost feel
like the aircraft has got a personality, you've
constructed with your own hands, you feel attached
to it, almost emotionally attached to the aircraft,
like some live object that we've made.'
Bonita Gorrie-Nuttall (Carte Blanche guest
presenter): 'What would you expect to find in
Potchefstroom? Hordes of students, beautiful oak
trees? But you probably wouldn't expect to find two
brothers with a boyhood dream that led them to
create a high-tech flying machine that's now taking
on the world. And no, it's not the Wright brothers -
it's the Jonker brothers.
Attie Jonker (Jonker Sailplanes): 'We grew up in a
family where it was gliding family. So, every
Saturday we were in the airfield flying or playing
around with little kids and then my father decided
to build his own glider. So we grew up in the garage
and house environment where continuously we were
talking and building gliders. And that was the
normal thing to do.'
Attie Jonker and his brother Uys were just boys when
they first took to the sky. Their father Tienie was
a schoolteacher in Christiana in the Transvaal.
And, for him, gliders were the cheapest way to feed
his passion for flying.
Tienie Jonker (Jonker Sailplanes): 'On the salary of
a teacher there was no way that I could afford to
buy a commercial glider. So I looked around and I
decided, 'Well, if you can't buy it you must build
it.' And I decided to build my own glider.'
Tienie purchased some plans from a designer in
America and slowly but surely the Miller Tern began
to take shape.
Tienie: 'I didn't want to take short cuts. We
imported wood from America, plywood from
Scandinavia, the special steel also from America,
all the nuts and bolts. And for the next five years
I was working away in my garage in all the spare
time that I had. And it took me five years before I
made the first flight.'
From a young age Tienie's boys learned all about the
finer points of glider flying and Uys clearly
remembers his first solo flight when he was only 16.
Uys: 'It was just awesome because suddenly you're
actually still a boy and you're sitting in the
control of a fairly large aircraft at that stage.
And nobody is telling you what to do... all the
decisions you have to make yourself.'
Bonita: 'When did you eventually start thinking,
'Okay, this is something I can actually make a
career out of'?'
Attie: 'It was never a career decision thing. It was
always a dream-chasing thing. I was in about
Standard 5... 6... 7 when I thought I could redesign
my dad's glider into something more modern. So, I
started looking at the plans and drawings and
started reading engineering books and realised this
is more difficult than it seems. And at that point I
decided I will study engineering for the sole
purpose of designing my own glider.'
Bonita: 'And did you take your brother along for the
ride? How did he become involved?'
Attie: 'Uys was always more sports involved, I was
always... the gliding thing was my thing. And
eventually Uys told us he joined the gliding thing
because he thought me and my dad had something going
[that] he was missing out on. So, he started flying
and eventually he latched onto the thing and became
much more passionate than I was about the thing and
told me, 'Let's do this!''
And so in 1999, with a dream of building the perfect
glider, the brothers teamed up with an enthusiastic
engineering student, Johan Bosman, who later became
their aerodynamic engineer. Together they started
the JS1 project.
Bonita: 'This little factory in the North-West
started out as a glider repair and refurbishment
business, but today it produces internationally
sought after high-tech gliders.'
The prototype was funded by the repair business, the
DTI and the University of the North-West. It took a
decade to complete, and earned itself the name the
Uys: 'The amount of work is absolutely a revelation
- we did not realise by a long shot how much work is
involved in this.'
Uys: 'This fabric [on screen] consists out of
Kevlar. Now we use this in the cockpit area. What
this does is its like shatterproof, the Kevlar keeps
it all together.'
The JS1 Revelation was 10 years in the making, and
the science behind it is was being delicately
refined every step of the way.
Attie: 'We started with a blank piece of paper
without any legacies. We said, 'We will continue to
design this thing until it's the best.' Refine,
refine, refine - a half a percent here, a quarter of
a percent improvement here, we really refined to the
point where we thought further refinement is not
Uys: 'This little section is the winglet. The
winglet is a very important part of the aircraft.
This is getting bonded into position at the correct
Then came the ultimate test - would the JS1
Revelation stand up to the stringent requirements of
the Civil Aviation Authority?
Uys: 'Certification is all about proving that you
meet the specification. Now the specification is
quite a thick document and each little paragraph of
those has to be addressed and proven without doubt
that we make the specification.'
During testing the design performed outstandingly to
the point where, as this wing stress test shows, the
test rig actually failed (rig breaks) at a force of
two tonnes, which is equivalent to a 16G load -
double the certification requirement.'
Attie: 'Well, you need to show that every piece of
the structure is 50% safer than ever required in
And the team did just that and were awarded the
first ever certification of its kind in South Africa
Bonita: 'The JS1 Revelation is the 'Formula 1' of
glider technology. It's a racing machine that uses
solar energy to soar for hundreds of kilometres at a
time, at speeds of up to 270km/h. This baby is at
the pinnacle of aerodynamic design.'
Word has spread in the international community and
the orders are starting to roll in. Already Jonker
Sailplanes' 13th glider is set to spread its wings.
Uys: 'This aircraft is not in final assembly; it's
going to a client in England. We hope to ship it
during next week. We expect the test flight to be
Bonita: 'How much do one of these retail for?'
Uys: 'The basic model is around €75 000, so it's
around R800 000 without instruments and
The 18m wingspan class of glider may seem like an
expensive toy, but those who race it take the sport
Bonita: 'Attie, how safe is the glider?'
Attie: 'Structurally a glider is extremely strong. I
mean, if you take for example, a glider like this
can take a 12 - 14G pullout whereas with a Boeing
they limit it to 4G. So it seems it's about 4X
stronger than a commercial aircraft.'
Bonita: 'What's it like in the air there, just you
and the glider?'
Uys: 'No, it's amazing! Why don't you go up and I'll
give u a bit of a feel?'
The JS1 is a single-seater, so Uys took me up in a
twin-seater training glider. Little did I know what
I'd signed up for.
Uys: 'Parachute first.'
Bonita: 'Oh my hat... okay. Mom - I love you.'
A quick safety briefing and the glider is attached
to a little Cessna aircraft that will be towing us
into the heavens.
The tow-plane would take us up to about 1500ft. Uys
will release the towrope and then we're on our own -
no engine, just the wind beneath our wings.
Uys: 'Now that's the beauty of aviation - gliders
are designed that they have such efficient profiles
that they don't need a lot to stay up. So what we're
doing basically is we fly the aircraft and when we
encounter lift, that is rising air. We start
circling like any vultures or birds that you will
see and then we're slowly going up - sometimes
fairly quickly, we may go up as much as 5m per
second or more on good summer days. And then we
convert this height again into distance by gliding
slowly down. So the whole gliding flight consists of
climbing up like the birds and then flying.'
Bonita: 'We're going up!'
The beeping noise is an audio climb indicator lets
the pilot know when the aircraft is ascending. And,
as I soon discovered, Uys had a few tricks up his
Uys: 'What about one loop?'
And that was called an inside loop with G-forces
equivalent to a space shuttle launch.
Bonita: '(hand shaking) I'm not kidding.'
After that I felt I'd had enough and Uys offered to
take us in for a gentle landing. Without an engine
this is a skill that requires extensive training
and, naturally, Uys aced it.
Uys: 'Bonita is okay, it was just a little bit of
Back on mother earth it took about 20 minutes for me
to find my land-legs again.
Uys: 'The scream was so hard...'
Bonita: 'Did you hear me scream, you must've heard
Uys: 'I think they heard you down there.'
Attie: 'Oh, did you do a loop? (laughs)'
The JS1 Revelation has won a number of local and
international competitions but Attie still dreams of
the big one.
Attie: 'Well, if our glider could win a world
championship that would be spectacular.'
Bonita: 'Do you think that your glider the best in
Attie: 'I don't have to think anymore - it's now
sort of a known fact. Internationally it's the best.
There are different classes and in its class it is
the best, it's a known fact, which is a great
In just three years the factory has expanded to
employ a staff of 50 - and it's growing.
Bonita: 'How do you feel about the fact that it's
affected so many people's lives?'
Uys: 'Sometimes when you can just stand back and
look at what's been achieved over a few years then
you do feel proud. You really feel you have achieved
something in your life that was a dream.'
Attie: 'The best part is when another pilot gets out
of the glider with a big smile and tells me it's the
best glider he's ever flown - that's the best!'