Safety Comes First - 2009/08

I LOVE TO hand launch a model. It gives me a closer connection
with flight to physically send an airplane soaring into the sky.
Conventional tractor-type aircraft with the propeller in front (the way
nature intended) respond nicely to hand launching, as long as you give
them the proper flying speed.
Since this is the safety column, you know that this discussion will
veer into launching some not-so-easy types of models. A new trendy
thing these days is to fly RC electric-powered jets with either a pusher
propeller or one mounted in the middle of the model. They fly well and
are convincing in flight, but getting them into the air without
bloodshed can be tough.
A standard 1930s overhand-launch technique will bring fingers and
propeller together in an unpleasant way. Some builders add a special
strake on the airplane’s belly as a holding fixture. Others launch their
jets from the top, holding the fuselage and giving an underhand fling,
hoping that they can pull their hands back quickly enough to avoid the
propeller tips. Yikes!
One creative
strategy is to use a
helper who holds
the wingtips and
push the airplane
away with both
hands. This leaves
the spinning
propeller closely
centered to the
launcher’s chest, but
at least all 10 digits
are clear.
I do not claim to
have the answer to
this situation, but
too many pilots
have shown me
their scarred hands.
We have to give this
some thought.
In the early days of marginally powered electric models, it was
common to use a bungee launch. This added another exciting element
to the mix: the stored energy of a giant slingshot.
For better or worse, at least we have more motor power these days.
This high power-to-weight ratio is the very thing that allows such
creative new airframe designs, which bring new problems to solve.
The picture of pilots mass launching their RC Combat F-22 jets
shows a variety of techniques. Nobody got nicked, so apparently each
launch style can be used safely.
Please contact me with your wisdom, ideas, and opinions about
hand launching these finger-biting little models. If there is some better
way, we all want to know about it. I have more to write about that jet
mass launch later.
One way to escape the pusher-propeller, finger-fillet situation is to
do away with the propeller entirely and use those great new Rapier
rocket motors. These are the next generation of Jetex-type power
plants, but are much more reliable than Jetex.
FF pilots can enjoy the sight of their models zooming into the sky
with a faint smoke trail and the distinctive sound of a tiny reaction
motor. Launching them can be slightly less romantic. Again, a standard
overhand toss is not recommended because the pilot gets a face full of
hot exhaust.
I managed to complicate things by building a dual-powered
Ercoupe with a rubber motor for the propeller and a Rapier underneath.
Yes, there really was a full-scale prototype. It was used to develop the
system.
My model flies sweetly but requires more
than two hands for motor ignition and launch.
I found that I could get away with a hand
launch if I tossed the airplane across my body
to my left instead of overhanding it straight
away from my face. That way I end up
standing next to the flight path instead of
directly behind the model. This works only
for small, lightweight models, but it does the
trick for me.
My friend, Ted Davis, built a sleek profile
HA-200 jet trainer for Rapier power. Look at
the picture of this airplane climbing out and
get a load of the exhaust trail centered on
Ted’s face. If you look carefully, you can see
that he is wearing his Zurich sunglasses.
These not only provide wrap-around coverage
from glare and dust, but they are also rated for
impact protection.
Although these fine sunglasses are not
recommended for direct exposure to rocket
exhaust, they provide excellent eye protection
at the field or anywhere. I use them, and there
are none better. Zurich gets an enthusiastic
plug here only because its products and
service are so good. I paid retail for my pair.
Zurich frequently advertises in this
magazine and you can visit the company’s
Web site to see its new line of Zurich Pilot
EXtreme Glare Sunglasses, which are
optimized for use by aviators of all types.
These new glasses have wraparound lenses
for peripheral vision, but they will not fit over
prescription glasses as the classic style does. I
have read too many eye-injury reports, so
please obtain and use good protection for your
sight.
Where was I? Oh yeah, Ted Davis was
hand launching a Rapier-powered model and
got a face full of smoke. There is more to that
story.
Ted and I were using motors from the
same package, but his were getting “burnthroughs,”
where exhaust came through the
side of the motor casing. Mine were running
fine. He got a little tired of seeing his flights
end literally in a smoking hole in the ground.
We finally determined that, although the
older batch of motors was somewhat prone to
burning through the side of the casing, our
lighting technique had a lot to do with it. We
were both using a standard electronic lighter,
but I was carefully inserting mine dead center
into the rocket nozzle, while Ted went in from
an angle and lit his motor off center. We
confirmed this by doing an autopsy on a
burned-through motor.
Shorty’s Basement now carries an
upgraded motor style that seems to have cured
this problem. The company’s Web site is in
the “Sources” list.
I’ve seen pictures and video of some new,
extra-small RC turbine engines being flown in
Europe. These little power plants are often
mounted on the tail of a small delta-wing
model, which is hand launched and belly
landed on grass. The current AMA guidelines
for turbine-powered models do not allow for
this type of model, because of requirements
for rudder control and landing gear steering
and braking.
There is talk of altering these rules to
allow the smaller jets, but one serious issue is
how to hand launch the things without
receiving a facial barbecue. Apparently it can
be done, since the pilots in the videos still
have eyebrows.
Another issue involves landing these little
jets with no undercarriage. A grassy field is
one thing, but what about landing on winter
snow? The jets might skid a long way while
they are essentially out of control.
Much smarter people than I are working
on this matter. If there are any changes, this
magazine and the AMA Web site will have
the news first.
Here’s the information about the F-22 masslaunch
photograph. These little airplanes are
the ones I mentioned last month, redesigned
by Ron Knight for his Knight Fighter RC
Combat event.
This is possibly the safest Combat event
ever. I watched these pilots fly and fight until
their batteries wore down, with only the
slightest midair damage during the match.
The other picture shows the Combat zone
with five airplanes visible and no casualties
yet.
It seems that these foam jets turn on a
dime and accelerate quickly on their electric
propeller power, so it is hard to bring two of
them together, even deliberately. They are
easily repaired, but may never need it. As of
press time, the following are the latest rules
for Knight Fighter Combat.
• The event is for 30-inch-long F-22 (Knight
Fighter) aircraft.
• 6 mm or thinner Depron foam must be used,
except for one carbon-fiber wing spar.
• Except for the spar, no glue is used—only
tape.
• Only a GWS 5030 propeller is permitted.
• The aircraft’s maximum weight is 8 ounces.
After the exciting, but uneventful, first
match using these rules, I strolled around the
flying field and noticed some battery packs
charging from a car battery.
The unusual thing was that the car engine
was running at the time, with the hood up and
nobody at the wheel. It was parked in the lot
at a busy RC field, and nothing bad occurred.
What do you think about this?
I was trained to avoid a situation such as
this for several good reasons. I’ve heard about
cars going for a drive on their own when left
running and unattended. I once saw a driver’sside
door sheared off by a post when an
unoccupied vehicle cruised by in reverse.
When we have to “static run” truck engines at
my company, we use extra-large wheel
chocks and all other possible precautions.
I think that charging an RC power pack is
a small drain on a normal car battery
compared to starting the car engine, and
running the engine is unnecessary, but I might
be wrong. If you know more about this than I
do, please hook me up with the electrifying
truth and I’ll share it with the world. MA
Sources:
Dave Gee
Box 7081
Van Nuys CA 91409
Academy of Model Aeronautics
National Model Aircraft Safety Code
www.modelaircraft.org/files/105.pdf
Zurich Sunglasses
(800) 533-5665
www.zurichsunglasses.com
Shorty’s Basement
(740) 225-8671
www.shortysbasement.com