ON THE SAFE SIDE
Propeller Strikes and Arming
Switches
by Jim Tiller,
Insider Safety Column Editor
Never, Never Stick Your Finger in the
Propeller
Before I took the job as AMA Insider safety
columnist, I remember lamenting to my beautiful wife
that it might be hard to make the column
interesting. I remember saying, “Just how many times
can you tell someone not to put his finger in the
propeller?” On a warm Friday afternoon in late
August, I found that the answer. After 30 years of
flying airplanes, I had my first encounter with a
spinning propeller.
I was
with a bunch of flying buddies at our preferred
float-flying spot, enjoying the late summer morning.
It was the first flight of the day on my .30
four-stroke powered Newbie float plane. As the
flight progressed, I could see the motor was not
developing full power, so I made an early landing
and taxied back to do some engine adjustment.
With
another flier holding the airplane, I was adjusting
the high-end needle setting when my hand somehow
wandered into the full-throttle propeller. In an
instant, the motor stopped and the blood began to
run. The cuts were quite serious and we immediately
went into damage-control mode. We had a first aid
kit along, but it was a small one. We applied
pressure and bandaged the wound with the only high
strength tape available, a roll of black electrical
tape. With the blood flow temporarily stopped, I
made my way to the emergency room for a two-hour
stay and about 14 stitches from a very competent and
friendly emergency room doctor. This little lady
looked, to me, to be about 14, but she did a great
job sewing up four separate propeller strikes on my
right hand. She mentioned that I was her very first
prop-strike victim and I replied that it was also a
first for me.
Fortunately, there was no permanent damage except to
my pride. I managed to hit the blade with the flat
of my hand rather than the fingers. That stopped the
propeller and reduced the number of strikes
somewhat. It is now almost two months later and I
have just the scars to remind me of my errant ways.
Who do I have to blame? No one but myself—it was a
preventable accident. In hindsight, I lost what the
military calls “situational awareness.” I was so
focused on the job at hand (no pun intended), which
was tuning the engine that I totally ignored the
close proximity to the spinning propeller. I know
better. On that day, evidently, I did not know
better and all it takes is one lapse in
concentration. That is the lesson I leave with you
and why I am sharing my experience.
A second observation. This little four-stroke is my
smallest motor. Maybe that is why I was not as
conscientious as I might have been. As you can see,
small propellers do just as much damage as big ones.
A third observation; and one that my flying group
has now corrected. Our first aid equipment was
inadequate. We have since purchased a much better
equipped first aid kit and put it in the storage
locker in our retrieval boat. That kit now matches
the one we have at our field. By the way, it still
includes the roll of electrical tape. I can vouch
for how well it worked at compressing the bandage
over the wound.
A fourth observation. I have my flying buddies to
thank for the help and assistance. It is important
to surround yourself with fellows who are safety
conscious and who can be trusted in an emergency.
And last: Never, never stick your finger in the
propeller.
Arming Switches on Electric Airplanes
This past summer, I learned of a couple of instances
where an electric airplane started before the pilot
was ready. In one instance, the pilot turned on the
transmitter but had it improperly set to another
airplane program. Evidently, the programmed airplane
had the throttle reversed and when the airplane
battery pack was plugged in the motor engaged. Most
good ESCs are supposed to prevent this by making you
put the throttle to its lowest setting before
arming. I’m not sure what happened here.
In the second instance, the airplane was on the
bench and the transmitter had yet to be programmed.
The throttle stick was in the mid-range. Once again,
when the battery was plugged in, the motor engaged.
An arming switch is a good way to prevent any
accidental motor start on an electric airplane. They
are most feasible on larger motors, but many
electric gurus say they can be fitted to an airplane
of almost any size.
Another good reason for the arming switch is to be
able to plug in the battery and then prepare the
airplane for flight. Many times there are cowlings
or hatches that have to be secured or other
preflight preparations to complete. Why do that with
the battery and motor armed?
A number of commercial arming switches are out
there. They are not very expensive and are easy to
use. Your local hobby shop can surely provide you
with one.
If you want to tackle the project in your shop, just
peruse the online forums and you will find lots of
pictures and schematics. Here’s one in the RCGroups
forum:
www.rcgroups.com/forums
/showthread.php?t=1335070.
And here’s an even better idea. These two clubs have
posted pertinent information and how-tos on their
websites for their members and others to use. I
think that is a great idea. It would be a simple
matter to create a link on your site to these
documents or write one of your own.
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