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AT THE END OF last month's "From the Ground Up" installment we had the
model at the taxiway with its engine at idle. Leave it there for the
time being; I'm going to discuss model flight operations in terms of
where we fly and what we fly to reduce the level of risk.
In the next
article I'll write about flight-operations safety from the perspective
of how we fly, including methods, techniques, and good flight-safety
practices.
Level of Risk: Everything we do in our lives carries some
risk. If you are a newcomer to flying models or an experienced
old-timer, you should fully appreciate the safety concerns involved with
piloting an RC aircraft. That knowledge can assist you in preventing
injury to others and yourself during model flight operations.
As the old
saying goes, "Forewarned is forearmed." If you know about the dangers,
you have a better chance of avoiding an accident and the potential
consequences.
The primary concern in model flight operations is an
out-of-control aircraft striking someone. A secondary concern is
property damage caused by an errant airplane. A third is that if you
lose control of the model, you destroy your beautiful creation.
Loss of
control and the subsequent crash may occur for a variety of reasons. The
pilot could make a mistake and cause the crash. A radio receiver battery
could fail. A control surface could detach. The model may be flown out
of radio range. A servo could jam or fail to operate properly.
In the
first two articles of this series I described the levels of safety
action we apply to aeromodeling to minimize risks and prevent injuries.
As a basis for further discussion, review the accompanying Table 1 (on
page 4): "Aeromodeling Safety Risks and Defense."
Reading from left to right
takes us from a low to high level of consequence—a first-aid injury to
major injury or death. Reading from bottom to top we see that the safety
action levels increase as the probability of an occurrence increases.
Where risk level is low and the likelihood of an event happening is low,
we may only need to ensure that we have the right attitude.
Let's
consider sawing a piece of thick balsa with a razor saw. If we slipped,
the resulting injury would be a cut and would be addressed by first aid.
If we considered an out-of-control, 6-pound aircraft moving 60 mph with
a propeller spinning at 12,000 rpm on the front, we are looking at a
safety risk of major injury or death.
In the latter case we would apply
all the levels of safety we could muster. We would ensure the right
attitude, prechecks in the preflight inspection, and backups such as
dual and independent servos for ailerons or elevator to prevent the
out-of-control situation.
We would also, by flying-field design, use
isolation by physical separation of the overflight area and spectator
and pit areas to protect us from injury. In extreme situations such as
air combat, we would increase the separation between the flight
operations and spectators and use barriers—i.e., hard hats—to protect
the pilots.
Perhaps you are thinking, "No problem. I fly park models;
they only weigh 13-16 ounces." A baseball weighs roughly that much. Have
you ever been hit by a baseball that missed your mitt? It hurts, doesn't
it?
A missed ball can make you appreciate the combination of mass and
speed as momentum. Even a small object such as a park flyer, traveling
at a significant speed, can hurt whomever it hits.
Several weeks ago I
watched a pilot fly a new F4U Corsair park flyer. It weighed only 15
ounces, but at full throttle it flew approximately 80 mph. If hit by
such a model gone out of control, you could sustain a serious injury.
Fliers have lost control of and been struck by their own models. I
almost did that once while I was learning to fly. Any contact between
flying models and pilots or bystanders must be prevented.
So how do we
reduce the safety risk of an in-flight control failure? Or if the
failure is not prevented, how do we prevent injury to a person? There
are three methods to reduce the risk to an acceptable level:
1) Organize
the flying activity in safety zones for different phases or activities
(where we fly).
2) Place limitations on the model size, weight, and
equipment (mostly what we fly).
3) Establish and apply appropriate
flight-operation safety standards (how we fly). This month I'll address
the first two methods.
Click on photo to view large image with caption
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