From NOTAM, Lewis Jordan, Editor
Crashless Flying
Fly RC long enough and you will
experience a crash. However, some pilots seem to
crash often—too often. Let’s explore some of the
causes of crashes and perhaps minimize crash
opportunities.
Split Second Delay Crashes: High speed
creates high loads on the plane’s control surfaces
and servos, causing a possible split second delay of
control after a stick input. A split second delay is
all that is needed when your plane is in some
maneuver heading toward that ground at 100 mph (147
feet per second). Point the transmitter antenna at
the airplane you can create a cone of science at
your receiver, which can cause a control response
delay.
Pilot Orientation Crashes: Another cause of
crashes is a non-mechanical one: pilot orientation.
If you are low and fast and lose orientation, expect
a crash. Have your airplane flying level or in an up
attitude while flying close to the ground.
Distraction Crashes: Another non-mechanical
cause: distraction. If you allow yourself to be
distracted, even for just a couple of seconds,
you’re likely to crash. If you were stung by a bee,
step on what you think could be a snake, or have
another critter eating your pant leg, put your plane
in a series of tight loops with full up elevator,
then take care of your business and your airplane
will still be there when you can tend to it again,
not two miles down the range. This may be overly
simplistic, but you get the general idea. All pilots
get distracted sooner or later. Think out in advance
what you will do so your fingers will react when you
do get distracted.
Aerobatic Crashes: Among the many maneuvers
pilots enjoy, snap rolls are at the top of the list.
Just be prepared for that fatal snap of a control
surface during this maneuver. Pilots usually enter a
snap full bore with full deflection on all control
surfaces. This can load your airplane up to as much
as 30 Gs, plus air drag loads. Inspect your airplane
carefully after doing this violent maneuver.
Elevator Crashes: Let’s spend some time with
the elevator. This is the most important crash
prevention control on your airplane. First, the
elevator itself must be built from good material.
Too hard and brittle is not good; too soft is not
good either. In today’s world, the high-quality ARFs
take care of this. Use your best servo in the
elevator. I don’t like the standard servos on any
function except the throttle.
Buy some good servos for your primary control
surfaces. Next, use only strong, stiff rod linkages
from servo to the control horn. Fiberglass rod
systems are great for long runs. Strong, stiff wire
works well for short runs. It’s very important to
keep the bends in the wire to a minimum. Lots of
pilots use them, but I don’t like the flexible Nyrod-type
systems. Any movement of flex here could allow
surface flutter, and also cause a split-second delay
crash. The plastic clevises and control horns
supplied in many kits leave a lot to be desired. Get
these items from Du-Bro or Hangar 9.
Dirt and grit will weaken the plastic clevis pin
very quickly, and generally they are too soft and
flexible. Consider using metal or the super strong
carbon fiber clevises and control horns.
Metal-to-metal contact is taboo, but most metal
systems have an insulator to prevent any
metal-to-metal contact. Always install a rubber or
nylon safety “keeper” on this and on all your
clevises.
Crashes are extremely frustrating and expensive.
With a better understanding of what causes crashes,
we can more easily prevent them.
Servo Damage Crashes: Servos can be
unknowingly damaged by a hard landing or by bumping
a control surface while loading the airplane into a
car. What happens is the servo’s gears get cracked
but it continues to operate until subjected to
flying loads, then the gears break. After a hard
landing or a bump, and from time to time, check your
servos by applying slight hand pressure to the
control surfaces while operating the servo. If it
takes hand pressure, it will usually stand up to
flying loads.
Take-off Stalls: The airplane will very
likely turn to the left during take-off. One method
to prevent this type of crash is a high-speed
takeoff run and a shallow climb after liftoff until
maximum climbing speed is reached. Use rudder to
maintain direction with very careful use of ailerons
to stay level. If the engine quits on takeoff, don’t
try to turn back to the runway. Keep the airplane
heading into the wind and make your landing.
Landing Turn Stalls: A very common pilot
error occurs while setting up a landing approach and
performing too steep a turn from downwind to final.
Airplanes stall at a much higher speed in a bank,
and a steep bank into the wind will quickly slow the
airplane and cause it to stall. Keeping turns
shallow on your approach will help prevent this type
of stall, and using rudder to turn will also help
keep the turns shallow and reduce the additional
drag of the ailerons. This becomes especially
critical if landing dead stick.
Routinely check and tighten motor and engine
mounting screws. Carefully inspect and test all
flying surfaces. Pull on them to make sure the
hinges are secure. Q
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