R/C Aircraft Safety-Propellers

R/C Airplane Propeller Safety

This photo looks pretty harmless.  However, if you have ever came into contact with one of these little babies while they are spinning at 15,000 rpm, you will remember it!  I will never forget my Dad’s misfortune.  I myself have been bitten and nicked by spinning propellers more than once.  Mostly before the days of electric starters and remote needle valves.

The fact is, our hobby or sport uses an exposed, rigid, and sharp blade, spinning at a high rate of speed.  Respect and alertness are mandatory if you want to keep all of your fingers.  If you continually ignore safety, you or someone close to you will be injured eventually. By adopting good safety practices we can minimize risk and enjoy our wonderful sport for many years.

The most destructive type of propeller injury, aside from being struck by a flying aircraft, is when the engine is operating at or near full throttle.  At full speed, a .40 size two stroke engine with an 11-6 nylon propeller can generate as much power as a 10″ table saw.  Just as a table saw demands your respect and attention, so does an aircraft propeller!

Before you mount your propeller or even start your engine, you should take a moment to review some basic pre-flight recommendations for propeller safety.

Inspection and Preparation

After purchasing a new propeller or rotor blade, or before installing a used one, take a few moments to inspect and prepare it.  First do a visual inspection.  Look for any obvious nicks or gouges.  Flex it gently back and forth along it’s length.  Check for cracks.  Primarily wooden propellers are susceptible to cracking, however I have had a composite prop completely disintegrate during normal running of the engine.  If you do find any damage, other than some minor scuffs at the tip, discard the propeller immediately.

After visual inspection, have it x-rayed at the local emergency room to check for any internal imperfections…just kidding!

Another technique for propeller safety is painting the tips of the propeller with a contrasting color.  it will add a bit of visibility.  Remember to use a fuel proof paint and to balance your prop.  Or just shop around for a commercially produced version.  Many manufacturers are already including tip paint for safety.  Such as this “master airscrew” composite type.

Choosing a wooden propeller instead of a nylon composite propeller is also a good way of reducing the severely of an injury if you are stuck by a propeller.  A wooden  prop will still hurt you, but it can’t compete with the ability of a composite prop to slice through flesh, tendons, nerves, and bone.  Unfortunately, wooden propellers are very susceptible to damage.  Although I like the look and added safety of a wooden propeller,  you just can’t beat a composite prop for durability and performance.  If you choose to use a composite propeller, do your self a favor and take a moment to remove the razor sharp flashing that comes from the factory mold.  It will not adversely effect the performance.  Again, this small step may help reduce the severity of a cut.  I like to use a very fine sandpaper to just knock off the edge.  Make sure you do not alter the actual shape of the propeller.  I also use this time to dull down the surface near the tips in preparation for paint.

Balancing

A balanced propeller is essential for safety, performance, and to reduce wear and tear of your engine bushings/bearings.  An unbalanced propeller causes vibration.  Vibration is an enemy of aviators.  Glue cracks, nuts loosen, and electronic equipment fails.  Luckily, most propellers come from the factor fairly well balanced.  Many people just skip this step.  They just take the propeller out of the package, mount it to their engine and go flying.  However, I don’t recommend this.  It does not take much work to balance a prop.  I use a commercially made version from TopFlight (like the one shown in this photo).  It can also be used to balance ducted fans and R/C car wheels.  I mostly use my tip paint to make up for any deviations but there are many techniques for properly balancing your prop.  Click here to view the TopFlight balancing manual.

o Always have someone hold onto your model while you starting it!

o After starting, move around behind the prop to remove the glow
plug battery and to make needle valve or engine adjustments!

o Never, under any circumstances, reach over a running prop!

o Be concious of the prop arc! Don’t let spectators stand in line with
or in front of the spinning propeller, and don’t stay there yourself
any longer than necessary.

o To make the ‘arc’ visible, paint the tips of the propeller with a bit
of white or silver paint.

Needle Valves

Before commercially manufactured remote needle valves were standard on most average two strokes, many a modeler had at the very least been “bit” by the spinning blades of their engines while attempting to adjust the needle valve. (myself included!)  If you are in the market for a new engine, consider a remote valve.

Anything that keeps you fingers away from a spinning propeller is a good idea to me!