nuts & bolts
maintenance & restoration
Time and hours important
JEFF SIMON, EAA 478233
When I think about propeller maintenance, I think about Rodney Dangerfield. Propellers endure high stress. The blades travel at speeds in excess
of 500 miles per hour while enduring 10 to 20 tons of centrifugal force acting to pull the blades from the hub. While
this is happening, the blades are slowly eroded by sand,
rain, and the occasional small rock. Props even get manhandled on the ground when pulled on to help park the
aircraft. Then, they go largely ignored when it’s time for
routine maintenance or when reaching the recommended
time between overhauls (TBO). Props get no respect, as
Rodney would say.
Props deserve better. After all, you can practice engine-out landings to your heart’s content, but it won’t do you
much good if you and your propeller part ways in flight.
The vibration resulting from a propeller blade failure can
easily tear the engine from its mounts, rendering the aircraft uncontrollable.
Every preflight checklist should include a careful inspection
of the propeller. Nicks and dings from rock strikes are easy to
see and should not be ignored. Even small areas of damage
can represent stress points that can lead to cracks or corrosion. It pays to be vigilant and attend to small areas of damage before they become big ones.
Making minor repairs to propeller blades is not a particularly challenging task, and FAA Advisory Circular 43.13-1B
is an excellent reference for understanding blade repairs.
However, dressing prop blades is not legal preventive maintenance, and it’s definitely not for novices because technique
is very important. Every propeller blade has dimensional
limits that restrict the amount of metal that can be removed
during repairs before the propeller becomes un-airworthy.
It’s easy to remove aluminum from a propeller blade and
impossible to put it back. Therefore, you need to proceed
with caution, using the following basic steps:
• Using a hand file, carefully remove the damaged material until you reach the bottom of the nick, ding, etc. None
of the original damaged surface should be left, but the
minimum material should be removed to accomplish this.
Corrosion is more dependent on age and
environment than on operating hours.
• Dress out the repaired area, making a smooth transition into the surrounding material. The general rule is to
dress out the repair to an area 10 times the depth of the
damage. For example, if you have to file down 1/8 inch to
get to the bottom of a nick on the leading edge, you must
dress out the repair 5/8 inch on either side of the center of
the repair for a total repair span of 1-1/4-inch. Try to maintain the original airfoil shape, blending the repair into the
• Remove file marks with emery cloth until the surface
is smooth. Then inspect the area carefully, using dye penetrant to reveal remaining marks or cracks.
• Treat the repaired area with Alodine and paint to protect against future corrosion.
• Use emery cloth to smooth leading edges as necessary
and apply a thin coat of oil to help resist corrosion.
Maintenance on constant-speed propeller hubs is far
more complex and, other than routine lubrication, should
be performed only at a propeller maintenance facility.
Lubrication of the propeller hub is very important because