Without a method of converting the power produced by the engine into useful thrust an aircraft would just be sitting still and creating a lot of noise and not get anywhere. All that power generated by the pistons and the rotating crankshaft is fed to the propeller to create useful thrust.
But to do that efficiently and reliably the propeller needs proper maintenance to keep it in tip top shape. So that it can remain in safe and reliable service for years to come. It should be noted that controllable propellers need a bit more care than the fixed types.
For most pilots the preflight inspection is the time they see and feel the propeller from a very close distance. This is your chance to take a good look at it and make sure its in flyable condition. Below we describe the things you can do to help keep it that way.
The preflight inspection by the pilot is the moment to catch any damage to the propeller early on. Give it a good look all over and feel with your fingers for any damage (careful). Any problems caught on early means that repairs are relatively cheap. Cleaning the aircraft and propeller after every flight makes sure corrosion (from bugs) does not get any chance.
FAA AC 43.13-1B describes what can and may be done to file out, or dress, the propeller. There are some dimensional limitations you need to be aware of. The procedure is not very difficult, have an A&P (or LAME, Licensed Aircraft Maintenance Engineer) explain it to you, and it requires a hand file, emery cloth and some light oil to clean the blades. This will work only with an aluminum propeller.
Metal propellers are usually made from aluminum and as such do not really corrode. Keeping the propeller oiled daily, especially in salty coastal environments will make sure that any corrosion is stopped before it does any damage.
Bug remains should be removed from the propeller right after the flight or at the end of the day. This stuff is very corrosive and hard to remove after a week in the hanger or left in the sun out in the open. Clean the rest of the aircraft too while your at it, a bit of water with a light soap does the trick perfectly.
A clean propeller (and wings too) performs much better, higher thrust and better climb may be expected. It might not be big numbers but the differences are there, and at the same time the aircraft looks good too!
These should be maintained by a qualified facility. The propeller hub contains the blade mechanism and every scheduled grease change removes contamination which could cause corrosion if not replaced. Use only the correct grade of grease specified by the propeller manufacturer.
If the propeller uses engine oil to operate the blades then regular changing of the engine oil really helps the propeller live longer. Done once a year, ideally before winter sets in, should be a minimum practice.
Leave the two-blade propeller in the horizontal position and the three-blade models in the one blade up position. This makes sure that the least amount of moisture can enter the hub. Should you poses blade covers, then by all means use them.
Propeller tracking makes sure that the blades do move through the same position or vertical plane without moving forward or backwards, which causes vibrations. This can be caused by a bent blade of an improper installation of the hub on the engine.
Propellers are normally statically balanced by the manufacturer but it is up to the owner or operator of the aircraft to balance the combination of engine and propeller (dynamic balancing). This will result in the removal of any vibrations and airframe and pilot fatigue will be minimal. This procedure is highly recommended!
Every propeller has an overhaul period, be that in hours (time in service) or in age (years), and its usually whichever comes first. Common overhaul times are 2000 hours or 10 years. During overhaul the blades of a metal propeller can be re-pitched to a coarser (cruise) or finer (climb) setting should you wish so. Do verify in the propeller maintenance manual if any re-pitching has already been done as this process is limited to number of degrees (in any direction).
Age eventually causes corrosion and this is the main reason that constant speed propellers really need an overhaul when the time comes, even if they only have been flown for a limited amount of time. The adage 'use them or loose them' comes to mind here.
Conclusion: By keeping your propeller(s) in tip top shape, you increase the safety of the flight. And, its the only part that moves the aircraft forward so take good care of it!