Prior to flight, take a few precautions to ensure that your propeller will perform as needed: Listen and feel for unusual noises and vibration. Look for loose bolts or a tip that might have separated during the start and taxi sequences. All props vibrate to some extent during operation. However, propeller roughness may be caused by 1) bent blades 2) blades out of track due to improper mounting of the propeller on the engine shaft, 3) imbalance, 4) a propeller loosely mounted on engine shaft, 5) angles between blades are out of tolerance 6) spinner imbalance due to improper mounting or dirt, snow or ice inside the shell.
- Use restraint in removing nicks. If you are an Ag Pilot, you most likely act as your own mechanic. As the mechanic, use restraint in removing nicks and sharp edges from your own propeller. We frequently see propellers that have been filed below minimums in the field. In an overhaul, the Professional Propeller Technician (PPT) is trained to remove just enough to smooth all of the dings and blemishes. Even a PPT can cause a blade to go below minimum thicknesses to where a blade will be scrapped. Leave as much blade diameter, thickness and width as possible for the PPT to utilize during overhaul. We want your propeller to make overhaul!
- Wash your propeller daily. While it is a good idea for every owner to wipe down a propeller after use, it is absolutely critical for the Ag plane owner to remove the caustic chemicals that build up with each use.
- Send your prop to a Certified Repair Facility for a Midlife Inspection. Keep in mind that even though your propeller appears to be functioning, internal corrosion, especially in humid climates, could be destroying your propeller. Catch corrosion early!
- While conducting a Midlife Inspection, have your propeller resealed. During a reseal the propeller is taken completely apart, a visual corrosion inspection is conducted and all the seals are replaced. Usually the propeller is repainted and balanced at this time as well. This relatively inexpensive procedure (half the cost of an overhaul) can add life to your propeller through the early discovery of corrosion and other problems that can destroy your propeller.
- Paint your propeller. Paint helps protect your propeller. A Dress and Paint by a professional will add life to your propeller! This procedure can be done more frequently, but the mid life inspection is a convenient time to get your propeller painted.
- Never attempt to straighten a propeller blade yourself. Straightening your own propeller blade is illegal for a good reason. Compromised metal is very dangerous. Let the experts straighten your blade and determine if the propeller is safe to put back on your aircraft. When it comes to propeller maintenance, never were the words, “Better safe than sorry” more true.
- Look at your Manufacturer’s guidelines before attempting to grease your own propeller. Over greasing your propeller can potentially cause an out of balance condition. Review your manufacturer’s general guidelines on how to grease your propeller.
- Keep your propeller balanced, both Statically and Dynamically. A Static Balance is routinely performed on every propeller by a Certified Propeller Repair Station (CPRS) during an overhaul, mid life inspection or even during a simple Dress and Paint. A Dynamic Balance is performed on a plane with the engine running. Because CPRSs (or other Maintenance Facilities) charge additional fees for this service and because it is not “required”, the owner often chooses not to have this service performed. Penny wise but pound foolish! A Dynamic Balance will help mate the prop and the crank shaft together; save the bearings in a crank shaft; and enable the entire engine to run more smoothly.
- Be on the alert for oil or red dye. If you spot oil or red dye, try to locate the origin of the leak. The propeller is not always the source of the leak. Engine oil leaks caused from mounting the O ring or crank shaft seal are often blamed on the propeller. If red dye is evident, the propeller must be removed from service and sent for repair. Depending on the model of the prop and per the manufacturer’s instructions, you are allowed to see if the propeller will seal itself. As long as you are not faced with a severe leak of red dye, you may fly a couple hours “to get where you are going”.
You MUST change or overhaul your propeller if you have a damaged or unserviceable propeller due to a strike or corrosion. Unseen internal corrosion destroys many propellers. The only way to properly inspect the surfaces of the hub and the blades for corrosion is through a teardown. You should overhaul your propellers if your propeller has reached recommended overhaul intervals based on either calendar time or flight hours. The manufacturer’s recommended TBO (flight time or calendar time) is mandatory for commercial aircraft.
Other reasons for changing your propeller include:
- If you change your flying habits (ie used to fly from grass strip to cross country)
- Move from sea level to a high elevation city.
- To improve take off and climb.
- To make your plane quieter.
- To gain ground clearance.
- Propeller is damaged or unserviceable due to a strike or corrosion.
- If you are changing from wheels to floats or skis or visa versa.
If a propeller must be shipped (for trade in or repair) never apply tape directly to the blades. Wrap each propeller blade with 3 or 4 layers of corrugated cardboard applying additional layers to the tips.If your propeller is a variable pitch, wrap the hub with several layers of cardboard and then cover the hub with a box padded so as to keep the hub from direct contact during shipping.If you are using a wooden box for shipment use caution to insure that the propeller fits snugly and is well padded inside the wooden container as the propeller will sustain damage if room for movement exists inside the crate.
For constant-speed propellers during run-up keep an eye on the oil pressure and temperature. Pressure should be in the normal, green arc range, and the temperature should be rising according to outside conditions. Because the constant-speed propeller needs both good oil pressure to do its job and oil thin enough to be pumped through the smaller passages of the prop, tit is important to keep these parameters in mind, particularly for cold weather departures. A takeoff with cold oil will result in a poorly governed prop and a possible over speed event. In subfreezing conditions, it could take 15 to 30 minutes to get minimum oil temperature. Storing the airplane overnight in a heated hangar or calling for preheat will help greatly.
While some try to paint their propellers themselves, I highly recommend that your propeller be repainted by a professional. Propeller repair stations will “dress and paint” your propeller using a high quality paint recommended for propellers.