Cost conscience Pilots are often reluctant to bring their propeller in for professional inspections. The down time and expenses are delayed because the ever present fear is, “What if they scrap or red-tag my propeller?” The best strategy is to take care of your propeller and when you notice irregularities, have a professional look at your propeller immediately. A properly maintained propeller will have the longest life and save you money in the long run.
How important is run-up for Constant Speed Propellers?
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.
How can I tell if my propeller may have an issue?
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.
How can I prolong the life of my propeller?
- 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".
I had a prop strike is my propeller repairable?
If the damage on your propeller tips allows you to reduce the diameter (the total length of the propeller) by less than the manufacturer’s prescribed minimum diameter, your propeller is often repairable. Some props do not allow for any reduction in diameter, others will allow up to 2 inches.
If the leading edge, trailing edge, surface or tip of the propeller is damaged and in repairing the propeller the technician has to reduce any one of the dimensions below minimum dimensions allowed by the manufacturer, the propeller is not serviceable.
If the blades are beyond repair, the hub is generally not reusable. Sometimes the internal parts of the hub can be reused after appropriate inspection. The manufacturer’s manual will outline any exceptions.
Call us and we will help you make an informed decision regarding the serviceability of your propeller.
When might I need to change my propeller?
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.
Whatever the reason, changing your propeller demands careful consideration. We will help you investigate your options for upgrading to a higher performance propeller or in replacing your aging propeller.
Converting to a 3 bladed propeller could increase your rate of climb and provide a quieter flight. Conversion kits are munufactured for a large number of aircraft and can often be purchased for a significant saving over the direct replacement.
Should I use hours or time in service to determine if my propeller is due for an overhaul or replacement?
All propellers have recommended overhaul intervals based on calendar time and flight hours. Depending upon the prop model, the amount of time in service could be 1,500 or 2,000 flight hours. It is important that calendar time be carefully considered at about 5 years in service. Too many pilots ignore the calendar limit!
Consider the aircraft that flies fewer than 100 hours per year. At 100 hours per year, a typical propeller might not get checked for 20 years! This is clearly a bad idea! Your propeller should be overhauled at either the time or calendar limit, whichever occurs first! If the engine comes up for overhaul before the prop reaches either limit, most shops will recommend removing the prop and governor and having them overhauled at the same time!
How do I ship my propeller?
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.
Maintenance of your propeller logbook is very important. The logbook stays with a propeller and should be updated with each overhaul or refurbishment. When traded or exchanged, a logbook should accurately indicate the TSN (time since new) or TSO (time since overhaul).
Accurate logbook entries will enhance the trade in value of your propeller. Without proper documentation, the propeller cannot be exported and it might be difficult to sell.
Can I paint my propeller myself?
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.
Having your aircraft propeller dynamically balanced is the most cost effective maintenance you can do for your airplane.
What will Dynamically Balancing my propeller do for me?
Balancing your aircraft propeller increases the life of your engine, improves performance, reduces vibration and saves maintenance dollars. PropellerMan’s experienced technician will generally reduce your propeller’s vibrations to half the acceptable .14 IPS limit.
Reading the FAQs below will help you to better understand the advantages of a dynamically balanced propeller.
How do I know if my propeller is in need of being dynamically balanced?
•If you have had your propeller overhauled or replaced, you should have the propeller dynamically balanced. (The propeller repair shop will provide a static balance only). •When your propeller is removed for engine work, you may want to have the balance rechecked. •If your engine keeps developing oil leaks after repairs have been made. •If your plane vibrates excessively. (NOTE: Some out of balance propellers do not cause perceivable vibration but still need to be balanced!)
My aircraft runs fine, why have my propeller balanced?
Most fixed-wing aircraft will benefit from having their propeller dynamically balanced. Most of the aircraft we have balanced had an initial vibration level greater than .45 IPS, three times the acceptable vibration level. Your engine, firewalls, instrumentation and even the structure of your aircraft will benefit from reduced vibration levels following a dynamic balance.
My aircraft propeller was overhauled recently. Should I have my propeller dynamically balanced?
The best time to dynamically balance a propeller/crankshaft is immediately following overhaul or propeller replacement. Even new aircraft with zero time engines and propellers need to be dynamically balanced. The shop that overhauled your propeller will statically balance your propeller before returning it to you. It must then be dynamically balanced when bolted to your aircraft.
What level of propeller vibration is acceptable?
In most cases, the vibration level due to mass imbalance can be brought down to under .14 IPS (inches per second) and usually to less than .07 IPS. When propeller vibration levels are this low, the operator will see a significant reduction in component wear and fatigue and the majority of pilots immediately notice a positive effect on the level of vibration in the cabin.
Will having my propeller dynamically balanced disguise other engine problems?
No! An engine with an internal problem causing unusual vibration will not respond to balancing in the same way that an engine which only vibrates from a propeller imbalance