An airplane’s propeller is one of the most highly-stressed and most-overlooked components on any aircraft. During routine operation, 10 to 25 tons of centrifugal force is pulling the hub’s propeller blades. Also, the propeller blades are bending and flexing due to thrust and torque.
Engineers design propellers to be properly maintained and to perform normally under these loads. But when damage occurs due to corrosion, stone nicks, or worse, additional unintended stress is imposed. In that case, the margin of safety may not be adequate. Operating an aircraft needing a propeller replacement or propeller overhaul can be a dangerous risk.
Propellers may need a professional propeller shop’s special attention and capabilities for many reasons, such as scheduled overhaul limits, operating inspections, and major repairs. Not to mention – propeller replacements!
If you’re worried about your propellers or require a propeller governor repair or propeller overhaul, talk to the experts at Stockton Propeller. With decades of experience and free service area pick-up and delivery, we’re the propeller experts who keep you flying!
A Quick Recap On Composite Airplane Propellers
Airplane propellers have been around, well, since the first powered flight. In the early days of aviation, propellers broke at an alarming rate. This breaking was a function of being carved from wood, a porous and fibrous structural tissue.
Today aluminum and structural composite blades are standard, and repairing them when they get dinged has become commonplace. Damage can result from stones and other objects and impact with external objects or the ground.
Repairing a structural composite blade is quite different because instead of just removing material, composite repairs replace material lost to gouges and other damage.
Beyond their obvious weight advantage over aluminum blades, structural composite blades have additional benefits:
- A longer service life
- The ability to maintain an optimum airfoil shape over the propeller’s service life
- An almost infinite fatigue life
- An expert can repair most damage
- Far more robust when it comes to erosion and impact
- Can withstand a lot more impact without affecting its airworthiness
- Can be repeatedly restored to factory-new shape and aerodynamics
While the composite materials that form propellers are incredibly durable, they are not entirely immune to operational damage. Propeller manufacturers have created and published protocols to help airplane operators and maintainers determine when and how to repair composite blades.
Overview Of Propeller Issues
Most airplane propeller issues fall into one of two categories: corrosion or physical damage.
One of the most insidious causes of damage to a propeller is corrosion, both external and internal. External corrosion is visible on the blades. Internal corrosion eats at the components within the variable-pitch propeller. Regardless of whether it’s internal or external, corrosion reduces the propeller’s structural integrity, as well as its performance.
Physical propeller damage include nicks, dings, gouges, and cracks on both the propeller blades and the propeller governor.
A propeller repair shop has the tools to do much more detailed inspections of propellers for cracks, including optical, eddy current, dye penetrant, and magnetic particle inspections. However, routine examinations for damage visible to the naked eye are crucial for good propeller health.
According to the FAA’s Advisory Circular AC 20-37E, “Limited minor repairs may be made on propellers by appropriately rated maintenance technicians either on the aircraft or upon removal of the propeller. Minor dents, cuts, scars, scratches, and nicks may be removed, providing their removal does not weaken the blade, substantially change weight or balance, or otherwise impair its performance.”
Why Repairing Is (Sometimes) Better Than Replacing
There are many valid reasons for repairing rather than replacing. These include:
- saving money,
- continuing working with a component that is otherwise known to be good,
- supporting good mechanics in their business,
- and saving the planet from a little more “airplane junk” in the dump.
Aircraft owners should consider all the costs of time, expense, and safety when considering what course to follow while performing maintenance.
Some mechanics prefer replacement over repairing a component. All FAA-licensed mechanics are authorized to do most repairs or replacement tasks, as long as they have the proper training, tools, and documentation.
In truth, most of your aircraft’s components can be repaired by your trusted mechanic, as long as they have the proper training and tools. The question is, should you have the propeller repaired or replaced altogether?
It’s important to consider:
- How critical are the components to my safety and the safety of future flights? (Hint: Propellers are VERY important!)
- What are the costs of repairing versus replacing (including your own time, shipping costs, and parts/labor)?
- How will propellor governor repair versus replacement affect the future reliability (and future maintenance cost) of your aircraft?
All manufacturers publish “time before overhaul” (TBO) guidelines for their propellers. These TBO guidelines are based on both the in-flight hours and the calendar months the propeller has been in service. These guidelines typically range from 1,000 to 3,000 flight hours and five to seven years in service.
The Case For Replacement
So we’ve already covered the main questions on whether to deal with repairing vs. replacing above.
Why else might someone choose to replace a propeller?
- You’ve reached your propeller’s operational life limit.
- It seems obvious, but it’s imperative to pay attention to your aircraft propeller’s time before overhaul (TBO). Flying your aircraft with propellers beyond their intended service life is inadvisable and potentially dangerous. Overhauling or upgrading your propeller is an investment in your aircraft’s future safety and performance.
- You are ready for a dramatic performance increase.
- With new propellers, pilots can (potentially) improve aircraft performance with:
- shorter take-off distances,
- lower noise levels,
- better ground clearance,
- reduced tip erosion,
- increased climb rates,
- increased cruise speeds,
- and overall smoother operation.
How Do You Know Which “Flight Path” To Take?
Okay, we’re sorry about that awful pun.
But we’re not sorry about being the best in propeller governor repair or propeller overhauls.
Talk to us. We’re the experts at Stockton Propeller. With decades of experience and free service area pick-up and delivery, we’re the composite propeller experts who keep you flying!