An aircraft’s propeller is one of the most increasingly stressed parts, which experiences 10 to 25 tons of centrifugal force during routine operations, with blades flexing, bending, and contending coupled with consistent engine power pulses and vibrations. Besides that, there is also a frequent build-up of debris and caustic elements on the propeller after each flight.
It’s vital to perform proper aircraft propeller maintenance regularly to ensure your plane runs smoothly and at peak efficiency under these harsh conditions. Propeller repairs are an essential part of its care and maintenance. Your plane’s propeller requires special attention after a certain number of flight hours, also known as the manufacturer’s published ‘Time between Overhauls’ TBO limit.
What Is A Propeller Overhaul?
An aircraft propeller requires periodic inspections and maintenance like any other mechanical part of your plane. If not maintained regularly, even your airplane’s propeller’s slightest issues may become highly costly and dangerous for flight safety. While you should conduct maintenance and inspections of your plane’s propeller frequently, most of the problems are challenging to detect, like seal aging and corrosion.
The increased degradation of a propeller is often identified only during a complete disassembly and overhaul done by a certified aviation maintenance expert. Even the aircraft propellers stored in a hanger or with low operating hours are susceptible to gradual degradation over time due to various factors, including internal seal aging, corrosion, and breakdown of internal lubricants.
Overall, a propeller overhaul is an increasingly careful and detailed process that involves propeller system disassembly, damage inspection, and propeller blade refurbishment as per the manufacturer’s specifications.
When Is The Right Time For An Aircraft Propeller Overhaul?
Always refer to the original equipment manufacturer’s OEM guidelines regarding propeller overhauls, calendar limits, TBO extensions, and long-term storage. Your propeller model number will tell you your propeller model specified in the service letter. This will help you determine the recommended number of flight hours within which your plane’s propeller can operate efficiently and safely between overhauls.
Things To Expect From Your Aircraft Propeller Overhaul
You can expect your propeller repair expert to perform the following vital steps during your aircrafts propeller overhaul:
Visual And Dimensional Checkups
First, your aircraft maintenance specialist will inspect your propeller visually for possible damage. Severe corrosion or ground strikes could prohibit your propeller from general overhauling services. The next step will be complete disassembly of your prop, followed by cleaning and servicing each component as per the overhaul manual. During this process, all parts of your propeller will be inspected and measured for damage.
For props with aluminum blades, the refurbishment process involves removing paint and remedying any minor damages and corrosion. It’s then followed by measuring the propeller blade dimensions for a second time after the refurbishing process. In the case of high-quality composite propellers certified for extensive blade life, the blades can be restructured to the original dimensions without excluding any material.
Non-Destructive Testing NDT
This procedure is often utilized to identify corrosion and cracks present in the propeller blades and hubs. There are different NDT methods, including eddy current, magnetic particles, and liquid dye penetrant inspections. In the case of composite blades, radiography or ultrasound inspections are widely performed.
For propellers with aluminum blades, the procedure called shot-peening is usually conducted to increase part-fatigue resistance. Aluminum blades get anodized for enhanced corrosion protection before applying a fresh coat of paint. After completing inspection and refurbishment, your prop will undergo reassembly and replacement of any necessary parts.
Lastly, your aircraft propeller will need to be rebalanced after completing its overhaul. Generally, a static balance is performed to ensure equal weights of both blades. Another procedure followed is dynamic balancing performed after mounting and re-installation of your plane’s propeller. This also helps in reducing the overall cabin vibrations and noise during a routine flight.