experimental aircraft

The Ins & Outs Of Experimental Aircraft

The popularity of working with one’s own hands to take to flight began long before the Wright brothers ever started experimenting in Kitty Hawk. Flying machines were being thought up, experimented with, and attempted long before the settlers colonized the U.S.

But, unfortunately, those early “homebuilt” machines weren’t always safe. To make these machines safe, the government found it necessary to have some oversight. That oversight began in October of 1952. 

For the first time, the U.S. government included an “experimental” amateur-built category in the Civil Aeronautics Manual. Perhaps not so coincidentally, it was around this same time, in January of 1953, that the Experimental Aircraft Association was founded in Wisconsin.

At Stockton Propeller, we love the challenge of working with our experimental aircraft customers and on their custom aircraft propellers. If you’re looking for someone in the Northern California/Nevada region to work on your homebuilt’s propellers including to repair the propeller blade, contact us today.

What Is An Experimental Aircraft?

“Experimental” is the Federal Aviation Administration (FAA) designation for amateur-built or homebuilt aircraft. The “experimental” identification has been around for over 60 years. 

It’s an aircraft used for non-commercial or recreational purposes, such as education or personal use. The term refers to the FAA category for the airplane’s registration, not the exclusivity of the plane’s design or the aircraft’s use. 

Suppose an individual builds at least 51% of an aircraft. In that case, one may register the plane in the FAA’s “Experimental” or amateur-built category. 

Builders can work from kits (with parts of the airplane fabricated) or plans (where the builder purchases all the pieces and then assembles them). 

These amateur-built, or experimental, airplanes are also commonly referred to as “homebuilts.” The name is obvious because many individuals construct aircraft and custom aircraft propellers at home. Construction often occurs in their garages or other outbuildings.

There are currently over 32,000 amateur-built aircraft licensed by the FAA. They have been registered and flown safely for many years.

Curiously, the FAA’s “Experimental” category also includes approximately ten other subcategories. These include aircraft used for crew training or air racing. They also have historic aircraft (such as World War II military aircraft) flown in air shows and exhibitions.

Experimental aircraft are not the same as “ultralights.” Ultralights are one-person flying machines operating under a completely different set of federal regulations. 

Amateur experimental aircraft and homebuilt custom aircraft propellers are registered with the federal government in the same manner as production aircraft with corresponding “N-numbers” on the fuselage.

Who Builds Experimental Airplanes?

There isn’t just one demographic for those interested in taking on this project themselves. Builders include astronauts, airline pilots, military jet pilots, mechanics, machinists, welders, professional people, and many others.

Why do they build them?

There’s a variety of reasons why someone chooses this particular DIY project. 

  • They could see it as a personal challenge
  • They may want to educate themselves more on the “nuts and bolts” of flying
  • They could be seasoned pilots looking to increase their performance in the skies
  • They may want to invest some “sweat equity” into custom planes and airplane propellers instead of purchasing a manufactured aircraft. 

While a few homebuilt airplanes are custom or original designs, the vast majority of builders use standardized, tried-and-true kits or plans. These plans or kits are constructed successfully by the hundreds, if not thousands.

What Goes Into Building Your Airplane and Custom Airplane Propellers?

Most enthusiasts will tell you that it’s a lot of blood, sweat, and tears.

The cost of building your airplane range may range from under $10,000 to more than $100,000. Many factors contribute to this price variation, including your desired performance characteristics and any optional engine and avionics packages you choose

For comparison, a new factory-built Cessna 172 costs more than a quarter of a million dollars. 

Many homebuilts utilize composite materials that help create lighter, faster, and more fuel-efficient airplanes than similar production aircraft.

It can take a while, however….

Building an amateur aircraft and your custom airplane propellers will take somewhere between 1,000 and 3,000 hours to complete, on average.

Some individuals complete their airplane in less than a year. Others may take a decade or more.

A Few “Extra” Facts About Experimental Aircraft

  • Experimental aircraft are regulated, just like manufactured aircraft. The plane still has to be registered with the Federal Aviation Administration, inspected by an FAA inspector, and issued an airworthiness certificate.
  • An amateur-built airplane is subject to the same condition inspections every 12 months as small production aircraft undergo.
  • You don’t need a license to build your aircraft; all you need is the will fly one! To fly, you must earn and maintain the same federal pilot’s training and ratings as those who fly factory-built aircraft, including Pipers, Cessnas, and Beechcraft. 
  • Also, planes and custom airplane propellers must follow the same appropriate federal regulations during their flights.
  • Experimental aircraft are practically as safe as manufactured aircraft. Studies by the FAA and the National Transportation Safety Board (NTSB) show that experimental aircraft have an accident rate of less than 1% higher than the general aviation community.

Finding The Right People To Work On Your Custom Aircraft Propellers

There are very few surprises or breakthroughs when it comes to experimental aircraft design. 

Much like a relationship, every airplane build is a compromise: If you want a little more of this, you have to give up some of that. And vice versa. 

The freedom to fly something that doesn’t meet standard certification means that an airplane licensed in the experimental category will most likely fly differently than the norm. 

Its performance is optimized toward certain criteria that were important to the designer and builder. You’ll probably see sacrifices in other details to achieve that end.

Homebuilding is about freedom. The freedom to build what you want, use whatever materials you choose, and achieve whatever point you wish to make. Because homebuilders can create, modify, or change their aircraft as they want, there may be a chance for replication.

Then there’s always the freedom of expression. A homebuilt is like a blank canvas. The builder sketches out pretty much anything they want, putting their name on a design. They are free to do so, as long as it doesn’t endanger their life, passengers, or the populace below during flights.

At Stockton Propeller, we love the challenge of working with our experimental aircraft customers and working on their custom aircraft propellers. If you’re looking for someone in the Northern California/Nevada region to work on your homebuilt’s propellers, contact us today.

propeller inspection

Replacing vs. Repairing Your Airplane Propeller

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 Damage

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!