Everything You Need To Know About Propellers – The final result of all your expense and effort when building a new home built airplane will be the performance of the propeller attached to your engine. Choosing a propeller type and supplier can be as simple as following the original designer’s recommendation or as complex as sifting through websites and input from fellow builders. In our annual roundup of propeller companies, we will try to update information and developments from the wide range of propeller suppliers and revise the topic of propeller design to help guide your choice.

If your homebuilt project will use a certified engine, you may feel the need to stick with an FAA-certified propeller, which limits your choices to the major U.S. it. Manufacturers of such props – Hartzell, McCauley, Sensenich and the foreign companies have gained mutual certification, such as MT-propeller. On the other hand, other than perhaps shortening the Phase I flight testing period, there is no compelling reason to go with a certified propeller on your homebuilt. The non-certified propeller route offers many more options, including some experimental-category props offered by traditional certified propeller makers. From the crossover models, your search can also lead to propeller suppliers who have no interest in offering certified props, who prefer to concentrate only on the experimental market.

Everything You Need To Know About Propellers

The ultimate experimental-category propellers are the customized props created for your particular engine and airframe combination. If you give custom prop builders your horsepower and speed range, they can create a special propeller just for your aircraft. In some cases this may involve a little tweaking to bring it right into the performance slot you want, matching it exactly to your real-world operating regime.

These Strangely Shaped Propellers Sprang From Research Into Propellerless Flight

Starting at the basics, a simple fixed pitch two-blade aircrew will keep the cost down and simplify the installation. Your engine may be installed only to accept such a primitive device. A fixed pitch propeller can be made of laminated wood, forged aluminum or composite materials with various core constructions. Fixed-pitch means you’ll have to live with the performance compromise inherent in the pitch built into the blades. Engine RPM changes as the airspeed varies unless the throttle is continuously adjusted.

Propeller pitch is similar to an automotive transmission’s gearing ratio: with only one “gear,” your fixed-pitch propeller is likely to be targeted more toward level cruising flight, where the airplane spends most of its time, to the detriment of takeoff and Climbing performance. However, there is a “sweet spot” range for a given blade pitch in which performance deteriorates by 10% or less from an optimum pitch. Some prop builders claim that their blades have the ability to flex under load to achieve some shift in pitch that provides better performance than a true fixed-pitch blade.

Experimental aircraft often use ground-adjustable propellers, with blades that can be rotated in a special hub mounting that allows their pitch to be tuned to provide maximum thrust at a certain airspeed. Such technology dates back to the 1930s, when adjustable steel and aluminum propellers were widely used. Once the adjustment is set, you will have a fixed pitch propeller until you can land and adjust the blade settings. Rarely do builders change the pitch once the proper setting is determined.

Ground-adjustable propellers can be tuned to provide maximum thrust at a certain airspeed. Once the blades are set, you will have a fixed pitch propeller until you can land and adjust the blades to a different setting.

How To Optimize A Propeller Design

Of course, pilots would rather be able to adjust the propeller pitch in flight, leaving it at a low pitch setting for takeoff and initial climb, then dialing it to a higher pitch to keep the engine from over-revving as airspeed increases in level flight. Such in-flight adjustments usually require intermittent activation of an electric motor to precisely determine the desired engine rpm. Some motorgliders, aka self-launching sailplanes, have three-position manually adjustable propellers that are shifted with the engine at idle, offering climb, cruise and feathered (engine off) positions. Adjustable propellers perform like fixed-pitch devices once set, so there will still be RPM changes as airspeed increases and decreases during maneuvering flight.

Naturally, more capability is always better, so the next step in complexity is to add a governor to the pitch-change mechanism, constantly varying propeller pitch during flight, so engine rpm is constant despite changes in throttle and airspeeds. Constant-speed propellers are complex devices and require a means of imparting the pilot’s impulses to the propeller, either electricity or oil pressure delivered to the prop hub. Having more moving parts to wear out means maintenance is inevitable. Also, the extra up-front weight of the constant-speed prop and governor must be taken into account.

Multi-engine airplanes require a means of stopping the propeller to reduce drag in the event of an in-flight engine failure, so the feathering propeller was invented to stop a windmill propeller from being a giant air brake. And for times when adding even more drag would be desirable, like during landing rollout, someone came up with reversing propellers, applying engine power for braking.

Ground-adjustable propellers are typically set up for level cruising flight. However, if better climbing performance is needed, the blades can be adjusted on the ground.

Blades Of Glory: What Every Pilot Should Know About Propellers

There is something to be said for simplicity. Failure is unlikely to occur in a piece of equipment that is not installed, and keeping extra weight off the aircraft is always desirable. Many owners would like the look of a three-blade prop, mistakenly expecting some benefit of performance enhancement. For most small homebuilds, a two-blade propeller is more efficient. Adding blades should only be done if extra horsepower needs to be harnessed; Generally speaking, a tri-prop provides more starting torque for takeoff and sounds better, but it will require masterful ranging to offset the inherent loss of performance over a good two-blade propeller, and there is usually a weight penalty.

I recently encountered an experimental airplane owner who wasn’t satisfied with his homebuilt 180-hp Lycoming O-360 engine, so he spent big bucks to remove the carburetor and install a rear-mounted fuel injection system. On top of that, he replaced the fixed-pitch propeller with a constant-speed version, something never envisioned by the original kit designer, which required substantial cooling modification. One hopes he considered the effect of the added forward weight.

All airplanes are compromises, and propeller choices are part of the equation when it comes to designing performance targets. It is always best to go with the propeller recommendation of the kit supplier and use a propeller type found to be correct for your engine installation.

As in previous years, we have compiled the latest information on propeller suppliers. Here are our listings for 2023.

Airplane Propeller Replica 46

At press time, we had not received a response to a request for an update on GT Propellers based in Rimini in northeastern Italy. Relying on previous information, we can only quote their website: The Italian propeller manufacturer GT Propellers offers wood-core carbon-fiber props in two- to five-blade designs, in fixed, ground-adjustable and constant-speed applications. They have had a 30-year relationship with Tecnam Aircraft, using GT props in Rotax engine applications.

Now part of a newly formed Hartzell Aviation umbrella that also includes exhaust and engine mount repair and fabrication, as well as the engine accessories division, Hartzell Propeller is Hartzell Aviation’s flagship component. In business for more than a century, Hartzell Propeller continues to develop powerful propellers for experimental aircraft.

Currently, Hartzell is with the Explorer, a three-blade carbon fiber prop for cross-country cruising with Lycoming 320/360/390 engines and several 540s as well. For stall work, the Pathfinder three-blade composite-blade model works well on select Lycoming 360 and 390 engines, and for backcountry and floatplane operators Hartzell offers its Trailblazer two- or three-blade prop for certain Lycoming 360 to 580 powerplants. Hartzell’s popular blended airfoil propeller, used on many kit airplanes for cross-country flying, is a two-blade constant-speed aluminum prop with swept tip blades for most 360 and 390 Lycomings. For the next generation of aerobatic propellers, Hartzell offers the Talon carbon-fiber two- or three-blade propeller, usable on select AEIO-360, 540 and 580 Lycoming engines.

As a wholly owned division of Cessna Aircraft for the past 62 years, continuing as part of Textron Aviation Inc., a Textron Inc. company, McCauley has been in the aluminum-blade propeller business since 1946. Equipment props for the Textron fleet and marketing the Blackmac brand of STC’d retrofit products. There are over 350,000 aircraft with McCauley propellers out there in service, so if you wind up with a used McCauley constant-speed prop on your project, it will be well supported.

Understanding Your Sailboat Propellers

Although of German origin, the MT-Propeller line of “natural composite” props is supported in North America by a company-owned service center in DeLand, Florida. MT offers a wide variety of constant-speed propellers for single-engine planes, as well as feathering and reversing systems for piston and turbine twins. Recent STC approvals are five-blade propellers for the King Air 300/350, three-blade props for Piper’s PA-34-200 and a five-blade propeller for the turbine conversion Cessna 206. Last September, MT-Propeller flew experimental 11 -Blade propellers mounted on a piper Cheyenne.

Sensenich, a major US

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