Aircraft Products
MT and Hoffman Propellers

Steen Aero Lab is proud to be an official distributor for both MT Propeller and Hoffmann Propeller. These German-made wood composite propellers are the finest in the world and are used for a variety of industries including general aviation, military trainers, airships, hovercraft, and wind tunnels. These companies have a combined manufacturing experience spanning many decades and their attention to quality ensures that these propellers are, quite simply, the best available anywhere. We can supply you with a high-performance propeller for almost any application: Aerobatics, General Aviation, Single or Multiple Engines, Piston or Turboprop Power, Certified or Experimental, Tractor or Pusher, Bush/Wilderness Flying, Motorgliders, Amphibians and Seaplanes, and even Airships!

Wood composite propellers (also called Natural Composite Propellers) are strong and lightweight and have many advantages over metal propellers. This construction method which is excellent for aerobatic and sport aircraft. Each propeller is custom-made to best suit the particular application, and MT and Hoffmann employ expert craftsmen who take great pride in producing the best propellers possible.

A short list of the many advantages of MT and Hoffmann wood composite props would include:

PROP CONFIGURATION
Propellers are available with 2, 3, 4, 5, and 6 blades, and the pitch may be fixed or variable (either electrically or hydraulically controlled.) Every prop design is custom-designed to be the perfect match for the application it will be used in. We even offer several custom colors!

Wood composite props can also be made to copy the blade patterns of most vintage aircraft, since no molds or castings are required for this type of construction. Wood composite props have been created for aircraft ranging from Spitfires and Yaks to the Junkers Ju-52 trimotor.

BLADE CONSTRUCTION
Both MT and Hoffmann props use advanced CNC machines to ensure that the wooden propeller blanks are milled to the tightest of tolerances. This ultra-precise manufacturing technique ensures that every single prop blade will have exactly the right airfoil shape and blade profile along the entire length of the blade, which means that every blade of the prop will perform exactly like the others. This leads to incredibly smooth running and less stress on the engine and crankshaft. After the wooden cores have been created and have passed inspection, a metal leading edge is often added to provide for maximum protection against damage from rain, water spray, gravel, etc. The metal leading edge is usually stainless steel, but for turboprop applications where the prop speeds are generally always high (even while taxiing) an optional nickel leading edge is available (nickel has roughly twice the resistance to nicks and damage than stainless steel.) Finally, the blades are covered by a tough, multi-layered epoxy/fiberglass composite covering. This composite covering adds tortional rigidity to the blade, as well as protects the entire blade against erosion and seals against water damage.

The materials and color coats used on the external layers are carefully chosen to provide for many years of superb resistance to damage and to maintain your prop’s great looks. For most applications, the rear face of the prop is painted flat black for visibility and to avoid reflections, and a variety of standard and custom colors are available. You will be proud to be seen with an attractive MT or Hoffmann prop on your aircraft!

DURABILITY
Wood composite props have a lot going for them, from their resilient construction to the exacting standards to their ability to be repaired easily if required. All of this can be described in one word: DURABILITY. Your MT or Hoffmann wood composite propeller will hold up through all types of climates and weather… from the snowy tundra to the blistering heat of the desert, and everything in between, you can depend on your MT or Hoffmann prop to serve well. Best of all, this isn’t just marketing hype or hopeful thinking based on limited lab tests. The extensive laboratory testing is backed up by the fact that many thousands of MT and Hoffmann wood composite props have been in service around the world for many years now. This large fleet of props is being operated in every concievable environment… snow, rain, humidity, floatplanes, dust, heat, you name it. This is proof positive that wood composite propellers are equal to the toughest challenge of all… surviving in the real world.

VARIABLE-PITCH, CONSTANT SPEED, FEATHERING, AND REVERSIBLE PROPS
For those looking for a variable-pitch propeller, we offer both electrically and hydraulically-controlled models with 2, 3, 4, 5, and 6 blades. Feathering and full reverse is available as well. Governors, control units, spinners and hub assemblies, and other accessories are available to fit Continental, Lycoming, Rotax, and turboprop engines in a wide variety of aircraft applications, including motorgliders and airships.

MT also offers the ELCOPROP, the only certified electric constant speed prop available worldwide. This propeller weighs about the same as a metal 2-blade fixed pitch prop, and is available in tractor or pusher configurations with 2, 3, or 4 blades and can be used on engines up to 350hp. Full-feathering capability is an available option. Several STC’s are available to retrofit aircraft currently equipped with fixed-pitch props, and it can be used in other applications such as ground-effect vehicles.

We offer everything you need to put a variable-pitch prop on your aircraft, or we will help you mount a new prop to work with your existing governor and other components whenever possible.

FIXED-PITCH PROPS
Fixed-pitch props are made in a manner that’s generally similar to variable-pitch blades. We can also provide elegant “wood look” props built to the same demanding standards as the more usual wood composites.

PROPELLER COMPARISON
Wood Composite vs. Aluminum

WOOD COMPOSITE BLADE	ALUMINUM BLADE
WEIGHT (Typical 3-Bladed Prop)
37% LowerApprox. 55 lbs. for typical 80 in. dia. prop.	HeavierApprox. 88 lbs. for typical 80 in. dia. prop.
POLAR MOMENT OF INERTIA (3-Bladed Prop)
60% LowerApprox. 4,100 lb.in.2 for typical 80″ dia. prop.	HigherApprox. 10,300 lb.in.2 for typical 80″ dia. prop.
VIBRATION CHARACTERISTICS
Less VibrationWood composite construction is an excellent damper of engine vibration.	No DampingAluminum props do not absorb vibration, and often carry operational RPM restrictions as a result to prevent catastrophic failure due to vibration-induced metal fatigue.
FATIGUE LIFE LIMITS
No Life Limit EstablishedNo fatigue problems have ever been reported. The lower weight and vibration-damping characteristics of a wood composite prop also creates significantly less strain and fatigue on the engine it is attached to, particularly during maneuvers.	Fatigue ProblemsBroken blade tips and broken hubs are regularly reported. Vibrations can induce and rapidly worsen fatigue cracks and failure. Given enough repeated vibratory stress, anything made of metal can, and will, eventually fail – not a good thought when you think of a heavy, quickly-spinning propeller blade!
ALL-WEATHER OPERATIONS
De-Icing AdvantagesElectric de-icing boots are available. Because wood composite blades have much lower heat conduction than aluminum, the boots consume half the amperage of standard boots – this allows you to use a prop with more blades while maintaining the same or less amp draw.	StandardAluminum is an excellent conductor of heat, which means it generally takes more of the available electrical capacity to de-ice a metal propeller than a wood composite prop.
EROSION PROTECTION
Erosion SheathA Stainless Steel erosion sheath (3 times harder than aluminum) plus polyurethane tape bonded to the blades provides excellent and replaceable protection from water spray, rain, hail, ice, sand, and stones. For turboprop applications (where the prop RPM is always high, even while taxiing) we have a Nickel leading edge option available, which is twice as damage-resistant as the Stainless Steel version.	Not Needed, BUT…Nicks from stones or other damage can lead to fatigue failures; requires dressing which can change the shape and performance of the blade.
CORROSION
No Corrosion PossibleWood and composites are not subject to corrosion problems, and the wood is protected from damage and decay by the durable, waterproof composite covering. Few atmospheric or environmental factors are capable of harming or penetrating the composite outer layers, and the Stainless Steel leading edge will not rust.	Corrosion CommonMoisture is everywhere, and the corrosion it causes is the biggest enemy of aluminum structures – including propellers. The high stresses experienced by a propeller greatly magnifies and accelerates any corrosion problems that may exist.
SERVICE LIFE
UnlimitedRepairs, if needed, do not alter the original dimensions of the blade, nor do they reduce strength. During overhaul, dings can be filled in with composite materials to maintain full strength while maintaining the precise airfoil shape. Repairs are generally invisible.	Limited Service LifeThere is only so far that you can go with removing and bending metal before you lose strength and performance, therefore there are significant repair limits associated with a metal prop.
PERFORMANCE
Improvement and ConsistencyWood Composite blades maintain their exact dimensions during their entire service life, producing consistent and exact performance each and every flight. The airfoil is made to exactly match the application, so valuable horsepower isn’t wasted.	ChangesPerformance can change with each blade rework, since the blade dimensions and airfoil are altered when material must be removed to effect repairs. This can also lead to vibrations and changes in balance. Most aluminum props are produced “cookie cutter” style for a certain engine.
REPAIRABILITY
Unlimited ReplacementsThere is no limit to the number of times the erosion sheath or leading edge can be replaced or to the rebuilding of blade tips… the original blade dimensions and airfoil is always maintained.	LimitedBlades must be shortened, scraped or filed to repair nicks, tip damage and other problems – this changes the dimensions, airfoil and balancing, eventually requiring the removal of the prop from service.
TOTAL VALUE
Maximum ValueThe above combination of factors give a well-made wood composite prop an edge over a metal prop in nearly all applications, both in performance and long-term durability!	Tried and TrueAluminum props are still popular, of course… yet they still suffer from the same problems they’ve had since the dawn of powered flight!