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    Performance

    An Airmaster propeller can increase the performance of your aircraft in many ways.

    Take Off | Climb | Cruise | EcoCruise | Landing

      

    These gains come about because an Airmaster propeller is able to control the three most important aspects of a propellers operation.

    Engine speed management | Blade angle control | Optimum blade selection

     

    Engine Speed Management


    Most internal combustion engines require some form of speed control to make the best use of their available power.  If the rpm is allowed to rise to high, physical damage to the engine can occur, while if the engine is operated at too low an rpm, little power is produced or the engine can be damaged from excess cylinder pressure. 

     

    Maximum Power

    Airmaster propellers allow the engine to operate at its highest rated rpm during take-off. This translates to more horsepower delivered to the propeller and more thrust getting you off the ground sooner and safer. .

    Maximum Efficiency

    It is common for internal combustion engines to have a peak efficiency at an rpm that is close to the peak of the torque curve.The Airmaster propeller allows you to operate at this rpm irrespective of your actual aircraft cruise speed. 

    Blade Angle Control


    Correct blade angle management is one of the most critical factors determining aerodynamic propeller performance.  Following is a summary of some key points

     

    Blade -Wing Analogy

    A propeller blade creates thrust in a similar way that an aircraft wing creates lift.  The geometries involved for a propeller are more complex than a wing however, since the blade is rotating.  Even so, most of the same problems exist, and must be considered when designing a propeller ie correct angle of attack, correct aerodynamic loading etc.

    Lift and Drag

    Like a wing, a propeller blade will generate both lift (thrust) and drag (power requirement from engine).  They both increase with angle of attack but not at the same rate.  The ratio of lift divided by drag (L/D) can be used to determine what angle of attack is likely to give the highest efficiency,  so forms one of the points to optimise for.

    Blade Helix

    Since it is advantageous to operate the engine at specific rpm, it is apparent that a change in aircraft speed will result in a change in the helix the propeller cuts through the air. In order to keep to our desired angle of attack, the pitch of the blade must be changed, as the aircraft speed changes. 

     
     

    Variable Pitch Hub

    The variable pitch hub is able to alter the pitch angle of the blades dynamically during flight, and can be considered the ‘muscle’ of the system.   This achieves the desired goal of altering the angle of attack of the blade as a whole, but does not provide any ‘brains’ as to where the best pitch may be.

    Automatic Control (Constant Speed)

    A common method of controlling the pitch of variable pitch propeller hubs is to use the pitch to regulate the engine rpm.  Since increasing pitch increases thrust and the drag, it will tend to cause the rpm to decrease.  Similarly a reduction in pitch will allow the engine rpm to increase.  This is the basis for a constant speed controller.  Where as fixed pitch (black) propeller will allow the engine speed to rise with airspeed, a constant speed propeller (blue) will hold the engine rpm steady, regardless of airspeed (within limits)

     
     

    Smart Controllers

    The advent of electric variable pitch hubs in combination with digital control systems has allowed a simplification in the operation of constant speed governors.  AC200 from Airmaster is a good example of how engine speed control and pitch management can be distilled to a simple selection of flight mode.  Take off, Climb, Cruise and Eco-Cruise (Hold) + special modes to enhance safety. 

    Blade Profile Management


    The parameters of the blade design have a large affect on the final propeller performance.   Since these parameters are fixed once the propeller is made, it is very important to choose the blade with its intended purpose in mind.

     

    Blade Selection

    There are many factors that go into the final blade selection including performance, cost, durability, weight and looks.  There are also many blade brands available and each have their own advantages and disadvantages.  Airmaster are able to select the particular one that fits your needs the best, and incorporate them into a customised propeller system just for you. 

     

    STOL

    Short take off and landing styled aircraft want performance optimised at low speed while still maintaining best possible cruise.  Choose larger diameters (70in +) where possible to increase disk area and aerodynamic solidity, so long as there is sufficient power available from engine.  Choosing too large a diameter/blade area for a  given power will cause the AoA to decrease to a point of lower efficiency.

    X Country

    Cross country aircraft like to be optimised for efficient cruising.  Blades are generally tapered/swept tip to reduce noise/losses and have medium cord lengths.  Diameter is often in the 68in -70in range but this depends on the specific engine.  High revving engines will use smaller diameter/area blades.

     
     

    Speed

    Faster aircraft require special blade selection in order to realise best top speed performance.  Careful attention must be paid to the blade loading and blade twist at the expected operating points, as high altitude conditions vary considerably from those at sea level.  Two blade propellers may commonly be considered for their higher theoretical efficiency, however often three blade props prove to be more effective due to the limited diameter available. 

    Amphibious

    Water based aircraft benefit enormously from the additional performance offered by an Airmaster propeller.  Because of the high drag during take-off, it is imperative to generate the highest possible thrust.  If the available blade diameter is limited , wider cord sections are chosen to assist solidity.  Consideration is given to ensure the blades are robust enough to withstand constant exposure to water spray.  Additionally special functions like Reversing are included to assist with manoeuvring safety.

     

    Summary


    Airmaster propellers offer all these advantages because of the gains made when 

    Engine rpm is managed separately from throttle setting

    Blade angle of attack is optimised to air inflow

    Blade selection optimised for your application

     Below is a discussion on how these effects benefit the pilot and aircraft in each phase of flight

     

    Take Off


    Max Power

    Select T.O. and apply full throttle. 

    The controller will govern the engine to its maximum rated rpm and generate full power.  Careful blade selection will ensure this power is translated into the maximum attainable thrust by allowing optimum blade angle of attack. 

     
     

    More Thrust

    Generate more static thrust to increase the aircraft roll performance during take-off and decrease the time to lift off.  Airmaster CS propellers significantly out-perform GA propellers in this area.  

    Testing of a typical two place, Rotax powered aircraft fitted with a two blade wooden fixed pitch  propeller,  yielded a static thrust of ~150kg.  On the same engine/aircraft  a CS propeller was capable of pulling 220kg (increase of ~ 45%)

    When Its Needed

    The high drag on water based planes is a big problem during take off. There is simply no substitute for extra thrust in this situation. 

    “My smooth water takeoff distance was cut by a third. I can now get off the water quickly with two on board.”

     

     

    Climb


    Increased RoC

    Select CLIMB : Maintain Full Throttle

    Once clear of obstacles (or after the full power time limit of the engine), the engine rpm will be lowered to its unrestricted operational rpm.  Small incremental pitch adjustments will automatically be made to keep the blade at an optimum angle, as the altitude increases. The propeller will now deliver a strong, consistently higher rate of climb.

     
     

    Low and Slow

    Aircraft operating in hazardous conditions benefit enormously from the increased climb performance.  Now that blade selection and pitch adjustment is no longer an issue (as it can be for fixed pitch propellers), you are able to realise the full climb potential from your aircraft.

    Hot and High

    Altitude and heat sap the performance of both the engine and the propeller system.  Under these conditions it is imperative to ‘make the most of what you’ve got’, or to augment your engine performance with a normalising turbo.  Either way an Airmaster propeller will allow you to do this.  Blade selection can also be altered  to optimise for this condition.

     

     

    Cruise


    Faster Cruising  +10 to 15%

    Select CRUISE : 75% Throttle

    Once you have achieved your cruising altitude, select ‘Cruise’.  The engine rpm will be lowered to near its torque peak (depends on settings).  The pitch will be automatically controlled to maintain this rpm regardless of altitude or attitude. 

     
     

    Turbo Normalising

    When there are larger distances to cover, there are definite gains in speed, comfort and economy to be had by operating your aircraft above flight level 100. This is very effectively  achieved with a Rotax 914 and Airmaster constant speed propellers.  

    When we chose a propeller to fly around the world (in our 914 powered Sling4), it was of course the Airmaster – Mike Blythe, Multi Circumnavigational Aviator

    Lowering Pilot Fatigue

    Fatigue has an insidious effect on pilots and can be a potential safety hazard.  The Airmaster propeller combats this in multiple ways.  

    • Lower noise and vibration levels are achieved by operating at lower rpm and by ensuring each propeller is well balanced and at precise pitch. 
    • Shortened flight times are achieved by operating at higher cruise speeds. 
    • Pilot workload and stress are lowered from increased performance and automatic operation. 
     

     

    Eco - Cruise


    Lowest Fuel Consumption

    Select HOLD : 65% Throttle

    An additional rpm selection is available for your engines most economical rpm and manifold pressure setting.  This may be different for each aircraft/engine combination so the AC200 controller allows you to fine tune it with the Hold selection.

     

     

    Descent -Landing


    Increased Control

    Select T.O. : Throttle as required

    The Airmaster propeller will substantially increase the possible descent rate during landing in a controllable way. It does this since the pitch control mechanism will naturally adjust to the finest pitch possible during partial throttle settings. The flatter blade pitch acts as a large wind brake for the aircraft, helping to slow it down.  

    • The balance between thrust and drag is easily controlled by use of the throttle, with no other input required.
     
     

    Safer Landing

    Landing is a critical phase of flight that has a high potential for error (unfamiliar airstrips) and often requires maximum performance from the aircraft.  Airmaster CS propellers help the pilot during this phase of flight by increasing the descent control during landing, increasing the climb out rate (in the case of a go-around) and decreasing the pilot work load (compared to an in-flight adjustable type).