Newtons law & Propeller

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What is Newtons second law and how it matches with Aircraft Engine?
If some mass ‘M” is accelerated, then a force presents. Same way the mass of fuel air mixture is accelerated by a chemical reaction thus creates exhaust force.

What is Newtons third law and how it matches with Aircraft Engine?
For every action there is an equal but opposite reaction.  The exhaust force created is also having equal and opposite reaction called Thrust which is always in the direction of flight.

What is a propeller? And how it functions?
A propeller is simply a rotating aerofoil. It provides thrust in the same way as how an aerofoil mounted on wing generates lift. To know how a wing generates lift click here.When propeller rotates, the hub has to cover a least circular path whereas the tip has to travel a large circular path; in the same time. So propeller tip will be experiencing high speed than hub; that means from hub to tip speed is increasing.



Suppose if we want to have a uniform thrust all along the length of propeller, the propeller must be designed by adding more aerofoil at various angle of incidence (or pitch) by taking consideration of the speed at the part. This is the reason for twisted propellers. The tip will have lowest angle of incidence where as the hub will have largest angle of incidence.

What are the types of propeller?
Fixed pitch propeller- The pitch can’t be changed after design
Adjustable pitch propeller- The pitch can be adjusted at ground with engines off.
Constant speed propeller- The pitch can be adjusted during flight to maintain a constant speed.

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