How does a propeller go into reverse and what is ...

Look at the prop like a screw you are screwing into wood. When the prop goes forward it is like when you screw into wood...when it is reversed the screw comes out of the wood...the concept with the propeller on a plane or on a boat is the same..only with water or air.

Hi Doug,

Here goes.  Think of a propeller like a big fan.  A fan has blades that are set at an angle so that it will blow air when you turn it on.  It might be helpful to start with a simple propeller like one that would be on a Cessna 172.  The blades of that propeller don't move from the angle the manufacturer picked. (sure, the propeller goes around but the angle of the blades can't be changed.  Just like the blades on your house fan can't be moved.)  This is called a fixed pitch propeller.  Now something like a Beachcraft Bonanza has a variable pitch propeller.  That means that the angle of the blades can be changed by the pilot.  A certain angle yields better takeoff performance (slow and/or heavy).  However, at cruise altitude it can be advantagous to be able to change the pitch of the blades - this usually yields better speed, fuel economy, and is usually quieter than the takeoff pitch setting.  All airplanes don't have variable pitch props because they result  in increases in weight, complexity, and cost.  The blades are moved by a gear mechanism built into the propeller hub.  This mechanism is usually powered by an electric or hydraulic motor.  Not only are these propellers more expensive to purchase than a fixed pitch propeller, but the mechanism that moves the blades has to be overhauled at regular intervals, just like the engine.  This all adds up, cost wise.  All of the props discussed so far only blow air in one direction - forward thrust.  Now, a propeller that is capable of producing reverse thrust is a variable pitch propeller that can move the blades so far that it now is blowing air the other way.  The propeller is still spinning the same direction - it doesn't actually change direction - but now the blades are blowing the air the other way.  More complexity and cost, but stopping distance is significantly reduced.  Because of the added expense, not many propeller driven aircraft have this feature.  Usually idle power is sufficient.  At idle,  the propeller acts sort of like a speed brake.  There are obviously exceptions and some owners or operators feel they need reverse capability.  Very handy in slick conditions.  As a personal aside, for awhile, I flew a big twin that could be landed and stopped (at 60,000 pounds) in less than 800 ft - mostly because of reverse.  Hope this has been fun and helpful.  Take care,  Jeff

I've heard of some small commuter prop planes using reverse to back out of a given parking position. I don't know if the practice is still used. Personally, I didn't consider it very safe for personnel on the ground..who would normally be cautious of blowing behind a prop..but not think of it in front of the prop. There was a lawsuit regarding an injury to a Flight Attendant on the tarmac under these circumstances.

Without reading the lengthy explanations above, let me offer this answer.  Propellers do not reverse.  They always turn in the same direction.  The pitch of the blades changes so that the thrust is reduced, or even reversed.

Jet engines also have thrust reversers for extra braking power when landing but the thrust is not reversed in the engine.  Instead, the thrust coming out the back of the engine is directed forward by a pair of clam shell doors that close behind the engine.

Sorry circusenvy1 but your reply is dead wrong.  Far from being the best answer, it is the least accurate of all the replies.  Propellers on aircraft only turn one way - the same direction at all times.  The never "screw out" or turn in the oppposite direction like a boat propeller in reverse gear. 

the propellar doesnt really go into reverse but the pitch of the blade is directed so that the thrust is thrown to forward of the a/c and not behind, Thush it helps shorten the landing roll along with the brakes. In a jet plane , reverse is lowering a deflector into the power stream of the engine which in turn changes the flow of the exhaust to the front.