It's not so much that it is moving more air but more inches through the air. Even though the 48" is only moving the airframe 48" per revolution it is able to do more revolutions per minute so the over all movement is greater. It can do this because the prop is flater and the engine can get a higher static or low speed RPM. But that then hurts it in cruise because the engine can over rev so when you throttle back for cruise you are moving less inches forward then the 50". This is the reasoning behind controllable props and why a controllable prop can generate a static RPM at red line and a fixed pitch can not. Static RPM for a fixed pitch prop depends on prop pitch.
Kevin1 --- In [email protected], "Donald" <dongen...@...> wrote: > > > > The way I understand (or misunderstand) that is the 48 pitch is turning > enough faster than the 51 will, so that it actually moves more air. If one > had unlimited horsepower or torque (wouldn't that be sweet?) then yes the 51 > would climb faster as you reason. > > --- In [email protected], Bill BIGGS <webacraft@> wrote: > > > > > > It is a matter of Torque. > > > > > > > > With the same prop pitch, more engine torque is required to turn the prop > > at a higher rpm. > > > > > > Bill > > > > > > To: ed@; [email protected] > > From: ercouper@ > > Date: Mon, 25 Jan 2010 13:59:00 +0000 > > Subject: RE: [ercoupe-tech] Re: PROP PITCH > > > > > > > > > > > > > > > > > > > > I am and have been confused about the prop pitch and hp relationship. If > > one is flying at a specific rpm with a 85 hp engine and a > > > > 71-51 prop, it is moving a specific amount of air regardless of the weight > > of the airplane. I understand that if the engine won't achieve the > > particular rpm the prop is not moving the same amount of air. So a 71-48 > > at 2250 rpm moves less air than a 71-51 at 2250 rpm. One would think that > > the 51 pitch would be better for climb. Is the issue that the engine can't > > turn the needed rpm in climb? > > > > Lee > > > > > > ____________________________________________________________ > > Diet Help > > Cheap Diet Help Tips. Click here. > > > > > > > > > > > > _________________________________________________________________ > > Hotmail: Free, trusted and rich email service. > > http://clk.atdmt.com/GBL/go/196390708/direct/01/ > > >
