Real Basic Question...

[Guest]

Okay, we're taking a few steps back here...but...Does "fixed pitch" mean the same thing as "constant speed?"The reason I ask is that I'm looking at some of the default FS2k2 aircraft. For example, the C172 says it has a "fixed pitch" propeller and does not have a blue prop lever--and that's what I was thinking. The C182, though, says it has a "constant speed" propeller, but the 182 HAS a blue prop lever which controls the pitch.So...is this a faux pas on Microsoft's part, or do I have my terminology mixed up?Thanks in advance,

[Guest]

No mix up. Just confusing terminology.A fixed pitch prop is just that -- fixed. There is no adjustment for pitch or speed. The throttle controls the speed of the propellor.A constant speed prop is more aptly name a variable pitch propellor. Ignoring the blue lever for just a moment, the throttle will control manifold pressure and power. But there is an oil system involved that varies the pitch of the prop to keep it spinning at a constant RPM. Bringing the blue lever back into the equation, the pilot can adjust the speed of the propellor, but for the most part, the prop will maintain the set RPM even with varying power settings.Did that clear things up a bit?(Experts: Did I get it right?)

[Guest]

Fixed pitch and constant speed are not the samething.In an airplane with a fixed pitch prop, the pitch angle of the blades cannot be changed and the prop RPM is dependant on your manifold pressure (power) setting. Its like the first bike you had. You have one gear and its designed to work over the entire normal operating regimen of the aircraft.Constant speed props on the other hand can vary the pitch and rpm of the prop independantly of the manifold pressure setting. In other words you can set a CONSTANT pitch/rpm for a given manifold pressure. The exceptions are when the engine is not developing enough torque to turn the prop at the set speed, like when at idle or when you forget to enrich the mixture during descent. This is like moving up to a ten speed bike. You can "change gears" depending on whats needed to get the "most with the least". On take off you set the RPM to to max which is analogous to first gear. Once in cruise you can lower the RPM increasing the pitch angle and take big bites of air to pull (or push in some cases) your aircraft through the air with less effort on the part of the engine. Another advantage is if you have an engine out situation you can feather the prop, reducing drag and getting better glide performance in a single engine aircraft or lessent the effect of P-factor (torque) or the tendency of the aircraft to turn into the dead engine. All of this gives the pilot the ability to fine tune the power settings of the aircraft according to his/her current situation and needs.Which is better? I guess that depends on the mission you have in mind for your aircraft. You will find that most trainers use fixed pitch props due to a less complicated environment for the student pilot and lower maintenance costs. Aircraft designed to fly faster and farther will almost always be equipped with constant speed props and I cant think of a twin in production now that has fixed pitch props either.One thing to remember when adjusting your power settings on constant speed prop plane, when you are reducing power set manifold pressure, prop rpm, and mixture in that order. When increasing the steps should be reversed.Mark

[LAdamson 240]

>(Experts: Did I get it right?) Close enough!I'll add some more....The fixed prop is a compromise between climb and cruise settings. Cheaper, simpler, but still a compromise.The "constant" speed is like a variable gear shift. Great for full power (as altitude will allow) during takeoff, and like running in a higher gear at cruise. Can also work as an airbrake in the pattern by moving to low pitch position. In the case of the Cessna 182 which is not a full feathering constant speed, the blue knob controls a prop governor setting which allows oil under pressure to push against a piston on the front of the prop. The piston will force the prop with linkages to a coarser position. If a problem occurs that results in loss of oil pressure, the prop will return to a "fine" pitch with spring and air pressure. The oil enters the prop through a hollow section in the front part of the crankshaft, and the piston is in front of the prop, as the pic below shows.Full feathering props use other combinations of pistons & counterweights.L.Adamson

[Guest]

Thanks guys! This is exactly what I was looking for.Matt

[Guest]

I have a burning question on that subject that has had me wondering since I was a little boy:If one of Santa's reindeer dies suddenly on takeoff (heaven forbid) how in the world to you feather a reindeer?

[Guest]

If he is flying one of the older model sleighs (pre-1950), he better hope the other 7 (or 8) reigndeer have enough horsepower (deerpower?) to drag the dead one around.In the early 1950's, the sleigh manufacturers incorporated a deer-release mechanism into the harnesses. In between each deer is a small device consisting of a steel block, tube containing a detonator (actually a 9mm handgun bullet), and an electrode. This device is operated by a handheld controller manned by the sleigh driver. If Santa gets into trouble, providing he's quick enough on thr draw, he can use this controller to select and "punch" the trouble deer. When he presses the release button, an electrical charge get sent down the electrode, firing the detonator. The bullet in turn severs the harness against the steel block, jettisoning the deer from the pack. This system is very similar to the cable release mechanisms used in the rescue hoists of modern helicopters.Honestly, I don't think the first scenario is very likely. I believe most if not all of the older sleighs were retrofitted with the modern jettisonable harnesses in the 70's and 80's.

[Guest Lizardo]

Everything you ever wanted to know about propellers: http://www.avweb.com/articles/pelperch/pelp0016.html

[Guest]

This has got to be my favorite post of the month!

[Guest]

LMAO, the first liar doesn't stand a chance here, does he? :-))Sounds like a viable solution to a very sticky situation, though.Did you figure that out or is it in some chopper emergency check list?:-))