OK, someone direct me in the direction of a thread or website that explains the difference.. like flight limitations, ease of learning, the mechs of etc... My Blade CX flew away into the dark grey Sky's to never return and I am at the next step beyond coax..FP or CP? I just need to research the difference. Thanks for any help.

KyMoonshine

FP: Fixed pitch. Altitude is changed by adding or decreasing main rotor speed.
CP: Collective Pitch. Altitude is changed by adding or decreasing main rotor speed and main rotor pitch angle at the same time or seperatley.

If you done the CX which is FP, I would suggest moving onto CP since all the bigger Helis use it.

A collective pitch machine maintains a constant rotor rpm regardless (unless you are landing and spooling down). The advantange is if you are descending and need to add power, on a FP machine you have to wait till the rotor spools back up before it starts providing more lift, often the helicopter and the ground become at one with each other before that happens.

The only two disadvantages to CP are the rotor head is more complicated and the throttle/collective stick is more sensitive. Both of which are far outweighed by the performance advantages. Also a FP machine is not capable of anything but the most basic aerobatics.

... "adding or decreasing main rotor speed" ... uhhh ... Not quit ... that would be fixed pitch (FP).
Ideally, the goal for CP helis is to have a constant RPM

It would have been a little more accurate to say this:
Altitude is changed by adding or decreasing engine power output (throttle) and main rotor pitch angle at the same time or seperatley while maintaining a constant RPM.

Oh. I have a Caliber 3 and on my 9chps it has a pitch curve AND a throttle curve. I just thought that it meant that the main rotor speed was changing because the engine speed was changing...

Remember the basic formula where power output and load produces a specific RPM.
Power Out (throttle) / Load (pitch) = RPM (for the most part). Notice that RPM is proportional to Power Out (ie increase in power = increase in RPM). Load (pitch) is inversely proportional to RPM (ie increase in load = decrease in RPM).

This means if you change just one component (power or pitch), the result will be a different RPM.
If you vary both components (power and pitch) to the same effectivity (ala power and pitch curves), the RPM will remain constant.

So, with the power and pitch curves in sync, as you increase the load (pitch), RPM should drop, however, you are adding an equivalent (hopefully) amount of power to counter the higher load. The result? ... constant RPM.

This is why you can accelerate your car. You are applying more power than resistance which increases the wheel RPM. You "think" that the throttle controls speed but it only controls power out. Physics controls the speed.

Oh. I understand (I actually do!). So even though the engine starts to whine harder it is just countering the pitch load. Thankyou for that explanation.

If you hear the engine bogging then you are using too much pitch for the throttle setting or the engine is capable of supporting, this btw is bad for your engine, its telling you to back off.

Bogging? What do you mean by that? I meant by whining harder the noise goes higher or lower in pitch (sound pitch)...

The noise your engine makes is proportional to the power it is making. Ever notice how 90 size engines seem a little louder than 30 size engines.

Bogging = drop in RPM due to the engine struggling with the load it is working against. Remember, the goal is to maintain RPM.

Bogging occurs anytime you apply a load to the engine where the current power output will not be able to maintain RPM. (ie drive your car up hill without adding more power ... the load starts winning and your engine RPM drops). So, to "fix" bogging you have to either decrease pitch/load (ala barracudahockey) or increase power output. If you are at full stick, increasing power output may not be an option since the throttle position will be at or near 100%. Assuming near max throttle, bogging can only be fixed by lowering the pitch/load.

This is why the power and pitch curves must be "tweeked" for best performance from 0% to 100%.