Cessna 206 help

[IL VATE]

I need an advice from anyone with more experience on 206 or constant speed prop.
I operate in a place where I cant get anything decent and reliable.
A 206 40 years hold with a new engine fitted, during t/ o cant get more than 2200 rpm everithing forward, at see level and 20 deg oat.
Maintenence said no problem, but they cant state that is the gauge that underread.
In the climb out after t/o the ROC reads 700' but the prop is still fully frw and it cant be decreased, straight and level performance looks ok, but still with prop fully frw.
Please any idea is welcome.

[Nightfire]

On a brand-new engine, this definitely shouldn't happen - with an old one, it could have many different reasons. Assuming that everything on the engine is fine, as it came straight from the factory's test-stand:

You are probably still using the old propeller, right?

I'm not a mechanic, so just guessing, but the Nitrogen-pressure may be low. Otherwise, it may mean that there is not enough oil pressure for some reason.

Does the problem get better or worse after a while, once the engine has warmed up?

[IL VATE]

It looks like it doesnt change at all.

[Nightfire]

It looks like it doesnt change at all.

So that excludes an oil leakage then.
Well, 2200 RPM is definitely not enough, you should have 2500 to 2650 or so.

Before you start dismantling the engine, check the prop, and ask the mechanics to check the oil pump pressure output as well.

If it's not that, then there may be a fault in the engine somewhere, which would be a case of warranty. Are you using the Conti, or the Lycoming by the way?

Perhaps you might also try posting this question in the tech-section of this forum.

[IL VATE]

It is Lycoming.

[Cardinal Puff]

Nightfire

What nitrogen?

Il Vate

Have it strobed to verify the rpm.

[Der absolute Hammer]

Well, the oil in an unfeathering accumulator is normally charges with air compressed or nitrogen. But that is not relevance to a C 206.
The C206 standard was Continental 260/300hp fuel injected engine with a variable speed propeller? Now replaced with a Lycoming fuel injected and still with a constant speed, variable pitch propeller? So a completely silly thing like carb heat enters not in the equation.
I would not want though to go around in an a/c that should prodice 2,600 RPM at take off power and instead produce 2,200RPM. That is a reduction of 15% power. Is a beeeg penalty.

[Nightfire]

What nitrogen?
Well, the way I know the systems on other planes, there is a nitrogen-pressured cylinder, located under the spinner. Maybe it's not the same on a 206; as I said, I'm not a mechanic. The compressed gas works like a spring, and tends to feather the propeller, while at the same time the supplied oil pressure from the running engine will vary the prop-pitch. The oil-pressure on one side and the pressure-cylinder on the other adjust the angle of the prop-blades, and thereby the RPM.
So if the engine delivers less power, the oil pressure drops, therefore the prop-pitch will decrease, therefore there's less aerodynamic resistance, therefore the RPM remains constant. And vice versa.

If there were not enough N2 in the cylinder, the propeller would turn too slow.
And likewise, if the N2-cylinder is over-filled, or if there is not enough oil pressure on the other side, you wouldn't reach the required RPM. (Which is also the reason why, if you were to lose all the engine oil, you would also lose all your thrust).

As I said: On an old engine, there could be many, many reasons for this problem and it would be impossible to tell without examining the motor.
But if the engine is brand new, it's more likely that the problem comes from somewhere else. And the prop is the first thing that I would guess.

Just my two cents.

[Cardinal Puff]

Why would the propellor on a single engine aircraft need to be feathered?

Hammer has it.

Strobe it to verify the RPM on the gauge. If there's a discrepancy, check out the setup of the CSU.

[AviatorJack]

Does the prop go past 2200 as you apply full power on ze takeoff run then settle down back to 2200? If so it could be a crack within the crankshaft. I've had the problem twice in the past. If there is a crack then too much oil could be pissing into the crankshaft and would give you a problem with RPM or on the other hand it could be a dodgy gauge. Get that checked first and monitor your oil consumption.

Sometimes these things can be the simplest of problems. Long live the 206............

[IL VATE]

It looks it is sorted guys....it was the cable running aroun the engine insted of going straight to the governor.....now we have 2600 rpm back!!!!
Thank all of you for your help...anyway if you have any spare material in Pdf woud be great, in this part of the world ther is nothing!!!!!
Thank again

[Yellow & Blue Baron]

Which part of the world are you in out of interest?

[IL VATE]

...somewere in meadle east...mate.Can't be more precise.But thanks all of you guys!!!