Question for B1900 Drivers

[pile_it]

Okay, so I'm doing some studying to prepare for initial ground school in a couple weeks and I just have a question regarding systems.

I'm reading about the autofeather system, if it's armed properly it will kick-in below 250 ft lbs torque and drain oil from the prop hub. Elsewhere, it mentions if there's a primary governor failure and the prop lever's aren't full forward, the fuel topping governor will kick in and significantly reduce fuel flow to the engine, which can appear much like an engine failure, until the prop levers are moved forward and the overspeed governor kicks in.

My question is, in a situation where there's a primary governor failure and the prop lever's aren't full forward, is it possible for the fuel topping governor to reduce enough fuel to the engine to the point that it's below 250 ft-lbs and have the auto feather kick in?

[Scuba_Steve]

FTG is a function of the primary gov. So if the primary goes you won't have a FTG, hence why the checklist tells you not to pull rev on landing if the primary gov fails.

Enjoy the 1900 it's a fun airplane.

[tca]

I don't fly the 1900 so I can't answer in specifics, but in the event the ftg reduced your engine to minimum fuel flow, and the autofeather was armed, you could definitely trigger autofeathering. But since the engine is still running, as the prop rpm decreases, the torque will increase and likely will exceed the autofeather threshold, so it will disengage. The prop will then begin picking up speed again, and if still at min fuelflow, your Tq will drop below the autofeather threshold again and try to feather. (you see this effect when doing the autofeather test on the ground). Thus cycle will repeat until you do something to stop it.

Now wrt the ftg, based on the installation I familiar with, if the prop levers are in cruise, the rpm at which the ftg kicks in will be lower than the rpm at which the overspeed gov takes effect. So if the primary gov failed to keep the prop on speed (ie the gov works properly but there is a blockage in the oil line etc), once the rpm reaches the ftg threshold (6% above desired rpm in my case) the ftg will reduce fuel flow to minimum to bring the prop back on speed. Once the prop is back on speed the primary gov should disengage the ftg and fuel flow returns. So autofeathering should not be a concern.

In this scenario, the ftg coming on and off may feel like the engine is surging, so advancing the prop levers to a pout where the overspeed gov takes effect is probably ideal.

Once again I can't give exact figures for the 1900 and there may be some differences from my installation, but I imagine it is pretty similar!

[tca]

DP. Sorry

[pile_it]

Thanks tca! That deininitely clears things up. It shounds like the system you're describing is identical to the 1900 (ftg maintains RPM 106% of selected value in the air, and 96% on ground). I assume you're a King Air driver?

[tca]

Thanks tca! That deininitely clears things up. It shounds like the system you're describing is identical to the 1900 (ftg maintains RPM 106% of selected value in the air, and 96% on ground). I assume you're a King Air driver?

You assume correctly. I know that the 1900 and the king airs share many similarities, but there are enough differences between models that you can significantly confuse somebody by explaining systems in a model that they don't fly! See a thread a while back about starting procedures; cross gen starts may work fine in the 1900 but is pretty well guaranteed to fry the current limiters in my (older model) king air.

Good luck with your training, hope you enjoy!

[MZUNGO]

(ftg maintains RPM 106% of selected value in the air, and 96% on ground).

just to clarify the ftg limits the engine speed to 96% in BETA, not just because the airplane is on the ground.
you could in theory pull the power levers into reverse in flight, I dont recomend it and you would only do it once. the low pitch solenoids limit the torque when the weight is on the wheels.
during beta operation the prop cannot control its speed by increasing the blade angle, so the ftg limits the N1 speed by bleeding off Py air from the fuel control.

as far as technical questions on the 1900 go I should be able to answer any that you have.
dont hesitate to ask