Turboprop fuel is constant at any alitutude, feature, bug or glitch?

[GoldForest]

While testing this prop passenger plane I made, I noticed that at no matter what height, the fuel was always (0.75) in use. Effective air speed and the flow both change, but the fuel usage does not. If I remember correctly, turboprops are like jet engines, so shouldn't the altitude effect fuel used? 

[mystifeid]

I can't remember ever seeing the turbo shafts having insufficient airflow. I think that fuel consumption is only affected by torque limit and rpm limit. You can change these in the engine PAW (right-click window) or you can assign them to axis groups. Even though you can use the main throttle axis group I've found that when using fine control (caps-lock), the custom axis groups provide very granular control compared to the throttle keys which seems to unaffected by the use of the caps-lock key. But maybe that's just my keyboard. (Note that by default there are no key-bindings for the custom axis groups - they must be assigned in the game settings under Input -> Vessel -> Axis Actions.)

Edited July 18, 2019 by mystifeid

[GoldForest]

3 minutes ago, mystifeid said:

I can't remember ever seeing the turbo shafts having insufficient airflow. I think that fuel consumption is only affected by torque limit and rpm limit. You can change these in the engine PAW (right-click window) or you can assign them to axis groups. Even though you can use the main throttle axis group I've found that when using fine control (caps-lock), the custom axis groups provide very granular control compared to the throttle keys which seems to unaffected by the use of the caps-lock key. But maybe that's just my keyboard. (Note that by default there are no key-bindings for the custom axis groups - they must be assigned in the game settings under Input -> Vessel -> Axis Actions.)

I did notice the throttle changed the fuel consumption. 

 

But if it is supposed to act like turboshaft, the fuel consumption should be effected by altitude like a turbine, since a turboshaft is a turbine.

[mystifeid]

3 minutes ago, GoldForest said:

But if it is supposed to act like turboshaft, the fuel consumption should be effected by altitude like a turbine, since a turboshaft is a turbine.

What about lowering the rpm limit so that it's still above the (reported) current rpm. Why does this lower fuel consumption?

Anyway, these are still new parts and as such they are probably still works in progress.

[bewing]

5 hours ago, GoldForest said:

But if it is supposed to act like turboshaft, the fuel consumption should be effected by altitude like a turbine, since a turboshaft is a turbine.

As I understand it, this is going to be a permanent limitation of the game. In order for the rotors to function the way they do, they can't use ModuleEngine. And only parts that use ModuleEngine can have altitude-based thrust curves. So no can do.

[GoldForest]

5 hours ago, bewing said:

As I understand it, this is going to be a permanent limitation of the game. In order for the rotors to function the way they do, they can't use ModuleEngine. And only parts that use ModuleEngine can have altitude-based thrust curves. So no can do.

So it is a feature/semi-bug. Okay, thank you for the information.

[pincushionman]

On 7/18/2019 at 10:31 AM, GoldForest said:

But if it is supposed to act like turboshaft, the fuel consumption should be effected by altitude like a turbine, since a turboshaft is a turbine.

This sounds wrong to me. Isn’t fuel consumption controlled only by throttle, with thrust/power and efficiency being what changes with altitude and speed?

Rockets used to also vary fuel flow with pressure, but that was changed because the pumps and injectors don’t care what the pressure is.

Edited July 20, 2019 by pincushionman

[GoldForest]

28 minutes ago, pincushionman said:

This sounds wrong to me. Isn’t fuel consumption controlled only by throttle, with thrust/power and efficiency being what changes with altitude and speed?

Rockets used to also vary fuel flow with pressure, but that was changed because the pumps and injectors don’t care what the pressure is.

While you are correct that throttle does effect fuel consumption, fuel consumption is also effected by altitude. Fly a plane with jet engines. Look at the liquid fuel consumption on take off, then climb up to 5000m, you'll see a significant fuel decrease with little to no thrust loss. This is how it also works in real life and why planes want to fly as high as possible. The higher the plane, the better the fuel savings.