Nose up Nose down

D

Draenog

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Hi Guys,
What is the cause of some flight models to nose down around 30 degrees when power is applied, then nose up about 30 degrees when the power is reduced, all the while fighting to keep it trimmed. The make of aircraft is totally unimportant other than it's a turboprop. I was just wondering if there is a number i can play around with in the cfg's and try to correct it?

Many Thanks

Gary
 
First thoughts...Have a look at fuel and payload, depending on the model , some will take on a nose up or down attitude, depending on how much fuel is in the fore and aft tanks. Also, some aircraft in FS will fly that way regardless, but it's more of a nose down attitude that catches my attention. Can you be specific... which model is it that you're seeing this with?


BB686
 
It is the position of the motor for center of gravity on the vertical axis.


[GeneralEngineData]
//0=Piston, 1=Jet, 2=None, 3=Helo-Turbine, 4=Rocket, 5=Turboprop
engine_type = 5
fuel_flow_scalar = 1.0
min_throttle_limit = -0.250000
engine.0 = 6, -8.84, 0.98,
engine.1 = 6, 8.84, 0.98,



I suppose an aircraft with such a configuration.
 
It can be quite difficult to arrive at a sensible value in FS9 - one can easily quote the vertical value of the prop or jet centreline relative to the fuselage centreline as drawn, but the zero datum for drag & weight (well mass) are not always at the same point. Most aircraft will have some effect on pitch with thrust (engine power) & one tries to establish that effect from pilots notes or actual experience & then adjust the vertical value to produce the desired effect. Then some aircraft designs have an angled thrust line to compensate & this value is rarely known without recourse to manufacturing drawings. So if you can find out how the real aircraft behaves with thrust then adjust the vertical value, if not you are just guessing (like most of us) at the effect!
Keith
 
Flusirainer said:
It is the position of the motor for center of gravity on the vertical axis.


[GeneralEngineData]
//0=Piston, 1=Jet, 2=None, 3=Helo-Turbine, 4=Rocket, 5=Turboprop
engine_type = 5
fuel_flow_scalar = 1.0
min_throttle_limit = -0.250000
engine.0 = 6, -8.84, 0.98,
engine.1 = 6, 8.84, 0.98,



I suppose an aircraft with such a configuration.
Click to expand...

Keith is right on with his explanation. In FS, the primary cause is the engine location as specified.

I usually place the engine .1 above for just a slight nose down with power applied.

The one stated above is about 11" above and would likely be the culprit.

Try .1 (feet instead of .98)) and adjust from there to your liking.
 
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