Constantly c.800fpm up, then similar down to maintain cruise altitude. Is this a fault in the FDE or is it fixable in aircraft.cfg or elsewhere? (I am guessing the former).

 

Thanks.

Aircraft type and model? Are you running on autopilot?

Is the aircraft correctly loaded ... the centre of gravity IS important.

Martin, it's impossible to help you without more info. 

 

Please give us the specifics of the aircraft model, plus the altitude, airspeed and weight during this problem.  Are you using AP and/or autothrottle?  Add anything more that you can think of.  Otherwise, all you will get are more responses like this one.

 

Regards,

JerryH

Will send more information ASAP.. Thanks.

The aircraft in question is the Dreamwings Embraer 145.

The MCP is obviously slightly different for this aircraft (from Airbus & Boeing) and I maintain speed manually with the throttles. I use the VS option to select a climb rate and the A/P levels the plane off at the selected cruise altitude. It thereafter pitches slowly up and down to maintain this, as I indicated. Doesn't seem to matter what altitude I choose - the same thing happens. It was 28000' yesterday.

I have attached a screenshot of the load indication. Is the load too far forward? I have searched online (and in the FS information in 'Learning Center' but haven't found out exactly where the CG indicator is supposed to be. Amazing how many things one discovers one doesn't know., even after over a decade of flightsimming!).I can bring it back a fraction by reducing loads in stations 1-3., but only fractionally. The loads are the 'default' Dreamwings setup BTW, I haven't changed them.

The .mdl files are from 07/2004 and the .air file is dated 20/06/2004. I can't locate any updates

Any other info I have forgotten? Thanks again..

Martin


Hmmm. can't get my screenshot (111kbs) to upload - keep getting error messages ('upload failed'. Trying again...

... from the aircraft.cfg:

[WEIGHT_AND_BALANCE]
reference_datum_position=0.000000,0.000000,0.000000
empty_weight_CG_position=0.000000,0.000000,0.000000
empty_weight=26694.000000
max_gross_weight=48501.0000
empty_weight_pitch_MOI=1272439.000
empty_weight_roll_MOI=1162183.000
empty_weight_yaw_MOI=1137024.000
empty_weight_coupled_MOI=1300.000
CG_forward_limit=0.000
CG_aft_limit=1.000
max_number_of_stations=8
//Weight-Fore/AFT-Right/Left-Up/Down
//Cabin
station_load.0=1400.000000,20.000000,-3.000000,4.000000 //FWD Left
station_load.1=1400.000000,20.000000,3.000000,4.000000 //FWD Right
station_load.2=1400.000000,0.000000,-3.000000,4.000000 //Center Left
station_load.3=1400.000000,0.000000,3.000000,4.000000 //Center Right
station_load.4=1400.000000,-15.000000,-3.000000,4.000000 //Rear Left
station_load.5=1400.000000,-15.000000,3.000000,4.000000 //Rear Right
//Baggage Cmpt
station_load.6=960.000000,20.000000,0.000000,-2.000000 //FWD
station_load.7=960.000000,-15.000000,0.000000,-2.000000 //Rear
 

Are you using real world weather or a weather engine, such as Active Sky or one of them? If so this could be just the signs of severe turbulence. check your wind direction and speed, that should give you a clue. then again, it could be the oat or tat, if it is a high oat or tat at high altitude then your engine is not getting enough air to produce the needed thrust.

Yes, I use Active Sky, but the pitching is smooth and slow, not the kind of 'bucking' you get in turbulence: and I get it if I close AS6 and fly calm weather via FS9. But thanks for the thought.

Also, as I stated in my previous thread, check the OAT/TAT temperature.  If you have a high OAT/TAT at altitude, then you are not getting enough thrust, thereby entering into a stall then recovery situation.  these are most times smooth and not an abrupt situation.  Again, just a thought.

.. the plane is flying way above stall speed by this stage - 300KIAS maybe. It's a flight dynamics problem, I am almost sure.

I seem to remember that FLUSIFIX has amongst its many tweaks one that addresses the very problem of aircaft pitching up and down at cruise altitude.

I don't experience this issue when using airliners, but get it all the time with low level GA flights or aircraft like the DC3 ,but this behavior seems to be in response to constantly changing barometric air pressure changes below 18000ft that occur in FS9 .

Anyways some thoughts ,but you could check out Flusifix.

Cheers Andy

OK, I already have it installed on my PC - I'll check it out. Thanks

Thanks for providing all the details.  Before reading through your comments, I thought it could be a problem with a sloppy autothrottle and variable airspeed that caused the altitude changes.  But you said the throttle is set manually.

 

My guess at the moment has to do with pitch control or stability that can be tweaked in the aircraft.cfg file under the [flight_tuning] section.  I would try one or all of the following parameters:

-  pitch_stability

-  elevator_effectiveness

-  elevator_trim_effectiveness

 

The default value is 1.0 for all of those.  My technique would be to change each value individually and run a test flight.  Double the original value for starters to see if it makes a difference.  If so, you can fine tune it later.

 

If pitch_stabilty changes don't help, for example, set it back to the original value and try the next item.  Be sure to back up the aircraft.cfg (or take good notes) before you mess with this.

 

The problem could be caused by one or all or none of the above.  Good luck.

 

Regards,

JerryH

Yes, I will do that, a bit of trial and error.

 

I did try changing this value, which I got from "FLUSIFIX" (I had forgotten how useful this 'little' (not so little) programme is:

 

[pitot_static]
vertical_speed_time_constant=1

 

I changed the value from 1 to 10, then 20 and found that the pitch wavering was a lot less - down to about 50fpm up and down: a lot, lot better than the previous 800, but still visible. I have now changed this to 100, the maximum value allowed, but have yet to experiment to see if this has unwanted side effects.

 

I will post back any results anyway. Thanks for the advice.

 

Martin

It's a long shot, maybe, but try reducing speed when at cruise altitude.

 

A long time ago I noticed this 'hunting' could be caused by an overspeed condition and completely eradicated when throttles were reduced  Could also be I was ham-fisted in those days too.  :lol:  :wacko: