Power setting and attitude/trim weirdness...

[burncpt]

Hi Guys

 

I'm new to DCS but with a fairly solid understanding of flight dynamics, but I'm confused by the way the Spitfire (and probably the TF-51 which is the only other aircraft I have at present) react to power settings. Generally the rule would be "Power, Attitude, Trim" to get stable flight in level, climbing or descending flight, and I tried this with the Spit. After getting her at a 180mph climb to altitude, I reduce throttle thinking this will bring the nose gently down at which point I can re-trim when the speed stabilises. Instead, I get a wild nose-up attitude and without strong forward stick I'll stall out. Conversely, adding power often seems to result in a nose-down attitude and needing back stick and up trim. Seems all arse-about-face to me - is this a Spit thing or a broken flight model?

 

Cheers muchly

[zcrazyx]

Hi Guys

 

I'm new to DCS but with a fairly solid understanding of flight dynamics, but I'm confused by the way the Spitfire (and probably the TF-51 which is the only other aircraft I have at present) react to power settings. Generally the rule would be "Power, Attitude, Trim" to get stable flight in level, climbing or descending flight, and I tried this with the Spit. After getting her at a 180mph climb to altitude, I reduce throttle thinking this will bring the nose gently down at which point I can re-trim when the speed stabilises. Instead, I get a wild nose-up attitude and without strong forward stick I'll stall out. Conversely, adding power often seems to result in a nose-down attitude and needing back stick and up trim. Seems all arse-about-face to me - is this a Spit thing or a broken flight model?

 

Cheers muchly

 

Could be something to do with the CofG perhaps, similar to stall behaviour? i know someone has bought this up at some point but i cant for the life of me remember where the thread is, i'll try give it a look and see if i can figure it out, gotta remember these are warbirds though and not GA aircraft.

[burncpt]

Yeah I did have a good hunt around but couldn't find anything yet. It could be CofG, but I would have imagined these birds to be nose heavy if anything with an enormous engine out front! Thanks for your help :)

 

[Art-J]

Check if your elevator axis is not bound to your physical throttle (apart from joystick). Actually, delete all duplicated assignments in control settings tab - there will be lots of them and if you're new to DCS that's the very first thing you should do before trying to fly any plane.

 

When in cockpit, you can enable controls indicator by pressing Ctrl-Enter to see if all axes work as intended.

 

Also, remember there are two control tables for each plane - one for game flight mode, one for simulation flight mode, it's easy for novice player to configure one, then fly with the other by mistake.

[grafspee]

Do i remember it right that in game flight mode trim system is not working correctly ?

Yes and default axis and button assignments is just a pain for me, every time i set up controls.

[DD_Fenrir]

The Spit (and the 109 coincidentally) suffer from power on - tail heavy trim at low airspeeds/higher AoAs. Simply put, at these regimes a portion of the propellers thrust is actually vectored in the vertical and due to the neutral static stability of the airframe there is not enough inherent longitudinal stability to compensate naturally for this.

 

This manifests itself in the airframe "self-tightening" turns and loops as airspeed drops and is noted behaviour; Dave Southwood, a highly regarded modern era test pilot and a high hours Spitfire and 109/Buchon pilot mentions this very characteristic.

 

I suspect this is playing a part, though your description sounds more violent; can you provide a track file for review? Maybe we can work out what's happening.