FSX Stratojet Excalibur pitch problems?

With autopilot on at cruise level, if it's pitching up and down or 'porpoising', the pitch moment of inertia or MOI could be too high. Look for the [WEIGHT_AND_BALANCE] section in the aircraft.cfg, then look for the "empty_weight_pitch_MOI=" entry. Edit it as per the example below:

Change:

empty_weight_pitch_MOI=5020933.91000

To:

empty_weight_pitch_MOI=4020933.91000

Then test again. If the porpoising has reduced, subtract another 1 from the MOI and test again until the porpoising stops.

If the porpoising has increased, add another 1 from the MOI and test again until the porpoising stops.

I fly the Stratojet Excalibur often, a favorite imaginary supersonic business jet with 2D wide aspect panel by Philippe Wallaert. Thank you, Philippe!

I stopped the porpoising by modifying these two values, a somewhat simpler technique that yields good results on this and other planes that needed it, though the two values require testing. Every plane model is different. Be sure to make a backup copy of the original aircraft.cfg.

[flight_tuning]

elevator_effectiveness=0.9

pitch_stability=3.0

You did not say which zip file name you are flying. There were 2 zips. One for FS9 and one for FSX.

'stratojet_excaliber-1.zip' ......9,195 Kb, 01/19/2014........is for FSX.

'sj_ex_2.zip' ......................12,743 kb, 10/22/2006.........is for FS2004.

I have this jobbie. Did not work on sicne 2014. But for starters the MOI's are thus:

empty_weight_pitch_MOI = 250000.000

empty_weight_roll_MOI = 200000.000

empty_weight_yaw_MOI = 200000.000

empty_weight_coupled_MOI = 5000.000

Try those. Also do you have this:

[pitot_static]

vertical_speed_time_constant = 1

pitot_heat=1.000000

I will fly it tonight. Got chores right now. Will report back tomorrow. The last time I flew it (2018) it was perfect as perfect can get - for being freeware. Heyart and Walert (spelling?) did top notch job on this one. That is why I mentioned FS9 -vs- FSX version. Get the right one then try it. Cheers.

Chuck B

Napamule

Edit: And another thing: If you don't have the C-172 as your Default Flight (loaded at FSX start) then that WILL be your 'problem'. Believe it!

...should I edit the vertical speed time and pilot static sections...

No. vertical_speed_time_constant only controls the lag of the VSI.

If you are playing with the MOI numbers you have to be careful when reducing them. Once you are below the FSX calculated numbers you can run into serious problems, especially when on ground.

Actually you do not have to do anything. I flew it and it is a little sluggish. Takes a while to get up to speed but otherwise it is PERFECT as perfect can get as is. Payware quality. Case closed.

I believe your problem is not having the C-172 as your 'default' start up flight (when FSX first loads).

Chuck B

Napamule