Left Yaw during take off 1.2.0

Either the Trims are too effective or left yaw are not quite correctly simulated yet.

In the real P-51D You had to set appr. 5 units of right rudder trim and a small amount of down elevator for the take off run and still need some right rudder to counter the yaw.

In DCS P-51D This causes an aggregated right yaw once setting take off power.

A setting of 1.5 units seems to work quite Ok.

With all trims zeroed it´s easy to take off. Only a small right rudder input is required.

...and yes I did deselect "simple flight model" during installation and doesn´t have auto rudder enabled under P-51 options.

Also no Take off help.

FinnJ

This is a hot topic of discussion internally at the moment. The debate rages on...... :)

Nate

This is a hot topic of discussion internally at the moment. The debate rages on...... :)

 

Nate

Lol

Comming from the A2A P-51D the flight model doesn´t seem that far different.

Only the torque induced yaw seems different (I won´t say wrong).

A2A have Dudley Henriques as advisor, who is a real life P-51 pilot.

That doesn´t mean that they got the FM 100% right, but following the realworld checklist in terms of trim setting works very well.

FinnJ

Don't forget TFC/ED actually own and fly a P-51 - but that is not to say the current implementation is correct - it is still a Beta.

Nate

may i mention in 1.2.0 that any trim adjustment does not get shown on the controls indicator when on the ground, it seems fine when airborne.

Have you rememberd to disable autorudder fjacobsen?

Have you rememberd to disable autorudder fjacobsen?

Yes...

As I told...

Autorudder off, no take off help and "use simplified flight model" unchecked during install.

I get left yaw during take off, but it´s too easily rectified with right rudder.

According to realworld P-51D manual You need appr 5 untis of right rudder trim input and then still need to feed in some right pedal to counter the Yaw.

FinnJ

The limitation you would be up against without the trim would be that you are simply not strong enough to provide the pedal force needed to counteract the yaw without the trim.

It still seems we are able to deflect the rudder to the stop throughout the take-off roll, even though the change list said rudder hinge moments in yaw and roll are now implemented.

This means the need for trimming as in real life is effectively eliminated. However, I think you will see this being corrected shortly.

Now, a bit of a rant on the subject. Bear with me.

For trimming to work as in real life, a force-based control implementation is required. This means that for a given deflection of the joystick/pedals, your virtual self applies a given force to the virtual controls, affecting them accordingly. Full joystick deflection to the side would mean e g 30 lbf applied to the stick of your virtual Mustang. At low speed, this means full deflection of the ailerons. At high speed, the ailerons will barely move. This is true to life – at high speeds, the controls pretty much feel like they are set in concrete.

This does not, however, mean that the aircraft cannot be manoeuvred. The deflections required for a certain roll rate or G loading decrease with increasing airspeeds, so things even out more than a bit. The same force tends to give more or less the same reaction from the aircraft over the speed range.

To have a model not based on control forces, on the other hand, means it will be very hard not to overcontrol the aircraft at high speeds. This was a problem when powered controls arrived in real aircraft. Suddenly, the hydraulic actuators could deflect the control surfaces fully at all speeds, which meant aircraft which were dangerously difficult to fly. One moment of hamfistedness, and you’d break the aircraft apart in the air.

To remedy this situation, q-feel systems were introduced. These systems artificially increase the control forces as airspeed increases. Without them, aircraft will not be certified for flight.

These days, fly-by-wire is all the rage, with computers interpreting the pilots control inputs and deflecting the control surfaces accordingly. Again, it is all based on force. x lbf of force gives y Gs. Never “x degrees of stick deflection”.

Finally, a bit of physiology:

We are not able to sense the position of our limbs with any precision at all. We may think we can, but what we really feel is the force we are using to hold our limbs up against gravity. We have learned to interpret these forces as positions. In zero-gravity, we typically do not know the position of our limbs if we can't see them.

We are, however, very good at sensing forces. Hence, control feedback is based upon forces applied rather than control deflections. Check the certification requirements for aircraft. It is all about forces. Also check the P-51D manuals, where they talk about the effect of flying with a full fuselage tank. It's all about control forces, nothing about "stick forward" or "stick aft".

Conclusion

Knowing this, it can be concluded that the only viable method of modelling the controls of an aircraft with conventional controls is a force-based model*. Most here are probably familiar with the Il-2 series, which has this. It is simply the simulator equivalent of providing us with the q-feel systems, which are mandatory in aircraft which, like our simulation, lack direct feedback through the control linkages.

As the devs talk about rudder hinge moments, I think force-based is the way we are headed. We may even be there already for all the limited testing I have done of the latest version, just that the parameters aren’t tuned.

When we do get there, you will find trimming for takeoff working the way it should.

Cheers,

Fred

*) One notable exception to this would be Rise of Flight, which does not have a force based control model (last I checked). They get away with this due to the very limited speed range and the very light control forces in most of the aircraft modelled. Control forces simply aren’t the limitation it is in a 500+ mph Mustang when you are plodding along in a Sopwith Camel.

To have a model not based on control forces, on the other hand, means it will be very hard not to overcontrol the aircraft at high speeds. This was a problem when powered controls arrived in real aircraft. Suddenly, the hydraulic actuators could deflect the control surfaces fully at all speeds, which meant aircraft which were dangerously difficult to fly. One moment of hamfistedness, and you’d break the aircraft apart in the air.

Very interesting post effte. My understanding that the principal advantage of the F-86 against the MiG-15 was the former had power controls and the latter did not. That meant that if the MiG-15 did not beat you within the first turn or two then the MiG-15's slightly superior performance would drop as the pilot became fatigued and then the F-86 could capitalize on this. So there are ups and downs to powered controls.