correct as is F16 doesn't taxi straight with asymmetric loadout

[Snakedoc]

As per title,

anytime an asymmetric loadout is used, the aircraft doesn't taxi on the ground straight requiring constant rudder adjustments. At low speed the parasite drag generated by any stores is virtually none so it shouldn't have any impact on the yaw moment

This is evident also if any pod is loaded on the left or right hardpoints but not as much like with different weapons.

I've attached 2 tracks. One with a clean aircraft which taxi straight with no rudder inputs, a second one with an asymmetric loadout to highlight the issue.

 

not sure if it's related to an old bug which was fixed in DCS 2.9.5.55300

 

DCS: F-16C Viper by Eagle Dynamics

• Fixed: Wheel friction imbalance.

F16 asymmetric loadout bug during taxi.trk F16 no bug on taxi without asymmetric loadout.trk

Edited August 21, 2024 by Snakedoc

[Lord Vader]

Hello @Snakedoc

We've analysed your track and concluded two things:

1. The amount of induced compensation for steering is not really that big. It may be a matter of your personal taste but it's actually in line with such an asymmetry you selected to use.
2. Of course you need compensation with such a weight on the right side. You must account for the extra wheel friction on the right side, especially above 20kts as you demonstrated in your track (about 35kts).

All in all, the team feels this is working correctly and no change is needed.
It's also generally speaking, common sense, that the F-16 should not be too asymmetrically loaded, at least not with such a difference of more than 1000lbs. 

 

[Snakedoc]

Ok thank you 

I was testing out a mission which came with a pre-loaded asymmetric loadout and noticed it.

thanks for clarifying 

[FusRoPotato]

On 8/23/2024 at 4:57 AM, Lord Vader said:

You must account for the extra wheel friction on the right side

 

It's not that simple. There's a lot of things that need to be considered, especially the experience and report of pilots. That nose gear is held in position with an actuator that uses position integration logic, meaning you don't have to account for the extra force because the actuator does most of that on its own. There are accounts of it being very difficult to steer via the brakes when NWS was engaged.

There were some situations when NWS would occasionally turn off if the aircraft was too light. They had to use brakes for steering, and in this condition, would notice sticky brakes. There is also a geometric consideration implemented for hard landings to stabilize the aircraft when one wheel touched down first. To help prevent roll over on hard touchdown, the camber shifts on the main gear during depression and becomes more positive. Additional to that geometric gear design, the lean of the aircraft itself also contributes to more positive camber on the heavy side and more negative on the light side. This causes both tires to push slightly in the direction of the heavier weight and results in a countering yaw. Heavy left wing -> positive left wheel camber -> right yaw. However, the moments produced by these effects are far too weak to overcome the actuator. A strong sidewind is much more likely to cause problems than any of those, especially tire drag. Tire drag to weight isn't typically documented or studied because they are usually negligent compared to tread patterns, speed, and temperature more than anything, and are very small forces in total.

I think you are making assumptions of physics that are more in-line with cars that have flat tires and no power steering. You give your overweight friend a ride and suddenly realize you have to hold a slight tug on the wheel. Older aircraft like the Phantom and Warbirds were known for this because of older tire designs and manual linkages, but the Hornet and Viper were not known for it.

Edited September 9, 2024 by FusRoPotato

[Lord Vader]

Hi @FusRoPotato

We appreciate personal opinions, especially when they are based on real life experience, of course.

However, with the issue above, as well as with the track that was tested with the team, it was concluded that no fix is required for the conditions demonstrated.

If you have any evidence to present showing the situation above is not accurate, feel free to PM that evidence (making sure it's publicly available non-classified data) to @BIGNEWYand we'll certainly look into it. 

[FusRoPotato]

I don't think it would be appropriate as I'm not here to argue to what degree of fidelity this sim should be at, especially if the devs themselves are not interested in the subject. If it's more a matter of finding reasons to avoid investment, it's probably best left as is.