Momentum drag for VTOL aircraft

[tridge]

In a VTOL aircraft like a quadplane momentum drag from vertical rotors is very important for slowing down the aircraft in a back-transition. I can't seem to get this to model at all realistically, testing in RF9.5.
I've been testing on this model:

SITL_Models/RealFlight/Released_Models/QuadPlanes/Alti_Transition_QuadPlane at master · ArduPilot/SITL_Models

Models of aircraft for SITL. Contribute to ArduPilot/SITL_Models development by creating an account on GitHub.

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We use a trick in ArduPilot where we startup the VTOL motors early to slow the plane before we start the descent for landing. I'm not seeing the deceleration that I expect.
Looking at the physics settings in RF9.5, there is a "Lateral Drag Factor (%)", but raising that to 200 doesn't seem to have any impact. Maybe it doesn't work for rotors that are rotated to point up?
I also notice that in the builtin E-Flite convergence model that this factor is set to zero which seems odd.
Is there some way to get the lateral drag effect of the spinning rotors working for this type of aircraft?
Cheers, Tridge

 

[uncle twist]

Didn`t you have another thread regarding this plane, I seem to recall one where,....it would appear that the problem you`re referring too,.. wasn`t an issue....that plane appeared to be able to fly and land vertically without a problem...???

 

[tridge]

Didn`t you have another thread regarding this plane, I seem to recall one where,....it would appear that the problem you`re referring too

yes, it flies pretty well, but it doesn't accurately reflect the real vehicle for this aspect of the flight. So it ends up having to pitch up more than it should when landing to slow down.
The reason it matters for me is I am adding more features to ArduPilot to take advantage of the momentum drag which greatly impacts the timing of landings. It would be nice to be able to test those features in RF9.
It isn't a big issue, I just thought someone might know how to adjust the physics settings to get this sort of drag.

 

[uncle twist]

Have you tried increasing the frontal drag on the fuse/wings... (I`m sure have).. that`s just the first thing that comes to mind for me...but there`s an infamous amount of things that you can try in the editor,... it can actually kind of mind boggling.

 

[tridge]

Have you tried increasing the frontal drag on the fuse/wings.

the drag when the vtol props aren't spinning is OK already, the issue is the lack of additional drag when motors start spinning.
The vtol motors act as a type of airbrake. That is a problem when doing a fwd transition as it means you need a bigger fwd engine to get past the "transition drag" and get to fixed wing flight speeds. It is a good thing when doing a back transition though, as it allows you to rapidly slow down without pitching up.