[Resolved] Overbanking tendency and BLIM

[Cake]

The hornet has a pronounced overbanking tendency in landing configuration when approaching or passing thirty degrees of bank angle. I'm not sure why the FBW system doesn't properly cope with this.

 

That said, the documentation I've read indicates that bank can be limited to 30 degrees using BLIM. I've tried setting this by boxing BLIM (and tried the various BLIM levels or settings), but none of them seem to have any effect. I must be missing some step for this. Anyone have any luck with this or might be able to tell me what I'm missing/doing wrong?

[M1Combat]

My guess is that it's WIP.. but I'm not sure.

[WildBillKelsoe]

Bank limiter is not yet implemented. How did you turn it on?

[Manuel_108]

The Hornet has a bank limiter?

[AvroLanc]

The bank angle limiter, only applies for when the auto pilot is engaged. It limits bank angle to 30 (NAV setting) or 60 degrees (TAC setting).

 

It might get implemented when 'Coupled' A/P mode gets added, along with FD bomb mode. Not sure how you selected it, because the push button doesn't work atm.

 

In any case, it won't help you in the landing config.

[Cake]

Bank limiter is not yet implemented. How did you turn it on?

 

AC Data page. You can box it and repeated clicks goes through multiple BLIM options.

[Cake]

The bank angle limiter, only applies for when the auto pilot is engaged. It limits bank angle to 30 (NAV setting) or 60 degrees (TAC setting).

 

It might get implemented when 'Coupled' A/P mode gets added, along with FD bomb mode. Not sure how you selected it, because the push button doesn't work atm.

 

In any case, it won't help you in the landing config.

 

Understood. It was mentioned in the DCS manual on page 28 regarding the autopilot, but it wasn't clear to me that it works under autopilot only.

 

It's too bad, because the overbanking tendency is unfortunate and surprising to me for a FBW aircraft.

[Druid_]

Its called negative roll stability. It should be neutral. It has been reported and will be fixed at some point.

[Cake]

Its called negative roll stability. It should be neutral. It has been reported and will be fixed at some point.

 

Glad to hear there is a fix in.

 

I'm not sure the problem is negative roll instability as you suggest - At least not the problem I am seeing.. In fact, in the clean configuration I observe neutral static and positive dynamic stability with a very mild under banking tendency - even at steep bank angles.

 

The Hornet FCS is supposed to monitor pilot input & aircraft motion and apply control laws to command control surface movements. Guess what, regardless of a given configuration, the control surfaces do not really respond at all, much less in the required manner to prevent OBT during flight in the landing configuration I would expect some type of response by the FCS to this, but it does nothing. The control surfaces do not move at all unless I move the flight controls or change speed/AoA! The exception is that if If I crank the turbulence setting up to max I will get a lot of rudder adjustments made by the system but only minor aileron adjustments and I'm not sure if they compensating displacements around the longitudinal axis, yet the Hornet seems well-damped and I would expect aileron inputs to help accomplish this.

 

Moving back to the landing configuration... On speed at any bank angle, I have to actively incorporate opposite roll inputs to maintain the desired bank angle. The steeper the bank, the greater the opposite input required. With the correct input, I am not noticing any roll instability, only the overbanking which the control logic ignores.

 

In summary, the problem seems to be a failure of the FCS to issue the proper control commands on its own - If I can fix the bank, the airplane should do better on its own.

[Druid_]

@Cake

 

Clean aircraft has neutral stability.

 

Once in PAM landing configuration the aircraft once rolled will have a tendency to continue it's roll in the SAME direction. This is what's called negative roll stability. (Had it wanted to roll back to wings level then it would have positive roll stability. The same logic is applied to pitch and yaw).

 

I'm not sure what control surface movement you are expecting the FCS to make once configured? Are you suggesting that should a gust pick up a wing the aircraft should automatically deploy control surfaces to alleviate the unwanted roll tendency? If so this is not something programmed into the Hornets FCS. (BTW fly-by-wire Airbus aircraft do this however Boeing aircraft do not).

 

Others FCS commands such differential flaperons, aileron movement as well as rudder toe in (to improve longitudinal stability) on the Hornet however is. Wing warping I'm fairly sure isn't. As for Frequency and dampening, they usually require very small but quick response of flight controls. I'm not sure if this is modelled in DCS but in all honesty its not something I would expect. After all how many pilots are looking at their flight controls when flying? I certainly never have unless I have a fault with them.

[Razor18]

I know it's a kind of old topic, but I was wondering if bank limiter (NAV and TAC) works today as it supposed to work, or is it still not fully implemented?

Flown a lot recently, I definitely never saw bank angles anywhere close to 60 degrees with tactical bank selected.

[BIGNEWY]

Hi, 

bank limits were adjusted some time ago, seems this thread was not marked at the time. 

If you think there is an issue and have public evidence to support it please make a new thread. 

thank you