Hi, just a question - would Simbrief consider adding Auto and Custom weight distribution (Center of Gravity) options, perhaps in the airframe editor?
The airframe editor allows very detail customization of weights, but nothing about distribution or “balance”.
The reason I ask is, in MSFS, in the default 787-10, apparently if you import Weight and Balance from Simbrief (a new capability in Sim Update 13), the sim moves the weight around to “optimize”, but the results are very tail-heavy, full nose down trim settings (at the moment).
SimBrief has no real concept of weight distribution, balance, or center of gravity. From a flight planning perspective (fuel burn, time en route, etc) it makes little difference.
Because every aircraft type (and potentially every individual add-on) will have different stations and limits, it would be a huge job to collect all that data and keep it up to date in SimBrief. Even bigger when you consider that we’d need to keep it up to date as and when developers update their aircraft.
It’s a lot of work and the potential for SimBrief becoming out of date at times is pretty high.
For this reason, we’ve always preferred that SimBrief remain “balance agnostic”, and that the add-on developers take care of distributing the load in a reasonable way on their end. While I understand your point that the current MSFS weight and balance isn’t ideal, I think a much better solution would be for MSFS to fix it themselves, rather than relying on SimBrief for this.
Thank you very much for the detailed reply - I get what you are saying.
Using the MSFS default 787-10 as an example, the MSFS toolbar > Weight and Balance panel actually seems to do a good job of allowing a user to specify custom weight and balance and CG per airplane (First Class, Economy, forward cargo, etc). And the CG calculated there does appear in the FMC once you load in. No problem there.
Recently MSFS and Working Title added the ability to import Simbrief flight plans, winds, and Weight and Balance in to the FMC of the 787 and 747 - replacing whatever was in the native W&B panel. What appears to happen is, when you import weights from Simbrief, the FMC “optimizes” (redistributes) the gross weight to favor a tail heavy plane. WT says the rationale is that (apparently) CG moves forward as fuel is burned… The problem is, the result is extreme trim settings and a significantly different configuration. I realize that’s not a Simbrief issue - I was just curious if the Balance part of Weight and Balance was in the cards. I can see how it would be complicated to say the least.
So for now, the simple solution is to just not import weight from Simbrief, and instead I manually enter the weight calculated by Simbrief in to the MSFS toolbar W&B screen manually (allowing custom distribution) - this results in what you would expect for configuration. This works fine.
As a dispatcher, I couldn’t care less how the weight was distributed as long as I am within the balance limits. Yes I know an airplane will burn slightly different than OFP if it is nose or tail heavy, but manufacturer performance information loaded into RW Flight Planning Systems do not provide a fuel burn delta based on where the CG is located.
MD11 aircraft are different, if the tail fuel management system is inop at dispatch (TFM moves the fuel around to keep the CG at the optimum location while airborne), I’ll add a 2.7% overburn as the CG is now assumed to be at the forwardmost limit, but that fuel adjustment is in McD’s MEL/DDG and their FCOM Vol 4 (Performance info) and the AFM for when TFM is inop.
Other than that one situation, as long as you’re in balance, FPS systems assume a CG location within the curtailed boundary.
Thanks - the issue only arose while testing the new 787-10 (Sim Update 13) in MSFS, which added optional ability to import from Simbrief. Specifically there is an option allowing you to import the weight from simbrief (thankfully it is separate from importing the flight plan) … and when you do so, the FMC does some weird calculation and puts the CG as far back as possible and ending up that that you need full nose down trim no matter what you do. This seems not normal and results in strange take off and landing behaviour - but that’s being discussed in the sim forum.
So that just led to trying to figure out why, and after going too far down the rabbit hole, I realized the easy solution is to just not import weights from Simbrief, and instead use the weight specified by Simbrief, but enter and distribute it manually in the native MSFS > Weight and Balance panel. That works just fine, and now that I understand how simbrief calculates passengers and baggage (in the airframe specs) I get the configuration (trim) settings I expect.
Topcat do a very good calc of distribution of passengers/cargo and therefore MAC %, I know it is not supported anymore, but as the 737, A320 etc are not changing much these days with regards to weight stations, it still works very well for calculating required STAB Trim…I just punch the MAC % from Topcat in the FMC and the stab trim calc from the FMC (or QRH) works well
I agree it is a pity Simbrief won’t do this, it is a wonderful piece of sw, but a nuisance that we have to do this calc separately
Are you also distributing the passenger/cargo load in your simulator the same way as you have in TOPCAT? As far I know you would need to do this manually through the payload editor since TOPCAT doesn’t integrate with any add-ons, which means manually setting all the passenger counts in the different cabin zones to match, as well matching the cargo weights in each individual compartment.
If you aren’t matching the distribution between the 2 programs, your MAC CG and Stab setting is going to be completely inaccurate anyways. You might as well just enter a random value.
Even if SimBrief supported this, you’d still need to manually distribute the weight in the sim for the MAC CG to match, which is arguably much more work than just going into the EFB/FMS and getting the actual value from there based on the add-on’s automatic payload distribution.
I simply take the distribution of passengers provided by Topcat (4 pass stations and 2 cargo holds in the 737) and punch those numbers into the 737 via its supplied program (in my case the prosim IOS), takes about 20 seconds
A lot of aircraft in MSFS don’t even let you customize the zones right now, so users would be expecting SimBrief to automatically match the add-on’s distribution. In some cases, the weight is distributed randomly by the add-on and impossible to predict at the flight planning stage.
This is something we’ll keep in the back of our minds for the future, but for now it isn’t likely to come soon.
While that is true, the location of the CG does not impact the flight plan I create from a fuel burn perspective. Other than the MD11, and in that very limited case as that is what the MEL requires - the 2.7% overburn when tailfuel management is inop as the MD11 now assumes that the CG is at the very forward limit… I still don’t care where the CG is as long as it is within the curtailed envelope. I know that will adjust the trim, but it doesn’t impact the flight plan.
