CG missing from “loadsheet”

SimBrief Feature Requests
1

I can’t fathom why Simbrief provides a “loadsheet” that is missing basic CG information, and in particular the Zero Fuel Weight CG (ZFWCG or MACZFW) that is essential for Airbus aircraft. We get a takeoff and landing calculator which is a nice to have, but CG information is more important.

It is painfully difficult to obtain this information elsewhere, basically requiring me to manually re-input all of the passenger and cargo data and distribution data when Simbrief already has all the necessary data. It also requires me to use TopCat to do this, an aging product which is barely supported at this point.

Please, please, please, now that you takeoff and landing calculators, consider going back and providing a real loadsheet. One that I can actually use.

2

No, it does not. Which is exactly why it doesn’t provide the CG. I think a FAQ entry is needed about this.

Regards,

Tim

3

What is it missing? It has passengers, baggage and cargo. Everything else is via an aircraft profile.

If Simbrief wants to be a complete flight planning solution, it needs to provide CG. Saying it doesn’t have all the information, and yet can predict things like takeoff distance and trip fuel burn is a bit disingenuous, no? A CG calculation needs very little aircraft data to calculate.

4

Where are the seats located in the aircraft? Does it have first and business class seats or not? If the aircraft is not full, where are the passengers seated?

You even said yourself you have to enter distribution data in TopCat; where would SimBrief get said distribution data? Out of a hat or perhaps a crystal ball?

Regards,

Tim

1 Like
5

The seat configuration is static. It doesn’t change every flight, so have it configurable via an aircraft profile. Then it can be set to match a specific add-on, such as the Pro-Sim A320 or JeeHell FMGS A320.

Foreflight and NavBlue can calculate CG and so can TopCat. Please don’t imply this is somehow impossible. With a little imagination, a workable solution isn’t that hard to envision.

Generally, each area of the aircraft (e.g., business class) is assumed to be loaded evenly, so just need to know the mean location, or “station” for each area. These could be handled with 7 such stations: crew, first/business class, forward cabin, mid cabin, aft cabin, forward cargo and aft cargo.

6

The Weight/Balance Manual for any large transport category aircraft is around 150+ pages or more of formulae, showing arms and moments, real painful reading. The airline’s engineers (or their contractor) will then take that WBM and based on their layout of pax accomodations, seats, cabin dividers etc (the LOPA) write their Wt/Bal program based on how they have their cabin laid out, then apply curtailments to account for how the CG travels in flight; how the the CG travels as the gear are retracted, how CG travels as the flaps are retracted, to account for nonstandard weight distributions. The same airplane model (say A320-200) could have an unlimited number of cabin configurations at an airline, all with different arms and moments, and acceptable arms and moments based on the AFM.

The Weight and Balance manual and the AFM are all proprietary as well and are usually written for an individual aircraft serial number (depending on complexity).

ForeFlight doesn’t know my LOPA; when it can do a 777 I’ll be impressed; it can do basic performance for simple airplanes but that is about it. That is why there are Engineers with Aeronautical Engineering degrees and attendance at a Major Airframe Manufacturer’s Performance Class writing these weight/balance programs; or the airline hires a contractor. Boeing’s W/B class is three days of basics, then an additional two days for Freighter W/B.

Simbrief isn’t for real world navigation and what you are asking for is very close to that. It does what it does well for the Flight Sim user; it could make up a number and you wouldn’t know the difference. When MSFS can model how CG travels in flight, the empty CG as the aircraft sits on the ground empty, and account for my LOPA, then the thin line between reality and sim has truly been blurred.

NavBlue’s N-Flight-Planning does not do C.G. calculations as a part of the operational flight plan, no flight planning system does for that matter as the data files used in the manufacturer’s performance tools (Boeing Perf Engr Tools, Boeing Perf Software, Airbus Perf Engr Programs) do not include a CG location as an argument for creating the performance profile to load into a flight planning system. The assumption is that the CG is a mid-range CG within the aircraft’s certification envelope.

2 Likes
7

Your response is so full of exaggerated claim, disinformation, and twisted logic it’s hard to know exactly where to start, so I’ll try to just keep this reply at a high-level and not get too lost in the weeds here.

I’ll begin with what is the biggest issue up front. You don’t seem to believe that C.G. calculations are important, because you believe that CG isn’t modeled in any simulated aircraft. That is patently false, as some of the more sophisticated aircraft at least (e.g., Pro-Sim) do model the effect of C.G. I’m sure there are many others (e.g., JeeHell FMGS, FSLabs, etc.). Maybe the default C172 in the Xbox game doesn’t, I don’t know.

Secondly, you take a rather narrowly restricted view of the flight planning process, as you state that weight and balance is not part of the “Operational Flight Plan”. While that is certainly true, the OFP is not the sum total of the pre-flight preparation. Weight and balance is critical to any pilot that expects to have a long life. Just because it’s not part of the OFP doesn’t mean it isn’t important.

Your claims that Firelight and NavBlue don’t offer weight and balance is laughable. Clearly you haven’t used them, never seen them, and have no idea what they are. Forelight is a complete solution. It literally has a tab on the main user interface for “weight and balance”. Here’s a link for you (ForeFlight - Weight & Balance for Flight Planning). If only it offered the necessary export format for flight simulation use I would ditch the limited functionality of Simbrief in a heartbeat, but this isn’t their market. I’d imagine they don’t want to deal with support requests from people that don’t understand what weight and balance is.

Finally, you act like weight and balance is rocket science. It isn’t. Did you ever play on a “seesaw” or “teeter-totter” as a child. It’s weight times moment arm, as every child instinctively learns on the school playground. You divide the total moment by the total weight and you have the C.G. There is nothing that I had to learn in my education as an aerospace engineer from MIT to learn how to find the center of mass of an object, because it was basic high school physics.

If the only objective of Simbrief is to produce an OFP as you seem to keep falling back on, that is fine. It’s none of my business what product you produce. If Simbrief only wants to be a navigation planner and not a full one-stop-shop for flight planning, that’s your choice. I recommended a feature that could make your product more of a complete solution for pre-flight planning. As it is, Simbrief is not that. It sounds like it never will be, and I will have to find another product that does what I need. They exist. It’s a shame, because what Simbrief does, it does fairly well. But the fact that the developers don’t even understand what C.G. is all about make me wonder what shortcuts have been taken elsewhere that I don’t know about, due to limited understand or interest.

9

Ok that’s probably enough for now. I’ll be closing this topic.

Your request has been noted. It might get added at some point in the future, but it isn’t currently on the road map.

Multiple highly respected and experienced users have already given some insight into the challenges associated with this. It’s not that it’s hard to add, it’s that it’s really time consuming to collect the data for all 160+ aircraft types and variants that SimBrief supports. And actually importing SimBrief’s load calculations into the various third-party add-ons would require additional coordination from both sides, which would take even more time.

As an aside, it sounds like it’s quite difficult to obtain CG information from your add-on of choice. If so, you might want to submit this feedback to the developer as well. They might be able to make this information more readily available for you, there’s no reason why they can’t distribute the load automatically and just provide you with the final CG value, for example.

Best regards,

Edited for brevity, no need for me to repeat what the others have already said.