Just when I thought I understood the payload model ...

[CowlFlapsOpen]

Hi all. I am growing very frustrated. I thought I understood the payload model based on a lengthy exchange in this forum that Dan and I had, but
read on...

I am trying to create a payload model for the DreamFleet Baron 58. This is a light GA aircraft so special consideration must be paid. It is
important to me that the flight dynamics be just as the maker intended (I bought it for its accurate flight handing) and that I model the presence of
a pilot and co-pilot of known weight who are not included in the passenger list. Based on my exchange with Dan, I understood that I needed to check
the "Disable position calculation" option so that FSP takes the empty CG/reference datum information directly from the aircraft.cfg (not an arbitrary
calculation done by FsP) and use the actual station information from the aircraft.cfg.

So, the default aircraft.cfg weight and balance for this aircraft appears below. I used this information to create a payload for this model by:

1. Defining the pilot and co-pilot as "Frd baggage" but located their station at the ARM for station_load.0/1 (-6.54, -0.3) and limited it to 400lbs
(200 X 2 souls).
2. Defined 2 passengers at Station 1 using the info for station_load.2/3 (-9.79, -0.3),
3. Defined 2 further passengers at Station 2 using the info for station_load.4/5 (-12.66, -0.3), and
4. Defined a "Rear Baggage" at the specified station_load.7 (-15.0, -0.5) with a max of 200lbs.

Trouble is, when you load this in FsP (400lbs for pilot/co-pilot), 191lb passenger in First row, 165lb passenger in 2nd row, 101lbs fuel, 200lbs
baggage) you get a center of gravity way aft and outside the range (plane tips on its tail sometimes on start). YET, if you load exactly the same
configuration in the defaul MS Payload and Fuel, the CG indicator shows a near centered CG.

What gives? What am I doing wrong? Can someone please explain how to make this model so that a known pilot and co-pilot are considered and the CG
obtained is that intended by DreamFleet for the specified load?

Can't wait for Dan to fix this in the next version (as he said he was going to).

[weight_and_balance]
max_gross_weight = 5524 //MTOW 5500 lbs
empty_weight = 3983
empty_weight_pitch_MOI = 5637
empty_weight_roll_MOI = 8874
empty_weight_yaw_MOI = 11076
empty_weight_coupled_MOI= 0.0

reference_datum_position =6.96, 0, 0 //6.96, 0, 0 83.1 in 6.925 ft
empty_weight_CG_position =-6.16, 0, 0 // max fwd 74 in 6.16 ft

max_number_of_stations = 8

station_load.0 = 0, -6.54, -0.9, -0.3, Pilot
station_load.1 = 0, -6.54, 0.9, -0.3, Co-Pilot
station_load.2 = 0, -9.79, -0.9, -0.3, Passenger 1
station_load.3 = 0, -9.79, 0.9, -0.3, Passenger 2
station_load.4 = 0, -12.66, -0.9, -0.3, Passenger 3
station_load.5 = 0, -12.66, 0.9, -0.3, Passenger 4
station_load.6 = 0, -1.25, 0.0, 0.0, Fwd. Baggage
station_load.7 = 0, -15.00, 0.0, -0.5, Rear Baggage

[DanSteph]

CowlFlapsOpen wrote:
station_load.0 = 0, -6.54, -0.9, -0.3, Pilot
station_load.1 = 0, -6.54, 0.9, -0.3, Co-Pilot
station_load.2 = 0, -9.79, -0.9, -0.3, Passenger 1
station_load.3 = 0, -9.79, 0.9, -0.3, Passenger 2
station_load.4 = 0, -12.66, -0.9, -0.3, Passenger 3
station_load.5 = 0, -12.66, 0.9, -0.3, Passenger 4
station_load.6 = 0, -1.25, 0.0, 0.0, Fwd. Baggage
station_load.7 = 0, -15.00, 0.0, -0.5, Rear Baggage

Is this the original aircraft.cfg ? I see no weight here... try to put the weight and see the result...
all station are behind the zero CG it seem your problem is normal what I find strange is that loading
it by FS give a right CG... how do you load it ?

also there will be no "fix" for your problem, only things is that you'll be able to define "pilot" station
and also give a lateral position this would not change anything to your problem here...

Dan

[CowlFlapsOpen]

Hi Dan. Thanks. Yes, that is the original. There are no weights for particular stations because that is the default (i.e. I haven't loaded pilot,
passenger, etc. in FS). What I did was define stations in a payload model as described above and then load the plane in FsP. Because there is a
pilot station in the model (using the forward baggage slot set to the station settings specified in the aircraft.cfg for the pilot/copilot) I could
specify a 200lb pilot, 200lb copilot, and 200lbs baggage. FsP then loaded a 191lb passenger in First row, 165lb passenger in 2nd row, and I added 101
lbs of fuel. The result was way out of balance.

So...I aborted the flight. Went to the MF Fuel and payload dialogue and added a 200lb pilot, 200lb copilot, 101 lbs fuel, 200 lb baggage in the rear,
and 191 and 165 lb passengers in the second and third rows respective. In other words, I replicated the loading the FsP has prescribed. MSFS showed
an excellent CG. Here is what it would have looked like had I saved it.

station_load.0 = 200, -6.54, -0.9, -0.3, Pilot
station_load.1 = 200, -6.54, 0.9, -0.3, Co-Pilot
station_load.2 = 191, -9.79, -0.9, -0.3, Passenger 1
station_load.3 = 0, -9.79, 0.9, -0.3, Passenger 2
station_load.4 = 165, -12.66, -0.9, -0.3, Passenger 3
station_load.5 = 0, -12.66, 0.9, -0.3, Passenger 4
station_load.6 = 0, -1.25, 0.0, 0.0, Fwd. Baggage
station_load.7 = 200, -15.00, 0.0, -0.5, Rear Baggage

By the way, what is the figure generated when you press Estimate? I know it is the sum of the product of the nbr passengers times 200 times the
longitdinal ARM plus 200 times the baggage ARM. But what does this mean? How does FsP relate this to the CG datum in the aircraft.cfg and how does
it know the tolerances? How does MSFS compute CG when one uses the Fuel and Payload dialogue. Just curious.

Thanks as always for a great product. I do hope you consider us light GA folks in the next revision by adding the pilot/FO and FA explicitly.

[jboweruk]

You do know somebody has done a payload model don't you? Why not try editing that to add your pilot/co-pilot.

[CowlFlapsOpen]

Thanks, yes, i knew about that. But the values in that payload model do not correspond to the aircraft.cfg. They are just arbitrary values. i would
like the stations located where the designer defined them so the plane handles as designed and as it would if loaded within MSFS itself. Maybe this
isn't possible afterall.

[DanSteph]

sure it is with the "disable calculation" you must define FSP station as in the aircraft.cfg and you get the same...
given that you have the last FSP version of course....

Dan

[CowlFlapsOpen]

I've been thinking a bit more about this an staring at the numbers above. I have no idea if this is correct but I'm beginning to think that I
constructed the ARMs incorrectly. Specifically, the reference datum is said to be at 6.96 forward. If the ARMs are in reference to this point and
not zero, then all the stations in FsP should be adjusted viz 6.96. Station 1 where the pilot is, for example is -6.54. Subtracted from 6.96 this
is .8 forward (not 6.54 feet aft). I'm not at home to try it out, but I think i should re-define the stations about the reference datum not about
zero. this will shift all the stations considerably forward and should remove the rearward CG I am finding, provided FsP uses the reference datum as
the start point for determining the CG when the "Disable position calculation" option is checked. it would be helpful of Dan could say just what
information FsP uses to determine CG when it is calculated directly from the aircraft.cfg.

[CowlFlapsOpen]

Looks like my last post is correct! The reason I missed it the first time is that I built a payload model of the same type for the Aeroworx B200 and
the reference datum for that one is defined as 0, 0, 0. Thus that model was correct (as my testing verified) using the figures directly from the
station ARMs specified. BUT the reference datum for the DreamFleet Baron 58 (and for DreamFleet's A36 Bonanza by the way) is a positive/forward
value (see above). Thus the ARMs in the aircraft.cfg are in relative to the reference datum. When you make this adjustment the CG is spot on center
before passengers and crew are loaded.

I know that probably this all seems esoteric to many folks, but I figured I'd post it in case there were others like me who really go for faithful
reproductions of the seating in light aircraft.

Thanks too to Dan for his patience. Hopefully I'm done with this. I've certainly become an "accidental expert" on the weight and balance sections of
aircraft.cfgs! Not exactly a lucrative skill I guess.

[pagir]

Happy you find the solution. And yes, it will helps others!

Pagir