Dan or others: A step-by-step weight and balance tutorial please?

[CowlFlapsOpen]

Hi all. I am spending so much time dealing with the payload model I am not getting to enjoy this wonderful add on. The supplied tutorial is
preoccupied with how to make an image but gives next to no information on how make a payload model from the aircraft.cfg so that aircraft's flight
dynamics remain faithful and accurate to the designers limits. I couldn't even find a definition of the Z and Y values anywhere. This frustration
has been expressed here by others too.

Could someone with certified expertise use the information below for the DreamFleet Baron 58 RXP to walk me through specifying the station parameters
in FsP? I want to know exactly how to do it so I can generalize the procedures to my other aircraft. I am aware that a payload model exists for this
model in Downloads but I have examined it closely and it doesn't look correct or square with the information in aircraft.cfg as far as I can tell.

Here is what I would like please:

1. I am aware from the other posts here that FsP doesn't address the weight and balance of pilots and crew and that a work around it required to have
accurate flight dynamnics. The Baron has no flight attendent, but I want to consider a permenent pilot and co-pilot of 200 lbs each. Thus the first
task is to alter the empty_weight and empty_weight_CG_position to reflect having the two pilots on board using the information on the pilot and
co-pilot stations that DreamFleet provided in the aircraft.cfg.

2. I'd like to add two banks of two seats each (see aircraft.cfg below) in their proper longitudinal, lateral, and vertical positions, as specified in
the aircraft.cfg. Since the seats are paired, their lateral positions will cancel to 0.0, which is what I see most payload models do anyway.

3. Finally I'd like the forward and rear cargo holds in their proper positions.

Please don't just tell me what the result should be. I think many people would benefit from seeing how, precisely, to take aircraft.cfg information
and generate a payload model so that the flight dynamics remain accurate. Of course, I know how to use the payload manager, make an image, etc., it
is only how to determine that Z and Y values for FsP and how to re-calibrate the empty CG in the aircraft.cfg to account for pilots on board that I need.

Thanks in advance -- jeff

============================

From POH: Maximum Gross Weight 5524 lb 2'509 kg; Seating Up to 6; Useful Load 1,517 lb 688 kg

From aircraft.cfg:

[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

[g48dd]

Hi CowlFlapsOpen, I am hoping that you get a response on this cause I am watching this thread so I can also learn.

[CowlFlapsOpen]

Let me try this another way since no one answered yet. Dan, could you please explain:

Below is the Weight and Balance section from the default C182. The FsP payload model that you supplied for this aircraft has two stations: Station 4
has 3 passengers with Pos Z = -1.0 and Pos Y = 0.0 and "Front Cargo" is given as 300 lbs,Pos Z = -5.0, and Pos Y = 0.0. How were these values
derived? Pos Y is always 0 because the two lateral seats cancel each other (1.5 and -1.5). But the Pos Z? I noticed that the empty CG is -3.0 and
the aircraft.cfg says the baggage compartment is -8.0 feet from the reference datum. Thus, the baggage station is -5.0 further aft of the empty CG. Is
that how it works? But what about the passengers? I can find anything that would have predicted that the station would be -1.0 as it is.

What am I missing? I looked at several examples, and most don't make sense. An exception is the one supplied by the Aeroworx developer for the Beech
200. He seems to have taken his Pos Zs directly from his airplane.cfg. I just want to build an accurate payload model for a couple of aircraft.

====================================================================================
[WEIGHT_AND_BALANCE]
max_gross_weight = 3110 // (pounds)
empty_weight = 1810 // (pounds)

reference_datum_position = 3.6, 0, 0 // (feet) distance from FlightSim Reference position: (1/4 chord, centerline, waterline)
empty_weight_CG_position = -3.0, 0, 0 // (feet) longitudinal, lateral, vertical distance from specified datum

max_number_of_stations = 50

station_load.0 = "0, -3.0, -1.5, 0.0, Pilot" // Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)
station_load.1 = "0, -3.0, 1.5, 0.0, Front Passenger" // Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)
station_load.2 = "0, -6.2, -1.5, 0.0, Rear Passenger" // Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)
station_load.3 = "0, -6.2, 1.5, 0.0, Rear Passenger" // Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)
station_load.4 = "0, -8.0, 0.0, 0.0, Baggage" // Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)

;Moments of Inertia
empty_weight_pitch_MOI = 1400.0
empty_weight_roll_MOI = 1137.0
empty_weight_yaw_MOI = 2360.0
empty_weight_coupled_MOI= 0.0

[DanSteph]

I always intended to do that (the tutorial is not finished)
but one things retained me to do that: My bad english...

I don't know how to explain in clear word how it work. The principle
remain simple but is a litle tricky to explain and to explain things
clearly you need to have a good language. Otherwise you might end
with something that is confusing.

I'll try again to do that... perhaps with some images ?

Dan

[CowlFlapsOpen]

Cheers Ken. Take care there. Sent you an email with the commander 115tc aircraft.cfg. If I get a response here I will make a payload model for that
plane. So far has been bleak though.

[DanSteph]

CowlFlapsOpen wrote:
What am I missing? I looked at several examples, and most don't make sense. An exception is the one supplied by the Aeroworx
developer for the Beech
200.

A fast explaination let me know if it's clear. (perhaps I can post it in the tutorial ?)

What are the coordinate mean for in the payload editor ?

PosZ in the payload editor is the front-rear position of a payload point in feet.
PosY is the vertical position of a payload point in feet.
There is no lateral position as FsP was done first for airliner.

How work the coordinate system in the payload editor ? (IMPORTANT)

The value "zero CG" position don't exist in Fs2004, So FsPassengers when you call the
payload loader do several test with various weight on the empty aircraft to find the zero
position on the empty aircraft

Now the PosZ position in the payload editor is always RELATIVE to this ZERO CG position on the EMPTY aircraft.
in brief -5 will be 5 feet back to the calculated CG position on the empty aircraft and + 10 will be 10 feet in front
of the zero CG position. Notice a -5 feet here may NOT match a -5 in the aircraft.cfg (this is important
for the explaination below) This method was done to avoid many problem with aircraft and it seem to
work on the majority of the aircraft. (see "Why FsP by default need to calculate...")

Now some poorly designed aircraft (those that are unflyable without a payload because
the designer loaded first the payload and then tuned the flight dynamic with the aircraft loaded)
this method may fail. So you have a parameter in the payload editor "Disable position calculation"
if this parameters is checked the PosZ will now be ABSOLUTE, mean exactly the same than in
the aircraft.cfg without any recalculation. Such a payload model may work thus only for one model.

So what should I put as number in the payload editor ?

As long as you don't check the "Disable position calculation" in the payload editor
consider always that your coordinate are RELATIVE to the center CG. It's up to you
to find the overall lenght of your aircraft in feet and put the payload point at an estimation
of the position based on the CG((always about 1/3 of the wing) the zero being at that CG,
negative number back and positive in front (see image below) You should also take care
that your weight are equally set around the CG.This is important especially for big payload point as
"100 passengers economic" class, if you put them at -40 feet "back of the CG" and don't put anything
in front of course the CG will be completely wrong, so usually you should put 100 pax at -40 and 100 at +40

Now you can tune the point as they make look in real for example if there is a back cargo on a baron 58
of course it will move the CG back.. as in the real aircraft. If you have a first class in front with a low pax count
you can put for example: "35 first class at +40ft" "90 economic class at -15ft", fully loaded the aircraft will
be well balanced. (this is an example)

Now nothing replace trial & error to fine tune your model, as you don't need to exit Fs2004 to see the change in your payload
model the job is really simple: In Fs2004 call the payload dialog, see CG with full aircraft, if not good switch to payload editor,
make change, save, switch to Fs2004 call again the payload dialog... etc etc.

To resume: The zero position in feet is always at the CG position (about 1/3 wing) up to
you to guess the total lenght of your aircraft and place the point at the correct position.

Why FsP by default need to calculate the zero CG and place the point relative to it ?

Because each aircraft is different and may use different coordinate system.
In aircraft.cfg for the same type of aircraft (example 737) you can see some aircraft having the pilot
at +40 feet and on some other it may be at +10ft or even -20 ft depend where the model's center is.
Thus a "737" payload model would work only for one model and fail for all others.( mess completely the CG when loaded)
So by calculating the zero CG position and placing the payload station evenly relative to this point
(say 80 pax at -10ft and 80 pax at +10ft) you are assured that this payload model would work on
the majority of the aircrafts and don't mess the CG.


One image worth thousand words:

Fig A Show an aircraft designed by Mr "A" he make the model with the zero CG at 22ft
in the aircraft.cfg also you have the payload point of the pilot at 25ft and the passengers at 10ft




Fig B Show an aircraft designed by Mr "B" he make the model with the zero CG at 10ft
as you see a payload model with ABSOLUTE position as in aircraft.cfg can't work for
both "A" and "B" aircraft.




In NORMAL situation without checking the "disable calculation"
in payload editor both aircraft will have the zero position as in the image above.
Thus it's simple to make a payload model that work well for both aircraft
+3ft for pilots and -5ft for passengers and -12ft for luggage in this case
(just and example the lenght scale is not right here)

Hope this explain a bit ? Is this clear enough to post in the tutorial ?

Dan



Post Edited ( 11-07-05 05:50 )

[CowlFlapsOpen]

Thanks Dan! Haven't had a chance to digest all this but looking forward to it. I'll try to look it over for tomorrow.

[DanSteph]

CowlFlapsOpen wrote:
Thanks Dan! Haven't had a chance to digest all this but looking forward to it. I'll try to look it over for tomorrow.

That's what I was saying with my poor english... in my native language I would be able to
write half this text twice more clear...

If anyone whant to refine it a bit ?

Dan



Post Edited ( 11-07-05 08:10 )

[CowlFlapsOpen]

Hi Dan. here is a summary of what I learned that may help others. However, make sure I got it right! Thanks!

There are two ways to make a payload. The first is to take the empty CG and station positions directly from the aircraft.cfg and translate them to
the payload. This approach is appropriate if you intend to make a payload model for a specific aircraft (say DreemFleet's Baron 58) but it will be
incorrect if you try to use it for another aircraft in that category (say the default Baron). This approach is also required in specific cases when
the aircraft's designer has given an inaccurate empty CG--usually because he/she assumed that the aircraft had passengers when developing the flight
dynamics without passengers aboard.

The second approach allows FS Passengers to estimate the CG using some internal trial and error tests and you supply the position of the stations
relative to whatever CG FS Passengers arrives at. The advatage of this appoach is that it is purely conceptual: You do not need to know the specific
locations for your stations or you can add stations that don't exist in real life--you only need to have an idea of where you want them placed
relative to one another(and the CG that FS Passengers deduces). A second advantage is that this payload can be used as a template for other aircraft
in the same category (all payware and default 747s you have for example). The stations in this appraoch will not correspond to those specified by the
maker of a specific aircraft and therefore are less realistic, but they should work generally and FS Passengers will test whether they are out of
bounds for the aircraff in question. If you don't have a payload for your specific airplane and you have one of these "generic" payloads, FS
Passengers will load it automatically (provided the aircraft name matches at least a portion of the payload names as discussed elswhere in a FAQ).

The specific approach: After creating the image you wish to use and starting the payload editor, check the "Disable position calculation" in the
payload editor. Using the aircraft.cfg, determine the stations using the longitudinal, lateral, and vertical distance given for each station and the
baggage compartment. FS Passengers does not model lateral position, so you can ignore this. Below is the Weight and Balance section from the default
C182, as an example. To model the two seats behind the pilot and copilot (station_load.2 and station_load.3), for example, create a station with 2
passengers, Z Pos = -6.2 and Y Pos - 0.0. This will place this set of seats 6.2 feet aft of the aircraft's modeled CG (which interested folks is 3.0
feet aft of a reference point 3.6 feet forward of the 1/4 chord line of the wing--or just above the wing i.e., 3.6 minus 3.0). Create a baggage
compartment 2 further feet aft of this, at -8.0 and 0.0. The procedure for airliners is the same although obviously there will be large numbers of
passengers at each station, depending. More on pilot and crew later.

The generic approach. Ignore the aircraft.cfg and simply visualize where you want different seating. FS Passengers will locate those seats in those
relative posiions in any aircraft you select and will determine, specifically, WHERE in the aircraft (in absolute terms viz the airframe) those seats
are later, when it determines the CG for that specific aircraft. So, for example, you might specify that you want 2 seats 3 feet in front of the CG
and 2 seats 3 feet behind those (nice leg room). The position for the first set would be z = 3.0 and Y = 0.0 and the second set Z =0.0 and Y=0.0. Be
careful to balance seating roughly around the CG in an offsetting fashion because you can obviously build a seating arrangement that is so out of
whack that the aircraft can't fly. You do not need to worry about this with the Specific Approach above as the developer considered this when they
supplied the values in the aircraft.cfg

Pilot and crew. FS Passengers does not model pilot and co-pilot on board. In large airliners their weight and balance can probably be ignore safely.
With light or medium GA aircraft they are a consideration. There are two alternatives. The easy solution is to place a station for them using the
procedures above and define it as "no charge". FS Passenegers will choose a pilot and co-pilot from among your passengers at the gate. This has some
disadvantahes:

1. it is unrealistic to ask a passenger to fly the plane unless this is a self-service airline (!)
2. the weight of flight crew varies from flight to flight,
3. you won't get a co-pilot usually if there are fewer passengers waiting at the gate than you have spaces for,
4.The pilot's name is not the name of the company pilot, and
5. You lose a potential paying customer or two.

If you place this station as the last station in the payload manager (#4), FS Passengers will fill it first which helps with the no co-pilot or pilot
problem.

There is a work around if you use the Specific Approach: In the aircraft.cfg, adjust the empty_weight value to add 190-200 pounds each for a pilot
and co-pilot. Determine from the aircraft.cfg where their position is relative to the empty CG would be (usually slightly forward). One way to do
this is to use the payload manager in MSFS and watch the "target" on the airplane model as you load weights for a pilot and co-pilot. Estimate the
relative change on CG and adjust the CG value accordingly in the aircraft.cfg. This adjustment will remain even you don't fly with FS Passenegers, so
if you are not flying with FS Passengers be careful not to load a pilot and co-pilot in the MSFS payload manager or the aircraft will be very off
balance.



====================================================================================
[WEIGHT_AND_BALANCE]
max_gross_weight = 3110 // (pounds)
empty_weight = 1810 // (pounds)

reference_datum_position = 3.6, 0, 0 // (feet) distance from FlightSim Reference position: (1/4 chord, centerline, waterline)
empty_weight_CG_position = -3.0, 0, 0 // (feet) longitudinal, lateral, vertical distance from specified datum

max_number_of_stations = 50

station_load.0 = "0, -3.0, -1.5, 0.0, Pilot" // Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)
station_load.1 = "0, -3.0, 1.5, 0.0, Front Passenger" // Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)
station_load.2 = "0, -6.2, -1.5, 0.0, Rear Passenger" // Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)
station_load.3 = "0, -6.2, 1.5, 0.0, Rear Passenger" // Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)
station_load.4 = "0, -8.0, 0.0, 0.0, Baggage" // Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)

;Moments of Inertia
empty_weight_pitch_MOI = 1400.0
empty_weight_roll_MOI = 1137.0
empty_weight_yaw_MOI = 2360.0
empty_weight_coupled_MOI= 0.0

[DanSteph]

I replied in the "official thread" here:
http://www.fspassengers.com/forum/showth...p?tid=1349

Dan

[g48dd]

Thanks CowlFlaps, I will be looking for it. Also thank you Dan for attempting to clairfy this. I have to go through slow lol. I will have some
time in a few days to try it out but right now getting ready for another mission won't be back for a few days.