W & B datum for Skydemon

[NigelW]

I have a SPL 450 and I am trying to set up the W&B datum on Skydemon. Does anyone have the 5 datum points to hand as I can't seem to get it right. Thanks in anticipation.

[MikeL]

Hi Nigel
Like you, I have tried many times to get the correct figures to produce an acceptable polygon, and hope that I have now cracked it.
SkyDemon is a brilliant piece of kit, but the weight & balance instructions are pretty opaque -the figures they give are not backed up by an explanation.
First, these are my SPL's Weight & Balance figures: Empty weight 260 kg @ CG 1586

With trial & error I have found the following will produce a polygon:

Going around the polygon (clockwise starting from the X/Y axis junction) in order:

1 1601.0, 260.0, ( 1601= CG minimum limit. The 260 = my empty weight)

2. 1601.0, 315 ( Most Fwd CG calculated with 55 kg pilot & no fuel-315 kg)

3. 1650.0, 450.0, ( Most Rearward CG calculated with 2 x 86 kg crew & no fuel. Max Weight allowed )

4. 1695.0, 450.0 (Most Rearward CG limit) & Max Weight Allowed)

5. 1695.0, 260.0 (Most Rearward CG & my SPL's empty weight)

If your set-up figures under “Aircraft” use the Pilot position 1688, Fuel/baggage position 2215 & you put your own weight in as pilot default weight & zero default for the other items, the graph populates itself waiting for you to add the relevant passenger/fuel/ baggage (if you are lucky) weights.
You must, of course, enter your A/C empty weight & CG in the top panels initially.

I found that you need to keep switching SkyDemon off/on every time you enter different polygon figures & also that the “flying weight” figure which comes up on the graph deducts the figure you have entered initially for taxiing, which is confusing at first, but actually very helpful.

I don't claim that these figures are “cast iron” because I am no expert in this matter, but they seem to work graphically & I hope they might stimulate further testing/verification by others who have been confused by SkyDemon's instructions.

Perhaps you can let us know how you get on?

Mike L.









Pc 1601.00,260.0, 1601.00,315.0, 1650.00,450.0, 1695.00,450.0, 1695.00,260.0

[NigelW]

Hi Mike, Thank you so much for the reply. I had almost given up hope after many failed attempts. I'll give them a go and report back. I do wish I was a 55kg pilot but I am a renowned salad dodger! Let's see what happens when my 'fatboy' figures are in the mix. thanks again Mike

[NigelW]

Well Mike, After months of meaning to get round to it I finally entered the figures. I have not flown yet but entered a route and simulated the flight. I did not get the usual warnings so on the face of it all seems well. I'll keep you posted on results.

[MikeL]

Hi Nigel
Very pleasing to see that it might work for your setup.
I would imagine that if it is OK in simulation mode then a flight test checked against actual loading figures should verify it.
Fingers crossed for further positive results soon.
Mike L.