Weight & Balance question.

[facthunter]

Just something to bear in mind. Make sure you have the Cof G or the various loads in the correct place with the pitch horizontal.  You look to be tending to tail heavy. How much can you fit in the Baggage area and how far back does it go.? Nev

[Moneybox]

The Datum is the leading edge of the wing. The fuel tank arm is 920mm and the baggage is 1270mm (in line with the wing trailing edge) and is just big enough for that pair of electric scooters that we're going to need to make it from the airport into town 🤣

 

The fuel tank is wedged in between the seats and the luggage space.

[440032]

1 hour ago, Moneybox said:

I'm grounded for now so I've been doing a bit of study but I got stuck on Weight and Balance because I find some of the references quite confusing. Anyway to get it clear in my mind I entered the data into Excel because at least I understand what I'm looking at.

 

Weight and Balance 24-4149.xlsx 11.79 kB · 5 downloads

 

Can one of you smart cookies, of which there a few, please confirm that my calculations look correct.

My plane has an empty weight of 309.8kg at 233.21mm aft of Datum.

I have one 65L tank and the crew weight 119kg.

 

It looks like there's room to expand on the fuel or luggage if I get the balance right?

I see some odd things.

74kg/L fuel. I think there is much lighter fuel available.

"Empty plane" ARM is what?

What is the datum point for this plane?

I would have been expecting to see an ARM measurement from datum to nosewheel, and a weight, and an ARM measurement from datum to main wheels, and a weight.

 

[facthunter]

You ARE getting towards the REAR of the permitted range.  It's NOT the best place to be. Nev

Edited February 9 by facthunter

[Moneybox]

15 minutes ago, 440032 said:

I see some odd things.

74kg/L fuel. I think there is much lighter fuel available.

"Empty plane" ARM is what?

What is the datum point for this plane?

I would have been expecting to see an ARM measurement from datum to nosewheel, and a weight, and an ARM measurement from datum to main wheels, and a weight.

 

 

HaHa, yes a typo. Grams if you like or 0.74kg.

 

As stated the datum is the leading edge of the wing. I've entered ARM measurements from that point rearward. The positioning of the wheels is only relevant when calculating the CG of the empty plane. I don't think it has anything to do with my loading of Crew, Fuel and Baggage.

 

Edited February 9 by Moneybox

[facthunter]

It would be better to have the datum say 500 mm forward of the spinner. At some time you might alter weights forward of the Wing LE and you avoid dealing with negative figures. Nev

[Moneybox]

1 minute ago, facthunter said:

It would be better to have the datum say 500 mm forward of the spinner. At some time you might alter weights forward of the Wing LE and you avoid dealing with negative figures. Nev

I might have to have a little rail running forward with a weight adjusted to suit the occasion.

 

 

I've got some of this lying around somewhere.

[facthunter]

It doesn't have to be a real place. You clearly designate it and base your figures on it. I'm led to believe it's done all the time.   Nev

[Moneybox]

6 minutes ago, facthunter said:

It doesn't have to be a real place. You clearly designate it and base your figures on it. I'm led to believe it's done all the time.   Nev

 

From a calculation point of view the excel file makes it easy to enter a negative if needed and the Datum remains the same.

[Moneybox]

Anyway I've achieved my goal. I have some understanding of weight and balance and how to calculate it. Perhaps somebody might get some value out of modifying my excel file to suit their own.

[facthunter]

 OK but there's a good argument for doing it the accepted way, in my book. Is there anything you can move forward  to move the balance point.? Nev

[facthunter]

WE posted together. Anyhow I'll leave you with it.. Nev

[Moneybox]

3 minutes ago, facthunter said:

 OK but there's a good argument for doing it the accepted way, in my book. Is there anything you can move forward  to move the balance point.? Nev

 

The Sportstar has a reputation of a beautifully balanced plane to fly. Best not tampered with until the day I choose to pack a few more litres of fuel under the seat. At this point it has no modifications since new.

[djpacro]

1 hour ago, Moneybox said:

The Datum is the leading edge of the wing. The fuel tank arm is 920mm and the baggage is 1270mm (in line with the wing trailing edge) and is just big enough for that pair of electric scooters that we're going to need to make it from the airport into town 🤣

Which model of the Sportstar? The POH for the Sportstar Max that I grabbed from online is different. It has fuel arm of 26.75 in (679 mm) and baggage arm of 43.65 in (1083 mm) assuming my arithmetic is correct! Crew moment arm is also different from your spreadsheet - 545 vs 500 mm.

 

Suggestion: to check your spreadsheet use the example given in the POH. And ignore those who say use different datums etc, just follow the POH and the TCDS.

[Blueadventures]

41 minutes ago, djpacro said:

Which model of the Sportstar? The POH for the Sportstar Max that I grabbed from online is different. It has fuel arm of 26.75 in (679 mm) and baggage arm of 43.65 in (1083 mm) assuming my arithmetic is correct! Crew moment arm is also different from your spreadsheet - 545 vs 500 mm.

 

Suggestion: to check your spreadsheet use the example given in the POH. And ignore those who say use different datums etc, just follow the POH and the TCDS.

Also does the log and other paper work contain its original or a recent w&b; if not try RAA maybe to get a copy if they can provide it.  Some paperwork is only available to the first owner sometimes. 

[Moneybox]

18 minutes ago, djpacro said:

Which model of the Sportstar? The POH for the Sportstar Max that I grabbed from online is different. It has fuel arm of 26.75 in (679 mm) and baggage arm of 43.65 in (1083 mm) assuming my arithmetic is correct! Crew moment arm is also different from your spreadsheet - 545 vs 500 mm.

 

Suggestion: to check your spreadsheet use the example given in the POH. And ignore those who say use different datums etc, just follow the POH and the TCDS.

Thank you. Mine is an early model, 2004 with a single tank in the fuselage. The later planes have wing tanks that alter the CG amongst other things. I have been confused by the documents sent by Evektor. I've had to request original documents for the plane as most have gone missing. I have documents dated the same with the correct rego number and serial number but some are in metric and some imperial.

 

Unfortunately I paid to have the Aircraft Operating Instructions printed and wire bound in A5 but the data is incorrect. I'll have to go again. Those instructions are dated 2006, with dual wing tanks and incorrect W&B for my model.

 

Reviving an old plane comes with its challenges.

[BurnieM]

Is that fuel capacity right ?

I thought all models (Sportstar, SS Plus, SS Max) of Sportstar had 115 litres.

 

Sorry, not keeping up; early model (2004) with single tank

 

Edited February 9 by BurnieM

[djpacro]

33 minutes ago, Moneybox said:

Thank you. Mine is an early model, 2004 with a single tank in the fuselage. ..... Reviving an old plane comes with its challenges.

I've been through that. I found an appropriate POH and Maintenance Manual - the latter has the moment arms same as you stated. Your spreadsheet seems fine to me.

 

My wife and I total about 150 kg and she would want to take more luggage than the 15 kg max of the Sportstar. Lucky, we have a different type.

 

Quote

It looks like there's room to expand on the fuel or luggage if I get the balance right?

Max baggage is 15 kg and max fuel is 65 litres regardless of balance.

[Moneybox]

18 minutes ago, djpacro said:

I've been through that. I found an appropriate POH and Maintenance Manual - the latter has the moment arms same as you stated. Your spreadsheet seems fine to me.

 

My wife and I total about 150 kg and she would want to take more luggage than the 15 kg max of the Sportstar. Lucky, we have a different type.

 

Max baggage is 15 kg and max fuel is 65 litres regardless of balance.

 

Yes I have a wife too so not the plane I'd have chosen 😀

 

I didn't actually buy it, I acquired it through a family member who purchased it new (demo model) but never learned to fly. Beggars can't be choosers. I need to cover longer distances and carry more load but as I say it was not a planned purchase.

 

[rgmwa]

15 minutes ago, Moneybox said:

I didn't actually buy it, I acquired it through a family member who purchased it new (demo model) but never learned to fly. Beggars can't be choosers. I need to cover longer distances and carry more load but as I say it was not a planned purchase.

Sounds like a bargain. What would you have bought?

[Moneybox]

4 hours ago, rgmwa said:

Sounds like a bargain. What would you have bought?

 

Most likely the same in a later model just for the bigger tanks giving it it a longer range. I train in an Evektor Harmony so I feel comfortable there.

[Flightrite]

This subject can be over thought in some ways. Simple solution is work out the worst case rearward CoG and Fwd CoG with these  numbers/weights handy and use them as a limit, anything less weight wise is obviously ok👍

[440032]

17 hours ago, Moneybox said:

 

HaHa, yes a typo. Grams if you like or 0.74kg.

 

As stated the datum is the leading edge of the wing. I've entered ARM measurements from that point rearward. The positioning of the wheels is only relevant when calculating the CG of the empty plane. I don't think it has anything to do with my loading of Crew, Fuel and Baggage.

 

That excel chart you sent makes no sense to me. (the "empty plane" bit) I've done a similar chart for my own plane and seen many others, I understand what you are aiming to end up with, a good usable chart.

I think it is now time for you to seek help from a professional WCO _ Weight Control Officer - an industry person accredited by CASA to do this stuff.

Loading is not a thing to guessing or relying on advice from experts on some forum on the internet. Some will be correct, some will not.

 

[Moneybox]

4 hours ago, 440032 said:

That excel chart you sent makes no sense to me. (the "empty plane" bit) I've done a similar chart for my own plane and seen many others, I understand what you are aiming to end up with, a good usable chart.

I think it is now time for you to seek help from a professional WCO _ Weight Control Officer - an industry person accredited by CASA to do this stuff.

Loading is not a thing to guessing or relying on advice from experts on some forum on the internet. Some will be correct, some will not.

 

 

It might look confusing as the results don't end up as a reference on a chart. They didn't supply a chart in this operators manual but use a % of Mean Aerodynamic Chord (MAC) as the load limits. I've got my head around it now and I'm happy with the results however I'm sure my trainer will set me straight when I get back there.

[skippydiesel]

My apologies in advance if this solution has already been suggested; OzRunways has a nifty weight and balance calculator, that can be configured/personalised for your aircraft. Once configured, you only have to put in the variables (fuel quantity/weights in location) and it tells you if your aircraft is within/out - simples!😈