Flyinglion2000 Posted February 23, 2014 Posted February 23, 2014 I was reading through Mark Kyle's build log on this site and came across the subject of weight & balance and the adjustments he put his aircraft through to adjust his aircraft's W&B to where he worked out it needed to be for optimum trim and performance. So I dug out my W&B and plotted it as per the manual and got an initial surprise - my W&B was well forward of the forward most CoG line provided by ICP in the manual. For reference the graph I initially used is found in CAP12. FIRST FLIGHT pages 1-2/4 dated 12th January 2010. Here is my data and graphic overlaid on the ICP W&B chart. My Sav S is the blue line. This was done using lb metres. Then I tried it using the W&B chart Mark Kyle was using for his aircraft. This chart is in kg metres. Lo and behold I was well within the forward and rearward limits of CoG. But this was for a Savannah XL VG?!?!?!? Getting very confused now So I went back to the manual and in the Pilot Operating Handbook (not the Construction Manual) I found another set of W&B charts - one in Kg metres and the other in lb feet. I immediately noticed that the kg metres W&B chart has the same CoG limits as for the Sav XL VG! Shouldn’t they be different ?!?!?!? So I plotted again in lbs and ft and I got the same result smack in the middle of the forward and rearward limits of CoG just like as it was for the W&B chart in kg metres above. Not unexpected if ICP did the change from metric to imperial correctly but is this the right W&B chart for a Sav S??? So my questions are: 1. Which W&B charts are correct for a Savannah S? The one in the construction manual or the one in the pilot operating handbook (which seems to be the same as the one for Sav XL VG!) 2. I would have thought that the Sav S is a little different in construction to the Sav XL VG so would therefore have a different W&B charts for each aircraft. Yes/no? Savannah S weight & balance lb metres.pdf Savannah S weight & balance kg metres.pdf Savannah S weight & balance lb metres.pdf Savannah S weight & balance kg metres.pdf Savannah S weight & balance lb metres.pdfSavannah S weight & balance kg metres.pdf 1
Kyle Communications Posted February 23, 2014 Posted February 23, 2014 The S and XL are exactly the same aircraft except for the rounded rear corners of the fuselage the only other differences are the flap control connections and how they come out of the fuselage at the flaperons but the measurements of cabin length from the rear wing mounts to the spinner and the wings are the same and the tail lengths are the same so it would hold true that the XL and S weight and balance should be the same chart the moments and arms are the same. I looked at a S manual and checked this. Mine flew great when she first flew but the nose wheel would always touch the gound very early on landings and I could not hold it up that well. Also on final the elevator I always had to hold a fair bit of pressure on it and if I released it the aircrafts speed accelerated quite fast so this is why I decided to look into changing the balance. I did all the calculations for the weights on the wheels WITHOUT weighing the aircraft and doing all the calculations and arrived at the chart I posted. I readjusted the trim as per the manual where the manual says 30mm mine originally was like 10mm now it is more like 30mm. I use a RC Allen servo and led display my takeoff trim and level flight it 2 bars down from the top so I still have some forward trim available and with first stage of flap and full up trim I can let the stick go and the aircraft stays rock solid at 50 knots. It is perfect. Elevator is what some may call sensitive in level flight but what I did notice was before I always had to just keep trimming for level flight a little….now once set the trim attitude remains solid and I put this down to the aircraft previously being too nose heavy even though it was ok in the chart but it was toward the nose heavy line but well inside it. I will post the actual figures soon as I have to do a new weight and balance for the 600 kg mod and submit them with the paperwork I expect the figures to be pretty much what I calculated because it flys like them. Mark
Kyle Communications Posted February 23, 2014 Posted February 23, 2014 It doesn't matter on the construction techniques used it is all to do with moments and arms and the weights on those
Kyle Communications Posted February 23, 2014 Posted February 23, 2014 I also not on your chart at the higher weight end you line is not straight that is because you have 30kg in the baggage area it is only specced for 20kg at that arm measurement thats why it does the dive towards tail heavy
Kyle Communications Posted February 23, 2014 Posted February 23, 2014 Oh and I wished I weighed 80kg 1
Flyinglion2000 Posted February 24, 2014 Author Posted February 24, 2014 Thanks Mark I emailed Reg Brost and I think we worked out the first chart i used (in pounds metres ?!?) was flawed and tus not to be used. Yes that was very interesting to see how the baggage weight has a very dramatic effect on the CoG. Do you think the chart is specified for the extended bagage area that most of us seem to installing? I hope so. I enjoy (as do many others) reading your posts on your aircraft build and flying - great to see. Hope you get back in the air soon - good flying weather is coming! ps Its a battle to stay at 80kg! too much amber fluid in my diet me thinks
Kyle Communications Posted February 24, 2014 Posted February 24, 2014 The extended baggage area is still only specified for 20 or 22kg just allows more room for the lighterweight bulky stuff that's all like spleepings bags etc
Kyle Communications Posted February 24, 2014 Posted February 24, 2014 That chart you did I gather you made it up on the computer ?
Flyinglion2000 Posted February 25, 2014 Author Posted February 25, 2014 Yes it was done on excel and I used the forward and rearward limits of CoG from the W&B charts supplied by ICP in the manuals. Basically just plotting a few lines.
Kyle Communications Posted February 25, 2014 Posted February 25, 2014 did you use exel to do the formulas as well...if so can you send me the file please [email protected]
Flyinglion2000 Posted February 25, 2014 Author Posted February 25, 2014 Yes I did. And email sent. Have fun! Let me know if I screwed up some way
Hongie Posted February 25, 2014 Posted February 25, 2014 The S and XL are exactly the same aircraft except for the rounded rear corners of the fuselage the only other differences are the flap control connections and how they come out of the fuselage at the flaperons but the measurements of cabin length from the rear wing mounts to the spinner and the wings are the same and the tail lengths are the same so it would hold true that the XL and S weight and balance should be the same chart the moments and arms are the same. I looked at a S manual and checked this. Mine flew great when she first flew but the nose wheel would always touch the gound very early on landings and I could not hold it up that well. Also on final the elevator I always had to hold a fair bit of pressure on it and if I released it the aircrafts speed accelerated quite fast so this is why I decided to look into changing the balance.I did all the calculations for the weights on the wheels WITHOUT weighing the aircraft and doing all the calculations and arrived at the chart I posted. I readjusted the trim as per the manual where the manual says 30mm mine originally was like 10mm now it is more like 30mm. I use a RC Allen servo and led display my takeoff trim and level flight it 2 bars down from the top so I still have some forward trim available and with first stage of flap and full up trim I can let the stick go and the aircraft stays rock solid at 50 knots. It is perfect. Elevator is what some may call sensitive in level flight but what I did notice was before I always had to just keep trimming for level flight a little….now once set the trim attitude remains solid and I put this down to the aircraft previously being too nose heavy even though it was ok in the chart but it was toward the nose heavy line but well inside it. I will post the actual figures soon as I have to do a new weight and balance for the 600 kg mod and submit them with the paperwork I expect the figures to be pretty much what I calculated because it flys like them. Mark Interesting mark. The savannah S that I rent is like yours used to be. Full back trim, and one stage of flaps, and the stick is a long way back with quite considerable weight on it. Being a 24- rego though I dont see how it could be rectified.
Kyle Communications Posted February 25, 2014 Posted February 25, 2014 Interesting mark.The savannah S that I rent is like yours used to be. Full back trim, and one stage of flaps, and the stick is a long way back with quite considerable weight on it. Being a 24- rego though I dont see how it could be rectified. yes very nose heavy..exactly how mine was....now she is a thing of beauty to fly :)
rick morawski Posted February 25, 2014 Posted February 25, 2014 Oooherr could you send one to me too? [email protected] or maybe just post it up. Cheers Rick Yes I did. And email sent.Have fun! Let me know if I screwed up some way oot em rof ypoc a Yes I did. And email sent.Have fun! Let me know if I screwed up some way
Kyle Communications Posted February 25, 2014 Posted February 25, 2014 Your Xl file seems to work perfect although the fuel arm is only slightly out attached is the original with the battery in the front and the "new one done with initial weights but need to still do it properly it is with the calculations I did Savannah S weight & balance new KgMetres.pdf Savannah S weight & balance KgMetres.pdf Savannah S weight & balance new KgMetres.pdf Savannah S weight & balance KgMetres.pdf Savannah S weight & balance new KgMetres.pdfSavannah S weight & balance KgMetres.pdf
Kyle Communications Posted February 25, 2014 Posted February 25, 2014 another thing that pretty much confirms these graphs is when first built my sav I could lift the nose right up and the tail would never sit on the ground now I can lift the nose up and the aircraft sits on its tail with a little weight on it…this is confirmed in the "new" chart when you look at it
Flyinglion2000 Posted February 25, 2014 Author Posted February 25, 2014 Here is the file. So Mark your aircraft is relatively light to lift the nose by hand as compared to before? Savannah S weight & balance.xls Savannah S weight & balance.xls Savannah S weight & balance.xls
Kyle Communications Posted February 25, 2014 Posted February 25, 2014 Nosewheel weight went from 71.5kg down to 58 kg a huge difference
Flyinglion2000 Posted February 25, 2014 Author Posted February 25, 2014 Yes it will be interesting to see how your actual W&B checks out when youre done rebuilding and ready to fly again. I gather having teh aircraft's W&B just right of centre of the two CoG limit lines is an optimum configuration. The fuel arm I used is 0.495M - it shows up in the table as 0.50M - is that right?
Kyle Communications Posted February 25, 2014 Posted February 25, 2014 yes the exel file is truncating the 2 decimal digits.....my D1 and D2 are a bit different...I don't know why. I have fitted the new main undercarriage and have to turn my nose fork back around I will do a remeasure for this and see what it ends up....I am not sure why mine are so different originally
Flyinglion2000 Posted February 25, 2014 Author Posted February 25, 2014 Yes I have only used the distance values of the landing gear from the manual. My actual distances are aprrox 20mm smaller. I will dig them out and adjust. Your main gear distance arm seems comparatively small. Mine is 654mm, the manual says 675mm. My reference point is the leading edge.
Kyle Communications Posted February 25, 2014 Posted February 25, 2014 yes I don't know why mine is 617mm I measured all the distances like 10 times to be sure because mine are a bit different to the manual but from what I have seen everyones distances all seem to be different , don't know why either, ...you need to do it with your distances....I note your nosewheel weight is 75kg I thought mine was heavy at 71.5 Probably on Friday I will get a chance to remeasure it all but cant get the weights done yet..... also when you do the weights I hope you blocked up the main wheels so a spirit level on the top of the rear deck showed it was level because if you don't you will get false weight values on your scales
Kyle Communications Posted April 10, 2014 Posted April 10, 2014 Ok did a new W&B on my rebuilt Sav here are all the actual weights and chart. Pretty much exactly as I had calculated when I shifted the battery Kyle Savannah weight & balance-2.xls Kyle Savannah actual weights.xls Kyle Savannah weight & balance-2.xls Kyle Savannah actual weights.xls Kyle Savannah weight & balance-2.xlsKyle Savannah actual weights.xls
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