Ed Cesnalis Posted January 12, 2014 Report Share Posted January 12, 2014 Judging from the CG thread in the 'Flight Instruction' forum there is an alarming amount of misconception about CTs and the CG envelope. Here are some thoughts on various points, in no particular order: Empty Weight Center of Gravity Range CTs have and empty CG that is forward of the CG envelope and therefore has no empty weight range, this does not apply to us. You can load a CT out of the CG envelope Many say you can't or 'you have to work at it' but the truth is you can. Our envelope is less than 5 1/2 inches fore to aft and any W&B's that I have seen can exceed the forward limit with full tanks, empty luggage and a minimum weight crew. I can exceed both the fore and aft CG limits using the spread sheet that Dick posted ( it does recognize that the luggage can be loaded at more than one arm) If both fore and aft can be exceeded then your CT can likely exceed the CG limit too. Full fuel challenges the forward limit Low fuel challenges the aft limit Aft limit means sensitivity on pitch control Forward limit means heavy resistance on pitch control Flying at or beyond either limit is more challenging with the aft limit approaching over sensitivity and the forward limit requiring additional pressure for less response. Link to comment Share on other sites More sharing options...
FastEddieB Posted January 12, 2014 Report Share Posted January 12, 2014 Everything a pilot needs to know, and a whole lot more, here: http://www.faa.gov/regulations_policies/handbooks_manuals/aircraft/media/faa-h-8083-1a.pdf It's marvelous that these resources are available free online and you can easily fit them all on a tablet. Link to comment Share on other sites More sharing options...
Tom Baker Posted January 12, 2014 Report Share Posted January 12, 2014 CT, just because an empty weight CG is outside a flight CG envelope doesn't mean that the empty weight CG range doesn't apply. Here is from the J3 Cub. C. G. Range (+10.6) to (+22.7) See NOTE 3 for restricted limits on certain Serial Nos. below 4502. Empty Weight C. G. Range If placard "Solo flying in rear seat only" is installed (See NOTE 2): (+8.5) to (+20.3) When empty weight C. G. falls within range given, computation of critical fore and aft C. G. positions is unnecessary. Range is not valid for non-standard arrangements. Notice that the forward empty weight CG is ahead of the forward flight CG. After looking again I see they call it empty weight CG limits on the W&B form from Flight Design. W&B.doc Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted January 12, 2014 Author Report Share Posted January 12, 2014 Tom, I see the empty weight limits from 9.45 to 13.78. Do range and limits have the same meaning? Back to Dick's SS it is within those empty limits and can be standardly loaded outside of the CG envelope. Link to comment Share on other sites More sharing options...
Tom Baker Posted January 12, 2014 Report Share Posted January 12, 2014 Tom, I see the empty weight limits from 9.45 to 13.78. Do range and limits have the same meaning? Back to Dick's SS it is within those empty limits and can be standardly loaded outside of the CG envelope. I put in my last post I saw that they were calling it a limit instead of range. These would be two different things. A limit is just that. The empty weight CG must be within the limit. With a empty weight CG range the empty weight CG can be outside the range. If it is outside the range you must perform the fore and aft CG calculations as well as weight. If you look at the sheet I posted I don't think you can get it out, but you are right on the forward edge of the envelope. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted January 12, 2014 Author Report Share Posted January 12, 2014 Do you weigh 160? Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted January 12, 2014 Author Report Share Posted January 12, 2014 Put 1 pound in the rear baggage area. 13.2817 It is easy to balance, my point is that we are capable of being out of the envelope, fore and aft. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted January 12, 2014 Author Report Share Posted January 12, 2014 I understand that. I just don't see why all the interest in this topic. Load the plane and do a CG calculation. For you guys that own your own plane, you should already know when you might be getting close to having a problem. Many CT pilots never do a calc or at least do not calc various configurations because they are told that they can't get it out of the envelope if they try. They also learn that there is no problem flying over gross. I think that these 2 nuggets combined can add up to a bad day. The CT has proven to be forgiving when it comes to W&B issues with the exception of saturated tail fins. A heavy tail fin can result in a plane that is not controllable in pitch. The weight is assumed to be unchanged when you do the calc but in ground handling you might sense a heavy tail condition and realize it would be a safety of flight issue. Link to comment Share on other sites More sharing options...
Doug G. Posted January 12, 2014 Report Share Posted January 12, 2014 I can duplicate this on many CTLS and not be out of range. (The empty weight is higher with a larger arm.) Link to comment Share on other sites More sharing options...
Runtoeat Posted January 12, 2014 Report Share Posted January 12, 2014 This has been very educational and enlightening. If someone gets tired of doing Sudoku puzzles, play with my revised spreadsheet and refer to the C.G. envelope (just a simplified partial part of the envelope from 1000lb to 1350lb). Looks to me if I'm flying alone, I better pay attention to how much fuel I carry and if over 20 gallons, I might need to add some ballast to the cargo area to keep from busting the forward C.G. limit. :unsure: I removed this SS from the other thread and will post it here with revisions and chart added. This chart is for example only. The values shown are visual approximations of the actual C.G. envelope graph. Link to comment Share on other sites More sharing options...
FastEddieB Posted January 12, 2014 Report Share Posted January 12, 2014 In the world of bigger planes, pilots often use collapsible water containers. Essentially no weight when you don't need it, 8 lbs/gal when you do. As an aside, at any given weight a plane will fly faster with a rearward CG. Link to comment Share on other sites More sharing options...
2FlyAgain Posted January 12, 2014 Report Share Posted January 12, 2014 Interesting. Any pilot less than 190 pounds can't fly with full fuel unless he puts some weight in. For better or worse, I weigh 155 lbs and my aircraft empty weight arm is an inch more forward than the example in the spreadsheet. In addition to the usual stuff like a wrenches, a pair of chocks, cleaning supplies, etc., I keep 30 lbs of ballast in the baggage area to ensure that I am not even close to the forward CG limit. But, if I had not done the calculations for various conditions I would not have realized that I could be "underweight" and still have CG problem. From the other thread, I think that some of the confusion stems from whether or not a concept called "empty weight center of gravity range" applies to the fleet of CT aircraft. If I find the right Flight Design person to ask, I will report back to the forum. In the meantime, the ballast stays in the baggage compartment when I fly solo... Fly safe everybody! Link to comment Share on other sites More sharing options...
sandpiper Posted January 12, 2014 Report Share Posted January 12, 2014 In the world of bigger planes, pilots often use collapsible water containers. Essentially no weight when you don't need it, 8 lbs/gal when you do. As an aside, at any given weight a plane will fly faster with a rearward CG. When I was in flight training learning how to fly my uncles helicopters, my instructor kicked me out then brought the Hiller OH-23 to a hover several times while sand bags were added, removed, adjusted, etc until he was happy. Then he got out and I went on my first solo. I wasn't nervous or anything by the time I got to go, I was beyond nervous. Much easier on the nerves if the instructor gets out quickly before the student can worry themselves to death. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted January 13, 2014 Report Share Posted January 13, 2014 Using the factory W&B sheet for my airplane, at my weight of 180 I can't get the airplane out of CG in any condition within gross weight...fuel fuel, empty fuel, max weigh passenger, no passenger, max baggage, no baggage...I can't find a condition that exceeds CG. Link to comment Share on other sites More sharing options...
Tom Baker Posted January 13, 2014 Report Share Posted January 13, 2014 Do you weigh 160? It will balance better if you use the correct arm of 11.8 for the fuel. I came up with a weight of 1031.3 and arm of 13.63 for a 120 pound pilot and full fuel. Link to comment Share on other sites More sharing options...
Runtoeat Posted January 13, 2014 Report Share Posted January 13, 2014 2FlyAgain (Mark) and Tom Baker pointed out the fuel arm in my SS was not correct. This should be 11.8" and I believe it is standard for all CT's. The mistake was corrected and the corrected spreadsheet is posted (below). The spreadsheet now shows my CT meets C.G. envelope limits with all fuel loads when flying solo but I'm right on the limit. Those who point out that it may be beneficial to add a few pounds to the cargo area have a good suggestion. One point about "empty C.G.". I would think this will vary to some extent among our various CT's based on installed equipment. A few years ago, before I purchased my CTSW, there was a lot of equipment removed and replaced (long story). The plane was weighed and a new W&B was logged with associated revised empty C.G. Recently, I installed Matco wheels brakes and axles and Monster 600-6 tires which added 10 pounds of weight. This required another empty C.G. calculation and this too was logged. Consequently, my current empty C.G. is the third iteration. N9922Z W&B worksheet_140113 (chart).xls Link to comment Share on other sites More sharing options...
Runtoeat Posted January 13, 2014 Report Share Posted January 13, 2014 The case where the pilot weighs 155 is right on the edge of the limit with full fuel load of 32 gal. My SS shows 155lb pilot with 32 gal. fuel is about 1085lbs or 13.69" C.G. Extrapolating the envelope graph it looks like 1085lbs should be 13.7" or more to stay within C.G. so it is right on the edge. I can see the merit of adding some weight to the baggage area just to give a little buffer to stay away from the limit. It is always the case as fuel is used, the C.G.situation improves. Link to comment Share on other sites More sharing options...
Runtoeat Posted January 13, 2014 Report Share Posted January 13, 2014 Hi MovingOn. I'm a little rusty with programming excel but setting up the C.G. envelope to reflect the calculated "loaded" C.G. is something I might try to do for a winter "project". Not sure what you mean when you say "Your spreadsheet C.G. limits are empty weight limits"? The SS calculates "loaded" C.G. The graph is just a portion of the "loaded" C.G. envelope. Referring to the graph, this shows if this calculated "loaded" C.G. value is "in" or "out" of the "loaded" C.G. envelope. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted January 13, 2014 Author Report Share Posted January 13, 2014 Dick, Your graph should probably be created after values are entered and at the minimum it should plot CG at take off and CG at fuel exhaustion. I think it would be a lot of work in Excel because you would really need a background image that shows the envelope then overlay a plotted graph. If I was going to do that much work i would abandon the spread sheet approach and write an app that would run on phones and tablets. Link to comment Share on other sites More sharing options...
Doug G. Posted January 13, 2014 Report Share Posted January 13, 2014 In the world of bigger planes, pilots often use collapsible water containers. Essentially no weight when you don't need it, 8 lbs/gal when you do. As an aside, at any given weight a plane will fly faster with a rearward CG. Of course, at some point, controlled flight becomes impossible. Link to comment Share on other sites More sharing options...
Doug G. Posted January 13, 2014 Report Share Posted January 13, 2014 This conversation explains why I once saw an SW that was being serviced that had dumbbells in the luggage compartments. I don't think the issue exists on an LS. Link to comment Share on other sites More sharing options...
Runtoeat Posted January 13, 2014 Report Share Posted January 13, 2014 Hi CT. I appreciate your input and I'm learning a lot about weight and balance by this. Let's see if we're on the same page with my graph. This graph is just a portion of the published C.G. envelope which came with my CTSW. It is supposed to reflect just the upper left portion of the envelope graph which shows the "allowed" loaded C.G.'s when my plane is loaded to a weight of 1000lb to the max. loaded weight we can fly LS at of 1320lb. To find out what where I woulf fall on this graph with fuel exhaustion, all I need to do is use "0" gallons of fuel. My SS would then calculate the resulting C.G. which would consist of the empty plane weight of 738lb, my weight of 180 lbs. The resulting weight of my plane then, with no fuel remaining, is 918lbs and the resultant C.G. is 14.27". Now I would normally go to my graph and find out where I fall with the 14.27" C.G. but there is a slight problem. The C.G. envelope graph actually reverses at the 1000 lb loaded weight and starts showing the C.G. limit increasing as the plane becomes lighter than than 1000lbs. I am attaching a scan of my C.G. envelope. This has a portion highlighted in red with arrows on each end. This partial portion of the of this C.G. envelope is what I have constructed and use with my SS. As far as I know, this is an unchanging chart that was developed by FD Germany using the flight characteristics of my particluar CTSW. you can see how the envelope starts going down and to the right for a loaded weight less than 1000lbs but it still appears that "0" gallons of fuel C.G. of 14.27" is still in the envelope. C.G. envelope.pdf Here's the SS showing "0" gallons of fuel and the resulting C.G. calculation: N9922Z W&B worksheet_zero fuel.xls Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted January 13, 2014 Author Report Share Posted January 13, 2014 Dick, We are on the same page with the exception of your chart being unique. My earlier CT doesn't have one but all others that I have seen look identical. Link to comment Share on other sites More sharing options...
procharger Posted January 13, 2014 Report Share Posted January 13, 2014 When the chute is repacked what needs to be done for weight? Link to comment Share on other sites More sharing options...
Roger Lee Posted January 14, 2014 Report Share Posted January 14, 2014 If all you do is re-install the chute after the re-pack then nothing needs to be done. Link to comment Share on other sites More sharing options...
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