Fuel Management Systems

[Guest Ron Freimuth]

>Hi Ron, >>The aired.ini on http://www.avhistory.org/ seems dated and >optimized to CFS compared to the one I got directly from >you. Has it been updated to account for all the >known/unknown issues for fs2002. There was a problem with the link to my Aired.ini at the top of the AIR file Forum, that may have been fixed. I checked the version when set the correct link and it was recent. Howver, you probably have a more recent version. The one attached to a message here was dated the 13'th. I keep making changes, sometimes just in nomenclature. The main stuff in the AIR file is pretty stable.>I also downloaded and installed the CFS3 avsdk.msi. It >seems to give some new details for MOI I had not seen >before. Its in the Aircraft Container Overview.doc, p.7. >It must be what FS2002 Aircraft Editor uses since they refer >designers to FSAE to build the aero. Is that the CFS3 SDK released recently? That requires G-Max to be installed? There are ways to calculate the MoI's from the AC weight and dimensions. In fact, Greg P. at avhistory wrote a VB app that lets you enter the AC weight, span, length, and type and it does the work for you. I've also found tables of AC MoI's and other data at various sites on the WEB. It appears that Roll MoI and Pitch MoI need to be quite different or an AC can be difficult to get out of a spin. I just noted that in an aerodynamics text I have. Ron

[Guest ChrisTrott]

Seems I've sparked an interesting thread here.For those of you who are interested in how much the fuel can effect the CoG of an aircraft, load up one of these planes-B-727 (Series)B-747 (Series)MD-80 (Series)DC-9 (SeriesMD-90 (Series)These aircraft all have VERY sensitive CoGs.Now for the CG exercise- Load up the plane with the fuel like thisB-727, MD-80, DC-9, MD-90 - Full Wings and Empty Center (or 1&3 full, 2 empty)B-747 - #1 & #4 Main and Reserves filledIn each case, with no other payload (i.e. empty plane), the aircraft should promptly rotate back on its tail. If it doesn't, then either the Fuel Tanks are mis-located, the Main Gear contact points are mislocated, the engines are not located and weighted correctly, or the static CoG is improperly placed. I know that Mike Stone's B727 is setup wrong (don't know which of the factors). I can actually fly the plane without problem with an empty center tank, which in real life would be impossible. I haven't tested POSKY or MelJet's 747s yet for this to see about them, nor have I tested the default MD-88 or other aircraft listed, I just know that this is what they do in real life.From your friendly ASIG Aircraft fueler,

[Guest Ron Freimuth]

>For those of you who are interested in how much the fuel can >effect the CoG of an aircraft, load up one of these planes- >>B-727 (Series) >B-747 (Series) >MD-80 (Series) >DC-9 (Series >MD-90 (Series) >>Now for the CG exercise- Load up the plane with the fuel >like this >>B-727, MD-80, DC-9, MD-90 - Full Wings and Empty Center (or >1&3 full, 2 empty) >B-747 - #1 & #4 Main and Reserves filled >In each case, with no other payload (i.e. empty plane), the >aircraft should promptly rotate back on its tail. If it >doesn't, then either the Fuel Tanks are mis-located, the >Main Gear contact points are mislocated, the engines are not >located and weighted correctly, or the static CoG is >improperly placed. Yes, most FS AC are set up incorrectly (in just about every way possible). I check the FAA TCDS file for CG range and make sure my AC don't tip on their tails with full aft payload. At least for the SEL's. I did see a picture of a jet transport that had tipped on its tail when unloaded incorrectly. Main LG location is critical, too far aft and an AC will be hard to rotate on TO. Too far forward and it can tip on its tail. Further, nose wheel steering is weak if there isn't enough weight on it. FS simulates this quite well, but one has to set up the AC correctly. From drawings, jet transports generally have the MG half the MAC lenght behind the 1/4 MAC CoL. So, if CG moves back to 75% MAC the AC would tip on its tail. However, the Empty CG may not be at 25% MAC, and the payload and/or fuel tanks generally are located to bring it close to 25% MAC -- at least after some fuel has burned off. TO is easier with an aft CG, since it takes less UP trim to get good rotation. Ron

[Guest ChrisTrott]

> From drawings, jet transports generally have the MG half >the MAC lenght behind the 1/4 MAC CoL. So, if CG moves back >to 75% MAC the AC would tip on its tail. However, the Empty >CG may not be at 25% MAC, and the payload and/or fuel tanks >generally are located to bring it close to 25% MAC -- at >least after some fuel has burned off. TO is easier with an >aft CG, since it takes less UP trim to get good rotation. Just FYI- Most planes I work around are loaded with a FORWARD CoG for departure. FedEX and UPS especially won't let their aircraft depart if the CoG is too far aft of "normal" loaded CoG. When I look at the final load plan screen at both UPS and FedEX after I'm done fueling the plane and they've got all the info in, usually the CoG is around the 30-40% CoG (with 0% being the forward CoG limit and 100% being the aft CoG limit) They try to keep it balanced perfectly, but usually you end up being a bit forward loaded. I know most pilots (including myself) prefer a forward CoG over an AFT one. It does take more up trim on departure, but it also makes the plane less likely to stall on departure from having the CoG too far back or risking a weight shift on departure from having all that weight back there.

[wsieffert 0]

Hi Ron,Yes, I believe you need GMAX 1.2 installed, which I have, since it provides the gamepack modules for GMAX. It also provides five Word documents. Why they needed to incorporate those into the gamepack, I don't know.There is also a mission SDK available. Neither require CFS3 to be installed. Again I don't understand why they put them in an installer package format. The mission SDK is just a Word document.BTW, I was using Herv'e Sors latest AFSD! Very nice program. His updates are tremendous. I am trying to redo the 717-200 aero. It immediately pointed out my errors, talk about aft CoG. Probably 30yds behind the aircraft!!!:-lolThe CFS3 files are available at: http://microsoftgamesinsider.com/CFSInsider/default.htm

[Guest Ron Freimuth]

>>least after some fuel has burned off. TO is easier with an >>aft CG, since it takes less UP trim to get good rotation. >>>Just FYI- Most planes I work around are loaded with a >FORWARD CoG for departure. FedEX and UPS especially won't >let their aircraft depart if the CoG is too far aft of >"normal" loaded CoG.>forward loaded. I know most pilots (including myself) >prefer a forward CoG over an AFT one. It does take more up >trim on departure, but it also makes the plane less likely >to stall on departure from having the CoG too far back or >risking a weight shift on departure from having all that >weight back there. That's true also. Forward CG is more stable. More recent jets have stability enhancment systems and move the CG rearward during cruise to reduce 'trim drag'. The 747-400 has fuel tanks in the three tail surfaces. I modified the FS2K2 747 a bit and noted CG is at 36% MAC (or more) when tanks are full and payload brings it to 875,000 lb. Probably the empty CG or payload should be changed to bring it within the aft limit. Ron

[Guest Ron Freimuth]

>Hi Ron, >>Yes, I believe you need GMAX 1.2 installed, which I have, >since it provides the gamepack modules for GMAX. It also >provides five Word documents. Does the document on the 'aircraft container' have any better information that provided for FS2K2?>BTW, I was using Herv'e Sors latest AFSD! Very nice >program. His updates are tremendous. I am trying to redo >the 717-200 aero. It immediately pointed out my errors, >talk about aft CoG. Probably 30yds behind the >aircraft!!!:-lol Getting the CG to read correctly can be a problem. I have more than one AC that appears to fly well with CG way off. I suspect it isn't, and the CG variable reads incorrectly due to the settings in aircraft.cfg. However, I do get the CG to come out at 25.0% when I calculate all the moments and set the payload for 25% balance. Also setting the wing parameters in aircraft.cfg to a 'rectangular wing' and the LE 1/4 the length of the MAC ahead of the desired CG. In these cases, I set the 'root_chord' to the length of the MAC and the taper and sweep to zero. I had suggested to Herve' that a Balance number be calculated consistent with the 'load moment' shown in many SEL PoH's. He may do that in AFSD Pro. Which should be able to log flight data. I also suggested many other things. This version will be so arcane that he doesn't expect to UL it -- but it will be available for those who can use whatever it displays. BTW, if you watch the AFSD Aerodynamics Window flying the MS 747-400 you will see the "Mach Drag", Cdm go negative at cruise speeds. Just one stupid thing set by MS. Of course, 'Mach Drag' should start increasing at about Mach 0.80 and normally peaks at 1.0. Ron