---------------------------------------------------------- Allegro-List Digest Archive --- Total Messages Posted Sat 12/09/06: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:37 AM - Re: Empty weight and C.G. LocationEmpty weight and C.G. Location (Thom Riddle) 2. 08:40 AM - Re: Empty weight and C.G. Location (Dave Grosvenor - DreamWings) ________________________________ Message 1 _____________________________________ Time: 06:37:26 AM PST US From: Thom Riddle Subject: Re: Allegro-List: Empty weight and C.G. LocationEmpty weight and C.G. Location Hugh, The maximum legal weight for an LSA in the USA that is not equipped for water operations is 1,320 lb. Equipped for water operations, the max is 1,430 lb. BUT each manufacturer can specify any MTOW for their aircraft at those weights or lower. The Fantasy Air USA website shows the MTOW at 1,232 lb. I did some calculations on change in Vs1 based on MTOW of 1,232 lb. vs. 1,146 lb. At MTOW of 1,232 lb. the Vs1 is just within the legal limit of LSA stall speed which is 45 knots. That is probably (just and educated guess) the reason they chose 1,232 lb. for the MTOW for LSA category, since a MTOW of higher than that would have disqualified it by virtue of the higher stall speed. As I said, the airplane handles fine at over 1200 lb. But the load limit at 1,232 lb. must be factored downward from the +4g/-2g numbers that were determined at 1,144 lb. Positive flight loads of 4 g at 1,146 lb. would equate to 4 x 1146 = 4,584 lb. Thus at 1,232 lb, a total flight load of 4,584 would be equivalent to a 3.72g load limit at 1,232 lb. (4584/1232=3.72). Do similar math for the negative load limits. These numbers are still very close to the required minimum load limits for standard category aircraft like Cessnas (+3.8g). There are other factors that should be considered when the designers calculate a MTOW, including the forces on the landing gear, particularly during landing operations. This may be one of the reasons they increased the dimensions of the main landing gear since the early design to accommodate the heavier MTOW in LSA category. Also, the CG limit range is between 25% and 35% of mean aerodynamic chord (MAC) which is 44" on the Allegro 2000. 25% of 44" is 11" for the forward limit and 35% of 44" is 15.4" for the aft limit. The location of the empty weight CG has no real significance, as long as the CG is within this range when in operation. CG range in light aircraft rarely exceeds 5" from fore to aft limit and the Allegro 2000 limit range is 4.4" (15.4-11), so that is a normal CG range. Unless you go way way over the baggage limitation, it is difficult for typical American sized pilots and passengers to get out of CG range in the Allegro as long as you do not exceed the MTOW of 1,232 lb. Attached is an Excel spreadsheet of my our W&B. You can modify this to suit your airplane. You may notice that the location of the baggage arm on my spreadsheet is further back than what the factory gives us. My numbers are from measuring to center of the baggage area not the bulkhead just behind the seats. Please use your own numbers as this is for our airplane only. If for some reason the file is not attached (have had troubles with the attachment process) and you want a copy of my spreadsheet, email me directly. Thom in Buffalo ________________________________ Message 2 _____________________________________ Time: 08:40:58 AM PST US From: "Dave Grosvenor - DreamWings" Subject: Allegro-List: Re: Empty weight and C.G. Location Hugh My Allegro (factory-built) weighs 308kg or 672 lbs. It has metal skinned wings, strobes and nav lights, wheel spats and a GRS ballistic chute. The chute weighs 13kg, so without it the empty weight comes out at 295kg or 650 lbs. I think your scales must be out. Considering the parts for the kit are almost completely factory built, I can't see where you could possibly pick up so much weight during the build process. We have now added wing tanks but have not re-weighed it since then. Dave ----- Original Message ----- > > Time: 12:47:24 PM PST US > From: "Hugh McKay III" > Subject: Allegro-List: Empty weight and C.G. Location > > Gentlemen: > > I have just weighed my kit built Allegro 2000 (empty weight*) to compare > with the published empty weight in the Fantasy Air Flight and Operating > Manual. > > * empty weight = weight of plane with standard instruments, engine, > coolant, > oil, ELT, & Battery (no fuel and no BRS). > > My empty weight* is 320 Kg, or 704 lbs. (Nose wheel = 154 lbs., Right Main > wheel = 270 lbs., Left Main wheel = 280 lbs.) > > The Flight and Operating Manual states that the empty weight should be 275 > Kg or 605 lbs. I am 99 lbs (16%) heavier than what is published for the > empty weight! The published MTOW is 520 Kg, or 1144 lbs. This leaves me > only > 440 lbs for a BRS, Fuel and 2 occupants. Those numbers are as follows: > > Main fuel tank fuel 14.5 gal. = 88.97 lbs. > BRS = 35.00 lbs. > Wing Tanks Fuel 10.4 gal. = 64.00 lbs. > My Weight = 150.00 lbs > > Total = 337.97 lbs. > > 440 lbs. minus 337.97 lbs is 102.03 lbs max weight for the passenger in > order not to exceed the MTOW of 1144 lbs. With these numbers, in reality I > cant take a passenger unless he is a child or a very light weight adult. > > What is the basis of the 275 Kg (605 lbs.) stated in the F and O Manual? I > dont understand why I am 99 lbs over the published empty weight! I have > nothing more in this plane at empty weight* other than what I have stated > above with the *. What are the empty weights running for the ready to fly > Allegros with similar items? > > With a total empty weight of 704 lbs. the c.g. is 12.18 inches behind the > leading edge. The maximum allowable distance is 390 mm or 15.35 behind the > leading edge. 12.18 is 81% of the limit. The F & O Manual states that the > c.g. of the empty aircraft is almost exactly the same for the aircraft > with > one or two pilots and with an empty or full fuel tank. According to this, > the empty c.g. and the MTOW c.g. stays the same (i.e I do not have to > weigh > the plane with fuel, and passengers to calculate a new c.g. . Is this > correct? > > I have sent this information to the US Distributor, Fantasy Air USA, but I > would like to get some independent feedback concerning the weight issue > (605 > lbs. Vs. 704 lbs.). Do any of you know your comparable empty weights, and > would you share them with me? Any and all help will be deeply appreciated. > > Hugh McKay > Allegro 2000 > Rotax 912UL > N661WW ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message allegro-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Allegro-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/allegro-list Browse Digests http://www.matronics.com/digest/allegro-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.