Selig's Newsletter: SAE Heavy-Lift Albatroz Airplane Lands in SeligSIM
The heavy-lift Albatroz SAE airplane is ready for download for the SeligSIM RC Flight Simulator. Both the full simulator and this latest airplane download are free.
The Albatroz design was mentioned in the prior newsletter. Here are more details about the design. The “Albatroz Aero Design” RC airplane, with a wingspan of 92 inches (2.33 m), is the Brazilian UDESC (University of the State of Santa Catarina, Brazil) 2023 entry in the SAE BRASIL AeroDesign competition. This airplane competed in the Micro Class and the UDESC Albatroz team placed 2nd in the flight competition.
Among the many design requirements for this class, one included maximizing payload weight while designing for a time disassembly to fit inside a small container. Another requirement was takeoff from an elevated platform 165 inch (4.2 m) long and 35 inch (0.9 m) high. Also, being electric powered was a requirement.
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João Vitor S. de Sousa, a member of the Brazilian Albatroz team and mechanical engineering student at the University of the State of Santa Catarina in Brazil, created the graphics model using Blender. The model was converted to the file format used by the simulator. He also provided some of the physical data (dimensions, weight, moments of inertia, motor, propeller, etc) and aerodynamics data that were compared with my own predictions that were then used in the aerodynamics modeling.
The wing airfoil is a design that was optimized by the team to meet the competition requirements and objectives. The resulting airfoil generates a maximum lift coefficient of around 2, which is typical of airfoils used in SAE heavy-lift competitions. As can be expected, the stall is rather sharp as a result of the high maximum lift coefficient.
If you are curious how these SAE heavy-lift designs might fly, this one will give you a taste of that. The airplane itself uses light weight construction, but when loaded up to its target flight weight of 14.5 lb (6.6 kg), the wing loading is 33 oz/ft² (102 g/dm²). By comparison, a typical RC thermal-duration sailplane of this size might have a wing loading of around 5-8 oz/ft². Another comparison is the aerobatic Extreme Flight Laser EXP (91-in span) that weighs around 10 lb (4.5 kg).
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The control setup includes ailerons, a full flying vertical fin, and a stabilator. The ailerons are set for +/-20 deg. The stabilator is set for 20 deg up elevator (airplane nose up) and 10 deg down. The vertical fin is +/-24 deg. There is only one flight mode (full throws) and no expo.
With the design being optimized around many factors and the competition flight path being one circuit around two flag poles (110 meters apart), the handling qualities itself was not optimized. There is barely enough aileron authority to bank the airplane, but with coordinated rudder and ailerons, the turns are sufficient when initiated with enough planning.
The tail boom is angled up around 20 deg and that is to avoid contact with the ground on rotation and also during high-alpha landings. There is more than enough elevator authority, and too much up input can produce a snap followed by a spin. The stabilator airfoil is a high-camber design. It is installed inverted for ample tail downforce.
Takeoffs can be tricky. I think the right way to take off is full throttle while easing in some up elevator. Without enough elevator, the propwash from the propeller hits the root wing area. Then the high wing camber wants to put much of the airplane weight on the nose wheel, and lift the rears. In that condition, it is very easy for the airplane to dig in and “oversteer.” Oversteer seems like the more appropriate term than the usual one - ground loop. In a full side drift, there are some interesting ground dynamics that cause the wheels to stick-slip, i.e., slide and stick repeatedly and even come to a halting stop by catching on the outside wheel. Turns on the ground can be described as a “wingtip pivot turn” where the turn pivots about the tip of the inside wing.
If flown slowly into a stall, there can be some wing rock. Exactly how that dynamic is generated from the aerodynamics is not perfectly clear (yet), but it happens. With more nose up elevator stick and slower airspeed, and it will tip stall abruptly and head nose down into a spin. The airplane can then enter into a fully developed flat spin. The spin is rather fast, partly because there is very little side area to slow it down. From a flat spin, adding power can sometimes arrest the spin and allow for recovery. Sometimes the spin is not recoverable.
So far the sim model does not include breakable parts, i.e., parts do not go flying off in a crash. Many of these SAE airplanes tend to catch a wing and cartwheel, but I've not seen many full airframes busted into bits (perusing videos on YouTube). If I do include broken parts in the sim model, expect to be hitting reset key far more often than you'd like.
The video links below show the Albatroz team flying this airplane and practicing the timed disassembly/assembly, including the packing in the box. More links will take you to the Brazil SAE AeroDesign competition site. The rules used in Brazil are different from the ones used in the US, but the heavy-lift theme is a common thread.
Downloading and Installing the Albatroz Aero Design Airplane
Go to the SeligSIM site and download the DLC (downloadable content) for the Albatroz and also grab the 2024b update. The 2024b update includes some under-the-hood aerodynamics support for this new Brazilian SAE airplane. Without the 2024b update, the airplane will not fly as intended.
Assuming that you have already installed the full simulator, go to https://www.seligsim.com/download.html and download these two files:
SeligSIM-2024b-Update-18002-3656.exe
SeligSIM-DLC-02-AlbatrozAeroDesign.exe
Remember to run theses exe installers as Administrator on your Windows computer. The order of install does not matter.
After installing, when you start SeligSIM, you should see that you're running version 2024b and a pop-up will ask you if you want to install the “AlbatrozAeroDesign” airplane. Click to confirm. Only install from trusted sources. At present, the only official site for SeligSIM downloads is from: https://www.seligsim.com.
About Selig’s Newsletter
Subscribers to this newsletter will be among the first to know when new airplanes and new features are planned and released for SeligSIM (FS One). I will also discuss some of the finer details that go into RC flight simulation, share tips and techniques for flying, and touch on aerodynamics and flight dynamics now and then. In addition to the usual coverage, keep an eye out for occasional thoughts and ideas on other related topics in RC modeling.
Until next time, happy landings!
Notes:
https://www.seligsim.com/download.html
https://www.youtube.com/watch?v=Wx-nDc47NCo&ab_channel=EquipeAlbatroz
https://www.youtube.com/watch?v=QpsWFDHwlhs&ab_channel=EquipeAlbatroz
https://www.saeaerodesign.com/
https://saebrasil.org.br/programas-estudantis/aero-design-sae-brasil/
https://www.youtube.com/watch?v=hCGN9NwZOgo&ab_channel=CanalSAEBRASIL
https://www.youtube.com/watch?v=dKzYybLc0Ts&ab_channel=CanalSAEBRASIL