Experience the Thrill of Tail Sitters in FS One
VTOL Tail Sitters Reimagined and Flyable, Free with DLC 5
This newsletter announces the addition of two tail sitter aircraft to FS One. You could call them Yaks “reimagined.” Inspired partly by the XFY-1 “Pogo”, XFV-1, and SkyTote (Convair, Lockheed, and AeroVironment designs) and simply my own interest in how a tail sitter might fly, using the Yak 54 as a base airplane was the quickest way to test out the flight characteristics and the challenge of landing one. The new airplanes are available as free downloadable content (DLC) for you to explore and enjoy inside FS One.
The Yak 54 base airframe was extended with the addition of an aft pyramidal truss frame rig (formally called a space truss) that converges on four contact pads or “feet” that in real life would likely be made of carbon to keep the weight down. This type of design for upright takeoff and landing necessitates a thrust-to-weight ratio greater than 1, and this RC Yak 54 model has that with its approximate 2:1 thrust-to-weight ratio. Additionally, it requires 3D flying skills for hovering to a touchdown (or use the keyboard “O” key to make hovering easier in FS One). While knowing how to fly 3D is not essential for takeoff, that skill becomes very important for upright landing! The video below makes it all look too easy.
The first tail sitter is specifically designed to land and take off solely from an upright tail sitter position. The cg is centered over the squarely arranged pyramidal four landing legs. In contrast, the second model has a canted landing leg arrangement that allows it to take off and land both conventionally and upright.
For both configurations, to maintain better control during upright landing in ground effect, the rudder and elevator control surfaces are offset from the ground so as to avoid the slower propwash closer to the ground.
As the propeller wash approaches and impinges on the ground, it has to slow and turn 90 deg right at the ground (as it sprays onto the ground). That means the flow stagnates there and the tail surfaces, if immersed in the stagnant region, would not have much control authority. So the tail surfaces are set off away from the ground. It makes the entire airplane stand very tall. The c.g. is in fact nearly 7 ft high! And the spinner reaches is a whopping 9.5 ft high.
Both tail sitter aircraft employ a conventional single propeller. The resulting propeller torque can be counteracted by the ailerons immersed in the propwash. The XFY-1 “Pogo”, XFV-1, and SkyTote designs all used counter-rotating propellers to cancel out torque from the propeller system and improve controllability.
Adding a counter-rotating propeller onto these designs would be interesting to test out. That would be a new future DLC, but you can get nearly the same effect by making a copy of the airplane and editing the aerodynamics. Set the parameter “mShaftTorque_UserFac” to zero to zero out the propeller shaft torque. With that adjustment (kludge), there will still be some propeller swirl flow that will affect the downstream surfaces, but the net torque from the swirl flow is a much smaller effect that the direct propeller torque.
The landing gear feet are somewhat grippy. If there is some interest, another tail-sitter DLC could be created to include landing gear feet that mimic rolling castor wheels - near frictionless. With wheels, the square-pyramid arrangement is easier to land because on touch down the airplane will slip into a level landing attitude rather than gripping and tipping over. The canted arrangement is a bit more tricky with or without grip. In fact, it seems trickier with slippery landing feet.
Physics Engine in FS One
The key advantage of FS One over other simulators is its more accurate physics engine - aerodynamics, flight dynamics, and ground reactions. In the case of these tail sitter designs, FS One captures their unique handling qualities and delivers an experience that closely resembles real-life flying.
#1 Best Selling
We cannot say we’re the “#1 Best Selling” because we’re free. We cannot say we’re the “Most Popular” because we just don’t have a megaphone big enough to reach everyone in the RC universe. But we have “scienced” the you-know-what out of RC flight simulation, and we will boast about that.
Free Simulator and Free Downloads
For those curious about the flight dynamics of tail sitters or simply looking for an interesting challenge, this presents the perfect opportunity to explore their distinctive characteristics within a simulation environment that boasts a high degree of realism.
This is your invitation to download these tail sitter aircraft and immerse yourself in the challenging experience of flying these new machines in FS One. If you have not yet tried the simulator, now is an excellent time to discover what you have been missing.
The online User Manual goes through all the setup steps, but shout out of you need help.
About the FS One Newsletter
Subscribers to this “RC Flight Simulation with FS One” newsletter will be among the first to know when new airplanes and new features are planned and released for 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.
Thanks for reading the newsletter: RC Flight Simulation with FS One! Subscribe for free to receive new posts and support my work.
Background panorama photography (first image) by Simon Inns is gratefully acknowledged and published under the CC BY 2.0 license.