Dowding its not "blade elemental theory" its blade element theory.
Straight from the man himself,
X-Plane goes through the following steps to propagate the flight:
1: Element Break-Down
Done only once during initialization, X-Plane breaks the wing(s), horizontal stabilizer, vertical stabilizer(s), and propeller(s) (if equipped) down into a finite number of elements. The number of elements is decided by the user in Plane-Maker. Eight elements is the maximum, and studies have shown that this provides roll rates and accelerations that are very close to the values that would be found with a much larger number of elements.
2: Velocity Determination
This is done twice per cycle. The aircraft linear and angular velocities, along with the longitudinal, lateral, and vertical arms of each element are considered to find the velocity vector of each element. Downwash, propwash, and induced angle of attack from lift-augmentation devices are all considered when finding the velocity vector of each element.
Propwash is found by looking at the area of each propeller disk, and the thrust of each propeller. Using local air density, X-Plane determines the propwash required for momentum to be conserved.
Downwash is found by looking at the aspect ratio, taper ratio, and sweep of the wing, and the horizontal and vertical distance of the "washed surface" (normally the horizontal stabilizer) from the "washing surface" (normally the wing), and then going to an empirical look-up table to get the degrees of downwash generated per coefficient of lift.
3: Coefficient Determination
The airfoil data entered in Part-Maker is 2-dimensional, so X-Plane applies finite wing lift-slope reduction, finite-wing CLmax reduction, finite-wing induced drag, and finite-wing moment reduction appropriate to the aspect ratio, taper ratio, and sweep of the wing, horizontal stabilizer, vertical stabilizer, or propeller blade in question. Compressible flow effects are considered using Prandtl-Glauert, but transonic effects are not simulated other than an empirical mach-divergent drag increase. In supersonic flight, the airfoil is considered to be a diamond shape with the appropriate thickness ratio... pressures behind the shock waves are found on each of the plates in the diamond-shaped airfoil and summed to give the total pressures on the foil element.
4: Force Build-Up
Using the coefficients just determined in step 3, areas determined during step 1, and dynamic pressures (determined separately for each element based on aircraft speed, altitude, temperature, propwash and wing sweep), the forces are found and summed for the entire aircraft. Forces are then divided by the aircraft mass for linear accelerations, and moments of inertia for angular accelerations.
5: Get Back to Work
Go back to step 2 and do the whole thing over again at least 15 times per second. Aren't computers great?
The newest enchancments/fixes are now.
New engine type: tip rocket! These are the rockets on the tips of helo rotors that turn the rotors without any need for a tail-rotor!
They look pretty funky at night with the rotor spinning round and round with flame shooting out of the tips!
New VTOL control option: Differential collective with pitch input: This is used in VTOLs with engines fore and aft of the CG
to control the atitude of the aircraft in hover. Design your own heavy-lift 4-engine Osprey now with very precise pitch control
by increasing or decreasing collective pitch on the front or aft rotors in hover. No more need for cyclic control!
New VTOL option: LIFT FAN! Here is how it works: A drive-shaft is connected from the JET ENGINE to the FAN.
When engaged, the jet engine sacrifices some part of it's thrust to drive this driveshaft which is connected to the fan.
In this mode, you get less thrust from the JET engine (because it is turning the driveshaft hooked to it's turbine), but
the shaft is turning the lift fan, which uses up the power to produce thrust itself! This is how the (real) F-35 works!
(the jet engine is in the back, the lift fan in the front... they engage the lift fan for hovering flight only)
Now you can simulate it in X-Plane! Here is how it works: You specify what percentage of the jet engine's output is sent to the
fan, and designe the fan just like you design any propeller in Plane-Maker. In the sim, when you transition to vertical flight,
you can wtch the prop visibly spin up as it starts producing lift for you! Onbly in X-Plane, that's for sure!!!
Example: If the jet engine puts out 20,000 lb of thrust, and you duct HALF of the output to the drive-shaft, then the jet engine will now
put out only 10,000 lb of thrust, and the fan will absorb the rest of the power. Does that mean the fan will put out the remaining
10,000 lb??? NO WAY!!!! The fan accelerates air at a much different rate, over a much different area, with a much different
efiiciency and peed range than the jet, so the fan will be no means put out 10,000 lb! In fact, if you design the fan right,
you may get that fan putting out 20,000 lb of thrust! Voila! A 20,000 lb het engine is now putting out a total of 30,000 lb of thrust!
You are now hovering in a 30,000 lb airplane with a 20,000 lb thrust engine! "Impossible!", you say? NOT AT ALL! The jet engine
accelerates a LITTLE BIT OF AIR a LOT (small engine face, exhaust at near Mach-1, which is efficient at high speed) but the lift
fan accelerates a LOT OF AIR A LITTLE (big fan face, exhaust at maybe 100 knots, which is much more efficient at low speed).
So, since the fan need only run at LOW SPEED (you don't need to HOVER fast!!!) you get a lot of thrust-augmentation by ducting
the jet's output to the fan!!
Now the challenge: Huch more lift YOU can get by ducting power OUT of your jet engine(s) to the fan that you design????
You design the fan in Plane-Maker like you deisgn props. If you play your cards right with the fan radius and size and
design speed and RPM and fan airfoils, HOW MUCH MORE THRUST CAN YOU GET??? Find out with X-Plane!
Reverse-flow over wings, and props improved.
This helps in those backslides, helos, and high-sped autogyros.
New blown flap improvement: Blowing speed foud for you based on the throttle reduction you decide...
and also you can blow air over ALL the control surfaces to keep flight control effectiveness at low speed.
Flap-deflection with pitch and roll for high-lift manuevering.
Engine idle thrust and tire rolling friction coefficient tweaked to get that taxiing just right in the heavies.
Improved wing-tilt modelling: All element locations now found when the wing tilts for steering.
Transmission drag now taken out of helos and VTOLs.
Thrust-reverser lockout on the props if props not full forwards, as in reality.
Auto thrust-reverse on touchdown, as used by Swedish Viggen fighter.
Lateral cyclic with heading input, for helos like the CH-46 Chinook, and other new prop and rotor control in Plane-Maker.
So dowding, I would love to hear what portions of this you think that Aces High does/doesnt do.
Xplane simply has the better system of "simulating" reality, (interaction of an object through a fluid mass "air", as opposed to that of Aces High).
Aces high does very well in many areas, but because it is firstly a game its demands of simulating reality are spread out in more directions then x-plane: guns/damage modeling/multiplayer/graphics etc...
Not that it means I am an expert in the laws of aerodynamics, but I am a real life pilot, have flown wwii fighter trainers, as well as multiple civil aircraft. Reality is Very fluid, xplane catches all the little dynamic occurences faster/more accuately then ANY other PC based simulator/game thus far and it is improving with each passing update.
