Revision of my previous entry- now using PID controllers.
This is a replication of the LiftSystem featured in the F-35B. The Lift Fan is replicated by a VTOL engine and two VTOL nozzles in the front, while the Three-bearing swivel module is replicated through the Jet engine connected to two hinges. The system gives the pilot fly-by-wire control of the planes pitch attitude, altitude, and rate of climb/descent. Videos of VTOL takeoff and landing below: Both the lift fan and the jet engine use PID inputs when S/VTOL is engaged. Videos of the system in action below:
https://youtu.be/SpLLV71dqps
https://youtu.be/Esono11NRQw
Gear must be down to engage the system. Moving the VTOL slider < 0 will move the rear nozzle for STOL and transition to conventional flight.
VTOL at -1 will enable VTOL flight. In VTOL flight, Rate of ascent/descent is controlled via pitch controls (stick forward for down, stick back for up). Also forward/backward creep can be controlled via the trim slider. Note, S/VTOL requires throttle be above 0 (and meet the conditions below). I recommend keeping it above 50% for STOL.
Featured FT Expressions:
Jet Engine
"(abs(rate(Altitude)) < 10) & (abs(PitchAngle) < 5) & (TAS < 75) & (VTOL = -1) & (LandingGear = 0) & (Throttle > 0) ? clamp(PID((-Pitch * 2.5), rate(Altitude), .2, 0.1, 0.1), 0, 0.25) + (Brake * 100) : ((LandingGear = 0) ? clamp(Throttle, 0, 0.5) + (VTOL * .25) : Throttle)VTOL engine:
"(abs(rate(Altitude)) < 10) & (abs(PitchAngle) < 5) & (TAS < 75) & (LandingGear = 0) & (VTOL = -1) & (Throttle > 0) ? clamp(PID(0, PitchAngle, .2, 0.1, 0.1), 0, 1) : ((LandingGear = 0) ? clamp(PID(-Pitch * 10, PitchAngle, .2, 0.1, 0.1), .1, 1) : 0)"
Explanation:
STOL is engaged whenever the landing gear is down. In STOL, the front fan PID variable is Pitch Angle and the setpoint is Pitch Input. This maintains a neutral attitude unless the pilot gives some pitch input. The Jet engine power is also reduced and clamped to keep the craft under control during transition to/from conventional flight
VTOL is engaged once the following conditions are met:
- Rate of altitude is less than 10
- Throttle > 0
- Pitch Angle is less than 5
- TAS is less than 75
- Landing Gear is Down
- VTOL = -1
In VTOL, the front fan PID variable is Pitch Angle , and the setpoint is 0- keeping the attitude neutral at all times. The Jet power is also controlled via PID with the variable being rate of altitude and the setpoint being the Pitch input. This makes the plane hover when there is no input, but also lets it ascend or descend if there is a pitch input.
Specifications
General Characteristics
- Predecessor Funky Trees Challenge
- Successors 3 airplane(s) +28 bonus
- Created On Windows
- Wingspan 23.4ft (7.1m)
- Length 32.1ft (9.8m)
- Height 8.9ft (2.7m)
- Empty Weight 11,664lbs (5,290kg)
- Loaded Weight 14,156lbs (6,421kg)
Performance
- Power/Weight Ratio 3.333
- Wing Loading 31.4lbs/ft2 (153.5kg/m2)
- Wing Area 450.2ft2 (41.8m2)
- Drag Points 2885
Parts
- Number of Parts 115
- Control Surfaces 6
- Performance Cost 712
@lemoose I haven’t tested it but I think the fix is for all the if variables like VTOL>0 & GearDown? Blah: blah blah need to be clamped between 0-1. It’s a weird fix but often helps. So it should be (clamp01(VTOL>0) & clamp01(GearDown))? Blah: Blah blah. Using ceil() might help too.
@OrderlyHippo Hey Glad you're enjoying the plane! Been a little busy with work and moving but I'll fix up the formula if/when I get back into the game. Haven't played it in months now TBH but every now and then I have an idea (or learn somethin new about a plane) and have to go back in and implement it.
@lemoose Not all edge cases were accounted for. There are times when the rear engine stops working in 'VTOL' at -1 mode while all the conditions are met. Also, some times when the VTOL engine in the front's PID controller will not activate making it bounce up and down, usually due to crazy spinning during a flight. Please limit the parameters so things don't stop after a long flight session only to have to restart since the code malfunctions. I don't understand how PID controllers work, but I have been adding a lot to this plane. I will post it eventually.
@Lilshrimp So, it's been a while but if you still want to know how, I think I have it figured out. You really want to get in the mind set of "slow decent" when landing. The reason for this is that the thrust in front automatically comes out in VTOL down mode to "help" keep the craft level. Meaning if the plane at any moment leans upside down, you'll probably have to re-start. To slow down, use all the air brakes. Slide the VTOL lever down most of the way and have about 20% thrust. When you're going so slow that the wings don't work any more, smack that VTOL lever to the bottom and pull a 180 via YAW controls. Roll during the rotation to slow down further. Once the 180 is complete, if you're drifting backwards, slightly tap the VTOL lever from the very bottom WHILE THE THROTTLE IS AROUND 45% because when the VTOL lever moves out of that smack bottom spot, the auto-leveling system turns off leaving complete rear thrust control completely manual. 45% makes a good ratio of front and rear thrust so you don't do flips lol. Do this as many times as you need to slow down to stationary speed while aiming for the spot. Practice will make aiming easier. My last piece of advice is if you are descending to fast, tap the VTOL lever out of the -1, bottom, position with 50% throttle or so to deactivate the auto pitch system and let you control the rear engine's thrust better. I'd like to know how a real F-35 control scheme would works. I always thought this was like it but never checked.
@OrderlyHippo appreciate the kind words! glad you enjoy my planes
I can't I get it to activate into vertical landing
F4 when?
Very well made! Not the easiest to control while hovering but it’s fun to fly and works pretty well