# Generating lift, sitting still

#### lionheart

Hey all,

Is it possible.... to generate lift... sitting still? One can do this with a helo. Can one do this with a plane?

Bill

#### jx_

not likely still. but maybe at 0.001 knots.

The only possibility I can think of would be CL_de. CL_de is always being actively computed, even if you disable the elevator itself. If you try a really big number and deflect the elevator full, it may generate enough lift to break gravity, but I haven't tried it or run the math.

...unless you can hack the inner variables live of course. I believe Doug Dawson's VTOL gauge does this.

#### lionheart

not likely still. but maybe at 0.001 knots.

The only possibility I can think of would be CL_de. CL_de is always being actively computed, even if you disable the elevator itself. If you try a really big number and deflect the elevator full, it may generate enough lift to break gravity, but I haven't tried it or run the math.

...unless you can hack the inner variables live of course. I believe Doug Dawson's VTOL gauge does this.

Thanks JL.

I didnt know about Dougs gauge. I'll have to ask him about it.

Bill

#### Roy Holmes

Resource contributor
To the extent that it can sit still and rise in the air, the Harrier can do what you are asking for.

At this point I will duck to avoid the purists who say it is done with thrust, not lift.

As regards generating aerodynamic lift at zero airspeed it is possible through flown boundary layer control, but not enough most likely

Roy

#### jx_

At this point I will duck to avoid the purists who say it is done with thrust, not lift.
Roy
Lol. Love it.

I figured it out guys. I will post here shortly.

#### lionheart

LOL......

Aim downwards, like a blimp would do.

A true VTOL would have control of that though, like a Harrier.

How did you solve it?

#### jx_

Well, it is weightless, but I can't get it to descend reasonably and it will only accelerate to 4 knots.

I set a helicopter's engine to produce thrust with high mass flow and very low velocity. So the 600 pounds of weight is being supported by 600 pounds of air moving at 32 ft p/s.

The problem is when you change the lift vector, the lifting thrust component is reduced and the weight is no longer supported. If the angle is unchanged, the craft will climb until it slows to a hover, then just sits there. Sometimes it climbs more, even with the engine off, until the rotors come to a complete stop. Then you fall like Wiley Coyote.

#### lionheart

Very cool! At least you got it working.

I got mine to act like a sort of blimp, though that is what I started out wanting and needing.

Mine will lift off gently from a horizontal movement similar to a blimp appears to hover at times. I set weight to -0.01 and the system changed it I guess for pilots and fuel, so that is up to 510 LBS. I took the pilots out just to see what would happen and the craft quickly flies up in the air, loops over and crashes into the tarmac violently. ??

I changed things like wing area (huge!!!), weight (less then zero, but it recalculates it), elevator, aileron, and rudder areas (for cool ultra slow manuvering), and had to increase MOI's and 'effectiveness' settings.

Oddly, effecting Stall had some wierd effects. -200 was fine, 0 has the alarm going off on the tarmac parked. 1 was not good as the craft will dump itself into the ground at what seems like over 1 knot. I then tried -0.001 and found that if you gas the engine (or sometimes not), the craft corkscrews into the ground violently (wings flip over fast and it crashes). Going to -0.01 is fine and the craft appears to hover in the air, weightless like a balloon, the speed barely perceptible. But.... If it hits near 0 knots, she dumps down into the ground and if you are high, it appears to try to spiral. (I have tons of wing area, so it must act like an umbrella of sorts, the flat area effect, a giant card).

Another thing is that it will only get up to about 100 knots as it is. I have to hold down the stick to keep the nose down or it tries to climb like crazy at full speed. At slow speeds its fine.

I am going to try to attach the Cessna 172 aircraft file here so you can check it out.

Bill

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#### jx_

No matter how much lift your wing produces, it will never work because Lift requires velocity.

Without velocity lift = 0, even if the weight is set to 0.

But it's good to try and see what the sim will do. You never know what you might come across.

#### lionheart

No matter how much lift your wing produces, it will never work because Lift requires velocity.

Without velocity lift = 0, even if the weight is set to 0.

But it's good to try and see what the sim will do. You never know what you might come across.
Roger that. Explains why it falls fast out of the sky when it hits stall.

Oddly, with the way the airfile is now on this Cessna experiment, it will tend to float forward and sideways while on the ground as though its in space. It refuses to sit on the landing gear. Probably adding some weight will cure that but will increase the downward plunge when it hits stall.

I tried to make Spoiler a 'downward force' and had the wildest reaction. It did a sort of loop while facing forward and then strikes the ground and crashes. Sort of hilarious to see. Trying to fine tune it, I discovered it had a point where it would stop doing this, but had no reaction either for causing a downward force.

Bill

#### mgh

It's straightforward to get anything to hover using SimConnect. It's another matter to control it realistically.

#### jx_

It's straightforward to get anything to hover using SimConnect. It's another matter to control it realistically.
How is it done in SimConnect? I've never used it before.

#### vololiberista

Could you not have a low speed flying wing model in the airfile. But your actual model looking somewhat different.
Also you'd need to find a way to vary the weight from panel control. Dropping sandbags, water, passengers etc.
vololiberista

#### mgh

:jx_

SimConnect permits direct contol of linear and angular velocities in body axes. It also proveides access to the corresponding lnear accelerations but not angular accelerations - which is not helpful.

#### lionheart

I started to look into SimConnect once. From what I saw, it is C++ or such a code as that, and I stopped there. I can barely write in XML.

If only SimConnect was super easy, like Air and Config files; turn this on, adjust this, slider to 0.35, etc.

Vololibirista; basically I have done that. It behaves a bit oddly though, lol. Floats around, even on the ground, slowly turning about.

Bill

#### jx_

you can also add extremely unrealistic amounts of lift using the CL AOA vs Mach table. Since your blimp is slow, you can reduce that table to Mach .2 and below and make it curve upward the slower you go.

It won't solve your issue of zero velocity hover, but would produce substantial lift at any speed greater than zero.

Stay out of bad weather though!