In a previous post you mentioned the case with the pilot lying on a table.
When the pilot, with the Portable Flyer secured onto his shoulders / torso, is lying on a small table, abutting on it with his lower chest, with his head and engines extending outside the table from one side, and with his hips and legs extending from the opposite side of the table, pilot’s legs counterbalance the engines / propellers weight.
If the propellers “look” slightly upwards, and the engines are cranked, the upper body of the pilot tends to lift, unless the legs of the pilot bend to balance the new situation.
At horizontal flight similar things happen.
The equilibrium is anything but stationary, as when a man is driving a bicycle wherein the center of gravity most of the time is not above the “base” (support base?), but it moves outside it. The bicycler continuously “feels and counteract to correct”.
Similarly pilot’s brain and body continuously “feel and counteract to correct”
Take the Portable Flyer together with the torso /chest of the pilot as a rigid body (the “fuselage” in the following), with the head, the waist, the hips, the shoulders, the arms and the legs hinged (directly or indirectly) from the “fuselage”.
The thrust force passes near the “overall center of gravity” of the assembly (including the pilot and the Portable Flyer).
By displacing his head and limbs relative to the “fuselage”, the pilot displaces the position of the overall center of gravity (always relative to the “fuselage”). This is how the “weight displacement control” works.
By changing the inclination of his head, hands and feet (all being inside the downwash from the propellers) the pilot deflects / restreams a part of the downwash. This is the aerodynamic control.
Wearing a wingsuit and flying horizontally at high speed, the pilot uses his/her legs to control the lift at the back side of his body. If he feels a “nose down” coming, the pilot reduces the angle (or the surface) of the part of the wingsuit which is between his legs.
At hovering, and in order to rotate about the vertical axis, the pilot uses his hands and or legs to deflect asymmetrically the high-speed downwards moving air stream, creating a pair of forces (moment) that spins him about his long axis (to make the same in the GEN-H4, they use an electrically controlled differential to increase slightly the revs of the one (fixed pitch) rotor and to decrease slightly the revs of the other “fixed pitch” rotor).
As regards the control of the flight,
the only difference from Mayman’s JetPack architecture wherein the center of gravity of the engines is, more or less, at the center of gravity of the pilot,
and from Zapata’s JetPack architecture wherein the weight of the engines is beneath the feet of the pilot (i.e. away from pilot's center of gravity),
is that the weight of the engines of the Portable Flyer is above the head of the pilot.
In all three cases the thrust force passes near the “overall center of gravity”, and the equilibrium is dynamic (feel counteract and correct).
“Your hands and feet controls, flying freely in the airstream while hanging from the motor unit, will not generate controlling forces and, as they are not in any way aerodynamic, will provide random control inputs meaning the pilot will have no ability to finely (if at all) control this machine.”
Please see the video of Yves Rossy flying above Dubai (in my last post).
The control of his flight is as fine as it gets. It is a perfect control.
Please see how he flies upside down and how he rolls back (from 2:49 to 2:53 in the video).
His Delta Wing is fixed (no flaps, no ailerons) and is secured on his back (with the four jet turbines fixed onto the Delta wing).
With only an altimeter and timer, Rossy uses his skin and ears as airspeed indicators.
"You feel very well, you feel the pressure," Rossy says, "you just have to wake up these senses. Inside an airplane we delegate that to instruments. So we are not awake with our body."
As Rossy says :
"I am the fuselage, and the steering controls are my hands, head and legs".
In order Rossy to control his flight by his head / limbs, he needs a minimum velocity (say, 100mph) relative to the surrounding air.
Instead, the head and limbs of the Portable Flyer pilot are from the very begining (take off) to the end of the flight (landing) inside the high speed downwash of the rotors.
Without the aerodynamic control, the Portable Flyer pilot should be an "acrobat" like Zapata.