2 stroke thread (with occasional F1 relevance!)

[gruntguru]

It is not the lift of the flyer engine, it is the aerodynamic drag of the flyer engine that reduces the moment on the back / torso of the pilot.

Thanks Manolis, I was missing that important distinction. I still see a problem however. You do not know the direction of the drag vector. It is certainly not horizontal. Hopefully it is not along the thrust axis (due to airflow over the engine being predominantly influenced by the wash from the propellers.)

Regardless of the answer - the flyer will be more stable if the hinge point could be lower on the pilot's body. Why take the risk? Why not design the prototype for maximum stability and make it "less stable" after testing while the pilot is still alive?

I do not agree with everything Rodak says by the way. The flyer can be designed to fly successfully, controlled only by the attitude of the pilot's body.

[Rodak]

Hey Manolis, here's a good basic video about stability, it's really worth a watch. Math speaks louder than words.....do some calculations and see where your center of pressure and center of gravity are and how they will interact with the flexible control system you propose. The issue I have with your control system is that basically you are introducing many hinges because of flexible body joints and it is pretty much impossible to determine how they will interact. For example, if I hinge the engine of a Cessna just behind the motor mount, put a hinge in the center of the fuselage, and mounted the tail plane on a hinge what would happen when control forces were applied? This would not be a stable system, it would be impossible to predict moments, and that is the issue I see with your flyer, the inability to predict reactions let alone determine how the moments would be applied to affect the direction of your motor unit in this flexible system (and also the power required for high speed horizontal flight, which I think you are really underestimating). A previous post also mentioned the angle of attack of the propeller at, say, 45°, and the difference in incident angle of attack from leading/trailing blades and it's effect on lift, etc.

https://youtu.be/vhBgfQwg8SY

[manolis]

Hello Rodak.

You write:
“if I hinge the engine of a Cessna just behind the motor mount, put a hinge in the center of the fuselage, and mounted the tail plane on a hinge what would happen when control forces were applied? This would not be a stable system, it would be impossible to predict moments, and that is the issue I see with your flyer”


While the multi-hinge structure of an airplane would be a curse,
the multi-hinge structure of the human body is a blessing.

The difference is on the control of, and on the feedback from, the various hinged subsystems (head, limbs etc), i.e. on the ability of the central processing unit to adjust each of the hinged parts immediately and intuitively.

The
“feel and react to correct”
is the basis:
for flying a Portable Flyer,
for flying a Jet-Pack,
for bicycling,
for running,
even for just walking.

When a man is walking on the ground, the various sensors (eyes, otoliths, skin, etc) continuously feed the brain with information, and the brain, based on the feedback, commands the muscles (or “meat”), supported on the bones, to displace properly the “hinged” parts.


By the way,
the flying birds and bats are doing more than what the body of the Portable Flyer pilot is required to do during a flight:

• As the pilot, the brain of a bat (or a bird) controls its flight by commanding the various muscles to contract more or less (and so to displace the various hinged parts of its body relative to each other), and by adjusting – based on the feedback from the various sensors of the body - the next bunch of commands to the muscles.

• But contrary to the pilot, the body of a bat (or a bird) has another mission to perform: to generate the power required for the flight (i.e. the power required in order to make the necessary thrust / lift for the flight).

This mission (power generation) is performed by the engines / propellers of the Portable Flyer (or by the jet-turbines of Zapata, Mayman, Browing JetPacks), leaving the pilot free to deal only with the control of the flight.


Browning, who does fly vectoring, by his “hinged” arms, a good part of the thrust, and who is using his “hinged” legs as basic stabilizing mechanism, says:
“approaching this challenge of human flight leaning very heavily on that already pretty amazing machine (the human body) … there is one thing that’s missing, and that’s horsepower … we don’t have enough power versus our weight …”
and
“the brain and body is a quite awesome machine at being able to balance and control”


Yves Rossy / Jetman "flies with the grace of an eagle, and the subtle body movements he uses to maintain flight - and perform his loops, rolls, and other maneuvers - mimics a bird of prey".
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"


Here are some single-engine Portable Flyer early-designs:








As the application for the BOEING / GoFly competition (at https://www.pattakon.com/GoFly/index.html) writes:

The PORTABLE FLYER is like an extension of the human body providing the required power in a true neutral way.
The brain, the senses and the muscles do the rest.

Thanks
Manolis Pattakos

[Rodak]

The difference is on the control of, and on the feedback from, the various hinged subsystems (head, limbs etc), i.e. on the ability of the central processing unit to adjust each of the hinged parts immediately and intuitively.

Well, I'm certainly curious how a pilot learns that feedback; is this some automatic thing that is instinctive? While we are on the subject, why do you have (2) counter-rotating propellers? Why not just a single set or two propellers rotating in the opposite direction to counter torque? That would seem to be much lighter.

Seriously, did you look at the video I posted re stability? Can you show your stability calculations? Where is the Cp and the C.G.? How did you determine the Cp of the machine? I've been able to find some data re drag of a supine human, but have no data on the Cp or lift, especially at various angles of attack; the human body is not an aerodynamic wing. How does the angle of attack of the motor unit affect the Cp of the entire unit? Seems to me the built in flexibility means there will be lots of thrashing around and, hence, control issues.

A person I worked with used to spin all sorts of ideas about shooting some sort of balls of energy. Sounded pretty good until one asked for details and then it became verbiage. I'm suggesting you might spend some time analyzing this system and then build a model and spend some time in a wind tunnel instead of relying on anecdotal information. Just sayin'.

Edited to add: I would be curious to see how far down the framework of the flyer shown in your last picture extends. Is it down the the feet of the pilot? So that he might exert some control torque??? Also, it looks like those dog belts are abrading each other.

[manolis]

Hello Gruntguru.

You write:
“Regardless of the answer - the flyer will be more stable if the hinge point could be lower on the pilot's body. Why take the risk? Why not design the prototype for maximum stability and make it "less stable" after testing while the pilot is still alive?”


The other way is to make it as simple, as compact and as lightweight as possible, and if there is any “stability” issue, to proceed with the modification of the support of the engines on pilot’s body.

The typical with the prototypes is that you have never the patience to finish them before put them on the road (or on the sky?).


I remember when modifying the:
“two-valve-lift-profiles with hydraulic-control” Honda Civic 1600cc 16v VTEC
to:
“infinite-valve-lift-profiles with mechanical control” VVA-roller:





a lot of time was spent thinking for the best type and position / arrangement of a restoring spring for the gas pedal.
Then it turned out that the existing 32 valve-springs (2 per valve) in the cylinder head do the restoring of the gas pedal just fine.


By the way, the above roller-VVA together with the rod-VVA (which also started road tests semi-finished):





are the “father” and “grandfather” of the Desmodromic VVA (or DVVA):



Thanks
Manolis Pattakos

[manolis]

Hello Rodak.

You write:
"Seriously, did you look at the video I posted re stability? Can you show your stability calculations? Where is the Cp and the C.G.? How did you determine the Cp of the machine?"


I did open that video.

Do open the following one:



wherein Browning, six days ago, flies and brakes a world record.


Why he wears the "lower" orange-coloured suit?

Does he know where his center of gravity and his center of aerodynamic lift / drag / etc are?


Do you care where your center of gravity is, as you are walking?
Have you any issues / problems walking without knowing where your center of gravity is?


Likewise walking,
flying is a sequence of "feel and react to correct".

Thanks
Manolis Pattakos

[manolis]

Hello Rodak

You write:
“Well, I'm certainly curious how a pilot learns that feedback; is this some automatic thing that is instinctive?”


Think how you walk.
Walking is an instinctive dynamic process.
You don’t need to think carefully where exactly to put your right foot at your next step, or whether your center of gravity is a little offset, or whether the ground is not exactly horizontal, or whether the wind is strong, or …
The brain automatically “feels and reacts to correct”.


Yves Rossy (the JetMan) flies, as he claims, instinctively, like the birds.
After the initial training (tethered tests in controlled environment) the brain gets familiar with the dynamic process of flying, and responds “automatically”.
As Rossy says, he just turns his head towards the desirable direction, and his Delta Wing JetPack follows flying towards that direction.



You also write:
“While we are on the subject, why do you have (2) counter-rotating propellers? Why not just a single set or two propellers rotating in the opposite direction to counter torque? That would seem to be much lighter.”


The arrangement with the two independent pairs of counter-rotating propellers and the two independent engines is for safety, for compactness, for lightweight, etc.

All are explained at
https://www.pattakon.com/GoFly/DTR_1.pdf,
https://www.pattakon.com/pattakonPatTol.htm
and
https://www.pattakon.com/pattakonFly.htm

Read the above and if you still have questions let me know to explain.


For instance:

SAFETY (from the second link):

As the Osprey, the Portable Flyer is capable for "vertical take-off / landing (like a helicopter), and for high-speed long-distance high-mileage flights (like an airplane).

The malfunction of the one propulsion unit (due, for instance, to an engine failure, or to a rotor breakdown, or to a broken tooth-belt etc) is not fatal because the other (completely independent) propulsion unit, ALONE, is capable for the safe landing of the Portable Flyer.

In the Osprey V-22 the malfunction / collapse / breakdown of the one rotor may turn out fatal, especially during a vertical take-off or landing.

In comparison, the Portable Flyer with the two OPRE Tilting engines is safer.

The breakdown of a rotor of a propulsion unit is not fatal: the other propulsion unit of the Portable Flyer (comprising an engine and two counter-rotating rotors) enables a safe landing or, if necessary, the flight to the closest safe landing place.”


For instance:

Counter-rotating and contra-rotating propellers (from the first link above, from where the screen-shot is taken):

The left upper and the left lower propellers compose a pair of “contra rotating” propellers (the one driven by the right engine, the other driven by the left engine, both rotatably mounted on the same pipe).
The right propellers comprise another pair of “coaxial” contra-rotating propellers.
The two engines operate independently from each other and can run at different revs if desired (to optimize the overall thrust and mileage).
For instance, if the lower propellers are similar (same diameter, same pitch, same design etc) to the upper ones, the lower engine may run at different rpm to align its propellers with the different air stream they “see” as compared to the air stream the top propellers “see”.
The set of the four propellers can be regarded as two “contra rotating” sets of counter-rotating propellers. A common characteristic of both, of the contra-rotating propellers and of the counter-rotating propellers, is the higher thrust to power ratio.”



Thanks
Manolis Pattakos

[Rodak]

Walking is an instinctive dynamic process.

Walking is a learned process that takes a lot of practice; have you ever had children? One thing I can tell you about that flying suit is that the center of pressure is behind the center of gravity, leading to stability; look at that big empennage.

[manolis]

Hello Rodak.


Instinctive control and fast learning.

It takes no more than an hour from its egg hatching in order a baby-chicken to stand on its two feet, walking and running.

Bicycling is a dynamic process, too, and it takes a couple of hours, or so, to be learned by a child. After a few more hours of practicing, the child is bicycling instinctively.

Mayman says that after 3 hours of tethered tests-flights with their JetPack, the ordinary person is ready for the first free flights.


Center of gravity, support base and stability:



In the above video:

• For more than 50% of the time none of the two feet of the runner abuts on the ground (or say: for more than 50% of the time the runner flies?).
  For about 90% of the time the center of gravity of the runner is out of the support base (i.e. the runner’s footprints).

The runner actually rebounds (from foot to foot).

The equilibrium is dynamic:
the brain takes feedback from the body (eyes, otoliths, skin, etc) and locates instinctively the foot that is going to abut, and commands properly the muscles in order the body of the runner to take the “right” push from the ground.

it is not a static equilibrium. It is a step (by step) dynamic correction of an instability.

In comparison, the brain of the Portable Flyer pilot seems as having an job to perform.

For stability what is required is not a center of gravity above the support base, or under the aerodynamic lift, but a way to “feel and react to correct”.


In the video of a previous post wherein Browning breaks a world record, it seems his left leg fin got into the hot exhaust gas (the jet-turbine(s) at his back), and got fire.
With his hands / arms busy in holding and vectoring their four jet-turbines, Browing cannot deal with the fire.

By the way,
in order the fins of Browning to provide some aerodynamic forces, he needs to fly fast or very fast.

In comparison, the head and limbs (which all are free) of the Portable Flyer pilot are, from before the beginning to the end of the flight, into the fresh/cool high-speed downwash from the propellers, providing aerodynamic control.



As the ground “rebounds” the runner, the same way the downstream of the propellers “rebounds” the pilot.

Thanks
Manolis Pattakos

[Rodak]

Yep, okay Manolis. I give up.

[gruntguru]

More thoughts on the feasibility of using drag forces on the engine to support the engine in horizontal flight.
1. If the drag vector was vertically up and sufficient in magnitude to support the weight of the flyer engine assembly, how fast would the flyer be travelling? Answer. At the terminal velocity of the engine dropped from a great height - probably more than 200 km/hr.
2. Is the drag vector pointing vertically up? No, at best it is horizontal as shown in your diagram.
3. Horizontal is very optimistic. The air streaming past the engine is generated partly by the forward flight. This component is horizontal. It is also generated by wash from the propellers. This component is along the tilted axis and does not help support the weight of the flyer engine.

Considering the three points above I estimate the flyer will need to be travelling at 300 km/hr and with the axis angled significantly upwards if it is to support the weight of the engine.

[manolis]

Hello Gruntguru.

You write:
“The air streaming past the engine is generated partly by the forward flight. This component is horizontal.”

Agree


You also write:
“It is also generated by wash from the propellers.”

I think not.
It is an “internal” force.
The engines and the propellers are “secured” to each other.
The force generated on the engines by the wash from the propellers is equal and opposite to the reaction force acting on the propellers (which are rotatably mounted on the two “holed” pipes, which are secured on the sides of the engines, see the image “screen shot” fives posts ago).
Differently, a part of the thrust force T from the propellers is “cancelled” (consumed? taken?) internally by the engines which are inside the wash from the propellers.



The following image shows at its upper-right side the “fuselage”. It is the grey-colored assembly that includes the engines, the frame (side pipes and saddle) and the pilot’s upper torso (back, chest and shoulders). This assembly / fuselage is, more or less, a fixed / rigid body.



At the bottom-right side of the image they are shown (by light-brown color) all the “hinged” and “multi-hinged” parts (members) of the pilot; while the upper arms are directly hinged to the “fuselage” (as defined above), the lower arms and hands are “multi-hinged” as hinged to parts that are already hinged to the fuselage.


The question is:

What is gonna fall?

The engines and the upper torso, as a rigid body, will fall (or turn downwards) together, as a single rigid body.

The hinged parts (head, limbs, lower torso) also tend to “fall” (or turn) due to the moment of their weight about their respective hinge points.

Depending on their pose, the “parts / members / “fins” of the pilot provide some lift (not necessarily positive (i.e. upwards), but also negative if required) and drag. All these either with the pilot wearing a wing suit, or not.

If, at horizontal flight, pilot’s legs are completely horizontal (no lift), they balance with their weight the part of the moment from the engines not balanced by the “eccentric” horizontal aerodynamic drag on the engines.

If, at horizontal flight, the legs of the pilot are “leaning to the sky” (like the tail “horizontal stabilizers” of the airplanes, which provide negative lift for the sake of safety: to avoid an uncontrolled stall) they can provide additional aerodynamic moment that tends to turn the fuselage upwards.
Likewise what Rossy does flying above Dubai (video at page 178):



Here Rossy flying upside-down:




As pilot’s legs, similarly with pilot’s head and limbs: they can provide control reactions with their weight and aerodynamic.

The flexible human body, controlled by the human brain, can fly better than the bugs, bats and birds. As Rossy claims and does.

Thanks
Manolis Pattakos

[Tommy Cookers]

....the tail “horizontal stabilizers” of the airplanes, which provide negative lift for the sake of safety: to avoid an uncontrolled stall ...

...hinged parts ..limbs..tend to 'fall' due to moment of their weight about their respective hinged points ...

.... Rossy does flying above Dubai ....

the horizontal stabilisers aka tailplanes usually provide positive lift (in doing their stabilising job)

hinged parts don't 'fall' (relative to the PF) eg if/when the PF is on an excursion towards and even beyond 0 'g'

Rossy's flying machine has aerodynamic stability from its delta wing
btw that's what delta wings (generally) do - have an inherent 'tailplane effect'
the difficulty with deltas is getting enough control/trim authority - that's where Rossy's limbs are useful
and given a suitable (reflex) aerofoil even a straight planform wing is stable without a tailplane

[gruntguru]

Hello Gruntguru.The following image shows at its upper-right side the “fuselage”. It is the grey-colored assembly that includes the engines, the frame (side pipes and saddle) and the pilot’s upper torso (back, chest and shoulders). This assembly / fuselage is, more or less, a fixed / rigid body.

This statement suggests there is not a "hinge" point at the pilot's shoulders. If the flyer and pilot's torso form a somewhat rigid assembly, I am much relieved for the safety of your test pilot.

[manolis]

Hello Tommy Cookers

For a personal flyer the Delta Wing has some side effects, like its weight and the difficulty at landing.

In some cases one parachute is used for the landing of Rossy, while another parachute is used for the landing of the Delta Wing.

The most interesting is how efficiently and accurately Rossy "drives" / control his fixed Delta Wing only with his head and limbs weight and aerodynamic.

Thanks
Manolis Pattakos