The stability of the Portable Flyer at take-off, hovering and cruising is dynamic; it is similar to the “dynamic” stability during walking, wherein the brain “feels” (mainly by the otoliths and the eyes) and responds by commanding the various muscles to expand or contract.
At take-off / hovering / cruising / landing the brain of the pilot of the Portable Flyer “feels” (otoliths, eyes, ears and skin) and responds by continuously / dynamically re-vectoring the thrust (say, by bending the spine and the shoulders (whereon the engines / propellers are fastened) at various directions relative to the rest body). Without zero gyroscopic rigidity it would be from difficult to impossible.
But this is not the only way to control his flight; the pilot can, alternatively, use his head and limbs as ailerons (just like Yves Rossy) to deflect the fast air stream wherein his body is.
Dynamic stability means: the brain works without breaks, feeling and adjusting and controlling and commanding and correcting.
The same is the case during a walk: if you “switch off” the “brain” for just a second (faint), you collapse.
Standing “nose-up” on the ground, the XFV-1 and the XFY-1 remind the Portable Flyer.
An airplane cannot have the legs, feet, arms, hands, head and torso of the pilot of the Portable Flyer or of Yves Rossy. This makes it necessary to add to the fuselage of the airplane dummy limbs and flaps and rudders for its control.
Open the youtube video https://youtu.be/EABQ6cKzxaQ Go to 1:03 (vertical take-off and then transition to horizontal cruise of the XFY-1) then go to 2:30 (vertical landing; look at the ailerons, the only control system, and how they play), then go to 3:43 (XFV-1, transition from hovering to cruising; look at the leaning angles it achieves before gathering a significant horizontal speed).
The pilot of the PORTABLE FLYER has a similar aerodynamic control: he can use his legs, arms, head as the pilots of the XFV-1 / XFY-1 use the flaps / ailerons.
But the pilot of the PORTABLE FLYER has additional control means, too. He can bend his spine to redirect the “line of the thrust” relative to the center of gravity. He can also re-arrange his legs, arms displacing his center of gravity. And the pilot, who is in the open air, is 80% of the total gross weight and is “flexible”.
@manolis Manolis, you write: In the PORTABLE FLYER design there is, among others, “pendulum effect”, with the pivot (or gimbal joint) being near the middle of the thoracic spine (the “line of thrust” can swing about said pivot, or equivalently, the lower body of the pilot can swing about said pivot).
It think there is a misunderstanding in terminology.
I stated that if there is no tilting of the propellers relative to the aircraft, then there is no pendulum effect.
But your 'swinging' is the same as my 'tilting' , so the effect can exist. The 'point' of thrust is now at the pivot.
You've used only the red vertical component of the thrust for your demo. You need to account for the horizontal green one also.
You'll see that the moment the green one generates about the cg cancels the moment coming from the red. The total thrust vector therefore passes directly through the cg and there is no pendulum effect.
(Not for a fixed propeller that doesn't swing or tilt relative to the rest of the aircraft, anyway)
go and make something HOVER in the air at this angle and post the video. Wont happen - before you start gaining a few knots in forward speed - the correcting moment will have dropped the operator to vertical Do you really think it will stay in that orientation - No. The green force does NOT cause an equivalent but opposite moment in this situation. as I stated this ONLY occurs once drag is significant enough to allow for such a moment to exist. You wont be able to post a video because its not possible - the only video you will ever find showing this orientation, (in equilibrium) is with the required forward speed to cause enough drag to allow for the moment to exist.
@ExpAir Oh I agree with the you, the system in your diagram is not in equilibrium. It is accelerating to the left (because of the green horizontal force).
But there is nothing causing it to pendulum.
(… ignoring any subsequent aerodynamic-drag effects)
The motors look very potent No hassle with powerplant. Unfortunately the name isn't great for marketing purposes - or maybe it is - memorable But the wing layout and cabin shape. It seems very tight and compact - unnecessarily so - since the wings dictate overall size - they could have used a bit more cabin space. Looks claustrophobic. But the biggest hassle I have is that the wing layout doesn't lend towards stability at speed. I also wonder if a longer chord would have been much better - much better lift. So far it just looks like a low speed device or needing active stabilisation all the way.
and Another question .... if you were a large enough company to sponsor or fund some of the Top10 phase 1 winners - do you think you would be convinced by a document and some drawings? If I was going to consider funding, I would require an RC demonstrator - large scale - maybe 1/3 or half scale. It will be very interesting to see what development actually takes place, but we will not see this. All we will see is minimal photos of the phase 2 winners - was it 4 winners or 2?
So, when the pilot of the PORTABLE FLYER “locks” his spine / shoulders immovable, then there is no pendulum effect, and when he uses his spine – shoulders as a built-in gimbal joint / pivot, then there is pendulum effect.
Hello ExpAir
You keep on refusing the maths / physics laws. You also keep on asking for scale prototypes and videos to check this or that theory.
Come on.
I already posted the https://youtu.be/EABQ6cKzxaQ video wherein they happen all these you can’t accept can happen.
For instance, you can see leaning angles near 90 degrees at very low horizontal speeds.
Worth to note here: when an aircraft like the XFY-1 leans, the requirement for a, more or less, constant vertical component of the thrust (it takes the total weight) results in an increased with the leaning angle horizontal component of the thrust, and this inevitably accelerates horizontally the aircraft.
The only control system of the XFY-1 is the four ailerons at the bottom of the “standing” (nose-up pose) aircraft. At take-off and landing these ailerons are so close to the ground that the air-stream generated by the contra-rotating propellers (some 10 meters above the ground) is quite difficult to reach the ailerons. However the pilot still achieves to keep control.
The extreme leaning angles of the XFY-1 simply prove that your analysis and calculations are wrong. Open your mind and read again the previous posts; you will learn new things; like, for instance, what are two “equivalent force systems”, what “line of thrust” is, etc.
In comparison to the XFY-1, the pilot of the PORTABLE FLYER at take-off and landing can use not only his legs / arms as ailerons, but he also can use his spine / shoulders to redirect the “thrust”, achieving a better / stricter control over his flight as compared to the XFY-1 (in the XFY-1 the rotation axis of the contra-rotating propellers is fixed on the aircraft).
ExpAir, from your nick name (Expert of the Air) I suppose you have qualifications over aerodynamics, flying, mechanics etc.
I guess you could be a mentor of GoFly, or a Judge of the GoFly contest.
7.4. Risks 1) The judges to not value the importance of the lighter weight for a flying device. 2) The judges to not value the importance of a longer range and of a higher speed, especially at adverse weather conditions. 3) The judges to not appreciate the simplicity, the instinctive control and the benefit - cost ratio.
End of Quote.
If I were writing today the “Risks”, I would add:
4) The biggest risk is the judges to understand nothing about how the PORTABLE FLYER will fly, and to understand nothing about how the PORTABLE FLYER is controlled (i.e. about the dynamics and about the aerodynamics of the PORTABLE FLYER).
This is why I keep on asking to see the scoring / justification for my submission for the GoFly Phase I.
Manolis haha - Expert of the air, no. The name is a composite of "Experimental Aircraft", and no - I'm just an enthusiast, but I can mentor you for $150 an hour if you like ..... and if you need maths included - $300/hour. Refusing the maths - hahaha. You think your device is the same as the XFY-1 ? You think that because the XFY-1 can move to a cruise angle of about 70 or 80 degrees, that you can as well ..... Im not sure if you are pulling my leg or serious. Yes the XFY-1 can do it. I never said anything about the XFV-1. I said your portable flyer cannot, and to be honest I'm surprised that you think the portable flyer and XFV-1 will have the same behaviour. But don't convince me. Convince possible investors in the merits.
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