F1technical.net

Posted: **29 Nov 2014, 07:49**

Agreed G-G, & while Ti was largely reserved for the likes of CIA 'Blackbirds' & BSA Works Comp Dept's way back then..

Now, with a well fettled 2-stroke mill - such as designed by our talented contributors here, it'd have to be a goer..

Posted: **29 Nov 2014, 08:16**

The principles behind VTOL aircraft have been well established, and it a basic fact that a small diameter fixed pitch rotor system operating at high speed is far less efficient at producing lift for a given amount of power than a large rotor system operating at low speed. Consider that the F-35B needs over 30,000hp to produce just 20,000lbf of thrust from its small diameter, high speed lift fan.

Posted: **29 Nov 2014, 08:52**

OTOH a smaller prop is far better at high speed horizontal flight, so VTOL fixed wing machines like the Osprey and Manolis' portable flyer have to compromise on rotor diameter.

Posted: **29 Nov 2014, 09:30**

Again r-r, it seems that you may be a bit too ready to make certain declarations sans full appraisal of the facts..
Of course..
.. if in the - albeit seemingly unlikely- event..
.. that you can provide some authoritative/scholarly citation to back your opinions expressed above..

I guess Manolis will.. ( akin to the "Bumblebee" case) ..rightfully claim that he is going to do empirical tests..
..based on well established aero-tech principles.. naturally.. & show you & other naysayers what's what..

We'll see..

Certainly 2-stroke power density has the performance for VTOL..

I have a decades old engineering text which examines the published power curves for a Kawasaki 750/3,
- the then gun 'Superbike' & the review concluded with some surprise & admiration that this 2-stroke had
such an impressive power to weight ratio - that it could go up vertically at ~40mph - if traction was available..

Posted: **29 Nov 2014, 10:20**

J.A.W. wrote:I have a decades old engineering text which examines the published power curves for a Kawasaki 750/3,
- the then gun 'Superbike' & the review concluded with some surprise & admiration that this 2-stroke had
such an impressive power to weight ratio - that it could go up vertically at ~40mph - if traction was available..

Ahh traction. That is where the large diameter rotor has the advantage - much better traction.

Yes, impressive, I assume that is the mass of the whole bike, not just the engine.

Posted: **29 Nov 2014, 10:50**

Including the rider.. in fact.. .. & based on the extrapolation of the gearing/torque curves vs weight..

See here for V1.. attempt..

https://www.youtube.com/watch?v=1N5rm0glYwY

Posted: **29 Nov 2014, 13:04**

yes of course jetborne vtol is very (Froude) inefficient, as momentum is conserved but kinetic energy is not conserved
the thrust (lift) is proportional to the change in momentum, so the bigger rotor is more efficient in the hover
(the part of the engine power that gave the KE is just wasted)

the helicopter pilot learns to do rolling takeoffs using partial power, great fun and incidentally improving Froude efficiency
and a bigger rotor has much more energy stored in its rotation, which can literally be vital in the power failure situation

officially there is no such thing as an autogyro, it is a gyrocopter
W Cdr Wallis said that one should fly only aeroplanes, or only helicopters, or only gyrocopters - I know what he meant
he also found using a 'cheep and cheerful' Mculloch engine (from a target drone) that the magneto always failed after a few minutes
because of the loss of magnetism when warm in the 'cheap and cheerful' magneto installed as fit for purpose

the (UK) CAA seemed to dislike 2 strokes because of their inconsistent behaviour at reduced power
btw the 750 Kawasaki would beat anything from 35 mph in top gear

Posted: **29 Nov 2014, 14:02**

riff_raff wrote:The principles behind VTOL aircraft have been well established, and it a basic fact that a small diameter fixed pitch rotor system operating at high speed is far less efficient at producing lift for a given amount of power than a large rotor system operating at low speed. Consider that the F-35B needs over 30,000hp to produce just 20,000lbf of thrust from its small diameter, high speed lift fan.

Rolls Royce refuse to build engines for the F35 because of this,
The Forward turbine also drives the forward lift fan mechanically on the F35.
That is why it is limited to 9 vertical take offs before a complete engine strip down.
Not exactly a 'safe' operating reliability.
The concept of supersonic VTOL fixed wing was and is fundamentally flawed.
To heavy, to thirsty, low payload and easily out performed by any conventional aircraft of the same generation.
This was simply a cash cow for Lockheed not a development of our Harrier in any shape or form.
It has left Britain with two through deck carriers with no cats or angled flight decks incapable of operating any other fixed wing aircraft than the F35 Dog and helicopters, it is the biggest covered up scandal since WW2.

Light helicopters have very limited range and lift capability an electric version has yet to be built with more than ten minutes flight duration and no payload capability, IC version are only slightly better and all are very difficult to get into safe autorotation. They are all without exception dangerous and I know this from my own flight experience.
There are one or two twin seat helicopters of light construction that just meet flight safety but only just.

Light autogyros by comparison can have a better performance in most aspects than any FULL sized helicopter.
Better range, speed, handling, safety. payload capability (relative to size) and much more.
Autogyros only lack VTOL which can be added with jump start, jet tip drive or a light electric partial drive.

Please look at the link I posted, this aircraft was fully developed for military and civil tasking.
We undertook ship landings on small patrol vessels of 30ft, full air to ground missile trials against tank armour and rapid deployment exercises from the back of C130s )flying on operation from deployment inside two minutes.
I still cannot post of its operational use as a two seater before the Berlin wall came down or of other covert operations it still undertakes.
Please stop posting about impractical light helicopters.

http://www.kate.aviators.net/gyro2.htm

Posted: **29 Nov 2014, 14:16**

riff_raff wrote:The principles behind VTOL aircraft have been well established, and it a basic fact that a small diameter fixed pitch rotor system operating at high speed is far less efficient at producing lift for a given amount of power than a large rotor system operating at low speed. Consider that the F-35B needs over 30,000hp to produce just 20,000lbf of thrust from its small diameter, high speed lift fan.

100% accurate

Maybe some people get confused with some aircrafts using not so big rotors because once you get enough power you can sacrifice thrust to achieve a higher top speed using a smaller prop spinning faster, but if your only concern is thrust/lift, a bigger prop spinning slower is always much more efficient

I can´t provide theoretical data, but real life experience with RC 3D planes is unquestionable

I´ve also designed my own drone (an octocopter) and I´ve tested some dozens of props with same results: brand/design of prop may affect, but never as much as diameter. But since power is more than enough even with smaller props, I did sacrifize efficiency for a safer configuration using 8 motors with not that big props, instead of using 4 motors with bigger props than would provide better efficiency. I could have chosen 8 big props, but then the total size of the aircraft would be too big for transportation.

So bigger props are always better for thrust/lift, but if you have enough power, you can sacrifize efficiency for different reasons. In my case size and safety (redundacy), with VTOL aircrafs it´s top speed.

Posted: **29 Nov 2014, 14:20**

gruntguru wrote:OTOH a smaller prop is far better at high speed horizontal flight, so VTOL fixed wing machines like the Osprey and Manolis' portable flyer have to compromise on rotor diameter.

An autogyro has a small diameter prop and a large main rotor so no compromise.
Although I have worked on a development to concertina the main rotor with increasing airspeed to reduce drag by a huge amount and increase speed close to sonic.
You cannot do this with a powered helicopter rotor.

The limit to speed for any rotor or prop equipped aircraft is rotor and prop tip speed. You have to avoid them reaching sonic speeds. This is a fixed limit for a powered rotor/helicopter, it is not for an autogyro with an unpowered rotor.
The rotor speed can be reduced and the rotor diameter reduced as speed increases maintaining balanced lift and preventing sonic tip speed. A turbofan powered autogyro with this rotor addition could reach very high sub sonic airspeeds.

The fully proven and in service Fairey Rotodyne had two turboprops of course and a modern version would have by-pass turbofans.
See simulation.

https://www.youtube.com/watch?v=VFk5Y_F-dwg

Far far better than any silly Osprey or even Chinook and C130.

Posted: **29 Nov 2014, 14:51**

Tommy Cooker wrote.
officially there is no such thing as an autogyro, it is a gyrocopter
W Cdr Wallis said that one should fly only aeroplanes, or only helicopters, or only gyrocopters - I know what he meant
he also found using a 'cheep and cheerful' Mculloch engine (from a target drone) that the magneto always failed after a few minutes
because of the loss of magnetism when warm in the 'cheap and cheerful' magneto installed as fit for purpose

Ken was simply explaining that there are three distinct forms of flight if you exclude lighter than air.
Kens aircraft were all called autogyros and it is the word he always used to describe this form of flight.
Gyrocopter is acceptable but does not really explain the rotors capability to produce lift 'automatically' when exposed to a relative moving air stream. Copter sounds more like 'helicopter' which Ken and I were always quick to point out the distinction.
It is not important as a word semantic issue but VERY important when many people STILL do not understand the huge difference.

Officially there is NO ONE at the CAA who has a clue how an 'Autogyro' works and there are STILL NO official definitions on autogyro flight at the CAA.
Ken and I were even asked on one occasion by the CAA (and I still have the communication) to produce a definition for autogyro flight for the CAA at our expense some four million pounds estimated.
That is the absolute truth Tommy.
So sad how low the British aviation industry has been driven to by outside corrupt interest.

Posted: **29 Nov 2014, 15:05**

autogyro wrote:
riff_raff wrote:The principles behind VTOL aircraft have been well established, and it a basic fact that a small diameter fixed pitch rotor system operating at high speed is far less efficient at producing lift for a given amount of power than a large rotor system operating at low speed. Consider that the F-35B needs over 30,000hp to produce just 20,000lbf of thrust from its small diameter, high speed lift fan.
Rolls Royce refuse to build engines for the F35 because of this,
The Forward turbine also drives the forward lift fan mechanically on the F35.
That is why it is limited to 9 vertical take offs before a complete engine strip down.
Not exactly a 'safe' operating reliability.
The concept of supersonic VTOL fixed wing was and is fundamentally flawed.
To heavy, to thirsty, low payload and easily out performed by any conventional aircraft of the same generation.
This was simply a cash cow for Lockheed not a development of our Harrier in any shape or form.
It has left Britain with two through deck carriers with no cats or angled flight decks incapable of operating any other fixed wing aircraft than the F35 Dog and helicopters, it is the biggest covered up scandal since WW2.
Argentina has just purchased 24 Saab Grippen from Sweden and after 2015 Britian will lose the Falklands mark my words.

Light helicopters have very limited range and lift capability an electric version has yet to be built with more than ten minutes flight duration and no payload capability, IC version are only slightly better and all are very difficult to get into safe autorotation. They are all without exception dangerous and I know this from my own flight experience.
There are one or two twin seat helicopters of light construction that just meet flight safety but only just.

Light autogyros by comparison can have a better performance in most aspects than any FULL sized helicopter.
Better range, speed, handling, safety. payload capability (relative to size) and much more.
Autogyros only lack VTOL which can be added with jump start, jet tip drive or a light electric partial drive.

Please look at the link I posted, this aircraft was fully developed for military and civil tasking.
We undertook ship landings on small patrol vessels of 30ft, full air to ground missile trials against tank armour and rapid deployment exercises from the back of C130s )flying on operation from deployment inside two minutes.
I still cannot post of its operational use as a two seater before the Berlin wall came down or of other covert operations it still undertakes.
Please stop posting about impractical light helicopters.

http://www.kate.aviators.net/gyro2.htm

Posted: **30 Nov 2014, 03:04**

How about a bit of twostroke discussion.

Posted: **30 Nov 2014, 09:21**

Hello.

The evolution from the Chinook to the Osprey shows the differences.

The second focuses on the horizontal flight at high speeds, keeping the ability for vertical take-off and landing. Compare the fuel efficiency, the top speed and the range of the Chinook with those of the Osprey.

Chinook (Boeing CH-47):
a pair of counter-rotating propellers of 18.3m diameter each,
a pair of engines providing 4,733 bhp each,
a maximum take-off weight of 22,680Kp,
a range of 741Km,
a maximum speed of 315Km/h.

Osprey (Bell Boeing V22):
a pair of counter-rotating propellers of 11.6m diameter each,
a pair of engines providing 6,150 bhp each,
a maximum take-off weight of 27,400Kp,
a range of 1,627Km,
a maximum speed of 509Km/h.

More than double range, almost double maximum speed, much smaller propellers and heavier "propeller disk loading" for the Osprey.

The Osprey V22 cannot auto-rotate. If both engines fail at small horizontal speed and low height, the Osprey cannot land safely.
They could keep the autorotation capability in expense of the horizontal flight, of the range, of the maximum speed, of the "mileage".
But what they wanted was an airplane having the capability to take-off and land vertically.

The PatATi Portable Flyer (25Kp total weight with the fuel, 100Kp with the pilot) can be seen as a scale-down Osprey V22. If combined with a wingsuit, it allows high-speed horizontal flights, low fuel consumption, long range and capability for vertical take-off and landing.

You can also see the PatATi Portable Flyer as a lightweight Peroxide JetPack (enjoy the youtube video at https://m.youtube.com/watch?v=E81KQ7u3-7s ), having 1/3 of the weight of the JetPack, and being rid of the limitations that make the peroxide JetPack just an expensive toy (among others: less than 30 seconds total flying time).

Gyroplanes have their own limitations. I don't think there is a conspiracy to keep gyroplanes out of the game. Their characteristics limit their use.

And since the thread is about the two-stroke engines, the PatATi Opposed Piston has several innovations / unique characteristics.
I can explain them if there is interest.

Thanks
Manolis Pattakos

Posted: **30 Nov 2014, 09:56**

Def' interested in your 2-stroke tech Manolis, for sure..

I am curious about the seemingly 'naked' ports shown on your flyer..
So - what about the gas ducting?

No visible means of support for..

Inlet air filtration & quiet yet - efficient intake - is it direct fuel injected?
Exhaust, pulse-tuned & silencing/disposal of noxious fumes?

Is discrete oil injection used?

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