The autogyro as flying car (in 4 parts)

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Jstorrshall

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In recent years there has been an increasing demand for an airplane suited to the needs of the private owner. Without going into a discussion of the problem it may be said that such an airplane should be capable of descending along a steep path at such a low rate of speed that it will be unnecessary for the pilot to alter the direction of the flight path or the speed when near the ground in order to make a satisfactory landing. --Charles Zimmerman, N.A.C.A, 1932

A series of speculations -- comments appreciated!

https://wimflyc.blogspot.com/2018/10/the-autogyro-as-flying-car-part-i.html
https://wimflyc.blogspot.com/2018/10/the-autogyro-as-flying-car-part-ii.html
https://wimflyc.blogspot.com/2018/10/the-autogyro-as-flying-car-part-iii.html
https://wimflyc.blogspot.com/2018/10/the-autogyro-as-flying-car-part-iv.html
 

BBerson

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Using cell towers as control centers is a good idea. I am not so sure about autogyro acceptability in neighborhoods.
 

Jstorrshall

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Quite right -- but remember that in the early days of the automobile, there was such a reaction that states passed laws requiring a man with a red flag to precede any car on the public roads.
 

oriol

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Jstorrshall,

Just my view but I do not think that the revolution of flying cars is going to happen thanks particularly to the autogyro config or any other configuration in particular (canard, stol...) but the overall performances/trade offs of both the terrestrial and air capabilities. Particularly its operational cost versus other existing conventional transportation alternatives.

Flying cars have been the subject of extensive debate in this forum. I do not think the discussion is going to be reactivated again unless someone puts a proof of concept working prototype on the table.


Oriol
 
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Jstorrshall

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I won't bore readers here with the details, but if you want my observations on those questions you can find them at great length in my book,
Where is My Flying Car?

amazon https://www.amazon.com/dp/B07F6SD34R
an overview http://wimflyc.blogspot.com/p/where-is-my-fly8ing.html

Any discussion of flying cars will involve a lot of economics, regulation, and speculations on future technology, none of which is necessarily of interest to people who just want to build their own airplanes. On the other hand, electric-assisted quadrotor autogyros are something I'm fairly sure you could build as an ultralight.
 

rotax618

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Gyros are great, but you could get better performance, efficiency and flying characteristics by using a circular wing of less than the rotor disk diameter.
 

Jstorrshall

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Gyros are great, but you could get better performance, efficiency and flying characteristics by using a circular wing of less than the rotor disk diameter.
It's a tradeoff, and cruise performance is what you're giving away. What you're getting is lack of stall, enormously better (and safer) low-speed low-altitude maneuverability, especially in high winds, and an order of magnitude less runway necessary.

Oh, and parking. You could put 4 gyros in a T-hangar, but you couldn't fit even one aircraft with a 25-foot circular wing.
 

BJC

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.. Any discussion of flying cars will involve a lot of economics, regulation, and speculations on future technology, none of which is necessarily of interest to people who just want to build their own airplanes.
What seems to be missing is a realistic market survey. Pilots, and wanna be pilots, that I know view the (mythical) flying car as an oddity, not something that they would spend money on.
On the other hand, electric-assisted quadrotor autogyros are something I'm fairly sure you could build as an ultralight.
Why a quadrotor autogyro? Isn’t a single, long, rotor, with its large disc area/low disc loading, much more efficient?

There have been/are ultralight autogyros.


BJC
 

Jstorrshall

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What seems to be missing is a realistic market survey. Pilots, and wanna be pilots, that I know view the (mythical) flying car as an oddity, not something that they would spend money on. Why a quadrotor autogyro? Isn’t a single, long, rotor, with its large disc area/low disc loading, much more efficient?

There have been/are ultralight autogyros.
BJC
Yes, indeed! and that tells us something important: the gyro can be simple and inexpensive to build. It's a local optimum in design space. But you pay for that in controllability.

Here's how I described it in the post:
Taking off in a fixed-wing airplane is fairly easy; you shove the throttle to full power and steer in a straight line, and when the airspeed indicator says you're going fast enough, pull gently back on the yoke and away you go.

In a gyro, not so much. First, line up on the runway and push the stick full forward. Then, holding the brakes, move the throttle up to about 2000 RPM, or the engine will stall when you do the next part. Release the rotor brake (wheel brakes still on) and engage the pre-rotator. You have to slowly edge the throttle up as the rotor accelerates, until it reaches 200 RPM. Now, in quick succession, release the wheel brakes, pull the stick full back, advance the throttle up to about 4000, and steer straight down the runway. As you accelerate, the relative wind will bring the rotor up to about 400 RPM. This enough to begin generating lift, which pulls you up onto your back wheels, doing a wheelie down the runway. You must accommodate this instantly with the stick; otherwise the angle change of the rotor shaft with the wheelie will tilt the rotor too far back and pull you over backwards.
Congratulations! you have now formed a wing. Still balancing on your back wheels, use it to take off. Continue accelerating down the runway, noting that the torque from the propeller will be trying hard to make you turn left; counteract this with pressure on the right rudder pedal.
rotorflow.jpg

The best way to visualize the rotor disc as a wing is to see that it induces the same lift-producing circulation patterns as a solid wing, but notice that the airflow can go through the disc. As you see, the flow is coming up through the front and going down through the back part of the disc. This pushes up in front and down in back; but by the magic of gyroscopic precession, it tries to tilt to the right, so push the stick to the left to counteract it.

Now the quadrotor is also a local optimum in design space -- look at how many there are. With a quadrotor, you don't have to worry that every maneuver is going to turn your craft into a pendulum, and leave you trying to counter the resulting oscillations. You don't get the extreme pitch excursions a gyro does even in normal operations. Combine them and maybe, just maybe, you could get something that is stable, agile, and controllable at the same time.
 

BJC

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What seems to be missing is a realistic market survey. Pilots, and wanna be pilots, that I know view the (mythical) flying car as an oddity, not something that they would spend money on. Why a quadrotor autogyro? Isn’t a single, long, rotor, with its large disc area/low disc loading, much more efficient?

There have been/are ultralight autogyros.


BJC
Yes, indeed! and that tells us something important: the gyro can be simple and inexpensive to build. It's a local optimum in design space. But you pay for that in controllability.

Here's how I described it in the post:
Taking off in a fixed-wing airplane is fairly easy; you shove the throttle to full power and steer in a straight line, and when the airspeed indicator says you're going fast enough, pull gently back on the yoke and away you go.

In a gyro, not so much. First, line up on the runway and push the stick full forward. Then, holding the brakes, move the throttle up to about 2000 RPM, or the engine will stall when you do the next part. Release the rotor brake (wheel brakes still on) and engage the pre-rotator. You have to slowly edge the throttle up as the rotor accelerates, until it reaches 200 RPM. Now, in quick succession, release the wheel brakes, pull the stick full back, advance the throttle up to about 4000, and steer straight down the runway. As you accelerate, the relative wind will bring the rotor up to about 400 RPM. This enough to begin generating lift, which pulls you up onto your back wheels, doing a wheelie down the runway. You must accommodate this instantly with the stick; otherwise the angle change of the rotor shaft with the wheelie will tilt the rotor too far back and pull you over backwards.
Congratulations! you have now formed a wing. Still balancing on your back wheels, use it to take off. Continue accelerating down the runway, noting that the torque from the propeller will be trying hard to make you turn left; counteract this with pressure on the right rudder pedal.
View attachment 75017

The best way to visualize the rotor disc as a wing is to see that it induces the same lift-producing circulation patterns as a solid wing, but notice that the airflow can go through the disc. As you see, the flow is coming up through the front and going down through the back part of the disc. This pushes up in front and down in back; but by the magic of gyroscopic precession, it tries to tilt to the right, so push the stick to the left to counteract it.

Now the quadrotor is also a local optimum in design space -- look at how many there are. With a quadrotor, you don't have to worry that every maneuver is going to turn your craft into a pendulum, and leave you trying to counter the resulting oscillations. You don't get the extreme pitch excursions a gyro does even in normal operations. Combine them and maybe, just maybe, you could get something that is stable, agile, and controllable at the same time.
Please comment on:

Market survey for a flying car?

Quadrotor autogyro?


BJC
 

Jstorrshall

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Please comment on:

Market survey for a flying car?

Quadrotor autogyro?

BJC
I doubt a market survey would tell you much, because the average public doesn't know enough about it to have a better opinion than random. You'd have to start having some actual flying cars around and then people would begin to want to know something about them.

There are two extremely different approaches to a flying car, roadable airplane and VTOL. Here's a simple question: what does the demand curve for helicopters look like? That's your entry-level VTOL. Travel theory tells us that the value of a heli is about 2 and a half the value of a car (purely for travelling; there are other things a heli is good for that travel theory doesn't capture).
Turns out that the overhead time of having to go to the airport just about kills the value of a roadable. So a flying car that anybody would pay a significant amount for, will have to fly under rotorcraft rules in the foreseeable future.
But if you can build a rotorcraft for under say $100k, there is a reasonable argument to be made that people would be willing to pay for it.

As far as a quadrotor gyro is concerned, it's just one of many possibilities, but one that seems to capture aspects of two local optima in design space. The key would be partially powering the rotors, with a direct drive motor right on the rotor hub. Use Bensen style teeter hubs so you're still less complex than a heli even though you have 4 of them. You can't afford enough power to make it actually VTOL, but you can drastically shorten TO and landing distance.
 
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