Monday, May 26, 2008

Arc Wing Versus Planar Wing

In the June 2008 edition of Flying Magazine, noted aviation expert and writer Peter Garrison writes about the forces associated with airplane lift in a very interesting article titled "The Bernouilli Brigade". He discusses at length why the lift possible from a wing is less than one would think. Here is some of what he says:
"The pressure difference between upper and lower surfaces causes spillage at the tips - this is the reason for the tip vortex - and robs the wing of 5 to 10 percent of its theoretical lift. Another loss occurs at the center of the wing where the fuselage interrupts air flow. The imaginary portion of the wing that lies within the - reported wing area includes this hidden part - produces in reality, no lift. But changes in the pressure are gradual, not instantaneous, and so the effect of the fuselage is to produce a dip rather than a sharp-edged gap in the spanwise distribution of lift. Depending on the fraction of the wing that lies within the fuselage, another 10 or 15 percent of potential lift may be lost here."
He also refers to the losses from the tips of the non-spanwise flaps.

His article deals with the loss of lift of the straight or planar wing. At Aeromobile Inc., we think our arc wing obviates several of these losses. In my previous blog entry, called "A Wing that Really Lifts", I list all the reasons the arc wing has superior lift to the planar wing. Here I will just mention a few:
  1. The arc wing has inherent "winglets" and minimal tip vortices to reduce that 5 to 10 percent of lift of the straight wing.
  2. There is no fuselage interrupting the arc wing span. The fuselage is under the arc wing saving a additional 10 or 15 percent of wing lift.
  3. Taken together, the theoretical saving of the arc wing over the straight wing without the fuselage interrupting may be as much as 10 to 25 percent.

Thursday, May 22, 2008

A Wing That Really Lifts

I've talked about the Arc Wing VTOL airplane in a number of earlier posts. Today, I want to talk mostly just about the arc wing itself. No airplane today has a wing like it, and I feel it would have many advantages even for conventional take off and landing (CTOL) aircraft, as well as vertical take off and landing (VTOL) aircraft.

This photo shows just the shape of the arc wing:

And, this image shows the arc wing in combination with a dual rotating propeller and a flap at the back that would be used for VTOL operations:

What are its advantages of the arc wing? When combined with dual rotating propellers:

  1. The arc wing has inherent "winglets" and minimal tip vortices to reduce 5 to 10 percent of lift of the straight wing.
  2. There is no fuselage interrupting the arc wingspan. The fuselage is under the arc wing saving an additional 10 or 15 percent of wing lift.
  3. Taken together, the theoretical saving of the arc wing over the straight wing without the fuselage interrupting may be as much as 10 to 25 percent.
  4. The arc wing has greater lift, (L/D), for a given span than a straight wing.
  5. An airplane designed with the arc wing will have as shorter span for a given load factor.
  6. The arc wing stalls at 33 degrees angle of attack vs. the straight wing that stalls at 17 degrees, resulting in later stall and higher lift.
  7. Arc wing flaps are full span and without tip losses, inboard or outboard.
    The arc wing has positive pitch stability that removes the need for a horizontal empennage and the structural weight and drag thereof.
  8. The arc wing can assume any angle of attack and "freeze" at any angle of attack by moving the tip mounts fore and aft. We have a video that my son William D. Bertelsen narrates that shows the arc wing stability at any attack angle.

Friday, May 16, 2008

Propellers Forever!

In a May 13th story titled "Single engine turboprops prosper", Kate Sarsfield of Flight International makes the point "The single-engined turboprop sector is riding high. Continued hikes in the price of oil worldwide, coupled with their unrivalled operational flexibility, are pushing up demand for these versatile, efficient propeller-driven aircraft.". In another story on May 15th, also from Flight International, writer Mary Kirby, says in her piece called "Embraer resumes analysis of turboprops" "Developing a new commercial turboprop is under renewed analysis at Embraer, and could provide an eventual substitution for the Brazilian manufacturer’s small regional jets."

Why is it that propellers are more efficient than straight jet engines?

1. Props move a larger volume of air more slowly that jets. An illustration is that the 40 foot rotor of the helicopter can lift more with less horse power than can smaller props.

2. Turbo props have larger diameters than jets, and move more air more slowly and more efficiently.

It conveniently happens our Arc Wing VTOL airplane not only uses a large propeller, but it is a dual rotating propeller, which is even more efficient than a single propeller, by a factor of 8%. Dual rotating props have a straight slip stream, but single rotation props leave a twisting slipstream that loses force by the angle of the twist.

With aviation gasoline prices very high, and likely to remain well above past averages, more efficient airplanes will have a big advantage over less efficient ones. We've discussed before how our Arc Wing airplane has vertical take off and landing, which is the most ideal method of operation. Now we can say that with its dual rotating propeller - and we believe its arc wing as well - it is the most efficient flying machine.

Parting with Parking

Recently, I've been referring to a Russell Baker column from 1996 when I talk about the inherent deficiencies with a car based culture. Today, I'll focus again on the issue of parking and parking lots, and how the Aeroduct System that we've developed at Aeromobile Inc. handles those two issues.

In that article Mr. Baker says "I'm mad about the grocery having relocated from just around the corner to three miles away in what used to be a cornfield out in the country. And why? Because the grocer needs 15 acres of parking lot to accommodate cars that have to be driven three miles every time you want a bag of grapefruit and a gallon of milk." He says later on in his column "I'm mad about spending my life looking for a parking space in the city, mad about paying breathtaking sums of money to parking garages..."

Cars require parking spaces, and the more cars there are, the more parking spaces are needed. In some cases, where land is more available, enormous parking lots are built, consuming perhaps acres of land. In many instances, as with a church or shopping mall, the parking lot's full capacity is utilized only some of the time. The rest of the time, no use is being made of a large paved surface that now covers the former green space where trees or other plants once flourished. This flora is essential in keeping atmospheric carbon dioxide levels from reaching undesirable levels .

Of course, there are places, like Manhattan Island in New York City, where there are not nearly enough parking for the cars that need a place to stop. Then finding parking becomes a vexing and time consuming task, and often a very expensive one as well. The mobility of the automobile matters little if the driver cannot park near his destination, and the expense of using the automobile increases as he drives around to find a spot, and perhaps pays a lot of money when he finally finds one.

So, parking must go, and that's what the Aeroduct System allows. With our system, you debark at the station nearest to your destination, and each possible destination will have a station, unlike mass transit, and your vehicle can return automatically to your house or to a nearby holding area until it is needed again. No verdant land is covered by asphalt, either for the guideways or parking lots. If you don't need your vehicle for a while, it can return home and wait for you to summon it again, or to be used by another family member. Or, if you will need it soon, vertical storage places that can store many Aeroduct craft will allow for the vehicle to remain close by.

The Aeroduct System saves enormous amounts of land that otherwise is being destroyed with pavement, and it saves all sorts of time that drivers now spend looking for the limited parking spots in town and city centers.

Wednesday, May 7, 2008

A (Better) Streetcar Named the Aeroduct System

In my blog post of May 4th, 2008, I commented on remarks made by Russell Baker in a 1996 column he titled “Here is what mad is”. That column was a complaint against the automobile dominated transportation of the modern USA. In this and in future blog entries, I'll comment at length on specific points he made, and how the Aeroduct System of ground transportation deals with his complaints.

For today, I'll discuss his statement “I'm mad about not having a bus or streetcar system left like the one that once enabled people to travel those six miles for a little pocket change.”

Rail transportation of all kinds, including streetcars, dominated the movement of people and freight for the last part of the 1800s and the first 50 years of the 1900s. People did not have to own their own vehicles; they could make use of mass transit for their travels. The advent of the automobile and accompanying roads changed all that. Streetcars and other means of mass transit dwindled in popularity as people used their cars to travel to all sorts of places not accessible by rail transportation. Suburbs grew up around major cities, became completely car based, and the remains of mass transit serviced only the densely populated cities.

This all happened because that's what people wanted. They wanted the freedom to live somewhere instead of a crowded city, and they wanted the freedom to go exactly where they wanted when they wanted. This type of freedom allowed by cars is its major attraction and few people would want to give it up.

Of course, this comes at a price, and Mr. Baker and numerous others have pointed out the many undesirable “side effects” of an automobile culture. But, returning to streetcars and other mass transit transportation is not going to appeal to most people, not matter how bad the future reality of traveling by cars on roads becomes. Mass transit can only work at all (and not always well) where there is sufficient population density, and people who live in suburbs or exurbs are there because they don't want to be part of high density population.

Cars can only be replaced by a ground transportation system that gives people the freedom to have their own vehicle and go where they want when they want. At Aeromobile Inc. our Aeroduct System does just that. It carries vehicles of any size, privately owned for the most part, on a cushion of air and service all the places where cars are currently the only possibility. Our system allows entry and destination points anywhere along the guideway, and these points of accessibility can be at each home, store, church, hospital, business, etc. as close together or as far apart as these locations are in the cities, towns, and suburbs we have today.

So, we can give Mr. Baker and anyone else a direct ride (no stops at other stations along the way) from their home to the store or anywhere else without requiring driving on busy roads in bad weather while consuming lots of high priced fuel and creating lots of carbon emissions. Our system is far more efficient and people and environmentally friendly than that.

Sunday, May 4, 2008

I hear you, Mr. Baker

On May 4, 2008, the NY Times reprinted a column by Pulitzer Prize winner Russell Baker, well known for his often humorous “Observer” column. The Times picked a column that Mr. Baker had written twelve years ago (1996) to the day, prefacing it with the statement Twelve years ago, the columnist Russell Baker, facing higher gasoline prices, complained about being forced to take his car everywhere.”.

For the vast majority of people in the USA, Mr. Baker's litany of complaints about automobile transportation and the impossibility of living with it, and the impossibility of living without it ring quite true. The automobile gives us the freedom to have extensive mobility, yet it extracts quite a price, and by doing away with any other systems of alternative transportation, has become obligatory. As Mr. Baker notes: I'm mad about not having a bus or streetcar system left like the one that once enabled people to travel those six miles for a little pocket change.”

Now that in the year 2008 the price of gasoline is higher than ever before, the economic costs of automobile – and by extension anything wheel based – are enormous. And, what will change this? Electric and hybrid cars are offered as options, as are alternative fuels. However, these are just possible solutions for the fuel costs. What about the costs of maintaining roads, bridges, tunnels and other components of the infrastructure? What about the costs of traffic accidents, fatalities, and the policing of roads?

Mr. Baker also says I'm mad, too, about people who can't drive being rendered immobile by the national drive-or-else policy.”. Automobile transportation is limited to those in a certain age range, a certain economic status and possessing certain physical and mental capabilities.

And, there are the environmental costs of automobiles and their need for level, hard surfaces, to which Mr. Baker alludes when he says “I'm mad about the grocery having relocated from just around the corner to three miles away in what used to be a cornfield out in the country. And why? Because the grocer needs 15 acres of parking lot to accommodate cars that have to be driven three miles every time you want a bag of grapefruit and a gallon of milk.” All those thousands of acres of parking lots in every town in this country (and just about every country), and thousands of miles of paved roads take away not only green space for enjoyment and recreation, but for the trees and other plants to counteract global warming.

So, what do we do about this? I think the answer is the Aeroduct System of ground transportation which we at Aeromobile Inc. have developed. It consists of mechanically simple air cushion vehicles in elevated guideways, completely automated and weather immune. All the problems Mr. Baker found with an automobile based society, and problems that he did not mention at length – like monumental traffic jams - will be fixed by this system. I hope people take it seriously and soon. I'll have a lot more to say about this in future blog entries.

Friday, May 2, 2008

Tilt Rotor Turmoil

The Dreadnaught blog reported in March a story about the faster than expected wearing out in Iraq of the engines for V-22 Osprey tilt rotor aircraft. This issue is just the latest in a long series of problems this plane has experienced.

An article in the the New York Times on April 14 of 2007, summarized the history of the development of the V-22. That story pointed out the high development cost, $20 billion dollars, high craft cost, $80 million each, and the fatal accidents that have occurred with this plane. The article relates further criticisms, including the lack of any ability to land safely should power fail, or the craft run out of fuel. It also states that the vortex ring state, where the propellers get caught in their own turbulence during landing is its chief operational risk.

From my perspective these criticisms should be expected because the V-22 Osprey, like any other tilt rotor craft, has an inherently flawed design. As I see it, the V-22 is far too complex because it uses the wrong technology for vertical flight and as a result many workarounds and add ons are needed to get it to operate at all. It's flaws include:

  1. The laterally disposed rotors present an asymmetrical lift situation, and any unequal lift from one or the other propellers can cause severe roll moments. It is essential to have centerline thrust to avoid this fatal occurrence.
  2. In total power failure or “running out of gas“, the V-22 is a free falling body below 1600 feet altitude. It cannot use its wing for gliding flight to non disastrous landing, because the large propellers will impact the ground on landing and crash the craft. Again, neither can it auto rotate its propellers like a helicopter.
  3. The complexity of V-22 cross shafting, nacelle tilt bearings, two transmissions, and servos, are inherent failure points, and potentially fatal failure elements.
  4. The V-22 is all computer programmed and controlled, additional elements to fail. The pilots need special training that exceed mere rotor craft training.
  5. In VTOL (vertical take off and landing) mode, the download of the propeller slipstream on the wing costs 10% of the trust for lift, plus there is additional upward fountains of air between rotors causing more loss of lift It has a less than optimal use of the propeller lift.
  6. With the high cost and maintenance of the V-22, only the military can afford it.

At Aeromobile Inc., we have designed and experimented with an entirely different approach to vertical take off and landing. Our Arc Wing VTOL airplane uses deflected slipstream for vertical maneuvers, and is a fixed wing airplane for horizontal flight. It does not have the inherent design problems I listed for the V-22 Osprey tilt rotor craft and will make a far more efficient, safe and inexpensive VTOL aircraft.