The paper describes preliminary design of the Magic Dragon aircar, a fully integrated automobile and airplane with automated conversion, like magic.

The design also features:

• an automobile-style lifting body with an automotive chassis and suspension;
• a front-mounted multi-bladed ducted fan propulsor to be operated in flight or at low power in the road mode with exhaust doors;
• a hybrid electric road drive with batteries charged by a generator on the engine;
• automatically folding swing-wings that may be stowed in the body while in the road mode and an automobile-style rear end and bumper that flips up to form a streamlined tail for flight.

The Magic Dragon is intended to be used on a daily basis as a productivity tool and recreational vehicle. For the former case, preliminary estimates indicate that the baseline trip may be accomplished via Magic Dragon in about the same time as would be required for travel via airliner or private auto and airplane. For the latter case, vacation travel or sport flying may be attractive from the view of scheduling. Designing the 'Magic Dragon' aircar is a "labor of love" work in progress by the author-inventor, whose background is in aerospace engineering.

Arthur C. Clarke

"Mark my words: a combination airplane and motor car is coming. You may smile, but it will come." - Henry Ford

BACKGROUND. The high cost and inconvenience of flying their own airplanes discourages potential airplane owners and pilots who might prefer to use an attractive, reasonable, and practical aircar. In the past, about a hundred different designs for combination automobiles and airplanes have been patented, including the predecessors of the Magic Dragon, and a few were built and operated. Most required awkward and time-consuming ways to convert from car to plane and vice versa. They also lacked the conventional automobile handling and required safety features. The Magic Dragon overcomes these drawbacks by combining the best features of state-of-the-art technologies in a unique, serendipitous architecture to provide more convenience. Higher production rates promise to provide lower costs through the advantages of scale.

A LIGHTER WEIGHT VEHICLE. The Magic Dragon is presented as a design based on aircraft technology, e.g., lightweight engine and aluminum and titanium alloys. It limits payload to two persons, since the majority of cars on the road are often carrying one or two persons. One may view it as a compact car where seating capacity is traded for aircraft components and/or as a four-place airplane where the weight of two passengers and baggage is traded for automobile components.

It may use a hybrid road drive that allows the use of a relatively lightweight complement of batteries for the road drive, as compared with all-electric drives that use batteries only. The usual spare tire is omitted, since most of the operations are flying. Gross Vehicle Weight is estimated at 2,400 lbs. [1100kg] (See Table 1 for weight estimates.)

A half-scale mockup was built in 2000 and displayed at the Dayton Air Show. (See Figure 6.)

SAFETY - At the outset, the author-inventor recognizes the safety risk of the aircar concept and has considered the design of the Magic Dragon from the viewpoint of his extensive background as a System Safety Engineer with the Air Force. As an example, many roadable airplane designers have chosen to use a three-wheel motorcycle design so as to avoid the various motor vehicle safety standards; the Magic Dragon design intends to comply with them. On the other hand, many features found in automobile technology are applied to enhance the safety and convenience of the Magic Dragon while operating in the flight mode, such as safety glass windshields with wipers and washers. Concern on the part of potential manufacturers for potential litigation has discouraged venture capital, so mass production is unlikely in the near future, unless government policies change. The U.S. government has granted some relief as regards liability limits for older aircraft. However, the development of new aircraft, such as Magic Dragons, seems to be better managed by simply making and operating them more safely. Insurance rates may be granted for Magic Dragons that are less than for conventional aircraft, just as is done currently for tricycle gear, centerline thrust, and stall-resistant aircraft that have lower rates than traditional aircraft.

The simple fact that the Dragon may be used as an automobile reduces the cost and risk as contrasted to the cost of ownership of two distinct vehicles in their respective environments and management operation control systems. The risk management, whether by using partially or wholly self-insured methods, is also reduced. The White House has set a

goal of reducing aviation accidents by 50% in the next ten years, as of a few years ago; however, there are no specific analyses and solutions to achieve the goal. The Aircraft Owners and Pilots Association's Air Safety Foundation publishes reports that summarize accidents at http://www.aopa.org/asf/publications/00nall.pdf . The data is used in the Magic Dragon design.

The Dragon is intended to improve safety, reducing insurance costs, and improving overall operation, as contrasted to standard lightplanes, with features such as:

• the enclosed fan with safety grill for less risk of propeller strike injuries;
• the ducted fan may provide increased thrust for shorter take-off (approximately 25%);
• the duct naturally governs fan speed to eliminate the need for a propeller pitch control;
• the ducted fan eliminates slipstream torque for simplified control;
• quieter muffled engine and fan noise levels for less fatigue and environmental impact;
• electric or mechanical road drive may be used to shorten take-off roll;
• simplified pitch and speed flight controls with flaps integrated with elevator trim eliminate the need for separate controls and actions;
• the Warp Action Spoiler Plate, WASP, ailerons eliminate the need for rudder control and associated actions, except for cross-wind landings with slipping versus crabbing;
• the four-wheel braking provides shorter stopping distance so the balanced field length may be reduced and the risk of over-running is reduced;
• the slotted wing provides less risk of loss of control and/or stalling;
• the lifting fuselage lessens the effects of wing stalling, since it would not stall;
• the low center of mass provides less risk of turnover in winds or forced landings;
• redundant four-wheel landing gear provides less risk of loss of control with blow-outs;
• redundant wide-stance front wheel steering for less risk of ground-looping ;
• balanced weight on front and rear wheels for better steering control;
• ground-level cabin doors, without steps, for less risk of injury;
• seating width that is comparable to airliner first-class for less fatigue (31" elbow width);
• the safety windshield provides better crashworthiness;
• the windshield wipers and washers provide better visibility;
• the overhead window provides better visibility during turns for less risk of mid-air collision;
• the duct doors are to be closed via brake linkage to provide reduced landing or abort rollout;
• the road drive eliminates hazard of physical injury due to towing or pushing;
• wide lifting fuselage with a flat bottom and low wing with full-span low flaps provide air-cushioned landings (particularly during emergency landings);
• in unforecast foul weather, the Magic Dragon provides an alternative to getting to destination by landing and driving, thereby reducing the "get home syndrome" hazards;
• Dragoneers can store their Magic Dragons in their hangarage at their home, rather than tieing them down in the weather, particularly during high winds or hailstorms to reduce risk of storm damage, or storing them in hangars, subject to "hangar rash";

Compared to road operations, the flight mode may reduce the risk as contrasted to road operations, considering collisions, slippery roads, and drugged or drowsy drivers.

FLIGHT DESIGN. The design was begun several decades ago. A wind-tunnel test of a one-twelfth scale model revealed three significant pieces of data. (See Figure 1 Cal Tech Wind-Tunnel Test ). Body lift was sufficient to move the center of pressure forward of the wing by the equivalent of one foot, suggesting that the body was lifting as much as the wing. This was expected, since the body area and the wing area were the same, 100 sq. ft.

The lift-to-drag ratio was measured as five to one, 5:1, at an angle of attack of twelve degrees. The staff then filled in the wheel wells with clay and re-tested and found a ratio of eight to one.

Other improvements, such as the pi-tail and increased wingspan and covered wheels are expected to increase the ratio significantly, so that the overall performance is expected to compare favorably with current lightplane designs.

FLIGHT ENGINE - The preliminary design is based on using an aircraft engine of about 160 to 200 horsepower [122-152 kW]. Lightweight automotive engines might also be used, where added weight may be traded for reduced maintenance costs.

PERFORMANCE - The Magic Dragon's flight performance is expected to be comparable to many current lightplanes with similar payloads and engines. Cruising speed at typical altitudes is expected to be about 120 knots [220 kph], or, for better fuel economy, about 100 knots [200 kph]. Range with fuel burn rates of 10 gallons per hour is expected to be about 300 nautical miles [550 km].

ducted fan propulsion - The use of the ducted fan for propulsion was selected for safety and performance. Since the fan is safety screened, the engine may be used to provide some thrust while operating in the road mode. The duct has doors at the exits that may be closed when thrust is not needed, e.g., during braking. When the doors are closed, the airflow re-circulates inside the duct. (See Figure 4, Ducted Fan and Wheels.) As an alternative, the fan may have a clutch. The smaller diameter of the fan allows the whole propulsion unit and body to be placed closer to ground level. This then eliminates the drag of wheel struts and lowers the drag of the wheels. The ducted fan also provides a much slower airflow over the body, further reducing drag. The exhaust flow boosts the wing root lift, providing better takeoff performance.

The ducted fan theory is that it provides increased performance by reducing the losses at the tips where the airflow is sealed, rather than letting the air circulate around the tips, as on a conventional open propeller. The effect is similar to having tip plates and reduces the drag accordingly. The fan speed is naturally governed. Another aspect is that the fan will also decrease the air pressure on the front sides; this has the effect of increasing the diameter.

ROAD DRIVE - The road drive is envisioned as being smaller than usual, since the engine and ducted fan will provide sufficient thrust during most of the driving for Cruising On Aerojets, COAJ. The road drive is for scenarios when surge power is needed, such as for accelerating while climbing ramps, or for reversing. Mechanical or hybrid electric road drives may be used, with connections to the aircraft or automotive engine. The engine will be set for a fast idle speed of about 900-1,200 rpm [15-20 Hz]. The power control will have the usual Reverse, Neutral, and Drive, plus a mode to open the doors in COAJ. The driver can depress the power pedal for the electric motor control and open the engine throttle to modulate the aerojet doors to control thrust while cruising. Thrust is expected to be about 100 pounds with the engine running at a fast idle speed. The pressure at the exits of the duct is estimated at about ten pounds per square foot. The velocity is estimated to be about 100 feet per second additional to vehicle speed while cruising, which would be reduced to modest velocities behind the Dragon.

The aircraft engine's electrical system will be linked to the batteries (Nickel-Metal Hydride).

Very preliminary figures for the added hybrid drive 120 VAC electrical power generation initially uses data for off-the-shelf, belt-driven units:
66 lbs., 4kW, 33 Amps, drawing 6+ hp @ 3600 rpm.

The electric road drive will consist of twin 10 kW motors to provide a surge capacity of 15 horsepower. A differential mechanism is desired, perhaps fluid or magnetic, to equalize power between the motors while ensuring reliability.

Assuming that the twin 10 kW motors are used to accelerate for 15 seconds per cycle, the 0.18 kWh drain from the batteries can be replaced by charging from the generator in 0.18/8 = 0.0225 hr = 81 seconds, plus allowances for efficiency losses. Longer times at lower rates will be studied to determine an optimum for the overall system in typical scenarios.

For a typical scenario of city driving, one can assume a one-mile stretch of road with traffic lights every two blocks, where there are 12 blocks per mile. Also assume that cruising speed is 35 m.p.h., or 50 feet per second, acceleration is 5 m.p.h. per second, and braking is 5 m.p.h. per second. This gives 10 seconds to accelerate that would drain the batteries, then 10 seconds for cruising and 10 seconds for braking that would charge the batteries. Assuming a 50-50 chance of getting a red light and that they're red for the typical 30 seconds, the waiting time is 15 seconds. The scenario gives a deficit of 6 Ampere-hours per mile.

Four 12-volt batteries of 60 Ah capacity each are to be installed, for an 80% Depth Of Discharge, DOD, at a weight of 132 lbs.. With a 66 lb. 4 kWh generator drawing 6+ hp., these will provide a range of driving of 196/6 = 32 miles.

Additional batteries could be added for chronic, severe driving conditions. For highway driving, for a 36-gallon supply and drawing 15 hp at 65 m.p.h. cruise with a specific fuel consumption of about 0.5 lb./hp/hr for a burn rate of 7.5 lb./hr. , gives about 1.25 gph, or 52 m.p.g.. This will provide a range of 36 * 52 = 1,872 miles in 26 hours.

One might conceive a non-flying hybrid electric vehicle similar to the Magic Dragon, but sans all flight components. Such a vehicle would have the benefit of trading the mechanical road drive, with the transmission, for the simpler ducted fan drive, with a simple composite material duct and the exhaust door linkages. This would allow reducing the overall cost and weight. The reduction in moving parts would also increase reliability and simplify maintenance. The ducted fan would also provide traction on slippery road surfaces.

AUTOMATIC CONVERSION - The conversion of the wing is conceived as an electric motor-driven rack and pinion type rod mounted in the wing root with pneumatic cylinder or coil spring assisting. The wing joint is a simple hinge connecting the main wing spar and the main body cross-beam as shown. Aileron and flap torque tubes automatically mate at the joints as shown in Figure 7a. The conversion system has a total of nine motors and twenty solenoid locks. Total of the conversion system weights is estimated at about 20-30 lbs. The wheels may be partially retracted to the extent of the vertical travel of the suspension system as shown in Figure 7b.

PRIMARY CONTROLS. Primary road control is with a conventional steering wheel, brake and power pedals; primary flight control is with a center-mounted control yoke and rudder pedals.

WEIGHT AND BALANCE. The airplane mode c.g. is at station 80, about a foot in front of the wing. With the 200-lb. wings stowed, the c.g. is at station 86. Road distribution is at 46% front, 54% rear.

FLIGHT-ROAD INTERFACE. The operation of the magic dragon series of aircars will take advantage of the thousands of existing airports, both public and private, for transitioning between air and road modes. There is no intention of using the public roads for either taking off or landing, except in dire emergencies, due to the hazards involved, such as distracting other drivers and obstacles.

DIMENSIONS - Dimensions are as follows:

Wingspan: 30 ft. [9.1 m]

Wing area/load: 135 sqft/18 psf [14 sqm/ 78 N/sqm]

Length (road): 19 ft 6 in [ 5.9 m]

Width (road): 92 in., 7 ft. 8 in. [ 2.33 m.]

Height: 80 in., 6 ft 8 in. [ 2 m]

Wheelbase: 118 in. [ 3 m ]

Wheel tread: 60 in. [ 1.5 m ]

Cabin width: 60 in. [ 1.5 m ]

Fan diameter: 36 in. [ 0.9 m ]

Tire diameter: 24 in. [0.6 m ]

VARIANTS. Variants of the basic design may include a stretched version for carrying three people and/or cargo that may be particularly suited for charter or corporate operations with chauffeur- pilots. (See Figure 8.) Another variant may use a swing-tail that would provide simpler structure and a lower center of mass. (See Figure 10)

OTHER TESTING. A small tether-type flight model was built and flown to check on stability with the pi-tail. It flew well. (See Figure 9.)

COST - The cost of the vehicle is estimated to be about $60,000 if the owner-operator builds it from a kit or twice that amount if the vehicle is manufactured in the usual manner. Savings in time for a nominal usage would justify the cost with payback well within the 10- to 20-year life cycle. Operating costs are expected to be on a par with airplanes or sportscars, particularly as regards fuel costs. However, when time value is considered, the per-seat-mile cost is estimated to be favorable.

BUSINESS PLAN - Planning is based on confidence build-up in three phased sub-plans.

Short Range Plan - Building of a Full Scale Mockup, FSM, with conversion systems is planned for 2002. Displays and demonstrations will follow.

Mid-Range Plan - Modification of the FSM for conducting limited flight and road propulsion test and evaluation is scheduled for 2003. Display and demonstrations will also be conducted.

Long Range Plan - Development of prototypes and testing and production kits for potential owner-operators to use for building Magic Dragons.

Eventually, major manufacturers may develop production models for the hundreds of thousands of licensed pilots who do not have their own airplanes and who would buy, rent, or lease aircars.

Intellectual property rights may be obtained for recent improvements; however, some foreign manufacturers may present problems.

The design is now considered to be mature enough for supporters to proceed with prototype development.

Development and production of the "Magic Dragon" aircar is considered to be a viable enterprise that would satisfy a niche market and provide a profitable venture for an extensive period of time.

Luigi Stipa invented the ducted fan circa 1937 and flew the so-called "barrel airplanes"; his work resulted in the first jet-powered airplane, the Caproni-Campini CC-2.

Prof. Edgar Lesher of the University of Michigan Aeronautical Engineering Department, late holder of the World Speed Record for lightplanes, provided guidance and encouragement. He admonished his students to "distort the specifications". The author chose to distort the specification of production quantities by designing for the traveling public.

• U.S. Patents 2,923,494 and 3,612,440.
• NASA TR "Q-Fan" by Hamilton Standard

Richard A Strong, PE, B.Sc. Aero. & Astro. Engrg, MA Mgmt

Major USAF, Retired; GM13 DAF, Retired

Commercial Pilot, ASEL, Instrument

StrongMobile Systems Co

7514 Belle Plain Dr., Dayton, OH 45424-3229

VOX: 800-267-6420 FAX: 937-236-2113

RichStrong@aol.com

www.strongware.com/dragon

"The Wonderful World of Wheels and Wings"