The AirCar Design
There are a half dozen design issues that must be solved when building a flying car. Solving these competing and conflicting design issues has been a formidable obstacle, and the primary reason no one has yet succeeded in building a viable flying car. The Milner AirCar has demonstrated solutions to each of these design issues.
In short, a flying car or roadable aircraft needs to:
1) be light enough to fly yet strong enough to be crashworthy (READ MORE),
2) be roomy enough for practical every-day use yet aerodynamic enough to fly at ~200 MPH (READ MORE),
3) have adequate constant airborne power (~300 hp) with appropriate variable ground power (~20 hp) (READ MORE),
4) have controls and instrumentation that provide adequate and normal control on the ground and also in the air (READ MORE),
5) carry ~150 sq ft of wing area yet be able to fold the wings while on the ground so the vehicle meets highway standards and can drive safely in side winds (READ MORE),
6) adjust the weight on the wheels so in air mode, the rear wheels lift about 90% of the weight, and in ground mode the rear wheels lift about 50% of the weight (READ MORE).
Explanations of Demonstrated Solutions
1) be light enough to fly yet strong enough to be crashworthy. This technology is best demonstrated by Indianapolis-style race cars. The race car without the engine weighs about 900 lbs with an aerodynamic skin over a steel structure. Building the AirCar using a race-car structure allows optimum aerodynamic shape with a steel cage underneath the skin that provides adequate strength for attaching drive train components and for crashworthiness purposes. Having the wheels outside the fuselage also provides for a smoother, quieter ride.
2) be roomy enough for practical everyday use yet aerodynamic enough to fly at ~200 MPH. Form follows function in aerodynamic design, with airplane fuselages being as long as necessary and having as little cross-section as possible. The AirCar design provides 54" front seat shoulder room, the same as two airline first-class seats and comparable to many smaller automobiles being currently produced.
3) have adequate constant airborne power (~300 hp) with appropriate variable ground power (~40 hp). This requires having two separate power sources, a 40 hp ground power unit that powers the wheels while in road mode, and two 160 hp ducted fan engines that power the aircraft while in air mode. We expect that both power sources will be lightweight rotary engines that use readily available gasoline. Rotary engines develop about 1HP per pound and run at about 6000 RPM. When attached to a 32" ducted fan unit, this RPM provides a reasonably quiet fan tip speed of .8 Mach without the need for gearing or speed reduction units.
4) have controls and instrumentation that provide adequate and normal control on the ground and also in the air. With the current move in aircraft to glass panel displays, the AirCar in air mode can easily display required instruments and navigation on its two display screens. Once switched to ground mode one panel becomes the instrument panel and the other becomes the menu screen for air conditioning, cruise control, entertainment center and other indications. The steering wheel in road mode is used as control wheel in air mode.
5) carry ~150 sq ft of wing area yet be able to fold the wings while on the ground so the vehicle meets highway standards and can drive safely in side winds. We created an efficient wing fold that folds the 28 ft wing span into a 7ft wide by 6 ft high box that also contains the two engine nacelles and vertical stabilizers. Room was saved by using our wing fold design that minimizes the extra space used when folding. The outboard sections of the folded wings provide downward lift while in road mode to provide added traction. The outboard canards fold under the inboard canards and retract inside the fuselage. A wide wheel tread width of 80" and long wheel base of 160" provide additional stability on the ground.
6) adjust the weight on the wheels so the rear wheels lift about 90% of the weight in air mode and no more than 67% of the weight in road mode. We have accomplished this by rotating the rear wheels axle arm that places the wheels 180 inches behind the nose in the road mode and 142 inches behind the nose in the air mode. With the center of gravity being at 130 inches aft of the nose, this method provides a 10% front & 90% rear weight ratio in air mode and 33% front & 67% rear weight ratio in road mode.
