Commercial airplanes like Boeing, Airbus, Embraer, and Bombardier follow the tube-and-wing configuration, prioritizing practicality and production-friendly designs over pure aerodynamic efficiency.
Emerging eVTOL (electric Vertical Takeoff and Landing) aircraft, especially air taxis, display common design features.
Standard eVTOL Design
Examples: Joby Aviation S4, Vertical Aerospace VA-X4, Maker by Archer, Hyundai SA-1, Beta Aviation ALIA 250
Common Features:
Multi-propulsors
High-gulf wing configuration
V-tail
Five-bladed tilt rotors (except ALIA)
Maximum takeoff weight: 2100-2800 kg
Payload capacity: 400-550 kg
Range: 80-150 miles
Top speed: 150-200 mph
Lift-to-drag ratio: 12-18
Slightly Different eVTOL Designs
ASX MOBI One: Uses tilt wings instead of tilt rotors
Overair Butterfly: One large rotor on each wing and two propulsors on the V-tail
Embraer X:
High wing
V-tail
Ventral fin
Uses ducted fans
Canard wing configuration
Similar range, top speed, and payload
Aerodynamic and Practical Design Features
Size and Capacity
Limited by energy density of the battery
Larger size or higher payload would require more voluminous aircraft, leading to increased weight.
Scaling up the aircraft: Doubling size increases weight 8 times
Battery weight: Should not exceed two-thirds of the total aircraft weight, but usually around one-third.
Range Calculation Equation: Range = (Battery Energy * Propulsive Efficiency * Lift-to-Drag Ratio) / Maximum Takeoff Weight
Example with Maker by Archer: 86 km range
Energy Consumption Breakdown (Maker by Archer Example)
50% for cruise
12% for hovering
20% reserve
15% capacity fade
3% inaccessible to extend battery life
eVTOL vs Conventional VTOL
Conventional VTOL (e.g., Canadair CL-84, AW 609, V-22 Osprey)
Heavier than eVTOL
Much longer range due to higher energy density of jet fuel
V-Tail Empennage
Lighter than conventional stabilizer and fin
Less wetted area
Reduces induced and parasitic drag
Requires longer fuselage to avoid yawing effects
Propellers
Five-bladed propellers:
Higher thrust for same RPM
Lower noise due to slower spin and lower tip speed
Example: Joby S4 (55 dB), Maker by Archer (45 dB)
Double motors for redundancy: More efficient with co- or counter-rotating propellers
Tilt Wing vs Tilt Rotor
advantages: Quicker transition from hover to cruise, reduced thrust interference, simpler single tilting mechanism
disadvantages: Susceptibility to gusts, complexity or bulkiness if batteries are stored in wings
Distributed Battery Pack System
Better weight distribution
Improved heat removal
Prevents thermal runaway propagation
High Gulf Wing Configuration
Provides clearance from rotors
Eases aircraft access
Batteries in wings enable higher center of gravity closer to rotor plane for better stability
Conclusion
eVTOL aircraft design converges on standard features due to practical and aerodynamic reasons.
The best eVTOL design should balance these features for optimal performance.