KAI X1

A VTOL aircraft with two kinds of thrust and four sources of power.

The KAI X1 is a four-seat, hybrid-electric vertical take-off aircraft concept. Two turbofans carry it in cruise, eight electric motors on four coaxial ducted pods lift it off the ground, and two 1 MW diesel APUs, a solar skin and a 550 kWh battery power it when the jets are shut down. FlightCore is the simulator we built to test how it behaves.

See the range estimate Open FlightCore

Hybrid VehicleModeled, not flown

Concept render of the KAI X1 on a seaside landing deck: a dark blue carbon-fiber blended-wing aircraft with four ducted fans, a four-seat bubble canopy and cutaway callouts for the generator, battery pack and fuel tank. — KAI X1 HEVTOL Hybrid Vehicle

Design baseline

The numbers we are building to.

From the KAI X1 build documents. Modeled in FlightCore, not flown.

Ceiling41,000 ft

Cruise360 ktTwo turbofans

Total thrust27,415 lbfFans and turbofans

Thrust to weight1.4+At 19,100 lb loaded

Jet fuel1,180 galJet-A main supply

APU fuel120 galDiesel, isolated cell

Battery550 kWhGraphene, under cabin floor

APUs2 × 1 MWDiesel generator sets

Architecture

Four power sources, built into one airframe.

Jet Propulsion

Two turbofans sit beneath the canted V-tail stabilizers, fed by dorsal flush intakes, for high-altitude cruise. A 1,180-gallon Jet-A supply feeds them.

Electric propulsion

Four wing-mounted pods each hold a pair of counter-rotating fans stacked back to back to cancel torque. Eight axial-flux motors, rated 1,000 hp each, drive them for vertical lift and low-speed flight.

Hybrid loop

Two 1 MW diesel APU generator sets share a dedicated 120-gallon fuel cell in a reinforced firewall bay over the center of lift. Six kilowatts of GaAs solar cells are bonded across the upper fuselage skin and the canted V-tail.

Energy storage

A 550 kWh graphene battery pack is mounted under the cabin floor, which lowers the center of gravity for stable low-altitude handling. A power distribution unit balances load between solar, battery and the APUs.

Airframe

A carbon-fiber lifting body with wide, highly swept wings. The cabin seats four in a 2+2 layout under an elongated, teardrop-shaped glass canopy, with the pods set out on the wings for easy access.

Redundancy

Adjacent coaxial motors re-map throttle output in an instant after a motor or blade failure. Two independent turbofans and two APUs back each other up, alongside the battery.

Flight profile

Four phases, each with its own power source.

The aircraft hands off between sources as fuel and battery state change. FlightCore simulates these hand-offs, including the safety gating on each.

Phase	Name	Speed	Thrust and power	Electric ducts
1	VTOL launch and transition	Up to 150 kt	Eight electric motors drive the coaxial fans, with the 550 kWh battery supplying peak power	Coaxial pods carry the lift, while the turbofans provide forward thrust and additional auxiliary power
2	Turbofan cruise	360 kt	Two turbofans, drawing on the 1,180-gallon Jet-A tank	Powered down above throttle and altitude limits are reached
3	Silent APU transit	215 kt	Turbofans off. Two 1 MW diesel APUs on a dedicated 120-gallon tank, plus 6 kW of solar	Powered by the APUs, targeting no battery drain
4	Battery glide reserve	195 kt	Turbofans and APUs on, 550 kWh battery with solar assist	Running on battery with APU and solar assist

Range estimate

How far it could fly, worked out from physics.

A still-air estimate built from fuel, battery and drag. Check out the map the view the estimated range, and nautical mile coverage.

Turbofan cruiseWith diesel APUsWith battery reserveAirports in range (hover or tap the map)

With up to 12 hours flight endurance, international range.

Estimated total range

3,833NM

Segment	Distance	Time
Climb and transition	140 NM	0.5 h
Turbofan cruise	3,027 NM	8.4 h
Diesel APU transit	504 NM	2.3 h
Battery reserve	161 NM	0.8 h

Electric power needed in APU transit: 665 kW of 2,000 kW installed.

Takeoff weight 19,129 lb

Lift-to-drag ratio 14.0

Turbofan fuel use, lb per lbf per hour 0.72

Fuel reserve 10%

Range in still air is the same from every launch point. The launch point decides the distances: each destination below is a great-circle distance from it, checked against the turbofan, APU and battery legs, with a flight time that follows the same legs.

Destination	From launch point	Reached by	Time
Los Angeles (LAX)	615 NM	Turbofans	1.8 h
Mexico City (MEX)	841 NM	Turbofans	2.4 h
Miami (MIA)	1,421 NM	Turbofans	4.1 h
Toronto (YYZ)	1,453 NM	Turbofans	4.1 h
Washington, DC	1,497 NM	Turbofans	4.3 h
New York (JFK)	1,661 NM	Turbofans	4.7 h
Bogotá (BOG)	2,439 NM	Turbofans	6.9 h
Anchorage	2,441 NM	Turbofans	6.9 h
Honolulu	2,804 NM	Turbofans	7.9 h
London (LHR)	4,480 NM	Beyond by 647 NM	—
São Paulo	4,777 NM	Beyond by 945 NM	—
São Paulo (GRU)	4,779 NM	Beyond by 947 NM	—
Tokyo Haneda (HND)	5,309 NM	Beyond by 1,476 NM	—
Dubai (DXB)	7,230 NM	Beyond by 3,397 NM	—

International airports in range (6)

Airport	City	Distance	Reached
LAX	Los Angeles	615 NM	Turbofans
MEX	Mexico City	841 NM	Turbofans
MIA	Miami	1,421 NM	Turbofans
YYZ	Toronto	1,453 NM	Turbofans
JFK	New York	1,661 NM	Turbofans
BOG	Bogotá	2,439 NM	Turbofans

How this is calculated

Turbofan cruise: Breguet range, R = (V / TSFC) × (L/D) × ln(W start / W end), at 360 kt, burning the main tank less a climb allowance and the reserve.
Diesel APU transit: power = drag × speed ÷ (0.70 propulsive × 0.90 electrical efficiency), minus 4.2 kW of solar. Diesel burns at 0.50 lb per kWh of electricity. Speed is 215 kt.
Battery reserve: 85% of the 550 kWh pack at the same power model and 195 kt.
Fixed inputs: 1,180 gal jet fuel at 6.71 lb/gal, 120 gal diesel at 7.0 lb/gal, climb allowance of 8% of the jet fuel and 140 NM, the same lift-to-drag ratio in every phase, the same reserve fraction on both fuels.
Left out: wind, weather, detours, payload changes and altitude effects on speed and fuel use.

Safety and redundancy

Failure modes, designed in.

Threat	Defect	Automated fail-safe
Motor or blade failure	One motor or blade fails in a coaxial pod	Adjacent coaxial motors re-map throttle output instantly, and the paired motor takes up the load to hold trim.
Turbofan flameout	Compressor stall or flameout at 41,000 ft	The remaining turbofan carries on while the electric fans spool up on battery power to stabilize control.
Battery thermal runaway	Cell temperature rises in the main battery	Intumescent barriers isolate the cell matrix and a pyrotechnic disconnect clears the circuit. Load moves to the APUs and solar.

Flight control

One command, many actuators.

Because the X1 vectors thrust two ways, the pilot or autonomy layer does not command nozzles or motors. It commands forces, and a triply redundant flight computer allocates blade pitch, motor speed, nozzle angle and duct tilt in real time.

Mass layout: the battery sits low under the floor and the APU cell over the center of lift, so weight stays close to where the lift is.
Autonomy: FlightCore models the hand-offs between propulsion modes and the clearance logic that gates each one.
Maintenance: rotor ultrasonic inspection every 250 flight hours and insulation tests before each launch.

Still being reconciledHeadline range, endurance and vertical-lift figures will be published after our build documents and simulator are checked against each other. Until then we show only the baseline above.

Work with us

Interested in the KAI X1?

Write to the founder about the program, testing partnerships or a FlightCore demo.

CDL@KAI-IndustriesCorp.com

KAI X1 HEVTOL