Pancake Aircraft Engine Architecture

I have previously proposed a hybrid turbofan engine where the fan portion was composed of an array of brushless DC (BLDC) fans. This time, I have simplified the turbofan engine even further: it is designed as a single, flat radial turbine. The 360° circle of this radial engine is segmented into four dedicated physical zones, each performing a specific thermodynamic function as the rotor sweeps through them.

The Four-Zone Sequential Cycle

Zone 1: Air Intake: The engine housing is completely closed except for the top face and a portion of the leading edge. Air is sucked vertically from the top and horizontally from the leading edge of the horizontally mounted engine.

Zone 2: Compression: The housing is closed all around, trapping the air pocket and allowing the mechanical compression of the air.

Zone 3: Combustion: The housing remains completely closed. Fuel is injected and ignited, rotating the turbine rotor and generating high-pressure thrust.

Zone 4: Exhaust: The hot gas is ejected laterally (radially outward) from this final closed-face sector.

Wing Integration & Aerodynamics

Because of its exceptionally low physical profile, this pancake engine can be embedded entirely inside the chord of the wing. This integration unlocks three distinct aerodynamic mechanisms:

1. Active Lift via Boundary Layer Ingestion (BLI): By sucking air directly from the top skin of the wing (Zone 1), the engine actively ingests the boundary layer, generating a localized low-pressure sink that produces high active lift.

2. High-Altitude Ram Air Recovery: Sucking air from the leading edge of the wing provides a high-energy ram-air source. This assists the boundary layer intake and prevents engine starvation at high altitudes.

3. Fluidic Ejector (Virtual Bypass): Dedicated, passive ram-air ducts running through the gaps between the engines capture additional air from the leading edge. The lateral exhaust (Zone 4) of the engines is ducted to merge with this bypass air, creating a fluidic vacuum (ejector effect) that pulls the bypass air through without back pressure.

The combined stream of exhaust and entrained bypass air is then ejected through a flat slit nozzle along the trailing edge of the wing. This creates a virtual wing effect (circulation control), extending the effective aerodynamic chord of the airfoil. Additionally, this trailing-edge jet sheet is manipulated using thrust vectoring nozzles for complete fluidic flight control.

Aircraft Configuration & Flight Control Redundancy

The aircraft utilizing this propulsion system is configured as a high-aspect-ratio, staggered biplane:

The Upper Wing: Built with a thicker chord to house the pancake engines. This wing relies entirely on active fluidic thrust vectoring (FTV) via the trailing-edge nozzles for pitch, roll, and yaw control, eliminating mechanical control surfaces.

The Lower Wing: Built with a thin profile optimized for passive aerodynamic lift. It provides vertical structural support to the upper wing in a rigid box formation. It also houses the mechanical flight control surfaces (flaps and ailerons), which remain locked under normal flight and are used strictly as a redundant safety measure during emergencies.

Performance & Operational Benefits

This integrated configuration yields massive vehicle-level advantages:

Aerodynamic Efficiency: The active boundary layer attachment and virtual wing effect dramatically increase the lift-to-drag (L/D) ratio, significantly improving fuel economy.

Short Takeoff and Landing (STOL): The immense lift generated by active upper-surface suction allows the aircraft to operate from exceptionally short runways and maintain flight control under harsh weather conditions.

VTOL Capability: For vertical takeoff and landing, the main landing gear can be replaced by compact rocket engines. During VTOL operations, the thrust vectoring nozzles of the pancake engines can deflect their thrust vectors directly toward the ground to assist the rocket lifters.