# US 11,077,939 B1 · Low observable aircraft having tandem lateral lift fans

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- Number: US 11,077,939 B1
- Document ID: US11077939B1
- Status: Granted
- Kind: B1
- Application number: 16/833,619
- Filed: 2020-03-29
- Granted: 2021-08-03
- Earliest claimed: 2020-03-28
- Assignees: Textron Innovations Inc.
- Applicants: Textron Innovations Inc.
- Inventors: Daniel Bryan Robertson; Kirk Landon Groninga; Steven Ray Ivans; Matthew Edward Louis
- Web page: https://patentgrep.com/patent/US11077939B1

## CPC

- B64C 15/14: the jets being other than main propulsion jets (jet flaps B64C9/38)
- B64C 1/0009: {Aerodynamic aspects}
- B64C 3/10: Shape of wings
- B64C 9/16: at the rear of the wing
- B64C 9/18: by single flaps
- B64C 9/20: by multiple flaps
- B64C 11/001: {Shrouded propellers}
- B64C 11/48: Units of two or more coaxial propellers
- B64C 15/02: the jets being propulsion jets
- B64C 19/00: Aircraft control not otherwise provided for
- B64C 21/08: adjustable
- B64C 27/22: Compound rotorcraft, i.e. aircraft using in flight the features of both aeroplane and rotorcraft
- B64C 27/26: characterised by provision of fixed wings
- B64C 27/30: with provision for reducing drag of inoperative rotor
- B64C 27/78: in association with pitch adjustment of blades of anti-torque rotor
- B64C 29/00: Aircraft capable of landing or taking-off vertically, e.g. vertical take-off and landing [VTOL] aircraft (rotorcraft B64C27/00)
- B64C 29/0016: {the lift during taking-off being created by free or ducted propellers or by blowers}
- B64C 29/0025: {the propellers being fixed relative to the fuselage}
- B64C 29/0033: {the propellers being tiltable relative to the fuselage}
- B64C 29/0083: {the lift during taking-off being created by several motors of different type}
- B64C 39/10: All-wing aircraft
- B64D 27/16: of jet type
- B64D 33/04: of exhaust outlets or jet pipes
- B64D 35/02: specially adapted for specific power plants
- B64D 35/04: characterised by the transmission driving a plurality of propellers or rotors
- B64D 35/06: the propellers or rotors being counter-rotating
- B64C 2230/04: by actively generating fluid flow
- B64C 2230/06: by explicitly adjusting fluid flow, e.g. by using valves, variable aperture or slot areas, variable pump action or variable fluid pressure
- B64C 2230/16: by blowing other fluids over the surface than air, e.g. He, H, O2 or exhaust gases
- B64C 2230/28: at propeller or rotor blades
- Y02T 50/10: Drag reduction
- Y02T 50/30: Wing lift efficiency
- Y02T 50/60: Efficient propulsion technologies, e.g. for aircraft
- B64C: AEROPLANES; HELICOPTERS
- B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

An aircraft operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a forward flight orientation. The aircraft has a blended wing body and includes an engine, a binary lift fan system, a forced air bypass system and an exhaust system. The engine has a turboshaft mode and a turbofan mode. The lift fan system includes a plurality of ducted fans in a tandem lateral orientation. In the VTOL orientation of the aircraft, the engine is in the turboshaft mode coupled to the lift fan system such that the engine provides rotational energy to the ducted fans generating the thrust-borne lift. In the forward flight orientation of the aircraft, the engine is in the turbofan mode coupled to the forced air bypass system such that the bypass air combines with the engine exhaust in the exhaust system to provide forward thrust generating the wing-borne lift.

## Claims

### Claim 1

An aircraft operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a forward flight orientation, the aircraft comprising:
a blended wing body;
an engine disposed within the body, the engine having a turboshaft mode and a turbofan mode, the engine configured to generate engine exhaust;
a binary lift fan system disposed within the body, the lift fan system including ducted fans in a tandem lateral orientation;
a forced air bypass system disposed within the body, the forced air bypass system configured to generate bypass air;
a transmission disposed between the engine and the forced air bypass system, the transmission engaging the engine with the forced air bypass system when the engine is in the turbofan mode and disengaging the engine from the forced air bypass system when the engine is in the turboshaft mode; and
an exhaust system coupled to the engine and the forced air bypass system;
wherein, in the VTOL orientation, the engine is in the turboshaft mode coupled to the lift fan system such that the engine provides rotational energy to the ducted fans generating the thrust-borne lift; and
wherein, in the forward flight orientation, the engine is in the turbofan mode coupled to the forced air bypass system such that the bypass air combines with the engine exhaust in the exhaust system to provide forward thrust generating the wing-borne lift.

### Claim 2 (depends on 1)

The aircraft as recited in claim 1 wherein the blended wing body further comprises a fuselage and a wing.

### Claim 3 (depends on 1)

The aircraft as recited in claim 1 wherein the blended wing body further comprises a rhombus shaped body.

### Claim 4 (depends on 1)

The aircraft as recited in claim 1 wherein the blended wing body further comprises a rhombus shaped body with winglets.

### Claim 5 (depends on 1)

The aircraft as recited in claim 1 wherein each of the ducted fans further comprises a rotor assembly having a plurality of variable pitch rotor blades.

### Claim 6 (depends on 1)

The aircraft as recited in claim 1 wherein the tandem lateral orientation of the ducted fans is configured to generate roll control moments in the VTOL orientation.

### Claim 7 (depends on 1)

The aircraft as recited in claim 1 wherein the forced air bypass system further comprises an inlet, a bypass fan disposed within the body downstream of the inlet and a bypass duct disposed within the body downstream of the bypass fan, the bypass duct coupled to the exhaust system.

### Claim 8 (depends on 1)

The aircraft as recited in claim 1 wherein the forced air bypass system further comprises:
first and second inlets;
first and second bypass fans disposed within the body downstream of the first and second inlets, respectively; and
first and second bypass ducts disposed within the body downstream of the first and second bypass fans, respectively, the first and second bypass ducts coupled to the exhaust system.

### Claim 9 (depends on 1)

The aircraft as recited in claim 1 wherein the exhaust system further comprises a mixing nozzle.

### Claim 10 (depends on 1)

The aircraft as recited in claim 1 wherein the exhaust system further comprises a film cooled nozzle.

### Claim 11 (depends on 1)

The aircraft as recited in claim 1 wherein the transmission engages the engine with the lift fan system when the engine is in the turboshaft mode and disengages the engine from the lift fan system when the engine is in the turbofan mode.

### Claim 12 (depends on 1)

The aircraft as recited in claim 1 wherein, in the forward flight orientation, the forced air bypass system is configured to generate a bypass ratio of between 8 to 1 and 12 to 1.

### Claim 13 (depends on 1)

The aircraft as recited in claim 1 further comprising an active flow control system configured to generate control moments in the VTOL orientation and the forward flight orientation.

### Claim 14 (depends on 13)

The aircraft as recited in claim 13 wherein at least a portion of the active flow control system is integral with the binary lift fan system.

### Claim 15 (depends on 13)

The aircraft as recited in claim 13 wherein at least a portion of the active flow control system is integral with the exhaust system.

### Claim 16 (depends on 13)

The aircraft as recited in claim 13 wherein the active flow control system further comprises a pitch effector configured to generate pitch control moments in the VTOL orientation and the forward flight orientation.

### Claim 17 (depends on 13)

The aircraft as recited in claim 13 wherein the active flow control system further comprises roll effectors configured to generate roll control moments in the forward flight orientation.

### Claim 18 (depends on 13)

The aircraft as recited in claim 13 wherein the active flow control system further comprises yaw effectors configured to generate yaw control moments in the VTOL orientation and the forward flight orientation.

### Claim 19

An aircraft operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a forward flight orientation, the aircraft comprising:
a blended wing body;
an engine disposed within the body, the engine having a turboshaft mode and a turbofan mode, the engine configured to generate engine exhaust;
a binary lift fan system disposed within the body, the lift fan system including ducted fans in a tandem lateral orientation configured to generate roll control moments in the VTOL orientation;
a forced air bypass system disposed within the body, the forced air bypass system configured to generate bypass air;
a transmission disposed between the engine and the forced air bypass system, the transmission engaging the engine with the forced air bypass system when the engine is in the turbofan mode and disengaging the engine from the forced air bypass system when the engine is in the turboshaft mode;
an exhaust system coupled to the engine and the forced air bypass system; and
an active flow control system configured to generate pitch and yaw control moments in the VTOL orientation and pitch, roll and yaw control moments in the forward flight orientation;
wherein, in the VTOL orientation, the engine is in the turboshaft mode coupled to the lift fan system such that the engine provides rotational energy to the ducted fans generating the thrust-borne lift; and
wherein, in the forward flight orientation, the engine is in the turbofan mode coupled to the forced air bypass system such that the bypass air combines with the engine exhaust in the exhaust system to provide forward thrust generating the wing-borne lift.