Aircraft With Integrated Lift And Propulsion System

• US 20140061392A1
• Filed: 10/21/2013
• Published: 03/06/2014
• Est. Priority Date: 08/15/2005
• Status: Active Grant

• Current Assignee: Abe Karem
• Original Assignee: Abe Karem
• Inventors: Karem, Abe
• Granted Patent: US 8,864,062 B2
• Time in Patent Office: Days
• US Class Current: 244/7.R
• CPC Class Codes: B64C 11/26 Fabricated blades
• CPC Class Codes: B64C 2003/149 for supercritical or transonic flow
• CPC Class Codes: B64C 2027/4736 from composite materials
• CPC Class Codes: B64C 2211/00 Modular constructions of airplanes or helicopters
• CPC Class Codes: B64C 29/0033 the propellers being tiltable relative to the fuselage
• CPC Class Codes: B64C 3/16 Frontal aspect
• CPC Class Codes: B64C 31/024 with auxiliary power plant
• CPC Class Codes: Y02T 50/10 Drag reduction

Abstract

A vertical take-off and landing (VTOL) aircraft is designed to be so efficient that it can be commercially competitive with runway dependent aircraft operating in a range of 100 to 1000 miles or more, with glide ratios of at least 24. Improvements include a combination of high efficiency tilting rotor and wing design that enable both vertical takeoff and efficient high speed cruising, a high aspect ratio wing, and a variable speed propulsion system efficient in both hover and cruise flight. Preferred aircraft use narrow chord inboard and outboard wings, and use efficient lightweight design to achieve unusually low empty weight fraction. In some embodiments, the rotors use medium rather than high modulus fibers, with wider blades of lower taper ratio, to provide the stiffness and mass properties required for high performance OSTR rotor blades. Also disclosed are VTOL aircraft with glide ratios from approximately 26 to over 40.

Claims

1. A flight operational rotorcraft having a rotor with at least first and second radially extending rotor blades, and an engine for providing power to rotate the rotor, wherein:

the rotor has a diameter of at least 15 feet and disc loading of at least 10 psf;

the rotor operates at a variable RPM corresponding to a rotational tip of 0≦

Mach number ≦

0.75 Mach, while also lift loaded between 0 lift coefficient and stall; and

the first blade comprises laminates of fibers, and at least 70% of the weight of the fibers in the first rotor blade have a modulus elasticity of no more than 50 msi.

2. The rotorcraft of claim 1 wherein the fibers have a tensile elongation to failure of at least 1.5%.

3. The rotorcraft of claim 1 wherein the fibers have a tensile elongation to failure of at least 1.8%.

4. The rotorcraft of claim 1 wherein the first rotor blade has a chord width at least 6.5% of rotor diameter at 30% blade station.

5. The rotorcraft of claim 4 wherein the first rotor blade has a blade thickness at least 1.5% of rotor diameter at 10% blade station.

6. The rotorcraft of claim 1 wherein the first rotor blade has a blade thickness at least 1.5% of rotor diameter at 10% blade station.

7. The rotorcraft of claim 1 wherein the first rotor blade has a blade thickness at least 1.4% of rotor diameter at 20% blade station.

8. The rotorcraft of claim 1 wherein the rotor has a diameter of at least 25 feet.

9. The rotorcraft of claim 1 wherein the first rotor blade has between 2 and 5 lengthwise extending cells disposed to operate as a spar.

10. The rotorcraft of claim 1 wherein the first rotor is free of structural dynamic instability in hover at lift of up to at least 20 lb per square foot of rotor disc area between 0 lift coefficient and stall.

11. The rotorcraft of claim 1 wherein the rotorcraft is free of structural dynamic instability up to at least 450 Knots.

12. A variable speed capable rotor blade that is free of structural dynamic instability in hover at lift of up to at least 20 lb per square foot of rotor disc area, and operable at a variable RPM corresponding to a rotational tip of 0≦

Mach number ≦

0.75 Mach, while lift loaded between 0 lift coefficient and stall, the blade comprising;

a length of at least 7 feet;

between 2 and 5 lengthwise extending cells disposed to operate as a spar, and comprising laminates of fibers, and at least 70% of the weight of the fibers in the first rotor blade have a modulus elasticity of no more than 50 msi.

13. The rotorcraft of claim 12 wherein the fibers have a tensile elongation to failure of at least 1.5%.

14. The rotorcraft of claim 12 wherein the fibers have a tensile elongation to failure of at least 1.8%.

15. A variable speed rotor for providing lift and thrust to a rotorcraft, the rotor having a radius measured from a center of rotor rotation and a diameter and comprising:

a rotor hub; and

at least two blades radially coupled to the hub, each blade having a root proximal the hub and a tip distal to the hub, wherein each blade weight in lbs. does not exceed the product of 0.0025 times the diameter of the rotor in feet cubed and wherein the flap stiffness of each blade in lbs-in² at 10% of the rotor radius is not less than the product of 25 times the rotor diameter in feet to the fourth power.

16. A rotor as recited in claim 15 wherein the flap stiffness of each blade is in lbs-in² at 30% of the rotor radius is not less than the product of 10 times the diameter to the fourth power.

17. A rotor as recited in claim 15 wherein the weight of each blade per unit length continuously decreases from the blade root to the blade tip.

18. A rotor as recited in claim 15 wherein the flap, lag and torsional stiffness of each blade continuously decrease from the blade root to the blade tip.

19. A variable speed rotor for providing lift and thrust to a helicopter, the rotor having a radius measured from a center of rotor rotation and a diameter and comprising:

a rotor hub; and

at least two blades radially coupled to the hub, each blade having a root proximal the hub and a tip distal to the hub, wherein each blade weight in lbs. does not exceed the product of 0.0015 times the diameter of the rotor cubed and wherein the flap stiffness of each blade in lbs-in² at 30% of the rotor radius is not less than the product of 10 times the rotor diameter to the fourth power.

20. A tilt rotor aircraft, capable of hover takeoff, comprising:

a fixed wing;

a fuselage having a maximum cross sectional area 3-15% of a planform area of the fixed wing;

a rotor coupled to the fuselage through the wing, and having at least first and second radially extending rotor blades,

an engine for providing power to rotate the rotor;

the fuselage, wing, and rotor configured to provide a glide ratio of 26-40 at 0.55 Mach.

21. The aircraft of claim 20, wherein the wing and rotor are configured to have a ratio of wing span to rotor diameter of between 2.5 and 3.5.

22. The aircraft of claim 21, wherein the rotor has a diameter of at least 15 feet.

23. The aircraft of claim 21, wherein the rotor has a diameter of at least 25 feet.

24. The aircraft of claim 20, wherein the glide ratio at Mach number 0.6 is not less than 85% of the glide ratio at Mach number 0.55.

25. The aircraft of claim 20, wherein a maximum cross sectional area is 3-8% of the planform area of the fixed wing, and the fuselage, wing, and rotor are configured to provide the glide ratio of 32-40 at 0.55 Mach.

26. The aircraft of claim 20, wherein the aircraft has a rotor maximum RPM in helicopter mode, and the fuselage, wing, rotor and engine are configured to provide flight operationability in airplane mode at variable RPM speeds below 70% of the rotor maximum RPM.

27. The aircraft of claim 20, wherein the rotor has a disc loading no higher than 60 psf.