AIRFOIL OF AN AIRCRAFT, AIRCRAFT WITH AN ICE PROTECTION SYSTEM AND METHOD OF ICE PROTECTING THE AIRFOIL

Abstract

An airfoil of an aircraft with an ice protection system, the airfoil having a leading edge, the ice protection system comprising a first applying mechanism for applying an ice protection fluid along at least a portion of the leading edge of the airfoil, and an ice protection fluid recovering mechanism for recovering the ice protection fluid applied by the first applying mechanism, the ice protection fluid recovering mechanism being arranged downstream of the leading edge of the airfoil. The ice protection system further comprises a second applying mechanism for applying the ice protection fluid recovered by the ice protection fluid recovering mechanism on at least one area of the airfoil arranged downstream of the leading edge of the airfoil. An aircraft may comprise at least one airfoil provided with the ice protection system. A method may be used to protect the airfoil of an aircraft from ice accumulation.

Claims

1. An airfoil of an aircraft with an ice protection system, the airfoil having a leading edge, the ice protection system comprising a first applying mechanism for applying an ice protection fluid along at least a portion of the leading edge of the airfoil, and an ice protection fluid recovering mechanism for recovering the ice protection fluid applied by the first applying mechanism, the ice protection fluid recovering mechanism being arranged downstream of the leading edge of the airfoil, wherein the ice protection system further comprises a second applying mechanism for applying the ice protection fluid recovered by the ice protection fluid recovering mechanism on at least one area of the airfoil arranged downstream of the leading edge of the airfoil.

2. The airfoil according to claim 1, wherein the ice protection fluid recovering mechanism comprises at least one recovery recess arranged on the surface of the airfoil downstream of the leading edge of the airfoil for recovering the ice protection fluid.

3. The airfoil according to claim 2, wherein the recovery recess comprises a cover that is open in icing conditions and that is closed in non-icing conditions so that it covers the recovery recess to be flush with the surrounding surface of the airfoil of the aircraft.

4. The airfoil according to claim 1, wherein the second applying mechanism comprises at least one pump for pumping the ice protection fluid recovered by the ice protection fluid recovering mechanism to the at least one area of the airfoil arranged downstream of the leading edge of the airfoil.

5. The airfoil according to claim 1, wherein the ice protection system is configured to work in an anti-icing mode and/or in a de-icing mode.

6. The airfoil according to claim 1, wherein the ice protection fluid comprises a freezing point depressant.

7. The airfoil according to claim 6, wherein the concentration of the freezing point depressant in the ice protection fluid is adapted so that the ice protection fluid keeps its ice protection properties after having treated the leading edge of the airfoil of the aircraft.

8. The airfoil according to claim 1, further comprising at least one motor arranged at a trailing edge of the airfoil, wherein the first applying mechanism is configured to apply the ice protection fluid along at least a portion of the leading edge of the airfoil, the ice protection fluid recovery mechanism is arranged on the airfoil downstream of its leading edge(10), and the second applying mechanism applies the ice protection fluid recovered by the ice protection fluid recovering mechanism along at least a portion of the leading edges of the at least one motor arranged on the respective airfoil.

9. The airfoil according to claim 8, wherein each motor comprises a spinner and a rotor and the second applying mechanism is configured to deliver the recovered ice protection fluid onto the spinner, and the spinner is configured to spread the ice protection fluid onto the rotor.

10. The airfoil according to claim 9, wherein the second applying mechanism is configured to apply a constant flow of ice protection fluid to the spinner.

11. The airfoil according to claim 8, wherein each motor comprises a motor flap and a bulkhead and the second applying mechanism is configured to distribute the ice protection fluid recovered by the ice protection fluid recovering mechanism onto at least a portion of the motor flap and the bulkhead of each motor.

12. An aircraft comprising at least one airfoil according to claim 1.

13. The aircraft according to claim 12, wherein the aircraft comprises at least two airfoils as claimed in any of claims 1 to 11, the airfoils being in the form of a pair of wings and/or in the form of a pair of canards.

14. The aircraft according to claim 12, wherein the aircraft is an electric takeoff and landing aircraft.

15. A method of ice protecting an airfoil of an aircraft, comprising the following steps: applying an ice protection fluid on a leading edge of the airfoil; and recovering the ice protection fluid downstream of the leading edge of the airfoil; and distributing the recovered ice protection fluid on at least an area of the airfoil arranged downstream from the leading edge of the airfoil.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Further advantages and details of the present disclosure can be taken from the following description of the figures, which show the following:

[0027] FIG. 1 Aircraft with an ice protection system arranged on airfoils thereof; and

[0028] FIG. 2 side-view of a canard of the aircraft shown in FIG. 1 with the ice protection system.

DETAILED DESCRIPTION

[0029] As outlined above, the object of the present disclosure is to provide a method for ice-protecting an airfoil of an aircraft from ice build-up, which overcomes the disadvantages known from the state of the art, and which, in particular, leads to reduced power consumption and/or reduced weight.

[0030] This object is solved by a method further comprising the step of distributing the recovered ice protection fluid on at least an area of the airfoil arranged downstream from the leading edge of the airfoil.

[0031] The ice protection fluid is disposed by the first applying mechanism at the leading edge of the airfoil of the aircraft, for example, the airfoil surface, in icing conditions and flows back forming a film across the airfoil. After de-icing or anti-icing at least a portion of the leading edge of the airfoil of the aircraft, the ice protection fluid applied by the first applying mechanism is recovered or collected by the ice protection fluid recovering mechanism. The recovered ice protection fluid may also comprise water from de-icing/anti-icing the portion at the leading edge of the airfoil of the aircraft. The recovered or collected ice protection fluid is then transferred to further areas of the airfoil of the aircraft, which are arranged downstream of the leading edge of the airfoil of the aircraft and is applied to these further areas of the airfoil of the aircraft by the second applying mechanism. As the ice protection fluid is first applied on the leading edge of the airfoil land then re-used on a further, downstream portion of the aircraft, the total amount of ice protection fluid needed by the ice protection system can be reduced. The aircraft only needs to be equipped with the amount of ice protection fluid necessary for de-icing the leading edge of the airfoil, the further areas of the airfoil of the aircraft are arranged downstream of the leading edge are ice-protected with the recovered ice protection fluid. Therefore, the overall weight of the ice protection fluid can be reduced. Furthermore, the energy consumption of the ice protection system is reduced in comparison with electrothermal ice protection.

[0032] FIG. 1 shows a perspective view of parts of an aircraft 1. The aircraft 1 is preferably an electrical takeoff and landing aircraft, in short eVTOL. The aircraft 1 is electrically operated, the advantages of which lead to reduced emission of noise and exhaust gases, leading to a reduction of air and noise pollution.

[0033] The aircraft 1 comprises an aircraft body 2, a pair of wings 3 attached to the aircraft body 2 and a pair of canards 4, which are also attached to the aircraft body 2. In FIG. 1, only one of the canards 4 and only one of the wings 3 is shown. The other canard/wing is arranged symmetrically to the first canard 4/wing 3 on the other side of the aircraft body 2. At least one motor 6 is arranged on the trailing edge of each wing 3 and on the trailing edge of each canard 4. In the embodiment shown in FIG. 1, six motors 6 are arranged on the trailing edge of each canard 4 and twelve motors 6 are arranged on the trailing edge of each wing 3. At the tip of each wing 3, a winglet 7 is arranged. The aircraft 1 is further equipped with landing gear 5. The number of motors arranged on each wing/each canard is not limiting. It is thus also possible to arrange more or less motors on each wing/each canard.

[0034] The airfoils of the aircraft 1, in particular, all portions of the surface of the aircraft 1, where ice formations are expected to form during flight in icing conditions, can be provided with an ice protection system 8. Therefore, the ice protection system 8 can be arranged on the leading edge 9 of each canard 4, on the leading edge 10 of each wing 3 and on the leading edges of the motors 6. The leading edges of the motors 6 are the motor inlet upper lip, called motor flap 11 in the following, the motor bulkhead 12 and the spinner 13, as well as, the rotor 14 of each motor 6.

[0035] FIG. 2 shows a side view of one of the canards 4 with at least one motor 6 arranged on the trailing edge 16 of the canard 4. The canard 4 and the motor 6 are provided with the ice protection system 8. In particular, the ice protection system 8 is arranged on the canard 4 and on the motor 6 arranged on the trailing edge 16 of the canard 4.

[0036] The other canard is designed identical to the canard 4 described here. Furthermore, each wing 3 is also provided with an ice protection system 8, which is constructed similarly/identically to the ice protection system 8 on each canard 4. It is also possible to provide the ice protection system on other airfoils of the aircraft.

[0037] The ice protection system 8 uses an ice protection fluid 17, which is applied to the ice-susceptible portions of the aircraft 1. The ice protection system 8 can be operated in a de-icing manner or in an anti-icing manner. The de-icing manner means the removal of preformed ice through the conversion of a thin ice layer on the airfoil surface to water, leading to the remaining pieces being removed due to aerodynamic forces. The anti-icing manner means preventing the incoming super cooled droplets from freezing as the ice protection fluid is reduced in viscosity for easier flow back along the wing with the additional water.

[0038] The ice protection system 8 comprises a first applying mechanism 18, which applies the ice protection fluid 17 onto at least a portion of the canard 4 along the leading edge 9 of the canard 4. The ice protection fluid 17 disperses along the canard 4 in a downstream direction, i.e., in the chordwise direction of the canard 4, as shown by arrow 21 in FIG. 2.

[0039] The canard 4 is provided with an ice protection fluid recovering mechanism 19 for recovering/collecting the ice protection fluid 17 applied to the leading edge 9 of the canard 4. The ice protection fluid recovering mechanism 19 comprises at least one recovery recess 22 in the surface of the canard 4. The recovery recess 22 can be a continuous recess extending along the spanwise direction of the canard 4 or can be composed of a plurality of smaller recesses arranged side by side along the spanwise direction of the canard. The ice protection fluid 17 traveling along the surface of the canard 4 in a downstream direction as shown by arrow 21 enters into the recovery recess 22 and is collected by the ice protection fluid recovering mechanism 19. The recovery recess 22 can comprise a cover that is open in icing conditions and that is closed in non-icing conditions so that it covers the recovery recess 22 to be flush with the surrounding surface of the airfoil of the aircraft, i.e., the canard 4.

[0040] The ice protection system 8 further comprises a second applying mechanism 20. The second applying mechanism 20 applies the ice protection fluid 17 recovered by the ice protection fluid recovering mechanism 19 to further ice-susceptible portions of the aircraft 1 arranged downstream of the trailing edge 16 of the canard 4, namely to the leading edge 23 of the motor flap 11, to the leading edge 24 of the motor bulkhead 12 and to the spinner 13. The second applying mechanism 20 comprises a pump 25, which pumps the recovered ice protection fluid 17 from the recovery recess 22 to the leading edge 23 of the motor flap 11, to the leading edge 24 of the motor bulkhead 12 and to the spinner 13. As described above, the viscosity of the ice protection fluid is reduced during deicing the leading edge 9 of the canard 4. The reduction in viscosity also makes it easier for the pump to move the ice protection fluid to the motor surfaces and the spinner.

[0041] The centrifugal force of the spinner 13 is sufficient to spread the ice protection fluid 17 over itself and over the rotor 14 so that the surfaces of the spinner and the rotor are kept ice-free. Therefore, no inter-cycle ice accretion and no concerns about ice thickness effects on the aerodynamics of the rotor blades occur. Preferably, the pump 25 provides a constant flow of ice protection fluid 17 to the spinner 13. Therefore, the spinner 13 and the rotor 14 remain coated with the ice protection fluid 17 and are protected in icing conditions.

[0042] The ice protection fluid 17 comprises a freezing point depressant. The freezing point depressant lowers the freezing point of water and ensures that ice does not form on the aircraft surfaces even at subzero atmospheric temperature conditions. Preferably, the freezing point depressant is ethylene glycol. The concentration of the freezing point depressant is sufficient for water impinging on the wing/canard areas when de-icing/anti-icing the leading edges thereof and subsequently on the spinner, bulkhead and flap leading edge due to supercooled droplet impingement.

[0043] For VTOL flight, the freezing point depressant ice protection system (FPD IPS) is a viable and mechanically suitable technology for ice protection. The use of a wing recirculation pump mechanism allows the reuse of fluid from the wing leading edge for the ice protection requirements of the spinner, rotor, bulkhead, and flap leading edge. The recirculated fluid is collected through a recess in the airfoil surface that is actuated to open in icing conditions, and otherwise flush with the surface in non-icing conditions to minimize the aerodynamic effect in flight. This saves weight of the total fluid required, and power in comparison to more energy-intensive technologies such as electro-thermal heating.

[0044] Some of the potential advantages include a drastic reduction in overall power requirements (otherwise due to active heating on the canard, wing, rotor blades, spinner, flap and bulkhead), sizing for the fluid requirements only for the canard/wing (as fluid is being reused), leading edge protection using FPD is limited to the stagnation zone and would not interfere with the forward spar on the wing, if the ground icing concept pursued would be fluid based then the motors would be qualified to ingest similar fluid in any case, etc.

LIST OF REFERENCE SIGNS

[0045] 1 aircraft [0046] 2 aircraft body [0047] 3 wing [0048] 4 canard [0049] 6 motor [0050] 7 winglet [0051] 8 ice protection system [0052] 9 leading edge of canard [0053] 10 leading edge of wing [0054] 11 motor flap [0055] 12 motor bulkhead [0056] 13 spinner [0057] 14 rotor [0058] 16 trailing edge of canard [0059] 17 ice protection fluid [0060] 18 first applying mechanism [0061] 19 ice protection fluid recovering mechanism [0062] 20 second applying mechanism [0063] 21 downstream direction [0064] 22 recovery recess [0065] 23 leading edge motor flap [0066] 24 leading edge motor bulkhead [0067] 25 pump