Propulsion engine

1. A propulsion engine for an aircraft, comprising:

a first fan having a set of first blades and a second fan having a set of second blades;

a first angular pitch adjustment mechanism coupled to the set of first blades;

a second angular pitch adjustment mechanism coupled to the set of second blades; and

a linear actuation means coupled to the first angular pitch adjustment mechanism through a first thrust rod and a first annular thrust bearing, the linear actuation means being configured to generate a linear output, wherein:

the linear actuation means acts on the first annular thrust bearing;

the first thrust rod couples the first annular thrust bearing to the first pitch adjustment mechanism in order to transfer linear motion from the linear actuation means to the first pitch adjustment mechanism;

the first angular pitch adjustment mechanism and the second angular pitch adjustment mechanism each comprise one or two unison rings to which each blade of a respective one of the set of first blades or the set of second blades is connected;

the pitch of all blades in the respective one of the set of first blades and the set of second blades is adjustable by rotation of the one or two unison rings;

the first angular pitch adjustment mechanism and the second angular pitch adjustment mechanism are coupled together through a set of axially extending thrust rods and a second annular thrust bearing, such that when the linear actuation means generates an output to the first angular pitch adjustment mechanism through the first thrust rod and the first annular thrust bearing, the first angular pitch adjustment mechanism is caused to adjust an angular pitch of each blade in the set of first blades, and through the transfer of linear motion through the set of axially extending thrust rods and the second annular thrust bearing coupling the first angular pitch adjustment mechanism to the second angular pitch adjustment mechanism, simultaneously the second angular pitch adjustment mechanism is caused to adjust an angular pitch of each blade of the set of second blades;

the set of axially extending thrust rods comprises a second thrust rod and a third thrust rod;

the second thrust rod couples the first pitch adjustment mechanism to the second annular thrust bearing;

the third thrust rod couples the second annular thrust bearing to the second pitch adjustment mechanism;

the second thrust rod is connected to a first crank of the first pitch adjustment mechanism; and

the third thrust rod is connected to a second crank of the second pitch adjustment mechanism.

2. The propulsion engine according to claim 1 , wherein the linear actuation means comprises at least one hydraulic piston.

3. The propulsion engine according to claim 1 , wherein the linear actuation means comprises a plurality of linear actuators.

4. The propulsion engine according to claim 3 , wherein the plurality of linear actuators are circumferentially arranged.

5. The propulsion engine according to claim 1 , wherein the propulsion engine has an engine casing that includes a static part, and the linear actuation means is mounted to the static part of the engine casing.

6. The propulsion engine according to claim 1 , wherein at least one of:

the first angular pitch adjustment mechanism comprises a plurality of first cranks each coupled to a radially inner end of a first blade in the set of first blades; and

the second angular pitch adjustment mechanism comprises a plurality of second cranks each coupled to a radially inner end of a second blade in the set of second blades.

7. The propulsion engine according to claim 6 , wherein the one or two unison rings of the first angular pitch adjustment mechanism comprise at least one of: (i) a first unison ring that couples the first cranks together; and (ii) a second unison ring that couples the first cranks together.

8. The propulsion engine according to claim 6 , wherein the one or two unison rings of the second angular pitch adjustment mechanism comprise at least one of: (i) a third unison ring that couples the second cranks together; and (ii) a fourth unison ring that couples the second cranks together.

9. The propulsion engine according to claim 6 , wherein the first thrust rod is connected to a first crank of the first pitch adjustment mechanism.

10. The propulsion engine according to claim 1 , wherein

the first angular pitch adjustment mechanism is arranged to rotate with the first fan; and

the second angular pitch adjustment mechanism is arranged to rotate with the second fan.

11. The propulsion engine according to claim 10 , wherein there is a plurality of circumferentially arranged first thrust rods.

12. The propulsion engine according to claim 1 , wherein the propulsion engine includes at least one of the following: (i) a plurality of circumferentially arranged second thrust rods; and (ii) a plurality of circumferentially arranged third thrust rods.

13. The propulsion engine according to claim 1 , wherein the first pitch adjustment mechanism and the second pitch adjustment mechanism are arranged such that when the actuation means generates an output, the angular pitch of the set of first blades and the angular pitch of the set of second blades change in a fixed ratio.

14. The propulsion engine according to claim 13 , wherein the ratio is 1:1.

15. The propulsion engine according to claim 13 , wherein the first angular pitch adjustment mechanism and the second angular pitch adjustment mechanism are arranged such that when the actuation means generates an output, the set of first blades and the set of second blades rotate in opposite directions.