Control method for preventing differences between rotor tilt angles in a fly-by-wire tiltrotor aircraft
A system and method for preventing a maximum asymmetric condition between pylon tilt angles due to a degraded pylon in a fly-by-wire tiltrotor aircraft during transitions between airplane mode and helicopter mode includes a conversion system for imparting movement on a right and left pylon. A flight control computer is operatively connected to a set of transducers for measuring pylon angles. The flight control computer is further connected to a set of actuators which are attached to each pylon. The flight control computer receives flight dynamics input from the set of transducers and/or the pilot and sends pylon command to the set of actuators. The conversion system measures the difference between the pylon angles during the transition and provides a pylon command adjustment if the difference exceeds a preset threshold.
1. A conversion system for a tiltrotor aircraft, comprising:
a first rotor system pivotable through a range of pylon angles;
a second rotor system pivotable through the range of pylon angles;
a flight control computer monitoring the first rotor system and the second rotor system, wherein the flight control computer:
transmits a pylon command to pivot the first rotor system and the second rotor system, the pylon command specifying, at least in part, a desired movement of the first rotor system and a desired movement of the second rotor system;
detects an asymmetric condition between the first rotor system and the second rotor system when a difference between a first pylon angle of the first rotor system and a second pylon angle of the second rotor system exceeds a first asymmetry threshold; and
transmits a first pylon command adjustment in response to the asymmetric condition.
2. The conversion system of claim 1 , wherein:
the flight control computer to transmit a second pylon command adjustment, subsequent to the first pylon command adjustment, when a secondary difference between the first pylon angle and the second pylon angle, subsequent to the difference, exceeds a second asymmetry threshold; and
the second asymmetry threshold is greater than the first asymmetry threshold.
3. The conversion system of claim 2 , wherein:
the flight control computer to transmit a third pylon command adjustment, subsequent to the second pylon command adjustment, when a tertiary difference between the first pylon angle and the second pylon angle, subsequent to the secondary difference, exceeds a third asymmetry threshold; and
the third asymmetry threshold is greater than the second asymmetry threshold.
4. The conversion system of claim 1 , wherein the first pylon command adjustment includes a pylon rate adjustment.
5. The conversion system of claim 1 , wherein the first pylon command adjustment includes a pylon position adjustment.
6. The conversion system of claim 1 , wherein the first pylon command adjustment includes a pylon rate adjustment and a pylon position adjustment.
7. A method for preventing a maximum asymmetric condition between a first rotor system pivotable through a range of pylon angles and a second rotor system pivotable through the range of pylon angles in a tiltrotor aircraft, comprising:
transmitting a pylon command to pivot the first rotor system and the second rotor system, the pylon command specifying, at least in part, a desired movement of the first rotor system and a desired movement of the second rotor system;
detecting an asymmetric condition between the first rotor system and the second rotor system in response to a first pylon asymmetry exceeding a first asymmetry threshold, the first pylon asymmetry comprising a difference between a first pylon angle of the first rotor system and a second pylon angle of the second rotor system; and
adjusting the pylon command to a current pylon command in response to the asymmetric condition.
8. The method of claim 7 , wherein the pylon command includes at least one of a pylon rate and a pylon position.
9. The method of claim 7 , further comprising adjusting the current pylon command to a latest pylon command in response to a second pylon asymmetry, subsequent to the first pylon asymmetry, exceeding a second asymmetry threshold.
10. The method of claim 7 , further comprising:
adjusting the current pylon command to a latest pylon command in response to a second pylon asymmetry, subsequent to the first pylon asymmetry, exceeding a second asymmetry threshold; and,
adjusting the latest pylon command in response to a third pylon asymmetry, subsequent to the second pylon asymmetry, exceeding a third asymmetry threshold.
11. A method comprising:
transitioning a fly-by-wire tiltrotor aircraft between an airplane mode and a helicopter mode, the tiltrotor aircraft comprising a first rotor system and a second rotor system;
transmitting an original pylon command to move the first rotor system and the second rotor system, the original pylon command specifying, at least in part, a desired movement of the first rotor system and a desired movement of the second rotor system;
determining a difference between a first pylon angle associated with the first rotor system and a second pylon angle associated with the second rotor system;
comparing the difference to an asymmetry threshold;
detecting an asymmetric condition between the first rotor system and the second rotor system if the difference exceeds the asymmetry threshold; and
adjusting the original pylon command to a current pylon command in response to the asymmetric condition.
12. The method of claim 11 wherein the adjusting the original pylon command includes adjusting a pylon rate.
13. The method of claim 11 wherein the adjusting the original pylon command includes adjusting a pylon position.
14. The method of claim 11 , wherein:
the original pylon command includes a pylon rate; and
the adjusting the original pylon command comprises adjusting the pylon rate to about 50-80% of the pylon rate.
15. The method of claim 11 , wherein:
the original pylon command includes a pylon position; and
the adjusting the original pylon command comprises adjusting the pylon position to about 25-60% of the pylon position.
16. The method of claim 11 , further comprising adjusting the current pylon command to a latest pylon command if a secondary difference between the first pylon angle and the second pylon angle, subsequent to the difference, exceeds a second asymmetry threshold where the second asymmetry threshold is greater than the asymmetry threshold.
17. The method of claim 16 , wherein:
the original pylon command includes a pylon rate;
the current pylon command includes a current pylon rate; and
adjusting the current pylon command comprises adjusting the current pylon rate to between 20 50% of the pylon rate.
18. The method of claim 11 , further comprising:
adjusting the current pylon command to a latest pylon command if a secondary difference between the first pylon angle and the second pylon angle, subsequent to the difference, exceeds a second asymmetry threshold where the second asymmetry threshold is greater than the asymmetry threshold; and
adjusting the latest pylon command if a tertiary difference between the first pylon angle and the second pylon angle, subsequent to the secondary difference, exceeds a third asymmetry threshold where the third asymmetry threshold is greater than the second asymmetry threshold.
19. The method of claim 18 , wherein:
the original pylon command includes a pylon rate;
the current pylon command includes a current pylon rate;
the latest pylon command includes a latest pylon rate;
adjusting the current pylon command comprises adjusting the current pylon rate to between 20 50% of the pylon rate; and
adjusting the latest pylon command comprises adjusting the latest pylon rate to 0% of the pylon rate.
20. The method of claim 11 , wherein adjusting the original pylon command prevents the difference between the first pylon angle and the second pylon angle from exceeding a maximum threshold.