# US 2019/0377366 A1 · System and Method for Rotorcraft Height Control

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- Number: US 2019/0377366 A1
- Document ID: US20190377366A1
- Status: Published application
- Kind: A1
- Application number: 16/004,254
- Filed: 2018-06-08
- Published: 2019-12-12
- Earliest claimed: 2018-06-08
- Assignees: Bell Helicopter Textron Inc.
- Applicants: Bell Helicopter Textron Inc.
- Inventors: Robert Earl Worsham II; Christopher Mike Bothwell; Sung Kyun Kim; Morganne Cody Klein
- Web page: https://patentgrep.com/patent/US20190377366A1

## CPC

- B64C 27/57: automatic or condition responsive, e.g. responsive to rotor speed, torque or thrust
- B64C 13/503: {Fly-by-Wire}
- B64C 27/006: {Safety devices}
- G01S 13/87: Combinations of radar systems, e.g. primary radar and secondary radar
- G01S 13/882: {for altimeters (measuring height using barometric means G01C5/06)}
- G05D 1/0066: {for limitation of acceleration or stress}
- G05D 1/042: {specially adapted for aircraft}
- G05D 1/0607: {specially adapted for aircraft}
- G05D 1/0816: {to ensure stability}
- B64C: AEROPLANES; HELICOPTERS
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES

## Abstract

A method of operating a rotorcraft includes receiving multiple first height data signals from multiple first height sensors on the rotorcraft, wherein the first height sensors measure height using a first technique, receiving multiple second height data signals from multiple second height sensors on the rotorcraft, wherein the second height sensors measure height using a second technique that is different than the first technique, determining a first height signal from the multiple first height data signals based on a selection scheme, determining a second height signal from the multiple second height data signals, selecting the first height signal or the second height signal to determine a selected height signal, and generating a flight control signal and controlling operation of the rotorcraft according to the flight control signal, the flight control signal based on the selected height signal.

## Claims

### Claim 1

A method of operating a rotorcraft, the method comprising:
receiving a plurality of first height data signals from a plurality of first height sensors on the rotorcraft, wherein the first height sensors measure height using a first technique;
receiving a plurality of second height data signals from a plurality of second height sensors on the rotorcraft, wherein the second height sensors measure height using a second technique that is different than the first technique;
determining a first height signal from the plurality of first height data signals based on a selection scheme;
determining a second height signal from the plurality of second height data signals;
selecting the first height signal or the second height signal to determine a selected height signal; and
generating a flight control signal and controlling operation of the rotorcraft according to the flight control signal, the flight control signal based on the selected height signal.

### Claim 2 (depends on 1)

The method of claim 1, wherein generating a flight control signal comprises:
determining a difference between the selected height signal and a reference height;
determining an altitude rate command based on the difference; and
transmitting the altitude rate command to a flight control device to control the flight control device.

### Claim 3 (depends on 1)

The method of claim 1, wherein the first height sensors are radio height sensors, and wherein the second height sensors are barometric height sensors.

### Claim 4 (depends on 1)

The method of claim 1, wherein the selection scheme comprises selecting the first height signal based on the smallest height indicated by the plurality of first height data signals.

### Claim 5 (depends on 1)

The method of claim 1, wherein the selection scheme comprises determining a difference between a first signal of the plurality of first height data signals and a second signal of the plurality of first height data signals.

### Claim 6 (depends on 1)

The method of claim 1, wherein selecting the first height signal or the second height signal comprises comparing the first height signal with a height threshold.

### Claim 7 (depends on 1)

The method of claim 1, wherein selecting the first height signal or the second height signal comprises determining whether any of the plurality of first height sensors are in a failure state.

### Claim 8 (depends on 1)

The method of claim 1, wherein determining a second height signal comprises determining a median value of the plurality of second height data signals.

### Claim 9

A flight control system for a rotorcraft comprising:
a plurality of radio height sensors;
a plurality of barometric altitude sensors; and
a flight control computer (FCC) operable to control one or more flight control devices of the rotorcraft, comprising:
a processor; and
a non-transitory computer-readable storage medium storing a program to be executed by the processor, the program including instructions for providing control of the rotorcraft, the instructions for providing control of the rotorcraft including instructions for:
receiving measured height data from the plurality of radio height sensors;
receiving measured altitude data from the plurality of barometric altitude sensors; and
controlling one or more flight control elements of the rotorcraft and maintaining a vertical position of the rotorcraft, wherein the controlling is based on the measured height data when the measured height data indicates a rotorcraft height at or below a threshold value.

### Claim 10 (depends on 9)

The flight control system of claim 9, wherein the executable program further includes instructions for controlling one or more flight control elements of the rotorcraft and maintaining a vertical position of the rotorcraft, wherein the controlling is based on the measured altitude data when the measured height data indicates a rotorcraft height above the threshold value.

### Claim 11 (depends on 9)

The flight control system of claim 9, wherein the executable program further includes instructions for controlling one or more flight control elements of the rotorcraft and maintaining a vertical position of the rotorcraft, wherein the controlling is based on the smallest measured height of the measured height data.

### Claim 12 (depends on 9)

The flight control system of claim 9, wherein the executable program further includes instructions for determining a limit on the descent rate allowed when maintaining a vertical position of the rotorcraft.

### Claim 13 (depends on 12)

The flight control system of claim 12, wherein the descent rate limit is based on a forward velocity of the rotorcraft.

### Claim 14 (depends on 9)

The flight control system of claim 9, wherein the executable program further includes instructions for determining a limit on the ascent rate allowed when maintaining a vertical position of the rotorcraft.

### Claim 15 (depends on 9)

The flight control system of claim 9, wherein the executable program further includes instructions for controlling one or more flight control elements of the rotorcraft and maintaining a vertical position of the rotorcraft, wherein the controlling is based on the measured altitude data.

### Claim 16

A rotorcraft comprising:
a flight control computer (FCC);
a first radio height sensor coupled to the FCC;
a second radio height sensor coupled to the FCC; and
one or more flight control devices coupled to the FCC and operable to control a flight parameter of the rotorcraft in response to a flight control device control signal received from the FCC;
wherein the FCC is operable to receive a first indication of height from the first radio height sensor and a second indication of height from the second radio height sensor, to generate the flight control device control signal according to the lesser of the two heights indicated by the first indication of height and the second indication of height, and to send the flight control device control signal to the one or more flight control devices.

### Claim 17 (depends on 16)

The rotorcraft of claim 16, wherein the FCC is further operable to determine if one of the first radio sensor or the second radio sensor has failed, and to generate the flight control device control signal according to the indication of height received from the other of the first radio sensor or the second radio sensor.

### Claim 18 (depends on 16)

The rotorcraft of claim 16, wherein the rotorcraft further comprises a plurality of barometric height sensors coupled to the FCC.

### Claim 19 (depends on 18)

The rotorcraft of claim 18, wherein the FCC is further operable to determine if both of the first radio sensor and the second radio sensor have failed, and to generate the flight control device control signal according to an indication of height received from the plurality of barometric height sensors.

### Claim 20 (depends on 16)

The rotorcraft of claim 16, wherein the FCC is further operable to limit a rate of ascent or a rate of descent associated with the flight control device control signal.