# US 2019/0376576 A1 · Dual-stage, mixed gas/fluid shock strut servicing

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- Number: US 2019/0376576 A1
- Document ID: US20190376576A1
- Status: Published application
- Kind: A1
- Application number: 16/210,662
- Filed: 2018-12-05
- Published: 2019-12-12
- Earliest claimed: 2018-06-08
- Assignees: Goodrich Corporation
- Applicants: Goodrich Corporation
- Inventors: Amir Fazeli; Matthew R Gomez; Adnan Cepic; Susanne M Reber
- Web page: https://patentgrep.com/patent/US20190376576A1

## CPC

- F16F 9/3264: {Arrangements for indicating, e.g. fluid level; Arrangements for checking dampers (F16F9/3292 takes precedence; testing of vehicle damping G01M17/04)}
- F16F 9/3271: {Assembly or repair}
- B64F 5/40: Maintaining or repairing aircraft
- B64F 5/60: Testing or inspecting aircraft components or systems
- F16F 9/063: {comprising a hollow piston rod}
- F16F 9/486: {comprising a pin or stem co-operating with an aperture, e.g. a cylinder-mounted stem co-operating with a hollow piston rod}
- B64C 25/60: Oleo legs
- B64F 5/50: Handling or transporting aircraft components
- F16F 9/0209: {Telescopic (F16F9/04 takes precedence)}
- F16F 9/3235: {of cylinders (F16F9/483 takes precedence)}
- F16F 2230/46: Maintenance
- G01M 17/04: Suspension or damping
- F16F: SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
- B64F: GROUND OR AIRCRAFT-CARRIER-DECK INSTALLATIONS SPECIALLY ADAPTED FOR USE IN CONNECTION WITH AIRCRAFT; DESIGNING, MANUFACTURING, ASSEMBLING, CLEANING, MAINTAINING OR REPAIRING AIRCRAFT, NOT OTHERWISE PROVIDED FOR; HANDLING, TRANSPORTING, TESTING OR INSPECTING AIRCRAFT COMPONENTS, NOT OTHERWISE PROVIDED FOR
- B64C: AEROPLANES; HELICOPTERS
- G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR

## Abstract

A method for servicing a dual-stage, mixed gas/fluid shock strut may comprise measuring a servicing temperature, charging a secondary gas chamber with compressed gas, wherein a secondary chamber pressure corresponds to the servicing temperature, pumping oil into a primary chamber of the shock strut, and charging the primary chamber with compressed gas.

## Claims

### Claim 1

A method for servicing a dual-stage, mixed gas/fluid shock strut, comprising:
measuring a servicing temperature;
charging a secondary gas chamber with a first quantity of compressed gas, wherein a secondary chamber pressure corresponds to the servicing temperature;
pumping an oil into a primary chamber of the dual-stage, mixed gas/fluid shock strut; and
charging the primary chamber with a second quantity of compressed gas.

### Claim 2 (depends on 1)

The method of claim 1, wherein the primary chamber is charged with the second quantity of compressed gas until the secondary chamber pressure corresponds to the servicing temperature as indicated by a secondary chamber pressure servicing chart.

### Claim 3 (depends on 2)

The method of claim 2, further comprising extending the dual-stage, mixed gas/fluid shock strut in response to the pumping, wherein the dual-stage, mixed gas/fluid shock strut extends such that a shock strut extension and the secondary chamber pressure match an oil servicing reference curve.

### Claim 4 (depends on 1)

The method of claim 1, further comprising extending the dual-stage, mixed gas/fluid shock strut to a shock strut extension corresponding to the secondary chamber pressure, in accordance with an oil servicing reference curve, wherein the oil is pumped into the dual-stage, mixed gas/fluid shock strut until a primary chamber pressure is equal to the secondary chamber pressure.

### Claim 5 (depends on 3)

The method of claim 3, wherein the oil servicing reference curve is provided in the form of at least one of a series of curves or a series of tables for various servicing temperatures.

### Claim 6 (depends on 1)

The method of claim 1, wherein the primary chamber is charged with the second quantity of compressed gas until a primary chamber pressure and a shock strut extension corresponds to a gas servicing reference curve.

### Claim 7 (depends on 1)

The method of claim 1, further comprising releasing an existing gas from the primary chamber.

### Claim 8 (depends on 1)

The method of claim 1, further comprising releasing an existing gas from the secondary gas chamber.

### Claim 9 (depends on 1)

The method of claim 1, further comprising releasing an existing oil from the primary chamber.

### Claim 10

A method for servicing a dual-stage, mixed gas/fluid shock strut, comprising:
charging a secondary gas chamber with a first quantity of compressed gas, wherein a secondary chamber pressure corresponds to a servicing temperature;
pumping oil into a primary chamber of the dual-stage, mixed gas/fluid shock strut, wherein the dual-stage, mixed gas/fluid shock strut extends in response to oil being pumped into the primary chamber until a first shock strut extension and the secondary chamber pressure match a primary chamber oil servicing reference curve; and
charging the primary chamber with a second quantity of compressed gas until a second shock strut extension and a primary chamber pressure match a gas servicing reference curve.

### Claim 11 (depends on 10)

The method of claim 10, wherein at least one of the oil servicing reference curve and the gas servicing reference curve correspond to the servicing temperature.

### Claim 12 (depends on 10)

The method of claim 10, further comprising measuring the servicing temperature.

### Claim 13 (depends on 10)

The method of claim 10, further comprising:
releasing a first existing gas from the primary chamber; and
releasing a second existing gas from the secondary gas chamber.

### Claim 14 (depends on 10)

The method of claim 10, further comprising draining an existing oil from the primary chamber.

### Claim 15

A method for servicing a dual-stage, mixed gas/fluid shock strut, comprising:
charging a secondary gas chamber with a first quantity of compressed gas, wherein a secondary chamber pressure corresponds to a servicing temperature;
circulating oil through a primary chamber of the dual-stage, mixed gas/fluid shock strut via an oil charge port and an oil bleed port;
extending the dual-stage, mixed gas/fluid shock strut, using a servicing tool, to a first shock strut extension corresponding to the secondary chamber pressure according to an oil servicing reference curve;
closing the oil bleed port;
pumping the oil into the primary chamber until the secondary chamber pressure reaches a pre-determined pressure;
closing the oil charge port;
extending the dual-stage, mixed gas/fluid shock strut to a fully extended position; and
charging the primary chamber with a second quantity of compressed gas until a second shock strut extension and a primary chamber pressure match a gas servicing reference curve.

### Claim 16 (depends on 15)

The method of claim 15, wherein at least one of the oil servicing reference curve and the gas servicing reference curve correspond to the servicing temperature.

### Claim 17 (depends on 15)

The method of claim 15, further comprising measuring the servicing temperature.

### Claim 18 (depends on 15)

The method of claim 15, wherein the pre-determined pressure is equal to the secondary chamber pressure.

### Claim 19 (depends on 15)

The method of claim 15, further comprising:
releasing a first existing gas from the primary chamber; and
releasing a second existing gas from the secondary gas chamber.

### Claim 20 (depends on 15)

The method of claim 15, further comprising draining an existing oil from the primary chamber.