# US 8,571,814 B2 · Load monitor reliability factor using an advanced fatigue reliability assessment model

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- Number: US 8,571,814 B2
- Document ID: US8571814B2
- Status: Granted
- Kind: B2
- Application number: 12/724,730
- Filed: 2010-03-16
- Published: 2010-09-16
- Granted: 2013-10-29
- Earliest claimed: 2009-03-16
- Assignees: Sikorsky Aircraft Corporation
- Applicants: Jack Z. Zhao; David O. Adams
- Inventors: Jack Z. Zhao; David O. Adams
- Web page: https://patentgrep.com/patent/US8571814B2

## CPC

- G06Q 10/04: Forecasting or optimisation specially adapted for administrative or management purposes, e.g. linear programming or "cutting stock problem" (market predictions or forecasting for commercial activities G06Q30/0202)
- B64F 5/60: Testing or inspecting aircraft components or systems
- G01M 5/00: Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings (G01M9/00 takes precedence)
- G06Q 10/20: Administration of product repair or maintenance
- B64D 2045/0085: {Devices for aircraft health monitoring, e.g. monitoring flutter or vibration}
- G06Q: INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
- 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
- G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT

## Abstract

According to one non-limiting embodiment, a method includes accessing distributions of flight loads associated with one or more flight regimes for a fleet of aircraft. Using the distributions of flight loads, a factor for at least one of the flight regimes is determined that provides a flight load adjustment for a component on each aircraft of a fleet of aircraft known to be affected through at least load damage by the at least one flight regime.

## Claims

### Claim 1

A method comprising:
accessing distributions of flight loads associated with one or more flight regimes for a fleet of aircraft; and
a computer determining a factor for at least one of the flight regimes using the distributions of flight loads, wherein the factor provides a flight load adjustment for a component on each aircraft of a fleet of aircraft known to be affected through at least load damage by the at least one flight regime, and wherein said step of determining a factor for at least one of the flight regimes includes:
A) identifying a critical flight regime from the occurrence distribution;
B) determining a 99th percentile flight load value for the critical flight regime in the occurrence distribution;
C) determining a 50th percentile flight load value for the critical flight regime in the occurrence distribution; and
D) defining the factor as a ratio between the 99th percentile and 50th percentile flight load values for the critical flight regime.

### Claim 2 (depends on 1)

The method as recited in claim 1, wherein said determining, using the distributions of flight loads, a factor for at least one of the flight regimes that provides a flight load adjustment for a component on each aircraft of a fleet of aircraft known to be affected through at least load damage by the at least one flight regime includes:
E) selectively repeating steps (A)-(D) for each of a plurality of critical flight regimes; and
F) defining the factor as a weighted average of factors for individual critical flight regimes.

### Claim 3 (depends on 1)

The method as recited in claim 1, wherein said identifying a critical flight regime from the occurrence distribution includes identifying a flight regime as a critical flight regime in response to the flight regime having a rate of damage with measured loads that exceeds a predefined threshold.

### Claim 4 (depends on 1)

The method as recited in claim 1, further including:
determining, using at least the factor, instructions to modify a lifetime of the component for a selected one of the aircraft from the fleet; and
communicating the instructions to an entity configured to use the instructions to modify the lifetime of the component.

### Claim 5 (depends on 4)

The method as recited in claim 4, wherein the instructions comprise signals on a computer readable medium configured to cause a computer on the selected aircraft to adjust a lifetime of the component by the factor.

### Claim 6 (depends on 4)

The method as recited in claim 4, further comprising displaying indicia corresponding to the lifetime of the component to a user of the selected helicopter.

### Claim 7 (depends on 4)

The method as recited in claim 4, wherein the instructions facilitate adjustment to the lifetime of the component.

### Claim 8 (depends on 4)

The method as recited in claim 4, wherein the method is performed on a computer remote from the aircraft.

### Claim 9 (depends on 1)

The method as recited in claim 1, wherein the distributions include a plurality of flight loads, the method further including:
multiplying the plurality of flight loads by the factor to provide a flight load adjustment such that the flight load adjustment maintains the same level of structural reliability provided by a conventional component life calculation using “high-envelope” flight loads.

### Claim 10 (depends on 1)

The method as recited in claim 1, wherein the distributions include a plurality of flight loads, the method further including:
verifying that the factor achieves a 0.999999 fatigue reliability.

### Claim 11 (depends on 1)

The method as recited in claim 1, the method further including:
dividing a retirement damage level for the component by the factor.

### Claim 12 (depends on 1)

The method as recited in claim 1, modifying a lifetime of the component for a selected one of the aircraft of the fleet in response to the factor.

### Claim 13

A method comprising:
accessing distributions of flight loads associated with one or more flight regimes for a fleet of aircraft; and
a computer determining, a factor for at least one of the flight regimes using the distributions of flight loads, wherein the factor provides a flight load adjustment for a component on each aircraft of a fleet of aircraft known to be affected through at least load damage by the at least one flight regime includes:
determining a Weibull plot of an actual distribution of flight loads for one of the flight regimes; and
defining the factor for a selected critical flight regime as a ratio between a 99th percentile Weibull plot flight loads value and a 50th percentile Weibull plot flight loads value for the flight regime.

### Claim 14

An apparatus comprising a computer configured through computer readable instructions to perform the operations of:
determining a fatigue reliability of an aircraft component in response to at least one of flight usage data, flight load data, historical data, and a fatigue reliability assessment model; and
determining, using distributions of flight loads, a factor for at least one of the flight regimes that provides a flight load adjustment for the component for each aircraft of a fleet known to be affected through at least load damage by the at least one flight regime by performing the steps of:
A) identifying a critical flight regime from the occurrence distribution;
B) determining a 99th percentile flight load value for the critical flight regime in the occurrence distribution;
C) determining a 50th percentile flight load value for the critical flight regime in the occurrence distribution; and
D) defining the factor as a ratio between the 99th percentile and 50th percentile flight load values for the critical flight regime.

### Claim 15 (depends on 14)

The apparatus as recited in claim 14, further comprising:
modifying a lifetime of the component for a selected one of the aircraft from the fleet in response to the factor.

### Claim 16 (depends on 15)

The apparatus as recited in claim 15, wherein said modifying a lifetime of the component for a selected one of the aircraft from the fleet in response to the factor includes at least one of multiplying a plurality of load damage counts by the factor or dividing a retirement damage level by the factor.

### Claim 17

A method performed by a computer either on-board or remote from an aircraft, comprising:
receiving a flight loads reliability factor associated with a component on an aircraft;
multiplying aircraft flight loads by the factor to determine adjusted flight loads using the computer;
the computer adjusting, using at least the flight loads reliability factor, a lifetime of the component in response to the adjusted flight loads;
the computer displaying the adjusted lifetime of the component; and
wherein said step of the computer adjusting, using at least the flight loads reliability factor, a lifetime of the component in response to the adjusted flight loads comprises the computer defining the flight loads reliability factor as a ratio of between a 99th percentile flight loads reliability vale and a 50th percentile flight loads reliability value.

### Claim 18

A method comprising:
accessing distributions of flight loads associated with one or more flight regimes for a fleet of aircraft; and
a computer determining a factor for at least one of the flight regimes using the distributions of flight loads, wherein the factor provides a flight load adjustment for a component on each aircraft of a fleet of aircraft known to be affected through at least load damage by the at least one flight regime; and
wherein the step of the computer determining a factor for a least one of the flight regions comprises the computer defining the factor as a ratio between a 99th percentile flight load value and a 50th percentile flight load value.

### Claim 19 (depends on 17)

The method of claim 17, wherein said receiving a flight loads reliability factor associated with a component on an aircraft includes receiving a single flight loads reliability factor for a plurality of flight regimes, and said multiplying aircraft flight loads by the flight loads reliability factor to determine adjusted flight loads includes multiplying aircraft flight loads for a plurality of flight regimes by the single flight loads reliability factor.

### Claim 20 (depends on 17)

The method of claim 17, wherein said receiving a flight loads reliability factor associated with a component on an aircraft includes receiving a flight loads reliability factor for each of a plurality of flight regimes, and wherein said multiplying aircraft flight loads by the flight loads reliability factor to determine adjusted flight loads includes multiplying each aircraft flight load for a given flight regime by the flight loads reliability factor associated with that flight regime.