# US 10,118,715 B2 · System and method for auxiliary power unit inlet door testing

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- Number: US 10,118,715 B2
- Document ID: US10118715B2
- Status: Granted
- Kind: B2
- Application number: 15/440,494
- Filed: 2017-02-23
- Published: 2018-08-23
- Granted: 2018-11-06
- Earliest claimed: 2017-02-20
- Assignees: Pratt & Whitney Canada Corp.
- Applicants: Pratt & Whitney Canada Corp.
- Inventors: Jean-François Bisson; Patrick Manoukian; Sarah Theriault
- Web page: https://patentgrep.com/patent/US10118715B2

## CPC

- B64F 5/60: Testing or inspecting aircraft components or systems
- B64D 41/00: Power installations for auxiliary purposes
- B64D 2033/0213: {specially adapted for auxiliary power units (APU's)}
- F05D 2220/50: for auxiliary power units (APU's)
- 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
- B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
- F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS

## Abstract

A method and system for operating an inlet door of an auxiliary power unit are provided. A control signal comprising at least one inlet door command is output. In response to the at least one inlet door command, at least one feedback signal is received and compared to the at least one inlet door command. If the at least one received feedback signal matches the at least one expected feedback signal, operation of the auxiliary power unit is allowed. Otherwise, operation of the auxiliary power unit is inhibited.

## Claims

### Claim 1

A method for operating an inlet door of an auxiliary power unit, the method comprising:
outputting a control signal comprising at least one inlet door command;
receiving, in response to the at least one inlet door command, at least one feedback signal;
comparing the at least one received feedback signal to the at least one inlet door command;
if the at least one received feedback signal matches the at least one inlet door command, allowing operation of the auxiliary power unit; and
inhibiting operation of the auxiliary power unit otherwise.

### Claim 2 (depends on 1)

The method of claim 1, wherein the control signal is output to an actuator coupled to the inlet door and operative to move the inlet door amongst a plurality of positions, the at least one inlet door command comprising instructions for commanding the inlet door to at least one of the plurality of positions.

### Claim 3 (depends on 2)

The method of claim 2, wherein the control signal is output as comprising instructions for the at least one feedback signal to be generated in response to the at least one inlet door command without the inlet door being moved to the at least one of the plurality of positions.

### Claim 4 (depends on 1)

The method of claim 1, wherein the control signal is output as comprising instructions for sequentially commanding the inlet door to a fully open position, commanding the inlet door to a partially open position, commanding the inlet door to a closed position, and sending no command to the inlet door.

### Claim 5 (depends on 1)

The method of claim 1, further comprising:
outputting the control signal for a first predetermined time period; and
waiting a second predetermined time period for the at least one feedback signal to match the at least one inlet door command, the second predetermined time period smaller than the first predetermined time period.

### Claim 6 (depends on 1)

The method of claim 1, further comprising, if the at least one received feedback signal does not match the at least one inlet door command:
determining whether the inlet door is currently locked open;
if the inlet door is locked open, disregarding data received in response to the at least one inlet door command; and
inhibiting operation of the auxiliary power unit otherwise.

### Claim 7 (depends on 1)

The method of claim 1, wherein the control signal is output once after completion of a power-up phase.

### Claim 8

A system for controlling an inlet door of an auxiliary power unit, the system comprising:
a memory; and
a processing unit coupled to the memory and configured to:
output a control signal comprising at least one inlet door command;
receive, in response to the at least one inlet door command, at least one feedback signal;
compare the at least one received feedback signal to the at least one inlet door command;
if the at least one received feedback signal matches the at least one inlet door command, allow operation of the auxiliary power unit; and
inhibit operation of the auxiliary power unit otherwise.

### Claim 9 (depends on 8)

The system of claim 8, wherein the processing unit is configured to output the control signal to an actuator coupled to the inlet door and operative to move the inlet door amongst a plurality of positions, the at least one inlet door command comprising instructions for commanding the inlet door to at least one of the plurality of positions.

### Claim 10 (depends on 9)

The system of claim 9, wherein the processing unit is configured to output the control signal as comprising instructions for the at least one feedback signal to be generated in response to the at least one inlet door command without the inlet door being moved to the at least one of the plurality of positions.

### Claim 11 (depends on 8)

The system of claim 8, wherein the processing unit is configured to output the first control signal as comprising instructions for sequentially commanding the inlet door to a fully open position, commanding the inlet door to a partially open position, commanding the inlet door to a closed position, and sending no command to the inlet door.

### Claim 12 (depends on 8)

The system of claim 8, wherein the processing unit is configured to:
output the control signal for a first predetermined time period; and
wait a second predetermined time period for the at least one feedback signal to match the at least one inlet door command, the second predetermined time period smaller than the first predetermined time period.

### Claim 13 (depends on 8)

The system of claim 8, wherein, if the at least one received feedback signal does not match the at least one inlet door command, the processing unit is configured to:
determine whether the inlet door is currently locked open;
if the inlet door is locked open, disregard data received in response to the at least one inlet door command; and
inhibit operation of the auxiliary power unit otherwise.

### Claim 14 (depends on 8)

The system of claim 8, wherein the processing unit is configured to output the control signal once after completion of a power-up phase.

### Claim 15

A non-transitory computer readable medium having stored thereon program code executable by a processor for:
outputting a control signal comprising at least one inlet door command;
receiving, in response to the at least one inlet door command, at least one feedback signal;
comparing the at least one received feedback signal to the at least one inlet door command;
if the at least one received feedback signal matches the at least one inlet door command, allowing operation of the auxiliary power unit; and
inhibiting operation of the auxiliary power unit otherwise.