System and method for controlling an auxiliary power unit inlet door

1. A method for controlling an inlet door of an auxiliary power unit, the method comprising:

receiving, at a computing device, input data comprising at least one of a current operating state of the auxiliary power unit, an indication as to whether an emergency shutdown of the auxiliary power unit has been commanded, and an indication as to whether at least one operational fault causing a shutdown of the auxiliary power unit is present;

determining, at the computing device, from the input data, whether a condition to inhibit a start of the auxiliary power unit is present;

responsive to determining, at the computing device, that no emergency shutdown has been commanded and that no operational fault is present, indicating that no condition to inhibit the start of the auxiliary power unit is present, outputting a door-opening signal comprising instructions to cause the inlet door to be commanded to an open position in advance of a prospective command to start the auxiliary power unit; and

responsive to determining, at the computing device, that the condition to inhibit the start of the auxiliary power unit is present, outputting a door-closing signal comprising instructions to cause the inlet door to be commanded to a closed position.

2. The method of claim 1 , further comprising determining that the emergency shutdown has been commanded to determine that the condition to inhibit the start of the auxiliary power unit is present.

3. The method of claim 1 , further comprising determining that an operational fault preventing the start of the auxiliary power unit is present and that the auxiliary power unit is not running to determine that the condition to inhibit the start of the auxiliary power unit is present.

4. The method of claim 1 , further comprising:

determining that the auxiliary power unit is in a shutdown state to determine that the condition to inhibit the start of the auxiliary power unit is present;

monitoring a current speed of the auxiliary power unit and an elapsed time period since the auxiliary power unit has been in the shutdown state;

outputting the door-closing signal if the current speed is below a predetermined speed threshold and the elapsed time period is above a predetermined time threshold; and

otherwise, outputting a door-holding signal comprising instructions to cause the inlet door to remain in a last commanded position.

5. 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:

receive input data comprising at least one of a current operating state of the auxiliary power unit, an indication as to whether an emergency shutdown of the auxiliary power unit has been commanded, and an indication as to whether at least one operational fault causing a shutdown of the auxiliary power unit is present;

determine, from the input data, whether a condition to inhibit a start of the auxiliary power unit is present;

responsive to determining that no emergency shutdown has been commanded and that no operational fault is present, indicating that no condition to inhibit the start of the auxiliary power unit is present, output a door-opening signal comprising instructions to cause the inlet door to be commanded to an open position in advance of a prospective command to start the auxiliary power unit; and

responsive to determining that the condition to inhibit the start of the auxiliary power unit is present, output a door-closing signal comprising instructions to cause the inlet door to be commanded to a closed position.

6. The system of claim 5 , wherein the processing unit is configured to determine that the emergency shutdown has been commanded to determine that the condition to inhibit the start of the auxiliary power unit is present.

7. The system of claim 5 , wherein the processing unit is configured to determine that an operational fault preventing the start of the auxiliary power unit is present and that the auxiliary power unit is currently not running to determine that the condition to inhibit the start of the auxiliary power unit is present.

8. The system of claim 5 , wherein the processing unit is configured to:

determine that the auxiliary power unit is in a shutdown state to determine that the condition to inhibit the start of the auxiliary power unit is present;

monitor a current speed of the auxiliary power unit and an elapsed time period since the auxiliary power unit has been in the shutdown state;

output the door-closing signal if the current speed is below a predetermined speed threshold and the elapsed time period is above a predetermined time threshold; and

otherwise, output a door-holding signal comprising instructions to cause the inlet door to remain in a last commanded position.

9. A non-transitory computer readable medium having stored thereon program code executable by a processor for:

receiving input data comprising at least one of a current operating state of an auxiliary power unit, an indication as to whether an emergency shutdown of the auxiliary power unit has been commanded, and an indication as to whether at least one operational fault causing a shutdown of the auxiliary power unit is present;

determining, from the input data, whether a condition to inhibit a start of the auxiliary power unit is present;

responsive to determining that no emergency shutdown has been commanded and that no operational fault is present, indicating that no condition to inhibit the start of the auxiliary power unit is present, outputting a door-opening signal comprising instructions to cause an inlet door of the auxiliary power unit to be commanded to an open position in advance of a prospective command to start the auxiliary power unit; and

responsive to determining that the condition to inhibit the start of the auxiliary power unit is present, outputting a door-closing signal comprising instructions to cause the inlet door to be commanded to a closed position.