Liquid tank level measurement
An exemplary liquid tank level measurement system includes a tank having a wall, an accelerometer attached to the wall and configured to measure a vibration in the wall, and an instrument electronically connected to the accelerometer, the instrument configured to communicate a liquid level condition responsive to a vibration measurement received from the accelerometer.
1. An aircraft, the aircraft comprising:
an engine connected a gearbox to drive a rotor when the aircraft is operating, wherein the operating aircraft has an inherent forcing frequency;
the gearbox comprising a tank;
a lubricant in the tank;
an accelerometer attached to a wall of the tank and operable to measure the inherent forcing frequency in the wall; and
an instrument electronically connected to the accelerometer and operable to communicate a level of the lubricant in the tank responsive to a forcing frequency measurement received from the accelerometer.
2. The system of claim 1 , wherein the instrument is operable to communicate an alarm when the lubricant level is below a threshold level.
3. The system of claim 2 , wherein the alarm is an audible alarm.
4. The system of claim 1 , wherein the vibration measurement is along an axis normal to the wall.
5. The system of claim 1 , wherein the accelerometer consists of a single-axis accelerometer and the vibration measurement consists of a measurement along an axis normal to the wall.
6. The system of claim 1 , wherein the vibration measurement comprises a measurement along more than one axis.
7. The aircraft of claim 1 , wherein the accelerometer consists of a single-axis accelerometer.
8. The aircraft of claim 1 , wherein the accelerometer comprises a plurality of vertically separated accelerometers.
9. A method, comprising:
monitoring a lubricant level in an operating aircraft, the aircraft comprising an engine connected to a rotor through a gearbox, the gearbox comprising a lubricant tank;
measuring, with an accelerometer, a continuous forcing frequency of the operating aircraft in a wall of the lubricant tank; and
communicating the lubricant level in response to the measuring.
10. The method of claim 9 , wherein the lubricant level is communicated to a flight computer.
11. The method of claim 9 , wherein the accelerometer includes two or more vertically separated accelerometers.
12. The method of claim 9 , wherein the communicating comprises communicating an alarm when the lubricant level is at or below a threshold level.
13. The method of claim 9 , wherein the communicating consists of communicating the lubricant level when it is at or below a threshold level.
14. The method of claim 13 , wherein the accelerometer includes two or more vertically separated accelerometers.