Flight test vibration monitoring system

On a recent European turbo-prop engine development program, there was a need to record the vibration from the engine on the initial set of flight tests. Key vibration indicators then needed to be displayed in the flight deck so that the flight crew could operate the test aircraft in a safe manner at all times.

HGL were asked to provide an acquisition and monitoring system that could be used to meet both of these requirements. The highly unusual nature of the flight test plan meant that it was necessary to adapt an Eagle system for flight test purposes, and to produce some special custom software to interface the Eagle into the flight deck display system.

The system was specially adapted to handle the harsh vibration environment within the aircraft during this particular flight test program. The unit was also configured to operate in an unattended fashion. The software was set up to begin monitoring the engine shaft rotation immediately after powering up. Pre-programmed triggers were then used to begin automatic recording of data whenever the test engine was rotating.

While the dynamic flight test data was being recorded for later analysis on the ground, the acquisition system was also required to calculate the vibration levels at the frequencies associated with the rotational speed of each shaft. These vibration levels were sent, via TCP/IP messages, from the Eagle unit mounted at the rear of the plane, forwards to a display system rigged up in the flight deck for the pilots to view.

At the end of each flight, the recorded data sets were automatically downloaded onto a laptop disk for later analysis.


Marshall Aerospace image

HGL Eagle unit