Flight Testing of the Grob 120 TP

Thomas Brenner, Grob Aircraft AG, Germany
Dr. Matthias Cremer, messWERK GmbH für Mess- und Anzeigetechnik Germany

Abstract

For the flight testing of the Grob 120TP the company Grob Aircraft works together with the company messWERK which equipped the aircraft with a measurement system for most tests.

The flight test system measures all control inputs and forces as well as attitude and the flow angle for instance. During the installation and calibration of the sensor system on the ground everything worked fine without any problems.

The first flight was another good example that ground preparation and testing on the ground is only half the way to flight testing. During the first flight three sensors failed suddenly at one point and the pilot seemed to be prepared for the next Olympic Games as he could hold a stick force of 3000 N without any problems.
It took some flights to find out what was going wrong and how to solve the problems. The wing boom sensors were destroyed by switching of the ignition system of the propeller tur-bine. And finally we found the reason for the high stick forced in a huge radio station quite close by which send a secondary lobe to Mindelheim.

For cooling test flights we had to block the oil cooler thermostat and so we designed a block-ing element and installed it in the oil cooler. The post-flight data evaluation first showed rea-sonable oil temperatures but we were slightly in doubt about the data. We repeated the test another day with different OAT but the oil temperatures kept the same as the flight before. And even a third cooling test flight at a third OAT showed just little different temperatures between the three cooling test flights. Though we surely believed in the function of oil cooler thermostat blocker we checked the thermostat and found out that the oil cooler was not com-pletely blocked. A small gap of the blocking element kept the oil cooler thermostat working all the time.