Abstract: Performance of a helicopter is evaluated with an apparatus including a recorder section and a reader section interconnected during a start-up period while the pilot is initially operating the helicopter. The recorder includes two analog to digital converters connected across temperature and rotor torque sensors of the helicopter. The converters derive digital signals having values representing the amplitudes of analog signals derived by the sensors. The recorder section has a first logic network that couples the digital signals with a data collecting memory. The reader section includes a second logic network, a digital read-out device and manually activated coding wheels for deriving numeric representing digital signals.