Eurocopter Deutschland will begin a further phase of flight testing of an EC135 with a fly-by-light flight control system (FCS) in July. This will evaluate the full system developed for German aerospace research organisation DLR's Active Control Technology demonstrator/Flying Helicopter Simulator (ACT/FHS).

The programme is funded by the DLR and the German defence ministry. The EC135, fitted with a quadruplex fly-by-light control system, was flown for the first time earlier this year (Flight International, 5-11 February). Fly-by-light systems replace fly-by-wire's electrical wiring with optical fibres.

Project leader Dr Ulrich Butter says the ACT/FHS has a four axis - longitudinal, lateral, directional and collective - fly-by-light system with a mechanical back-up. The latter is a requirement of German airworthiness authority LBA and DLR, which is due to receive the machine by October.

As well as providing a safety back-up, the mechanical system also back-drives the safety pilot's controls, which mimic the evaluation pilot's inputs and allows the safety pilot to monitor the system, says Butter.

The FCS enables the helicopter to be flown as a standard EC135 or as an airborne simulator for another helicopter, says Butter. The fly-by-light system has been tested since January to ensure that the machine has the same handling characteristics as a production EC135. The next phase of testing will evaluate the full system. The FCS is also reprogrammable, says Butter.

Liebherr has provided the "smart actuators", which incorporate control electronics and clutches to switch flight control between the fly-by-light and mechanical systems, and the safety and evaluation pilots.

Liebherr also supplied the quadruplex computer, the cockpit interface control unit (CICU), which is the heart of the system and hosts the software that allows the ACT/FHS to be flown as an EC135 or another type.

It is also where system monitoring, averaging and other functions are processed. The CICU comprises two channel systems that use dissimilar hardware and software, says Butter.

Source: Flight International