Embraer rethinks Phenom 100 brake-by-wire system, training

Washington DC
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A series of runway overruns, blown tyres or failure indications on landing have prompted Embraer to review the flight training regime and design of the brake-by-wire system for its Phenom 100 six-seat twinjet.

Of the six incidents since October, two resulted in overruns, both in Brazil, and two incidents, both in the USA, resulted in a blown main gear tyre. The pilot in one case received a brake failure message and resorted to using the aircraft's emergency brake.

In the overruns incidents, Embraer reported that neither had received brake fail messages. Of the other two events, one was an uneventful landing in the USA after pilots had received the failure message and successfully used the emergency brake. The details were presented at a Phenom 100 maintenance and programme update to owners in Naples, Florida on 27 March.

The company's investigation focused not only on possible mechanical issues, including air in the brake lines, brake control units and valves, but also on pilot techniques.

With the brake-by-wire system, sensors on the pedals send an electronic signal to the brake control unit that controls the hydraulic pressures released by the brake control valve to the brake assemblies, one on each main gear tyre.

The feedback pilots receive through their feet is artificial, provided by springs connected to the pedal linkages. Embraer notes that pilots can sometimes feel that the aircraft is decelerating too slowly even though maximum braking is being applied.

A renewed emphasis on training includes changes to Phenom 100 and Phenom 300 full-flight simulator sessions at the joint venture Embraer CAE training services.

Included now are short runway operations in both dry and wet conditions with a brake failure case with a go-around manoeuvre and landing at an alternate airport using the aircraft's emergency brakes, an exercise designed to prevent the tyre failures experienced by operators in the reported incidents.

After its investigation, Embraer developed improved brake line bleeding procedures as well as a new brake control unit with software improvement the company says makes the it "less sensitive to transient pressure build up conditions".

As of 10 March, seven of the 56 aircraft flying in North America, home to 60% of the fleet, had received the new brake control unit.