Display failures in Embraer twinjet prompt software upgrade
Brazilian, European and US authorities have ordered Embraer 170 operators to conduct checks on the avionics software after the loss of the aircraft's primary and secondary cockpit displays during test flights.
Concern over possible risks from the failures, traced to a network interface card, prompted Brazil's DCA late last month to draw up an emergency airworthiness directive. This instructed the immediate addition of new operational instructions to the aircraft's flight manual, a test of the 170's avionics standard communication bus within 30 days, and the installation of an upgraded version of Honeywell's Primus Epic avionics software within 40 days.
The European Aviation Safety Agency (EASA) has also issued a similar emergency directive, while a general directive has been produced by the US Federal Aviation Administration.
Certification of the 170 was delayed by problems with development of the Primus Epic avionics, and software verification for the Honeywell-developed fly-by-wire flight-control system. "A temporary loss of all display units has been found during some flight tests performed by Embraer on [170] prototype aircraft," says the DCA directive. Such a loss leaves pilots with only the integrated electronic standby system (IESS) with which to fly the aircraft.
While the typical period of display loss has been around 4s, with the system recovering without pilot intervention, the DCA says: "Further investigation showed the theoretical possibility of a sustained loss of all display units, which could lead the flightcrew to experience a significantly increased workload to complete the flight safely."
The DCA, EASA and FAA insist that Embraer 170s should not be flown with the IESS inoperative, even though this was previously allowed by minimum equipment lists. Authorities have also imposed operational restrictions on the type to mitigate the risk from a display-system failure during take-off or landing in low-visibility conditions. EASA says that these restrictions forbid take-off with runway visual range below 600m (1,970ft) and set a minimum approach decision height of 490ft above the runway threshold elevation.
Embraer says the warnings "follow [our] service bulletin issued as a preventative measure in the unlikely event of a display error".
DAVID KAMINSKI-MORROW / LONDON
ADDITIONAL REPORTING BY DARREN SHANNON IN WASHINGTON DC
Source: Flight International
