Embraer to retrofit Phenom flap controls from April
By John Croft
Embraer plans to begin retrofitting the 10 or more Phenom 100s light jets already delivered in the US with a new flap control unit from April to correct the problem at the centre of a Brazilian emergency airworthiness directive (AD) levied on the twin-jet last month.
The US Federal Aviation Administration (FAA) on 27 February issued a complementary “final” AD prohibiting operators from using full flaps on landing unless flying in icing conditions with the associated higher airspeeds.
Embraer learned of problems with the Eaton Aerospace-built throttle quadrant after deliveries began in early January, says Mauricio Almeida, vice-president of Embraer’s executive jets programs.
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Due to integration issues between the flap lever, which has four pre-set flap levels, and the box itself, Embraer has determined through analysis that the system could improperly detect that the flaps have failed due to a mis-compare between the lever reading and the actual flap position.
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Though no problems have occurred in practice and in more than 500 go-arounds in certification and in-service reliability testing, Embraer has determined that pilots trying to raise flaps from the fully extended ("FULL") to the go-around (“2”) position could be faced with stick-pusher activation due to the lever issues. The company alerted Brazilian authorities to the problem, who then issued the AD.
The Phenom has a stick shaker and stick pusher, the former activates as the aircraft approaches an aerodynamic stall to alert the pilot to the issue; the latter activating if the aircraft continues to approach a stall, physically pushing the control column forward to prevent a stall.
As built, the Phenom 100 anti-stall logic includes a safety feature whereby the stick shaker and stick pusher threshold occur at a higher speed if the system detects a flap failure or if the aircraft is flying in icing conditions.
Embraer is concerned that pilots flying in nominal conditions, unaware of the possibility of a mis-compare, could raise the flaps to the “2” position from the “4” position on go-around and be faced with an unexpected stick pusher, causing loss-of-control near the ground.
The fix, being developed by Embraer and Eaton, will include stick shaker and stick pusher thresholds for each flap setting rather than a single global level as currently designed.
Almeida says Embraer expects to certify the new system by mid-March and will begin retrofits on the delivered fleet and on the assembly lines by the end of March.
