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Old 27th Jul 2007, 10:18
  #579 (permalink)  
Join Date: Sep 2000
Location: Bielefeld, Germany
Posts: 955
Ground spoiler actuation logic is as follows.

The ground spoilers partially extend 10 degrees when reverse is selected on at least one engine (the other engine at idle) and one squat switch is triggered (one main gear on ground firmly). The ground spoilers extend fully on landing when both main gears have touched down and
* Ground spoilers are armed and thrust levers (both) are at or near idle, or
* They are not armed and reverse is selected on at least one engine (other at or near idle)

"Idle" here means TLA less than 4 degrees, or less than 15 degrees when below 10 ft RA

The main gear touchdown condition is triggered for both mains when their wheel speed is greater than 72 knots, or when the squat switches are on (struts compressed) and the RA is less than 6 ft.

Thrust reverse actuation requires one FADEC channel signalling throttle reverse *and* both main gear struts compressed *and* TLA reverse signals from at least one SEC.

This logic is changed slightly from when I wrote my paper in on the braking logic in 1994.

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