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Old 27th Mar 2019, 23:45
  #756 (permalink)  
NSEU
 
Join Date: Feb 2004
Location: Australia
Posts: 1,300
Originally Posted by tdracer View Post
The Flap/Slat Control Units on the 767 are relatively crude by current standards (not surprising - the basic design being nearly 40 years old). They put out analog discretes for 'flaps not stowed' - true anytime the flaps are not fully 'up', and 'flaps in landing' - true when flaps are ~23 degrees or greater (there may well be others - those are the ones that get used by the propulsion systems) - as well as digital outputs for use by systems such as EICAS.
There are also FSPM's (Flap/Slat Position Modules) providing data directly to the AFDS & TMS, including position, not just (flaps out of up, etc) discretes. The leading edge flap position indication system also send signals to the PSEU (Proximity Switch Electronics Unit) for use with other systems. It's difficult to know which box does what.

Regarding your comment...

If anyone cares, on the engine side 'flaps not stowed' turns on continuous ignition.
Wiring schematic 74-31-01 shows an input into the ignition system from the Proximity Switch Electronics Unit (with a gate marked "SLATS RETracted"). However, the flight idle signal definitely comes from the FSEU.

There are also some lesser-known microswitches on the flap lever itself (at 1 unit) which input into the Thrust Management Computer and Flight Control Computers.

These switches are actuated in the flaps 1 detent position.
When actuated, the thrust management computer estimates the slats
moving to the flaps 1 position linearly in 5 seconds.
My training notes use this terminology in relation to GA Thrust Limit Mode:

The thrust limit mode transitions to GA when:
1) TO/GA is pressed on the TMSP (i.e. MCP) in the air
2) In air and the thrust limit mode is not in TO and the FCC signals GS Capture.
3) In the air and the thrust limit mode is not in T/O and flaps transition from zero to one.

The thrust limit mode will be locked in GA for flaps greater than 23.
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