BOAC,
I don’t fully follow your question so if I missed your point please try me again…
In my earlier post I spoke about slats, that was sloppy, I should have used the phrase LE Devices.
The autoslat system will automatically move the LE Devices from Ext to Full Ext whenever the speed is v low and the LEDs are only at Extend. When the speed is restored it will automatically move them back to Ext again. It works at F10 because the LED’s are only at Extend in that config. Why? I guess to protect during flap retraction in the F15 T/O or G/A case or during approach when F10 was used (remember F10, 160?).
The “at normal rate” only applies to PTU operation (of the autoslats). If there were no PTU the autoslat would probably not work without B sys press, or only at a reduced rate with only the Elec hyd pump because it is not as powerful as the Eng hyd pump.
“Will it retract the LEDs from full to extend if you stop the alt retract at more than 'UP' (and, of course, will it complete the retraction at 'Clean')?” – Yes but only if the autoslat system had moved then to full ext because you had got to close to the stall speed. Did you mean to say “alt retract” because retracting flaps with the alt system will not move the LEDs.
Think of the autoslat system like the flap load relief. Flap load relief automatically and temporarily retracts the flaps to prevent you damaging them during an overspeed. The autoslats automatically and temporarily moves the LEDs from Ext to Full Ext to help prevent you from stalling. Both systems automatically return the aircraft to the selected config after the condition is over.
SpannersatKL,
I think you are confusing the activation criteria of the PTU with the LGTU. I promise you the PTU (usually) works quite well with both engines running.
Hope this helps.
S&L