IDG Disconnect
 

hi...

i would like to know why the engine must be running and above idle power to diconnect the IDG.

and why the push button should not be held for more than 3 sec's (if my memory servs me right)

thanks

IDG disconnect
 

A320.(for example )
When engine is not running, the IDG disconnect control signal is inhibited by the engine oil low pressure switch.

This prevents damage to the IDG disconnect mechanism. Mechanism includes:
solenoid, spring loaded disconnect plunger with threaded pawl, worm shaft and ground reset handle.

3 seconds maximum for IDG pushbutton to prevent damage to the disconnect solenoid.
:ok:

If the input speed is too low, the centrifugal force cannot open the clutch
completely, this can lead to a clutch damage, such as broken teeth.

Maybe this makes it clear: :ok:
http://img47.imageshack.us/img47/151...nectrh7.th.jpg

That diagram is very enlightening. What prevents the clutch from reengaging once the plunger releases?

the plunger is spring loaded. once triggered it remains in position until reset by pulling the loop on the end.

nice pic by the way!!

Sorry.....Errr.."clutch"....

My understanding, both before and after that great graphic, is that the spring-loaded plunger is released by the solenoid (when the DISC switch is held), and positions itself in the rotating wormdrive of the IDG input shaft.

That rotation then forces the wormdrive to displace the input shaft of the IDG such that the spline is fully withdrawn and all IDG rotation ceases, with (manual) reset only available on the ground with the engine shut down.

If the engine is operating at less than idle RPM, the spline drive may not fully withdraw, and although the IDG will still cease to rotate, the two will not be 100% disconnected, like just enough to damage the spline entry surfaces.

Understand, this is quite a violent mechanical action when actuated, the pin drops in and WHAM, the drive is forced out at great speed, enough to fully separate the two drive ends.

That's about as basic as I can explain it!

Cheers..FD..;)