A320 PTU Inhibit
 

Hi All,

I realize the three instances when the PTU on the 320 is inhibited. The Cargo door operation is easy to understand, however, what is the reason behind opposing master switches and parking brake and nose wheel steering bypass pin installed? Is it to prevent any inadvertent tow bar movement or some other reason? Thx

Hi A320drvr,
The NWS lock out pin prevents any HYD powered nose steering input fighting the tow bar. The PTU won't run in this case because you don't need it.

If you look at FCOM, DSC-29-10-20 Generation, PTU
PTU.png
you'll see a clever bit of logic to control when the PTU will run automatically and inhibit it when not needed.

The PTU will run during Single Engine taxi (L/G shock absorber compressed) and with the parking brake off. It doesn't run when stationary with the parking brake on. (Because you don't need it).

A320drvr, this question came up a while ago, you may find your answers in that thread: http://www.pprune.org/tech-log/51200...nhibition.html

Thank you!