The fcu is basically off until you get Py air around 50 ish percent. There is a bypass "min flow valve" that once it recieves pressure 100ish psi if i remember. It will give roughly 50% Ng. On the -28's around 90pph, to around 180pph on the -67. From there on the Py acts on the pneumatic bellows"FTG" allowing the valve attached to the governor to control fuel flow.
Last edited by rigpiggy; 23rd Sep 2017 at 04:49.
Reason: Clarification