Merlin negative G cutout too quick?

[ZaltysZ]

Originally Posted by 41Sqn_Banks

The throttle also had to be closed when negativ g cut out occured. IIRC Reason is that when the throttle remains opened and the fuel flow is restored the engine might overrev as power is regain so quickly that the CSP can't react quick enough.

Engine starves briefly at first and then gets flooded with fuel, because things get reversed: the more fuel you have in float chamber, the more fuel you get into it. Tilly orifice simply restricted fuel flow to amount engine needs at max power setting, so even when things are reversed, float chamber gets no more fuel than engine can burn (at max power setting). Lower the fuel usage (cut the throttle or lower the RPM), and Tilly orifice won't prevent the flooding anymore. Without orifice things are the same, except engine gets flooded even at max power setting.

Running engine at max RPM and open throttle softens the flooding by some extent, but recovering with same settings can indeed result in overrev. It is probably better to cut the throttle just before recovery and not the moment cut out occurs - this seems more optimal.