Something I tried today for the fun of it.
Lift-off of LGS-0B (series of cutsom-made test missions)
"Houston Amicitia, we have a center engine down over"
"We copy Amicitia, standby"
"Amicitia Houston, Abort ATO, Abort ATO !"
"Amicitia Houston, Main Engine limits to Inhibit"
"Amicitia Houston, MECO confirmed, a lower orbit but still manageable, no OMS-1 required"
"Amicitia Houston, go for +X, no pitch maneuver"
"Mission Control reports of a stable orbit at an altitude of 140nm by 140"
Now that I feel more confident with the Shuttle, I wanted to try an ATO scenario, as I believe no failures have been implemented to cause this kind of scenario, I voluntarily shut the center engine at 5 minutes and 46 seconds (as it happened with STS-51-F) to see what would happend.
Surprisingly, the FCS automatically compensated for the missing engine and continued to burn for 2 more minutes as the 2nd engine isn't burning fuel anymore.
MECO occured at ~10 mins instead of 8:30 and no OMS-1 was required. The mission can be resumed as planned.