OMS-to-RCS Gauging Sequence

The OMS-to-aft-RCS propellant quantities are calculated by burn time integration. Once each cycle, the accumulated aft RCS thruster cycles are used to compute the OMS propellant used since the initiation of gauging. The number of RCS thruster cycles is provided by the RCS command subsystem operating program to account for minimum-impulse firing of the RCS thrusters. The gauging sequence is initiated by item entry of the OMS right or OMS left interconnect on the RCS SPEC CRT display and is terminated by the return to normal item entry.

The gauging sequence maintains a cumulative total of left and right OMS propellant used during OMS-to-aft-RCS interconnects and displays the cumulative totals as percentage of left and right OMS propellant on the RCS SPEC display. The flight crew will be alerted by a Class 3 alarm and a fault message when the total quantity used from either OMS pod exceeds 1,000 pounds or 8.37 percent.