#2 FMS's operate in DUAL mode,. The #3 FMS that normally has destinat=on information is called a HOT spare FMS„ Since only #1 and #2 FMS units have Performance Computers,. I can select whi=h FMS units operate with the 2 FMS Performance Computers., Note: G550 utilizes 3 Performance computers, so all 3 are active on N