Flaps have not achieved the flap handle commanded position
The flaps have not moved or have stopped short of the position commanded by the flap handle. This can be caused by mechanical interference, mechanical failure, or an electrical problem between the flap handle and the flap hyraulic motor. Of these problems, the only one you can work around is if the electrical problem lies in the FSECU. The procedure has you bypass the FSECU with the ALT FLAP switch. If that doesn't work, you are going to land with the flaps where they are.
If the flaps fail to extend when commanded, the primary channel of the FSECU may be the cause. Proceed as follows:
If flaps extend normally, proceed with normal landing. If flaps do not extend normally, see Partial or Jammed Flaps Landings
NOTE: With stab armed, normal pitch trim is unavailable other than manual trim using the normal trim wheel. Electric pitch trim must be disengaged (DISENG) in order to use the trim wheel. Engaging the autopilot will allow the autopilot to trim the airplane using normal electric pitch trim.
If stabilizer matches flap position, proceed to Step 7.
If stabilizer fails to move:
We made a big deal of this in the G-III and G-IV. Then, in the G-V, we decreased our VREF by fifteen knots and it stopped being a big deal. Now, in the G-450, we got ten of those knots back, but it still doesn't seem to be a big deal. I think it's because the brakes are so much better than they were with the G-IV and we can now move the stabilizer to match the flaps.
You just need to line up the stab to match the flap with the PFD indication. Then return the EMER STAB switch to OFF and you can trim normally. A piece of cake.