The purpose of a landing controllability check is to see if you can get the airplane into its normal landing configuration and speed at a high enough altitude to give yourself some recovery room if things don't go well, and if that isn't possible, to see how much configuration you can do and how slowly you can fly. Once you've done this at a comfortable altitude, you will know with greater confidence how much flap you can use and what approach speed you can fly when it comes time to land for real.
Everything here is from the references shown below, with a few comments in an alternate color.
CREW SHOULD BE PREPARED TO STOP FLAP MOVEMENT IF AIRPLANE RESPONSE BECOMES OBJECTIONABLE.
a. POWER LEVERS . . . Use asymmetric thrust (as required)
IF LANDING CONTROLLABILITY CHECK REVEALS SIGNIFICANT AFT CONTROL STICK FORCES ARE REQUIRED FOR APPROACH AND LANDING, DELAY SPEED REDUCTION / FLAP SETTING TO MINIMIZE DURATION OF HIGH CONTROL FORCES.
See Controllability Check for general techniques on how to safely accomplish a landing controllability check. The GVII flight control display gives you an excellent presentation of how much elevator travel you have with a frozen stabilizer. The top view show here is of a normally faired stabilizer and elevator. As you reduce speed during a controllability check (middle view) you will see the elevator move toward its limit. You know that as you get to the upper limit of travel (bottom view) you will have nothing left with which to flare the airplane. So make sure you go no slower than where you will have something left.
Gulfstream GVII-G500 Airplane Flight Manual, Revision 4, August 29, 2019
Gulfstream GVII-G500 Production Aircraft Systems, Revision 3, July 15, 2019
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