A Cessna 560 flight crew returned to their departure airport when they received multiple system warnings indicative of a failed air/ground squat switch.

Narrative

I was pilot not flying on this night flight. The weather was approximately 600 overcast; hard rain with gusting winds 10-24K from the northwest. The temperature was approximately +5C. The initial climb out went normally until approximately 1;000 MSL when the HYD PRESS/MASTER CAUTION lights illuminated. We also noticed that the GEAR UNLOCK light was still illuminated. Shortly thereafter we got a STAB MISCOMPARE light. The flaps had not retracted with the flap handle selected up. The SIC flew the aircraft while I ran the appropriate checklists. During that process we got a GRND IDLE light. At this point we suspected that the squat switch had failed. We notified ATC that we did not have an emergency but that we needed to return to the airport. ATC asked the nature of our problem and I told them we had a gear retraction problem. We proceeded with the Approach and Before Landing checklists. When the gear and flaps were selected down we got three green lights and the HYD PRESS and STAB MISCOMPARE lights extinguished. All indications were normal prior to landing except for the GRND IDLE light was still illuminated. We told the Tower that we had normal gear down indications. The Tower dispatched the safety equipment as a precaution. The SIC flew the LOC 6 approach to a normal landing. We were met on the ground by CFR for whom I filled out a brief incident report.