The production "Su-27K" featured the required strengthened landing gear with a two-wheel nose gear assembly, folding stabilators and wings, outer ailerons that extended further with inner double slotted flaps and enlarged leading-edge slats for low-speed carrier approaches, modified LERX (Leading Edge Root eXtension) with canards, a modified ejection seat angle, upgraded FBW, upgraded hydraulics, an arresting hook and retractable in-flight refuelling probe with a pair of deployable floodlights in the nose to illuminate the tanker at night. The "Su-27K" began carrier trials in November 1989, again with Pugachev at the controls, on board the first Soviet aircraft carrier, called "Tbilisi" at the time and formal carrier operations commenced in September 1991.