with gear down and locked
I hope you only mean "three Greens" type locked. I once had the pleasure of ferrying an F27 to its engineering base. It had suffered a gear retraction on landing (another story) and had been repaired sufficiently well to fly; on a 24 hour permit. The engineers wanted it to fly with the ground-locks in. "No way, Jose". If I lost an engine on take-off, I wanted that gear retracted, and we talk about engineering damage back on the ground.