Cessna 441 Pilot reported a left main landing gear failure on landing. The aircraft became uncontrollable and departed the runway resulting in damage from colliding with runway lights. The aircraft was removed from the runway and taken to a hangar for maintenance action.

Narrative

We were conducting a practice no flap landing to the ZZZ Runway XX. The aircraft was on final with gear down; no flaps and airspeed 15 kts. above normal approach speed; 135 to 140 KIAS. On short final the PIC reduced our airspeed to 115 KIAS; which is the procedure outlined in the POH; and maintained that airspeed until main gear touchdown. The landing was really good; on speed; on center line and the flare was correctly accomplished with no float and excessive sink. The landing was normal and the nose gear was gently lowered to the runway. It's when the nose gear contacted the runway and the power levers were positioned to ground idle when we encountered the problem. We started to feel a shimmy in the aircraft; nose up elevator pressure was applied to see if it was a nose wheel shimmy or not. The shimmy continued and then we had a partial collapse on the left side. I thought the left main tire had blown and the aircraft started to veer to the left. The flying pilot stated that the aircraft was going left and they could not get it back to the right. At that time he had both engines in full reverse; full right rudder and was applying the brake on the right side. I reached up and took the left engine out of reverse and placed it in the ground idle mode. That seemed to stop the left veer and we were paralleling the edge of the runway; this was indicated by the skid marks. At this point both engine condition levers were in take-off; climb and landing position which is 100% N1. Since the PIC was struggling with the aircraft; and we were very close to the edge of the runway; I positioned the engine condition levers to start and taxi; or 65% N1. The aircraft then veered to the left with the left propeller striking a runway edge light. After the left main gear was in the grass the aircraft started to straighten a bit but by this time the entire aircraft veered into the grass and the right propeller then struck another runway edge light. We came to a stop about 15 ft. from the edge of the runway; I immediately positioned the condition levers to emergency cut-off. The flying pilot secured the aircraft and I exited through the main cabin door to inspect for leaking fuel or a possible fire. None was noted. The first thing I noticed was the left main tire had not blown but the landing gear assembly had partially collapsed. The PIC then exited the aircraft; we made sure that we were both ok; and we both looked around the aircraft for possible fire issues; again none were noted. (Crash Fire Rescue) CFR then showed up and positioned the fire truck for a possible fire. The aircraft did start to leak a small amount of fuel from the left wing vent; I believe this was due to the left wing low position of the aircraft; we had around 2000 lbs of fuel onboard. A bucket was placed under the vent to collect the dripping fuel. Upon inspection of the left main gear assembly it was noted that the left main gear trunnion had broken. A local Mechanic pointed out an Airworthiness Bulletin indicating the identical break in the main landing gear trunnion. We called the appropriate agencies to report the incident; made sure the aircraft was secured and a plan was in place to get the aircraft moved from the side of the runway. The PIC and instructor then debriefed the incident and covering what went well; what did not go well and what we could do better in the future. There were no injuries and the only damage to the aircraft was that both propellers had a strike to the edge lights and the left gear area was damaged.