C182RG passenger reported landing gear collapse on landing.

Narrative

Owner/Pilot of the aircraft and a Myself planned to depart ZZZ at XA30 on a local flight with the intent of exercising his skills in operation of a new Garmin Avionics suite. Due to my prior experience with similar systems on various other aircraft; I obliged to offer my personal input. The Flight route was ZZZ to ZZZ1 to ZZZ2 to ZZZ3 to return to ZZZ. The flight was completed at all times in VMC conditions under VFR flight rules. I arrived at the aircraft; and the owner/pilot had pulled the aircraft out of the hangar and confirmed he had completed a preflight. I did a secondary walk-around and boarded in the right seat. We departed from ZZZ approximately XA45 local time from Runway XXL. We initially had planned to depart towards ZZZ1 from the East side of the airport in order to deconflict with traffic practicing approaches on XYR. A left downwind departure to the East/Northeast was executed en route to ZZZ1. ZZZ4 Tower approved a transition 'along the beeline' through their airspace Northwest bound. Approaching ZZZ1 the airport traffic pattern was full and the pilot opted to turn back towards ZZZ2 then continue to ZZZ3. A long final to Runway XZ at ZZZ3 was joined. At 5 mile final the aircraft was configured to land. A normal approach; landing; and departure was made at ZZZ3 Runway XZ. After the departure from ZZZ3 we planned to return to ZZZ. While we were 15 miles to the West; we observed there were multiple aircraft on the approach course to Runway XXR. In order to separate safely with the other training aircraft; while on a 10 mile final to Runway XXR; the pilot slowed the aircraft; selected Flaps 10 degrees; and lowered the gear. The C182RG has only one gear light indication. After selecting 'Gear down'; the aircraft slowed; and a green indication was observed. The approach was made in a normal manner. With power reduction no warning horn was heard; all indications seemed normal. With a very light left crosswind; an approach to landing on Runway9R was standard; power was reduced and a flare was commenced. While in the flare while landing on XXR the left main gear made contact. Soon after; the right main landing gear made contact. Upon contact the pilot continued to add back pressure at which point the aircraft seemed to jolt and scraping metal was heard. The aircraft slid to a stop and rested in the grass on the right side of Runway XXR at the intersection of the Runway and Taxiway 1. Airport authorities and the FAA were notified. No injuries resulted. These are the events from my perspective in the right seat of the 182.