A Raytheon 390 Premier I impacted a highway in Elmina, Shah Alam, after a loss of control while on approach to runway 15 at Sultan Abdul Aziz Shah Airport (SZB/WMSA), Kuala Lumpur. The two pilots, six passengers, a car driver and a motor cyclist on the ground were killed. The flight departed Langkawi Airport at 14:08 LT, bound for Kuala Lumpur-Sultan Abdul Aziz Shah Airport (WMSA) with eight people on board. The PIC was the pilot flying (PF) and was seated on the right, while the SIC, seated on the left side, acted as the non-flying pilot monitoring (PNF). The SIC was not type-rated on the Premier I. The crew managed the aircraft operation without apparent issues. Amid light conversation, the PIC instructed the SIC on various aircraft systems, including communication, navigation, and flight control. In addition to performing PNF duties, the SIC also operated certain aircraft systems as part of the checklist items, such as the weather radar, flaps, landing gear, and spoilers, based on analysis of the CVR recording. As N28JV approached WMSA, the Lumpur Approach air traffic controller instructed it to descend to 2,500 ft and proceed directly to the CE beacon for an NDB Approach to Runway 15. The crew then worked that SIC Approach checklist. N28JV was then handed over to Subang Tower after establishing at 2,500 ft on the NDB Approach Runway 15. Subang Tower instructed N28JV to continue the approach to accommodate a departing aircraft, which the SIC acknowledged. The PIC then asked the SIC to lower the landing gear and flaps, and the SIC complied. At 14:48:36 LT, Subang Tower cleared N28JV to land, and the SIC acknowledged the clearance. At 1,000 ft on final approach, the PIC requested the SIC to run the Before Landing checklist. The SIC proceeded: “check before landing, landing gear down, lift dump unlocked, handle illuminated.” About 0.9 seconds after the SIC said “…handle illuminated,” the PIC acknowledged “lift dump unlocked.” Approximately 1.7 seconds after that, the SIC exclaimed loudly, “woah, woah, woah…, what’s going on?” Multiple alarm sounds followed, including the lift dump aural warning tone, autopilot disconnect alert, and Enhanced Ground Proximity Warning System (EGPWS) callouts such as “minimums, minimums” and “sink rate, pull up, pull up”. The lift dump handle was confirmed to be in the “EXT” position at the time of the crash. Analysis of the CVR recording, crew voices, cockpit sounds, and operational circumstances indicates a high probability that the SIC inadvertently extended the lift dump while performing the Before Landing checklist. This action caused the aircraft to abruptly lose lift, leading to a catastrophic loss of control in flight and resulting in the crash at Persiaran Elmina, Elmina, Shah Alam, approximately 2.7 nm short of Runway 15. Cause. The accident was primarily caused by the inadvertent extension of the lift dump spoilers by the flight crew while performing the Before Landing checklist. Contributing Factors. Contributing factors included deviations from standard operating procedures, inadequate crew training, regulatory grey areas, and deficiencies in communication and decision-making.