Cessna 425 Conquest I, Lone Tree, Colo., Aug. 13, 2005–The NTSB determined that the cause of the accident was the pilot’s failure to properly execute the published instrument approach procedure.
Conquest N425SG was making a night ILS approach to Runway 35R at Centennial Airport (APA) when it crashed, killing all four occupants. The airplane was destroyed by fire. On vectors in the terminal area, the pilot’s keying of the microphone and the timing of his speech showed decreased coordination during approach.
The airplane deviated above and below the glideslope, and left and right of the localizer. The 5,000-hour pilot had read back the clearance, and the controller asked if he were “starting down on the altitude.” The pilot responded in the affirmative. At 8,500 feet and with a groundspeed of 170 knots, the airplane was at the outer marker. The controller reported a 500-foot ceiling and said he was getting a low-altitude alert. The pilot acknowledged that he was low but then said, “I’m back on glideslope.” That was his last transmission.
Toxicological tests showed bupropion (to quit smoking) and anti-anxiety drugs in the pilot’s body. He did not hold a valid medical certificate at the time of the accident.