Max Trescott examines the tragic crash of a Citation S550, N666DS, in San Diego during an attempted RNAV (GPS) 28R approach to Montgomery Field at approximately 3:46 AM. After departing Teterboro, NJ, and making a fuel stop at Wichita's Jabara Field, the pilot continued westbound overnight.

After refueling, the flight continued to San Diego, where the Montgomery Field AWOS was inoperative, and weather was marginal. The pilot requested weather at nearby airports.

The aircraft correctly crossed the final approach fix PENYY at 2500 feet but then flew below the glide path and failed to stabilize. Speeds decreased from 200 knots to 124 knots on final, increasing workload and destabilizing the descent.

Flight path data suggests the pilot may have flown the approach as if it were a non-precision LNAV approach, mistakenly observing step-downs like the PALOS fix, which applies only to LNAV. Two level-offs occurred—one around 1300–1400 feet, then again at 500 feet—further evidence of a step-down approach profile, inconsistent with a stabilized LPV descent. Ultimately, the jet was 173 feet below LPV minimums and 440 feet below LNAV minimums when it leveled at 500 feet before crashing.

The autopilot appeared to be disengaged near the end, with irregular lateral path and a brief climb after leveling at 500 feet. Fatigue may have played a significant role, as the pilot had been flying for over 7.5 hours and the crash occurred at 3:45 AM Pacific (6:45 AM Eastern), squarely in the circadian low period when alertness suffers.

Max points out that older aircraft like this 40-year-old Citation often have non-intuitive or limited autopilot functionality for RNAV approaches. Social media commenters speculated the aircraft may have had either a non-WAAS FMS providing limited vertical guidance, or a Jet Tech STC'd Garmin 750 setup requiring autopilot workarounds. Either case complicates RNAV approach execution—especially when the pilot is tired.

Given the ILS 28R approach was available and offered the same minimums, Max questions why the pilot didn't choose it. Even older autopilots generally handle ILS approaches more reliably than LPV. He concludes that while RNAV approaches are preferred in modern aircraft, an older jet with dated avionics at night, may warrant choosing the simpler, more robust ILS option.

Max reiterates a fundamental safety takeaway: Always tailor your approach to the aircraft and situation. What works best in a G1000 or G3000 might not be safe in a 1980s-era Citation. And never underestimate the risks of fatigue, especially during early morning hours.

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