Part 91 of the federal aviation regulations offers pilots flexibility that’s not available to air carriers or charter operators. We can fly at night without a working landing light or venture beyond gliding distance of a shore without so much as a life jacket. We’re not required to carry fire extinguishers or crash axes, and the question of whether to attempt an instrument approach to an airport where the weather’s below minimums is left entirely to our discretion. The fact that these things are legal doesn’t make any of them wise.

About 3:15 p.m. on Dec. 2, 2012, a Piper PA-46-350P Malibu Mirage took off from Destin-Fort Walton Beach, Fla., climbing to Flight Level 210 on its way north.  The pilot, his wife, and another couple were returning home to eastern Indiana after a quick weekend vacation.  The 350-horsepower pressurized single covered the 620-nautical-mile route in less than three hours. At 5:48 p.m., the pilot asked for a lower altitude and was cleared to descend to 14,000 feet. Four minutes later, he requested the GPS approach to Runway 36 at his home field of Greensburg Municipal in Greensburg, Ind. The controller told him to stand by, then cleared him to continue the descent to 11,000 feet. Just before 6 p.m., he was instructed to proceed to PULIC (one of two initial approach fixes), descend to 5,000 feet, and contact Indianapolis Approach.  The Indianapolis controller issued the approach clearance with an altitude restriction of 3,000 feet to the initial approach fix and asked the pilot if he had the current weather. The pilot said he did.

There were two problems with that response. Greensburg doesn’t have its own weather station; the approach plate lists the AWOS frequency for Columbus Municipal 18 miles to the northwest and directs pilots to increase minimum descent altitudes by 40 feet if they’re forced to use the altimeter setting from Indianapolis International instead. Conditions at Columbus weren’t up to approach minimums, or even close.  A METAR archived 10 minutes before the pilot received his approach clearance reported the ceiling as 300 feet overcast, more than 300 feet below the authorized minimum descent altitude of 1,560 feet msl (648 feet agl). Visibility was 1.5 miles in mist.

The pilot’s readback of the instructions for canceling IFR was the last transmission received from him. Radar tracks and data recovered from a handheld GPS both show that the Malibu tracked the inbound course, but started the approach both hot and high. It crossed the initial approach fix at 5,300 feet msl, some 2,300 feet above the assigned minimum altitude, at a groundspeed of 200 knots. By the intermediate fix it had slowed to 170 knots but was still more than 1,500 feet above the appropriate step-down altitude. At the final approach fix, 4.1 miles from the missed approach point, it had slowed to 138 knots and descended to 2,500, the authorized altitude for the intermediate segment. The radar data ended a minute and a quarter later with the airplane established on the final approach course but already 200 feet below the minimum descent altitude. The GPS data continues for another 40 seconds, during which time the Malibu accelerated back to 155 knots. It was barely 200 feet above ground level a third of a mile from the runway threshold, after which it began a gentle climb.

The missed approach procedure calls for a climbing left turn to 2,500 feet and a hold at the intermediate fix, but the Malibu initially veered to the right.  Its groundspeed dropped to 89 knots as it climbed to 1,400 feet, then began a horseshoe-shaped turn to the left. It briefly reached 1,500 feet before commencing a series of erratic turning climbs and descents. After about one minute and 20 seconds, it crashed into an open field three-tenths of a mile east of the runway threshold, shattering the airplane and killing all four on board. Rescuers who responded after the flight was reported overdue described the weather as dark and murky, with ceilings of 200 to 300 feet and visibility less than a quarter mile.

The National Transportation Safety Board concluded that the pilot succumbed to spatial disorientation after descending below the minimum authorized altitude without seeing the airport. The first few minutes of a missed approach are busy at the best of times, and a Malibu is a fair amount of airplane for a low-time pilot to manage in IMC at night. (According to his logbook, he reached 400 hours of total experience during the accident flight.) The sudden acceleration, torque reaction, and changes in attitude can test one’s instrument scan even without having to concurrently reconfigure the airplane for climb, making it easy to get behind the airplane. The Malibu crashed with its gear still down and locked.

Attempting an approach in below-minimum weather isn’t inherently dangerous.  The procedures are carefully designed to provide a reasonable margin of safety—provided they’re flown exactly as specified, with rigorous adherence to course, altitude limits, and the missed-approach sequence. Another pilot flew the same nonprecision GPS approach half an hour earlier, executed the missed, and diverted safely to Columbus where an ILS was available.  The fact that weather wasn’t reported from the destination airport made it less certain that conditions were really too low to get in, but the actual report gave plenty of reason to expect that. A decision to skip the first approach in favor of an immediate diversion to the alternate could hardly have been criticized.