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Bad decisions below minimumsBad decisions below minimums

CHI06FA232CHI06FA232

When the ceiling is low and visibility poor, circling approaches can be one of the most challenging aspects of instrument flying. The higher descent minimums and the need to maintain visual contact with the runway while maneuvering can lead to some ill-advised flying to avoid going missed. Even in a nimble, single-engine trainer, an extremely tight, low pattern can be difficult to fly. Try one in a twin, below minimums, and the results are apt to be tragic—even for a multiengine instructor.

On Aug. 14, 2006, a Piper PA-23-250 Aztec crashed during a circling approach at Chippewa County International Airport in Sault Ste. Marie, Mich. The pilot, a 1,000-hour multiengine instructor, was attempting a knife-edge turn back to the airport after flying downwind at 200 feet agl, 600 feet from the runway (laterally). The instructor, his student, and two passengers were killed.

At about 6:30 on the morning of the accident, the flight instructor called Green Bay Automated Flight Service Station to file an IFR flight plan and obtain a weather briefing. Marginal visual conditions with areas of IMC prevailed along the route of flight. The forecast weather near the destination airport was VMC. The briefer also informed the instructor that Runway 16/34 at the destination airport was closed for service. Runway 16/34 is the primary runway at Chippewa County Airport and the only one served by a precision approach.

The aircraft left Waukesha County Airport in Waukesha, Wis. at 7:11 a.m. and proceeded without incident for an hour and a half. At 8:40 a.m., the instructor reported having the current weather at Chippewa County (visibility three miles, scattered clouds at 900 feet agl, overcast at 3,500 feet agl). Nine minutes later, he requested the VOR-A approach, landing Runway 27, which ATC approved.

At 9:08 a.m., the instructor reported crossing the Sault Ste. Marie VOR inbound on the approach. ATC told him to change to the unicom frequency and cancel his flight plan after landing. The pilot acknowledged the clearance, stating “I’ll cancel on the ground; still IMC.” It was the last radio call received from the aircraft.

The Chippewa County Airport elevation is 800 feet msl. According to radar data, the Aztec tracked the 218-degree radial inbound and descended below the approach’s authorized minimum descent altitude (MDA) of 1,260 feet msl about two and a half miles northeast of the airport. The aircraft leveled off about 200 feet below MDA until crossing over the intersection of Runway 9/27 and Runway 16/34. The Aztec then made a descending left turn to the east, paralleling Runway 27 about 600 feet to the south at 985 feet msl.

At 9:16 a.m., the Aztec’s last radar return was recorded about a half mile east of the Runway 27 threshold. The wreckage was discovered 725 feet north of this position. Numerous witnesses reported seeing the airplane traveling eastbound at about 150 to 200 feet agl before attempting a steep left turn back toward the airport. Several of those witnesses reported that the airplane reached a bank angle of nearly 90 degrees before plunging nose first into the terrain.

Weather conditions at the time of the accident had deteriorated to visibility one-and-a-quarter miles, sky overcast at 300 feet agl. The NTSB determined that the crash resulted from the instructor’s failure to maintain aircraft control during the circling approach and his failure to perform a missed approach when the airplane was no longer in a position to land using normal flight maneuvers. Contributing factors included the pilot’s decision to operate below the approach’s MDA before having the runway environment visible, as well as the low ceiling and visibility.

No doubt the low ceiling surprised the accident pilot as he descended on approach. The forecast had called for VFR weather near Chippewa County Airport. The 8:35 a.m. automated weather observation, which the pilot had received, hinted at deteriorating conditions but was still well above minimums.

By 9:15 a.m., the ceiling had dropped to 300 feet agl—160 feet lower than the MDA for the VOR-A approach. Rather than executing the missed approach, the pilot continued down another 200 feet before he broke out of IMC. Now dangerously low, he attempted to salvage the circling approach by putting the twin through maneuvers that simply defied the laws of aerodynamics.

Weather is fickle, and pilots should always be prepared for unexpectedly poor conditions. Even when we expect to drop out of the soup well above MDA, we need to be ready—and willing—to go missed. Descending below authorized minimums is never wise, even when shooting a straight-in, precision approach at a familiar airport. Busting the MDA and then attempting to circle to land is an invitation for disaster.