Air Safety Institute Safety Spotlight
Circling below minimumsWhen the ceiling is low and visibility poor, circling approaches can be one of the most challenging aspects of instrument flight, and they can lead to some ill-advised attempts to avoid going missed-approach. 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 could be tragic--even for a multiengine instructor (MEI).
On August 14, 2006, a Piper PA-23-250 Aztec crashed during a circling approach at Chippewa County International Airport in Sault Ste. Marie, Michigan. The pilot, a 1,000-hour MEI, was attempting a steep turn back to the airport after flying downwind at 200 feet agl, 600 feet laterally from the runway. The instructor, his student, and two passengers were killed.
The aircraft was en route from Waukesha County Airport in Wisconsin. At 8:40 a.m., the instructor reported having the current weather at Chippewa County (visibility three miles, scattered clouds at 900 feet, overcast at 3,500 feet). 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, still in instrument meteorological conditions (IMC). According to radar data, the Aztec descended below the approach's minimum descent altitude (MDA) of 1,260 feet msl about two and one-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. Chippewa County Airport elevation is 800 feet msl.
The Aztec's last radar return was recorded about a half-mile east of the Runway 27 threshold. Witnesses saw the airplane attempt a steep left turn back toward the airport, reaching nearly 90 degrees of bank before it plunged nose first into the terrain. The National Transportation Safety Board (NTSB) determined that the crash resulted from the instructor's failure to maintain control during the circling approach and his failure to perform a missed approach when he could no longer land using normal flight maneuvers. A contributing factor was the pilot's decision to operate below MDA.
No doubt the low ceiling surprised the accident pilot as he descended. The forecast had called for VFR weather near Chippewa County Airport. The 8:35 a.m. automated weather observation 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.
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. Busting the MDA and then attempting to circle to land is an invitation for disaster.
An aviation technical writer with the AOPA Air Safety Foundation, Carl Peterson creates interactive courses and other safety education materials for the aviation community. He has been flying since 1989.
By Carl Peterson