IFR Fix: Hold the altitude, forget the autopilot
You were expecting to shoot an RNAV approach in challenging 800-and-2 weather at night. What you got instead, after a flight fraught with glitches and deviations from air traffic control instructions, was weather easy enough to handle with a visual approach.
But is that a good idea?
There’s the added safety of procedural certainty, for one thing, especially if the arrival is taking you to an unfamiliar airport after a long and fatiguing flight.
For a night arrival, flying the IAP is insurance against tangling with hidden obstacles—power lines, for example—on final in the dark.
Also, flying the approach—or for those so equipped, hand-flying it—is just good practice that counts toward maintaining recency of experience, if needed.
For all those reasons, the pilot of a PC–12 single-engine turboprop made the decision to fly a published RNAV approach to bring to an uneventful conclusion a flight during which some of the previous decision making perhaps didn’t measure up to such a high standard.
During the flight’s cruise phase, the PC–12 had suddenly pitched aggressively down, and the autopilot disengaged.
“I immediately grabbed [the] yoke and pitched up and tried to (assess) the situation. During this time the plane climbed about 1000 feet to FL240,” the pilot recounted in a report to the Aviation Safety Reporting System.
There was another pilot aboard, and the two began to work the problem, engaging the autopilot twice more.
“This did not work as it resulted in an even worse altitude excursion and ATC informed us that the traffic space was tight and we needed to hold that altitude and forget diagnosing autopilot.”
Pressuring their decision making was the expectation of “800 feet with snow and 2-4 miles visibility,” at the destination, even though the weather had been improving en route.
Looking back on the flight, the pilot’s evaluation noted other strategies for handling the problem, including making only one attempt to troubleshoot the autopilot, or asking ATC for a cruise clearance—that is, a block of altitude—in which to conduct a more detailed investigation.
Bottom line: “Decided to do approach for safety factor after stress of incident, long day and night conditions plus additional practice [hand flying the] approach.”
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