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Just enoughJust enough

New instrument pilots may be surprised to find that the rating is apt to make decision making more difficult rather than easier. Ceilings and visibility that would ground a VFR flight—no discussion, no controversy—instead open up a whole new set of questions: How low is it forecast to get? How far is the nearest good alternate? How sharp are my skills today—really? And what besides guy wires and granite might be lurking in those clouds? Turbulence? Embedded thunderstorms? Ice?

Likewise, incremental improvements in a light aircraft’s capability increase the options available to its pilot—thereby creating a whole new set of decision points, each with its own opportunity to make the wrong choice. Lack of familiarity with the principles and limitations of that equipment compounds the peril. Moderate precipitation can obscure the view of truly nasty cells farther ahead from the low-power signal and small antenna of a typical on-board radar installation. Nexrad downloads provide a more comprehensive picture, but it’s of where the weather was maybe 15 or 20 minutes ago. Mistaking that for where the weather is now has led to tragedy. And anti-ice systems, even those approved for flight into known icing, are only intended to buy enough time to get out of the ice again in a reasonably orderly fashion.

Just after midday on April 27, 2010, the pilot of a Model 58 Beech Baron contacted Indianapolis Center to request a higher altitude “for weather.” The Baron was about halfway from AOPA’s home base of Frederick, Md., on an IFR flight to Olive Branch, Miss., just south of Memphis. The pilot was cleared to climb and maintain 12,000 feet, but after 10 minutes at that altitude he contacted center again. This time his request was for a lower altitude due to “problems” with his airspeed indicator. He made further reports of airspeed anomalies during his descent and never leveled off; the last transmission received from the Baron was "just went down like an absolute rock—don't know what happened." It disappeared from radar at 12:25 p.m. Seven hours passed before authorities received reports of a crashed airplane on a hillside in the Daniel Boone National Forest outside Bear Branch, Ky. Search crews needed two more hours to reach the site, but the delay did no harm to the 68-year-old pilot or his wife. Both were killed outright by the near-vertical impact.

The normally aspirated 1981 Baron was equipped with factory-installed alcohol windshield, propeller anti-ice systems, and pneumatic boots installed under a supplemental type certificate (STC), a combination the NTSB judged to have provided known-ice certification. (This assessment has proven difficult to confirm.) Its pilot held a commercial certificate with single-engine, multiengine, and instrument ratings, and his logbook showed 1,545 hours of flight experience, including 104 in the accident airplane and 134 hours in actual instrument meteorological conditions. The day’s weather was enough to put them both to the test. A cold front along the route produced “an extensive area of clouds and precipitation,” combining low ceilings with tops forecast to reach 22,000 feet. Actual satellite images showed nimbostratus clouds whose tops reached 27,500 feet near the accident site; the freezing level was at 6,000 feet. An Airmet Zulu for moderate icing between 5,000 and 16,000 feet—including an 80-percent chance of ice between 9,000 and 11,000 feet—was corroborated by “numerous pilot reports” of light to moderate rime and mixed ice up to 15,000 feet. The pilot had been advised of the airmet during his weather briefing.

The investigation found evidence that adequate fuel was on board, but both engines were operating at low or no power at the time of impact. (This might have been consistent with attempted recovery from a nose-low unusual attitude.) Sections of the boots were found inflated, indicating they were operational. Curiously, though, the NTSB’s report makes no mention of the status of the pitot heat, either the position of the cockpit switch or the functional condition of the heating element. As new instrument pilots will remember (but more experienced ones might forget), a blocked pitot tube will cause the airspeed to go to zero if the drain hole remains clear, allowing ram pressure to escape. If both the ram port and drain hole are plugged, the trapped pressure will make the airspeed indicator mimic an altimeter, indicating higher speeds as the airplane climbs and lower ones as it descends. Failure to recognize this can lead the pilot to stall the airplane pitching up, or dive it into the ground.

On learning of the accident, another Frederick-based pilot—a career professional with many thousands of hours in dozens of aircraft types—sighed and shook his head. A known-ice Baron, he said, is an airplane “just capable enough to get you into real trouble.” He has a point. Without the illusory security of known-ice “protection,” it’s doubtful the accident pilot would have attempted that flight on that particular day.