There was an unfortunate reminder last week that the high skies, despite a former United Airlines advertising slogan, are not always that friendly. A Cessna 421C on an IFR flight from Louisiana to Florida failed to respond to a Center frequency change and began to circle, inexplicably, as shown in the image. All comments here are purely speculative until the accident report is completed, although my hunch is it will read something like, “Pilot incapacitated, probable cause undetermined.” Recovery of the Golden Eagle is unlikely since it is reportedly in deep water in the Gulf of Mexico.
It is exceedingly rare for pilots to become incapacitated due to an unnoticed pressurization fault. We are trained to go on oxygen immediately before doing anything else and then to start an immediate descent. There are only two GA accidents that I can recall that fit this profile: Golfer Payne Stewart in a Lear 35 (1999) and Bo Rein, the Louisiana State football coach who was lost when a Cessna 441 went off course on autopilot, climbed to more than 41,000 and flew for several hours before spiraling into the Atlantic (1980). Both the Stewart and Rein flight profiles looked similar—aircraft flew in a relatively straight line until fuel exhaustion brought them down. Altitudes were fairly stable.
The flight path in this accident, involving a 65-year-old pilot, looks different with circling and multiple altitude excursions. In all these cases, military aircraft intercepted the target aircraft and noticed there was no response. The cabin windows were fogged over indicating a possible pressurization fault. I asked David Kenny, the Air Safety Institute’s database manager, to do a little research and to speculate with some other AOPA staff pilots on why the flight path looked as it did. You can add your own thoughts:
- The pilot recognized the loss of pressurization in time to disconnect the autopilot, but not in time to actually manage the descent. If he was holding the yoke when he lost consciousness, that might explain the initial right turn which would be consistent with a turn back toward Louisiana. Any deflection of the yoke or asymmetric thrust after he lost consciousness would have been enough to produce circling flight. As long as the airplane was trimmed level or nose up, it would have more or less maintained altitude or gradually climbed until it stalled.
- The autopilot was set to wing-leveller mode without altitude hold.
- The autopilot was tracking away from a VOR and reverted to wing-leveller mode once VOR reception was lost. This is consistent with the track, which was following a radial from the Leesville (LEV) VOR when the wandering began. The flight plan had been filed as “/G,” but we don’t know whether he was navigating by VOR or GPS at the time. Again, we’d have to assume that it wasn’t set for altitude hold.
Another mystery involves the reportedly “gentle” splashdown after the aircraft ran out of fuel.
The FAA sums up the best practices in the advisory circular AC 61-107A OPERATIONS OF AIRCRAFT AT ALTITUDES ABOVE 25,000 FEET MSL AND/OR MACH NUMBERS (MMO) GREATER THAN .75. It’s a good review.
Here are a few reminders:
The time of useful consciousness at FL270, the flight’s filed altitude, is about three minutes if the cabin suffers a slow decompression and about half that with a rapid decompression. There is an annunciator light to warn the pilot, and there are some physiological signs such as euphoria, sweating, headache, fatigue, tunnel vision, hot flashes, etc. The lack of oxygen affects all of us a bit differently.
When in doubt, quickly don the mask (cannulas are OK below 18,000; you did remember to check mask/cannula before takeoff and that there is adequate supply?) and then figure out what happened. Those of us who don’t fly the flight levels still need O2 for prolonged flight above 10,000 (5,000 at night), although using it at lower altitudes couldn’t hurt, and may in fact be necessary if lack of sleep, age, smoking, and other habits are causing a hypoxic condition before ever leaving the ground. It’s better for your brain and your alertness level. There are a number of mishaps where a perfectly capable pilot does something unexplainable where oxygen deprivation seems as likely as many other answers, and it’s easy to remedy!
Our condolences to the family and friends of this C421 pilot—unexplained accidents are always unsettling.