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(ERA12FA030)(ERA12FA030)

By David Jack Kenny

Sometimes it’s easy to distinguish individual links in the chain of events leading to an accident, but other wrecks seem to defy explanation. In 2008, a Piper Cherokee Six flew directly into a Nevada mountainside in the middle of a clear summer afternoon, killing everyone on board. Modest detours to either the left or right would have kept it safely over lower ground. Why did this happen?

Just as inexplicable was the Oct. 16, 2011, crash of a Cirrus SR22 on final approach to Runway 26 of the Danbury, Conn., Municipal Airport. In good visibility under high ceilings at night, the airplane flew directly into a tower—and not just any tower. The Cirrus hit a hazard beacon installed to warn pilots of a hill under the final approach course. A witness confirmed that the beacon’s red lights kept flashing right up to the moment of the collision that killed the solo pilot. Both the witness account and GPS track data retrieved from the airplane’s remote data module (RDM) indicate that he made no attempt to avoid the structure, which was well below the usual visual descent profile: 292 feet above field elevation, three-quarters of a mile from the runway threshold.

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The 64-year-old pilot had bought the airplane new three years earlier. He held a private pilot certificate with instrument rating for single- and multiengine airplanes and had logged a little more than 2,600 hours of total flight time; in the past two years he’d flown almost 200 hours in the Cirrus. His logbooks did not record any previous flights to Danbury.

He came up from Easton, Md., on an IFR flight plan. After he reported the field in sight, New York Approach cleared him for the visual and transferred him to the Danbury tower, which instructed him to report midfield on a right downwind. Shortly afterward he was cleared to land, and his last transmission was a readback of the landing clearance. Both the radar track and data recovered from the RDM indicate that he made a 45-degree downwind entry to a right-hand traffic pattern, turning base and final at appropriate points. Radar contact was lost below 1,400 feet msl, but the GPS data show that the Cirrus completed the turn to final at 1,211 feet msl, 663 feet above field elevation.

Once established, though, its descent was unusually fast for an airplane on a one-and-a-half-mile final. The GPS recorded the Cirrus losing 358 feet over the next 15 seconds, a rate of 1,432 feet per minute. Its descent moderated at that point, but continued. The airplane lost another 106 feet in the final 10 seconds before impact.

Examination of the wreckage suggested, and monitoring data recorded by the RDM confirmed, that the engine operated normally throughout. The fuel pump still contained 100 LL, and control continuity was confirmed up to the fractures caused by the collision. There was no evidence of any mechanical failure that might have compromised airplane performance or control.

So what happened? The NTSB’s report notes that the threshold of Runway 26 is displaced 734 feet because of that same hill. It has runway end identifier lights but no visual approach slope indicator. Trying to pick out the threshold among the other lights on the ground without benefit of any external descent guidance, it’s possible that the pilot didn’t realize he was low. It’s even possible he didn’t notice the hill, which would have been below his line of sight to the runway. But it’s hard to imagine why he didn’t see the flashing red hazard lights as he flew directly toward them.

The final paragraph of the NTSB report hints at one other possibility. It notes that the airplane was equipped with a terrain awareness warning system that would have sounded a routine alert as the airplane descended through 500 feet agl toward an airport—and also synthetic vision. Both were turned on, and relied on the same database. It showed the hill under the final approach course but did not depict towers less than 200 feet tall. The one supporting the hazard beacon was about half that high.

Is it possible this pilot decided to fly the traffic pattern using synthetic vision instead of the old-fashioned kind? One can see a certain novelty appeal in the idea. Or might he have simply been using it as an aid, trying to de-clutter the view through the windscreen? There’s no knowing—but his unerringly straight path into the warning lights would be easier to understand if his eyes were on the panel instead of out front.