Obscured Vision Leads to Fatal Air Crash? CFIT Again?

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I’m scratching my head on this one.

A recently released NTSB preliminary report on the fatal crash of a single-engine Cirrus SR-22 in Utah states that moments before the crash the plane was above 13,000 feet mean sea level (MSL) in the midst of clouds between 9,000 and 27,000 feet MSL. Light rain was reported. Both the pilot and his wife were killed in this July 14th crash. A local newspaper speculates that the pilot’s vision was obscured.

The beautiful terrain of Fishlake National Forest where, two weeks ago, a pilot flew his single-engined plane into a ridge. Photo: Wikipedia

The Cirrus SR22. Photo: Wikipedia

That sounds about right — a pilot who is in clouds and in precipitation typically has obscured vision. That’s where the aircraft’s instruments come to the fore, allowing a “blind” pilot to safely fly through clouds and many types of precipitation. However, not every pilot is rated to fly using only the aircraft’s instruments.

The confusing part to me is why was this pilot flying in clouds? Worse, flying in clouds and precipitation? The preliminary NTSB report does not list the pilot’s qualifications or his familiarity with his aircraft. The report also states there was no flight plan filed with the FAA. Though a filed flight plan is not required, it restricts the pilot to Visual Flight Rules (VFR). Under VFR, the pilot must be able to always operate the aircraft with visual reference to the ground, and by visually avoiding obstructions and other aircraft. VFR pilots are not allowed to fly into clouds; IFR pilots can. At the same time, one of the most valuable benefits of a filed flight plan is emergency tracking: if you don’t show up when and where your flight plan says you will, an emergency search is initiated.

Though the NTSB report stated that visual and instrument meteorological conditions prevailed along the route of flight, there aren’t enough details to analyze the specific meteorological conditions involved in the crash, but I can make some educated guesses. Looking at some of the ImpactWeather surface charts from the 14th, there was a cold front in northwestern Utah with a trough of low pressure extending southeastward into central Utah near the crash site. Along both the frontal system and the trough, our forecast included thunderstorm and rain shower activity. Though clouds and storms would be much more pervasive along the frontal boundary, there were likely breaks in the clouds along the trough and near the crash site. Traveling eastward from California to Colorado (the flight was bound for Aspen), this would likely have been the only area of problematic weather.

The SR22 has a sophisticated cockpit including the Avidyne primary flight display. Photo: Wikipedia

Again, the NTSB report states cloud bases of 9,000 feet MSL and the aircraft’s flight level was just above 13,000 feet MSL.  However, these altitudes are indicated as mean sea level and must be adjusted to AGL (above ground level) — a calculation every pilot knows how to make. Additionally, the aircraft’s altimeter must be calibrated for mean sea level pressure (MSLP) — the measurement reported in all weather observations. This is critical not only to an accurate reading from the aircraft’s altimeter, but to a total understanding by the pilot of true altitude over the ground below. The crash was reported to be in Utah’s Fishlake National Forest (FNF). A quick look at area topographic maps shows heights of 8,500 feet MSL and higher around the crash site. In other words, and depending on atmospheric pressure, a 9,000 MSL cloud base could be significantly lower measured in AGL over the mountains of Fishlake. A VFR pilot finding himself suddenly in the clouds over Fishlake on the 14th could find himself in a very dangerous situation. Even more confusing, cloud bases and ceilings in official weather observations are recorded and disseminated in AGL, not MSL. Could the pilot have been confused? Could the altimeter have been adjusted incorrectly? This sounds like a  CFIT incident.

Headlights from emergency vehicles illuminate the crash site that took the lives of six last November in Arizona's Superstition Mountains. Photo: Wikipedia

Controlled flight into terrain (CFIT) indeed occurs in areas of elevated terrain. Add in obscured vision from clouds and/or precipitation and deadly results are often unavoidable. The NTSB report states the crash site was on a northern slope of a ridgeline in FLNF. Seems like it could be CFIT. Since this crash happened at 11:30 AM local in broad daylight, it would seem the pilot found himself unexpectedly in clouds and, perhaps because of an improperly set altimeter, unexpectedly too low. A combination of errors that’s not unusual. It’s also possible low level windshear (LLWS) or a microburst from a nearby thunderstorm contributed to the crash. Microbursts can be deadly to large and small aircraft when they’re near the ground, no matter if flying in mountainous terrain or on a controlled approach to an airport (read my article on the crash of Delta Flight 191 here). There was no mention in the report if the aircraft was equipped with a GPS-driven terrain data base system which can alert the pilot to dangerous terrain.

It was not even a year ago when a probable (the NTSB report is not final) CFIT incident took six lives when the straight and level flight of a small airplane crashed into the rugged Superstition Mountains near Phoenix. And it was 67 years ago this Saturday when a B-25 Mitchell bomber flew straight into the Empire State Building while in dense fog. This crash took the lives of 14 and was ultimately attributed to the pilot who disregarded instructions from air traffic control and became disoriented in the fog. Next week will be the 15-year anniversary of the CFIT incident involving Korean Air Flight 801. The KA 747-300 flew straight into a mountain killing all 228 persons on board and was blamed on several factors including pilot fatigue, an improperly trained crew and altitude warning systems that had been deliberately modified to be less sensitive.

The Empire State Building was left smoldering after a B-25 hit the building between the 78th and 80th floors on Saturday, July 28, 1945. The building was open for business the following Monday. Photo: Wikipedia

The official report on the Fishlake National Forest crash is likely many months or even a year away. Until then, we can only speculate. However, an experienced instrument-rated pilot will typically file a flight plan for such a long cross country flight. As this pilot was flying such a flight as VFR, I suspect he was not instrument-rated. Though less experienced than IFR-rated pilots, VFR pilots should be experienced enough to know to steer well away from questionable weather (even a dark cloud should be considered “questionable”). Why was this VFR pilot in clouds?

Even if it is ultimately proved that the crash was caused by a mechanical issue, it was a fatal mistake for this pilot to be caught in clouds, near thunderstorms and in mountainous terrain.

 

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