Plane & Pilot
Saturday, April 1, 2006

Avoiding CFIT

Despite constant warnings, controlled flight into terrain continues to vex general aviation pilots

With the CFIT risk augmenters in mind, pilots should be able to make the proper adjustments to their preflight planning and en route decisions. When developing a flight plan, do a thorough terrain evaluation, particularly if you’re unfamiliar with the area. New computer flight-planning programs can facilitate this with ease. This topographical analysis should take into account the departure airport area, the climb path, route at cruise, the descent conduit and the arrival airport and its surroundings. By knowing where the terrain is and being clued in to what the minimum clearance altitudes are, you shouldn’t ever be caught off guard by a hill or tower.

During this examination of the flight route, aircraft performance needs to be checked. A pilot who doesn’t check takeoff and landing charts isn’t just a fool, but is disobeying the FARs. Someone who doesn’t consider climb rates after takeoff and en route performance is tempting fate. Let’s say you’re taking off out of Alamogordo, N.M., (elevation 4,200 feet) and you’re planning to fly due east to avoid the multiple restricted areas in the vicinity. Within four miles of the airport, the terrain rapidly rises up to over 8,000 feet. There aren’t many GA aircraft that can comply with a climb gradient (different than rate of climb) of 1,000 fpm at sea level, let alone at altitude.

So you’re a smart enough pilot to know that you’ll need to climb to the west in the flatlands prior to heading east. But what about the mountains beyond the airport that saliently poke up to 10,000 feet? Simply fly a couple thousand feet above that; no biggie, right? Well it depends. Let’s say that the typical mountain concerns (wave activity, obscuration, etc.) aren't a factor. One of the most common trepidations that many GA fliers have at these altitudes is related to oxygen requirements. Oxygen is an important factor, but just as epochal is aircraft performance.

Depending on the model, a Cessna 172 has a service ceiling of 13,000 feet under ideal conditions. To determine the actual service ceiling, one needs to check the temperature aloft—perhaps it’s 10 degrees above standard. The aircraft climb rate would thus become marginal (100 fpm) at around 11,000 feet, which doesn’t leave much insurance. Of course, all of these service-ceiling calculations should be taken with a grain of salt—they ignore the fact that the engine has probably been beaten up quite a bit throughout its lifetime and has likely experienced the degrading effects of, say, turbulence. Neglecting to premeditate these factors is poor SA.

Losing track of where you are also results in a collapse of SA. Though there’s really no excuse for losing SA, the moving-map GPS negates any possible rationalizations. By knowing your exact position and, through your diligent preflight planning, knowing the attributes of proximate obstructions, CFIT should be wiped out altogether (wishful thinking, I know). And if keeping track of your location seems a bit too trying with the aforementioned methods, there’s even better technology available.

The cutting-edge Terrain Awareness and Warning System (TAWS) has been invading GA cockpits for a while now. And it’s quickly becoming more affordable. TAWS endlessly performs GPS position vs. elevation analyses and presents the results to the pilot on a visual display of intuitive colors (yellow represents a terrain caution and red is a warning). Aural warnings are also provided to keep even the most situationally unaware pilot alert. Other technological tools are out there, such as Chelton’s synthetic vision system, which displays terrain contours on the pilot’s primary flight display. Though, as with any other new cockpit contrivances, pilots shouldn’t become over-dependent on these tools.

With all this CFIT talk, one might argue that GA flying is rather dangerous. But consider what CFIT really is and what typically causes it—a pilot flies the plane into ground that he or she didn’t know was there. If you know where you are and where the terrain is, your safety is assured. GA flying is as safe as you’re willing to make it. By effectively planning your flight and keeping track of your position, you can be certain that you’re not going to see any mountain goats from the vantage point of the cockpit.

Labels: CFITFlight HazardsSafety


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