October 2015 Issue

Get Some Air Under You

Since we usually can’t see unlit objects at night, there’s an increased risk of controlled flight into terrain, CFIT, and the plain, old-fashioned collision with an obstacle. One way to help minimize the risk of CFIT at night is simple: fly higher. And one way to do that is use IFR minimum altitudes even when VFR.

The two screenshots at right, of the same area near the Virginia/West Virginia border, provide a good example. The sectional chart in the upper image depicts 5100 feet as the maximum elevation figure (MEF) for the quadrant and is circled in red. A close look at the spot elevations nearby, also circled in red, show why.

Meanwhile, the low altitude en route chart at bottom dispenses with the topographical clutter but does a much better job recommending safe altitudes for flights passing through the area. The off route obstruction clearance altitude (OROCA) for the same area is 7200 feet. The OROCA is computed similarly to the MEF but provides an additional buffer of 1000 feet in non-mountainous areas and 2000 feet in designated mountainous areas within the United States.

Missing the terrain by 100 feet or by 1000 is still a miss. But what happens if you forget to switch tanks, the engine sputters and you descend a few hundred feet before it recovers? Better to be higher.