Terrain Flight

Dennis Dura, Chief Pilot, Ohio Department of Transportation

Terrain flying involves flight close to the surface of the earth. The US Army breaks up terrain flight into nap of the earth (NOE), contour, and low level. NOE is flying as close to the earth?s surface as vegetation or obstacles will permit. Airspeed and altitude are varied in accordance with weather conditions and ambient light. Contour flight is characterized by varying altitude, adhering to the contours of the earth, and a constant airspeed. Low level flight is performed at a constant airspeed and altitude. When performing a reconnaissance, a pilot may go from one technique to another while maneuvering over a route. Even though the US Army tailors its training toward helicopters, there is no reason that an airplane cannot execute terrain flight. As Natural Resource Pilots, it is not a bad idea to evaluate what mode of flight you are going to use after a thorough map reconnaissance. This will allow you time to review what flight techniques may be necessary to safely accomplish the mission. Because of man made or natural obstacles along a proposed route, an airplane may select low level flight, whereas a helicopter may choose contour flight. Weather, rate of closure to obstacles based on airspeed, flight characteristics and maneuvering space all play a part in the differences between an airplane flying contour compared to a helicopter.

Since terrain flight requires more attention to detail and the fatigue factor is high, you must consider human factors such as physical conditioning, creature comfort in the cockpit, physical well being, and attitude. Not everyone has the skill level or inclination to perform terrain flight. A pilot needs to plan in detail and be proficient in maneuvering close to the ground. For example, a pilot relies heavily on his peripheral vision to ensure terrain and obstacle clearance. This requires the pilot to be aware of any blind spots peculiar to the aircraft being flown because of hazards such as wires. Anytime you find yourself near roads, man made structures, or below natural terrain features, suspect wires.

While studying the map, high light all potential hazards and during the flight be ready for surprises. Detection of wildlife and vegetation of interest depends upon altitude, airspeed and weather conditions.

Terrain flight also increases the probability of bird strikes. A single bird will avoid an aircraft, however the aircraft may need to be maneuvered to avoid a flock. Distraction and fixation can cause a pilot to exceed his or the aircraft?s capabilities when trying to avoid the ground or obstacles. Terrain flight demands a fast cross check in and out of the cockpit as well as diversification of attention. Some additional suggestions are avoid flying into the sun, and if visibility is reduced by the weather, reduce airspeed and/or increase altitude. Anticipate loss of altitude in turbulence and vertical thermal air currents. Stay ahead of the aircraft and aviate. Terrain flight can be one more tool you can use to accomplish your missions as Natural Resource Pilots.

LOW LEVEL
Constant Airspeed
Constant Altitude

CONTOUR
Constant Airspeed
Variable Altitude

NOE
Variable Altitude
Variable Airspeed

-Dennis Dura, D.P.E.