Invisible obstacle 

One of the hardest things in life (and aviation) is the purely random tragedy where those who pay the heaviest price haven’t done anything wrong. A car going the other way on a divided highway loses control and crosses the median, or a spacecraft explodes beneath its crew. College students are murdered by a fellow student they didn’t even know.

The death of a 58-year-old crop duster on Jan. 10, 2011, was one of those random tragedies—and like many others, it could have been prevented. The 26,000-hour commercial pilot was killed when his Rockwell S-2R hit an unmarked meteorological evaluation tower (MET) while he was treating a field in Contra Costa County, Calif. Witnesses confirmed that he made a reconnaissance pass before beginning the application, but the tower was bare metal, unpainted, and not marked by any lights, flags, or other warning devices. The NTSB quoted an article by the National Agricultural Aviation Association (NAAA) which observed, “The fact that these towers are narrow, unmarked, and grey in color makes for a structure that is nearly invisible under some atmospheric conditions.” According to the witnesses, he made no apparent attempt to avoid it before the impact.

The tower had been erected in April 2009 “for wind resource measurements.” It stood 197 feet, 8.25 inches tall, and four sets of guy wires extended up to 184 feet from its base. In the permit application filed with Contra Costa County, its operator noted that its height was “lower than the 200-foot threshold set by the FAA, and thus meets FAA regulations.”

True enough, as far as it went—but the permit was only valid through August 2009, after which the operator was required to remove it within 30 days. The permit also offered the option of applying for a one-year extension, which the operator did not do. So although this “nearly invisible” tower should have been dismantled a year and a quarter earlier, it was still standing, and the county didn’t follow up.

This is at least the third time in eight years that a pilot has been killed in a collision with an unmarked meteorological tower, which the NAAA notes also pose hazards to “emergency medical services (EMS) operations, Fish and Wildlife, animal damage control, aerial fire suppression, and any other low-level flying operation.” Just five days before the accident the FAA had issued a request for comments on its proposed guidelines for voluntarily marking these structures, which included painting the towers themselves in alternating bands of orange and white and marking the guy wires with flags, balls, or high-visibility sleeves. Many of the 460 comments they received specifically referred to this accident. After reviewing submissions from individual operators and groups including NAAA, the Helicopter Association International, the Experimental Aicraft Association, the National Association of State Aviation Officials, and both the American and California Wind Energy Associations, the FAA issued a revised version of its recommendations on June 24—but these recommendations remain voluntary.

Individual states have been more assertive. Wyoming and South Dakota, for example, both require METs to be marked. Wyoming also maintains an online database of their locations, something the FAA insists is not feasible on a national level. While talk of additional regulation goes against most pilots’ grain, the increasing interest in developing wind power can be expected to lead to the assessment of “wind resources” in more locations, most of them rural. Pilots living in those areas might want to know what their states do to make sure those who have to fly down low have a fair chance of coming home again. Private landowners may also choose to require markings as a condition for siting towers on their property.

Aerial application is essential work, and tricky enough at the best of times. Handling heavy aircraft at low altitudes, minimizing the time and fuel lost during turns, it’s a little much to expect even the most expert pilots to watch out for uncharted obstructions that can’t be seen.