A checklist for ensuring reliable lightning protection
Most airport towers are built with Lightning Protection Systems. However, serious incidents do occur.
According to a recent Associated Press story, a lightning strike on the airport tower at Baltimore/Washington International Thurgood Marshall (BWI) Airport injured an air traffic controller and revealed a potential vulnerability that could affect towers at other U.S. airports. In the BWI incident the Lightning Protection System failed, most likely because the cable was cut during a construction project several years earlier.
The air traffic controller is recovering, but the incident was serious enough to prompt the Federal Aviation Administration (FAA) to make plans to assess the Lightning Protection Systems at the 440 U.S. air traffic control towers it managers. Special attention will be focused on the 200+ towers built before 1978, when the FAA first established its lightning protection requirements for the following:
Lightning protection components at a glance
If an airport is located in an area with a high incidence of lightning, the Catenary System (used to protect the Space Shuttle) can be used but would be very costly. Sandia National Laboratories (SNL) recommends a less costly (but equally effective) alternative. SNL recommends installing a ground ring complemented with ground rods and radials.
Ensuring reliable lightning protection
The presence of sparks in the incident at BWI indicate a lack of equipotentiality. This problem can be identified with a ground resistance tester like the Fluke 1625-2 GEO Earth Ground Tester and other Fluke test tools.
These are the three steps to take to ensure reliable lightning protection:
Step 1. Assess existing grounding system, measure soil resistivity
Step 2. Measure ground impedance and continuity, and take other preventive maintenance steps
Step 3. Troubleshoot problems
Go here for more detail about each of these steps plus additional information about lightning protection system codes and standards as well as general grounding requirements from FAA AC 150/5340-30D (.pdf) »
Find out more about earth ground testers »
Go to Fluke News article "Don't Forget the Grounding System" »