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Concerns Over Navigable Airspace

I ATTENDED AN INTERESTING MEETING last week. Despite having a determination of ‘no hazard’ from the Federal Aviation Administration (FAA), despite meeting and exceeding all of the state an local requirements for tall structures, and despite already receiving zoning approval and a building permit, the local airport manager protested the proposed construction of our client’s tower. What’s worse, construction was due to start any day and delaying the project would cost our client thousands of dollars.

The concern that towers impact navigable airspace is often one of the most difficult hurdles to overcome, especially when the site is relatively close to an airport. Even if the FAA has given its approval, local airport managers and private airstrip owners will often argue that the tower is an obstacle and will harm the present and future plans for the airport. Luckily we knew how to combat this problem.

If you haven’t sifted through the National Transportation Safety Board (NTSB) Accident Database, you should. A cursory review of this database will show that there have been very, very few aircraft vs. tower accidents since the NTSB began keeping records in 1962. There were only 65 (or so) aviation accidents involving towers despite more than 250,000 tower sites, 4,000 to 6,000 aircraft flying in the skies at any one time, and more than 50,000 aircraft operations in our country every day. You do the math. That seems like a mighty fine safety record to me.

In the 65 (or so) aircraft vs. tower accidents, the most prevalent cause cited by the NTSB Accident Database was pilot error. The second most common cause was mechanical failure to the aircraft prior to it striking the tower. In other words, something happened to the airplane in the sky and when it fell it had to hit something. In these few instances it hit a tower.

There’s more. If and when an aircraft was involved in mishap with a tower, the tower was usually a tall, guyed tower often greater than 300’ to 400’ tall. If you are attempting to zone a shorter cellular tower (especially if it is a monopole or self-supporting structure), this is an excellent point to make. Would the zoning officials prefer you locate your tower further away from the proposed site, requiring the tower to be taller and guyed so it poses a far greater threat to navigable airspace? I don’t think so.

The use of the NTSB Accident Database as a defense during a zoning meeting is only one of the many weapons one should be armed with before walking into the meeting. You should also:

1. Explain all of the steps your company took to ensure the proposed tower would not affect navigable airspace.

2. Explain the function of the FAA and the meaning of a positive determination (i.e. the structure is not greater than 1’ tall for every 50’ horizontal from the nearest point of the nearest runway, the structure does not displace a runway threshold, etc.).

3. Explain that the FAA solicits comments from local airport managers, aviation clubs and state agencies…and they still approved the proposed structure.

4. Explain how the site meets or exceeds all state and local requirements.

5. Demonstrate how other structures in the vicinity exceed the FAA’s ratio for 1’ tall for every 50’ horizontal from the nearest point of the nearest runway. Be sure to also research the airport at AirNav.com. The listing for the airport will detail structures that are considered obstructions. Also drive around the airport and look for other obstructions, including trees, water towers, buildings, silos, power lines, etc.

6. Be prepared to compromise if necessary. Offer to light the tower top with a red, non-blinking obstruction light instead of a full blown strobe or dual lighting system. Also offer to paint the tower per the FAA’s Advisory Circular # AC70/7460-1K.

Combating overzealous concerns that your tower will impede navigable airspace can be one of the most difficult zoning hurdles to overcome. Knowing the facts and doing your homework, however, can result in success. ■

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