Answers for Pilots

10 questions

February 1, 2001

Fight a towering threat

AOPA provides information for its members through a vast array of communications technology. You can reach experts in all fields of aviation via AOPA Online (, the AOPA Pilot Information Center (800/USA-AOPA), and via e-mail. Aviation technical specialists respond promptly to member requests. Recently a member wrote with this concern:

"Recently [an] article appeared in the local newspaper [with the headline "Cell Towers May Threaten Airport"]. I have an airplane based at the Carlisle Airport (N94), and I can tell you that it is the last paved runway in Cumberland County, Pennsylvania. It is a high-volume reliever airport for the Harrisburg area. It would be terrible for the local pilot community to lose our airport. I am an AOPA member and would like AOPA's help to keep our airport open. Can you please help us?"

The growing number of cellular telephone and other antenna towers often threatens GA airports. In order for AOPA to participate in the obstruction evaluation process, AOPA Aviation Technical Specialist Keith Holt asked the member to provide AOPA with more information, specifically to respond to the following questions:

  • What is the location of the proposed obstruction? This should include the approximate location relative to the airport as well as common airways or other factors that could cause the obstruction to be a hazard to aircraft.
  • How tall will the object be (height in feet msl and agl)?
  • How will the object affect aeronautical operations, specifically VFR operations? (What are the main concerns of pilots regarding the obstruction: will it raise minimums or pattern altitude?)
  • Do you know if the FAA is conducting or has conducted an aeronautical study? (This information can be obtained from the airport management or possibly the FAA's Regional Airports Office.)
  • If there is an aeronautical study, what is the aeronautical study number?
  • Is there a comment period open for the public now? If so, when does that end?
  • If the comment period has closed, or if there was not one, has the FAA already issued a Determination of No Hazard finding?
  • Are there any local zoning laws that can be used to stop the construction?
  • What local authorities have jurisdiction over the site of the obstruction?
  • Have local authorities already issued all necessary approvals for the sponsor to build?

These 10 questions were prepared by AOPA's Air Traffic Services department to better equip AOPA to argue a case for an objection to a proposed obstruction. Answers to these questions determine how AOPA can get involved, according to Michael Brown, AOPA associate director of air traffic services.

The Federal Aviation Regulations (FARs) require that persons wishing to construct a tall structure must notify the FAA if the structure exceeds the notice outlined in section 77.13(a), but the agency has no enforcement jurisdiction. The FAA's only authority is to study the request and make a determination as to whether it presents a negative impact to the safe and efficient use of the airspace. Consequently, tall structures may be constructed even if the obstruction presents a hazard to air navigation (though rarely does construction proceed once such a determination has been made, said Brown). A "no hazard" designation only means that the structure does not exceed the FAA standards.

Currently, AOPA Air Traffic Services is preparing an issue brief on the obstruction evaluation process. The guide will help members participate in the process, according to Brown, and will be available to members after March 1 on AOPA's Web site. "Also, the obstruction evaluation process cannot help private-use airports, but AOPA may be able to help with alternatives," added Brown. (There is no federal precedent governing privately owned airports.)

As an AOPA member, you have access to the best resource anywhere for information and answers for pilots. AOPA Online ( provides members with access to information and resources 24 hours a day, seven days a week. The AOPA toll-free Pilot Information Center gives you direct access to specialists in every area of aviation. The center, 800/USA-AOPA (800/872-2672), is available to members from 8:30 a.m. to 6 p.m. Eastern time, Monday through Friday.

AOPA Web resources

AOPA Pilot article, "The Towering Imbroglio: Who Let Them Build That Tower There?" Describes AOPA's ongoing campaign to strengthen the FAA's ability to regulate structures that affect aviation.

You may download the FAA forms applicable to obstruction evaluation (Form 7460-1: Notice of Proposed Construction or Alteration; Form 7460-7: Acknowledgement of Notice of Proposed Construction or Alteration; Form 7460-8: Aeronautical Study of Proposed Construction or Alteration; Form 7480-1: Notice of Landing Area Proposal; Form 7460-10: Determination of Hazard to Air Navigation; and Form 7460-9: Determination of No Hazard to Air Navigation) by visiting the FAA's Web site (

Julie Walker

Julie Summers Walker | AOPA Senior Features Editor

AOPA Senior Features Editor Julie Summers Walker joined AOPA in 1998. She is a student pilot still working toward her solo.