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Question concerning control tower equation

The criteria for the establishment and/or discontinuance is found in APO 90-70 (google the document). It outlines the benefit cost analysis used, which involves some rather involved weighting methodology. Reading the document does provide insight into the emphasis placed on air carrier operations, in part because of the perceived risk exposure to larger number of people involved and the mix differential of the aircraft (read mix to mean speed, airspace need, wake turbulence, etc). The end result is a John Lawson mentioned, a calculated BCA greater than 1.0 versus a BCA less than 1 (14CFR Part 170). The formula that you may be thinking about where the type of operations plays a part in the formula (GA vs. air carrier vs. military) may actually be the formula used for the old ADAP and current ACIP calculation for funding criteria. 

The answer to the board's question is a risk-based response.... the focus is on the number of people. More people have exposure should an aircraft accident occur with an air carrier than with a GA operation. The exception is if there is a congress-person on board a GA aircraft involved in an accident (tongue firmly in place ). An additional factor is the assumption of larger aircraft with greater speed differential than GA piston aircraft (totally ignoring that GA includes larger jet operations as well). And then the number of instrument operations come into play, since air carriers are required to operate under those requirements.

One of the impacts not being fully discussed about the closure of towers and the reduction of navaid maintenance is the potential impact on the future closure of navigational aids. There is a BCA associated with navaid facilities as well. With towers inoperative, that may result in a reduction of instrument approaches (due to a lack of weather reporting capabilities or individual company/insurance policies that restrict/limit operation at nontowered facilities or to higher minimums in effect). The reduction in numbers may then impact decisions about discontinuance of a navaid (ILS, for instance) and promote the (FAA) goals of ADB-S implementation or consolidation at the TRACONS or CENTERS. 

Tough situation all around. Being involved in SMS, I can see the assessment of risk playing out in the current debate. The real question the board should be asking is "what level of risk are we willing to tolerate?" The FAA is now saying they are willing to accept a higher level of risk than in the past. Affected airports are saying otherwise, in which case, the burden may fall on the airport to support the lower risk assessment through self-funding, lawsuits, congressional emphasis, etc.  Hope this helps.

Stephen M. Quilty, A.A.E.    SMQ Airport Services 26757 Haverhill Drive Lutz, FL  33559-8509

813-388-9132    SMQAirportServices@xxxxxxxxx

The mission of SMQ Airport Services is to support the airport management profession with training and education,

safety audits, SMS and group facilitation, organizational development and assessment, and special research study.

On Wed, Apr 3, 2013 at 9:20 AM, <Richard.Stein@xxxxxxxxxxxxxxx> wrote:
Everyone -

I have a question about equation that the FAA uses (or use to use) for determining if a control tower would be considered for an airport.

Background - Lynchburg Regional Airport is losing its contract control tower next month.  We're currently examining several options, including asking the state to use our entitlement funding to continue to operate the control tower for a few months until a permanent solution is found.  One of the questions from the Aviation Board was "Why are Air Carrier operations more important in determining if we get to keep our control tower"?

One piece of the answer is an equation I remember from college that used airline operations, general aviation operations and some other operations to get a result.  If the result was over a certain number - you were more likely to get a tower.

That class was over 25 years ago - I'm glad I remember the equation at all.

My question:  What was the equation for determining having a control tower?

Any comments would be appreciated, also feel free to email or call with any questions or comments about the tower closure issue.

Richard M. Stein, A.A.E.
Deputy Airport Director, Operations and Maintenance
Lynchburg Regional Airport
350 Terminal Drive, Suite 100
Lynchburg, VA  24502
(434) 455-6088
(434) 239-9027 (fax)


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