Airport obstacle surfaces

Journal of Advanced Transportation, Fall, 2009 by Scott Litsheim, Xiaosong Xiao

TSS is utilized to locate runway threshold in order to meet approach and departure obstacle clearance requirements, and to determine if a threshold displacement is necessary due to penetrations to the approach or departure surface. The dimensions of TSS vary with the type of aircraft operations, the approach visibility minimums, and the types of navigational instrumentation, which are defined in AC 150/5300-13, Appendix 2 [FAA(2006b)].

The majority of the TSSs in Table A2-1 of FAA AC 150/5300-13 are surfaces from other sources. Only the first three surfaces originate from this Advisory Circular. Most importantly, these first three surfaces are the only ones that cannot be penetrated without requiring a relocation or displacement of a threshold. Rather, the remaining TSSs in Table A2-1 are TERPS surfaces and the OEI surface, which can be penetrated without requiring a relocated or displaced threshold, although with other tradeoffs, such as restricting TERPS night operations or limiting air carrier takeoff weights.

6. FAA's Obstruction Evaluation Process

The prime objective of the FAA in conducting obstruction evaluation (OE) studies is to ensure the safety of air navigation and to efficiently utilize navigable airspace by aircraft. There are many demands being placed on the use of the navigable airspace. The FAA's philosophy in evaluating objects is that a structure that exceeds one or more of the FAR Part 77 obstruction standards is presumed to be a hazard to air navigation unless the obstruction evaluation study determines otherwise.

Aeronautical studies are conducted to determine the impact of an object on the safe and efficient use of airspace. In order for an object to be considered to have an adverse effect, one or more of the following conditions must be met [FAA(2006c)]:

* Exceeds the obstruction standards of Part 77 and/or have a physical and/or electromagnetic effect on the operation of air navigational facilities.

* Requires a change to an instrument procedure or minimum flight altitude.

* Requires a change of VFR regular flight course or altitude.

* Restricts control tower line-of-sight.

* Reduces airport capacity and efficiency.

* Affects future VFR and/or IFR operations.

* Affects useable runway length.

For a determination of hazard (DOH) to be issued, a substantial adverse effect must exist. An object has a substantial adverse effect if it causes electromagnetic interference to the operation of an air navigation facility or the signal used by aircraft, or if there is a combination of:

* Adverse effect.

* Significant volume of aeronautical operations.

What volume of aeronautical operations is "significant"? When one of the following occurs the volume is considered significant:

* One or more VFR or IFR arrival or departure per day.

* An average of once-a-week for an instrument approach procedure or minimum altitude that serves as the primary procedure under certain conditions.

If a substantial adverse effect is found to exist, a DOH is issued. In the absence of such a finding, a determination of no hazard (DNH) will be issued.