FAA addresses obstacles in descent paths

New guidance preserves instrument approaches

November 26, 2013

The FAA released a plan Nov. 15 to identify and mitigate the risk of potential obstructions jutting into airspace reserved for the descent path of instrument approaches.

A parcel of airspace on a 20:1 slope leading to the threshold of a runway must be free of obstructions for a given instrument approach. In an internal memo, the FAA outlined a plan to notify airports of potential obstructions, evaluate the risk, and take action if necessary, in some cases removing, lighting, or lowering the obstacle in question.

Many of the instrument approaches affected by the interim guidance, which takes effect Jan. 6, are now marked unavailable at night via notam; AOPA has been working with the FAA to develop alternative solutions so pilots can safely use approaches at night.

When it learns of a potential penetration of an instrument approach procedure (IAP), the FAA will ask airport owners and sponsors to validate the obstruction as soon as possible. Potential obstacles that are found to be invalid will be removed from the FAA’s obstacle database; those found to be valid must be dealt with in a time frame according to whether they are classified as low, medium, or high risk. AOPA supports a risk-assessment approach such as this in favor of a one-size-fits-all approach because it only applies restrictions where there is a significant threat to safety, allowing other approaches to remain open.

“If the penetration(s) are verified as more than 11.0 feet above the 20:1 surface they are considered as high risk and immediate action is required to restrict the IAP visibility to at least 1 statute mile (SM) and if the obstacle is unlighted, restrict night operations,” the memo reads. The airport operator or sponsor must submit a plan to remove, light, or lower the obstacle as soon as possible, or the FAA will restrict the IAP.

The FAA used to permit the use of a visual approach slope indicator (VASI) or precision approach path indicator (PAPI) to mitigate an obstruction in the 20:1 surface area, but in some cases the lighting had given pilots a false sense of security: The glide path provided by the VASI or PAPI could result in collision with the obstacle. The new guidance provides an option other than marking an approach unusable at night.

The FAA has also convened a working group comprising industry representatives, including AOPA, to review its interim guidance, make recommendations for improving it, and develop a long-term solution that takes into account the handling of obstructions, such as buildings, that cannot be moved. The group will evaluate if airports need new instrument approaches to mitigate the risk of immovable obstacles, and whether the 20:1 surface area should be amended for more precise, GPS-based approaches.