What is the approach slope requirement for precision instrument runways?

The approach slope requirement for precision instrument runways is set at 50:1, meaning that for every 50 units of horizontal distance, the vertical rise or descent should be 1 unit. This ratio is essential for ensuring that aircraft can safely approach and land on the runway under various weather conditions, particularly those where visibility may be limited.

A 50:1 slope provides a balance between safety and practicality for precision approaches, allowing for the necessary clearance over obstacles while minimizing the potential for excessive descent rates or profiles that are too steep for aircraft performance during landing. This standard is part of the guidelines established by aviation authorities to enhance safety and operational effectiveness at airports, particularly those that handle a high volume of air traffic and where precision approaches are required.

In contrast, slopes like 40:1 or steeper ratios do not meet the specific criteria outlined for precision instrument approaches, which could lead to increased risk during landing due to inadequate obstacle clearance or excessive descent angles.