For airport taxiway geometric design, which of the following limiting values are used: maximum longitudinal grade, permissible rate of change of grade, and permissible transverse grade?

Introduction / Context:
Taxiway grades influence aircraft ground handling, drainage, and safety. Excessive longitudinal or transverse slopes can cause clearance issues (e.g., nacelle or tail strikes) and impair braking or steering, especially in wet conditions. Therefore, conservative limits are prescribed for gradient magnitudes and for how quickly grades may change.

Given Data / Assumptions:

• Design element: taxiways (not runways).
• Limits under consideration: longitudinal grade, rate of change, and transverse grade.

Concept / Approach:
Typical exam values for taxiways include a maximum longitudinal grade near 3%, a small permissible rate of change of grade (around 1% over a defined control length), and a modest transverse grade near 1.5% to ensure drainage without compromising stability. Grouping them as “all of the above” reflects the integrated nature of these constraints.

Step-by-Step Solution:
Confirm each stated limit as aligned with standard recommendations for taxiways.Recognize the set addresses different but complementary safety aspects.Choose “All of the above.”

Verification / Alternative check:
Airport design manuals consistently set taxiway slopes lower than roadways to match aircraft performance on the ground.

Why Other Options Are Wrong:

• Any single choice alone is incomplete; all three limits are simultaneously applicable.

Common Pitfalls:
Applying runway slope limits to taxiways or ignoring rate-of-change requirements that affect vertical curves on taxi routes.

Final Answer:
All of the above