Desert Landing Site (DLS) – Final

1. Soft/Wet Spots: These areas are prioritized first as they are most likely to have weakened load-bearing capacity. Testing here ensures safety by assessing the risk of excessive deformation or instability under aircraft weight, which could lead to hazardous conditions.

2. Repaired Areas: Repaired areas are next because they might have variable compaction and strength due to recent work. Testing verifies whether these areas meet the required standards and can withstand operational stresses without premature failure.

3. Primary Braking Zone: This zone experiences high stress during landing as aircraft decelerate. Testing ensures the soil can handle repeated braking forces, reducing the risk of rutting or soil displacement that could compromise safety.

4. Turnaround Areas: These areas handle heavy loads as aircraft turn, which can create significant lateral stress on the soil. Testing helps confirm that the area can support these maneuvers without excessive wear or instability.

5. Touchdown Zone: The touchdown area is subject to impact forces each time an aircraft lands. Testing ensures that the soil can withstand the repeated compressive loads, preventing issues like surface deformation or reduced structural integrity.

6. Point of Rotation: This area bears the weight of the aircraft during liftoff, where the nose lifts, and additional stress is applied. Testing here ensures that the soil strength is sufficient to support these loads, helping maintain a safe and stable surface for takeoffs.

This priority order addresses the highest risk areas first, ensuring that critical zones affecting operational safety are tested before moving to lower-stress areas.

The Surface Profile Airfield Condition Index (SPACI) surface distress of Rolling Resistant Material (RRM) is directly related to the Rolling Friction Factor (RFF), as both measure how surface conditions affect the ease or resistance of aircraft movement over the airfield.

Here’s how they are connected:

1. Surface Roughness and Rolling Resistance:
• The SPACI rating for RRM reflects the roughness, texture, and overall quality of the airfield surface. High SPACI surface distress, indicating rough or uneven surfaces, results in increased rolling resistance as the wheels encounter more friction and resistance when moving over irregularities.
• Rougher surfaces, such as those with loose aggregate or damaged areas, contribute to a higher Rolling Friction Factor (RFF). A higher RFF means there’s more resistance to rolling, which can lead to increased wear on aircraft tires and affect fuel efficiency.
2. Impact on Aircraft Performance:
• As SPACI surface distress increases (indicating more severe surface issues), the RFF also rises, meaning aircraft require more power to overcome the additional rolling resistance. This is especially relevant during taxiing, takeoff, and landing, where high RFF values can impact braking, acceleration, and fuel consumption.
3. Maintenance Implications:
• A high SPACI surface distress rating for RRM typically signals the need for maintenance or repair to reduce RFF. By improving surface smoothness, the airfield can lower the RFF, enabling smoother, more efficient operations.

The primary purpose of the Dynamic Cone Penetrometer (DCP) in airfield surveying is to evaluate the strength and load-bearing capacity of soil layers. This is critical for determining whether the ground can support the weight and operational demands of aircraft and other heavy equipment. In airfield surveying, the DCP provides essential data for:

1. Assessing Soil Strength: The DCP measures soil resistance at various depths, indicating how well different soil layers can support loads. This information helps engineers understand the structural integrity of the airfield’s subsurface layers.
2. Identifying Layer Boundaries: By measuring the penetration resistance at each depth, the DCP helps define the depth and thickness of soil layers with varying strengths, which is essential for determining suitable pavement or soil reinforcement designs.
3. Predicting Performance under Load: DCP results are used to estimate the California Bearing Ratio (CBR) of the soil, a key indicator of its load-bearing capability. Higher CBR values correlate with stronger soils that can support heavier loads.
4. Supporting Maintenance and Rehabilitation Decisions: By identifying weak layers or areas with low load-bearing capacity, the DCP aids in planning maintenance, upgrades, or reinforcement efforts for airfield pavements and unpaved areas.