.
THE LOAD ON EACH GEAR CAN CHANGE WHILE YOU TOW THE AIRPLANE. THUS, THE RECOVERY PERSONS MUST CONTINUOUSLY MONITOR THE PRESSURE GAGES ON THE GEAR STRUTS.
2-10-2
EFFECT OF TERRAIN AND WEATHER
Page 2-10 Jul 01/2005 D623N004
2-10-3 Soil Analysis
1.
The load capacity of the soil is very important. You must know it when you tow the airplane or when you use tethers or supports with the airplane.
2.
We use a standard named the California Bearing Ratio (CBR) to compare the different soil conditions. This standard compares the soil strength to the strength of some (crushed) stone (shown as 100). Figure 2-6 shows the strength (CBR) for different soil conditions.
3.
Examine the load capacity of the soil.
A. The surface hardness and smoothness
B. The effect of rain
C. The safe bearing load and area (see Figure 2-7)
D. The maximum rut depth (see Figure 2-4 and Figure 2-5).
NOTE: If you have large depths (rut depths), you must use supports (ground cover, shoring or cribbing). These supports increase the load capacity of the soil (see Figure 2-6).
4.
If jack points on the airplane are lower than the soil, you must remove the necessary soil. If you must use supports, you must put the supports on a hard surface of the correct dimensions. The soil capacity gives you the dimensions of the support surface. The dimensions of the support surface (cribbing base) give you the depth of soil you must remove (see Figure 2-6).
5.
You must have soil of the same strength for a depth of eight inches (20 cm).
6.
If it is possible, find a person who knows about ground capacities (Civil Engineer or Soil Analyst). This person can help you make the decisions about the load capacity of the ground at the incident location. We recommend this.
7.
Make a check of the possible weather conditions that can occur. The terrain in the area can change with the weather.
A. Water (heavy rains) can change the capacity of the ground. In some locations, you must use irrigation pumps or drainage ditches to remove unwanted water.
B. Cold weather (snow and ice) can make very hard conditions.
C. High winds can blow airborne material (sand and dust) and make the operation slow.
2-10-3
SOIL ANALYSIS
Page 2-11 Jul 01/2005 D623N004
[1] THE RUT DEPTH IS LIMITED BY A 24,560 LB (11140 KG) MAXIMUM TOW OUT FORCE ON THE MAIN LANDING GEAR STRUCTURE (SEEFigure 4-17)
2-10-3
SOIL ANALYSIS
Page 2-12 Jul 01/2005 D623N004
