3.
BREAKING STRENGTH IS GIVEN IN POUNDS (KILOGRAMS)
4.
DIAMETERS ARE GIVEN IN INCHES (MILLIMETERS)
3-20-2
TETHER LINES
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3-20-3 Anchors for Tethers
1. Many different types of ground fasteners (anchors) are available. The type you use must agree with the strength of the soil at your location. Each fastener is used for a specified type of soil. Ground fasteners (anchors) are made of aluminum or steel (or malleable iron). They are made in different increments, weights and capacities. They are installed with different procedures:
A. Hand installed. Use a manual impact tool, a rod to drive the fastener and a handle to hold the fastener.
B. Screw type. Use a power drive machine.
C. Expandable type. Drill the hole, push the fastener into the hole, turn the fastener until it expands and fill the hole with soil (tamped) or concrete.
2.
When you use ground fasteners (anchors), make a decision about the fastener positions. Install the ground fasteners (anchors) after you refer to the manufacturer’s instructions. Attach each tether line to a screw anchor or an equivalent fastener point on the ground (heavy truck, deadman, tractor). Make sure each position is sufficient for the applicable loads. Use a sufficient factor (margin) of safety. Each line must have an adjustment device (block and tackle, turnbuckle, hoist) to permit small changes in the line tension. Keep a constant, but not too much, tension on the line. Figure 3-10 shows different examples of tether line installation with anchors.
3.
Frequently, it is not easy to find the maximum permitted load you can use for a ground fastener. Thus, we recommend a special tool (Penetrometer or Soil Test Probe) to help you find the permitted load. See the Vendors shown in SUBJECT 5-20-1.
NOTE: THERE IS A SPECIAL TOOL (THE CHANCE PROBE, MODEL C3090032, MADE BY THE CHANCE COMPANY, USA) THAT YOU CAN USE TO FIND THE GROUND STRENGTH WITHOUT THE REMOVAL OF GROUND MATERIAL. THE TOOL HAS A SMALL DIAMETER AUGER THAT HAS A LENGTH OF 60 INCHES (152 CM). THERE IS A TORQUE FIXTURE, ATTACHED TO A RATCHET HANDLE, THAT MOVES ALONG THE AUGER. THIS TORQUE FIXTURE MONITORS THE GROUND STRENGTH IN INCH-POUNDS. WHEN YOU TURN THE AUGER INTO THE GROUND, YOU CAN FIND AN APPROXIMATE STRENGTH VALUE FOR THE GROUND MATERIAL.
3-20-3
ANCHORS FOR TETHERS
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757
AIRPLANE RECOVERY DOCUMENT
Figure 3-3 TETHERING DIAGRAM
3-20-3
ANCHORS FOR TETHERS
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757
AIRPLANE RECOVERY DOCUMENT
Figure 3-4 ENGINE TETHERING
3-20-3
ANCHORS FOR TETHERS
Page 3-17 Jul 01/2005 D623N004
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