A
CORE DRILL ASPHALT PAVEMENT. FOR PIER LENGTH AND DIAMETER, SEE TABLE B11-1
SPIRAL REINFORCEMENT EQUIVALENT TO THE 13mm [#4]
TIES MAY BE USED.
SEE FIGURE B11-3 FOR ALLOWABLE MOORING AND STATIC 1.
2.
3.
NOTES
16mm [NO. 4] COPPER CONDUCTOR
A A
2
[12"]
13mm [#4]
ELEVATION
N.T.S.
N.T.S.
Table B11-1. Army Pier Length and Depths for Tiedowns
Cohesive Soils
Pier Diameter Pier Length Unconfined Compressive Strength
(qu in kg/m2 [lb/ft2)
m ft m ft
qu < 5,000 kg/m2 (qu < 1,000 lb/ft2)
600 mm 2.0 ft 1,800 mm 6.0 ft
5,000< qu <19,500 kg/m2 (1,000< qu <4,000 lb/ft2)
500 mm 1.5 ft 1,800 mm 6.0 ft
qu >18,500 kg/m2 (qu >4,000 lb/ft2)
500 mm 1.5 ft 1,200 mm 4.0 ft
Cohesionless Soils
Pier Diameter Pier Length
Friction Angle ∅ in Degrees m ft m ft
∅ < 20° 600 mm 2.0 ft 2,100 mm 7.0 ft
20° ≤ ∅ ≤ 30° 600 mm 2.0 ft 1,800 mm 6.0 ft
∅ > 30° 500 mm 1.5 ft 1,800 mm 6.0 ft
B11-3 EXISTING MOORING POINTS FOR ARMY. Existing mooring points will be tested for structural integrity and strength as detailed in Figure B11-2. If the existing mooring fails to meet the structural requirements listed herein, replacement of the mooring structure is required. If the existing mooring point has an attached ground rod, its electrical resistance value must be measured. If it fails to meet resistivity requirements, a new static ground rod is required.
B11-3.1 Evaluation of Existing Mooring Points for Structural Adequacy
B11-3.1.1 Adequate Mooring Points. Existing 19-millimeter (0.75-inch) -diameter bimetallic, copper-covered steel rods, 1,800 millimeters (6 feet) long are considered adequate for immediate aircraft protection, provided the following conditions are met:
The existing rods are installed in rigid pavement.
The existing rods do not show signs of deformation or corrosion.
The existing rods are inspected for deformation and corrosion at least once a year and after each storm event with winds greater than 90 kilometers per hour (50 knots).
B11-3.1.2 Inadequate Mooring Points. At Army facilities, any existing rods that exhibit deformation or corrosion will be considered inadequate and require replacement.
All existing 19-millimeter (0.75-inch) -diameter, 1,800-millimeter (6-foot) -long rods in flexible (asphalt) pavement, including those with a Portland cement concrete (PCC) block at the surface, require replacement.
B11-3.2 Evaluation of Existing Mooring Points for Resistance. The maximum resistance measured, in accordance with IEEE Standard 142, of existing grounding points, will not exceed 10,000 ohms under normally dry conditions. If this resistance cannot be obtained, an alternative grounding system will be designed.
B11-4 STATIC GROUNDING POINTS FOR ARMY FIXED- AND ROTARY-WING FACILITIES
B11-4.1 Type. A static grounding point for Army facilities is a 3-meter (10-foot) rod with a closed eye (see Air Force Static Ground, Figure B11-12) except when installed in a hangar. Inside hangars, the static ground point consists of a copperweld rod attached to a bronze casting with a threaded connection, as shown in Figure B11-9.
Figure B11-9. Army Grounding Point Inside Aircraft Hangars
70mm [2-3/4"] DIA.
73mm [2-7/8"]
19mm [3/4"]
2,400mm [8']
FINISHED APRON
4mm [NO. 10] BRASS BALL CHAIN
19mm [3/4"] N.C. THREAD
19mm [3/4"] COPPER-WELD GROUND ROD
CAST BRONZE COVER FRICTION FIT
CAST BRONZE HOUSING
BRASS PIN 2
B11-4.2 Layout
B11-4.2.1 Fixed-Wing Layout. Static grounding points for fixed-wing aircraft will be located on the parking apron as recommended by the aircraft manufacturer or as required by the facility. Typically, one static grounding point is provided for every two parking spaces, and is located between the parking spaces.
B11-4.2.2 Rotary-Wing Layout. One static grounding point will be provided at each rotary-wing aircraft parking space, as shown in Figure B11-10.
B11-4.3 Installation. Static grounding points can be installed in new concrete or asphalt. New grounding points placed in turf areas will be constructed in a 12,000-square- millimeter (18-square-inch) concrete pad flush with existing ground. Static grounding points for turf areas are shown in Figure B11-11.
B11-4.4 Grounding Requirements. In accordance with IEEE Standard 81, the maximum resistance measured of new grounding points will not exceed 10,000 ohms under normal dry conditions. If this resistance cannot be obtained, an alternative grounding system will be designed.
Figure B11-10. Mooring and Ground Point Layout for Rotary-Wing Parking Space
6m [20']
6m [20'] 6m [20']
STATIC GROUNDING POINT
MOORING POINT-SIX LOCATIONS TYPICAL
0.6m [2']
TIEDOWN CABLE
Figure B11-11. Army Grounding Point for Turf Areas
450mm [18"]
CONCRETE PAD
ARMY STATIC GROUNDING POINT
EXISTING GROUND
PAD CONSTRUCTED FLUSH WITH EXISTING GROUND
150mm [6"] CONCRETE MARKER PAD OVER EXISTING SOIL
GROUND ROD WITH SCREW 3,000mm [10'] COPPER TYPE BOTTOM ANCHOR
B11-5 AIR FORCE TIEDOWNS AND STATIC GROUNDS
B11-5.1 General. For the Air Force, tiedowns will be constructed in accordance with Figures B11-14 and B11-15 and may be used as a static ground provided they meet the requirements given in paragraph B11-5.4. For maximum flexibility, they may be installed in 4.6-meter (15-foot), 6.1-meter (20-foot), or 9.1-meter (30-foot) grids, or offset grids. At minimum, place tiedowns as indicated in aircraft Technical Orders or Facility Requirements Documents. Ideally, tiedowns will be centered in slabs, but, at minimum, shall not be located less than 914 millimeters (3 feet) from any joint.
B11-5.1.1 If tiedowns are intended to also be used as static grounds, soil conditions may require that a ground rod be installed. When a ground rod is included, bond it to the tiedown bar.
B11-5.1.2 Static grounding points will be installed using a minimum 3-meter (10-foot) rod with a closed eye. The 3-meter (10-foot) rod will have a diameter of not less than 19 millimeters (0.75 inch) and the top will be a closed forged eye or a shepherd's hook bend with clamped sleeve, having an inside diameter of not less than 40 millimeters (1.5 inches) (see Figure B11-12). The rod may be copper, copper-clad steel, galvanized steel, or copper-zinc- silicone alloy. The Air Force static ground is used only as a static ground, not an electrical ground, and is not designed to withstand the uplift forces imposed for mooring aircraft. On aprons, stencil the pavement near each static ground with the legend "Static Ground Only" in 102-millimeter (4- inch) block letters. Black lettering on a yellow background that extends a minimum of 51 mm (2 in) beyond the outermost edges of the letters is recommended.
B11-5.1.3 Inside hangars, Air Force activities may use the Army static ground fixture shown in Figure B11-9. All static ground fixtures inside hangars must be connected to the building ground and all grounds must be bonded.
B11-5.2 Layout. Static grounds and tiedowns will be configured and spaced in accordance with the requirements of the mission aircraft and will vary from aircraft to aircraft. An example of a multiple fixed-wing aircraft tiedown layout is shown in Figure B11-13.
Figure B11-12. Air Force Static Ground
19mm
19mm
25mm 40mm 115mm [4 1/2"] APPROX.
DETAIL OF EYE AND SLEEVE ASSEMBLY
127mm [5"] DIA. MIN.
PAVEMENT
150mm [6"] MAX.
75mm
A A
B
B
APPROX. 80mm [3-1/4"] R.
ANCHOR
ANCHOR EDGES ROUNDED