Attachment 3 - UFC 3-260-01 Appendix B Ch 11 Army Criteria.pdf

UFC 3-260-01

4 February 2019

Change 1, 5 May 2020

APPENDIX B

SECTION 11

TIEDOWNS, MOORING, AND GROUNDING POINTS

B11-1 TYPES OF EQUIPMENT.

B11-1.1 Mooring and Grounding Point.

A mooring and grounding point is a mooring casting with a grounding rod attached.

Aircraft mooring and grounding points are used to secure parked aircraft and also serve as electrodes for grounding connectors for aircraft. Combined mooring and grounding points have previously been used by the Army but are not currently used as they do not meet mooring and grounding design loads required by TM 1-1500-250-23.

B11-1.2 Mooring Point.

A mooring point is a mooring casting without a grounding rod attached, used to secure parked aircraft. Mooring points are used by the Army.

B11-1.3 Static Grounding Point.

A static grounding point is a ground rod attached to a casting. The casting protects the ground rod but does not provide mooring capability. Static grounding points are used by the Army in aprons and hangars.

B11-1.4 Static Ground.

A static ground is a 3-meter (10-foot) rod with a closed-eye bend. The static ground is not intended to secure parked aircraft but may serve as an electrode connection for static grounding of aircraft. Static ground are installed at many Air Force installations.

B11-1.5 Tiedown Mooring Eye.

A tiedown mooring eye is a mooring casting with a grounding rod attached. They are similar to the mooring and grounding point discussed above. Tiedown mooring eyes are used by the Navy and Marine Corps.

B11-2 MOORING POINTS FOR ARMY FIXED- AND ROTARY-WING

AIRCRAFT.

B11-2.1 Type.

A mooring point consists of a ductile iron casting, as shown in Figure B11-1. The mooring casting is an oval-shaped casting with a cross-rod to which mooring hooks are attached.

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Figure B11-1. Army Mooring Point

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B11-2.2 Design Load.

Unless specifically waived in writing by the facility commander, all new construction of Army aircraft parking aprons will include aircraft mooring points designed for a 67,800- Newton (15,250-pound) load, as specified in TM 1-1500-250-23 and applied at 19.15 degrees (19.15°) from the pavement surface, as illustrated in Figure B11-2. Testing of new mooring point installations is not required; however, follow Figure B11-2 if testing is performed.

Figure B11-2. Army Load Testing of Mooring Points

B11-2.3 Layout.

B11-2.3.1 Fixed-Wing Aprons.

Mooring points should be located as recommended by the aircraft manufacturer or as required by the base.

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B11-2.3.2 Rotary-Wing Aprons.

B11-2.3.2.1 Number of Moored Parking Spaces.

All exterior aircraft parking spaces will be provided with mooring points.

B11-2.3.2.2 Number of Mooring Points at Each Parking Space.

Each rotary-wing aircraft parking space location will have six mooring points. Although some rotary-wing aircraft only require four mooring points, six will be installed to provide greater flexibility for the types of rotary-wing aircraft that can be moored at each parking space. The largest diameter rotor blade of the facilities’ assigned aircraft will be used for locating the mooring points within the parking space. The allowable spacing and layout of the six mooring points is illustrated in Figure B11-3. Parking space width and length dimensions are presented in Table 6-2 of Chapter 6.

B11-2.3.2.3 Mooring Points on a Grid Pattern.

A 6-meter by 6-meter [20-foot by 20-foot] mooring point grid pattern throughout the apron for mass aircraft parking aprons will not be authorized unless economically and operationally justified in writing by the installation commander. Figure B11-4 provides the recommended pavement joint and mooring point spacing should grid pattern mooring be utilized.

B11-2.4 Installation.

B11-2.4.1 Mooring Points for New Rigid Pavement Equal to or Greater Than 150 Millimeters (6 Inches) Thick.

Mooring points for new rigid pavements will be provided by embedding the mooring devices in fresh Portland cement concrete (PCC). The layout of points is shown in Figure B11-3 with mooring points at least 600 millimeters (2 feet) from the new pavement joints. This spacing will require close coordination between the parking plan and the jointing plan. Mooring points should be located a minimum of 600 millimeters (2 feet) from any pavement edge or joint and should provide proper cover for the reinforcing steel. Reinforcing bars should be placed around the mooring points as illustrated in Figure B11-5.

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Figure B11-3. Army Rotary-Wing Allowable Mooring Point Spacing

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Figure B11-4. Army Rotary-Wing Mooring Points Layout

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Figure B11-5. Slab Reinforcement for Army Mooring Point

B11-2.4.2 Mooring Points for Existing Rigid Pavement Equal to or Greater Than 150 Millimeters (6 Inches) Thick and in Uncracked Condition.

The following method should be used to provide mooring points for existing rigid pavement in an uncracked condition. The pavement should have only a few slabs with random cracks and must not exhibit "D" cracking. Mooring points should be provided by core-drilling a 300-millimeter (12-inch) -diameter hole through the pavement and installing a mooring point as illustrated in Figure B11-6.

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Figure B11-6. Mooring Point for Existing Rigid Pavement for Pavement Thickness Greater Than 150 Millimeters (6 Inches)

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B11-2.4.3 Mooring Points for Areas Not Covered Above.

The following installation options should be used to provide mooring points for rotary-wing aircraft parked on the following pavements: existing rigid pavement less than 150 millimeters (6 inches) thick; existing rigid pavement in a cracked or deteriorated condition; new or existing flexible pavement; turfed areas; and other areas where appropriate.

B11-2.4.3.1 Installation Option 1, Mooring Pad.

This option is the preferred installation method and allows for placement of a new concrete pad with a minimum thickness of 200 millimeters (8 inches). The size of the pad should be a minimum of 7.3 meters (24 feet) wide by 13.4 meters (44 feet) long.

The length and width may be increased to match the existing concrete joint pattern. The mooring pad, with six mooring points, is illustrated in Figure B11-7. The mooring devices should be installed as illustrated in Figure B11-1 and the concrete reinforced as illustrated in Figure B11-5.

B11-2.4.3.2 Installation Option 2, Piers.

This option allows the use of individual concrete piers for each mooring point, as shown in Figure B11-8. The diameter and length of the pier must be based on the strength of the soil, as presented in Table B11-1.

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Figure B11-7. Army Rotary-Wing Mooring Pad Detail

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Figure B11-8. Army Mooring Point for Grassed Areas, Flexible Pavement, or Rigid Pavement - Thickness Less Than 150 millimeters (6 inches)

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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).

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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 AND AIR FORCE FIXED-

AND ROTARY-WING FACILITIES.

See UFC 3-575-01 for static ground requirements. One static ground point shall be provided at each rotary-wing parking position, as shown in Figure B11-9.

Figure B11-9. Mooring and Ground Point Layout for Rotary-Wing Parking Space