Atch_29_UFC_3-260-01-Tie_Down.pdf

UFC 3-260-01

17 NOVEMBER 2008

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

5m m m m m m

[4

/2

A P

P R

O X

DETAIL OF EYE AND

SLEEVE ASSEMBLY 127mm [5"] DIA. MIN.

PAVEMENT

150mm [6"] MAX.

5m m

A A

B

B

APPROX. 80mm [3-1/4"] R.

ANCHOR

ANCHOR

EDGES ROUNDED

SECTION A

SECTION

B

DETAIL OF PAVEMENT RECESS

FOR CONCRETE

[3/4"] R

[3/4"] R

[1

[1

/2

[3

38 mm [1.5"]

THREADED OR

WELDED SCREW

ANCHOR FOR

FLEXIBLE PAVEMENT

SHEPHERDS HOOK

OR FORGED EYE

19mm [3/4"] MIN DIAMETER x 3,000mm [10'] COPPER, COPPER

CLAD STEEL, GALVANIZED

STEEL, OR

COPPER-ZINC-SILICONE ALLOY

COPPER COMPRESSION

SLEEVE FOR SHEPHERDS

HOOK STYLE ROD ENDS

NOTES

1. STATIC TIEDOWN GROUNDS ARE NOT INTENDED

AS AIRCRAFT TIEDOWNS OR THRUST ANCHORS.

2. THESE WILL BE USED AS EXTERIOR STATIC

GROUND POINTS FOR ARMY ROTARY WING

AIRCRAFT.

Figure B11-13. Example of Air Force Multiple Tiedown Layout for Fixed-Wing Aircraft

6m [20']

18m [60']

6m [20']

17m [56']

9m

3m [10']

B-1B BLAST DEFLECTOR

B-1B TIEDOWN

LOCATION

THIS IS AN EXAMPLE FOR ONE AIRCRAFT (B-1B).

FOR SPECIFIC AIRCRAFT DIMENSIONS REFERENCE

THE AIRCRAFT TECHNICAL ORDER (T.O.)

(AVAILABLE FROM MAINTENANCE ASSISTANCE

PROGRAM OFFICE).

[30']

C OF PARKING SPOTL C OF PARKING SPOTL

NOTE:

B11-5.3 Installation

B11-5.3.1 Static Grounds in Rigid Pavement. Where static grounds are to be installed in rigid pavement, the rods may be installed without bottom anchors. Static grounds should be offset a minimum of 600 millimeters (2 feet) from any pavement edge, joint, or tiedown point.

B11-5.3.2 Static Grounds in Flexible Pavements. Where flexible pavement is to be constructed, static grounding rods will be equipped with a screw-type bottom end having a wing diameter of not less than 127 millimeters (5 inches), as shown in Figure B11-12. The helical anchor may be welded to the rod or the rod may be threaded to permit attachment to the bottom anchor.

B11-5.3.3 Pavement Recess Design. The top of the static ground will be set at pavement grade or not more than 6 millimeters (0.25 inch) below grade. A smooth, rounded-edge recess 75 millimeters (3 inches) wide and not more than 150 millimeters (6 inches) long will be provided in the pavement around the eye for accessibility and attachment of grounding cables. This is shown in Figure B11-12.

Figure B11-14. Air Force Aircraft Tiedown, Profile

127mm [5"]

NOTES:

1. PLACE TIE DOWNS AS INDICATED IN AIRCRAFT TECHNICAL ORDER OR FACILITY REQUIREMENTS

DOCUMENT. IF THE TIEDOWN IS INTENDED TO ALSO BE USED AS A STATIC GROUND, SOIL

CONDITIONS MAY REQUIRE THAT A GROUND ROD BE INSTALLED. WHEN A GROUND ROD IS

INCLUDED, BOND IT TO THE TIEDOWN BAR.

2. MINIMUM DISTANCE FROM TIEDOWN CENTER POINT TO AN UNDOWELED JOINT IS 914 mm (3').

WHEN TIE DOWNS OCCUR 914mm [3 '] FROM A SINGLE JOINT, ORIENT BAR PARALLEL WITH THE JOINT. IF CENTER POINT OCCURS 914mm (3') FROM ADJACENT JOINTS, ORIENT BAR PARALLEL

WITH EITHER JOINT.

3. BAR WILL BE 32mm [1.25"] AISI 4130.

4. MINIMUM SLAB THICKNESS IS 254mm [10"].

5. PIER DIMENSIONS FOR ASPHALT PAVEMENTS MUST BE DESIGNED TO ACCOMMODATE

ANTICIPATED UPLIFT FORCES. FOR 17,100 kg (37,700 LBS) MINIMUM PIER DIMENSIONS ARE 1.83m x 1.83m x 2.13m (6' x 6' x 7').

6. FOR INSTALLATION IN PREEXISTING SLABS, INSTALL 1" Ø x 16" DOWEL RODS CENTERED AT HALF

SLAB DEPTH , ALL FOUR SIDES AS SHOWN IN THE PLAN VIEW. MINIMUM ANCHOR BLOCK

DIMENSIONS IN THIS CASE ARE 254mm [10"] x 1,067mm [42"] x 1,067mm [42"].

76mm [3"] R

146mm [5.75"]

914.4mm [36"]

254mm [10"] MINIMUM

92.25mm [3.75"]

178mm [7"] 127mm [5"] 152mm [6"]

#5 REBAR, FOUR

EACH WAY, TYP

114mm [4.5"]

DOWELS REQUIRED FOR

INSTALLATION IN PREEXISTING SLABS,

SEE NOTE 6

406mm [16"]

DOWEL

PRE-EXISTING

SLABS

Figure B11-15. Air Force Aircraft Tiedown, Plan

25mm [1"]

DOWELS

1,067mm [42"]

1,067mm [42"] 76mm [3"] MIN

305mm [12"] MIN

152mm 6"]

203 mm [8"]

203 mm [8"]

1m (3') MIN TO JOINT

1m (3') MIN TO JOINT

B11-5.4 Grounding Requirements. The maximum resistance of new static grounds, measured in accordance with IEEE Standard 81, should not exceed 10,000 ohms under normal dry conditions. If this resistance cannot be achieved, an alternative grounding system should be considered. Tiedowns that meet the above requirements may be used as static grounds.

B11-6 TIEDOWN MOORING EYES FOR NAVY AND MARINE CORPS.

Requirements, layout, and installation details for Navy and Marine Corps tiedown mooring eyes are found in Figure B11-16. Requirements, layout, and installation details for Navy and Marine Corps grounding arrangements are found in MIL-HDBK-274.