Att.3 - FAA Slip Ring Specification Document (4-8-19).4-8-19

Terminal Doppler Weather Radar (TDWR) Dustless Slip Ring Assembly Requirements Description

1.0 Mission

1.1 Intent

The intent of this document is to define what the minimum requirements are for a dustless, replacement slip ring assembly for the TDWR. While a “dustless” slip ring assembly design is desired, the FAA will consider alternate bids addressing “reduced dust” slip ring assembly designs, as well. Section 4.4 addresses specification requirements if a “reduced dust” design is provided.

Though not required, responding vendors are encouraged to provide a proposal for each type of design described above, however, emphasis is on the “Dustless Design”. During the proposal review process, the FAA will decide which path, “Dustless” or “Reduced Dust”, is in the best interest of TDWR improvement and service life extension projects; only proposals within the selected bid/design type will be considered for contract award.

The goal of this procurement is to obtain a high reliability slip ring assembly for the TDWR in a realistic timeframe that is compatible with the FAA’s schedule constraints. Responding Vendors are also encouraged to propose ideas for reducing project risk, production time, and/or production cost.

1.2 Expectations

The pedestal slip ring assembly will be expected to meet or exceed the specifications as outlined below. The pedestal slip ring assembly will support a 3-phase brushless motor with resolver feedback, dual-motor drive system and will be expected to minimize maintenance (dustless) and to increase the reliability of the TDWR antenna pedestal. The slip ring assembly shall be designed to meet or exceed the requirements as outlined in FAA-G-2100H, Federal Aviation Administration Specification, Electronic Equipment, General Requirements, dated May 9, 2005.

2.0 Slip Ring Environment

The Slip ring assembly is mounted inside of an antenna pedestal that is rain tight, and the entire pedestal is protected by a radome but otherwise is not environmentally protected.

2.1 Installation Orientation

The slip ring assembly is oriented vertically (the assembly’s axis of rotation is perpendicular with the ground) when installed in the antenna pedestal.

2.2 Operating life

The slip ring assembly will be operated continuously and will have a life period of 20 years. It is expected that there will be a minimum of 53 x 106 revolutions of the slip ring assembly over the period of 20 years.

2.3 Duty Cycle

The TDWR antenna operates 24 hours a day, 7 days a week, except when shut down for corrective or preventive maintenance.

2.4 Temperature Range

-50° C to +55º C (operating) -40º C to +70º C (non-operating)

2.5 Altitude

0 to 10,000 feet above MSL (operating)

0 to 50,000 feet above MSL (non-operating)

2.6 Humidity

5% to 100% (operating) 0% to 100% (non-operating) Above 40º C, the relative humidity is based on a dew point of 40º C. The above includes condensation due to temperature changes.

2.7 Salt Fog

The slip ring shall be resistant to the corrosive effects of a salt fog atmosphere.

2.8 Fungus

No fungus nutrients shall be used in the construction of this unit. Only inherently fungus-resistant materials shall be used. Reference Guideline 4 of MIL-HDBK-454B for guidance.

2.9 Oil

The slip ring shall be resistant to oil seepage. Oil shall not be allowed to enter the assembly from the top or the sides.

3.0 Reliability Requirements

3.1 Safety

The unit shall conform to Government/DOD safety requirements. Reference Guideline 1 of MIL-HDBK-454B for guidance.

3.2 Dissimilar Metals

If dissimilar metals must be in contact, precautions must be taken to alleviate electrolytic corrosion. Design shall be in accordance with MIL-STD-889B. Reference Guideline 16 of MIL-HDBK-454B for guidance.

3.3 Workmanship

Workmanship shall conform to best acceptable practices. Reference Guideline 9 of MIL-HDBK-454B for guidance.

3.4 Quality Assurance Provisions

Shall be in accordance with the purchase order. The vendor shall test each slip ring assembly prior to shipment. Testing shall be in accordance with the vendor generated and FAA approved Acceptance Test Procedures (ATP). A copy of the test results shall be shipped with each assembly.

The FAA may perform tests on any production shipment to substantiate that the design criteria have been satisfied.

3.5 All of the specifications herein, including the electrical noise requirement of Section 5.6, shall be met over the unit's 20-year service life.

4.0 Mechanical Requirements

FAA Drawing AE-D-2337-1 defines the FAA’s desired Form/Fit dimensions for the slip ring assembly. It defines information pertaining to assembly length, maximum diameter, bore hole, Next Higher Assembly interface requirements, connector locations (with exceptions noted below), etc. Non-dimensioned components shown in the FAA Drawing AE-D-2337-1 are not intended to suggest design preferences. The drawing should be used in conjunction with pertinent information from this document. Deviation from the FAA’s desired slip ring assembly dimensions is only allowed for specific circumstances/exceptions described in this specification document and the statement of work.

4.1 Overall Physical Dimensions

Construction and physical dimensions shall be in accordance with this specification and FAA Drawing AE-D-2337-1.

4.1.1 Bore Hole: 3.97 – 4.00 in.

4.1.2 Stator Outside Diameter: 8.25 in. (not including connectors)

4.1.3 Overall Length: 21.5 in. +0/-.2 (not including connectors or stator restraining pin)

4.1.4 Variation in desired Stator Outside Diameter and Cylinder Length

The “Form” and “Fit” requirements of the slip ring assembly’s design allow for a slight increase in overall length and/or stator outside diameter, assuming certain conditions are met. The vendor may depart from the desired overall length and/or stator outside diameter dimensions, shown in FAA Drawing AE-D-2337-1, only if, in doing so:

1. Initial procurement costs are reduced, Lifecycle (i.e. removal, maintenance, repair, and reinstallation) cost are reduced, Maintenance requirements decrease, and/or Mean Time Between Failure (MTBF) increases;

2. The Contractor includes all components and hardware necessary to replace TDWR infrastructure affected by the deviation from the FAA’s desired length and/or outside diameter of the slip ring assembly (e.g. Infrastructure components most likely affected by an increase in the slip ring assembly’s length are the slip ring assembly support arm, waveguide sections above, and sections below the TDWR azimuth rotary joint);

3. The design does not require special or exotic parts, tools, maintenance actions, or special skills to install;

4. The design does not interfere with normal maintenance activities of other TDWR parts and equipment (e.g. removing and replacing the motor units)

Regardless of dimensional changes (Length/Diameter), the Contractor must deliver a complete turnkey solution that is immediately compatible with a brushless motor equipped TDWR system. The Contractor’s proposal must include the cost of replacing pedestal infrastructure components impacted by their design. Interface with the FAA Contracting Officer’s Representative (COR) to obtain specifications and drawings for use in defining modifications to or replacements of infrastructure components/equipment affected by increased dimensions (length/diameter) of the slip ring assembly design.

4.2 Housing

The housing shall be a cylindrical (i.e. Drum) shape with an internal hollow shaft/bore hole. The internal hollow shaft shall have a diameter large enough to allow the flange of a WR-187 waveguide to pass through it. Refer to FAA Drawing AE-D-2337-1 for clarification of bore hole dimensional requirements and constraints.

4.3 Dielectric

Material shall be in conformance with this specification document.

4.4 Contacts

The slip ring assembly contacts coupling the rotor to the stator are to be “Dustless”, meaning the interaction between rings and contacts produces negligible amounts of dust over a significant period of time. Dust removal shall not be a necessary or required maintenance action, for the FAA or the Vendor/Repair Source.

Note: If an alternate bid, pertaining to a “Reduced Dust” design, is submitted, all specifications contained in this document remain valid except for the contact requirements, above. The contacts in a “Reduced Dust” design produce dust, however, at a significantly reduced rate compared to traditional silver graphite brush contacts. An assembly using this type of brush/contact may require removal of dust as a maintenance action at vendor recommended maintenance intervals, but not before.

4.5 Internal Wire

All conductors are to be stranded Copper. Wire shall be insulated and meet environmental requirements herein. Wire temperature rating shall be 105º C minimum.

4.6 Stator Rotation Restraint

The stator section of the existing TDWR slip ring assembly is restrained from rotational motion via a metal pin located at the bottom of the stator section. The pin rests in a slot on a support arm mounted to the wall of the pedestal.

Ideally, the proposed TDWR slip ring assembly will re-utilize the pedestal’s existing infrastructure in order to restrain stator rotation. Figure 4.6, below, illustrates the existing arrangement in the azimuth pedestal. FAA Drawing AE-D-2337-1 identifies the required location and size of the rotation restraint pin for ease of implementation; alternate means of preventing stator rotation are acceptable.

4.7 Connectors

Connectors shall be per MIL-C-38999, type MS27466. Refer to FAA Drawing AE-D-2337-1 for connector pin-out information.

4.7.1 Rotor Connector Positioning/Orientation

Rotor connectors are to be located on the top of the assembly, oriented axially (i.e. parallel to the rotational axis of the slip ring assembly), and separated by 120º. FAA Drawing AE-D-2337-1 illustrates the orientation of the rotor connectors relative to each other and the Next Higher Assembly interface connection bolt holes also located on the top of the slip ring assembly.

4.7.2 Stator Connector Positioning/Orientation

Stator connectors are to be radially oriented on the stator (i.e. perpendicular to the rotational axis of the slip ring assembly). Figure 4.6 illustrates the relationship between the Stator Restraining Pin (or other restraining method), the Stator Connectors, and the Azimuth Hatch. The stator connectors must be oriented such that they face the pedestal’s azimuth hatch when the slip ring assembly is properly installed; this is illustrated by the grey shaded section/zone in Figure 4.6.

Note that FAA Drawing AE-D-2337-1 depicts radially oriented stator connectors located near the bottom of the assembly, however, this specific location and/or configuration is not a requirement. As stated above, the only constraints for placement of stator connectors is that A.) they are radially oriented and B.) face in the direction of the azimuth hatch when the slip ring assembly is installed.

4.8 Rotational Characteristics

Velocity: 30 degrees per second (5 RPM).

Acceleration: 15 degrees/sec/sec Rotation: Clockwise & Counter-Clockwise directions

4.9 Rotational Torque

10 ft-lbs. maximum

5.0 Electrical

A total of 73 rings are required for this application; their characteristics are described in the following sections.

5.1 Ring Order

Ring order is at the discretion of the manufacturer with only the following criteria:

Distribute the rings such that they are placed in a manner minimizing the occurrence of high potential between any two adjacent rings that could lead to arcing. Examples of high power/high potential rings are the motor power rings (phase a,b,c rings), A/C outlet rings, etc.; basically, high potential rings are not signal rings.

5.2 Insulation Resistance

Circuits 1 through 21: 500 MEGOHMS minimum @ 1500 VDC when tested between mutually insulated points or between insulated points and ground.

Circuits 22 through 73: 200 MEGOHMS minimum @ 500 VDC when tested between mutually insulated points or between insulated points and ground.

5.3 Dielectric Strength

Circuits 1 through 21: 1500 VRMS @ 60 Hz for 5 seconds when tested between mutually insulated points or between insulated points and ground.

Circuits 22 through 73: 500 VRMS @ 60 Hz for 5 seconds when tested between mutually insulated points or between insulated points and ground.

5.4 Description of Circuits 1 through 21:

5.4.1 Motor Power Circuit (Quantity of 2)

4-wire twisted shielded insulated 12 AWG circuit, 50 Amps RMS, 320VDC.

Each wire plus the shield is assigned to a ring for a total of 5 rings in this circuit (See note 2). A total of 10 rings are utilized for both motor power circuits combined.

5.4.2 120VAC SERVICE

Two, 2-wire twisted shielded insulated 16 AWG circuits, 40 Amps RMS, 200 VAC each. A single phase is divided amongst the 4 wires (i.e. 2 hot and 2 neutral wires); the hot wires share a ring, and, similarly, the neutral wires share a ring. Each shield (one from each TSP) is given its own ring (see note 2). A total of 4 rings are utilized for this circuit.

5.4.3 120VAC LIGHTS

2-wire twisted shielded insulated 16 AWG circuit, 5 Amps RMS, 200VAC. Single phase with neutral and shield (see note 2). A total of 3 rings are used.

5.4.4 SPARE RING (Quantity of 2)

2-wire insulated 16 AWG circuit, 35 Amps RMS, 200VAC; 1 ring per circuit. One line divided amongst 2 wires combined into one ring. A total of two (2) rings are utilized for both spare circuits combined.

5.4.5 SERVICE GND

2-wire insulated 16 AWG circuit, 40 Amps RMS 200VAC; 1 ring per circuit. One line divided amongst 2 wires combined into one ring. Total number of rings used is 1.

5.4.6 SPARE RING

1-wire insulated 16 AWG circuit, 35 Amps RMS, 200VAC; 1 ring per circuit. Total number of rings used is 1.

Note 1: For thermal design considerations, any 10 of these power circuits (circuits 1 through 21) will be at their full rated power (current) at any given instant; the others will be at half current or less.)

Note 2: Shield is to be continuous through the assembly. Shield ring is to be rated for no less than ½ Amp and 24 AWG.

5.5 Description of Circuits 22 through 73

5.5.1 EL 1x CX

Twisted shielded insulated triple, 22 AWG circuit, 2 Amps, 200VAC. Each wire plus the shield is assigned to a ring for a total of four (4) rings (See note 2, above).

5.5.2 EL 28&1/8 CX

Twisted shielded insulated triple, 22 AWG circuit, 2 Amps, 200VAC. Each wire plus the shield is assigned to a ring for a total of four (4) rings (See note 2, above).

5.5.3 SYNCRHO REF

Twisted shielded insulated pair, 20 AWG circuit, 2 Amps, 200 VAC. Each wire plus the shield is assigned to a ring for a total of three (3) rings in this circuit (See note 2, above).

5.5.4 EL RES REF/1

Same as Section 5.5.3

5.5.5 EL RES REF/2

Same as Section 5.5.3

5.5.6 EL#1 SIN

Same as Section 5.5.3

5.5.7 EL#2 SIN

Same as Section 5.5.3

5.5.8 EL#1 COS

Same as Section 5.5.3

5.5.9 EL#2 COS

Same as Section 5.5.3

5.5.10 SOUND PHONE

Same as Section 5.5.3

5.5.11 DOWN LIMIT

1-wire insulated 20 AWG circuit, 2 Amps RMS, 200VAC; 1 ring per circuit.

5.5.12 UP LIMIT

Same as Section 5.5.11

5.5.13 +26 VDC

Same as Section 5.5.11

5.5.14 AZ STOW PIN INTLK

Same as Section 5.5.11

5.5.15 EL HANDCRANK INTLK

Same as Section 5.5.11

5.5.16 INTLK BUS

Same as Section 5.5.11

5.5.17 +26VDC

Same as Section 5.5.11

5.5.18 EL/1 BOX OIL LVL

Same as Section 5.5.11

5.5.19 EL/2 BOX OIL LVL

Same as Section 5.5.11

5.5.20 +26VDC

Same as Section 5.5.11

5.5.21 26V RTN

Same as Section 5.5.11

5.5.22 EL STOW PIN INTLK

Same as Section 5.5.11

5.5.23 26V RTN

Same as Section 5.5.11

5.5.24 EL MOTOR/1 FDBK SHIELD

Same as Section 5.5.11

5.5.25 EL MOTOR/2 FDBK SHIELD

Same as Section 5.5.11

5.5.26 EL MOTOR/1 THERMO

Same as Section 5.5.11

5.5.27 EL MOTOR/2 THERMO

Same as Section 5.5.11

5.5.28 SPARE

Same as Section 5.5.11

5.5.29 SPARE

Same as Section 5.5.11

5.5.30 SPARE

Same as Section 5.5.11

5.6 Electrical Noise

Dynamic contact resistance change of any of the 73 circuits shall not exceed 30 milliohms at 50 milliamps and 5 RPM.

5.7 Circuit Resistance/Continuity

Stationary Channel Resistance shall not exceed 200 milliohms.

6.0 Maintenance

6.1 Periodic Maintenance

The antenna pedestal slip ring assembly will be maintained in accordance with manufacturers’ recommendations. It is expected that the periodic maintenance will consist of listening for worn or deteriorating bearings and visual inspection of rings and contacts for cleanliness (if required) at intervals not to be less than annually. Based upon the bearing life and ring contact life determined by the manufacturer, slip rings will be periodically replaced at scheduled intervals not less than once every 7 years to prevent unscheduled outages of the TDWR system.

6.2 Ring Cleaning Statement

Should there be a requirement for periodic cleaning of the rings (in accordance with the requirements of Section 4.4, above), there should be no chance for exposure to hazardous materials. There should be no requirement for maintenance technicians to don respirators. The prescribed maintenance should be able to be completed within 45 minutes. There will be no other periodic maintenance.

Figure 4.6: TDWR Azimuth Pedestal Arrangement. Depicted is a profile view of the azimuth housing, left, and a top view of the housing, right.