Attachment_7_Environmental_Test_Plan_for_Rotary_Switch_SWU58A-002.pdf

Attachment VII: ETP For Rotary Switch. For Reference Purposes Only i

Environmental Test Plan

For

Rotary Switch, SWU-58/A

AGM-86, Air Launched Cruise Missile

Aging & Surveillance Program

December 3, 2009

Prepared By

For

498th MSUG

7339 Sentry Blvd

Tinker AFB, OK 73145 i

TABLE OF CONTENTS

Section Page

I. ITEM DEFINITION

1.1 Physical

1.2 Theory of Operation

II. AGE SENSITIVITY ITEM ANALYSIS SUMMARY

III. TEST METHODS

3.1 Test Methods for Each ASIA Parameter

3.1.1 Contamination and Corrosion

3.1.2 Degradation, Embrittlement, Cracking and Fatigue

3.1.3 Fatigue of Voids and Delaminations

3.1.4 Metal Migration

3.1.5 Contact Wear and Contamination

3.1.6 Electrical Contact Copper Diffusion Through Gold Plating

3.1.7 Degradation of Insulation

3.1.8 Corrosion in Electrical Connectors

3.2 A&S Test Methods and Environments

3.2.1 Functional Tests

3.2.2 Performance Tests

3.2.2.1 Actuator Switch Contact Timing

3.2.2.2 Actuator Switch Closed Contact Resistance

3.2.2.3 Detent Pin Extraction

3.2.2.4 Detent Pin Insertion

3.2.2.5 Relay Contact Wear

3.2.2.6 Relay Contact Closure Timing

3.2.3 A&S Unique Tests

3.2.3.1 Capacitor Leakage Current

3.2.3.2 Ceramic Capacitor Failure Due to Manufacturing Defects

3.2.3.3 Inductor Insulation Degradation

3.2.3.4 Wire Chaffing

3.2.3.5 Solder Manufacturing Defects

3.2.3.6 Insulator Pad Degradation

3.2.4 Visual Inspections

3.2.4.1 Corrosion/Contamination of Housing, exposed surfaces of nylon guide for detent pin insertion, and ball bearings

3.2.4.2 Corrosion/Degradation of Electrical Connector Pins

3.2.4.3 Housing Cover O-Ring Seal

3.2.4.4 Circuit Board Conformal Coating Degradation

3.2.5 Environmental Tests

3.2.5.1 Leak Tests

3.2.5.2 Vibration/Temperature Tests

IV. TEST EQUIPMENT AND FACILITES REQUIREMENTS

ii

V. AGING & SURVEILLANCE STORAGE ENVIRONMENTS

VI. A&S TEST REQUIREMENTS

6.1 Test Classifications

6.2 Test Types

6.2.1 Baseline “A” Tests

6.2.2 Interval “B” Tests

6.2.3 Comprehensive “C” Tests

6.3 Test Sequence

6.4 Test Data Categorization

VII. MEASUREMENTS LIST

LIST OF TABLES

Tables Page

Table 1. Recommended Parameters for Rotary Switch Monitoring Table 2. Random Vibration Levels Table 3. Temperature Test Levels Table 4. Combined Environmental Test Levels Table 5. Equipment and Facilities Required for Testing the Rotary Switch Table 6. Recommended A&S Tests Table 7. Sample Size Table 8. Measurements List

LIST OF FIGURES

Figures Page

Figure 1. Rotary Switch Physical Interface Figure 2. Rotary Switch Electrical Interface Figure 3. Measurement Circuit for Wet Tantalum Capacitors in Parallel Figure 4. Typical Measurement Circuits for Inductors Configured in the EMI Filter Figure 5. Temperature Variances for MOB 1 and MOB 2 Figure 6. Humidity Variances for MOB 1 and MOB 2 Figure 7 Recommended Rotary Switch Test Flow

I. ITEM DEFINITION

1.1 Physical

The SWU-58/A Rotary Switch Assembly is defined on Envelope Drawing 232-30040, The Boeing Company detailed by Consolidated Controls Corporation (CCC) Drawing 76410. The source for all Rotary Switches was CCC as a sub-vendor to Boeing. (Note:

Eaton Industries acquired CCC in 1986, Eaton Industries was subsequently acquired by VACCO in 2000.)

The rotary switch contains internal components that include: an EMI Filter, 11 sub-miniature relays, a separation switch actuator assembly, a resistor board assembly, and 11 diodes. Two interface connectors, J1 and J2, provide electrical interface between the rotary switch functionality and other missile components. Connector J1 is an integral part of the EMI Filter, while J2 is a surface mount connector that physically attaches to the rotary switch housing via screws. Each rotary switch has mounting holes drilled in its housing so that it can be physically attached to the air vehicle via screws and washers.

Figures 1 and 2 show the rotary switch physical and electrical interfaces.

Fuel Service Valve

Exhause Nozzle Cover

Oxygen Assist Cartridge

Air Supply Valve

Start Cartridge

Wing Deploy Acatuator

Elevon Deploy Actuator

Fin Deploy Actuator

Battery

Rotary

Switch

Inertial

Navigation

Element

Umbilical

Enclosure

WAD

Launch

Critical

Functions

Figure 1. Rotary Switch Physical Interface

ROTARY SWITCH (FR08S)

RTN

EBW CHARGING

RTN

EBW CHARGING

RTN

EBW TRIGGER

RTN

EBW TRIGGER

RTN

ENABLE BATT ACT

ENABLE BATT ACT RTN

MAIN LOAD BUS

RETURN

BATTERY ACTIVATE

BATT ACT RTN

WAD LOAD BUS (-)

WAD LOAD BUS (+)

ORD ALARM MON

ORD ALARM MON RTN

Rotary Switch

J1 J2

Lanyard

(Installed)

K2

E

F

D BATTERY CARTRIDGE #2

BATT CART RTN

BATTERY CARTRIDGE #1

C

I

X

FIN DEPLOY

ELEVON DEPLOY

START CARTRIDGE

WING DEPLOY

PARACHUTE DEPLOY

AIR SERVICE VALVE

OXYGEN ASSIST

EXHAUST NOZZLE

SEP ARM EXCT RTN (K11)

FUEL SERVICE VALVE

SQUIB

CONTROL

RELAYS

(K3 - K11)

V

W

J

P

R

N

B

C

A

J

G

C

H

T

U

S

H

R

S

N

X

M

K

M

F

L

P

Q

T

To K6

To K8

To K7

To K4

To K10

To K3

To K11

To K9

To K5

PULSE

LOAD BUS

RELAY

COMMON

K3 - K10

SEP ARM EXCITATION

SEPARATION ARM EXCT RTN

PULSE LOAD BUS (-)

PULSE LOAD BUS (+)

SQUIB ENABLE

R

P

B

J

M FILTER

Z

A

B

D

E

Y

TEST

INTER-LOCK

To P10

FIN DEPLOY ACT CART #1

FIN DEPLOY ACT RTN

FIN DEPLOY ACT CART #2

ELEVON DEPLOY ACT CART #1

ELEVON DEPLOY ACT RTN

ELEVON DEPLOY ACT CART #2

START CART #1

START CART #1 RTN

START CART #2 RTN

WING DEPLOY ACT CART #1

WING DEPLOY ACT RTN

WING DEPLOY ACT CART #2

TO RECOVERY UNIT (P4)

OXYGEN ASSIST CART #1

OXYGEN ASSIST CART #1 RTN

OXYGEN ASSIST CART #2 RTN

EXHAUST NOZZLE COVER CART #1

EXHAUST NOZZLE COVER RTN

EXHAUST NOZZLE COVER CART #2

FUEL SUPPLY VALVE CART #1

FUEL SUPPLY VALVE CART RTN

FUEL SUPPLY VALVE CART #2

AIR SUPL VALVE CART #1

AIR SUPL VALVE RTN

AIR SUPL VALVE CART #2

OXYGEN ASSIST CART #2

START CART #2

K1

G

R

W

T

U

V

B

E

C

D

Q

D

H

P

J

S

A

E

K

L

M

G

H

F

N

Z

F

D

F

E

J1 J2 Figure 2. Rotary Switch Electrical Interface

1.2 Theory of Operation

The Rotary Switch is used in conjunction with the ALCM secondary power during the launch and free flight modes of operation. Its purpose is to function as a power distribution unit. The rotary switch provides isolation, enabling, and distribution of electrical power directly to the ALCM “Launch Critical” functions and indirectly to the warhead arming device and warhead via the umbilical assembly and the inertial navigation element.

During ground handling operations, the rotary switch prevents external application of bus power within the ALCM.

During captive carry (prior to launch), the Enable Battery Activate signal is generated in the aircraft setting the K2 relay, thus closing the Battery Activate signal path. A secondary signal is generated from the aircraft and is routed uninterrupted through the umbilical, the rotary switch, and associated cable harnesses to the pulse load battery cartridge to initiate ALCM secondary system power.

At launch, the detent pin is extracted and the separation switch actuator in the rotary switch operates to close the circuit paths for the pulse load power bus and the main load power bus. Secondary paths in the switch complete the loop between the constant load power and the engine power setting actuator.

After launch, the rotary switch receives commands from the inertial navigation element that configure internal circuitry to provide output power to the launch critical functions highlighted in Figure 1. Throughout the ALCM free flight mode of operation, the rotary switch provides the electrical interface for the main bus power for the Warhead Arming Device.

II. AGE SENSITIVITY ITEM ANALYSIS SUMMARY

The Age Sensitivity Item Analysis (ASIA) on the Air Launched Cruise Missile (ALCM) Rotary Switch has concluded that the component is age sensitive and that its inclusion in the ALCM A&S program is appropriate. The details concerning all ASIA findings and recommendations are documented in the ALCM Rotary Switch ASIA Report, dated 8 October 2008. The Rotary Switch is one of three ALCM hardware components included in the Nuclear Weapon Sub-System (NWSS) that provide the electrical interface with the warhead for arming and fuzing control.

The materials analysis found evidence of major aging concerns associated with the switch actuator and switch deck, electrolytic capacitors, and electrical relays within the rotary switch. Each of these issues is highlighted below.

There are several aging effects and switch actuator conditions that may, alone or in combination, eventually cause the rotary switch deck to fail. The aging effects include diffusion of copper through the gold plating of the contact switches (resulting in oxidation of the copper and an increase in switch contact resistance) and the build up of contamination, corrosion and deterioration within the actuator housing, impacting switching functionality.

Two electrolytic (wet tantalum) capacitors are used on the pulse load bus power circuit to provide low pass signal filtering. The combined attributes of known leakage current degradation and the uncertainty in the quality of the hermetic seal on these capacitors may have adverse long-term effects, which will continue to get worse due to metal migration within the components, and eventually may result in a short circuit across the capacitor.

The relays inside the rotary switch have exhibited some wear and contamination on the relay contact surfaces. Similar characteristics in relays used in the WAD have resulted in the relay contact surfaces causing open circuits and failure conditions. This is an aging effect that is likely to become more frequent over time.

These mechanisms, coupled with other known aging mechanisms in this type hardware, have led to the identification of 19 critical parameters and 2 non-critical parameters for the rotary switch. The 2 non-critical parameters were dismissed as viable A&S candidates as described in the Rotary Switch ASIA Report. All 19 critical parameters were recommended for inclusion in the ETP and TRD development efforts. The delineation between critical and non-critical parameters can be found in the ASIA Report.

Table 1 summarizes the conclusions of the ASIA study and identifies the critical aging mechanisms that should be considered for inclusion in the A&S program for this component.

Identifier Name Aging Mechanism Critical Non-Critical

Actuator Assembly

Contacts Diffusion of copper through gold plating

Piston/Spring Mechanism Contamination and corrosion

Sleeve Bushing Contamination and corrosion

O-Ring Seals Embrittlement and cracking

Switch Deck Discs Degradation & cracking

Resistor Board Assembly

Conformal Coating Degradation

Relays

Relay K1 Contact wear & contamination

Relay K2-K11 Contact wear & contamination

Table 1. Recommended Parameters for Rotary Switch Monitoring

Identifier Name Aging Mechanism Critical Non-Critical

EMI Filter

Feed thru Capacitors Fatigue of voids and delaminations

Inductors Degradation of insulation

Ceramic Capacitors Fatigue of voids and delaminations

Connectors Corrosion

Wet Tantalum Capacitors Metal migration

Circuit Board Fatigue

Miscellaneous Components

Wiring Wire chafing

Solder Vibration, exposure

Connector Assembly Corrosion

Insulator Pads Degradation, burns, holes

O-Ring Seal Embrittlement and cracking

Table 1. Recommended Parameters for Rotary Switch Monitoring (cont)

Aging & Surveillance testing on the rotary switch is required to provide the data necessary for analysis and life predictions relative to the noted age sensitivities.

Methods of testing for each of these aging mechanisms are discussed in Section III.

III. TEST METHODS

This report section describes test methods recommended for the A&S program for the rotary switch. Program constraints limit ALCM A&S testing to non-destructive test types. Therefore only test methods and test environments that are non-destructive in nature are fully documented for use in the development of the Test Requirements Documents. In Section 3.1, test methods are described which are suitable for characterizing the individual ASIA parameters noted in Section II. In Section 3.2, these test methods are combined into more specific A&S test methods that will be used as the basis for the development of the Test Requirements Document (TRD) in those cases where non-destructive tests can be implemented.

3.1 Test Methods for Each ASIA Parameter

The following paragraphs discuss methods of testing for each of the aging mechanisms identified in the ASIA and noted in the table of Section II. Where applicable, alternative methods of testing are discussed and recommendations are made.

3.1.1 Contamination and Corrosion

The ASIA describes build up of contamination and corrosion inside the plunger and actuator housing as well as on the ball bearings and piston that are part of the piston/spring mechanism. The nylon guide insert in the housing, where the pull-out pin is inserted, exposes these components to contamination and moisture. This is further exacerbated by the application of lubricant on the pull-out pin during maintenance as the lubricant can rub off on the components and act as a collecting agent for the contaminates. The sleeve bushings used to provide free rotational motion for the switch lever could also collect particulate debris leading to contamination and corrosion.

Visual inspection will reveal contamination and corrosion in the piston/spring mechanism and sleeve bushings of the rotary switch actuator assembly components. Magnification (approximately 30X) should be used to aid the inspection.

Note: The rotary switch has some established disassembly and assembly procedures in an authorized Technical Order. However disassembly of the switch actuator to visually monitor contamination and corrosion on many of the subcomponents would be considered a destructive test until such time that approved maintenance procedures could established. This will limit the types and extent of the inspections implemented.

3.1.2 Degradation, Embrittlement, Cracking and Fatigue

Visual inspection will reveal degradation of the circuit board conformal coating;

degradation and cracking of the switch deck discs; embrittlement and cracking of o-ring seals; degradation and cracks in circuit board conductive paths.

Note: Disassembly of the switch actuator to visually monitor degradation and cracking of the switch deck would be considered a destructive test on the switch actuator until such time that approved maintenance procedures could established. This will limit the types and extent of the inspections implemented.

3.1.3 Fatigue of Voids and Delaminations

A test to determine fatigue of voids and delaminations in capacitors can be used to determine an open circuit or short to chassis.

Note: Destructive disassembly of the rotary switch EMI Filter is required in order to inspect the feed thru capacitors. This will limit the extent of the inspections to rotary switch failures that require teardown analysis.

3.1.4 Metal Migration

A test to determine metal migration in wet tantalum capacitors can be used to monitor for high leakage rates or electrical shorts.

3.1.5 Contact Wear and Contamination

A test to determine contact wear and contamination within the relays can be used to monitor for a high resistant path or open circuit.

3.1.6 Electrical Contact Copper Diffusion Through Gold Plating

The diffusion of copper through the gold plating on the rotary switch actuator contacts can be characterized by metallurgical examination. A cross-sectioned sample can be examined by means of a SEM X-ray line scan in order to identify the metals near the surface of the sample. The diffusion of copper into the gold plating layer can thus be characterized. In advanced aging cases, copper oxide (black in appearance) may be seen on the gold plating during a visual inspection under a microscope.

Note: Disassembly of the switch actuator for these inspections would be considered a destructive test until such time that approved maintenance procedures could established.

This will limit the types and extent of the inspections implemented.

3.1.7 Degradation of Insulation

A test to determine a change in value or possible shorts in the inductors of the EMI Filter can be used to monitor this aging mechanism.

3.1.8 Corrosion in Electrical Connectors

Electrical tests and visual inspections can be used to check for changes to resistive paths and open circuits.

3.2 A&S Test Methods and Environments

This section provides recommended A&S test methods based on the non-destructive testing requirements identified in Section 3.1 above. Authorized maintenance Technical Orders detail allowable rotary switch disassembly and assembly procedures. Some of the detailed inspection of internal components for aging effects requires that the rotary switch and switch actuator and/or its sub-assemblies be destructively disassembled. Described below are non-destructive tests that can be performed at the switch assembly-level and those tests that can be conducted within the bounds of the authorized maintenance procedures.

Prior to conducting electrical tests, rotary switches should be visually inspected for obvious signs of damage and/or corrosion. A functional test of the rotary switch should also be conducted to verify initial condition.

The following test methods will not damage the rotary switch, allowing it to be placed back into service. These non-destructive tests may provide indications of possible aging effects of internal components, and thus may be beneficial for identifying samples to select candidates for destructive disassembly and more detailed inspection as the A&S Program advances.

Four test methods are defined in this test plan. They include Functional Tests, Performance Tests, A&S Unique Tests, Environmental Tests and Visual Inspections.

Each method is described below.

3.2.1 Functional Tests

The functional test for the rotary switch should include: verification that all relays function the actuator switch functions, verification of resistance measurements of all closed circuit paths, and insulation resistance measurements. The closed loop paths include:

a) Simple loop back paths from one pin to another in the same connector (i.e., Test Interlock pins J2Z-to-J2A, and the 12 redundant outputs for launch critical squib paths such as J2A-to-J2B for elevon deploy and J2S-to-J2T for wing deploy)

b) Loop back paths thru relays K3 thru K11 which short output circuit paths when relays are not activated (i.e., all Rotary Switch outputs paths for squib cartridges for the Launch Critical Functions)

c) Loop back paths thru the EMI Filter and the switch contacts in the actuator and back to J1 (i.e., ordnance alarm loop, emergency destruct paths, and warhead load bus power paths)

d) Battery Activate and Return Paths thru the EMI Filter, thru K2 contacts and to output pins in J2

e) Paths from output signal lines for launch critical functions back trough each of the 100 K-ohm resistors (used for static grounding of those output lines) and back to the rotary switch case.

f) Pulse Load Bus and Return Paths thru the EMI Filter, thru switch contacts in the actuator, thru 1-ohm current limiting resistors and thru the closed K3-K11 relay contacts.

Measured resistances on closed loop paths should be less than 2 ohms for the circuit paths with the current limiting resistors, approximately 100 K-Ohm for the static ground circuit paths, and less than 1 ohm on all other paths. A milliohm meter with a 4-wire test lead (to eliminate effects of the test lead) should be used to make this measurement, since the measured resistance will be very low. Insulation resistance measurements should be greater than or equal to 100 meg-ohm at 100 VDC.

3.2.2 Performance Tests

The performance tests identified for inclusion in the Rotary Switch A&S Program include: Actuator Switch Contact Closure Timing, Actuator Switch Closed Contact Resistance, Detent Pin Extraction, Detent Pin Insertion, Relay Contact Closure Timing, and Relay Contact Wear.

3.2.2.1 Actuator Switch Contact Timing

Upon removal of the detent pin, the actuator switch contacts should close each circuit path within 7.5 milliseconds. A measurement of the closure time can be used to characterize the aging characterize weakening of the spring loading mechanism in the actuator, and corrosion and/or contamination in the piston o-ring seal in the sleeve bushings, plunger and actuator housing.

3.2.2.2 Actuator Switch Closed Contact Resistance

The closed contact resistance measurements can be used to characterize aging effects associated with arcing and pitting of the contacts; diffusion of copper through the gold plating resulting in oxidation at the contact surface; and (to a lesser degree) wear of the gold plating. In addition, gross failure of the electrical connections through the external connector, internal soldered wires, and shorting bars can be detected.

When a switch contact is closed, the measured resistance across the contact should be near zero. A high accuracy ohmmeter with a 4-wire test lead (to eliminate effects of the test lead) should be used to make this measurement, since the measured resistance will be very low.

In addition, the contact resistance should be measured under load by applying a test current and measuring the voltage drop across the actuator switch connector pins. All 11 actuator switch contacts used in the rotary switch can be measured from J1 thru the EMI Filter and switch deck and back to J1.

Engineering documentation that defined the limits for the contact resistance is no longer available through the OEM (reference 78346 PTP1, as defined on Actuator Assembly, Separation Switch mechanical drawing 78346). The switch deck design used for the rotary switch is identical to that used for the ACM Arm/Disarm Device. The available ACM A/DD specification documentation states that the contact resistance shall not exceed:

44 x 10-3 ohms with a current load of 5 Amperes

200 x 10-3 ohms with a current load of 500 Amperes

These limits should be used as a guideline for developing the test requirements for this test method.

3.2.2.3 Detent Pin Extraction

Measurement of detent pin extraction forces can be used to characterize aging due to the combined effects of changes of spring force; corrosion of internal components; and internal contamination.

A test apparatus will be required that will allow measurement of the force required to extract the pin while measuring the force required for its release. The rotary switch specification states that the force required to overcome the detent and remove the pin shall be no less than 30 pounds (static). In addition, the dynamic extraction load shall not exceed 95 pounds with initial velocities of 8 ft/sec and 17 ft/sec and with the force applied at angles up to 25 degrees from the axis of the detent pin receptacle.

3.2.2.4 Detent Pin Insertion

Measurement of detent pin insertion forces can be used to characterize aging due to the combined effects of changes of spring force; corrosion of internal components; and internal contamination.

A test apparatus will be required that will allow measurement of the force required to insert the pin while measuring the force required for its insertion. The rotary switch specification states that the force required to set the pin into the detent position shall not exceed 35 pounds when the force is applied in a direction up to 15 degrees from the axis of the detent pin receptacle. Variation of the pin alignment from parallel thru 15 degrees offset from the detent pin receptacle must be monitored.

3.2.2.5 Relay Contact Wear

The relay closed contact resistance measurement can be used to characterize aging effects associated with arcing, pitting, and general wear of the contacts. In addition, gross failure of the electrical connections through the external connector, internal wiring, and internal soldered connections can be detected by means of measurements at the interface connections of the Rotary Switch.

When a relay contact is closed, the measured resistance should be near zero. A high accuracy ohmmeter with a 4-wire test lead should be used to make this measurement, since the measured resistance will be very low. This test method will also to eliminate effects of test lead circuit loading. Limits will need to be established for the acceptable resistance of the contact and associated connections. Initially, a 1.0 ohm (1000 mΩ) value can be assumed as an acceptable limit, until sufficient A&S data has been collected to establish more precise limits.

It is necessary to power the relay contact before the resistance can be measured. The relay pull-in and drop-out voltages should also be recorded and tracked for the A&S program, which can be performed by monitoring for continuity through any relay contact while the applied coil voltage is ramped up or down. The nominal relay coil voltage is 28 volts direct current.

The engineering data available for the Rotary Switch does not specify actuation currents for the relays. In prior studies of the Advanced Cruise Missile, it was noted that the maximum actuation current for each of the ACM Arm/Disarm Device relays K3, K4, K5, K6, K7, K8, and K9 was specified at 250 milliamperes. Since the relays used in the Rotary Switch are built to the same Military Standard, the maximum limit of 250 milliampres should be used until sufficient A&S data has been collected to establish more precise limits.

3.2.2.6 Relay Contact Closure Timing

The Rotary Switch specification establishes circuit closure timing requirements that are directly associated with the performance of the individual relays. This measurement can be used to characterize the relay coil performance and/or build up of contamination or corrosion within the relay. This measurement can be made by analyzing the time variance between applying the relay actuation voltage and observing a change of continuity across a contact set within the relay.

3.2.3 A&S Unique Tests

Several electrical tests are defined that are not generally considered as functional tests or performance tests. They can, however help determine the long-term health of the rotary switch and are therefore included as A&S Unique Tests. Tests related to these issues include: Wet Tantalum Capacitor Leakage Current, Ceramic Capacitor Failure Due to Manufacturing Defects, Inductor Insulation Degradation, Actuator Assembly Switch Contact Resistance and Disk Degradation, Wire Chaffing, Soldering Manufacturing Defects, Insulator Pad Degradation.

3.2.3.1 Capacitor Leakage Current

There are two wet tantalum electrolytic capacitors used in the Rotary Switch. The 270 F capacitors, encapsulated in the potting inside the EMI Filter housing, are used in filtering the input signal for the Pulse Load Bus Power. The ASIA identified high leakage currents in these capacitors as a susceptible aging mechanism due to inherencies of the wet tantalum design.

Exact measurement of leakage current of individual capacitors requires that the capacitor be removed from the circuit. A voltage is applied across the capacitor (typically either the in-circuit voltage, or the capacitor’s rated DC voltage) while power supply output current is monitored. The measured leakage current is then compared with the manufacturer’s rated maximum value.

This method would require destruction of the EMI Filter metal case and potting in order to individually test each capacitor. Since no destructive tests will be included in the ALCM A&S Program, a modified measurement capability for the leakage current in a non-destruct test will be implemented. The filter design coupled with its application in the rotary switch allows for non-destructive measurement of the combined leakage of the two capacitors in their parallel configuration. The following diagram is a depiction of the required measurement circuit.

Figure 3. Measurement Circuit for Wet Tantalum Capacitors in Parallel

Applying a voltage across pins J1R and J1M while monitoring the supply output current can assess leakage current through the parallel 270 UF capacitors.

3.2.3.2 Ceramic Capacitor Failure Due to Manufacturing Defects

Ceramic capacitor samples studied in the past that are identical to those found in the rotary switch had manufacturing defects such as voids and delaminations. This included ceramic capacitors on the circuit boards, as well as in one of the EMI filters. Although the manufacturing defects themselves are not a problem (since the capacitor meets its rated electrical specifications), they are a mechanical stress point for fracture of the ceramic material as the capacitor is overstressed or subjected to repeated cycles of stress.

Any defects noted can be traced back to a specific manufacturer and production dates since the components have manufacturer and date codes.

The only way to know whether or not a ceramic capacitor has an internal void or delamination is to destructively cross section the component and examine it under a microscope. For the A&S program, there may be some benefit gained from inspecting the ceramic capacitors from sample rotary switches in order to characterize the extent of such defects, and to look for components that may have failed. Note that many of these components are used as “filter capacitors,” which typically cannot be tested adequately in-circuit because their function is often to provide a high-pass filter for electrical noise (bypass to ground). Environmental stress testing of the rotary switch is the best way to find these problems outside of destructive testing.

3.2.3.3 Inductor Insulation Degradation

There are 19 wire wound inductors identified in the schematics for the EMI Filter used in the Rotary Switch. They include seven 200 uh, four 250 uh, four 30 uh, and four 400 uh devices that are built to the requirements specified in the engineering document. The inductors are all encapsulated in the potting inside the EMI Filter housing and are used in filtering the various input signals. The ASIA identified possible insulator degradation that could lead to unacceptable shorts.

30 UH

30 UH 30 UH

30 UH

1.5 UF

1.5 UF

270 UF 270 UF

J1 Pin R

J1 Pin M

Open connection with detent pin installed

Exact measurement of individual inductor resistance and visual inspection is required to assure that they might be the root cause of short circuits due to insulation degradation.

This method would require destruction of the EMI Filter metal case and potting in order to individually test each inductor. Since no destructive tests will be included in the ALCM A&S Program, a modified capability for the inductor resistance measurement in a non-destruct test can be implemented. The filter design coupled with its application in the rotary switch allows for non-destructive measurement of the combined resistance/impedance of the circuits that employ the inductors. The following diagrams depict typical measurement circuits that are accessible in the rotary switch when the cover is removed.

(a) Single Inductor Circuit

(b) Multiple Inductor Circuit

Figure 4. Typical Measurement Circuits for Inductors Configured in the EMI Filter

Measurement of the resistance/impedance for these circuits would require removal of the rotary switch cover and probing at the applicable interconnects. In some instances the series resistance/impedance will have to be monitored.

3.2.3.4 Wire Chaffing

Functional testing of the rotary switch under environmental stress screening to include thermal and vibration stress can best identify wire chaffing.

30 UH

30 UH 30 UH

30 UH

1.5 UF

1.5 UF

270 UF 270 UF

J1 Pin R

J1 Pin M

Open connection with detent pin installed

200 UH

0.22 UF

J1 Pin C

3.2.3.5 Solder Manufacturing Defects

This manufacturing issue in the rotary switch can best be identified by visual inspection, but may also be found by testing the device under a thermal and vibration stress test.

3.2.3.6 Insulator Pad Degradation

The rotary switch uses an insulator pad between the top of the relays and the rotary switch cover. Wire chafing and solder defects combined with conformal coating degradation could lead to failures due to shorts in the rotary switch. Visual inspection and environmental stress testing are the best methods of characterizing these problems.

3.2.4 Visual Inspections

The visual inspections identified for inclusion in the Rotary Switch A&S Program include: corrosion/contamination of housing, exposed surfaces of nylon guide for detent pin insertion, and ball bearings, corrosion/degradation of electrical connector pins, degradation of the housing cover o-ring seal, and circuit board conformal coating degradation.

3.2.4.1 Corrosion/Contamination of Housing, exposed surfaces of nylon guide for detent pin insertion, and ball bearings

Corrosion: Inspect all surfaces of the aluminum and steel components for evidence of corrosion. Discoloration or the presence of surface deposits may indicate corrosion.

If corrosion is suspected in any of these areas, examine them in more detail with the aid of a microscope (approximately 30X). Any evidence of corrosion should be photographed for documentation purposes.

Corrosion/Contamination: A portion of the nylon guide insertion port for the detent pin can be visually inspected at the rotary switch assembly level. Inspect the guide for any indications of excessive roughness and wear from repeated insertion and removal of the detent pin, or contamination from external environments. Inspect the exposed surfaces of the ball bearings used to retain the detent pin for signs of corrosion and/r contamination. Examination under a microscope (approximately 30X) may aid the inspection. Any evidence of damage to the ball bearings should be photographed for documentation purposes.

3.2.4.2 Corrosion/Degradation of Electrical Connector Pins

A visual inspection of the electrical connectors is recommended to look for corrosion and degradation/copper diffusion on the connector pins. In addition any degraded electrical contact when mated will be detected during functional testing to help monitor this aging condition.

3.2.4.3 Housing Cover O-Ring Seal

A visual inspection of the O-ring should be performed to look for cracking and changes in cross section due to compression set. Thorough evaluation of the O-ring will require that it be removed from the housing. The cover O-ring is the most convenient to use because of its size. An elongation test can be used to check for embrittlement of the material. A durometer (hardness) test can be performed on the O-ring, although the test may need to be repeated several times in order to get meaningful results (the small material volume can affect the test). A visual inspection of the O-ring should also be performed to look for cracking and changes in cross section due to compression set.

3.2.4.4 Circuit Board Conformal Coating Degradation

Conductor cracks that fail open may be detected during ground testing such as An ESTS Level I or Level III test, and Service STAR testing. However, it is possible to have fatigue cracks in the conductive paths that close and maintain the electrical connection under static conditions and open or short to outside circuits under operational conditions.

Thus, a visual inspection of the circuit board is recommended to look for degradation of the conformal coating and fatigue-related cracks in the conductors. Also, a functional test when the Rotary Switch is in under an applied environment of vibration and temperature extremes should identify such aging problems.

3.2.5 Environmental Tests

The complete suite of acceptance tests are outlined in Rotary Switch, Individual Acceptance Test Procedure, 76410 ATP2, Section 4.0 include the original environmental tests used for production line acceptance. These tests should be used to help establish test parameters. The environmental tests for the Rotary Switch should include: Leak Test, and Vibration/Temperature Tests.

3.2.5.1 Leak Tests

There are no exact requirements for a leak test on the rotary switch in the product specification, Boeing Document 232-30040. The Acceptance Test Procedure for the device, VACCO Industries Document 76410 ATP2, calls out for a leak test during acceptance testing, however, no specifics for the test or detailed requirements are provided. The Depot Maintenance Technical Order for the Rotary Switch, TO 11N- C5033-3, details a helium leak test following any maintenance that violates the seal integrity. The test described in the manual is virtually identical to those defined via specification for the WAD and the Air Launched Cruise Missile Arm/Disarm Device.

A helium leak test, based on the test described in the Technical Order, can be developed for A&S test purposes to evaluate embrittlement or compression set of O-ring seals, or identify gross failure (cracks) in the housing components of the rotary switch.

A leak test port screw, a 3/8 X 6-32 machine screw located adjacent to the J2 connector on the rotary switch, was designed into the device as a means of conducting leak tests as part of the production line acceptance test procedure. That screw port can be removed so that a special pneumatic fitting can be installed. Then, the rotary switch internal environment can be evacuated for performing a pressure decay test or pressurized with a mixture of nitrogen and helium so that a leak test can be performed.

The housing seal integrity test is considered to be non-destructive. However, it will be necessary to follow the repair procedures in the technical order before the rotary switch can be re-used since some touch-up paint will be necessary when the port screw is replaced.

The helium leak test should include purging of the rotary switch (prior to sealing) with a mixture of nitrogen and helium, of which 4.75% to 5.25% shall be helium. The helium will be used as a tracer gas that can be detected with standard leak detection equipment.

The rotary switch should be pressurized with the mixture to 1 PSIG. Following a 45 second delay the leak rate should be measured. The Technical Order notes a maximum leakage rate of 1 x 10-6 standard atmosphere cubic centimeters per second. The rotary switch should be purged and back filled with air to standard atmosphere following the leak test.

A pressure decay test could be considered as an alternative approach, although it would not be as sensitive as a helium leak test. Under this method, the housing should be pressurized to approximately 10 psi (this value was arbitrarily chosen, lacking specific manufacturing or maintenance documentation), and then the supply valve should be shut while the housing internal pressure is monitored. The pressure should be monitored over a period of 2 or more hours to detect leakage. The temperature of the housing and internal gas will need to remain constant during the test. Pass/fail criteria for an acceptable leakage rate will need to be established during the A&S program.

3.2.5.2 Vibration/Temperature Tests

Environmental tests can be used to detect aging conditions that are not evident during inspection and/or static/bench level testing. These conditions include such things as degraded or cold solder joints, relay contact chatter, and chaffed wire anomalies.

For testing under environment, the Rotary Switch Requirements Specification (232- 30040) specifies random vibration test levels for each of the three axes as follows:

Frequency Spectrum Level

10 Hz to 34 Hz 0.0015 g2/Hz, steady state 34 Hz to 100 Hz 0.0015 g2/Hz to 0.015 g2/Hz, linear ramp 100 Hz to 2000 Hz 0.015 g2/Hz, steady state

Table 2. Random Vibration Levels

For testing under environment, the Rotary Switch Requirements Specification (232- 30040) specifies the following temperatures and durations:

Temperature Duration

Ambient (72F) 2 Hrs 40 minutes

-65F 2 Hrs 40 minutes +160F 2 Hrs 40 minutes

Table 3. Temperature Test Levels

The recommendation for A&S testing, based on the Rotary Switch Requirement Specification and the goals of the A&S program, is for performing vibration per Table 2 above for each axis at temperature for the duration of one functional test (about 10 minutes at each axis). To provide a functional test under environments for the A&S program these temperature and vibration levels can be combined with functional testing at each axis as follows:

Temperature Soak Duration Vibration Duration Axis

+160F 120 minutes 10 minutes X

Ambient (72F) 120 minutes 10 minutes Y

-65F 120 minutes 10 minutes Z

Table 4. Combined Environmental Test Levels

Notes: 1. Temperature ramping shall not exceed 5F per minute.

2. Vibration profile is included in the final 10 minutes of the temperature soak.

3. Functional Testing of the Rotary Switch occurs during the vibration period at the end of the temperature soak.

IV. TEST EQUIPMENT AND FACILITES REQUIREMENTS

The following table presents a list of equipment and facilities required for testing of the rotary switch per the test methods described in Section 3.2. Re-use of the A&S Test Complex developed for the ACM NWSS components limits new equipment and facility requirements as Manufacturers and part numbers are included where specific recommendations can be made, but equivalent equipment can be used. In some cases, only general requirements or a possible commercial source may be identified since the components will need to be selected and designed into a custom test fixture. High quality photographic documentation will be important to the A&S program. A digital camera system is recommended (which will allow direct archiving to computer disk) in addition to film-based photographic equipment.

Equipment Item Suggested Mfg. and P/N or

Description Used For

Microscope (adjustable zoom to at least 30X), with camera mount

Nikon, Zeiss, Bausch & Lomb;

with camera adapters for SLR, Polaroid, and digital cameras

Visual inspection

Light for microscope halogen light and fiber optic light ring; Sunnex, Leica Visual inspection

Photography system SLR, Polaroid, and digital cameras with MP4 photography stand

Visual inspection

MTS-8 Aging & Surveillance Test Set GFE Multiple requirements

AGREE Vib/Hum/Temp Chamber GFE Multiple requirements

Durometer GFE Hardness test on O-Ring

Positioning axis with position feedback linear motion, 1” stroke or more, 0.0001” resolution; Dillon or Intelligent Actuator Corporation

(IAC)

Measurement of switch actuation vs.

plunger travel;

Measurement of spring plunger force;

O-ring elasticity test

Force transducer 0-30 pound range;

Dillon AFG 250N

Measurement of spring plunger force;

O-ring elasticity test

Helium leak tester Varian 959 with custom fixture hardware, GFE Housing seal integrity test

Nitrogen compressed gas bottle instrument grade inert gas Housing seal integrity test

Test Fixture (custom) use for several tests

Measurement of spring actuation vs.

plunger travel;

Measurement of switch transfer time;

Measurement of plunger spring force

Table 5. Equipment and Facilities Required for Testing the Rotary Switch

V. AGING & SURVEILLANCE STORAGE ENVIRONMENTS

Aging storage environments should be representative of the actual operational aging storage environments experienced by the components deployed to the field. Dedicated A&S component samples will be maintained in the storage environment, and will periodically be removed for testing to gather parametric data necessary to characterize the aging mechanisms. The total number of samples recommended for the A&S program is specified in Section 6.3.

One concern for the rotary switch is moisture ingress past the pull-out pin and into the actuator switch springs and plunger o-ring seal. Thus, it is recommended that the rotary switch be stored in an environmental chamber that simulates temperature and humidity variations (temperature variation will drive moisture in and out of the rotary switch if the O-ring is not sealing properly). Recommended parameters for temperature and humidity variation need to be developed based on climatic data for typical storage environments, but should include the extremes of summer months in hot weather storage locations, the extremes of winter months in cold weather storage locations, and the extremes of humidity for typical storage locations.

The simulated storage environment should reflect the temperature and humidity variation experienced by the component when the missiles are stored in igloos at various environmental locations (both hot and cold). The weather stations at operational bases (referred to as MOB 1 and MOB 2) were contacted and, as a result of our discussions, they provided historical data on actual site temperature and humidity variations. MOB 1 provided the information detailed to the daily variations, while MOB 2 provided monthly averages, highs, and lows. Plots of the temperature and humidity comparisons for the MOBs are shown below.

Figure 5. Temperature Variances for MOB 1 and MOB 2

Temperature Comparison

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

MOB 1

MOB 2

Figure 6. Humidity Variances for MOB 1 and MOB 2

The recommended temperature storage environment for the rotary switches is 3 months at 70F 5F, 3 months at 100F 5F, 3 months at 70F 5F, and 3 months at 0F 5F. The fall and spring temperature averages for both MOBs are close enough that the recommended cycle is a close approximation for both. The winter months at MOB 1 are much colder than MOB 2; therefore, the recommended variations over the winter months follows MOB 1 averages. Similarly, the summer averages at MOB 2 are much higher than MOB 1, and the recommended variation follows MOB 2 averages

The recommended humidity storage environment for the rotary switches is 3 months at 50% RH, 3 months at 80% RH, 3 months at 50% RH, and 3 months at uncontrolled RH.

These levels account for the variances between the MOBs and the limitations imposed by artificial environmental controls.

Since all rotary switches, those installed in missiles and those in spares inventories have the pull-out pin installed (except during ground tests) the dedicated A&S samples should be stored with the pins installed. The pull-out pins should be removed once annually, reflecting typical test cycles.

Humidity Comparison

J a n

F e b

M a r

A p r

M a y

J u n

J u l

A u g

S e p

O c t

N o v

D e c

Month

R e la ti v e H u m id it y

MOB 2

MOB 1

VI. A&S TEST REQUIREMENTS

6.1 Test Classifications

Three environmental levels are generally applied to long-term laboratory test programs developed for aging and surveillance purposes for nuclear weapon components. Those include “ambient,” “hard,” and “destructive” test levels. The ambient level determines whether the aging environment (i.e., storage and periodic maintenance) affects the performance characteristics of the hardware. The hard environment includes the application of vibration, shock, and/or temperature excursions to determine if the hardware is capable of performing in a flight environment after being subjected to the aging environment. The destructive environment is required to capture parametric data not available through non-destructive means. Given program constraints, the ALCM A&S Program will not include tests that fall under the “destructive” test level. In the event an age-out problem is detected, the multi-level test approach used for ALCM will allow a comparison to help determine if the problem is due to aging alone, or if it is caused by the interactive effect of aging and the service environment.

6.2 Test Types

The test classifications (ambient, hard, and destructive) are further characterized by definition of the types of tests conducted within the classification. Five specific test types have been defined for the ALCM A&S Program. Baseline “A” Tests and Interval “B” Tests comprise the ambient classification, while three Comprehensive “C” Tests (C1, C2, and C3) fall within the hard environment classification.

6.2.1 Baseline “A” Tests

These tests are non-damaging tests that establish the health of each parameter of interest.

In as much as the ALCM A&S Program development was started well after the production lines were shut down and the hardware delivered to the Air Force, it is impossible to capture data at true time t0 (typically referred to as zero-time data).

Therefore, the baseline should be established by testing a number of samples in the first test year.

6.2.2 Interval “B” Tests

These tests are non-damaging tests that are made on dedicated A&S samples. These dedicated samples should be stored in a controlled environment that emulates the aging environment of the operational fleet, as recommended in Section V. A comparison of the cumulative “B” test data from year to year with the previously established baseline will determine if the aging environment is causing degradation.

6.2.3 Comprehensive “C” Tests

Comprehensive tests include pre-environment tests (C1), tests during environment (C2), and post-environment tests (C3). Comprehensive tests are designed to include the baseline parameters as well as functional performance parameters.

6.3 Test Sequence

The following table shows the recommended A&S tests to be accomplished for this component. In all cases, baseline “A” tests are required to establish a point of reference for comparison of future test results. Interval tests “B” are required to monitor aging of dedicated A&S storage environment samples. All “C” tests are conducted using rotary switch samples that have been returned from the field.

A&S Test Method Aging Mechanism A B C1 C2 C3

Rotary Switch Assembly Level Tests

Visual Inspection, External Moisture/contamination build up in pull-out pin receptacle, see 3.2.4.1

Corrosion of housing, see 3.2.4.1

Corrosion/wear on pull-out pin, see 3.2.4.1

Damaged connector pins, see 3.2.4.2

Corrosion of connectors, see 3.2.4.2

Circuit Board Conformal Coating Degradation

Functional Test

Functional Test Confirm basic functionality, see 3.2.1

A&S Unique Tests

Actuator Switch Contact Timing

See 3.2.2.1

Actuator Switch Contact Resistance

See 3.2.2.2

Detent Pin Extraction See 3.2.2.3 Detent Pin Insertion See 3.2.2.4 Relay Tests See 3.2.2.5 & 3.2.5.2 Capacitor Leakage Current See 3.2.3.1

Housing Seal Integrity Tests

O-Ring Seal Integrity See 3.2.5.1 O-Ring Seal cracking and compression set

See 3.2.4.3

Table 6. Recommended A&S Tests

Section VII includes the detailed Environmental Test Plan Measurements List.

The block diagram in Figure 6 illustrates the recommended test sequence. The first step will be a visual inspection of the rotary switch to look for externally visible housing corrosion, connector damage, and possible handling damage. To the extent possible, the opening for the pull-out pin should be inspected for signs of contamination build up, moisture, corrosion and deterioration within the actuator housing.