| Aerospace relays are electrically controlled devices | | | | electrical connections. The use of properly calibrated |
| that open and close electrical contacts to effect the | | | | torque wrenches and following the manufacturer's |
| operation of other devices in the same or in another | | | | installation procedures is strongly recommended. This |
| electrical circuit. The relay converts electrical energy | | | | is especially important with hermetically sealed relays, |
| into mechanical energy through various means, and | | | | since the glass-to-metal seal (used for insulation of |
| through mechanical linkages, actuates electrical | | | | the electrically "live" components) is especially |
| conductors (contacts) that control electrical circuits. | | | | vulnerable to catastrophic failure as a result of |
| Solid-state relays may also be used in electrical | | | | overtorquing. |
| switching applications.a. Use of aerospace relays. Most | | | | (1) When replacing relays in alternating current (ac) |
| relays are used as a switching device where a weight | | | | applications, it is essential to maintain proper phase |
| reduction can be achieved, or to simplify electrical | | | | sequencing. For any application involving plug-in relays, |
| controls. It should be remembered that the relay is | | | | proper engagement of their retaining mechanism is |
| an electrically operated switch, and therefore subject | | | | vital. |
| to dropout under low system voltage conditions.b. | | | | (2) The proximity of certain magnetically permanent, |
| Types of Connections. Relays are manufactured with | | | | magnet assisted, coil operated relays may cause |
| various connective means from mechanical to plug-in | | | | them to have an impact on each other. Any |
| devices. Installation procedures vary by the type of | | | | manufacturer's recommendations or precautions must |
| connection and should be followed to ensure proper | | | | be closely followed. |
| operation of the relay.c. Repair. Relays are | | | | Aerospace switches. |
| complicated electromechanical assemblies and most | | | | LOAD CONSIDERATIONS. |
| are not repairable.d.Relay Selection. | | | | When aerospace switches or aerospace relays are to |
| (1) Contact ratings, as described on the relay case, | | | | be used in applications where current or voltage is |
| describe the make, carry, and break capability for | | | | substantially lower than rated conditions, additional |
| resistive currents only. Consult the appropriate | | | | intermediate testing should be performed to ensure |
| specification to determine the derating factor to use | | | | reliable operation. Contact the manufacturer on |
| for other types of current loads. (Ref. | | | | applications different from the rated conditions. |
| MIL-PRF-39016, MIL-PRF-5757, MIL-PRF-6016, | | | | OPERATING CONDITIONS FOR SWITCHES AND |
| MIL-PRF-835836.) | | | | RELAYS. aerospace switches and aerospace relays |
| (2) Operating a relay at less than nominal coil voltage | | | | should be compared to their specification rating to |
| may compromise its performance and should never | | | | ensure that all contacts are made properly under all |
| be done without written manufacturer approval.e. | | | | conditions of operation, including vibration equivalent |
| Aerospace relays Installation and Maintenance. For | | | | to that in the area of the aircraft in which the switch |
| installation and maintenance, care should be taken to | | | | or relay is to be installed. |
| ensure proper placement of hardware, especially at | | | | |