Business & GA, Commercial

Product Focus: Connectors

By Capt. Edward R. Hanson Jr. | July 1, 2001
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CONNECTORS, quite apparently, join different materials or segments of a material together. There is nothing mysterious about the connector’s function. However, the durability and environmental stress tolerance that they must possess make them potentially the strongest link in a wire chain. The connector is the second suspect in any electrical equipment malfunction. (The first suspect is the circuit breaker.)

The nice thing about connectors from a pilot’s point-of-view is how little we need to be concerned with them. They seem to always work and rarely cause problems. There is a reason for this. Connectors have been engineered to solve a particular application requirement in a specific manner. And they have improved over the years.

If you look at a cockpit panel on older Boeing equipment you will notice little "+" symbols among the switches, gauges and dials. Aviation tradition has it that these pluses are where the pilots should firmly tap the panel if they question the integrity of the connections behind it. KC-135, Boeing 707, 727 and 737 all have these little "contact embellishment" points. Pilots typically tap a panel when its integral lights don’t illuminate. A few well-positioned taps and the lights begin to work. The industry has come a long way since those "tap the panel, beat on the gauge" days.

Pilots are well aware of the ubiquitous "cannon" plug, a screw-on connection usually found in the back of radio racks. These plugs rarely malfunction but are not necessarily impervious to moisture. When an avionics application ceases to work with no obvious external symptoms, the ace mechanic usually checks the cannon plug.

Newer aircraft have multipin connectors and bayonet-style couplings in the electrical equipment (E&E) compartment, where there are high-electrical-draw items. The E&E compartment usually sits directly beneath and behind the cockpit on the same level as the baggage bins. When the cockpit electronic flight instrument system (EFIS) displays a status message regarding an on-board system, the crew notifies the technicians, and they typically will attempt to "rerack" the offending component before proceeding with more complicated troubleshooting. Reracking affirms that all component connections, particularly multipin connections, are secure.

Many connectors are required to protect circuits from electronic interference emanating from closely bundled, other components, as well as from interference external sources. The last thing an aircraft needs is a connector that "leaks" and allows electromagnetic contamination into the system. Therefore, some connectors are filtered to suppress contaminants.

Other connectors are not so ambitious. They merely facilitate wire-to-wire splicing in a lap joint. Here, a soldering sleeve contains an internal solder flux that melts at a predictable temperature and an external shell that shrink-wraps and forms an environmental moisture barrier. The shrink-wrapped shell provides some strain relief to the wire. Sometimes the flux material changes color to indicate that the connection is appropriately made–which makes for easier inspection.

We are all familiar with coaxial cable connections, used for signal transmission to our televisions from the service provider or an antenna. Myriad devices on-board a commercial airliner use the same type of connection. Coaxial cable applications include all the VHF and HF radios. Here, the same problems that can occur at home can happen in an aircraft. If the coaxial cable is crimped inappropriately, the signal can be degraded and the device the cable supports made inoperable. Coaxial cable is tough, but the environment can be tougher.

Fiber optic connections represent the future. Flight-by-wire is giving way to flight-by-light, and fiber optics’ information-carrying capabilities make it a choice candidate for applications such as advanced technology flight controls. Flight-by-light captures engineering imaginations because fiber optics saves weight. And generally, on modern air carrier jets, every thousand pounds of extra weight costs 40 pounds (18 kg) of fuel per hour to carry.

The ubiquitous connectors join sensors to processors and processors to displays. The right connector for the right application will provide years of trouble-free service.


Aeroflite Enterprises [email protected]
Air Electro
American Connector Corp.
Ametek Aerospace
Amphenol Aerospace
Array Connector Corp. 305-234-1000
Electro Enterprises
Electronic Cable Specialists
Excalibur Systems Inc.
Hirel Connectors
HS Electronics Inc. 305-821-5802
Intro Corp.
J&K Connectors
Marine Air Supply
Microdot Connectors
Omnetics Connector Corp.
PIC Wire & Cable
Radiall – Jerrik
Spacecraft Components
Tri-Star Electronics International
Trompeter Electronics
Tyco Electronics (Raychem)
Wings Electro Sales Co. Inc.

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