How to Establish Electrical Grounding in Airplanes

The design of a fully-functional aircraft is incomplete without the presence of a robust grounding and bonding electrical system. This is because improper grounding can lead to several in-flight accidents from an over accumulation of electrostatic charge. Moreover, the subsequent discharge and voltage fluctuations of all connected devices can lead to the overall rise in the risk of shock hazards. However, that is not all; electromagnetic interference from the atmosphere and lightning strikes during stormy weather conditions pose additional threats. Therefore, this blog will shed some light on how electrical grounding in airplanes can be established to prevent such scenarios from emerging.

Most all-metal airframes in modern aircraft require single-wire systems in their electrical circuits; wherein only one wire is needed to connect all electronic devices to the common source of electromotive force—whether that be an alternator or battery. However, some aircraft also use two-wire systems to suit their requirements. Grounding is a process where a connection is established between the conducting object and the source of the primary structure (such as the metal airframe, fuselage, or the plane's wings) to complete the circuit where the current can return.

A sound grounding system should always feature energy and lightning absorption, low internal impedance, and fault protection, apart from promising quick installation and easy maintenance. The usage of copper meshes within aircraft grounding framework enables the establishment of an appropriate Faraday cage. A Faraday cage can be defined as a shield that localizes or blocks specific electromagnetic radiation. It works on the hypothesis that when an electromagnetic field intercepts a conductor, the charges accumulate on the conductor's external surface instead of traversing the conductor.

The manufacturing of most commercial aircraft today involves using a conductive metallic material, such as aluminum. Consequently, the electrical grounding of such aircraft demands the connection of most electrical appliances to either some metallic structure, such as the aircraft body itself, or to another typical source of common return for all electrical connections.

Suppose the grounding system conducts electricity from two different sources: DC and AC. In that case, a net accumulation of the different types of current can increase noise for any digital device connected. This is why designing current grounding circuits demand utmost precision and attention so that current mix-ups and the dangers they pose can be avoided. Ideally, ground return circuits must have adequate current ratings and voltage drop measurements so that all connected devices can be checked for compatibility before installation.

The Process of Aircraft Grounding

Aircraft needing electrical grounding do not always have to be physically present "on the ground," as their name might imply. Instead, grounding refers to building an aircraft circuit with low inherent resistance that contains the capacity to carry high volumes of electrical current until dissipated.

While choosing the metal airframe of an aircraft as the common grounding object may seem like a viable solution, this can cause various problems to arise because of the insulation present in airframes, types of materials used in applied paints, poorly placed rivets, and corrosion. All these factors may contribute to the decrease of conductance, leading to frequent voltage drops and an overall increase in resistance. Most aircraft today come equipped with static wicks, which are electric dischargers that release an excessive build-up of static charge into the atmosphere to combat this design flaw. However, in their absence, technicians must ensure that all primer, paint, anodized film surfaces, grease, and other foreign substances are completely scraped off from the metal surface before the installation process begins. 

Most grounding systems employ either of the two grounding circuits:

Single-wire: This system depends on the aircraft's body to be an electric conductor.

Two-wire: This system needs every device connected to the power source to have at least two wires, where one is the "power" wire, and the other is the "return" wire. Both of these wires are connected to a central master ground which is coupled with a thick wire to the battery.

With that said, most modern aircraft use single-wire systems for their grounding needs. Given below is a step-by-step process of their installation and connection:

  1. Establishing a good engine ground: This is done by connecting a metal grounding strap or the end of a heavy cable to the nearby bolt of an engine crankcase. This connection ties the common electrical ground with the engine, and care should be taken to avoid the non-conducting rubber shock mounts present anywhere along the way.

  1. Connecting P-leads to the magneto wires: When an engine is first installed, the magneto wires immediately throw off any plugs connected to them as soon as the propeller is moved slightly. However, when P-leads are connected to these magnetos, they are electrically grounded through the ignition switch.

  1. Shielding: This process involves encasing a magneto wire within a metal braid so that high-frequency voltages can be dissipated within the cable shield itself, rather than in nearby circuits where they might cause electrical disturbances. Usually, both ends of the shielded wire are grounded to prevent the cable from emitting any radio frequencies.

Do's and Don'ts With Aircraft Grounding

Adhering to a manufacturer’s instruction manual from start to finish is not enough to establish a fully-functional aircraft grounding system. In addition, there are precautions that should be taken to optimize the function of a grounding system:

Do's

1.The overvoltage relay and voltage regulator should be grounded, even if the instructional schematics may not display this regulation explicitly.

2.Freshly-cleaned aluminum surfaces should be treated with a suitable conductive chemical substance, such as Alodine, within 24 hours of removing the finish.

3.The same type of hardware used in the original connection should be used during repair and replacement.

4.Heavy current-load devices such as batteries, external power compartments, and transformer rectifiers should be connected to individual grounding brackets through metal-to-metal bonding to the overall aircraft grounding system. Such connections should offer sufficient conductivity to adjust the aircraft's normal and fault currents.

Don'ts

1.Magnesium parts should not be included in the grounding system at any point.

2.Freshly established grounding connections should be treated with suitable non-corrosive sealants to avoid corrosion due to exposure to saline atmospheric conditions.

3.Fault current ground connections should be avoided within flammable environments.

4.Ground attachments should not be made within close proximity to one another to avoid the loss of multiple power systems.

Wrapping Up

If you are looking for top-notch electrical grounding and bonding components, then NSN Axis is here to help. Being a premier supplier of the most in-demand aircraft parts, you can rely on our expansive supply network featuring top manufacturers to procure the part of your choice delivered in record time! Moreover, our dedicated team of account managers will ensure that you get all the help you need throughout the entire part procurement process. We encourage you to make an inquiry using our Instant RFQ service available on our website to get started.


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