Aircraft rely on numerous on-board systems that provide crucial data for safe flight. To support these systems, a complex network of cables, known as the Electrical Wiring Interconnect System (EWIS), Grommet Edging runs through the fuselage, often in tight spaces. These cables pass over sharp edges, which, if not properly protected, may cause abrasion—leading to data loss, system failure, or even fire at high altitudes.
Traditional wiring protection methods, dating back to the 1950s, involve using nylon grommet strips (MS21266/ BACG20Z) and adhesive, but these are time-consuming and costly to install, and provide unreliable protection on edges.
Spring-Fast grommet edging is a more effective wire protection solution from manufacturer DTi device technologies GmbH (DTi GmbH). It has been specifically designed to apply by finger pressure and without adhesive. This simple installation process is 49% more cost-effective and boosts productivity by 9.5 times, eliminating the need for additional materials like adhesives, gloves, masks and solvents.
Now DTi GmbH has launched a new Spring-Fast variant M22529/3, that is specifically designed to securely fit flanged edges without adhesives.
It resists flight stresses like vibration and extreme temperatures, offering superior protection against abrasion and maintaining the 49% costs savings and 9.5X productivity increase.
Aircraft have a multitude of on-board systems that need to communicate to ensure smooth safe operation. These systems are almost all connected with cables. This cabling system is broadly known as the EWIS – the Electrical Wiring Interconnect System, and itexists in all aircraft: commercial jets, ATR turboprops, Gulfstream, Embraer or Dassault executive jets and Pilatus, Grob, Piper, Diamond, Daher/Socata or Cessna general aviation aircraft.
The EWIS is the “nervous system” of every aircraft, as it maintains and supports the functionality of all aircraft systems.
For example, a narrow-body commercial airliner such as the Boeing 737NG has an EWIS with as much as 60 kilometers (~37 miles) of wiring while the EWIS of the Airbus A380 reportedly has more than 450 kilometers (~280 miles) of wiring.
Almost all wiring is routed at some point through penetrations which are strategically located in the aircraft structure like lightening holes or conduits for wire, cables, fluid and pneumatic lines. These penetrations are designed to be as small as possible so as not to weaken or reduce the mechanical integrity of the structure. However, this can result in clearances between the wiring and the airframe as small as 6mm (1/4 inch).
“If wiring under stress starts to make contact with the fuselage it will create chafe which can lead to a wide range of issues: at the low-end it will be annoying system discrepancies and data loss but at the other end it can mean life threatening system failure, arcing/sparking or fire. Not exactly a pleasant thought when you’re experiencing turbulence or when you are eight kilometers (five miles) in the air”, says Nick Petri, President of DTi GmbH.
That’s why service technicians inspect the wiring in the EWIS to prevent this from happening. However, a substantial portion of aircraft wiring is not easily accessible or visible for inspection which means technicians may not see a wire that is starting to chafe.
In addition, it gets more complicated because of the two key types of edges on aircraft: un-flanged and flanged edges. Flanged edges require grommets that are flexible in three axes (X, Y, and Z directions) – something nylon grommet strips cannot provide.
Grommets Have an Operational Impact Far Greater Than their Size
Flanged edges are especially common in older or retrofitted aircrafts, making wire protection more challenging on such platforms. OEMs use glued-on nylon grommet strips on the edges of penetrations to protect against wiring chafe but they do not work well on flanged edges.
Nylon grommet strips present many other problems: the application itself is long, slow, and costly. The glue application is a non-standard process and can often lead to dis-bonding on the first attempt. In addition, nylon has a tendency to dry out and become embrittled when exposed to heat or cold repeatedly. “However, there is a bigger issue. Regular flight conditions include wide swings in temperature. This expands and contracts the metal edge, the grommet strip and the adhesives that keep it in place – but at different coefficients. Over time it creates a shearing action that cracks the nylon and/or the adhesive which reduces wire protection and introduces Foreign Object Debris (FOD) into the aircraft.” says Petri. Although data on wiring degradation is hard to find, our 40 years of application engineering research shows that when aircraft were designated as AOG (Aircraft on Ground) or NORS (Non-Operational Ready Status), the biggest single reason – at 37% – was wiring discrepancies attributed to chafe. These discrepancies can affect any system and can be a significant drag on readiness, availability, and efficiency which in turn impacts medium to long-term operational costs and profits.
Protecting the EWIS is important as its affects flight safety. OEMs want the best products but business pressures from rising costs and supply chain issues are driving the search for solutions that improve productivity and lower costs.
These pressures are at the core of why many OEMs as well as MRO/FBOs are switching from the old, glued nylon grommet strips to the Spring-Fast grommet edging developed by manufacturer DTi GmbH.
Innovation Replaces Nylon
According to Petri, Spring-Fast grommets offer top-tier performance, are lightweight, and provide excellent retention strength. They can be easily installed or removed in seconds using just finger pressure, without the need for glue. As a result, manufacturers can save at least 49% of their installation costs compared to traditional bonded nylon grommets.
Protecting the EWIS is critical for aerospace and DTi GmbH has designed three EASA Approved Spring-Fast products for this purpose.
The newest product in the Spring-Fast range is the M22529/3 (M/3), which features an encapsulated steel substrate with opposing castles, which give it multi-axis flexibility, making it ideal for roll-formed and flanged penetrations. A sacrificial cushion increases abrasion resistance.
In contrast, the M22529/2 (M/2) has alternating castles which give it 2-axis flexibility even on right angle corners (90-degree bends). “These castles, or gripping teeth, on all three products angle into the edge creating a compression force that gives strong edge retention which has been static load tested on 3 axes to 20 G”, says Petri. The sacrificial cushion increases abrasion resistance.
Lastly the M22529/1 (M/1) offers an encapsulated steel substrate with alternating castles which give it 2-axis flexibility- again even on right angle corners (90-degree bends). This is a low-profile variant without a sacrificial cushion, which are often used on ground-based systems.
“Since weight is always a concern in aviation, it should be noted, that despite the steel core of the M22529 series, there is no weight penalty compared to nylon and its required adhesive”, Petri adds.
All three types of the M22529 are easy to work with and excellent for tight access locations because it is simply pushed onto the edge with finger pressure and it locks in place on flanged or un-flanged edges without adhesives. This can speed up initial construction, and is far easier to install when working around existing wiring harnesses.
This minimizes the production or set-up time from several minutes to a few seconds which boosts task productivity by a factor of 9.5X. However, it can be easily removed and replaced without loss of edge retention. In combination, these benefits lead to an overall installation cost reduction of at least 49% compared to nylon grommet strips and glue.
The three M22529 products are also safer and greener than nylon. This contributes to a safer work environment as it requires no VOCs from adhesives or MEK-based solvents necessary for clean-up. From an operational safety and liability point of view it has a low Foreign Object Debris (FOD) footprint as far fewer shop consumables such as gloves, cloths, adhesive, tape, solvent, and masks need to be brought onto the aircraft.
“In summary, Spring-Fast is a lower cost, higher efficiency and higher performance grommet edging as well as being a greener alternative to nylon strips with adhesive. Free samples are available on our website if you would like to see for yourself.”, concludes Petri.
