When I first got a call from an aerospace components engineer last year asking, “Can your plastic terminal block cases hold up in a jet engine’s wiring harness?” I didn’t jump right to a yes or no answer. As someone who’s spent the last twelve years running my small custom plastic case and terminal block shop—we’re the ones manufacturers call when off-the-shelf parts won’t cut—I knew this wasn’t a question of “plastic vs. metal” but of matching the right material to the exact aerospace requirement. That day, I dug through our material data sheets, tested a sample case in our environmental chamber, and even sat in on a conference call with an aircraft wiring team to get the real details of what their systems face. By the end, I realized this is a conversation every engineer, every supplier, and every aerospace maintenance shop needs to have, because the answer isn’t a hard yes or no—it’s a “when these conditions are met, and here’s how we make it work.” Plastic Case and Terminal Block
First, let’s break down what aerospace applications actually demand of terminal block cases, because not all aerospace parts are the same. The FAA doesn’t have a one-size-fits-all rule for plastic components in aircraft wiring, but there are a set of standards that everyone in the industry references. For commercial airliners, the most common specs are DO-160 for environmental testing and DO-178 for software, but when it comes to physical parts, we’re talking about things like vibration, temperature extremes, flammability, and resistance to fluids like jet fuel, hydraulic oil, and cleaning agents. For general aviation small planes, the bar is a little lower than for military fighter jets, which have to handle supersonic speed, sudden temperature shifts between high altitudes and ground level, and even electromagnetic interference (EMI) from radar. That’s where the confusion starts: a plastic case that works in a Cessna might not work in a 787’s wing wiring harness, because those two environments are night and day.
I see a lot of engineers writing off plastic terminal block cases entirely because of old assumptions that plastic is too weak or too flammable for aerospace. But that’s not the plastic we work with. When I started this business, we only made ABS plastic cases for standard industrial terminal blocks. But over the years, as more manufacturers asked for parts that could survive harsh conditions, we shifted to engineering-grade thermoplastics that are made specifically for demanding environments. For example, polyetherimide (PEI) is a plastic that can withstand temperatures from -160°C to 170°C—think the cold of 40,000 feet and the heat of a nearby engine compartment. Then there’s polyether ether ketone (PEEK), which is even tougher; it resists chemical corrosion, doesn’t burn easily, and can handle the vibration that shakes a fighter jet during maneuvers. These aren’t the same plastic that’s used for toy boxes or water bottles. They’re specially formulated to meet aerospace standards.
Let’s get concrete about the testing we do in our shop to make sure these cases hold up. Last year, we had an order from a regional airline that needed terminal block cases for their new fleet’s wingtip navigation lights. Their engineer was worried because wingtips are exposed to ice, heavy vibration from wind, and deicing fluid that’s sprayed on during cold weather. We sent them samples made from a glass-filled PEI blend, and they put it through a battery of tests. First, thermal cycling: they cooled it to -55°C for 4 hours, then heated it to 125°C for another 4, repeated that 50 times. No cracks, no warping, no seal failure—we even tested that the terminal blocks inside stayed tightly in place after each cycle. Then there was the flammability test, which is non-negotiable in aerospace. We use UL 94 V-0 rated materials, which mean they self-extinguish within 10 seconds when exposed to a small flame, and don’t drip burning material. That’s a big deal because if a terminal block case catches fire, it can spread to nearby wiring, which is a safety hazard in a closed aircraft fuselage.
Vibration is another big one. Aircraft parts are constantly moving—from the rumble of the engines to the turbulence that shakes the plane. If a terminal block case isn’t secure, the wiring inside can come loose, causing a short circuit. We recently tested a PEEK case for a military contractor that needed parts for their helicopter’s cockpit wiring. We put the case on a vibration shaker that mimicked the 20 G forces the helicopter’s avionics experience during high-speed flight and landing. After 24 hours of continuous vibration, we took the case apart and checked the terminal blocks. They were still tight, no wires had moved, and the case itself had no scratches or cracks. That’s not something many off-the-shelf metal cases can handle without adding extra weight, which is a huge no in aerospace because every pound adds to fuel costs.
Speaking of weight, that’s one of the biggest advantages plastic has over metal cases in aerospace. Metal cases are heavier, which means airlines have to burn more fuel to carry them. Over the lifespan of a single 747, that extra weight can add up to millions of dollars in fuel costs, plus more carbon emissions. A plastic terminal block case is about 40% lighter than a stainless steel case, and since it’s non-corrosive, you don’t have to spend money on regular maintenance to check for rust or damage. That’s a selling point that’s hard to ignore, especially as airlines are under pressure to cut costs and meet environmental regulations. But here’s the catch: plastic cases only make sense for aerospace when they’re designed for the exact application. You can’t use a cheap, untested plastic case for a part that’s near a jet engine, because even if it meets basic standards, it might not handle the continuous high heat.
I think the biggest mistake suppliers make is treating aerospace applications like a one-size-fits-all. A lot of big companies that make plastic parts will just take a standard terminal block case, add a stamp that says “aerospace grade,” and charge three times more, but it hasn’t been tested. That’s why our customers—aircraft manufacturers, maintenance shops, wiring integrators—come to us instead. We don’t just sell a part; we work with them to tailor the plastic case to their specific needs. For example, if an engineer needs a terminal block case for a general aviation plane, we might use a glass-filled nylon that’s light, cheap, and meets all the basic standards for temperature and vibration. If they need parts for a commercial airliner’s cabin wiring, we might use a flame-retardant PEI that’s also resistant to the cleaning chemicals used on aircraft interiors. For military applications, we use PEEK, which meets strict military specs for EMI and chemical resistance.
Another thing we do that sets us apart is we test every case before it leaves our shop. We don’t just send a sample for testing; we test every production run. Last month, we had a rush order for 500 terminal block cases for a company that makes wiring for small drones used in military surveillance. Drones operate at high altitudes, where temperatures are extremely low, and they vibrate a lot during flight. We tested each case for thermal cycling, vibration, and flammability, and found that one batch had a small seal defect that would have let moisture in. We scrapped that entire batch, even though it cost us money, because we knew if that case failed, it could mean a drone crashing, which is a safety and financial disaster. That’s the kind of attention to detail that aerospace requires, and it’s something you don’t get from big suppliers that prioritize volume over quality.
Of course, plastic cases aren’t right for every aerospace application. If a terminal block is going to be in a part that’s very high stress, like the landing gear wiring, a metal case might still be the better choice. But for 70% of the terminal block applications I’ve worked on in aerospace—from cabin lighting to avionics to wing wiring—plastic cases work just as well as metal, and they’re cheaper and lighter. The key is choosing the right material, testing it properly, and designing the case to fit the exact application.
I always tell my customers that the biggest misconception about plastic in aerospace is that it’s not durable. But if you use the right material, test it under real-world conditions, and follow the industry standards, plastic terminal block cases can be even more reliable than metal. They don’t rust, they’re lighter, they self-extinguish if there’s a fire, and they can handle all the vibration and temperature extremes that aircraft face. The only time they don’t work is when someone tries to cut corners by using a cheap, untested plastic, or when they apply a standard that’s too low for the application.
For anyone who’s still on the fence about using plastic terminal block cases in aerospace, my advice is to do your homework. Ask your supplier for material data sheets that show they meet DO-160, UL 94, or the relevant military specs. Ask them if they test every batch of parts, not just samples. And ask them if they’ve worked on applications similar to yours. At the end of the day, aerospace is all about safety, reliability, and efficiency. Plastic terminal block cases can check all three boxes—if you choose the right ones.
I’ve been in this business long enough to know that there’s no such thing as a trivial part in aerospace. A terminal block that’s holding a wiring harness together might seem small, but if it fails, it can take down an entire system. That’s why we take so much care in making every plastic case and terminal block we sell. We don’t just make parts; we make parts that keep aircraft in the air, keep passengers safe, and help our customers save money.
If you’re an engineer, a maintenance manager, or a component buyer looking for terminal block cases for an aerospace application, I’d be happy to sit down with you to talk through your needs. We can send you sample cases, walk you through our testing process, and help you figure out if plastic is the right choice for your project. No pressure, no sales pitch—just real talk from someone who’s been in the industry for years and knows what works.
Don’t let outdated assumptions about plastic hold you back from getting a better, cheaper, more reliable part for your aerospace application. Reach out to us today, and let’s find the right solution for your terminal block needs.
Relay References
- Federal Aviation Administration. (2020). DO-160G: Environmental Conditions and Test Procedures for Airborne Equipment.
- Underwriters Laboratories. (2018). UL 94: Standard for Safety of Flammability of Plastic Materials for Parts in Devices and Appliances.
- Institute of Electrical and Electronics Engineers. (2019). IEEE 1789: Recommended Practice for Modelling and Measuring Electromagnetic Field Exposure From Lighting and Light Systems.
- Aerospace Industries Association. (2021). Materials Selection Guidelines for Commercial Aircraft Wiring Components.
- DuPont. (2022). Engineering Thermoplastics for Aerospace Applications: PEI, PEEK, and Glass-Filled Nylon Performance Data Sheets.
Jian Xin Technical Limited
Jian Xin Technical Limited is well-known as one of the leading plastic case and terminal block manufacturers and suppliers in China. If you’re going to buy high quality plastic case and terminal block with low price, welcome to get pricelist from our factory. Also, customized service is available.
Address: Jianxin Industry Park, Longtan Load, Yuhang District, Hangzhou, China. 311121
E-mail: marketing@jianxintechnical.com
WebSite: https://www.jianxintechnical.com/
