Poor visibility conditions force the pilot of a small aircraft to operate on an instrument flight plan, navigating and maintaining aircraft control on instrument readings alone. It’s OK – she’s trained for this. Suddenly, the plane crashes into an obstacle that should not have been a factor. The instruments were giving false readings, guiding the pilot directly into a target.

It sounds like something out of an action movie – a similar scene plays out in Die Hard 2 when a plane crashes after villains modified the instrument landing system. In reality, the recent discovery of a cybersecurity vulnerability in the Controller Area Network (CAN bus) that allows instruments and avionics to communicate reveals that this type of scenario is technically possible. An attacker with unsupervised physical access to a plane could compromise the data it shows the pilot or alter its flight path.

Thankfully, this vulnerability has not been exploited – it’s simply been exposed by cybersecurity researchers. The risk is serious enough that the U.S. Department of Homeland Security’s Cybersecurity and Infrastructure Security Agency (CISA) issued an informational alert in July 2019. The CAN bus raises important questions for the aerospace industry and highlights concepts central to a sound cybersecurity strategy.

CAN bus vulnerability

The CAN bus is basically a system of wires that allow instruments and avionics in modern small airplanes and helicopters to share information without a central computer. On aircraft, the CAN bus is often located in an easily accessible compartment for maintenance.

In tests conducted by cybersecurity firm Rapid7, a small device plugged into the CAN bus could alter information displayed such as altitude, airspeed, and engine readings. It could even control or disable autopilot.

A hacker would need the knowhow and a few minutes with access to the aircraft, requiring special planning and knowledge, especially since aircraft are stored in secure facilities. While it’s not something the run-of-the-mill hacker could pull off, the potential for destruction is great, and the worst-case outcome is more spectacular than hacking the automation system in a car.

So far, the only fix for the vulnerability is keeping planes under lock and key. Savvy aviators likely would be able to notice and compensate for bogus data showing up on the instruments. For instance, there is almost always an old-school, non-powered magnetic compass in the aircraft that would be unaffected by hacking of CAN bus-connected avionics. Many pilots also fly with extra navigation equipment that isn’t networked into the aircraft, such as an iPad running Foreflight.

While flying under instrument conditions, a properly trained pilot would likely notice the discrepancy between the in-aircraft avionics and the non-networked, supplemental systems. There are, however, times during an instrument flight where the margin for error is very small, especially while on precision instrument approach into an airport with low visibility.

Cybersecurity oversight

Aside from finance, aerospace manufacturing is now the most cybersecure industry in the U.S. NIST 800-171’s strict and sweeping cybersecurity guidelines took effect Dec. 31, 2017. The guidelines apply to any manufacturer handling controlled unclassified information (CUI) anywhere in the federal government supply chain. NIST 800-171 covers more than a dozen criteria on how to configure networks, how to store and track data, and how employees receive access.

Though the deadline has long passed, many smaller manufacturers are still getting up to speed, spurred by compliance requirements from larger companies they supply. Plus, the guidelines are so complex and thorough, it takes months to achieve compliance.

With increased focus on aerospace manufacturers protecting their environments and data, the CAN bus vulnerability is a reminder to keep cybersecurity top of mind when designing software and networked systems. Engineers must put themselves in hackers shoes and imagine how a given system could be exploited, now and hypothetically in the future. With new Internet-of-Things (IoT) exploits coming to light regularly, it’s easy to see the dangers of designing an open CAN bus system – which dates to the 1980s – even when no immediate threat is apparent. The best outcomes are achieved when security is part of the design spec, not an afterthought.

Physical cybersecurity

The CAN bus vulnerability illustrates a concept that data must be physically and electronically secured. A manufacturing facility’s physical security is covered in the NIST 800-171 cybersecurity guidelines. The flip side of this is that the physical security of aircraft, airports, and hangars is the only thing keeping the CAN bus vulnerability from being exploited. We would not be having this discussion if the CAN bus had a robust authentication mechanism that would only communicate with good devices.

Effective cybersecurity strategies have multiple layers. Physical security is often ignored as some companies fail to secure server closets or monitor facility access. Although the aerospace industry does this quite well, any cybersecurity system with a single layer is bound to fail eventually. Higher security environments restrict physical access to their network and logically control which devices can connect to it.

In the long term, manufacturers of instruments and avionics connected to the CAN bus will likely need to add security features that limit how components interact. The challenge is going to be finding a way to make this change before a catastrophic cyberattack. Since the CAN bus vulnerability was announced in July, there hasn’t been much talk of designing components to compensate for it. The notion seems to be that planes are stored securely, alerts have been issued to pilots, and everything should be fine. I hope that’s the case. When it comes to cybersecurity, hoping for the best is often a way to get the worst.

Kelser Corp.

About the author: Jonathan Stone is an instrument- rated commercial helicopter pilot and CTO of Kelser Corp., a Connecticut-based IT consulting firm. He can be reached at jstone@kelsercorp.com

Photos courtesy of Bumax

Potentially disastrous effects could result from galled fasteners seizing or experiencing fatigue breakage, so aircraft manufacturers must counter this threat. Not everyone in manufacturing is familiar with galling, except for those who absolutely must know: designers and engineers. With galling a serious threat to the quality and safety of expensive and crucial equipment, staff in executive management, operations and procurement would be wise to study this phenomenon also.

In galling, excessive friction between two moving metal surfaces causes mechanical wear, tearing up material and transferring it between the surfaces when load compresses the surfaces together.

Fasteners prone to galling

Standard stainless-steel bolts and fasteners tend to gall under certain conditions. Thread galling can occur with standard fasteners when pressure and friction cause the bolt threads to seize to the threads of a nut or a tapped hole. Severe galling, known as cold welding, can cause the two surfaces to fuse together, making the joint impossible to remove without cutting the bolt or splitting the nut.

Galling’s consequences should not be underestimated. A galled fastener may fail to achieve the necessary pre-load – especially in dynamic loading. This jeopardizes the fastener’s task to securely fasten two surfaces together, which is complicated by the fact that an application may involve hundreds or even thousands of stainless-steel fasteners.

If critical fasteners in the rotating parts of a chemical pump, rotor blade, or propeller gall, the joint is likely to experience fatigue breakage, requiring costly maintenance and downtime for the customer. At worst, fatigue breakage of critical fasteners might result in accident or injury. Galled fasteners are also much more susceptible to corrosion, which can ultimately result in breakages.

Five galling prevention steps

Select the correct material

Certain types of stainless steel are more prone to galling due to their atomic structure. Cold-formed, strain-hardened stainless steels provide excellent galling resistance due to improved strength and reduced ductility.

Choose fasteners with a perfect fit

A tight fastener fit reduces galling risk by minimizing movement and friction. High-quality threads have fewer surface deviations that can rub together and lead to galling.

Add lubrication

Lubrication allows materials to slide past each other without causing friction. Some leading premium fastener manufacturers use custom-made wax to ensure an optimal friction coefficient. Anti-seizing and anti-galling lubricants can also help reduce galling.

Avoid damaged fasteners

A bolt with dented or damaged threads has a significantly increased chance of galling. Check all fasteners for damage that may have occurred during shipping. Dirty bolts with debris in the threads can also greatly increase the risk of galling – so only use clean bolts.

Install carefully

Most stainless-steel is sensitive to high temperatures, so tightening bolts slowly can reduce friction and heat that can cause galling. Avoid power tools that can cause excessive friction and heat. Calculate each application to determine tools that can be used.

Catastrophic failure risk

In the aircraft industry, catastrophic failures can occur if the thread galls before enough torque has been obtained. However, galling can be overcome even in the most challenging of applications – particularly by selecting premium quality stainless-steel fasteners.

A fastener such as the Bumax 88 has a high molybdenum content to make joints extra strong, reliable, and corrosion resistant.

Premium fasteners may look similar to standard stainless-steel fasteners, but superior material properties can make all the difference with galling. Explain to your fastener supplier exactly how the fasteners will be used to ensure optimized galling resistance. Premium stainless-steel fasteners also typically offer other properties that are essential in many critical fastener applications – including corrosion resistance and high tensile strength.

Bumax

About the authors: Patrik Lundström Törnquist is managing director of Bumax, and Anders So¨derman is the company’s technical director. They can be reached at anders.soderman@ bufab.com and patrik.tornquist@bufab.com.

All photos courtesy of Buehler

Printed circuit boards (PCBs) need to operate reliably in harsh aerospace environments withstanding extreme temperatures, humidity, vibration, and in some cases, solar radiation.

Therefore, the manufacturing process must be accurate and reliable, providing an industry standard 15-to-20-years of failure-free operation for electronics.

Ensuring reliability in PCBs starts with their fabrication and design, following every step of the way with rigorous quality control procedures.

PCB manufacturing

A PCB provides the basic building block of an electronic device. They consist of alternating layers of material to provide an insulating overlay and conductive paths. Board manufacturers can make cheaper PCBs of less durable materials, but higher-quality boards are mostly comprised of fiberglass, such as FR4. Producers manufacture multiple layers of the board sequentially. The processing can be expensive and adds value to the components. Finding a problem in production late in the process is not preferable, so quality control checks must be done quickly and efficiently at crucial stages. Test coupons and the part are typically manufactured within the PCB to achieve this reliability.

Documentation

Test coupons allow manufacturers to analyze PCBs in the quality assurance lab. The coupon is subject to the same manufacturing processes and sequences as the PCB and can be evaluated for the specific characteristics present on the entire board before the manufacturer mounts other components. With the same qualities and flaws as the PCB, the coupon will show any quality problems.

Even without the components that are eventually mounted on it, a circuit board is an intricate part. The board usually contains a filler, such as silica. It also can consist of aluminum, which manufacturers use as a dielectric for high-frequency boards.

Some manufacturers design test coupons that easily press-out from the board, ensuring removal without damaging the overall board. Where this is not done, they must be removed using an appropriate cutting tool, a critical step given the board’s brittle material.

Coupons can check bare board quality, issues such as etch definition, layer registration, plating quality, or solder mask definition. They can also monitor the assembly processes for surface mount technologies (SMT) and conventional plated through-hole (PTH) assembly types – cut and clinch quality, paste printing quality, insertion accuracy, reflow/flow soldering quality and assembly cleanliness.

Manufacturing the coupon at the same time as the main PCB gives both the same impedance, which depends upon the PCB’s dimensions and electrical properties.

Primary board inspection concerns are the copper plating thickness and the width of the component mounting through-holes. A scanning electron microscope (SEM) examines the holes to determine if they meet specification. If the holes are too wide, the lab rejects the board.

Copper plating can be contaminated during board coating. Also, the boards must be tested for the surface coating’s integrity. If encapsulation is insufficient, the board oxidizes, shortening the component’s lifetime. IPC-222 standards define test coupon design requirements, and IPC-601 standards identify the minimum and maximum dimensions for all internal and external features, including laminate layers, plating, foils, holes, and spaces.

Maintaining coupon integrity

Crucial to inspection, the lab needs to remove the coupons from the PCBs without damaging the coupon’s structure. The piece must be cut to a specific size while preventing the board from cracking. With the brittle materials contained in many boards, this can be challenging.

Some labs use hand saws, which can be imprecise and can damage the coupon or the board. Cutting these coupons is not merely lopping them off the PCB. There are many inspection areas and cutting damage can make a quality inspection impossible.

Also, there must be some margin between the edge of the board and where the copper coating begins. Finally, cutting must not splinter the edge of the board to avoid secondary damage.

Abrasive and precision cutting machines and sectioning saws can support metallography testing. Specimen preparation for microstructural examination of PCBs starts with a quality cut. Selecting the proper sectioning blades and precision cutting saws saves time by limiting the number of steps needed to analyze coupon samples.

Proper coupon sectioning technique depends on the boards’ thickness, size, and silica composition. Based on the board’s hardness, the technician can select a cutting blade with a low concentration of diamond cutting points that reduce damage for hard, brittle materials.

Recent developments in precision sectioning saws are improving the precision and efficiency for cutting coupons and can provide the versatility needed for various PCBs.

To achievie efficiency, semi-automated sectioning saw controls easily position samples to minimize setup time and can accommodate various coupon sizes. The controls enable quick cutting-parameter setup. Protective or smart-cut functions limit cutting loads on precision saws, ensuring consistent quality.

Precision is crucial. Accurate positioning, higher reproducibility, and minimal sample deformation are required for delicate PCBs. For further precision, advanced units can fine-tune adjustments after clamping.

Automated serial cutting – the ability to cut parallel lines accurately without re-clamping – adds efficiency, reducing operator variability and ensuring high-quality coupons. Using specialized precision cutters, the lab technician can cut 10-to-20 samples per hour with minimal deformation. With the high volume of boards coming off the plant floor into the quality assurance labs, these systems let facilities handle a greater number of samples to keep the line moving.

Through-hole inspection

Inspecting PCB test coupon plated through-holes or via’s requires metallographic preparation of the sample, a process that requires mounting the coupon in plastic to protect the sample, then grinding and polishing to the center of the feature of interest.

Due to the continued miniaturization of electronics, these features can be extremely small – yet targeting the center is crucial for accurate quality control checks. In high-volume laboratories, where speed and quality are equally essential, this can be achieved using test coupons with specific dimensions.

The coupons can be held in a precision target grinding fixture that uses reference pins to hold the coupons in position. Diamond stops in the fixture then allow grinding to the features of interest, with an accuracy up to 0.004" (0.102mm).

Quality assurance

For quality assurance labs handling a wide range of samples, precision saws can section a wide range of materials from PCBs to rubber, nickel superalloys, and carbon fiber. Saw manufacturers can guide you as to which cutting blades match the kinds of boards or other material you are inspecting.

The quality lab’s ability to keep up with inspections should not slow things down. Nor should rushing this process compromise quality control or threaten the reliability of the aircraft using the PCBs.

Buehler

About the author: Nanu Vishora is a materials engineer at Buehler, an Illinois Tool Works (ITW) company. He can be reached at info@buehler.com.

The aerospace and defense (A&D) market demands product development efficiency, quality, technological innovation, and regulatory compliance. Many A&D products are subject to export regulations, including International Traffic in Arms Regulations (ITAR) and Export Administration Regulations (EAR), requiring compliance in technical data handling and access.

Regulations stipulate that any technical data deemed controlled by ITAR or EAR must not be exported during design, production, or sustaining activities unless covered under an export license.1

In practical terms:

• ITAR-, EAR-regulated data must remain in the U.S.; be accessible only to U.S. persons
• In-transit, at-rest data must be encrypted
• Platforms containing regulated product data must control and restrict access to only U.S. persons

These regulations ensure companies have tight control over all regulated technical data, including controlled unclassified information (CUI). The registered manufacturer defines what technical data in the product record is under export control based on the product, how the government classifies the product, and what product features are of interest to the U.S. government. Technical data can include file names, component descriptions, engineering drawings, specifications, test procedures, and bills of materials. All restricted data must be tightly controlled by standard policies and procedures for access, audit history, and incident reporting.

Regulations refer to any method of access: operating systems, applications, IT assistance, and/or system maintenance where restricted data is stored. All information sharing methods require control, including email, faxes, and physical deliveries.

Complex products, development

Increasing complexity – mechanical products becoming electro-mechanical, electro-mechanical products embedding software and Internet of Things (IoT), artificial intelligence (AI), and machine learning – makes regulatory compliance more difficult.

Of the top 10 business threats to the A&D industry identified by Ernst & Young 2, four relate directly to product complexity in compliance, strategy, and operations – creating supply chain management burdens, innovation challenges, quality and time-to-market stresses, and overall performance stresses. A&D companies must prioritize product data control, transparency, and availability to overcome these challenges.

Digitizing the complete product record can advance intelligence, improve manufacturing, and increase quality. However, companies won’t experience those benefits until they control the product record in one digital form. This digital copy allows all design, release, and service activities to flow from the same view across all products.

Managing export-controlled data

Legacy business software solutions, developed before modern security advancements, don’t support complex product work needed for efficiency, speed, and quality. Homegrown desktop apps, spreadsheets, and local file servers can suffice for a time, but none enable scaling business, optimizing processes, or exceeding quality and market goals. Most of them can’t adequately address the security and location-based restrictions federal regulators demand without cost and additional risk.

ITAR and EAR regulations impact every tool and method of storing and accessing controlled technical data:

• Physical and logical layers, hardware, operating systems, networks, protocols
• Platforms, applications
• Product data structures
• Data classification
• End-user controls
• Access management

Regulations stipulate specific requirements, and the responsible owner for each layer must ensure requirements are met, including policies and procedures, incident reporting, and maintenance activities.

De-mystifying ITAR, EAR

Management should confer with compliance officers and legal counsel to determine:

• Does product require registration for ITAR, EAR, both
• What in the product data is under export control
• Which requirements, beyond specific regulations, must also be met
• Determine how the requirement is being met and who is responsible for that requirement

Security controls have the highest priority when adopting or changing product lifecycle management (PLM) systems or digitizing complete product records. Modern systems allow regulatory compliance and improve business operations by offering collaboration functions.

Technologies and practices have progressed to the point that U.S. government agencies use various secure cloud tools for everyday business such as Cloud First, Cloud Smart, and GovCloud initiatives.3 Regulatory bodies have recognized this technological maturity, updating regulations to account for more collaborative cloud options.

Arena Solutions