Leeham News and Analysis
There's more to real news than a news release.
Bjorn’s Corner: Faster aircraft development. Part 27. Where Speed-Up gets Tough.
By Bjorn Fehrm and Henry Tam.
February 13, 2026, ©. Leeham News: We are summarizing how modern tools, processes, and AI can help reduce the time required to develop a clean-sheet 200-seat replacement for the Airbus A321neo and the Boeing 737 MAX 10.
We discussed some ideas in the last article on how current AI can support development. We could see it helping reduce the time spent on templating documents and on designing and verifying simple parts, such as mounting brackets for pipes and cables.
To address the more challenging parts where AI struggles to assist, we need to understand why development programs now take longer than in the past and what can be done to shorten the timeline.
Here are examples of challenges that meet today’s Part 25 aircraft development projects:
Use of Advanced Material
Many programs today are using new composite materials to reduce weight. On the one hand, these materials typically have better properties than traditional materials, and costs would come down once the tooling is paid off. On the other hand, certifying new materials is often not as simple as expected. It often takes years to characterize these materials and manufacturing processes.
Composite materials qualification typically involves thousands of test articles to statistically characterize the material. A range of tests, from small test coupons to full assembly, is required. The processes used to produce these parts must also be controlled and documented in the materials qualification dataset.
The National Center for Advanced Materials Performance (NCAMP) maintains a pre-qualified materials list to reduce the number of tests required. OEMs that choose to use these material specifications must adhere to the design constraints and manufacturing processes when developing parts from these materials. If OEMs deviate from the material specifications, additional tests are required.
We shall compare this to designing yet another aluminium airliner, like when Boeing went from the 727 and 737 to the 757/767. Essentially, the same material system was used for the different parts, sometimes with modest updates. But it wasn’t as drastic a change as going from Aluminium Alloys to Carbon Composites for a part of the aircraft. The bottom line is that an aluminium structure is faster and cheaper to develop and produce, though it is less beneficial in terms of weight and maintenance costs.
Widespread Use of Advanced Electronics
Modern aircraft have numerous onboard smart electronic systems. The traditional pitot-static system has been replaced by smart probes. The avionics system is now the aircraft’s brain, with access to every system. Flight controls on new airliners are all fly-by-wire.
There is a cost to using these advanced electronics, especially in safety-critical systems. Software for these systems must follow the processes outlined in DO-178, Software Considerations in Airborne Systems and Equipment Certification. This is not a black-box test that a developer can do at the end of the development. The design must be fully traceable.
Safety-critical software has even more stringent requirements, such as Object Code Verification. This requires traceability from source code to machine-understood low-level code. If traceability cannot be demonstrated directly, additional verification is required.
As with software systems, complex electronics also need to be qualified under DO-254, Design Assurance Guidance for Airborne Electronic Hardware. The guidance applies to a wide range of components, including circuit board assemblies and integrated circuits. The design must undergo a rigorous validation and verification process. Again, a black-box test at the end of development is not acceptable, especially for safety-critical systems.
From this, we can see that a major change in an advanced electronic system could have a significant impact on work time due to verification and validation. Regression tests often consume a non-trivial amount of time.
Electric Wiring Interconnection System (EWIS)
Wiring has also gotten more complicated over time. Part of the complexity stems from the widespread use of advanced electronics. More wires are needed to connect components to the “brain”. This also leads to more complex failure analyses. Can a rotor burst, a tire burst, a local fire, etc., damage wiring in a way that the aircraft cannot achieve a safe flight to landing?
A safety engineer can work with their systems and structures counterparts to physically separate redundant systems. However, this strategy does not work if a rotor burst could sever all the wires to these redundant systems.
Another part of the complexity comes from lessons learned. Some regulations grew out of an aircraft explosion thought to have been caused by wire shorts igniting fuel tank vapour, and damage to the aircraft caused by wiring faults (sometimes originating in non-essential systems).
One common yet critical challenge with EWIS on a development program is that the team often receives numerous late changes for various reasons, even though they must deliver parts early so wiring bundles can be buried deep inside the airframe.
Regulatory Interaction and Oversight
Highly advanced/integrated systems and novel materials often lack established methods for demonstrating compliance with applicable regulations. To establish the means of compliance (MOC), the OEM and the regulator often engage in extensive back-and-forth communication to discuss the technology and its features, develop an MOC, and document the agreement through Issue Papers.
These coordination activities with the authorities often take months to close. It is also not unusual to have multiple sets of MOC Issue Papers for a development program.
When the regulator determines that current rules do not adequately address a new technology, the OEM and the authorities often engage in a multi-year process to develop Special Conditions to address the gaps. Unlike Issue Papers, Special Conditions establish regulatory requirements.
As a result, Special Conditions are subject to public comment, which may lead to a lengthy closure period. For example, the Notice of Proposed Special Conditions for magniX’s electric engines was released in November 2020 (https://www.federalregister.gov/documents/2020/11/19/2020-23434/special-conditions-magnix-usa-inc-magni250-and-magni500-model-engines).
The Final Special Conditions were released in September 2021 (https://www.federalregister.gov/documents/2021/09/27/2021-19926/special-conditions-magnix-usa-inc-magni350-and-magni650-model-engines-electric-engine-airworthiness). This is almost a year of waiting for the requirements to which the motor shall be developed.
Interagency coordination is another challenge. When validating a type design with foreign authorities, the foreign authorities may deem the agreed Means Of Compliance (MOC) inadequate. If this is addressed early on, it may not be a big deal. However, if this is done after certification, it could require costly changes to obtain the desired foreign validation.
Summary
The above lists reasons why the typical development time for a new airliner in the A320/A321 and 737 class now takes two years longer than for 40 years ago when the A320 was developed. We will summarize the impact of modern integrated tool support, such as the Digital Twin, Agile methodologies, and AI, next week.
For composites you have different deformations as it leaved the form tools after autoclave baking. For softer aluminium it is not as critical and you can allow more deformation at assembly before shimming. Just look at the A380 wing where they forced composite/metal parts together at assembly and hence got to high forces in the joint due to forcing stiff composite parts to mate during riveting, then some years later had to redo it with new parts (panels and ribfeet)
Was that the design or the wrong install process?
I remember every one made up to finding the issue and getting the final fix in had to be redone. Talk about costing big bucks.
Airlines could pay the hit then (lost flights) or latter but no getting out of it one way or the other.
A bit of both, the UK wing structure designers should have anticipated the deformations and the rivet axial forces due to forcing parts together. Assembly should be better shimmed up to allowable gaps, this to limit the axial rivet forces and with it rib feet forces. Then as reject numbers should have bloomed the present design changes or better (that can handle long term parking) should have been made.
Interesting info on EWIS here, among other things. Thanks.
It is slightly surprising that wiring becomes more complex, when the electronics to handle high speed buses have become vanishingly cheap.
This should greatly simplify the wiring harness and make it so small that it can easily be protected or armored, quite apart from having redundant buses widely separated.
Good one to get an explanation on.
When I started, Processors for controls were for big systems only, you could only get it into a room. Anything outside the room was wire intensive. Mostly not doable.
Eventfully the rooms that had whats called Terminal Box (air damper for cooling and or heating coils). All we had to do was run a wire from the temp sensor on the wall to the box and daisy chain in a com line. Power use was so low you could daisy chain in 20 of those terminal boxes off on Xformer.
In that case it allowed remote monitoring of what the box was doing, room temperature, programing changes if needed or troubleshooting to see what was not working. Beyond cost prohibitive to do with wires.
It was almost like being Omnipotent over entire facility and remote buildings. Bandwidth was low, you could link in remote with a modem. Literally FBW when it was that or nothing.
“when the electronics to handle high speed buses have become vanishingly cheap”
Cheap is not reliable.
fault scenario for wires (still) is much more benign than complex electronic components. Wires and “boxes” fail “per item” while loss of function has more reach for “boxes”.
Redundancy beyond other (beneficial) effects increases the number of parts that can fail. ( Quad vs Twin retold in a way. )
Both Boeing and Airbus have been utilizing fiber optic cables in design. Primarily for weight savings and reliability. The 787 utilizes extensive fiber optics. In the early years one drawback was if a FO cable did get damaged or cut, it required replacing the whole run. Boeing has since developed an approved repair splice scheme.
Some advantages include:
Immunity to Interference: Since fiber uses light rather than electricity, it is immune to electromagnetic interference (EMI) and radio-frequency interference (RFI), allowing it to be installed near high energy equipment without issues.
Physical Durability & Size: Fiber optic cables are thinner, lighter, and more resistant to pull pressure than copper, making them easier to install in tight spaces.
Security & Reliability: It is much harder to tap into fiber optic cables, making them more secure. They are also non-corrosive, enhancing their long-term reliability and lifespan (30-50 years).
Safety: Because fiber does not carry electric current, it does not pose a fire hazard, unlike older or damaged aluminum cabling.
Also:
– Lack of crosstalk.
– Much higher bandwidth.
– Less signal degradation per unit length.
Not just the 787:
“The Airbus A350 uses optical fiber for high-speed data transmission, specifically in its in-flight entertainment (IFE) systems, avionics, and for advanced structural health monitoring. It utilizes fiber optic gyroscopes for flight controls, improved sensors for engine pylon overheating detection, and offers high-bandwidth, low-latency communication. “
“Safety: Because fiber does not carry electric current, it does not pose a fire hazard, unlike older or damaged aluminum cabling.”
you still need to supply power to those “safer” devices.
data lines like ethernet or signal lines are usually too low power to be seen as a hazard. ( I’ve handled EX requirements for mining equipment ). Now things like POE are a different animal.
Hi RobertPhoenix,
Excellent question. I think there are a few challenges though.
First, even advanced microelectronics can fail. So, redundancy is likely required to meet certain level of reliability.
Second, armour may protect against events like rotor burst. We still need to protect systems/wirings from other events such as fire, shorts, etc.
Third, imagine there is only one main data bus. It will need many “network switches” (or some sort of mux/demux) throughout the aircraft to connect to all the controllers, sensors, and actuators. Each of these switches can fail. When one fails, downstream devices are affected. So, redundancy may be required and we are back to having more boxes and wires.
At least in my world the controllers were stand alone. Loose the buss and they ran on their internal program.
Vast majority did anyway, central control only had a few programs it invoked into the controllers for specific conditions. Default the controlled entity just stayed in its mode. A lot of it could be programed to a fail safe condition.
We used some free air cooling, ergo, as long as using the Refrigerant Compressors, they would run. So loss of com was a shift to or remain in Reefer mode.
The one that was a dilemma was shared information and that boiled down to Outside Air Temperature that affect all the large fans. I used a lot of dedicated OA sensors at the units to ensure that did not bust the most critical fans.
Aircraft of course are literally a bunch of flying systems working together so it all has to be shared. My mind boggles at how you program such a creature.
Wiring while complex also was not computers. A lot of my stuff was simply told to turn on or off (or shift) and the OEM processor did all the ops. Rudder control does not work that way of course. Input in, move rudder, report rudder movement and so on.