In the latest round of problems for the Boeing 737MAX, the FAA is taking a serious look into aircraft wiring. The issue is wiring bundles in the tail of the aircraft that could chafe causing incomplete or short circuits. Incomplete circuits could cause a loss of directional control of the aircraft. Short circuits can overheat and start an aircraft fire. I first reported on the problem in this post from January 6, 2020.
The Problem
All aircraft have miles of electrical wiring running the length and width of the aircraft. These wires service aircraft controls, mechanical functions, HVAC, passenger services and more. The current version of the 737 has about 42 miles of wire in the airframe. Wires that go to common destinations in the aircraft are loomed together into wire bundles. It is a wire bundle in the tail section of the 737MAX that is at risk. Wire bundles must be constructed and installed in a way that there is no movement of the wire so that it becomes either loose or chafed. Chafing is caused by wire movement against the airframe which causes the insulation to wear out. Loss of insulation can lead to short or incomplete circuits as noted by the First Defense Insulation company. The critical nature of this wire bundle handles the control or the rudder (yaw) which is the left and right steering of the aircraft. The control over the elevators (pitch) the up and down control movement is also affected.
737MAX Certification Issues
The 737MAX is currently grounded while awaiting FAA approval of the MCAS system which was responsible for two fatal air crashes. The FAA is taking a position of increased scrutiny and has identified the wire bundle issue as not meeting certification standards. This is what the FAA is saying:
“The manufacturer must demonstrate compliance with all certification standards. The aircraft will be cleared for return to passenger service only after the FAA is satisfied that all safety-related issues are addressed.”
Boeing responded by saying:
“We remain in ongoing discussions with the FAA on the wire bundles. Regardless of the final determination on this matter our estimate for a mid year return to service of the MAX is unchanged.”
Not only would Boeing have to modify the wire bundles in aircraft under construction, but they would also have to modify the more than 400 737MAX aircraft that have already been built.
What Boeing Needs To Do
The fix for the wiring bundle problem is not that complicated. They can create modified wire bundles on the factory floor. Then they would remove the existing wire bundle and replace it with the new wire bundle using approved construction methods. It is estimated that Boeing could swap the wire bundle in about two hours per aircraft. Boeing can’t afford another 737 crash regardless of cause. They need to stop talking and fix the problem.
Boeing says that if they have to replace the wire bundles, it won’t further delay the 737MAX reentry into service.
What The FAA Needs To Do
The FAA is already under the microscope in Congress as to their relationships with aircraft manufacturers. The FAA has long let aircraft manufacturers to self-inspect their construction methods and certification inspections. One of the reasons for this is that the FAA can’t pay qualified engineers enough money to work for the FAA. These engineers can make much more money working in private enterprises.
Congress is currently looking into new “oversight” requirements for the FAA. The mission of the FAA is to promote aviation and to ensure safety in aviation. There are times when these objectives are directly opposed to each other. This is a circumstance when promoting aviation (Boeing 737MAX) and enforcing safety standards are at odds with each other.
The FAA should mandate that Boeing fix the wire bundle problem before recertification of the 737MAX is granted. It looks like this is just what the FAA is going to do.
Final Thoughts
When you look at all of the problems at Boeing, one thing is consistent – a problem with the safety culture. Boeing needs to focus on safety instead of cost and deadlines. The FAA needs to take the driver seat in aircraft safety certification issues and not let it run on autopilot.
The wiring bundle issue needs to be resolved by Boeing before the FAA should grant certification for the 737MAX. The fix is relatively simple and won’t cost a lot to repair.
