“U.S. air-safety regulators have launched an audit into how a Boeing Co. BA -1.32% factory tweak led to a safety problem with some of the plane maker’s 737 MAX aircraft, two years after a pair of fatal crashes prompted other fixes to the jet.
The Federal Aviation Administration on Thursday said it is investigating why Boeing missed that a minor production change involving drilled holes wound up as the root of potential electrical problems. The audit is expected to delve into issues beyond those addressed by a typical agency review of such problems … The FAA will examine ‘Boeing’s process for making minor design changes across its product line, with the goal of identifying areas where the company can improve,’ the agency said after The Wall Street Journal reported the audit …..
After Boeing identified the electrical issue, engineers determined it affected a standby power supply unit and a rack located behind the first officer’s seat, as well as the cockpit’s main instrument panel, according to the FAA. One potential side effect, people familiar with the matter said, could result in flight crews being unaware that the plane’s anti-icing systems aren’t working. Ice buildup can cause engine flameouts, or temporary shutdowns.”Link to:
The Wall Street Journal - April 30, 2021Personal comment: That last sentence is grossly incomplete. The greater danger with up ice buildup is that a plane becomes overweight and can’t fly due to excessive weight
and loss of lift on the leading edges of the wings and other lift devices. It literally falls out of the sky. Particularly hazardous at low altitudes and slower speeds (as when preparing to land). Knowing the anti-ice devices aren’t working is essential - as there are things a flight crew could do to land the plane safely in this event - if they had the information.
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The other info also suggested that as Boeing has been chasing down this production issue they have found the same situation in a number of other areas on the 737 Max, both in some aircraft which have already been delivered to customers, and in aircraft which are still in the possession of Boeing. Boeing likely has a good idea exactly which aircraft are involved, as their records should show when the production method was changed.
The fix is pretty straightforward, usually involving the addition of a grounding cable from the equipment to the airframe. A worrisome thing, it seems to me, is the rather vague information suggesting that "equipment in other areas of the plane" have also been found to have this problem. Let's hope that they manage to find them all.
At least Boeing found this issue themselves, and brought it to the attention of safety regulators.
Additional comment: A close read regarding the aircraft de-icing systems seems to suggest that the equipment grounding issue doesn't actually affect the de-icing system itself, but rather impairs notification to the pilots if the de-icing system does fail to operate. While obviously the lack of de-icing monitoring is not a good thing, at least it's not as critical as impairment of the de-icing system itself.
There has been mention of holes drilled in articles about the electrical issue. That leads me to wonder if abrasion of the electrical wires’ insulation caused by the nature / location/ or size of those holes was a possibility. Should the insulation wear off it could cause either a short circuit or possibly loss of electrical current should the wire be damaged enough. Small issues like that can bring down an airliner. No excuse for it really.
We occasionally saw similar problems in our shop with the installation of radio communications gear. Good grounding is critical to the dependable operation of electronics equipment.
PS - A well grounded answer.