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What it means to ground Boeing 737 Max 8 planes

Tuesday March 12 2019

Boeing 737 MAX 8

A Southwest Boeing 737 Max 8 enroute from Tampa prepares to land at Fort Lauderdale-Hollywood International Airport on March 11, 2019 in Fort Lauderdale, Florida. US regulators have ordered Boeing to make urgent improvements to the best-selling jet. PHOTO | JOE RAEDLE | GETTY IMAGES |AFP 

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As the investigation continues into the fatal crash of a 737 Max 8 in Ethiopia on Sunday, regulators in China and Indonesia are grounding the planes, and some airlines in other countries are voluntarily pulling their fleets from service.

In the United States, the Federal Aviation Administration, which certified the latest version of Boeing’s best-selling jet as airworthy in 2017, has not taken that step despite mounting questions about the plane’s safety record.

The agency released a memo, known as a Continued Airworthiness Notification to the International Community, on Monday night that made no mention of plans to ground 737 Max planes.

Robert W. Mann, an airline industry consultant in Port Washington, New York, described what a grounding entails and the factors regulators consider when making the decision to order one. His responses have been condensed and edited for clarity.

  • What is a grounding?

A grounding occurs when the relevant safety regulator (the FAA in the United States, or the European Aviation Safety Agency in Europe) removes the airworthiness certificate for a certain kind of plane. Effectively that makes those airplanes unusable in that jurisdiction, and also in other jurisdictions that have accepted a particular regulator’s authority.


Groundings come in a variety of forms.

They can require planes be taken out of service immediately, even before a remedy has been specified, or they can come with a remedy specified.

Airplanes can also be grounded after a certain number of hours or flights, during which the airlines that operate the affected aircraft can decide when and how to inspect and repair them.

That kind of grounding happened most recently after the engine failure on Southwest Airlines Flight 1380 last spring prompted the FAA to order closer inspections of a type of engine made by CFM International.

  • What does it take for the FAA to ground a fleet of planes?

Regulators would have to conclude that there was some inherent design or manufacturing problem that was pervasive.

The worst-case example was the McDonnell Douglas DC-10 grounding after the American Airlines accident in Chicago in 1979 that killed more than 250 people.

It is the worst case from an airline’s perspective because as of the order’s effective date, the airline does not have the airplane to utilise in its fleet, so its schedule is decimated.

In the case of that accident, the concern was that there was some sort of a fatigue or maintenance procedure issue that could appear on that fleet of airplanes no matter who operated them.

  • When was the last time the FAA grounded a fleet?

The most recent fleet-wide grounding was in 2013, when the Federal Aviation Administration ordered Boeing 787s to stop flying temporarily after a problem with the plane’s battery system was identified.

That kind of grounding is pretty rare, and it should be, too. If they were happening regularly you would conclude that the review-of-design or review-of-manufacturing process was deficient.

  • What happened in the 787 case?

In close sequence, an All Nippon Airways airplane had a battery system fire, and then days later a Japanese Airlines flight arrived to Boston with an aft cargo fire indication.

The two battery fires in close sequence identified the issue that these batteries could go into thermal runaway. What Boeing engineered to isolate that problem was to first conduct an extensive analysis of the battery packs.

The FAA determined there has to be some method of isolating these batteries if you have a problem. Boeing designed a stainless steel box into which the batteries were installed, and it was vented to the atmosphere. It controlled the battery fire if there was one within the box and let it get vented outside the airplane as opposed to burning into the cabin or the cargo compartment. That fix is still flying today.

A couple of years later, an Ethiopian 787 caught fire at Heathrow, and that was attributed to the emergency locator battery. That took about 15 months to figure out. In that case, the locator beacon was banned and pulled from service.

  • How long do groundings usually last?

It varies. The issue is whether you have anything to suggest how to remedy the issue or whether there’s anything that needs to be remedied.

If it is just a question of reinforcing what needs to be done to respond to that particular event should it occur, you train for that, you test for it, and that is what you do.

But if it is something that requires a system redesign, then there is a question of whether you issue an interim order that focuses on a way to make that kind of system moot or whether there is some greater change that needs to be made.

In the case of the 737 Max, the fact that there are people that fly the airplane every day without issue suggests there is some sort of anomaly that is occurring or why it does not seem to happen here or in China where there are a hundred of them flying. It is unclear what, if anything, is the proximate cause of these particular incidents.

While airlines like Southwest and American have said they will continue to operate with their fleets of Max 8s, other carriers have halted their use as the investigation continues.