After 2 serious 737 Max engine incidents at Southwest, Boeing alerts pilots

Last year, two Southwest Airlines 737 Max jets lost engines on takeoff after striking large birds, emergencies made much more serious when smoke and fumes penetrated inside the airplanes.

Flight crews on both aircraft — one taking off from Havana, Cuba, the other from New Orleans — followed procedures and made emergency landings back at the airports.

Recognizing an abnormally high risk in these two unusual incidents, Boeing sent an alert to airlines in February to make sure pilots know the correct procedure in such an emergency to quickly stop the penetration of smoke and fumes.

In response, United conducted “a thorough review of training and existing procedural guidance for our pilots.” Southwest and American — the other U.S. airlines operating the Max — sent notices to their pilots detailing what had happened and explicitly flagging the right procedure to use.

The goal was to minimize the risk of catastrophe in the future if pilots facing a similar incident didn’t handle it as well as the two Southwest crews did. Yet a detail in Boeing’s alert — mention of a system on the Max’s LEAP engine the pilots hadn’t known about — caused concern among some pilots.

That system, a fail-safe feature developed by engine maker CFM International, worked as designed to constrain even worse damage to and a potential breakup of the engine.

But pilots want to know more about the system, which is not in their manuals, and how exactly it performed in these two incidents.

Southwest’s notice said it intends to update its flight manual for the Max with information about the system. But that hasn’t been issued yet.

“We haven’t been told a lot,” said Tom Nekouei, vice president of the Southwest Airlines Pilots Union, or SWAPA. “We’re still kind of in limbo.”

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AN ENGINE SYSTEM THAT’S NEWS TO THE PILOTS

The pilot manual and training lay out the conditions that tell a pilot when to use the procedure for engine fire or severe damage. One of those is heavy vibrations accompanied by abnormal engine warnings on the instrument panel.

This is where a new system on the Max’s engine is relevant. It’s called a load reduction device, or LRD.

The major change to the 737 design with the Max was a new engine called the LEAP, made by CFM International, a 50/50 joint venture between GE and French company Safran and the exclusive engine provider for the 737 since the 1980s.

The LEAP is also the most popular of two engine choices on the rival Airbus A320 jet family.

Replacing the earlier engine that powers the prior 737 NG model, the LEAP has a much bigger fan to add fuel efficiency. CFM added the LRD technology as another upgrade and it’s on both the Airbus and Boeing versions of the LEAP.

If an engine fan is badly damaged in flight, say by a bird strike, broken fan blades will throw the rotating parts off balance.

That will cause the whole intricate mechanism to shake and heavy vibrations can lead to further damage.

When this happens, the new LRD safety feature activates and disconnects the fan blades from the rotor turning the fan. The fan blades then spin freely.

CFM said this allows the fan to decelerate rapidly “to minimize disturbance to the rest of the engine and its connections to the aircraft.”

Since airline mechanics must maintain the Max engines on a daily basis, the LRD is duly described in the airline maintenance manuals.

An entry in the maintenance manual describes the LRD’s purpose — “to protect the aircraft in case of heavy vibration” — and how it works.

But airline pilots were not similarly informed.

Boeing in a statement explained that the LRD does “not affect airplane handling, the crew cannot affect their operation, and no crew procedures change as a result of LRD activation.”

That’s the rationale for not putting the LRD in the Max pilot manual. It activates automatically when severe damage occurs. It doesn’t affect what the pilots do and they have no control over it.

Federal Aviation Administration spokesperson Jillian Angeline said “the pilot training for engine failures has not changed and does not specifically address the Load Reduction Device mechanism or functionality.”

Yet some pilots at Southwest and American were startled and unhappy to learn of this for the first time.

“If I have a system in the airplane that has a function, I need to know about it,” said SWAPA vice president Nekouei.

It’s also unclear why Boeing’s service bulletin and the airline notices to pilots mention the LRD. Since the crew cannot control it, what is its relevance to them? Did it have some role in these emergencies?

When the LRD works as it should to reduce vibration and further engine damage, could that mask the severity of the damage to the engine and lead pilots to use the wrong recovery checklist?

Boeing declined to comment. The FAA’s Angeline said there’s “no evidence” that the pilots in the Southwest incidents “were misled by engine symptoms in any way.”

A confidential hotline complaint — which The Seattle Times reviewed —submitted to the FAA under the whistleblower protection system by a Southwest pilot likens the withholding of information about the LRD to Boeing’s hiding of the Maneuvering Characteristics Augmentation System, or MCAS, that was a prime cause of the two fatal Max crashes five years ago.

Yet while MCAS was a badly flawed design, there’s no indication the LRD is defective.

The birds that struck the two Southwest engines “significantly exceed the size and weight” of those used in required certification tests, and yet “the engines performed as designed during these events,” said CFM spokesperson Nathan Hicks.

And although the LRD is new to the 737 on the Max model, CFM says the system is also on the 787 Dreamliner and 777 engines, both made by GE.

Still, American Airlines captain and APA spokesperson Tajer is unhappy.

“While this engine safety system appears to have a necessary function, we continue to seek information,” he said.