FAA issues Airworthiness Directive for Boeing 737 Max following Lion Air Crash | Malfunctioning sensors now treated more seriously

[AlTech]

Bloomberg and The Verge report that the Federal Aviation Administration has issued an Airworthiness Directive for the Boeing 737 Max following the Lion Air Crash.

 

This also follows Boeing's own safety bulletin although the American regulators required that carriers add information about how to diagnose malfunctioning sensors to pilot manuals.

 

Boeing's safety bulletin explained that the Angle of Attack Sensor (AOA), used to determine the attitude/pitch of the plane, could in some cases provide false readings. Boeing and the FAA have stressed that malfunctioning sensors are something to be taken very seriously and an NTSB Official believes it could have contributed to the crash.

 

Quote

Boeing cautioned that the so-called angle-of-attack sensor can provide false readings in limited circumstances -- such as when a plane’s autopilot is switched off -- that cause the 737 Max to pitch nose downward. The sensor malfunction can essentially trick the plane into pointing its nose down to gain the speed it thinks it needs to keep flying.

 

The Boeing directive doesn’t call for operators to conduct new inspections or take other action. It merely stressed that pilots should follow procedures in the flight manual when encountering erroneous data. Following the protocol should be routine for pilots, though may be more challenging in the heat of the moment when equipment is malfunctioning and alarms are sounding.

 

American aviation regulators followed by issuing an emergency order Wednesday requiring that airlines follow Boeing’s instructions and add information to pilot manuals showing how to diagnose the problem and respond. Carriers will have three days to update their manuals under the order, issued by the Federal Aviation Administration, according to an emailed statement.

 

Quote

According to the “black box” data found in the Boeing 737 Max 8 aircraft, the airspeed indicator malfunctioned on its last four flights. The Lion Air aircraft, which had only been in use for a few months, is one of Boeing’s newest commercial aircrafts. The Boeing 737 Max 8 is currently in use by two US airlines, Southwest and American Airlines, though no issues have been reported by those airlines yet.

Following Boeing’s statement, the FAA has issued an airworthiness directive for the 737 Max which mandates safety protocols for US carriers, according to Bloomberg. The emergency order requires airlines to follow Boeing’s instructions if encountering the issue, which “could cause the flight crew to have difficulty controlling the airplane, and lead to excessive nose-down attitude, significant altitude loss, and possible impact with terrain.”

 

Quote

The sensor on the Lion Air jet been replaced the day before after it failed on a previous trip, the Indonesia National Transportation Safety Committee said in a briefing Wednesday. The malfunction can cause the plane’s computers to erroneously detect a mid-flight stall in airflow, causing the aircraft to abruptly dive to regain the speed it needs to keep flying.

On a previous flight from Bali to Jakarta, the angle-of-attack sensor feeding the captain’s flight displays registered a 20-degree difference from the device on the copilot’s side of the cockpit, the committee said. Pilots on that flight were able to compensate.

An angle-of-attack sensor that had been removed before that previous flight has been brought to the investigators and will be examined in the U.S., the Indonesian officials said.

 

I'm definitely glad the FAA issued the bulletin although it's a reminder of what a shame it is that their is no real aviation regulator outside of the US. Sure, ICAO exists but they don't serve the same job as the FAA in the US.

At any rate, this should make flying the Boeing 737 Max slightly safer and we'll see what the NTSB and FAA think once the investigation into the air crash has been completed.

[manikyath]

on the next season of air crash investigation...

[Coaxialgamer]

1 minute ago, manikyath said:

on the next season of air crash investigation...

"Jeff is boarding a 737 on route to Pangkal. It is a sunny day and the weather is calm. This should a routine trip for jeff".

 

I miss the passive-aggressive foreshadowing

[GDRRiley]

and this is why redundant sensors are key. 

[rcmaehl]

18 minutes ago, Coaxialgamer said:

"Jeff is boarding a 737 on route to Pangkal. It is a sunny day and the weather is calm. This should a routine trip for jeff".

 

I miss the passive-aggressive foreshadowing

 

Yep. Is "Seconds from Disaster" still a thing? Where they repeat the same info over and over to pad 30? minutes?

[rcmaehl]

Slightly off topic: Boeing's 777x folding wings

[Coaxialgamer]

5 minutes ago, rcmaehl said:

 

Yep. Is "Seconds from Disaster" still a thing? Where they repsat the same info over and over to pad 30? minutes?

Last episodes came out in 2014 so it seems to be pretty much done. Guess they ran out of fatal aircraft accidents?

[S w a t s o n]

So the first one failed the day before, they replaced it and the second failed again? I think Boeing fucked up and needs to issue a recall

[Coaxialgamer]

18 minutes ago, S w a t s o n said:

So the first one failed the day before, they replaced it and the second failed again? I think Boeing fucked up and needs to issue a recall

That's pretty much what an airworthiness directive is though

[S w a t s o n]

3 minutes ago, Coaxialgamer said:

That's pretty much what an airworthiness directive is though

Quote

The Boeing directive doesn’t call for operators to conduct new inspections or take other action. It merely stressed that pilots should follow procedures in the flight manual when encountering erroneous data. Following the protocol should be routine for pilots, though may be more challenging in the heat of the moment when equipment is malfunctioning and alarms are sounding.

American aviation regulators followed by issuing an emergency order Wednesday requiring that airlines follow Boeing’s instructions and add information to pilot manuals showing how to diagnose the problem and respond. Carriers will have three days to update their manuals under the order, issued by the Federal Aviation Administration, according to an emailed statement.

That doesnt sound like a recall to me

[manikyath]

2 hours ago, rcmaehl said:

Yep. Is "Seconds from Disaster" still a thing? Where they repeat the same info over and over to pad 30? minutes?

seat 16B, american airlines 737, dallas international airport, dallas, dallas county, texas, the USA, north america, earth, the galaxy, the milky way. in 30 minutes, josh taking seat for an ordinary flight will be dead along with 97 other people.

[DrMacintosh]

I still don't get how a trained pilot can be unaware of their aircrafts pitch and airspeed without indicators. 

 

Is the throttle open? If yes then the aircraft is probably going relatively fast. If not then the opposite. 

Is your stick all the way forward? If yes then the aircraft is probably pitched down pretty hard. 

 

The only time I think this would be an issue for a pilot is if you were in the middle of a cloud and had no frame of reference. 

 

[edit] Apparently the aircraft was equipped with a "feature" that automatically takes control of the aircraft to give it airspeed that it thinks it doesn't have. 

 

Trained pilots and manual overrides are usually good ways to keep planes from crashing. 

[Mira Yurizaki]

2 hours ago, S w a t s o n said:

That doesnt sound like a recall to me

The airliner didn't seem to take warnings of their staff or the maintenance seriously enough. Basically this sounds like an isolated incident.

 

If another airliner has sensor issues, even with proper maintenance, then that's a more compelling reason to ground all aircraft of that type.

[S w a t s o n]

1 hour ago, M.Yurizaki said:

The airliner didn't seem to take warnings of their staff or the maintenance seriously enough. Basically this sounds like an isolated incident.

 

If another airliner has sensor issues, even with proper maintenance, then that's a more compelling reason to ground all aircraft of that type.

Except that they replaced it the day before and it failed in a day for a second time. They seem to have done the maintenance, perhaps it was sloppy

[CaptainAirbus]

IMHO, Boeing simply tried to copy Airbus (automatically taking control when a stall is detected and other fly by wire safety systems) and completely and utterly failed. They should have made the systems more robust against small glitches but apparently didn’t. 

[Mira Yurizaki]

1 hour ago, S w a t s o n said:

Except that they replaced it the day before and it failed in a day for a second time. They seem to have done the maintenance, perhaps it was sloppy

Considering what the maintenance logs said prior to the flight, I'd say someone was grossly negligent in heeding the issues.

4 minutes ago, PilotMeeho said:

IMHO, Boeing simply tried to copy Airbus (automatically taking control when a stall is detected and other fly by wire safety systems) and completely and utterly failed. They should have made the systems more robust against small glitches but apparently didn’t. 

Airbus had a similar incident to this on, but the pilot was able to recover the aircraft.

 

Autopilot systems can't save you if the plane's sensors are faulty

[D13H4RD]

7 hours ago, DrMacintosh said:

The only time I think this would be an issue for a pilot is if you were in the middle of a cloud and had no frame of reference. 

Not entirely. Another situation where you can be spatially disoriented is during night flying. If you don't have a horizon outside as a reference point, you pretty much have to rely on an artificial horizon to know the aircraft's pitch. They've usually been reliable, but their failure, while not enough to cause a crash entirely on their own, coupled with no outside horizon and perhaps a crew with issues, can cause a fatal accident. Look up Korean Air Cargo Flight 8509 and Copa Flight 201. And especially look up Aeroperu Flight 603. That accident gives me chills every time I read about it. 

 

The control column on FBW aircraft also doesn't always directly indicate the plane's attitude/pitch. It's entirely possible to pull a side stick/control column forward but the plane to not directly respond to such controls since they're not directly connected to the control surfaces. This is especially true on FBW systems where the computers have complete authority. 

[D13H4RD]

2 hours ago, PilotMeeho said:

IMHO, Boeing simply tried to copy Airbus (automatically taking control when a stall is detected and other fly by wire safety systems) and completely and utterly failed. They should have made the systems more robust against small glitches but apparently didn’t. 

Airbus have had similar failures in the past, though not all of which are part of the aircraft's design.

 

Qantas Flight 72 suddenly went into a dive when an error in the ADIRU caused AOA and altitude binary info to be mixed, causing the envelope protection to pitch the A330-300's nose down by as much as nearly 10 degrees. The crew were able to recover and make an emergency landing at Learmonth Air Base without further incident. 

 

XL Airways Germany Flight 888T stalled and went into a nosedive due to malfunctioning AOA sensors caused by washing the aircraft without covering the AOA sensors, which ended up having water inside them. During the flight, the water subsequently froze and stuck the AOA sensors in their position. Without accurate data, when the crew deliberately attempted to stall the aircraft as part of their test flight, the stall protection failed to kick in. 

 

Another one isn't directly related to the FBW system, but more of intuitive controls and ATC confusion. Air Inter Flight 148 crashed into a mountain short of the airport after the crew mistakenly told the autopilot to descend at 3300 feet per minute (when they were targeting 3.3 degrees of FPA). Confusing word choices from the ATC didn't help the pilots' situation and during the investigation, whilst they found out that the 3300ft/min descend wasn't enough to cause the A320-100 to crash, because the aircraft hit a patch of turbulence, it triggered a safety feature in the autopilot that caused the aircraft to descend at a faster rate, ultimately being another link in a series that resulted in the aircraft smashing into the mountain. The fact that the A320-100 operated by Air Inter was not equipped with GPWS was another major factor. 

 

Boeing isn't really new to FBW. The Boeing 777 for instance is one of the first Boeing jetliners to use FBW and it's been a very reliable aircraft. 

[jagdtigger]

4 hours ago, S w a t s o n said:

They seem to have done the maintenance, perhaps it was sloppy

This is my opinion only but i would send the offending part to Boeing for analysis and have the plane grounded until i hear back from them... Yes it is expensive but IMHO they should always expect the worst in these situations where a mission critical system suddenly dies on them.

[D13H4RD]

This crash eeriely reminds me of some previous accidents. 

 

• Birgenair Flight 301: Boeing 757-200 from Puerto Plata to Frankfurt that crashed into the Atlantic Ocean shortly after take off, killing all 189 passengers and crew. The cause was a blocked pitot tube that fed erroneous information to the captain's ASI alongside the autopilot, which reacted erroneously due to receiving faulty data. The cascade of contradictory airspeed and stall warnings added to the confusion in the cockpit, which culminated when full thrust was applied, of which the left engine flamed out due to the plane's already high pitch, causing the 757, now with its right engine on full thrust, to go into a spin for the last moments of the flight before crashing into the Atlantic. The first officer's ASI was later found to be displaying the accurate airspeed all this while. 
• Turkish Airlines Flight 1951: Boeing 737-800NG from Istanbul to Amsterdam that stalled and crashed just short of the runway at Schipol Airport, killing 9 people including the cockpit crew. The cause was a faulty radio altimeter, which fed incorrect data to the autopilot, which subsequently put the 737 into "Retard Flare" mode (reducing engine power and pitching the plane to upwards just before touchdown). However, whilst the altimeter itself wouldn't have caused the crash, the crew was heavily preoccupied with the landing and didn't take notice of the warning signs (red bars on the ASI amongst other things) and by the time the stick shaker activated, it was too late and the aircraft stalled before crashing into the ground. 

XL Airways Germany Flight 888T, an Airbus A320-200 that stalled and crashed into the Mediterranean Sea alongside Qantas Flight 72, an Airbus A330-300 that suddenly went into an uncommanded but recoverable dive also came to mind. 

[CaptainAirbus]

On 11/9/2018 at 9:39 PM, D13H4RD said:

 Boeing isn't really new to FBW. The Boeing 777 for instance is one of the first Boeing jetliners to use FBW and it's been a very reliable aircraft. 

Yes. The 777, 787 and 747-8 (partial FBW) all use FBW control systems. But the 737max was the first Boeing to add stall protections into the system, something that Boeing has not done before and didn’t even disclose it to pilots or operators of the jet. The prior Boeing FBW jets only had the very basic protection. 

[D13H4RD]

6 hours ago, PilotMeeho said:

Yes. The 777, 787 and 747-8 (partial FBW) all use FBW control systems. But the 737max was the first Boeing to add stall protections into the system, something that Boeing has not done before and didn’t even disclose it to pilots or operators of the jet. The prior Boeing FBW jets only had the very basic protection. 

Don't the 777 and 787 have flight envelope protection? 

[CaptainAirbus]

17 hours ago, D13H4RD said:

Don't the 777 and 787 have flight envelope protection? 

Only the most basic. It limits overloading the flight surfaces and overloading the structure in general, but didn’t have anything in place to protect against stalls. It had very basic over bank and pitch limits, but they were at the extremes, way over 50 degrees pitch or bank before they kicked in.