tvon

Here are the reactions from US carriers that fly these planes: Southwest, American and United:

https://www.usatoday.com/story/trave...ic/3127692002/

They are all keeping them in the air. United doesnt fly the max 8 but does fly the max 9, which i understand to be just a longer version of the 8 (correct me if im wrong)

sddjd

The implementation of MCAS has nothing to do with inherent instability- the M8 has almost the same static margin as the 73H which clearly has no stability issues. If a fault in an AoA sensor causes MCAS to command a nose-down stab trim the runaway trim procedure is followed. Oddly the FAA advisory applies to the M8, while the NG series as a whole also has a stall protection feature integrated into the FCC that will trim the aircraft down in a stall. Too much is being made of "hidden" systems, when the manifesting result falls directly under a procedure that has been in place for decades. If pilots fail to do so, as seems apparent from the data in the Lion Air crash, they fight a progressively losing battle against the stabilizer with the elevators that can only end one way.

With zero data on the ETH crash it's pure speculation, but it's definitely acceptable to consider if there is an AoA sensor/system problem on the M8 but it's not an issue that should lead to hull losses (as evidenced by the Lion Air crews that flew the ill fated jet previously).

The original 737 design's age is irrelevant considering the lack of similarities between that air-frame and those flying today. It's competitor is almost 40 years old and similarly will be flying for decades into the future with new configurations, systems, etc.

DCP2016

The MAX 8 is statistically more dangerous than the 737 NG's and the A320 family.

As for your second paragraph, that is completely false. The 737-900 was already pushing the design limits of the 737.

The MAX's (hence my Frankenstein comment) take it a step further, with many aerodynamic drawbacks that Boeing has attempted to correct with software crap that obviously isn't working. That's not even talking about the mess that is the 737-10.

I love the 737 line, but it should've ended when they introduced the NG's.

arjaok

I'm flying OAK-MSY tomorrow on a MAX 8 with southwest and just got a notification offering me a free flight change as there are "some issues (weather, etc)" that may affect my flight for tomorrow. Any chance this is the first step to them taking these planes out of service for a bit?

sddjd

The geometric changes to the fuselage were limited to tail cone reshaping and some modification near the stabilizers that remove the need for the vortex generators on previous models while improving fuel burn through better aerodynamics. The engines (larger) were located on new pylons that, in addition to providing the necessary ground clearance, provide better aerodynamic positioning relative to the wing. The primary notable software changes relate to spoiler operation that reduces weight and improves flow and stopping distances on roll-out.

These drawbacks somehow add up to a 21k increase in MTOW and a range increase of 800nm at slightly higher cruise speed.

I'm genuinely curious as to the aerodynamic drawbacks you reference. As for statistics, they can be tailored to any point desired. We could look to the a320 and note a window in time at which 33% of the in-service fleet had crashed (AF296 at Habsheim). That was not an indicator of the airworthiness of the a320, and it is highly speculative to make similar deductions regarding the MAX at this time.

Ripfree

Your comment is completely uninformed, even ignorant. First, putting new engines on a 50 year old airframe design is not any worse than putting new engines on a brand new airframe design. The age of the design is irrelevant. It's what you do to prepare the design for the new hardware that counts.

the MCAS was not necessary due to an inherently unbalanced aircraft. EVERY aircraft is unbalanced until you balance it. In fact, the MAX was rebalanced by extending the tail enough to compensate for the engine's having been moved forward a little. This was done because the new engine cowling has a larger diameter. To maintain ground clearance, the engines moved forward slightly so they could move up without redesigning the entire wing.

The larger issue is that the new engine cowl shape does something the older cowling did not. At very high AOA, such as climbout after flaps retracted, the cowls start developing unwanted lift the older cowls didn't. This new lift is concentrated ahead of the CL (center of lift) the plane has at lower AOA, such as during cruise. The effect is the plane suddenly wants to go nose high, when the wing is already fairly close to stall AOA. The inertia of the airframe makes it difficult to avoid over-rotating the nose upwards under normal pilot pitch control. This is only a problem when the flaps are stowed and the wing stalls at a lower AOA, like any other wing.

So to get around this, Boeing engineers came up with MCAS to keep the plane from stalling when over-pitching the plane upwards is imminent. The sensor inputs to this system are numerous, and there are math calculations done by the flight control computer. it could be bad sensors, or it could be an algorithm loop error. But it's not an inherently unstable aircraft. The problem with procedural changes to temporarily deal with the issue is that invariably some pilot doesn't get the email, as it were. I'm speculating the Ethiopian pilot was not aware how to switch off MCAS, nor to recognize it's erroneous onset. One thing is for sure--you don't want your aircraft design to have a CL that moves around with pitch if you can avoid it. And anything you affix to the outside of the engine cowls to spoil the lift they generate at high AOA would probably add drag, subtracting from the plane's economy and performance. Maybe then need to add a degree or two of flap at high AOA instead of a complicated computer controlled MCAS system. The plane knows what the AOA is without all the other sensor inputs. And the stall AOA is pretty much the same regardless of all the other sensor inputs, so maybe a simpler system would be more reliable.

LarryJ

None of the 737s are unstable.

The MAX has the MCAS system which, in rather extreme situations, will apply stabilizer trim input to bias the nose down to avoid a stall. Some other airliners I've flown have a stick-pusher which physically pushes the control yoke forward, quite aggressively, to lower the nose. The 737 does not need anything as aggressive as a stick-pusher to meet the certification requirements.

In the Lion Air crash, judging only by the information that has been released to this point, didn't have an MCAS failure. It had a bad angle-of-attack (AoA) sensor which fed invalid data to the MCAS system.

MCAS will not activate until the flaps are retracted. The flightstat data released on the recent accident indicates that they barely reached 1000'. Depending on the departure profile (NADP1 or NADP2), the flaps are not typically fully retracted until at least 1200' above the airport, sometimes as late as 3300'. Their vertical speed fluctuations started well below an altitude where the flaps would have been retracted. If that data proves correct, it would seem to contradict the theory of another MCAS activation.

The flight recorders have been recovered. If there was some type of aircraft failure, we should start hearing something in the next day or two.

Annalisa12

I admit I looked up an internal Asian flight coming up to see if it was a 737 Max 8. It wasn't. I think I would of changed it if it was.

SQTraveller

Looks like Singapore have just banned the arrival and departure of all 737 Maxes
Boeing 737: Singapore bars entry and exit of 737 Max planes

JamesKidd

Looks like China and now Singapore are bit more conservative in their approach. Other big operators of 737 - Canada, India, UAE are reassured with Boeing's and FAA's explanation.

lhrsfo

Australia has banned it as well, although only a handful of this type fly to Australia.

And now also the UK, which has about 30 aircraft based in the country.

Ripfree

Good point about the flaps. The weather was quite hot that morning, and the airport is over 7000 msl. The density altitude might have been quite high. I wonder if they pulled the flaps at around 8200 ft and stalled. Then recovered, climbed too steeply and stalled again. Pure speculation, I admit.

adenzin7

UK and Germany have closed their airspace for any max 8. Turkish is turning around already

yno

TUI as well as Norvegian have also grounded their max 8
(sorce: https://edition.cnn.com/world/live-n...ash/index.html)

ian_btv

Indeed. Sources, @DanielW? I think all of us here want facts before theories, and @LarryJ just posted some useful ones. I also suggest avherald.com (to everyone). All facts.