Countries Restricting 737 MAX Flights After Second Crash

[jwperry]

Boeing's system here works a little differently than other systems have. From what I can read on the system, I personally don't particularly like how Boeing implemented it (as an aircraft systems engineer and private pilot); I don't like that it works off only one sensor at a time and I don't like that it just add in trim input without some kind of annunciation that it's doing something (IMHO it should at least pop up an "MCAS ACTIVE" advisory message for a few seconds or something). But after the Lion Air crash I would think anyone flying one of these would know about MCAS and how to deal with it if it starts misbehaving.

Some larger aircraft that aren't fly-by-wire, particularly those with T-tails, have a system that adds a control input to avoid a stall. But at least on the aircraft I work on, it's not a somewhat-subtle trim input--it's a very noticeable shove forward that you won't mistake for anything else.


Were I a betting man, I'd bet a beer or two that this accident has nothing whatsoever to do with MCAS. Unfortunately, even if I'm right, the airplane will probably wind up forever saddled with an undeserved reputation for being "dangerous".

Fair enough, the systems I'm familiar with provide crew advisory warnings when the system activates; it is both audible & visual cuing. If 737 MAX drivers aren't receiving an EICAS message when this activates than that is poor implementation of one of the better crew work shedding safety systems available...

[Suvorov]

Fair enough, the systems I'm familiar with provide crew advisory warnings when the system activates; it is both audible & visual cuing. If 737 MAX drivers aren't receiving an EICAS message when this activates than that is poor implementation of one of the better crew work shedding safety systems available...

There is no EICAS on the 737 up to and including the Max. The plane in very antiquated in this regard. My understanding is that the decision not to place EICAS in NG and Max models was due to commonality of flight decks.

[Suvorov]

There is nothing subtle about trim inputs in a 737 flight deck. The trim wheels are enormous, relatively speaking, so you can manually turn them if need be. Trim inputs involve those wheels spinning that are loud and very noticeable.

The normal takeoff and climb sequence involves automated trim without additional annunciation. But that is expected behavior at that point in the climb.

I have zero experience with the Max but I am curious if MCAS activates without letting the crew know.

This was a question I had. I posed to question to our training department and they assured me that MCAS activation will result in the trim wheel spinning. MCAS is very similar to the speed trim you are familiar with but has different parameters for activation. Like the speed trim it can be overridden with the electric trim switches as well as trim cutout switch’s. It will not however be overridden by the yoke cutout switches.

One of the parameters of MCAS is it is only active with flaps up. From what I understand the airplane in Ethiopia never reached 3rd stage climb which means MCAS should NOT have activated regardless of an AOA vane or other ADC irregularity. All that said - there may be a ghost in the machine.

My speculation is that dual AOA input requirement will be one of the updates to the software.

[jwperry]

There is no EICAS on the 737 up to and including the Max. The plane in very antiquated in this regard. My understanding is that the decision not to place EICAS in NG and Max models was due to commonality of flight decks.

Call Garmin, they'll put a G3000 in it for you.

[GardoneVT]

We should note that not every country has the same aviation culture seen in the US. As observed earlier, in some countries crew training,CRM and aircraft maintenance aren’t professional creeds but “if Allah wills it”. Some Asian airlines have epic CRM horror stories. All it takes is one failure in those three categories to cause a fatal and expensive problem.

[Suvorov]

Call Garmin, they'll put a G3000 in it for you.

The level of sophistication that is common in new GA airplanes blow anything coming out of Seattle or Toulouse away.

[TGS]

Really interesting stuff to read from the airline guys here.

Question for you commercial guys.....I only ever flew single engine props. In a 152 or Cherokee, you could be near unconscious and you'd still get enough feedback from the platform to wake you up prior to stalling.

With these big busses, what is the significance of the built in stall protection? Why is this so important? Is there simply not enough feedback with an airliner to detect an impending stall?

[rayrevolver]

Really interesting stuff to read from the airline guys here.

Question for you commercial guys.....I only ever flew single engine props. In a 152 or Cherokee, you could be near unconscious and you'd still get enough feedback from the platform to wake you up prior to stalling.

With these big busses, what is the significance of the built in stall protection? Why is this so important? Is there simply not enough feedback with an airliner to detect an impending stall?

You don't want to stall a big airplane. The altitude required to recover is in the thousands of feet, not hundreds like your 152. And the passengers will be pissed!

I am not an airline guy but I would hazard a guess that those guys have never stalled or come close to stalling a commercial airliner in real life. That said, I was in the jump for 31 stalls on one flight during the 737 certification process. These were yoke in your belly until the nose dropped full stalls.

There is a lot more feedback from the airframe then I can ever remember in a Cessna or other straight wing airplane. I will let our professional pilots respond to what they can see, hear, and feel (EFS firing!) from their sims.

The initial buffet in a 737 feels like driving an old truck on a washboard dirt road. You start getting bounced around. Deterrent buffet is obvious and dare I say violent, the banging around in the cockpit was such that I was waiting for the DUs to fallout. Don't forget that the distance from the cockpit to the wing is say 50-70 ft and the fuselage is a bendy tube. The cockpit gets whipped around pretty good when you start buffeting.

Once you hit deterrent buffet, with all the lights and sounds, stick shaker, and stick forces, it should be obvious you are about to stall.

[GJM]

Since there is discussion of G3000, the jet I fly has Garmin G3000, and this is what the avionics suite looks like at altitude.



What is even crazier is how capable the avionics are in the light sport Cub I fly.

[HeavyDuty]

Some news outlets are reporting the US is grounding the fleet.