canopus27

BTW, I haven't seen a link to the actual preliminary report, posted here yet.

So here it is:
http://www.ecaa.gov.et/documents/204...8-d7af1ee17f3e

expert7700

Here is a good article I saw posted:

Boeing’s effort to get the 737 Max approved to fly again, explained
A bigger problem than a software update.

yulred

skybluesea

delete

canopus27

Beyond Ethiopian Airlines (who lost a plane in the crash), please remind me of which other airlines, anywhere in the world, proactively grounded the MAX in advance of their regulatory body doing so? Because I don't recall any other airlines doing that.

Feel free to use the wikipedia page as a refresher, and by all means let me know about any omissions you find there and I'll update the page for you.
https://en.wikipedia.org/wiki/Boeing...tory_responses

InTheAirGuy

Let me put some perspective on the narrative

Ethopian Airline= African = Bad Pilots = plane crash
Lion Air = Asian = Bad Pilots = Plane Crash
Air Canada = Canadian = Good Pilots <> Except for Complex Night Runways in SFO

The Lev

This might help explain (sorry for long quote):
After Flaps up at B, you have the first MCAS nose down at 1 which stops at 2 (the FFC, Flight Control Computer, trim trace). Between 2 and 3, PF trims against. This causes MCAS to reset and trim again at 3 and it gets interrupted by PF trim at 4. Now MACS is identified and the Pilot Monitoring (PM, the First Officer) cuts trim with Cut Off switches after 5. We know this as the next attack from MCAS at 6 has no effect on Pitch trim units (the trace below FCC trim). Now the fight with MCAS is over and the crew starts turning back to the airfield after 05.40.45, Figure 1 Heading Disp (Displayed) trace.

The Crew finds however they can’t correct the nose heavy trim with the manual wheels, contrary to what is stated in the AD and in their Checklists. Speed is now at Vmo, the maximum design Indicated Air Speed (IAS) for the aircraft, 340kts.

The throttles are left at 94% thrust for the whole flight. This is higher than normal but this is a high takeoff. At 7,600ft it is a full 2,200ft higher than Denver, which is the US Benchmark for high takeoffs. And with Stick Shaker and IAS disagree you keep high thrust and fly a slow climb (the IAS disagree is present in the traces but not mentioned in the report specifically. We don’t have all the Crew callouts and discussions present in the report is my conclusion).

The high speed of 340kts indicated airspeed and the trim at 2.3 units causes the Stabilator manual trim to jam, one can’t move it by hand. The crew is busy trying to hand trim the next two minutes but no trim change is achieved.

At 7 the aircraft nose is dipping (see Pitch Attitude Disp trace) because PF can no longer hold against the Yoke forces we discussed Wednesday (Ctrl Column Pos L/R). PF decides he needs Electric Trim to stop the aircraft from diving. Cut Off switches are put to Electric Trim active. PF successfully trimmed against the last MCAS attack, he can do it again.

The insufficient trim mystery after re-activation of Electric Trim

After 7 PF commands Electric Trim Nose Up in two short cycles. I asked my selves (as did others) why these short trims? They are fighting to get the nose up to the extent they risk switching in the Electric Trim again. Then why not trim nose up continuously or for at least long cycles once Electric Trim is there? It took me several hours to find an explanation. Here my take:

To understand the blip trims one must have flown fast jets at low altitude. At the speed ET302 is flying, 360kts, it’s hypersensitive to trim. The least trim action and the aircraft reacts violently. Any trimming is in short blips.

As PF holds the nose up with a very high stick force, now for a long time, he’s sensitivity to release stick with trim is not there (this is what Pilots do when they trim nose up, otherwise the aircraft pitches up fast). He trims therefore in short blips and has difficulty to judge the trim effect he has achieved. His is not flying on feel. He can’t, he is severely out of trim, holding on to the Yoke with a strong pull force.

Anyone who has flown a grossly out of trim aircraft at high speeds knows your feel is compromised. The sensors you have to rely on are your eyes, not your hands.

PF has the horizon glued to read the aircraft. The result is the short nose-up trims we see. The nose goes up and the stick force needed is reduced. His judgment is; this is enough for now, it was a powerful response. Any MCAS attack I now trim against, then I correct my trim if I need to.

But the aggressive MCAS, trimming with a speed 50% higher than the pilot and for a full nine seconds, kicks in at 8 with a force they didn’t expect. Speed is now at 375kts and MCAS was never designed to trim at these Speed/Altitude combinations. Dynamic pressures, which governs how the aircraft reacts to control surface movements, is now almost double it was when last MCAS trimmed (Dynamic pressure increases with Speed squared).

The Pilots are thrown off their seats, hitting the cockpit roof. Look at the Pitch Attitude Disp trace and the Accel Vert trace. These are on the way to Zero G and we can see how PF loses stick pull in the process (Ctrl Column Pos L). He can barely hold on to the Yoke, let alone pull or trim against.

His reduced pull increases the pitch down further, which increases the speed even more. At 05.45.30 the Pilots have hit the seats again (Accel Vert trace and Ctrl Columns force trace) and can start pulling in a desperate last move. But it’s too late. Despite them creating the largest Control Column movement ever, pitch down attitude is only marginally affected.

We have Control Column displacement this time, JT610 was Force. If the elevator reacts to these displacements, at the Dynamic Pressure we have, we should have seen the diving stop. The lack of reaction to the large Control Column displacement of two Pilots pulling makes me think we now have blowback. This is not a design fault, we are well beyond Vmo. But it explains the rapid dive, unhindered by the Pilots’ actions.

It’s easy to say “Why didn’t they trim then?”. Because they are going down at 20 degrees nose down (which is a lot, a normal landing approach is 3°) and at 400kts. Then you just pull for all you have. And the aircraft is not reacting to the largest Control Column displacement since takeoff. This makes them pull even harder, the aircraft is unresponsive and they are fighting for theirs and all the passenger lives.

https://leehamnews.com/2019/04/05/bj...irst-analysis/

yulred

canopus27

This all sounds dishearteningly feasible.

(shudder)

TheCanuckian

As the story continues to unfold, I find myself wondering: What will it take for me to get back on a MAX? And even more so, to get my family on? My next scheduled MAX flight is YVR - HNL in October, and that's with the whole family. What kind of reassurance will I need from Boeing, the various regulatory bodies, and Air Canada, before I usher us all onto that flight? How long will I need to have seen MAXs flying problem-free before I have that level of confidence in them—confidence to put the people I love most aboard one? If, as some have speculated, the MAXs come back online in late summer or early fall, do I want us to be aboard the first few hundred flights in which we've now been assured everything is okay? And will Air Canada extend some kind of help to those who just aren't yet convinced? This is the stuff that perplexes me.

yulred

RangerNS

It is becoming clear that the regulator process is collaborative and ongoing (not that that is really news to me), as opposed to some situation where an OEM sends the regulators a finished aircraft to put through some evaluation process. Being obviously bad for everyone that there are unsafe aircraft flying around, an approach of "trust, but verify" by regulators has historically been enough... But the process for the MAX apparently was "trust" without any follow up.

And globally, the inter-sovereign process was always "just trust". Garneau's lap-dog level of FAA alignment has me with zero trust for Canadian regulators.

So, my line may be EASA being satisfied. Europe, from RoSH to GDPR to grounding the MAX, is obviously unconcerned with appeasing the irrational colonists.

skybluesea

delete

yulred

mj188

Perhaps. On the flip side, doubling of traffic doesn't necessarily mean doubling of flights. Larger aircraft can go a long way. And so can point-to-point routings. Ten years ago I was on 50 seaters a lot. That's given way to 70 or 90 seaters I used to fly A319 and 737-700 often, and now see a lot more A321 and 737-900 on the same routes. And you need less block hours to operate YWG-YLW nonstop than to fly the same number of passengers YWG-YYC-YLW, for example Which works as long as the traffic is there - and in a traffic growth scenario, that's what we're talking about.

Of course retirements and replenishment of seasoned crews is another question, but I'd think the regionals are going to suffer more in that regard than the majors.

And also not to say automation won't come, whether strictly "necessary" or not. It could be a good thing, but no doubt will be a disruptive change.