Ethiopian 737-8 MAX down. No survivors.

Now there is a investigation leak that a bird or FOD damaged the AOA sensor. That appears to be the link between the two accidents.

 

Image Unavailable, Please Login

 

Meanwhile latest news says the Ethiopian pilots followed Boeng’s procedure to turn of the MCAS and yet there was still a problem.

Who knows maybe they didn’t follow the full procedure or maybe there is more going on.

Said it before and I’ll say it again, Boeing has a huge problem and what I am seeing from them is a large quantum of poorly formed spin, not leadership.

Thais planes are not going to be flying this month and it’s going to get ugly.
Two pilots I know who fly 777’s said Boeing Comite’s two sins. One was building an unstable aircraft and the other was putting a system in that pilots could not override by working the yoke.

 

I keep hearing from my airline pilot buddies, " SHUT THE DAMN THING OFF! The 737 Max is not an unstable airplane. The latest info is that the AOA sensor was damaged and fed incorrect signals to the MCAS that then input responses that were not compatible with the situation. The MCAS software was not right but it could be shut off and manual control could be exercised. That's what I'm hearing.

 

Reports are the Ethiopian pilots turned off the MCAS followed boe ings procedures but still could t establish control. Maybe they were in over their heads, or maybe it’s something more.

Either way the pr for Boeing stinks and imo they’re not handling the situation well from a perception perspective.

 

You can have lots of airspeed and if the AOA is too high, most aircraft cannot fly. The Brazil coast crash illustrates that pretty well.

 

The problem is that you can't shut the MCAS off. You can only disable the electric trim, which in turn disables the MCAS. The next problem is that the MCAS can, very quickly, trim the nose down so far that the air loads on the elevator make it very difficult, to maybe impossible, to use manual trim to get the airplane back to a more normal configuration.

Well, you can use manual trim if you unload the elevator by pushing forward, but at low altitude that may be impossible.

It's a bad place to be.

 

Reading the latest official comments and recognising that the plane barely got 1000ft of the ground, I can understand that it could escalate very quickly and it's easy to say the pilots should've done this and should've done that.
I watched the Sully film and don't know how accurate it was but I'm sure it was a lot easier to return the plane forewarned (and forward planned) in the simulator than it was in the real world with real people on board.
This looks more and more like a human factors engineering issue, where the workload quickly overcomes the capacity and time available to act......or is there something else hidden in the software that's not been found yet?

Both of these crashes were in good daylight conditions so what on earth happens at night or in bad weather when you've lost visual reference in a high workload situation?

 

Thanks, Don. I admit that I don't know everything that I should about the fluid situation with the airplane and proper sequencing but I also realize that there have been no fatal incidents with Max's flown in this country...some of which have done the MCAS thing. This Max event now has the face of most crashes, a complex string of causes that managed to join hands to pull everything down. I suppose that I should just watch and listen.

 

Yes, I don't know how many issues there have been with Max's in the US... I do know someone who had flown with the captain of the Ethiopian flight and described him as "above average by any standard."

 

This is an interesting supposition. The regulations say such systems must be designed within a certain range of pilot effort. For the trim wheel the system must be designed for pilot effort of no less than 50 lbs but not more than 150 lb. Applying 150 lb tangential force on the trim wheel would extremely difficult in the best of circumstances. Probably near impossible with one hand while also trying to help recover the aircraft with the other. If the load on the elevator did indeed require that much effort to move the trim wheel then I think that points to other design issues that should be resolved as part of the fix, i.e. not just a software change.

 

Not to mention, in both cases, these guys were rocketing along low to the ground at a very very high airspeed which would have increased the loading on the elevator making it even worse to muscle it with an out of trim situation.

 

Prelim report-

1 FACTUAL INFORMATION

1.1 HISTORY OF FLIGHT

On March 10, 2019, at about 05:44 UTC (All times listed is Universal Coordinated Time (UTC), as recorded on the FDR.), Ethiopian Airlines flight 302, a Boeing 737-8 (MAX), Ethiopian registration ET-AVJ, crashed near Ejere, Ethiopia, shortly after takeoff from Addis Ababa Bole International Airport (HAAB), Ethiopia. The flight was a regularly scheduled international passenger flight from Addis Ababa to Jomo Kenyatta International Airport (HKJK), Nairobi, Kenya. There were 157 passengers and crew on board. All were fatally injured, and the Aircraft was destroyed.

The following is based on the preliminary analysis of the DFDR, CVR and ATC communications. As the investigation continues, revisions and changes may occur before the final report is published.

At 05:37:34, ATC issued take off clearance to ET-302 and to contact radar on 119.7 MHz.

Takeoff roll began from runway 07R at a field elevation of 2333.5 m at approximately 05:38, with a flap setting of 5 degrees and a stabilizer setting of 5.6 units. The takeoff roll appeared normal, including normal values of left and right angle-of-attack (AOA). During takeoff roll, the engines stabilized at about 94% N1, which matched the N1 Reference recorded on the DFDR. From this point for most of the flight, the N1 Reference remained about 94% and the throttles did not move. The N1 target indicated non data pattern 220 seconds before the end of recording. According to the CVR data and the control column forces recorded in DFDR, captain was the pilot flying.

At 05:38:44, shortly after liftoff, the left and right recorded AOA values deviated. Left AOA decreased to 11.1° then increased to 35.7° while value of right AOA indicated 14.94°. Then after, the left AOA value reached 74.5° in ¾ seconds while the right AOA reached a maximum value of 15.3°. At this time, the left stick shaker activated and remained active until near the end of the recording. Also, the airspeed, altitude and flight director pitch bar values from the left side noted deviating from the corresponding right side values. The left side values were lower than the right side values until near the end of the recording.

At 05:38:43 and about 50 ft radio altitude, the flight director roll mode changed to LNAV.

At 05:38:46 and about 200 ft radio altitude, the Master Caution parameter changed state. The First Officer called out Master Caution Anti-Ice on CVR. Four seconds later, the recorded Left AOA Heat parameter changed state.

At 05:38:58 and about 400 ft radio altitude, the flight director pitch mode changed to VNAV SPEED and Captain called out “Command” (standard call out for autopilot engagement) and an autopilot warning is recorded.

At 05:39:00, Captain called out “Command”.

At 05:39:01 and about 630 ft radio altitude, a second autopilot warning is recorded.

At 05:39:06, the Captain advised the First-Officer to contact radar and First Officer reported SHALA 2A departure crossing 8400 ft and climbing FL 320.

Between liftoff and 1000 ft above ground level (AGL), the pitch trim position moved between 4.9 and 5.9 units in response to manual electric trim inputs. At 1000 ft AGL, the pitch trim position was at 5.6 units.

At 05:39:22 and about 1,000 feet the left autopilot (AP) was engaged (it disengaged about 33 seconds later), the flaps were retracted and the pitch trim position decreased to 4.6 units.

Six seconds after the autopilot engagement, there were small amplitude roll oscillations accompanied by lateral acceleration, rudder oscillations and slight heading changes. These oscillations continued also after the autopilot was disengaged.

At 05:39:29, radar controller identified ET-302 and instructed to climb FL 340 and when able right turns direct to RUDOL and the First-Officer acknowledged.

At 05:39:42, Level Change mode was engaged. The selected altitude was 32000 ft. Shortly after the mode change, the selected airspeed was set to 238 kt.

At 05:39:45, Captain requested flaps up and First-Officer acknowledged. One second later, flap handle moved from 5 to 0 degrees and flaps retraction began.

At 05:39:50, the selected heading started to change from 072 to 197 degrees and at the same time the Captain asked the First-Officer to request to maintain runway heading.

At 05:39:55, Autopilot disengaged,

At 05:39:57, the Captain advised again the First-Officer to request to maintain runway heading and that they are having flight control problems.

At 05:40:00 shortly after the autopilot disengaged, the FDR recorded an automatic aircraft nose down (AND) activated for 9.0 seconds and pitch trim moved from 4.60 to 2.1 units. The climb was arrested and the aircraft descended slightly.

At 05:40:03 Ground Proximity Warning System (GPWS) “DON’T SINK” alerts occurred.

At 05:40:05, the First-Officer reported to ATC that they were unable to maintain SHALA 1A and requested runway heading which was approved by ATC.

At 05:40:06, left and right flap position reached a recorded value of 0.019 degrees which remained until the end of the recording.

The column moved aft and a positive climb was re-established during the automatic AND motion.

At 05:40:12, approximately three seconds after AND stabilizer motion ends, electric trim (from pilot activated switches on the yoke) in the Aircraft nose up (ANU) direction is recorded on the DFDR and the stabilizer moved in the ANU direction to 2.4 units. The Aircraft pitch attitude remained about the same as the back pressure on the column increased.

At 05:40:20, approximately five seconds after the end of the ANU stabilizer motion, a second instance of automatic AND stabilizer trim occurred and the stabilizer moved down and reached 0.4 units.

From 05:40:23 to 05:40:31, three Ground Proximity Warning System (GPWS) “DON’T SINK” alerts occurred.

At 05:40:27, the Captain advised the First-Officer to trim up with him.

At 05:40:28 Manual electric trim in the ANU direction was recorded and the stabilizer reversed moving in the ANU direction and then the trim reached 2.3 units.

At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and FirstOfficer confirmed stab trim cut-out.

At 05:40:41, approximately five seconds after the end of the ANU stabilizer motion, a third instance of AND automatic trim command occurred without any corresponding motion of the stabilizer, which is consistent with the stabilizer trim cutout switches were in the ‘’cutout’’ position

At 05:40:44, the Captain called out three times “Pull-up” and the First-Officer acknowledged.

At 05:40:50, the Captain instructed the First Officer to advise ATC that they would like to maintain 14,000 ft and they have flight control problem.

At 05:40:56, the First-Officer requested ATC to maintain 14,000 ft and reported that they are having flight control problem. ATC approved.

From 05:40:42 to 05:43:11 (about two and a half minutes), the stabilizer position gradually moved in the AND direction from 2.3 units to 2.1 units. During this time, aft force was applied to the control columns which remained aft of neutral position. The left indicated airspeed increased from approximately 305 kt to approximately 340 kt (VMO). The right indicated airspeed was approximately 20-25 kt higher than the left.

The data indicates that aft force was applied to both columns simultaneously several times throughout the remainder of the recording.

At 05:41:20, the right overspeed clacker was recorded on CVR. It remained active until the end of the recording.

At 05:41:21, the selected altitude was changed from 32000 ft to 14000 ft.

At 05:41:30, the Captain requested the First-Officer to pitch up with him and the First-Officer acknowledged.

At 05:41:32, the left overspeed warning activated and was active intermittently until the end of the recording.

At 05:41:46, the Captain asked the First-Officer if the trim is functional. The First-Officer has replied that the trim was not working and asked if he could try it manually. The Captain told him to try. At 05:41:54, the First-Officer replied that it is not working.

At 05:42:10, the Captain asked and the First-Officer requested radar control a vector to return and ATC approved.

At 05:42:30, ATC instructed ET-302 to turn right heading 260 degrees and the First-Officer acknowledged.

At 05:42:43, the selected heading was changed to 262 degrees.

At 05:42:51, the First-Officer mentioned Master Caution Anti-Ice. The Master Caution is recorded on DFDR.

At 05:42:54, both pilots called out “left alpha vane”.

At 05:43:04, the Captain asked the First Officer to pitch up together and said that pitch is not enough.

At 05:43:11, about 32 seconds before the end of the recording, at approximately 13,4002 ft, two momentary manual electric trim inputs are recorded in the ANU direction. The stabilizer moved in the ANU direction from 2.1 units to 2.3 units.

At 05:43:20, approximately five seconds after the last manual electric trim input, an AND automatic trim command occurred and the stabilizer moved in the AND direction from 2.3 to 1.0 unit in approximately 5 seconds. The aircraft began pitching nose down. Additional simultaneous aft column force was applied, but the nose down pitch continues, eventually reaching 40° nose down. The stabilizer position varied between 1.1 and 0.8 units for the remainder of the recording.

The left Indicated Airspeed increased, eventually reaching approximately 458 kts and the right Indicated Airspeed reached 500 kts at the end of the recording. The last recorded pressure altitude was 5,419 ft on the left and 8,399 ft on the right.

 

Very sobering to read......RIP

 

I figured when you hit the trim cutoff switches it completely shutdown the trim motor, leaving only manual (i.e. the wheel). Apparently not. So not sure exactly what those switches are supposed to do but appears they didn't do enough.

 

I believe they turned it back on. They couldn't move the manual wheel, so the electric was really the only option... the problem is, as soon as they released the trim switches, it started to run nose down at high speed.

 

I don’t know if this has been covered before, but for those of you that are familiar with the MCAS system.....is there any automated throttle control linked to any part of this system? Both planes were traveling at high speed seemingly due to the nose down profile that the MCAS placed them in, but you would have wanted to bleed off speed to lessen control forces to effect recovery and neither seem to have done so. This makes me wonder if, in addition to the trim down, the MCAS also advances throttle to “help” keep the plane flying....

 

I don’t believe MCAS has any linkage to the autothrottles. But, on underslung wing mounted engines, decreasing thrust would create a downward pitch and vice versa. Obviously they shouldn’t have let it get to over speed like they did, which made things worse for them when they had to use manual control forces to fight the trim.

 

I posted this in the 737-MAX conspiracy thread.

Image Unavailable, Please Login

Per Boeing: Normal electric trim control on the yoke can stop the MCAS-driven stabilizer movement, however MCAS will activate again within 5 seconds after the switches are released if the angle of attack is still sensed too high. Pilots can deactivate MCAS and automated control of the stabilizer trim with the cutout switches and can hand-crank the trim wheels on each side of the quadrant for manual trim. What is not clear is why the Manual Trim Control did not work as advertised.

 

Is it possible that the speeds the plane was going made trimming the plane more difficult?

 

AF447?

 

I don't know why I am responding, since you are talking about conspiracies and probably won't believe anything I say, but here goes...

It's no mystery why the manual trim didn't work. At high speed and with the airplane way out of trim, there are substantial air loads on the tail. And that stabilizer is a big piece of metal anyway. So the higher the air loads, the harder it is to move that wheel. In this configuration, the airplane was so out of trim that it was probably impossible to move the wheel. This is a big reason why it has electric trim in the first place.

I'm not a 737 guy, but I believe Boeing even says that in the manual.

 

I'm not a pilot. Fascinating to read the transcription above.
A question- is the trim control mechanically connected to the jackscrew that runs the stabilizer? That seems almost impossible due to the surface area and distance you'd have to cover to be able to move it. I bet the motor that moves the surface is substantial.
Another thing I've noticed in some of the simulation recreations is that the trim wheel is really spinning and it's a big wheel. It seems like it would be some risk to catching something like clothing.

 

The trim wheel is connected directly to the jackscrew via cables (2-pair, i.e. redundant system) that run the entire length of the fuselage, so yes the wheel moves even when using the trim switches on the yoke.
Image Unavailable, Please Login