Official Aviation Thread...

[LateFan]

From what I've read, the 737 Max is still a "hydraulically-assisted" cable flight controls airplane. No fly by wire.

What they've been talking about, and with this bulletin, is the airspeed indicators and angle of attack sensors somehow think the thing is stalling, and the computer forces the nose down even if flying manually. If the sensors are messed up, fooling the computer, the pilot is fighting a plane that wants to dive.

What the "standard procedure" is to overcome that, I have no idea. It doesn't seem like there's time to be browsing through the manual for Section 378 Paragraph 5B.

The thing hit the water going fast. Engines still spinning, blades all mashed, fuselage "fractured." Landing gear and the engines are the biggest pieces.

[FLYNAVY]

I wonder how much is or is not being lost in translation with this bulletin. But if is as described, this sort of goes against literally decades of NTSB reports......ie if the stick shaker or pusher is moving unexpectedly, you probably aren't in the regime of flight you thought you were. This could be said for Air France, Colgan, hell even Air Florida decades ago. If this story is true, that is a bit disconcerting. I know you can override a stick pusher with enough force, but having the conviction to do that and the absolute certainty you are right is probably not historically supported by good outcomes. Obviously a crosscheck of pitch attitude and N1 will probably give you a pretty good idea that the airspeed indicator is wrong and thus the stick pusher is erroneously activated, but I can see the confusion that would arise from this sort of scenario.

[flyboyx]

I have a tendency to agree with navy. I don't fly the 73, but we have emergency procedures for this sort of thing on the airbus. basically, we are taught to turn off a couple of computers and get the airplane into a more manual configuration asap. in airbus speak, that would be what is known as getting the airplane into alternate law.

the 73(even the max) is a much more manual airplane than an a320 is. I would think that it sounds very reasonable that they should have been airborne long enough to switch to a more manual mode and "fly by the seat of their pants". who knows what the training program was like for those pilots? I don't want to sound like I am pointing fingers since I certainly was not there and do not have all the facts. makes you wonder though...

I don't want to stereotype, but it could have been a situation where the pilots would have had to "think outside the box" to save the day. assuming that the pilots were asian, sometimes as a culture they have a lot of difficulty with this concept. I would see culturally how if there was no procedure, or if they were unable to identify the correct one, that they just flew along continually trying the same thing over and over that didn't work.

[LateFan]

All very interesting.

So, they let this thing take off four times with serious problems. They changed out an AoA sensor, still had problems next flight. I don't know what they did after that flight, but the next day it crashed.

So, two bad parts in a row?
Installation error?
Wiring / connection problem?
Software / computer problem?
Design / engineering flaw?

I've never noticed one of these on a plane. You often see the pitot tubes, but I haven't seen the vane piece on the sides.

[FLYNAVY]

We have very similar AoA vanes on the FA-18. The more updated versions in the Super Hornet have been problematic over the years, owing to sticking/ratcheting. Long story short, there is a pretty simple procedure to deal with this, and the end result is something akin to the alternate law flyboy talked about the 'bus having. I'm not sure, reading the AD, if this procedure did not previously exist for the 737. Seems strange that it wouldn't have, since we have been flying these things for decades and I would expect that this would have occurred by now. Perhaps there is something very different about the MAX that I'm missing.

As a random aside, since we are talking about heavy metal, I've got 10 hours of 757 FFD and FFS sim time to get through in the next couple days. Should be interesting......never flown anything heavier than 61k lbs before, much less a transport cat aircraft. The place I'm ultimately trying to go only has 737s and a few A321's (for a short time longer), so it might be my only time "flying" something so large if my plans work out accordingly.

[flyboyx]

every jet airliner that I've ever flown has aoa sensors. I guess its the most efficient method of determining the direction of airflow over the wing(even though they are always located on the nose). I would assume that there are 3 of them on a 737 that each provide separate information to the instruments. one for the captain, the fo, and a backup. if only one fails, it should be fairly easy to figure out which one is putting out erroneous info and disregard that one. in a way, based on what I know if the culture over there, I could see that if the left side failed and the captain was a somewhat incompetent autocrat....a first officer too intimidated to speak up.....just speculation on my part. the other more likely scenario is probably the computers that receive inputs from these little guys probably went haywire.

good luck with your job search navy. I cannot think of a single airline here in the United States that fits into the category (of aircraft) you mention above. perhaps the closest being that one based up there in Seattle.

probably the hardest thing to get used to between your fighter and the airliner will be the sight picture on landing. the '75 is so much higher above the ground, I bet you will prang the heck out of a few landings before you get it sorted out. honestly, though....I've never been in a sim that actually lands like the real airplane does.

[FLYNAVY]

good luck with your job search navy. I cannot think of a single airline here in the United States that fits into the category (of aircraft) you mention above. perhaps the closest being that one based up there in Seattle.

probably the hardest thing to get used to between your fighter and the airliner will be the sight picture on landing. the '75 is so much higher above the ground, I bet you will prang the heck out of a few landings before you get it sorted out. honestly, though....I've never been in a sim that actually lands like the real airplane does.

Thanks! I was talking about the one based in SEA......they got the 321s from the VX merger, though I hear they are looking to offload them ASAP in order to order more MAX's.

I thought the actual flare/landing was pretty straight forward......the mechanics were actually pretty similar to the F-16 to include the same altitude where you start leveling the nose and pulling power, though it tended to float a little more than a viper. That being said, my learning curve really began once the thing was arriving on the runway in a strong crosswind. I chalked it up to my FA-18 experience, where making large force corrections with the nose wheel steering and/or rudders is a recipe for disaster......you generally want to minimize the drift, but be pretty damn ginger with your corrections back to centerline, and in the case of the 75, it just took a lot more physical force/deflection of rudders to get the same actual response. We also land in a partial crab with crosswinds, whereas the 75 used a partial forward slip easing to neutralize on touchdown.......so my standard kick out half the crab before touchdown yielded a little drift that I was slow to correct for (see above reasoning). Interesting experience though. Got to dead stick a landing after a dual engine failure near SLC. My initial sight picture from my Viper SFO days was pretty overly aggressive, roughly 15 deg nose down most of the way......the 75 glides much mo better at a very similar "best glide" speed, so I was very excess energy and accelerating rolling out on final and using a lot of spoilers and forward slip to try and make it happen. Did the "impossible turn" back to the opposite direction parallel with the remaining excess energy, and managed to make the runway. Used a decent amount of flap position judgement from my KC-135 background crew member in order to make that happen......im used to flaps half or full, or in the case of the F-16 whatever flap setting the FLCS deems appropriate actuated by lowering the gear handle (no flap switch), rather than like 47 different flap settings and what they actually mean in terms of performance :)

[tttoon]

The Max is still hydraulically powered, yes, just the speedbrakes are now fly by wire. It does seem to fly a little better than the NG, it's much more stable in speed. And the fuel burn is insane, about 2000kg/hr fully loaded vs. 2400 for an -800 with the same load and split scimitar winglets.

As to the crash, it seems they had unreliable airspeed and a slow trim runaway at the same time. Both failures should be pretty straightforward on their own, but multiple failures at the same time can quickly become very challenging.

[flyboyx]

our 320 classics with the cfm with burn about 28-2900lbs of fuel a side at altitude(say 37,000') and a cost index of around 8. under the same conditions, a Neo with a leap 1a will only burn about 21-2250lbs of fuel an hour per engine. I assume this is pretty similar to the metric 73 numbers you mention above? its a game changer really. in essence, the airplane is good for at least another hour of range, not to mention the fuel savings on a standard route. in theory, we are supposedly going to get a few 321 neo extended range airplanes. those have enough nuts to go to Europe from Cleveland or Atlanta.

[tttoon]

Yep, 2000kg equals about 2200lbs/hr, for 189 pax in the max-8. We're usually around cost index 20. And you get to play cold war with the overhead panel too! We're getting -10s in a year or two, they're looking at doing transatlantic stuff with those too.

[hoveringuy]

My understanding of the systems is that in the NG, a high AoA would 1) activate stick shaker 2)inhibit rudder yaw damping and 3) use Sys A hydraulics to re-bias the elevator feel to give more control pressure, but it wouldn't move the controls directly.

The Max has the additional feature of trimming the nose down which is the same as a control input. I also need to research a rumor that the high AoA also triggers a thrust increase in autothrottle.

So, a false high AoA signal could pitch the nose down and increase thrust...

[BlackbirdM3]

So this happened... I shot this as the owner was leaving Oshkosh.


Not to get too far off topic, here is 184 seconds over Oshkosh, at night. This is a single exposure shot of one of the night airshow performers.



This shot was kinda cool. That straight, bright blue beam of light was a laser that prompted a TFR to 99K feet. (Yes you read that correctly, 99000 feet.) The performer was in a Yak 52.


Will

[tttoon]

Nice, Will!

My understanding of the systems is that in the NG, a high AoA would 1) activate stick shaker 2)inhibit rudder yaw damping and 3) use Sys A hydraulics to re-bias the elevator feel to give more control pressure, but it wouldn't move the controls directly.

The Max has the additional feature of trimming the nose down which is the same as a control input. I also need to research a rumor that the high AoA also triggers a thrust increase in autothrottle.

So, a false high AoA signal could pitch the nose down and increase thrust...

The (unadvertised) new MCAS (Manual Control Augmentation System) in the MAX apparently does that. If a high AoA is sensed (error or not) the system commands nose down trim. The trimming is also much faster than the STS on the NG. Boeing's argument for not having the system in the manual is that a failure of the system just needs to be treated as a trim runaway. I'm hearing lots of airlines do not agree with that. We just got the bulletin today, stating basically that they will incorporate the system into the FCOM.

[LateFan]

A rare screw-up for Boeing? (which I hate to see)

Or a training lapse and poor communication?

https://www.reuters.com/article/us-indonesia-crash-boeing-explainer/explainer-unraveling-the-boeing-737-max-lion-air-crash-idUSKCN1NK2BE

"...as a result of the larger engines, which are placed higher and further forward of the wing, the jet’s balance changed. To address that, Boeing put in place more anti-stall protections, Leeham Co analyst Bjorn Fehrm said in an online post."

"An automated protection system called the Maneuvering Characteristics Augmentation System (MCAS) kicks in when the angle of attack is too high, when the plane’s nose is too elevated, threatening a stall."

"One of two angle of attack sensors on the Lion Air jet was faulty, according to Indonesian investigators."

"The U.S. Federal Aviation Administration (FAA) last week warned airlines that erroneous inputs from those sensors could lead the jet automatically to pitch its nose down even when autopilot is turned off, making it difficult for pilots to control."

"Lion Air’s flight manual did not contain information about the new anti-stall system, according to investigators and an airplane flight manual seen by Reuters. U.S. pilots were also not made aware in training courses, pilot unions say."

"Boeing Chief Executive Dennis Muilenburg told Fox Business Network on Tuesday that Boeing provides “all of the information that’s needed to safely fly our airplanes”."

"Pilots can stop the automated response by pressing two buttons if the system behaves unexpectedly, the FAA says.

That action is set out in a checklist used by Lion Air pilots for in-air troubleshooting, an instructor said. It is also required to be committed to memory by pilots."

"Pilots on a flight from Jakarta to Bali the day before the crash experienced a similar sensor issue but managed to land safely by turning off the system, the New York Times reported."

[hoveringuy]

I've always believed that, if the plane is trimming down and trying to fly you into the water, don't let it! Pilot controls (at least in Boeing) overcomes automation. Pull back hard, fly the plane, and figure-out why it was doing that later.