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Discussion in 'Flight Following' started by Anymouse, Mar 10, 2019.
I think I've heard that there are jet fighters that would be unflyable without software.
This is not exclusive to the Max. Most under-slung (below wing) jet aircraft will "nose up" when you add power. The only issue with the Max in comparison is that the control forces reduced vs other types.
Or IF certain conditions are present like excessive airspeed. There are now articles being published (WSJ) that are more specific to the 302 crew actions or lack there of. Time will tell. Unfortunately, loss of or errant actions of aircraft automation happen everyday but things usually work out in the end. Foe example, several weeks ago a 787 had both engines roll back power on their own during an approach in Japan. But the crew managed to get the aircraft on the ground. Have they published the cause or ground the 787 fleet? No. Is this the first time this has happened with new models engines? No. So why the difference now?
On AviationWeek today (requires free account)
Informative, especially Boeing’s quoted, on the record responses.
Three things I took away:
1) It appears MCAS will activate beginning at 20* nose up AoA, maybe lower.
2) Boeing’s quoted comments appear to have had both a legal and corp comm review.
3) The proposed changes are intended to result in bad AoA data not turning into a helmet fire.
On a 737: how is stick force transmitted to the flight crew? It isn't a direct coupling like a 172, it has hydraulics between the column and tail...doesn't it?
I'm wondering why stick forces would ever be so strong they couldn't be overcome, like power steering, and be pulled to the stops? I thought I read, somewhere in this thread, that hundreds of pounds of force might have been necessary, that seems excessive, but I don't understand how all the feedback systems work.
There are several planes that are literally unflyable without a computer, including some fighters. I've no issue with computers figuring out how to implement the pilot's commands.
I think it’s more like loading anvils in the tail. CG can be designed in. Thrust and rudder are side effects.
this wasn't a CG issue.....
Like I said before stick forces are simulated by the elevator feel computer which has it's own independent airspeed sensor (pitot tube)
If there's an elevator feel computer why did they need to invent MCAS to increase the control pressure?
Regulatory requirement to maintain the 737 type certification due to non-linear control forces without MCAS.
This is why God created air accident investigations. You are assuming facts not in evidence.
I guess I'm trying to ask is why the elevator feel computer couldn't be modified to do that.
The elevator feel computer is not exactly what you might be thinking, it's basically a mechanical device in the tail and senses only airspeed through it's own independent devices, it has no knowledge of AOA. All large airliners have them. Without it you would wildly over-control the tail at higher speeds.
Sure it is. If the thrust line/cg relationship isn't what it is, there would be no need for MCAS.
light pitch control forces might "feel" like a CG issue....but it wasn't a CG issue. Irregardless of the actual CG the control forces can be whatever the designer chooses....and there is a range that's spec'd out....hence the reason for MCAS on several other models of Boeing aircraft.
Interesting. Which models have it? I’m typed on the 757, 767, and 777 and as far as our manuals say (which we now know doesn’t mean much) none of them have the MCAS system like the Max has. The 777 has some pitch protection systems, but nothing like the MCAS.
Ok, it's not a cg problem in the classical weight distribution sense of stability. It's a thrust line in relation to cg that results in the non-linear pitch forces problem.
So, I lost track of this thread...but has it been discussed yet that the flights would have been ok if only they had an AOA sensor?
Well technically they had it, but needed it to be working.
Pretty certain it’s only the three Max variants.
The 767 tankers (KC-46) have a version of the MCAS. Here's one ref:
I’m sure you’re right. Only the 737 Maxes have them.
From what I understand, this pitch system is for refueling only to help with the bow wave effects of some of the larger receiver aircraft. I don’t know if it relies on AoA input, or more likely it’s probably based on pitch/altitude hold, but I don’t really know for sure.
I'd call it a control forces issue in that configuration.....controlability.
It's in there Capn....you just don't know bout it.
A year ago, I would have said “no way,” it’s not in the manual, it’s not on the jet. Now seeing that Boeing has been playing fast and loose with what systems they decide to document, it wouldn’t surprise me. But... I still think we don’t have it on the 757/767. With all this brouhaha surrounding the MCAS, I’m sure if one of our fleets had it, Boeing would have put out an emergency bulletin explicitly describing what types use MCAS, if any. The fact I haven’t seen an FCIF yet telling me that my aircraft has MCAS leads me to believe that we don’t have it. Nor does the 76 or the 777. But, who knows at this point. I’ll see if I had email our fleet test pilots and see.
so you think you know that thing down to the code level?......lol
No, of course not. Neither do you, I’m sure. I’m guessing the Boeing test pilots don’t even have that kind of base programming knowledge. I bet the only ones that know those airplanes down to the code level are the software engineers themselves.
But, seeing all the bad press Boeing has gotten for not putting a major system into the flight manuals, nor even letting the pilots know about it, I’m pretty confident that if ANY of their aircraft variants out there had a system similar to the MCAS they would be scrambling to ensure every operator of those fleet types now knew about it and it was trickled down to us, the end users.
Here’s the thing. The code probably isn’t the issue. The issue appears to be what the logic tree is when erroneous information is fed to it.
That’s the bigger challenge Boeing has to overcome. Notice there’s been more than a couple who have fully trusted Boeing has provided them with the information necessary to successfully recover from abnormal conditions occurred during flight.
That trust was broken with the revelation of MCAS in the 737, after the fact.
Had Boeing applied the rigor we’re seeing now in the immediate aftermath of the Lion Air crash, it’d be a different story.
the response is no different.....hence the lack of clarity.
I think Mr. Flynn was making a joke based on previous threads in which AoA sensors were being touted for GA aircraft.
I know. Tried to extend the play and failed.
Focus on the pilots in this article.
And the discussion continues to expand to include the certification side as well as the pilot side. Here's one example:
"The source indicates the crew appeared to be overwhelmed and, in a high workload environment, may not have followed the recommended procedures for re-trimming. Boeing’s stabilizer runaway checklist’s second step directs pilots to “control aircraft pitch attitude manually with control column and main electric trim as needed,” according to one U.S. airline’s manual reviewed by Aviation Week. If the runaway condition persists, the cut-out switches should be toggled, the checklist says."
"The certification process relies on crews 'flying the plane' (see magenta line video) when something goes awry. All systems eventually rely on giving the bag of bolts to the flight crew - that's what alternate and direct law are about in A and it is why the flight crew are there. It was expected that a response to inappropriate MCAS would be autopilot off, autothrottle off, manual trim to correct to neutral trim then stab trim off and fly the plane. Perhaps certification should not rely on the crews following these NNC and other checklists? That is a big can of worms and leads to autonomous aircraft that can handle non-nominal cases that the crew were there to handle."
Counterpoint to the seekingalpha piece from another pprune post, and good questions to ask:
Totally agree that this is an effort to build the public opinion case for pilot error. I find it quite remarkable that it takes such a long windup to finally conclude that the crew did not do everything perfectly. Duh. No human ever does.
And then it just stops. What is the point of finger-pointing? How can that help anyone in any way? (Except perhaps Boeing's reputation, but even that is doubtful.)
A finding of "Human Error", can never be the end of an analysis, rather it must be the start of asking questions such as:
What was the exact situation the operators were in?
What was the information they could get?
Was some information maybe ambiguous? Even contradictory? Hard to find?
How much time did they have to find it?
How much time did they have to analyse it?
Were they trained to evaluate the information properly?
Were there perhaps multiple anomalies requiring different, possibly even contradictory procedures?
Was there perhaps cognitive overload?
Did they (could they?) have an understanding of why the system did what it did?
What additional information do we have now, that the operators at the time did not have? (The easy one: we know that what they did eventually led to an unrecoverable situation. They didn't. Or else they wouldn't have done it.)
Which again leads to: why did they do what they did?
How can we prevent:
... crews from doing the same things again, or better still:
... anyone from getting into the situation in the first place?
I’m not surprised an investment advice website would be producing an opinion piece to support or counter whatever position the advice they’re giving is.
Especially when both authors are Boeing drivers, and at least one of them has his own financial analysis firm, focusing on the aviation industry.
Interestingly enough, that guy doesn’t hold a CFP designation, so has no real fiduciary responsibility.
I’m thinking that jet fighter pilots are more the cream of the crop. I don’t think that is a standard that can be expected from all commercial airline pilots, throughout their whole career that can be expected. I know there are automated systems on airliners, but this seems unconventional and not necessarily well thought out, as well as bugs reported.
There is a level of ability and competence expected, and many airline pilots are former jet fighter pilots I understand but with so many pilots, this seems to an outsider to be on the edge of responsible.
With more and more automation, the code becomes more and more complex as it is tasked with mor and more of the responsibility. As a programmer, I know testing has to be rigorous and honest. And even then there will be mistakes.
....and the job of the test pilot is to ensure all "safety critical" permutations are discovered...
Even then, it depends on who writes the test plan. There are a lot of cooks around the broth pot.