Boeing 737 Max Software Fixes Due to Lion Air Crash Delayed
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Reuters - MARCH 21, 2019 / 9:36 PM ET
American Airline pilots expect to test 737 MAX software fix in Boeing simulator
https://www.reuters.com/article/us-e...-idUSKCN1R306I
American Airline pilots expect to test 737 MAX software fix in Boeing simulator
https://www.reuters.com/article/us-e...-idUSKCN1R306I
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Reuters - MARCH 21, 2019 / 9:36 PM ET
American Airline pilots expect to test 737 MAX software fix in Boeing simulator
https://www.reuters.com/article/us-e...-idUSKCN1R306I
American Airline pilots expect to test 737 MAX software fix in Boeing simulator
https://www.reuters.com/article/us-e...-idUSKCN1R306I
Salute!
A sim is a sim is a sim..........
The best way to show an "old" 737 driver MCAS and the new "fix" is to have the sucker in the real plane.
- have a means to disable MCAS and either slow to get increased AoA or do a wind up turn like the golden arms do on a test profile.
- note the back pressure as the plane gets to the stall shaker and compare to the "old" 737 they flew
- enable MCAS and repeat
- note the back pressure difference.
Demonstrating the malfunction that happened with the Lion accident would also be a good idea, but at a reasonble altitude
Gums sends..
A sim is a sim is a sim..........
The best way to show an "old" 737 driver MCAS and the new "fix" is to have the sucker in the real plane.
- have a means to disable MCAS and either slow to get increased AoA or do a wind up turn like the golden arms do on a test profile.
- note the back pressure as the plane gets to the stall shaker and compare to the "old" 737 they flew
- enable MCAS and repeat
- note the back pressure difference.
Demonstrating the malfunction that happened with the Lion accident would also be a good idea, but at a reasonble altitude
Gums sends..
Yo gums, ‘a sim is just a … ‘ until it isn’t.
A common difficulty in simulation is the friction associated with conventional cable runs, cranks, pulleys, etc and how they change with in-flight loads.
This could be major issue in the simulation of manual trim-wheel operation, even more so if the stabiliser forces were so excessive that they prevent trim wheel movement - see discussions Boeing advice on "aerodynamically relieving airloads" using manual stabilizer trim
Re ‘a good idea’ demonstrating the malfunction: given the current level of knowledge, unknowns, variables; then the flight test planning might judge the need to roll the aircraft towards the inverted so to use the adverse trim condition to affect ‘upwardness’, then unload-load the elevators, and move the trim wheel.
Easy in your Viper, not such a good idea for a commercial aircraft flight test.
A common difficulty in simulation is the friction associated with conventional cable runs, cranks, pulleys, etc and how they change with in-flight loads.
This could be major issue in the simulation of manual trim-wheel operation, even more so if the stabiliser forces were so excessive that they prevent trim wheel movement - see discussions Boeing advice on "aerodynamically relieving airloads" using manual stabilizer trim
Re ‘a good idea’ demonstrating the malfunction: given the current level of knowledge, unknowns, variables; then the flight test planning might judge the need to roll the aircraft towards the inverted so to use the adverse trim condition to affect ‘upwardness’, then unload-load the elevators, and move the trim wheel.
Easy in your Viper, not such a good idea for a commercial aircraft flight test.
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Gums
Salute
Indeed , would I love to take the MAX to the limit, but I pass! Except with a Full Boeing Testpilot!
Firstly, this day and age I think if it is NOT possible to reproduce and recognize in the sim, most Air-framers have a training OR a design problem.
Agree, the sim is not the aircraft, but civilian use have strict limitations as opposed to mil. ( Mind you we also have to know and avoid the stall) .
Think 737-800 vs P8 Poseidon.
Remember
European TREs and line trainers has possible never done a spin in a Cessna 172, never mind recovered a MAX from a full stall/incipient spin!!
Radical idea, not happening Sir!
Regards
Cpt B
Indeed , would I love to take the MAX to the limit, but I pass! Except with a Full Boeing Testpilot!
Firstly, this day and age I think if it is NOT possible to reproduce and recognize in the sim, most Air-framers have a training OR a design problem.
Agree, the sim is not the aircraft, but civilian use have strict limitations as opposed to mil. ( Mind you we also have to know and avoid the stall) .
Think 737-800 vs P8 Poseidon.
Remember
European TREs and line trainers has possible never done a spin in a Cessna 172, never mind recovered a MAX from a full stall/incipient spin!!
Radical idea, not happening Sir!
Regards
Cpt B
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I would argue that depends. Having been through the flight school of the legacy airline in my country i would say they all have. Back in my time it was a few hours of spinning in a T-34, later on they switched to G-120s when the Mentors started to get serious wing-falling-off-problems. And of course, that school, until recently and now again, does sponsored abinitio training. Of course, in a modular training it might be different, as the student has to organize and take the financial hit himself (come to think of it, i had to pay myself as well, but the spin mission was simply part of the training, no getting out of it).
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Reuters - MARCH 21, 2019 / 9:36 PM ET
American Airline pilots expect to test 737 MAX software fix in Boeing simulator
https://www.reuters.com/article/us-e...-idUSKCN1R306I
American Airline pilots expect to test 737 MAX software fix in Boeing simulator
https://www.reuters.com/article/us-e...-idUSKCN1R306I
That is like test flying or test firing where all tests are always done in optimal conditions. => The "accidental" hardware failures can never be simulated.
I remember a brand new Air to air missile. => 100 test firings gave 98% successful launches. WHAW, what a GREAT result.
In operations and almost ALL failed. => When the missiles had a few flights behind it, the wingtip vibrations and "G" forces had broken the missiles internally in multiple ways.
Back to BASICS => You can NEVER solve a HARDWARE issue with a SOFTWARE update.
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How about a case where the pilots, after having been trained about the perils of spurious MCAS activations, would get an airspeed indication failure (unreliable airspeed) followed by real stall warning (generated by the AOA vane), and a justified MCAS activation, but that they would misinterpret as a spurious MCAS activation. They would do the runaway trim drill, meaning trim against the down stab, and turn off the stabilizer switches and pull on the stick.
Would they be able to recover from the stall that would follow ?
quote:
I'm beginning to picture this scenario:
- * you have a malfunctioning AOA sensor, which basically by random misfortune happens to be the one feeding STS and MCAS for this flight (the other one works just fine, but is being ignored)
* you get no warning of the failure, because your cheap-o third-world airline did not purchase the AOA disagree warning option
* instead, you get stick shaker and stall warning
* so you push a bit of nose down (and perhaps add a little thrust) to build a safety speed margin above an airspeed you're suddenly no longer sure about
* MCAS - which you may or may not know about, certainly not through reading the FCOM - silently kicks in and gives you 2.5°/sec of nose down trim for 10 seconds - speed increases quickly
* you may have noticed - amid the cacophony of alarms, perhaps while trying to run an unreliable airspeed checklist - the uncommanded trim movement, but then it stops on its own - so no, this is not a runaway stab trim occurence
* you pull back on the yoke to avoid overspeeding, and probably trim nose up to alleviate the effort - but not for a full 10 seconds: stab trim is still nose down and speed is not back down to where it started
* after 10 seconds MCAS is back in action, and gives you another 10 seconds of nose down trim - speed increases further
* you're now pulling back on the yoke with all your might, but blowback kicks in and despite your best efforts the elevator looses authority
At this point you have just one chance of living through the day by executing this exact sequence of actions:
1) do not heed the backseater pilot deadheading on the jump seat behind you, yelling to cutoff stab trim! At least not yet: if you do, you will not have enough elevator authority to climb out of the dive you're currently in; you need electric trim because hand cranking the manual trim wheel will not be fast enough, and you need both hands to apply as much nose up elevator as you can in the meanwhile
2) use electric trim switch to trim nose up and continue to pull back on the yoke (something they taught you since PPL should not be done: first stick, then trim)
3) if you aren't a smoking hole in the ground by now, get speed under control and back to level flight eventually
4) NOW you must cutoff the stab trim to avoid riding the rollercoaster again
Creepy, and sobering
unquote:
as I am only rated on airbus I cannot comment but this scenario makes a lot of sense to me.
if it happened somehow like this 95% of us superpilots could have been caught in this trap.
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Did Boeing make AoA disagree an extra-cost option on the MAX because it's not available on the NG, and therefore if it was standard on the MAX it would reduce cockpit commonality, make the "it's just the same as an NG, no training required" argument less convincing?
Oh, and are you suggesting that they go fly the fix on the real aircraft before they've rung it out in the sim?
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Hello, good morning, good afternoon, and HOW STUPID are they actually? ? ? In a simm??
That is like test flying or test firing where all tests are always done in optimal conditions. => The "accidental" hardware failures can never be simulated.
I remember a brand new Air to air missile. => 100 test firings gave 98% successful launches. WHAW, what a GREAT result.
In operations and almost ALL failed. => When the missiles had a few flights behind it, the wingtip vibrations and "G" forces had broken the missiles internally in multiple ways.
Back to BASICS => You can NEVER solve a HARDWARE issue with a SOFTWARE update.
That is like test flying or test firing where all tests are always done in optimal conditions. => The "accidental" hardware failures can never be simulated.
I remember a brand new Air to air missile. => 100 test firings gave 98% successful launches. WHAW, what a GREAT result.
In operations and almost ALL failed. => When the missiles had a few flights behind it, the wingtip vibrations and "G" forces had broken the missiles internally in multiple ways.
Back to BASICS => You can NEVER solve a HARDWARE issue with a SOFTWARE update.
"...one APA pilot and one pilot from American’s management team would test the software fix in Renton, Washington, where Boeing builds the MAX and has two simulators."
Those would be Boeings engineering sims (I've been in them). There is a vast difference between them and the average Level D crew training simulator. Completely different equipment for completely different purposes.
An engineering simulator is a good and safe place to start testing effectiveness and failure modes.
But, nothing replaces actual flight test. You can be absolutely sure that Boeing will complete flight tests to clear whatever MCAS fix is to be implemented.
But, nothing replaces actual flight test. You can be absolutely sure that Boeing will complete flight tests to clear whatever MCAS fix is to be implemented.
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(Not a pilot) THY1951 had a faulty radio altimeter antenna that gave a valid but incorrect value. That single input caused the autothrottle logic to throttle down the engines. Were there any subsequent changes in logic, or did Boeing just reiterate that crew should monitor airspeed?
Now, one duff sensor apparently affects all manner of instruments and systems, and it sounds as if Boeing hope that an indicator light and a conflict warning will be the fix, and an existing trim procedure will work in this new case if the worst happens.
I imagine similar examples exist for weight-on-wheels sensors, the reverse-thrust system, and many more that I cannot conceive.
If I am being fair in the above, will the aviation world allow Boeing to continue this apparent philosophy of simple inputs, simple logic, and an aeroplane arguably simple to fly in manual mode when some part of the above fails? Will they be forced to make a more "foolproof" 'plane?
Now, one duff sensor apparently affects all manner of instruments and systems, and it sounds as if Boeing hope that an indicator light and a conflict warning will be the fix, and an existing trim procedure will work in this new case if the worst happens.
I imagine similar examples exist for weight-on-wheels sensors, the reverse-thrust system, and many more that I cannot conceive.
If I am being fair in the above, will the aviation world allow Boeing to continue this apparent philosophy of simple inputs, simple logic, and an aeroplane arguably simple to fly in manual mode when some part of the above fails? Will they be forced to make a more "foolproof" 'plane?
Last edited by fotoguzzi; 23rd Mar 2019 at 04:05. Reason: comma
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It was available on the NG, flew quite a few of them equipped with the AOA DISAGREE option installed. But apparently, it was a customer option for the NG as well, not standard equipment.
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I am also absolutely sure that Boeing conducted test flights to check and validate the current MCAS solution also.
I am also aware that, for completely different reasons, they chose to not include it in the "conversion" and line training requirements and crew documentation (until AFTER the Lion Air crash) and thus the "MCAS fault" scenario does not appear in the (few) Level D crew training simulators that are currently in service.
There's something fundamentally wrong here. The AoA sensors on the Max are failing. They are normally very reliable - I've never seen one fail in about 10,000 hours of flying aircraft with the same sensors. What you do notice while doing the walk around check is that they are fully deflected up if reverse thrust was used on the previous landing. The Max has engines moved far forward of the original position. Perhaps the sensors are being damaged by use of reverse thrust.