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Hans...
"And where did I say the pilots should have controlled the aircraft with trim??? I said they didn't trim while having to pull with all their force to control the aircraft for several minutes..."
You didn't... Boeing controls the AC with Trim....in this case, mysteriously, and with fatal results. It is Boeng controlling with Stabiliser "Trim". Calling the HS a trimming device is an invitation to disaster,
qed
"And where did I say the pilots should have controlled the aircraft with trim??? I said they didn't trim while having to pull with all their force to control the aircraft for several minutes..."
You didn't... Boeing controls the AC with Trim....in this case, mysteriously, and with fatal results. It is Boeng controlling with Stabiliser "Trim". Calling the HS a trimming device is an invitation to disaster,
qed
Ah, I misread what you meant.
But every air transport plane out there for the 7 decades has used the elevator for control, and the HS for trim. And every manufacturer has increased the amount of controlling the aircraft does for you behind the scenes. I fly the bus, and haven't trimmed myself in 12 years, outside of the SIM. I would definitely call what Airbus does controlling the aircraft with trim/HS.
The design of MCAS was a disaster. The fatal results were also because of the pilots.
3 minutes of having to trim ANU in the first 10 minutes of flight is not mysterious. It's a very clear indicator that switching of the trim would help.
Switching of the electric trim after the aircraft is out of trim, even though you were able to trim the force off before is also not good enough.
Last edited by hans brinker; 15th Jun 2024 at 17:45.
Hans...
"Switching off the electric trim after the aircraft is out of trim, even though you were able to trim the force off before is also not good enough."
Agreed. Reading QRH takes both eyes and both hands. Flying takes two eyes and two hands. Turning ninety degrees and finding the trim motor switches takes two eyes and two hands.
Back to a third pilot?
Any trimmed condition that cannot be overcome by flight controls swiftly should be prohibited ....imo
Quote Multi
Agreed. Reading QRH takes both eyes and both hands. Flying takes two eyes and two hands. Turning ninety degrees and finding the trim motor switches takes two eyes and two hands.
Back to a third pilot?
Any trimmed condition that cannot be overcome by flight controls swiftly should be prohibited ....imo
Quote Multi
And to alleviate emphatic NU Pitch caused by more powerful engines, which were also moved forward of prior engine placement to clear the wing...
The issue was that - at very high angles of attack (i.e. near stall) - the additional lift generated by the larger, further forward engine nacelles on the MAX reduced the control forces needed to pull up. This is contrary to a FAR/CS that required increasing the pitch require increased control forces. Various aerodynamic fixes were tried, but didn't have the desired effect. MCAS, OTOH, by trimming the stab, created the desired increase in control forces.
After the grounding, it was proposed by the Canadian CAA that Boeing simply get rid of MCAS entirely, and obtain an exemption to the relevant FAR, then address the controllability effect with training. Personally, I rather liked this option, but reportedly the FAA and EASA were rather less thrilled by that option.
Last edited by Saab Dastard; 15th Jun 2024 at 18:24. Reason: Removed response to personal insults
Not quite. MCAS was unrelated to the engine thrust induced patch-up from the engines (which, BTW, are similar thrust levels to those on the 737NG).
The issue was that - at very high angles of attack (i.e. near stall) - the additional lift generated by the larger, further forward engine nacelles on the MAX reduced the control forces needed to pull up. This is contrary to a FAR/CS that required increasing the pitch require increased control forces. Various aerodynamic fixes were tried, but didn't have the desired effect. MCAS, OTOH, by trimming the stab, created the desired increase in control forces.
After the grounding, it was proposed by the Canadian CAA that Boeing simply get rid of MCAS entirely, and obtain an exemption to the relevant FAR, then address the controllability effect with training. Personally, I rather liked this option, but reportedly the FAA and EASA were rather less thrilled by that option.
The issue was that - at very high angles of attack (i.e. near stall) - the additional lift generated by the larger, further forward engine nacelles on the MAX reduced the control forces needed to pull up. This is contrary to a FAR/CS that required increasing the pitch require increased control forces. Various aerodynamic fixes were tried, but didn't have the desired effect. MCAS, OTOH, by trimming the stab, created the desired increase in control forces.
After the grounding, it was proposed by the Canadian CAA that Boeing simply get rid of MCAS entirely, and obtain an exemption to the relevant FAR, then address the controllability effect with training. Personally, I rather liked this option, but reportedly the FAA and EASA were rather less thrilled by that option.
Waive certification rules? Like EASA waived airframe cues at Stall for Airbus?
{Pitch stability at stall, no nose down?)
MCAS NG to MAX
Not quite. MCAS was unrelated to the engine thrust induced patch-up from the engines (which, BTW, are similar thrust levels to those on the 737NG).
The issue was that - at very high angles of attack (i.e. near stall) - the additional lift generated by the larger, further forward engine nacelles on the MAX reduced the control forces needed to pull up. This is contrary to a FAR/CS that required increasing the pitch require increased control forces. Various aerodynamic fixes were tried, but didn't have the desired effect. MCAS, OTOH, by trimming the stab, created the desired increase in control forces.
After the grounding, it was proposed by the Canadian CAA that Boeing simply get rid of MCAS entirely, and obtain an exemption to the relevant FAR, then address the controllability effect with training. Personally, I rather liked this option, but reportedly the FAA and EASA were rather less thrilled by that option.
The issue was that - at very high angles of attack (i.e. near stall) - the additional lift generated by the larger, further forward engine nacelles on the MAX reduced the control forces needed to pull up. This is contrary to a FAR/CS that required increasing the pitch require increased control forces. Various aerodynamic fixes were tried, but didn't have the desired effect. MCAS, OTOH, by trimming the stab, created the desired increase in control forces.
After the grounding, it was proposed by the Canadian CAA that Boeing simply get rid of MCAS entirely, and obtain an exemption to the relevant FAR, then address the controllability effect with training. Personally, I rather liked this option, but reportedly the FAA and EASA were rather less thrilled by that option.
So, yeah, the genie is out of the bottle. Center of Lift moves forward in pitch and you better be ready to apply positive stick to manage it. Boeing knew that would happen 10 years ago. My sense is that everybody is training to that reality even if it's not what the book says. MCAS was an inadequate remedy.
From dodgy PA announcements to hydraulic leaks, this has not been a the best of weeks for the 777
The dodgy PA announcement is weird to say the least.
https://simpleflying.com/united-airl...-announcement/
The dodgy PA announcement is weird to say the least.
https://simpleflying.com/united-airl...-announcement/
Not quite. MCAS was unrelated to the engine thrust induced patch-up from the engines (which, BTW, are similar thrust levels to those on the 737NG).
The issue was that - at very high angles of attack (i.e. near stall) - the additional lift generated by the larger, further forward engine nacelles on the MAX reduced the control forces needed to pull up. This is contrary to a FAR/CS that required increasing the pitch require increased control forces. Various aerodynamic fixes were tried, but didn't have the desired effect. MCAS, OTOH, by trimming the stab, created the desired increase in control forces.
After the grounding, it was proposed by the Canadian CAA that Boeing simply get rid of MCAS entirely, and obtain an exemption to the relevant FAR, then address the controllability effect with training. Personally, I rather liked this option, but reportedly the FAA and EASA were rather less thrilled by that option.
The issue was that - at very high angles of attack (i.e. near stall) - the additional lift generated by the larger, further forward engine nacelles on the MAX reduced the control forces needed to pull up. This is contrary to a FAR/CS that required increasing the pitch require increased control forces. Various aerodynamic fixes were tried, but didn't have the desired effect. MCAS, OTOH, by trimming the stab, created the desired increase in control forces.
After the grounding, it was proposed by the Canadian CAA that Boeing simply get rid of MCAS entirely, and obtain an exemption to the relevant FAR, then address the controllability effect with training. Personally, I rather liked this option, but reportedly the FAA and EASA were rather less thrilled by that option.
I even suspect it could, paradoxically, be easier.
If you feel your airplane suddenly going nose-up while at stall, you might feel a very strong desire to counter this rotation by pushing full forward. Which is exactly what you have to do.
Ah, I misread what you meant.
But every air transport plane out there for the 7 decades has used the elevator for control, and the HS for trim. And every manufacturer has increased the amount of controlling the aircraft does for you behind the scenes. I fly the bus, and haven't trimmed myself in 12 years, outside of the SIM. I would definitely call what Airbus does controlling the aircraft with trim/HS.
The design of MCAS was a disaster. The fatal results were also because of the pilots.
3 minutes of having to trim ANU in the first 10 minutes of flight is not mysterious. It's a very clear indicator that switching of the trim would help.
Switching of the electric trim after the aircraft is out of trim, even though you were able to trim the force off before is also not good enough.
But every air transport plane out there for the 7 decades has used the elevator for control, and the HS for trim. And every manufacturer has increased the amount of controlling the aircraft does for you behind the scenes. I fly the bus, and haven't trimmed myself in 12 years, outside of the SIM. I would definitely call what Airbus does controlling the aircraft with trim/HS.
The design of MCAS was a disaster. The fatal results were also because of the pilots.
3 minutes of having to trim ANU in the first 10 minutes of flight is not mysterious. It's a very clear indicator that switching of the trim would help.
Switching of the electric trim after the aircraft is out of trim, even though you were able to trim the force off before is also not good enough.
If the control system is easily overriden by the trim, then the trim becomes the real control system, and the main controls become the trim. The roles are reverted.
Having now flown both airbus and boeing, I really don't understand the concept of having a speed stability on an airliner with a flight control law. The entire point of the flight control law should be to make the pilot's job easier. Removing the trim does make it easier.
Then, the defects added by airbus are easily corrected. An airplane should not be allowed, able to trim itself below maneuvering speed. With a THS position that gives an equilibrium speed below maneuvering speed. So in airbus talks it shouldn't go below VLS. It shouldn't go above max speed as well.
Then, there should be a very conspicuous trim indicator.
To finish with, the manufacturer should introduce an emergency "untrim" button, that would unsurprisingly be located next to the previous indicator, and which would reset the stabilizer position to a neutral position that allows flight at all masses, centers of gravity, and flaps/gear configurations.
This would have prevented AF447, it would have allowed XL airways 888 to survive, and maybe some others.
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Originally Posted by CVividasku
I'm pretty sure the pilots would be more than able to deal with this.
I even suspect it could, paradoxically, be easier.
If you feel your airplane suddenly going nose-up while at stall, you might feel a very strong desire to counter this rotation by pushing full forward. Which is exactly what you have to do.
I even suspect it could, paradoxically, be easier.
If you feel your airplane suddenly going nose-up while at stall, you might feel a very strong desire to counter this rotation by pushing full forward. Which is exactly what you have to do.
Stability is designed-into an aircraft for a reason.
Originally Posted by Bonnielass
From dodgy PA announcements to hydraulic leaks, this has not been a the best of weeks for the 777
AF447 was deep into the stall, which the pilots hadn’t recognised. And when they did recognise it, they were so far in the system gave them conflicting information when they tried to get out of it.
it’s the same with MCAS. If Boeing had been more forthcoming with information about it airlines could have trained for it and its failure modes. They weren’t and the airlines didn’t. The results are well known and Boeing deserves everything it gets in my opinion.
As for the THS, every pilot flying big jets should have it drilled in to them that’s it’s the most powerful control surface on the aircraft, and should be respected as such.
Pegase Driver
@CVividasku
the trimming system should not be more powerful than the control system..
A personal anecdote from years back. Towing gliders for years on Socata Rallyes and Robins DR400, Simples trims. you can dive rapidly and easily after release on both not having to touch the trim much .Our club bought a Super Cub to reduce the towing costs especially for aerobatics towing ( 4-5000Ft) it has a moving horizontal stab trim , ok, read the POH, nothing special mentionned.in there . I had previous recreational experience on standard PA18 with 100 HP .never had trim issues. On my first acrobatic high tow, after release want to dive down but a rather strong force is needed on the stick, so I trim ND to be able to reach a good rate of descend, keeping a bit of RPM to keep engine warm ,(standard towing procedure) speed and ROD increases, but still on the yellow arc at 2000 Ft time to start to level off and then the force on control is too hard ,I turn back the trim ANU ,but very high forces needed to turn the trim handle but it turns eventually however nothing happens, Had to flip the aircraft in a sharp 7--80 degrees turn to lift the nose up using the rudder to break the dive and save the day. Big discussion afterwards,
Learned that when too strong force is on the Horizontal stab , the cable supposed to move it just glides around the pulley of the trim handle in the cockpit. Basically once you pass a certain speed you can't trim back . Nothing in the POH , and not mentioned on the (basic) type rating training I received either. OK this was GA, not Airline ops.
Last edited by ATC Watcher; 17th Jun 2024 at 10:33. Reason: typo
And airbus planes are not stable as in the conventional definition of stability.
I don’t think either of those would have survived had they had the system you suggest.
AF447 was deep into the stall, which the pilots hadn’t recognised. And when they did recognise it, they were so far in the system gave them conflicting information when they tried to get out of it.
AF447 was deep into the stall, which the pilots hadn’t recognised. And when they did recognise it, they were so far in the system gave them conflicting information when they tried to get out of it.
Airbus system trimmed the THS all the way up, for both cases.
For the XL case, the pilot was pushing full forward, and it wasn't enough to keep the nose from going up quickly.
My suggestion is to prevent the THS from trimming itself so far nose up.
And to include an emergency button that could be used in upset situations, to reset the THS.
Any of these two would have saved for sure the XL plane.
As for the 447 case, had the trim stopped trimming to nose up, the pilot would have had to pull constantly to increase AOA at a stall. He would have had a very clear cue that this was a low speed stall and not a high speed one.
Then, deep into the stall, I can't say for sure that pushing the "trim reset" button would magically make the airplane go out of the stall, but it surely would be huge help.
The first system modification would have been more useful in the first place.
I thought so too. but modern airliners are not unique in this. the good old PA-18 has this feature too and it can bite you hard too .
And the PA18 is a very old airplane that's rarely flown today.
If you look at modern planes used for training, such as the DA40, DA42, you can fly at cruise speed with trim at stall speed and conversely. I tried it with no problem whatsoever. Next time I do it, I will bring a device to measure force and have figures to support my discourse.
What I can say objectively however is that two fingers were enough to counter the force in both cases. Whereas if a boeing airplane is out of trim, you will firmly grip both hands on the control wheel, and maybe sometime involuntarily press the PTT button.
The experience that you describe is frightening, and it just shows very nicely that the PA18 is a very old airplane that can't meet today's safety standard, except if this type of problem would be corrected.
My suggestion is to prevent the THS from trimming itself so far nose up.
And to include an emergency button that could be used in upset situations, to reset the THS.
Any of these two would have saved for sure the XL plane.
As for the 447 case, had the trim stopped trimming to nose up, the pilot would have had to pull constantly to increase AOA at a stall. He would have had a very clear cue that this was a low speed stall and not a high speed one.
Then, deep into the stall, I can't say for sure that pushing the "trim reset" button would magically make the airplane go out of the stall
And to include an emergency button that could be used in upset situations, to reset the THS.
Any of these two would have saved for sure the XL plane.
As for the 447 case, had the trim stopped trimming to nose up, the pilot would have had to pull constantly to increase AOA at a stall. He would have had a very clear cue that this was a low speed stall and not a high speed one.
Then, deep into the stall, I can't say for sure that pushing the "trim reset" button would magically make the airplane go out of the stall
I’ve added bold to your quote because that’s exactly what the FO did!
In the case of AF447 it trimmed full nose up because the pilot held full back stick pretty much for the entire duration. And I can say with certainty it takes quite a lot of effort to hold full back stick against the spring.
My point is, if they didn’t recognise the issue enough to release the full back stick then they certainly wouldn’t have recognised it enough to reset the stab trim.
Notice recent Boeing/FAA fireworks to try and drag Airbus into this self-made mess.
Boeing can begin to start the decade it will take to reinvent themselves now; Airbus never had to start so are just waltzing away with superior aircraft. And COMAC are literally laughing at Boeing’s ability to throw the baton under their own wheels. Repeatedly. With the help of the FAA.
The future is A, C, B.
Boeing can begin to start the decade it will take to reinvent themselves now; Airbus never had to start so are just waltzing away with superior aircraft. And COMAC are literally laughing at Boeing’s ability to throw the baton under their own wheels. Repeatedly. With the help of the FAA.
The future is A, C, B.
It was China.
And it apparently went on for four years before anyone noticed (BTW, still not seen anything about how/why this was discovered - that could prove interesting as well). Add that to a long list of fake/contaminated products they've sent to the west over the years (knew someone who's dog died from the poisoned dog food they sent our way - she now studies labels religiously, and if she can't find what's she's looking for that wasn't make in China, she simply does without).
You still want to trust your life to a COMAC jet? You really think their domestic stuff is any better?
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Wall Street Journal reporting on its website (June 17) on certain aspects of the Department of Justice decision, still pending, about the Deferred Prosecution Agreement in the criminal case proceeding in a U.S. District Court in Texas. The headline: "Inside DOJ's Wrenching Decision on Whether to Prosecute Boeing."
The article is an overview of significant parts of the 737 MAX saga, covering many of the central events, albeit in a general way (for those who have followed the saga closely, one might say "in a superficial way"). Regardless, as the headline suggests, the reporting does take the reader into the deliberations inside DOJ for a decision on what to do about the DPA in the aftermath of the Alaska door-plug incident.
The article - as an SLF/attorney I thought this was a little surprising - does not mention the decision by a federal appellate court which required the court proceedings to give the crash victims' families the opportunity to express their views on the DPA. It does describe their meeting with the official at DOJ reportedly making the decision about the DPA.
The article is an overview of significant parts of the 737 MAX saga, covering many of the central events, albeit in a general way (for those who have followed the saga closely, one might say "in a superficial way"). Regardless, as the headline suggests, the reporting does take the reader into the deliberations inside DOJ for a decision on what to do about the DPA in the aftermath of the Alaska door-plug incident.
The article - as an SLF/attorney I thought this was a little surprising - does not mention the decision by a federal appellate court which required the court proceedings to give the crash victims' families the opportunity to express their views on the DPA. It does describe their meeting with the official at DOJ reportedly making the decision about the DPA.
This entry by Big Pistons Forever, Latest Boeing News suggests corrosion was the first clue.
Geeze….looking at Space News it seems Boeing can’t catch a break. Not good when your “Starliner Spacecraft” has Helium leaks due to faulty valves and seals. Especially when launch was delayed to supposedly fix the problem.
Pulled up 400 ft from the ocean ? I think Boeing have been exceptionally fortunate with this. If an accident had ensued, yet again with pitch control on the Max, something which MCAS was meant to manage, it could have been curtains for the programme. Yes, we could all have technical discussions here about the differences, but another out-of-control Max into the ocean could be just the step too far.
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FO reports his push was "inadvertent" (accidental).
MCAS is not designed to deal with this situation.
Any nose down is not tolerated, it would seem allowing the nose to raise at this point in any fashion would be a good thing. Turns out the A/C climbed too high anyway. Something is not jiving.
MCAS is not designed to deal with this situation.
Any nose down is not tolerated, it would seem allowing the nose to raise at this point in any fashion would be a good thing. Turns out the A/C climbed too high anyway. Something is not jiving.