MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures
" Defence News reported earlier this year (2018) that the US Army had stopped taking deliveries of the AH-64E Apache attach helicopters from Boeing in February. The US Army explained that 'the service is not confident in the durability of what it deems a "critical safety item" - a strap pack nut that holds very large bolts, that subsequently hold the rotor blades on the helicopter'
(snip)
(snip)
Plus: that's Boeing Mesa, Rotary Wing.
Ryanair are supposedly considering Airbus as well though long term committed Boeing customers may find it worthwhile to stick with Boeing and drive very hard on price whilst being number one in the queue for the new narrow body MAX replacement when it arrives. A clean sheet design would probably outperform the A320NEO so Airbus might get into an arms race with Boeing to build an even better A320 replacement, something both companies have tried to avoid.
Of course it could just be a bargaining position. Airbus didn't bother talking to British Airways for years as they felt they were wasting their time and were simply being used to help BA get a better price from Boeing. When BA first bought Airbus aircraft they had to go to Toulouse and convince the sales department that they were serious.
Of course it could just be a bargaining position. Airbus didn't bother talking to British Airways for years as they felt they were wasting their time and were simply being used to help BA get a better price from Boeing. When BA first bought Airbus aircraft they had to go to Toulouse and convince the sales department that they were serious.
Only half a speed-brake
I think the problem is the efficiency sought.
- 737NG already has CFD wing
- the new engines are same for both
- fuselage won't add up to much, the tail has already been tweaked thrice.
So you can do weight.
- But a composite hull (787) for a shorthaul a/c needs to take a lot of beating on the ramp. Also the aftermarket needs aftermarket repairs, availability of both affects the sales price. Sales price needs to cover the development cost and here the two go against each other.
- go fly-by-light, all electric FCS. Sadly the recent even shows Boeing and their ecosystem do not have the skills to achieve that, present day.
- a plethora of unspecified small improvements. Which are also available to Airbus on their current airframe, hmm.
So all new airframe then, once materials and technologies that are not available now become suitable for mass production and field deployment. At the same time when 320NEO is becoming obsolete, not sooner.
my 2pc.
Last edited by FlightDetent; 14th Aug 2019 at 08:20.
Just how long do you think that would take to bring to the market?
Join Date: Feb 2013
Location: Gloucestershire, UK
Posts: 34
Likes: 0
Received 0 Likes
on
0 Posts
'TUI says that the grounding of the Boeing 737 Max will cost the holiday group €300m. It said: "Resumption of the 737MAX remains subject to the clearance decision of the civil aviation authorities and we have secured replacement aircraft leases out to the end of our Summer 2019 programme." The company made the disclosure in its third quarter results where it reported a 3.7% rise in sales to €4.7bn. Pre-tax profits, however dropped by 58.2% to €58.9m.'
https://www.theguardian.com/business...-to-300m-euros
This is good news because it seems to me that the only thing the aviation industry and its customers (right down to SLF) really cares about is money and therefore if the Max catastrophe costs everyone concerned a lot of money perhaps safety will claw its way back up the agenda towards its rightful position. Perhaps. Maybe. I am SLF on a flight this morning at a ludicrously low fare (less than a meal in an average restaurant), using an elderly turboprop on a shuttle island-hop, and I do wonder....
https://www.theguardian.com/business...-to-300m-euros
This is good news because it seems to me that the only thing the aviation industry and its customers (right down to SLF) really cares about is money and therefore if the Max catastrophe costs everyone concerned a lot of money perhaps safety will claw its way back up the agenda towards its rightful position. Perhaps. Maybe. I am SLF on a flight this morning at a ludicrously low fare (less than a meal in an average restaurant), using an elderly turboprop on a shuttle island-hop, and I do wonder....
Maninthebar, #1832 not known; the background is in the EASA reference below.
“Simulation has demonstrated that the thumb switch trim does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope,”
“The trim wheel can be used to trim the airplane throughout the entire flight envelope. In addition, the autopilot has the authority to trim the airplane in these conditions.
The reference regulation and policy do not specify the method of trim, nor do they state that when multiple pilot trim control paths exist that they must each independently be able to trim the airplane throughout the flight envelope.”
“The main issue being that longitudinal trim cannot be achieved throughout the flight envelope using thumb switch trim only.
…
Boeing set the thumb switch limits in order to increase the level of safety for out-of-trim dive characteristics (CS 25.255(a)(1)). The resulting thumb switch limits require an alternative trim method to meet CS 25.161 trim requirements in certain corners of the operational envelope.
The need to use the trim wheel is considered unusual, as it is only required for manual flight in those corners of the envelope.”
The inference is that the stick trim switches are electrically inhibited at a particular tail position, preventing either ANU or AND movement (otherwise it would invalidate the purpose of inhibition for safety reasons - trim runaway).
Points to note: the ‘discrepancy’ was noted in simulation. ‘Authority’ or inhibited?
Apparently (significant speculation) the use of trim wheel, in simulation (as the alternative to elect trim) was restricted to the certification overspeed requirements, and not the full range of physical trim movement, or ability to manually trim over this trim range. Thus did not identify any inability to move the trim manually.
Apparently the autopilot / auto trim has the ability to trim over full range. This is ambiguous; either as required for autopilot control - stay in trim, but not manual trim cert requirements. Also, this could invalidate the safety inhibition as above - trim is still electrically enabled, and ‘if so’, and ‘if’ MCAS was routed via the ‘auto’ FCC, then it could electrically signal the tail to move in conditions which the stick trim could not.
Reference to ‘aisle stand trim switches’ is confusing, perhaps trim wheel.
https://www.easa.europa.eu/sites/def...20ISS%2010.pdf Page 15
“Simulation has demonstrated that the thumb switch trim does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope,”
“The trim wheel can be used to trim the airplane throughout the entire flight envelope. In addition, the autopilot has the authority to trim the airplane in these conditions.
The reference regulation and policy do not specify the method of trim, nor do they state that when multiple pilot trim control paths exist that they must each independently be able to trim the airplane throughout the flight envelope.”
“The main issue being that longitudinal trim cannot be achieved throughout the flight envelope using thumb switch trim only.
…
Boeing set the thumb switch limits in order to increase the level of safety for out-of-trim dive characteristics (CS 25.255(a)(1)). The resulting thumb switch limits require an alternative trim method to meet CS 25.161 trim requirements in certain corners of the operational envelope.
The need to use the trim wheel is considered unusual, as it is only required for manual flight in those corners of the envelope.”
The inference is that the stick trim switches are electrically inhibited at a particular tail position, preventing either ANU or AND movement (otherwise it would invalidate the purpose of inhibition for safety reasons - trim runaway).
Points to note: the ‘discrepancy’ was noted in simulation. ‘Authority’ or inhibited?
Apparently (significant speculation) the use of trim wheel, in simulation (as the alternative to elect trim) was restricted to the certification overspeed requirements, and not the full range of physical trim movement, or ability to manually trim over this trim range. Thus did not identify any inability to move the trim manually.
Apparently the autopilot / auto trim has the ability to trim over full range. This is ambiguous; either as required for autopilot control - stay in trim, but not manual trim cert requirements. Also, this could invalidate the safety inhibition as above - trim is still electrically enabled, and ‘if so’, and ‘if’ MCAS was routed via the ‘auto’ FCC, then it could electrically signal the tail to move in conditions which the stick trim could not.
Reference to ‘aisle stand trim switches’ is confusing, perhaps trim wheel.
https://www.easa.europa.eu/sites/def...20ISS%2010.pdf Page 15
Apparently the autopilot / auto trim has the ability to trim over full range. This is ambiguous; either as required for autopilot control - stay in trim, but not manual trim cert requirements. Also, this could invalidate the safety inhibition as above - trim is still electrically enabled, and ‘if so’, and ‘if’ MCAS was routed via the ‘auto’ FCC, then it could electrically signal the tail to move in conditions which the stick trim could not.
Reference to ‘aisle stand trim switches’ is confusing, perhaps trim wheel.
https://www.easa.europa.eu/sites/def...20ISS%2010.pdf Page 15
So.....it COULD be that MCAS is able to trim the surface beyond the point at which the electric trim switches were inhibited.
Understood that the auto trim should not have been allowed to run that far without 'contradiction, though acknowledging that MCAS drive auto-trim drives the surface ~50% faster than the manual electric trim
Join Date: Apr 2019
Location: EDSP
Posts: 334
Likes: 0
Received 0 Likes
on
0 Posts
I guess we are beyond the "MCAS COULD" - we are pretty sure about that it does.
Having looked at the wiring diagrams it can indeed not be deduced if the only one direction of electric trim is inhibited beyond a certain deflection or both. I assumed it was only the towards mechanical limits direction. Maybe there was some input before in one of the threads but I cannot find it at the moment.
Having looked at the wiring diagrams it can indeed not be deduced if the only one direction of electric trim is inhibited beyond a certain deflection or both. I assumed it was only the towards mechanical limits direction. Maybe there was some input before in one of the threads but I cannot find it at the moment.
Dave your previous might be misinterpreted on two counts.
‘Flight envelope’ implies an in-trim condition (speed?), whereas if the more likely tech design was that the trim cutout was relative to the tail angle then the crew could encounter very high stick loads relative to that required for the aircraft to be ‘in trim’ at the actual speed.
The reports / FDR did indicate that the crew attempted to use elect trim at larger tail angles, but without movement. Unfortunately there is no indication of this being relative to any elect trim inhibition, not known (or trim direction?), nor if this was due to high mechanical loading or purely elect inhibition.
‘Flight envelope’ implies an in-trim condition (speed?), whereas if the more likely tech design was that the trim cutout was relative to the tail angle then the crew could encounter very high stick loads relative to that required for the aircraft to be ‘in trim’ at the actual speed.
The reports / FDR did indicate that the crew attempted to use elect trim at larger tail angles, but without movement. Unfortunately there is no indication of this being relative to any elect trim inhibition, not known (or trim direction?), nor if this was due to high mechanical loading or purely elect inhibition.
I probably could have worded that slightly better. How about "there's no suggestion that either crew was attempting to trim in the direction approaching the extremes of the range" ?
Join Date: Jul 2019
Location: Mass
Posts: 23
Likes: 0
Received 0 Likes
on
0 Posts
The reports / FDR did indicate that the crew attempted to use elect trim at larger tail angles, but without movement. Unfortunately there is no indication of this being relative to any elect trim inhibition, not known (or trim direction?), nor if this was due to high mechanical loading or purely elect inhibition.
The second MCAS activation at 05:40:20 moved the stab trim down to 0.4 units, its lowest point of the flight. Airspeed was just below VMO. The crew responded with MET and raised the stab trim back up to 2.3 units. The two MET blips at the end of the flight (05:43:11) raised the stab trim position from 2.1 to 2.3 units. The switch wasn't held long enough to affect more movement, but that doesn't mean it was "without" movement.
As for the question whether MET can trim up after the stabilizer is beyond the nose-down limit, or trim down after the stabilizer is beyond the nose-up limit, the schematics posted by Yoko1 on June 28 suggest they can (sorry, but I don't seem to be able to reproduce them here b/c I'm still new). The MET trim up signal goes through the stab nose up limit switch, but not the nose down limit switch. Likewise, the MET trim down signal goes through the stab nose down limit switch, but not the nose up limit switch. So, for example, the stabilizer being beyond the nose down limit should have no effect on MET trim up signals.
Join Date: Apr 2019
Location: EDSP
Posts: 334
Likes: 0
Received 0 Likes
on
0 Posts
The schematics posted by the alter ego do only show that there are two seperate inputs to the eaton actuator for nose up and down electric trim end switch. Nothing is disclosed about how they are evaluated and used within the eaton assembly.
Last edited by BDAttitude; 14th Aug 2019 at 16:46.
Join Date: Jul 2019
Location: Mass
Posts: 23
Likes: 0
Received 0 Likes
on
0 Posts
It is conceivable that the Eaton motor assembly knows the position of the stabilizer (although I've seen no evidence of that). It is a lot harder to believe that Boeing would bake flight dynamics decisions (nose up and down limits and their affects on MET and FCC trim commands) into the motor. Do you have any factual basis for speculating that the Eaton motor inhibits MET signals based on stab position?
Join Date: Dec 2008
Location: PDX
Posts: 72
Likes: 0
Received 0 Likes
on
0 Posts
[Not a pilot] After STAB TRIM cutout, the Ethiopian pilots were apparently wondering why the electric trim was not working. After one minute of this, the First Officer requested permission to try manual trim, which would seem to be the handwheel. After eight seconds, he declared that it was not working.
My question: Is it possible that the Pilot in Command flipped only one STAB TRIM cutout switch thinking that it would still allow electric trim as on previous 737s?
I'm not qualified to say how MAIN ELECT and AUTO PILOT work on previous series planes, but might a scenario like this explain the wasted minute until the first officer spoke up?
My question: Is it possible that the Pilot in Command flipped only one STAB TRIM cutout switch thinking that it would still allow electric trim as on previous 737s?
I'm not qualified to say how MAIN ELECT and AUTO PILOT work on previous series planes, but might a scenario like this explain the wasted minute until the first officer spoke up?
Join Date: Jun 2019
Location: VA
Posts: 210
Likes: 0
Received 0 Likes
on
0 Posts
[Not a pilot] After STAB TRIM cutout, the Ethiopian pilots were apparently wondering why the electric trim was not working. After one minute of this, the First Officer requested permission to try manual trim, which would seem to be the handwheel. After eight seconds, he declared that it was not working.
My question: Is it possible that the Pilot in Command flipped only one STAB TRIM cutout switch thinking that it would still allow electric trim as on previous 737s?
I'm not qualified to say how MAIN ELECT and AUTO PILOT work on previous series planes, but might a scenario like this explain the wasted minute until the first officer spoke up?
My question: Is it possible that the Pilot in Command flipped only one STAB TRIM cutout switch thinking that it would still allow electric trim as on previous 737s?
I'm not qualified to say how MAIN ELECT and AUTO PILOT work on previous series planes, but might a scenario like this explain the wasted minute until the first officer spoke up?
As far as the functionality of the two switches, procedurally these switches are always used together whether on the NG or MAX and frankly I don't see this crew having either the awareness or the inclination to make this kind of distinction and diverge from procedure and use just one of the switches.
Join Date: Dec 2008
Location: PDX
Posts: 72
Likes: 0
Received 0 Likes
on
0 Posts
[Not a pilot]
I have to agree. The two hundred hour pilot did not have any decades long habit of flipping just one switch, and he was the one who threw the switches. Why the Captain was seemingly expecting manual electric still to work is a mystery, which was why I thought they may have thrown only one switch.
"At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and First-Officer confirmed stab trim cut-out."
"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."
Not sure if the handwheel would have been easier to turn a minute sooner, but CUTOUT should have been a good hint that manual electric was no longer going to work.
I have to agree. The two hundred hour pilot did not have any decades long habit of flipping just one switch, and he was the one who threw the switches. Why the Captain was seemingly expecting manual electric still to work is a mystery, which was why I thought they may have thrown only one switch.
"At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and First-Officer confirmed stab trim cut-out."
"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."
Not sure if the handwheel would have been easier to turn a minute sooner, but CUTOUT should have been a good hint that manual electric was no longer going to work.
[Not a pilot]
I have to agree. The two hundred hour pilot did not have any decades long habit of flipping just one switch, and he was the one who threw the switches. Why the Captain was seemingly expecting manual electric still to work is a mystery, which was why I thought they may have thrown only one switch.
"At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and First-Officer confirmed stab trim cut-out."
"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."
Not sure if the handwheel would have been easier to turn a minute sooner, but CUTOUT should have been a good hint that manual electric was no longer going to work.
I have to agree. The two hundred hour pilot did not have any decades long habit of flipping just one switch, and he was the one who threw the switches. Why the Captain was seemingly expecting manual electric still to work is a mystery, which was why I thought they may have thrown only one switch.
"At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and First-Officer confirmed stab trim cut-out."
"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."
Not sure if the handwheel would have been easier to turn a minute sooner, but CUTOUT should have been a good hint that manual electric was no longer going to work.
