The 737max disaster!

[SirGalahad]

That wasn't what I asked about, though.

Is the plane unflyable without MCAS?
If not inherently so, was it just the cost of proper training that made MCAS the chosen "solution"?

As I pointed above it needed MCAS for its type rating.

You can fly it without MCAS its not inherently unstable but then you would need to retrain using simulators of which there is only one in North America.

But then you would need to certify the new plane, the training etc which would take more time and cost than trying to retrofit a solution.

 

[bernardgreen]

The thing that cncerns me is that the MCAS can rotate the jack screw of the stabilisor at high speed ( as shown by the rapid rotation of the trim wheel in the cock pit ) yet even with the MCAS disabled ( electrical supply to jack screw motor Cut Off ) it requires almost super human effort from the pilots to rotate the trim wheel.

 

[fillyboy]

Can a technical modification be that difficult? In the many Triumph Spitfires I drove in my youth, I always had a sack of potatoes in the boot, appalling rear suspension design.

 

[durhamplumber]

requires almost super human effort from the pilots to rotate the trim wheel.

Not at all..it is just slow..difficult if plane is in a dive

 

[durhamplumber]

Can a technical modification be that difficult? In the many Triumph Spitfires I drove in my youth, I always had a sack of potatoes in the boot, appalling rear suspension design.

737 Tad more complex old bean.As shown by the crashes, tech mods are a bit tricky!!!

 

[bernardgreen]

Not at all..it is just slow

Pilots have said that the trim wheel can require a lot of effort, sometimes from both pilots, to recover from "trim runaway" Trim runaway is a rapid movement of the stabiliser to nose up or nose down due to an "error" from the automated systems.

When flying manually the frequent and very small changes to trim that are necessary in normal flight can be made by one hand on the rim of the trim wheel. On autopilot these trim alterations are performed automatical.

difficult if plane is in a dive

Manual trimming requires more physical effort when the stabiliser is deflecting the plane from normal level flight as the pilots then have to over come the high aero-dynamic forces exerted on the stabiliser. This situation should never happen but when it does the trim wheel has fold out cranks to enable the pilot(s) to exert more force.

The MCAS system moved the stabiliser to an angle where the aero-dynamic force was too high for the pilots to crank the trim wheel enough turns to remove the nose down before the impact with sea / land. Had it happened at 30,000 feet then the pilots might have had time to turn the trim wheel enough times to remove the nose down

 

[motorbiking]

The solution is to have 3 sensors and use a closest 2 comparison. That way you need 2 sensor failures before MCAS will push you in to the ground.

 

[Doug99]

The solution is to have 3 sensors and use a closest 2 comparison. That way you need 2 sensor failures before MCAS will push you in to the ground.

In addition to the above, any sensor should fail 'safe' ie the manual control of the plane by the pilot is not compromised.
Even if all sensors fail, the pilot should still be able to fly the plane.

 

[durhamplumber]

Pilots have said that the trim wheel can require a lot of effort, sometimes from both pilots, to recover from "trim runaway" Trim runaway is a rapid movement of the stabiliser to nose up or nose down due to an "error" from the automated systems.

When flying manually the frequent and very small changes to trim that are necessary in normal flight can be made by one hand on the rim of the trim wheel. On autopilot these trim alterations are performed automatical.



Manual trimming requires more physical effort when the stabiliser is deflecting the plane from normal level flight as the pilots then have to over come the high aero-dynamic forces exerted on the stabiliser. This situation should never happen but when it does the trim wheel has fold out cranks to enable the pilot(s) to exert more force.

The MCAS system moved the stabiliser to an angle where the aero-dynamic force was too high for the pilots to crank the trim wheel enough turns to remove the nose down before the impact with sea / land. Had it happened at 30,000 feet then the pilots might have had time to turn the trim wheel enough times to remove the nose down

As I said...more effort required if not in level flight.simple aerodynamics.

 

[bernardgreen]

.simple aerodynamics.

I cannot understand the logic behind the decision to move the pivot point of the horisontal stabiliser from the leading edge to the trailing edge.

With the pivot point at or near the leading edge the stabiliser air flow will try push the stabilisier back towards the neutral position. Force has to be applied to move it to create nose up or nose down when that is required.

With the pivot point at or near the trailing edge once the stabiliser is out of the neutral position force has to be applied to prevent the air flow pushing the control surface further and creating a steeper descent ( nose down ) or climb ( nose up ). This force has to be applied by the pilots if the electric motor has been switched off.

 

[Harry Bloomfield]

The MCAS system moved the stabiliser to an angle where the aero-dynamic force was too high for the pilots to crank the trim wheel enough turns to remove the nose down before the impact with sea / land. Had it happened at 30,000 feet then the pilots might have had time to turn the trim wheel enough times to remove the nose down

What I saw, suggested the motorised system under automated control could rapidly change the trim, yet a pilot would need to put in numerous turns under manual control, once he had thrown the isolation switches. The obvious to me solution, is to have witch to isolate the automatic control and give the pilot direct control of the trim actuator motors.

 

[durhamplumber]

Let's hope Boeing never goes into the driverless car business!

In fairness,they have produced some fantastic aircraft with great safety records,but mistakes happen...No one is perfect LaL.

 

[SirGalahad]

The problem with the 737 Max was it was an iteration too far trying to keep up with the far more advanced A320. They had to raise the landing gear and push the engines slightly forward to accomodate the larger and more efficient engines. This then changed the flying characteristics of the plane, which isn't a problem - you would then need to certify the place and retrain all the pilots are great expense and time.

Their fix to meet the same type rating as the previous 737 was MCAS - a disaster waiting to happen. It's why they made it difficult to turn it off.

https://www.seattletimes.com/busine...ax-cockpit-limiting-ability-to-shut-off-mcas/

 

[EddieM]

More aeronautical engineering experts on here than could be believed.

 

[durhamplumber]

More aeronautical engineering experts on here than could be believed.

Indeed..Boeing know f all.!