Aren't the GTFs practically the same size?

Well they would be pretty much the same size, just a little bit lighter.

UA444 wrote:

Since the LEAP engines are so large and heavy and affected the planes center of gravity, and the GTF is scalable to different fan sizes, would the MAX be having the same issues if it had a PW GTF with a smaller diameter fan? Could this be an opening for PW to get on the MAX if Boeing is desperate to save the program?

No! the problem isn't the engines. It was the stall protection MCAS system!

strfyr51 wrote:

UA444 wrote:

Since the LEAP engines are so large and heavy and affected the planes center of gravity, and the GTF is scalable to different fan sizes, would the MAX be having the same issues if it had a PW GTF with a smaller diameter fan? Could this be an opening for PW to get on the MAX if Boeing is desperate to save the program?

No! the problem isn't the engines. It was the stall protection MCAS system!

Wasn't the MCAS install needed because the engines had to be set up higher on the pylon than previous models? So as a result, it is the engines. As the end of the day, it's a management failure to build a new design years ago instead of sitting on their hands.

It would be worse, as the GTF favours are a large fan.

TWFlyGuy wrote:

strfyr51 wrote:

UA444 wrote:

Since the LEAP engines are so large and heavy and affected the planes center of gravity, and the GTF is scalable to different fan sizes, would the MAX be having the same issues if it had a PW GTF with a smaller diameter fan? Could this be an opening for PW to get on the MAX if Boeing is desperate to save the program?

No! the problem isn't the engines. It was the stall protection MCAS system!

Wasn't the MCAS install needed because the engines had to be set up higher on the pylon than previous models? So as a result, it is the engines. As the end of the day, it's a management failure to build a new design years ago instead of sitting on their hands.

MCAS was put on the MAX to make it's handling characteristics be so similar to the NG that pilots didn't need simulator training. By doing so airlines would save money on training which ultimately makes ordering the MAX more attractive. The higher placement of the engines does increase lift during high thrust settings but they could of trained pilots to be cognizant of this and to be diligent in preventing the aircraft attitude from going out of limits of safe operating envelope. Instead they put a digital fix on a analog aircraft.

It's also needed for the lengthening, and skipping that would mean a very niche product since the CSeries is already taking away market share from the smaller versions.

What it needs is a complete redesign, or at least a full fly by wire system.

What about CG changes from the new engine position?

JohanTally wrote:

MCAS was put on the MAX to make it's handling characteristics be so similar to the NG that pilots didn't need simulator training. By doing so airlines would save money on training which ultimately makes ordering the MAX more attractive.

MCAS is a longitudinal stability enhancement. It is not for stall prevention (although indirectly it helps) or to make the MAX handle like the NG (although it does); it was introduced to counteract the non-linear lift generated by the LEAP-1B engine nacelles at high AoA and give a steady increase in stick force as the stall is approached as required by regulation.

The LEAP engine nacelles are larger and had to be mounted slightly higher and further forward from the previous NG CFM56-7 engines to give the necessary ground clearance. This new location and larger size of nacelle cause the vortex flow off the nacelle body to produce lift at high AoA. As the nacelle is ahead of the C of G, this lift causes a slight pitch-up effect (ie a reducing stick force) which could lead the pilot to inadvertently pull the yoke further aft than intended bringing the aircraft closer towards the stall. This abnormal nose-up pitching is not allowable under 14CFR §25.203(a) "Stall characteristics". Several aerodynamic solutions were introduced such as revising the leading edge stall strip and modifying the leading edge vortilons but they were insufficient to pass regulation. MCAS was therefore introduced to give an automatic nose down stabilizer input during elevated AoA when flaps are up.

Source: b737.org.uk/mcas.htm

JohanTally wrote:

TWFlyGuy wrote:

strfyr51 wrote:

No! the problem isn't the engines. It was the stall protection MCAS system!

Wasn't the MCAS install needed because the engines had to be set up higher on the pylon than previous models? So as a result, it is the engines. As the end of the day, it's a management failure to build a new design years ago instead of sitting on their hands.

MCAS was put on the MAX to make it's handling characteristics be so similar to the NG that pilots didn't need simulator training. By doing so airlines would save money on training which ultimately makes ordering the MAX more attractive. The higher placement of the engines does increase lift during high thrust settings but they could of trained pilots to be cognizant of this and to be diligent in preventing the aircraft attitude from going out of limits of safe operating envelope. Instead they put a digital fix on a analog aircraft.

But without MCAS it is though that it would be uncertified due to stick force lightening approaching a stall.

767333ER wrote:

JohanTally wrote:

TWFlyGuy wrote:

Wasn't the MCAS install needed because the engines had to be set up higher on the pylon than previous models? So as a result, it is the engines. As the end of the day, it's a management failure to build a new design years ago instead of sitting on their hands.

MCAS was put on the MAX to make it's handling characteristics be so similar to the NG that pilots didn't need simulator training. By doing so airlines would save money on training which ultimately makes ordering the MAX more attractive. The higher placement of the engines does increase lift during high thrust settings but they could of trained pilots to be cognizant of this and to be diligent in preventing the aircraft attitude from going out of limits of safe operating envelope. Instead they put a digital fix on a analog aircraft.

But without MCAS it is though that it would be uncertified due to stick force lightening approaching a stall.

To me it just seems like the training could of just emphasized that the pilot who is watching instruments keep an eye on the attitude during takeoff roll and climb out. In theory MCAS should of been a valuable aid to pilots but literally was trying to crash the aircraft when given erroneous data. Boeing should never of implemented MCAS without redundancy, which is the primary reason why modern airliners are so safe. When that Qantas A380 engine blew apart and took out the two primary hydraulic systems a third hydraulic system(redundancy) got that aircraft back on the ground safely.

JohanTally wrote:

767333ER wrote:

JohanTally wrote:

MCAS was put on the MAX to make it's handling characteristics be so similar to the NG that pilots didn't need simulator training. By doing so airlines would save money on training which ultimately makes ordering the MAX more attractive. The higher placement of the engines does increase lift during high thrust settings but they could of trained pilots to be cognizant of this and to be diligent in preventing the aircraft attitude from going out of limits of safe operating envelope. Instead they put a digital fix on a analog aircraft.

But without MCAS it is though that it would be uncertified due to stick force lightening approaching a stall.

To me it just seems like the training could of just emphasized that the pilot who is watching instruments keep an eye on the attitude during takeoff roll and climb out. In theory MCAS should of been a valuable aid to pilots but literally was trying to crash the aircraft when given erroneous data. Boeing should never of implemented MCAS without redundancy, which is the primary reason why modern airliners are so safe. When that Qantas A380 engine blew apart and took out the two primary hydraulic systems a third hydraulic system(redundancy) got that aircraft back on the ground safely.

I think seeing MCAS as a valuable aid to pilots, if implemented correctly, is not really the way to look at it. The very need for MCAS should have indicated that the design had to change fundamentally.

IIRC the A380 only has two hydraulic systems. The backup is electro-hydraulic actuators (EHAs) and electro-hydraulic backup actuators (EBHAs). Same as the A350. These are not hydraulic "systems" but actuators with their own self-contained hydraulics.

BTW it is "could have" and "should have", not "could of" and "should of". Because they "could have emphasized" and "MCAS should have been".

JohanTally wrote:

767333ER wrote:

JohanTally wrote:

MCAS was put on the MAX to make it's handling characteristics be so similar to the NG that pilots didn't need simulator training. By doing so airlines would save money on training which ultimately makes ordering the MAX more attractive. The higher placement of the engines does increase lift during high thrust settings but they could of trained pilots to be cognizant of this and to be diligent in preventing the aircraft attitude from going out of limits of safe operating envelope. Instead they put a digital fix on a analog aircraft.

But without MCAS it is though that it would be uncertified due to stick force lightening approaching a stall.

To me it just seems like the training could of just emphasized that the pilot who is watching instruments keep an eye on the attitude during takeoff roll and climb out. In theory MCAS should of been a valuable aid to pilots but literally was trying to crash the aircraft when given erroneous data. Boeing should never of implemented MCAS without redundancy, which is the primary reason why modern airliners are so safe. When that Qantas A380 engine blew apart and took out the two primary hydraulic systems a third hydraulic system(redundancy) got that aircraft back on the ground safely.

As far a I know it is absolutely against regulation to have stick force lightening that regardless of what the risks are and an exception/amendment would have to be made which is something I don't think should be done.

The fan diameter of the PW GTF on a regional jet, like the embraer E2, is larger than the LEAP 1b for the Boeing 737 MAX. This gives some perspective. Even the fan diameter of the CFM56 is very large for 737NG. That's why the engine isn't circular.

reidar76 wrote:

The fan diameter of the PW GTF on a regional jet, like the embraer E2, is larger than the LEAP 1b for the Boeing 737 MAX. This gives some perspective. Even the fan diameter of the CFM56 is very large for 737NG. That's why the engine isn't circular.

It all comes down to ground clearance issues. IIRC the nacelle could be flattened at the bottom by moving some of the accessories to the sides instead of their usual location on the bottom.



The A320 version of basically the same engine has a circular nacelle.

the 737 is a horse that has run it's race and gone it's nearly last mile. with the Max 8,9,10? the tribe has died. Boeing needs to get on with a new design and do it with an eye for the Next 50 years.

Yes, it would have solved the problem. But not for the reasons you may think. In order to be competitive with the Neo, it would have need a fan diameter of roughly the same size. To make that fit, they'd have to fit a new MLG and NLG and install overwing evacuation slides. That would have invalidated the grandfathering rights, which would have meant they might as well start with a clean slate.

So, yes, it would have solved the problem, but at the cost of killing the 737.

JohanTally wrote:

TWFlyGuy wrote:

strfyr51 wrote:

No! the problem isn't the engines. It was the stall protection MCAS system!

Wasn't the MCAS install needed because the engines had to be set up higher on the pylon than previous models? So as a result, it is the engines. As the end of the day, it's a management failure to build a new design years ago instead of sitting on their hands.

MCAS was put on the MAX to make it's handling characteristics be so similar to the NG that pilots didn't need simulator training. By doing so airlines would save money on training which ultimately makes ordering the MAX more attractive. The higher placement of the engines does increase lift during high thrust settings but they could of trained pilots to be cognizant of this and to be diligent in preventing the aircraft attitude from going out of limits of safe operating envelope. Instead they put a digital fix on a analog aircraft.

the MCAS system is rights now why the 737Max is grounded. Boeing came up with the MCAS system to NOT have to add a particular simulator for the 737MAX, and they Half assed the system by #1) only tying the MCAS system to ONE Angle of attack vane, #2) having the Angle of attack indication sold as an option rather than a primary indication #3) by Not having any override if the system failed and the only AOA vane attached was damaged or inop. You might be able to tell these OTHER guys your opinions But you can look it up and SEE what the overall reasoning was. The AOA has always been a comparator system where if One side is out of whack? the other side should be giving proper indication. And? It was never tied to the Primary control system, UNTIL Boeing got "cute" and tied that BS to the pitch trim system. That's what primarily caused those crashes. We can dance around that all damn Day! but? The Truth is the truth! So ? Answer me this? Why did no US 737 Max operator crash flying the MAX? Why? Because they all had 737's of earlier vintage and they all already HAD the AOA indication and they could readily see if the Capt's AOA was out of whack. Not one of those carriers had less than 500,000 hours flying the 737. That's WHY no US based 737 operator had a crash. So Unless there's NEW evidence to the Contrary? them all you have to do is look at the FAA docket on the 737MAX to see why it's grounded. As then you might understand why the FAA is so damn hacked off at Boeing and with GOOD reason!