Moderators: richierich, ua900, PanAm_DC10, hOMSaR

 
UA444
Topic Author
Posts: 2992
Joined: Sun Mar 09, 2014 7:03 am

Would the MAX be having issues if it had the PW GTF?

Wed Mar 11, 2020 6:47 pm

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?
 
speedbird52
Posts: 1013
Joined: Sat Nov 26, 2016 5:30 am

Re: Would the MAX be having issues if it had the PW GTF?

Wed Mar 11, 2020 6:55 pm

Aren't the GTFs practically the same size?
 
arcticcruiser
Posts: 439
Joined: Tue Aug 22, 2017 2:16 pm

Re: Would the MAX be having issues if it had the PW GTF?

Wed Mar 11, 2020 7:31 pm

Well they would be pretty much the same size, just a little bit lighter.
 
strfyr51
Posts: 4899
Joined: Tue Apr 10, 2012 5:04 pm

Re: Would the MAX be having issues if it had the PW GTF?

Wed Mar 11, 2020 7:52 pm

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!
 
TWFlyGuy
Posts: 426
Joined: Mon Apr 17, 2017 5:10 pm

Re: Would the MAX be having issues if it had the PW GTF?

Wed Mar 11, 2020 8:12 pm

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.
 
User avatar
seahawk
Posts: 9627
Joined: Fri May 27, 2005 1:29 am

Re: Would the MAX be having issues if it had the PW GTF?

Wed Mar 11, 2020 8:27 pm

It would be worse, as the GTF favours are a large fan.
 
JohanTally
Posts: 130
Joined: Tue Jun 18, 2019 3:44 am

Re: Would the MAX be having issues if it had the PW GTF?

Thu Mar 12, 2020 1:11 am

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.
 
unimproved
Posts: 184
Joined: Sun Jun 22, 2014 7:14 pm

Re: Would the MAX be having issues if it had the PW GTF?

Thu Mar 12, 2020 11:24 am

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.
 
744SPX
Posts: 216
Joined: Mon Jan 27, 2020 6:20 pm

Re: Would the MAX be having issues if it had the PW GTF?

Thu Mar 12, 2020 4:09 pm

What about CG changes from the new engine position?
 
User avatar
Horstroad
Posts: 514
Joined: Thu Apr 08, 2010 8:19 pm

Re: Would the MAX be having issues if it had the PW GTF?

Thu Mar 12, 2020 7:04 pm

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
 
User avatar
767333ER
Posts: 1169
Joined: Wed Jun 15, 2016 5:14 am

Re: Would the MAX be having issues if it had the PW GTF?

Thu Mar 12, 2020 11:42 pm

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.
Been on: 732 733 734 73G 738 752 763 A319 A320 A321 CRJ CR7 CRA/CR9 E145 E175 E190 F28 MD-82 MD-83 C172R C172S P2006T PA-28-180

2 ears for spatial hearing, 2 eyes for depth perception, 2 ears for balance... How did Boeing think 1 sensor was good enough?!
 
JohanTally
Posts: 130
Joined: Tue Jun 18, 2019 3:44 am

Re: Would the MAX be having issues if it had the PW GTF?

Fri Mar 13, 2020 4:11 am

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.
 
User avatar
Starlionblue
Posts: 19926
Joined: Fri Feb 27, 2004 9:54 pm

Re: Would the MAX be having issues if it had the PW GTF?

Fri Mar 13, 2020 8:35 am

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".
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
User avatar
767333ER
Posts: 1169
Joined: Wed Jun 15, 2016 5:14 am

Re: Would the MAX be having issues if it had the PW GTF?

Fri Mar 13, 2020 4:52 pm

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.
Been on: 732 733 734 73G 738 752 763 A319 A320 A321 CRJ CR7 CRA/CR9 E145 E175 E190 F28 MD-82 MD-83 C172R C172S P2006T PA-28-180

2 ears for spatial hearing, 2 eyes for depth perception, 2 ears for balance... How did Boeing think 1 sensor was good enough?!
 
User avatar
reidar76
Posts: 521
Joined: Sun Sep 27, 2015 5:16 pm

Re: Would the MAX be having issues if it had the PW GTF?

Fri Mar 13, 2020 10:07 pm

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.
 
User avatar
Starlionblue
Posts: 19926
Joined: Fri Feb 27, 2004 9:54 pm

Re: Would the MAX be having issues if it had the PW GTF?

Sun Mar 15, 2020 1:45 am

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.

Image

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

Image
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
strfyr51
Posts: 4899
Joined: Tue Apr 10, 2012 5:04 pm

Re: Would the MAX be having issues if it had the PW GTF?

Sun Mar 15, 2020 6:11 am

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.
 
B777LRF
Posts: 2682
Joined: Sun Nov 02, 2008 4:23 am

Re: Would the MAX be having issues if it had the PW GTF?

Sun Mar 29, 2020 1:15 pm

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.
Signature. You just read one.
 
strfyr51
Posts: 4899
Joined: Tue Apr 10, 2012 5:04 pm

Re: Would the MAX be having issues if it had the PW GTF?

Mon Mar 30, 2020 5:00 am

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!

Who is online

Users browsing this forum: No registered users and 22 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos