29 ms·

The airframe isn't getting old. In fact there's nothing left of the old airframe but the general shape of the windshields. It's the type rating approval proces

by lstodd 8y ago

The airframe isn't getting old. In fact there's nothing left of the old airframe but the general shape of the windshields. It's the type rating approval process that got old and caused all this.

nabla9 8y ago
Many design choices still exist. Some design constraints were irrelevant already when the plane was introduced, yet they still exist and haunt the plane. They made the ground clearance as small as possible, because 737 engineers assumed that people have to walk stairs to the ground level to enter and exit the plane. The luggage and serving of the plane was also done by hand without lifters at that time. This unfortunate choice led to engine placement that increased fuel consumption they tried to fix. Newly designed aircraft would have better handling without these fixes.
JorgeGT 8y ago
The 737 is a great example of a Ship of Theseus, years of small changes have left barely anything of the original besides the name... and the type certificate.
- bunderbunder 8y ago
  And, apparently, sitting very low on the tarmac. What I haven't seen yet, and would love to see, is an explanation of why they went for this cascade of apparent band-aid solutions, instead of just adjusting the landing gear to give them more options for where to put the engines. I'm sure everything I'm reading is an oversimplification, but, from what I have read, it sure sounds like the crux of the problem here is that they put the moment of thrust in the wrong spot.
  - WalterBright 8y ago
    Lengthening the main landing gear would require a near total redesign of the wing, as the gear would have to be moved further outboard.
    - burfog 8y ago
      That was but one of many options, all with pros and cons. It does appear that there is a bit of room to move the gear attachment point outward. Internal stuff might need to be relocated. A very nice solution is to fold the landing gear as the B52 bomber does, asymmetrically with one in front of the other. Internal stuff almost certainly would need to be moved around, and then doors would be required. The doors would probably fit, unlike on the original, so that would be a nice upgrade. Boeing did add some fancy stuff (on the 737MAX-10 only) to lengthen the gear right before lifting into the air and then unlengthen it as it gets retracted. The nice thing about this choice is that there need not be any changes to the height of airport equipment unless the fancy mechanism wasn't used for the nose gear. So that helps: food/maid truck, fuel truck, baggage truck, jetway or airstairs, etc. Another option is to keep the aircraft low. This of course makes it much harder to increase the frontal area of the engines while keeping the aircraft with a pair of under-wing podded engines. We can imagine playing with the definition of "engine", installing units that have pairs of side-by-side turbines that can only be operated or maintained as a complete unit. We can imagine a much higher engine mounting, with some of the bypass air flowing over the top of the wing. We can imagine moving the engines outward to give more clearance due to wing shape, at the cost of being less-capable of crosswind landings and being more difficult to fly straight when an engine is out. Or they could just do a clean new design.
  - JorgeGT 8y ago
    Here's Gary Hamatani, chief project engineer for Boeing's 737 MAX program, explaining that they needed the main landing gear to fit the existing wheel wells: https://www.youtube.com/watch?v=F4IGl4OizM4 https://www.youtube.com/watch?v=F4IGl4OizM4 I find it very illustrative, as it contains the keywords that are at issue here: "we wanted to preserve commonality", "from a pilot's perspective there's absolutely nothing different", etc.
- growlist 8y ago
  Or Trigger's Broom (for those of us in the UK): https://www.youtube.com/watch?v=56yN2zHtofM https://www.youtube.com/watch?v=56yN2zHtofM
the_mitsuhiko 8y ago
How exactly is the approval process at fault here? Nobody forced Boeing to make a plane that has the same type rating.
- JorgeGT 8y ago
  The approval process allowing indefinite "type certificate stretching" may create a perverse economic incentive for companies to mask or downplay relevant changes to the aircraft.
- BurningFrog 8y ago
  It would cost some number of $B and years to get different type rating. If you want to call that "forcing" is a matter of taste, but it's certainly a very strong and involuntary incentive.
  - ctvo 8y ago
    Boeing made the decision to maximize profits by retrofitting an older model. There’s nothing involuntary about it. They’ve released newer model planes that have gone through the review process fine, correct?
    - js2 8y ago
      FWIW, according to Wikipedia Boeing had intended to design a new plane but were forced into re-engineing the 737 by market forces: > In 2006, Boeing started considering the replacement of the 737 with a "clean-sheet" design that could follow the Boeing 787 Dreamliner.[12] In June 2010, a decision on this replacement was postponed into 2011.[13] > On December 1, 2010, Boeing's competitor, Airbus, launched the Airbus A320neo family to improve fuel burn and operating efficiency with new engines: the CFM International LEAP and Pratt & Whitney PW1000G.[14] In February 2011, Boeing's CEO Jim McNerney maintained "We're going to do a new airplane."[15] At the March 2011 ISTAT conference, BCA President James Albaugh was not sure about a 737 re-engine, like Boeing CFO James A. Bell stated at the JP Morgan Aviation, Transportation and Defense conference the same month.[16] The A320neo gathered 667 commitments at the June 2011 Paris Air Show for a backlog of 1,029 units since its launch, setting an order record for a new commercial airliner.[17] > On July 20, 2011, American Airlines announced an order for 460 narrowbody jets including 130 A320ceos and 130 A320neos, and intended to order 100 re-engined 737s with CFM LEAPs, pending Boeing confirmation.[18] The order broke Boeing's monopoly with the airline and forced Boeing into a re-engined 737. https://en.wikipedia.org/wiki/Boeing_737_MAX#Background https://en.wikipedia.org/wiki/Boeing_737_MAX#Background

by lstodd 8y ago

The airframe isn't getting old. In fact there's nothing left of the old airframe but the general shape of the windshields. It's the type rating approval process that got old and caused all this.

nabla9 8y ago

Many design choices still exist. Some design constraints were irrelevant already when the plane was introduced, yet they still exist and haunt the plane. They made the ground clearance as small as possible, because 737 engineers assumed that people have to walk stairs to the ground level to enter and exit the plane. The luggage and serving of the plane was also done by hand without lifters at that time. This unfortunate choice led to engine placement that increased fuel consumption they tried to fix. Newly designed aircraft would have better handling without these fixes.

JorgeGT 8y ago

The 737 is a great example of a Ship of Theseus, years of small changes have left barely anything of the original besides the name... and the type certificate.

bunderbunder 8y ago
And, apparently, sitting very low on the tarmac. What I haven't seen yet, and would love to see, is an explanation of why they went for this cascade of apparent band-aid solutions, instead of just adjusting the landing gear to give them more options for where to put the engines. I'm sure everything I'm reading is an oversimplification, but, from what I have read, it sure sounds like the crux of the problem here is that they put the moment of thrust in the wrong spot.
- WalterBright 8y ago
  Lengthening the main landing gear would require a near total redesign of the wing, as the gear would have to be moved further outboard.
  - burfog 8y ago
    That was but one of many options, all with pros and cons. It does appear that there is a bit of room to move the gear attachment point outward. Internal stuff might need to be relocated. A very nice solution is to fold the landing gear as the B52 bomber does, asymmetrically with one in front of the other. Internal stuff almost certainly would need to be moved around, and then doors would be required. The doors would probably fit, unlike on the original, so that would be a nice upgrade. Boeing did add some fancy stuff (on the 737MAX-10 only) to lengthen the gear right before lifting into the air and then unlengthen it as it gets retracted. The nice thing about this choice is that there need not be any changes to the height of airport equipment unless the fancy mechanism wasn't used for the nose gear. So that helps: food/maid truck, fuel truck, baggage truck, jetway or airstairs, etc. Another option is to keep the aircraft low. This of course makes it much harder to increase the frontal area of the engines while keeping the aircraft with a pair of under-wing podded engines. We can imagine playing with the definition of "engine", installing units that have pairs of side-by-side turbines that can only be operated or maintained as a complete unit. We can imagine a much higher engine mounting, with some of the bypass air flowing over the top of the wing. We can imagine moving the engines outward to give more clearance due to wing shape, at the cost of being less-capable of crosswind landings and being more difficult to fly straight when an engine is out. Or they could just do a clean new design.
- JorgeGT 8y ago
  Here's Gary Hamatani, chief project engineer for Boeing's 737 MAX program, explaining that they needed the main landing gear to fit the existing wheel wells: https://www.youtube.com/watch?v=F4IGl4OizM4 https://www.youtube.com/watch?v=F4IGl4OizM4 I find it very illustrative, as it contains the keywords that are at issue here: "we wanted to preserve commonality", "from a pilot's perspective there's absolutely nothing different", etc.
growlist 8y ago
Or Trigger's Broom (for those of us in the UK): https://www.youtube.com/watch?v=56yN2zHtofM https://www.youtube.com/watch?v=56yN2zHtofM

the_mitsuhiko 8y ago

How exactly is the approval process at fault here? Nobody forced Boeing to make a plane that has the same type rating.

JorgeGT 8y ago
The approval process allowing indefinite "type certificate stretching" may create a perverse economic incentive for companies to mask or downplay relevant changes to the aircraft.
BurningFrog 8y ago
It would cost some number of $B and years to get different type rating. If you want to call that "forcing" is a matter of taste, but it's certainly a very strong and involuntary incentive.
- ctvo 8y ago
  Boeing made the decision to maximize profits by retrofitting an older model. There’s nothing involuntary about it. They’ve released newer model planes that have gone through the review process fine, correct?
  - js2 8y ago
    FWIW, according to Wikipedia Boeing had intended to design a new plane but were forced into re-engineing the 737 by market forces: > In 2006, Boeing started considering the replacement of the 737 with a "clean-sheet" design that could follow the Boeing 787 Dreamliner.[12] In June 2010, a decision on this replacement was postponed into 2011.[13] > On December 1, 2010, Boeing's competitor, Airbus, launched the Airbus A320neo family to improve fuel burn and operating efficiency with new engines: the CFM International LEAP and Pratt & Whitney PW1000G.[14] In February 2011, Boeing's CEO Jim McNerney maintained "We're going to do a new airplane."[15] At the March 2011 ISTAT conference, BCA President James Albaugh was not sure about a 737 re-engine, like Boeing CFO James A. Bell stated at the JP Morgan Aviation, Transportation and Defense conference the same month.[16] The A320neo gathered 667 commitments at the June 2011 Paris Air Show for a backlog of 1,029 units since its launch, setting an order record for a new commercial airliner.[17] > On July 20, 2011, American Airlines announced an order for 460 narrowbody jets including 130 A320ceos and 130 A320neos, and intended to order 100 re-engined 737s with CFM LEAPs, pending Boeing confirmation.[18] The order broke Boeing's monopoly with the airline and forced Boeing into a re-engined 737. https://en.wikipedia.org/wiki/Boeing_737_MAX#Background https://en.wikipedia.org/wiki/Boeing_737_MAX#Background