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It strikes me how a seemingly insignificant decision at the time - to position fuselage slightly higher above the ground - gave Airbus a strategic advantage 50

by mcsoft 7y ago

It strikes me how a seemingly insignificant decision at the time - to position fuselage slightly higher above the ground - gave Airbus a strategic advantage 50 years later. It forced the competitor into a services of unexplainable and reckless decisions that break basic principles of reliable engineering. Which in turn led to a very visible disastrous business consequences: Boeing had to silently reduce 737 MAX production despite having secured orders for over 5000 planes. A case to be studied in business schools.

techslave 7y ago
basic principles? i think that’s a bit far. the plane isn’t inherently unstable is it? i thought it’s just the black box of MCAS that is the problem and MCAS is there to avoid a lengthy type certification. it’s completely explainable. and it wasn’t seemingly insignificant. it was for fuel efficiency. it was significant and they knew what they were doing.
- mcsoft 7y ago
  They had to install MCAS because the plane was unstable in high AoA mode, i.e. during takeoff. And it was unstable because larger CFM engines could not fit under the wing anymore so they had to put it further forward and a bit up. This increased the pitch up moment when a full power is applied. Also, can't really see how the height of the fuselage above the ground affects fuel efficiency.
  - hotsauceror 7y ago
    "Also, can't really see how the height of the fuselage above the ground affects fuel efficiency." It doesn't. They wanted to use a larger, more fuel-efficient engine but the 737's ground clearance couldn't accomodate it. So they moved the engine forward.
  - cesarb 7y ago
    > They had to install MCAS because the plane was unstable in high AoA mode, i.e. during takeoff. Forgive me if I'm missing something, but isn't MCAS disabled while the flaps are extended, which is the case during takeoff and landing?
    - ummonk 7y ago
      Yup. The real danger was during climb I believe. And it wasn’t unstable, just had a backwards feel at high angle of attacks which could lead to pilots inadvertently stalling it.
    - mcsoft 7y ago
      You are right though pilots prefer to retract flaps soon after liftoff since extended flaps mean more drag and less efficiency. And the danger comes from the low altitude thus no margin for error. In the doomed ET302 flight they retracted flaps 62 seconds after liftoff at only about 1200ft above the ground. MCAS kicked in 5 seconds later. Had autopilot been engaged it'd also had saved them from MCAS trim down commands.
- hotsauceror 7y ago
  Seems to me that redundancy in mission critical systems where failure means loss of several hundred lives is a basic engineering principle. MCAS apparently relied on a single AOA sensor's input. The system had no way to validate the data or handle a mismatch, and the only recourse was to light up an (optional) disagreement indicator - but still relied on just the one sensor to apply control forces.
- lagadu 7y ago
  Well, yes: the plane is inherently unstable. That's why the MCAS system is there. The system itself is mostly fine, it does what it's intended to under ordinary conditions. The problem was that Boeing, in order to avoid costs to the buyer, declared that pilots did not require training on it and made the instrumentation that manages the system woefully inadequate to the task of handling malfunctions (plus the system relying on a single sensor is pretty brittle but adequate malfunction handling instruments would've mitigated that).
erentz 7y ago
Had Boeing built the 737 at the time Airbus built the A320 they would've had a taller undercarriage also. For example the narrow body 757 built around the time of the A320 does have this. When the 737 was built back in the 60s it was intended to be a small regional jet, not the continent and ocean crossing aircraft it evolved into over the years since. It originally came with a retractable staircase for passengers to embark/alight the aircraft, and having a low fuselage also made it possible to hand load the luggage in a time before widespread belt loaders.
- deskamess 7y ago
  Why would they not have gone with a, say, 757 MAX - it seems to fit the bill spec wise. Is it that global pilot pool is not as great for the 757 as 737?
  - staunch 7y ago
    I don't think it matters how big the global pilot pool is for 737s. What matters to a specific airline is how many of their pilots are type rated for a particular aircraft. An airline that has standardized on the 737 is going to have a pool made up of mostly 737 rated pilots.
  - nwallin 7y ago
    The 757 "max" is a 767. 757s and 767s share a common type rating. It's not so much that the pilot pool is lacking, it's that a lot of airlines have a pool of existing 737 pilots already on their payroll. If you need to lay off half your employees, and replace them with an entire new pool of people, half of them are going to be terrible employees, and it will take you years to weed out the bad ones. For better or worse, pilot unions tend to be very strong. Firing them is difficult. The 737 MAX wasn't beset by technical problems, they were social and political ones.
    - CydeWeys 7y ago
      Huh? There's no such thing as a "737 pilot", there is a "pilot with 737 type rating". It's the whole "becoming a pilot in the first place" part that's hard, not certifying a new type. Plenty of pilots are certified to fly multiple types. The fundamentals of flight are the same across all planes. The airlines would've just had to retrain their existing pilots to fly the new type. It's not nothing, but it's a lot less worse than massive lay-offs and rehiring.
anticensor 7y ago
You mean genetic algorithms at work?

by mcsoft 7y ago

techslave 7y ago

basic principles? i think that’s a bit far. the plane isn’t inherently unstable is it? i thought it’s just the black box of MCAS that is the problem and MCAS is there to avoid a lengthy type certification. it’s completely explainable. and it wasn’t seemingly insignificant. it was for fuel efficiency. it was significant and they knew what they were doing.

mcsoft 7y ago
They had to install MCAS because the plane was unstable in high AoA mode, i.e. during takeoff. And it was unstable because larger CFM engines could not fit under the wing anymore so they had to put it further forward and a bit up. This increased the pitch up moment when a full power is applied. Also, can't really see how the height of the fuselage above the ground affects fuel efficiency.
- hotsauceror 7y ago
  "Also, can't really see how the height of the fuselage above the ground affects fuel efficiency." It doesn't. They wanted to use a larger, more fuel-efficient engine but the 737's ground clearance couldn't accomodate it. So they moved the engine forward.
- cesarb 7y ago
  > They had to install MCAS because the plane was unstable in high AoA mode, i.e. during takeoff. Forgive me if I'm missing something, but isn't MCAS disabled while the flaps are extended, which is the case during takeoff and landing?
  - ummonk 7y ago
    Yup. The real danger was during climb I believe. And it wasn’t unstable, just had a backwards feel at high angle of attacks which could lead to pilots inadvertently stalling it.
  - mcsoft 7y ago
    You are right though pilots prefer to retract flaps soon after liftoff since extended flaps mean more drag and less efficiency. And the danger comes from the low altitude thus no margin for error. In the doomed ET302 flight they retracted flaps 62 seconds after liftoff at only about 1200ft above the ground. MCAS kicked in 5 seconds later. Had autopilot been engaged it'd also had saved them from MCAS trim down commands.
hotsauceror 7y ago
Seems to me that redundancy in mission critical systems where failure means loss of several hundred lives is a basic engineering principle. MCAS apparently relied on a single AOA sensor's input. The system had no way to validate the data or handle a mismatch, and the only recourse was to light up an (optional) disagreement indicator - but still relied on just the one sensor to apply control forces.
lagadu 7y ago
Well, yes: the plane is inherently unstable. That's why the MCAS system is there. The system itself is mostly fine, it does what it's intended to under ordinary conditions. The problem was that Boeing, in order to avoid costs to the buyer, declared that pilots did not require training on it and made the instrumentation that manages the system woefully inadequate to the task of handling malfunctions (plus the system relying on a single sensor is pretty brittle but adequate malfunction handling instruments would've mitigated that).

erentz 7y ago

Had Boeing built the 737 at the time Airbus built the A320 they would've had a taller undercarriage also. For example the narrow body 757 built around the time of the A320 does have this. When the 737 was built back in the 60s it was intended to be a small regional jet, not the continent and ocean crossing aircraft it evolved into over the years since. It originally came with a retractable staircase for passengers to embark/alight the aircraft, and having a low fuselage also made it possible to hand load the luggage in a time before widespread belt loaders.

deskamess 7y ago
Why would they not have gone with a, say, 757 MAX - it seems to fit the bill spec wise. Is it that global pilot pool is not as great for the 757 as 737?
- staunch 7y ago
  I don't think it matters how big the global pilot pool is for 737s. What matters to a specific airline is how many of their pilots are type rated for a particular aircraft. An airline that has standardized on the 737 is going to have a pool made up of mostly 737 rated pilots.
- nwallin 7y ago
  The 757 "max" is a 767. 757s and 767s share a common type rating. It's not so much that the pilot pool is lacking, it's that a lot of airlines have a pool of existing 737 pilots already on their payroll. If you need to lay off half your employees, and replace them with an entire new pool of people, half of them are going to be terrible employees, and it will take you years to weed out the bad ones. For better or worse, pilot unions tend to be very strong. Firing them is difficult. The 737 MAX wasn't beset by technical problems, they were social and political ones.
  - CydeWeys 7y ago
    Huh? There's no such thing as a "737 pilot", there is a "pilot with 737 type rating". It's the whole "becoming a pilot in the first place" part that's hard, not certifying a new type. Plenty of pilots are certified to fly multiple types. The fundamentals of flight are the same across all planes. The airlines would've just had to retrain their existing pilots to fly the new type. It's not nothing, but it's a lot less worse than massive lay-offs and rehiring.

anticensor 7y ago

You mean genetic algorithms at work?