7 ms·
How do you know the airframe is fundamentally flawed? ("the engines are too big" is not an answer).
by rrss 7y ago
How do you know the airframe is fundamentally flawed? ("the engines are too big" is not an answer).
- dboreham 7y agoThe wings are too low?
- notjustanymike 7y agoKeeps crashing into the ocean
- toomuchtodo 7y agoIf the airframe isn’t flawed, fly it without MCAS. With Boeing management onboard. Surely you don’t need to dynamically adjust flight dynamics without the pilot’s input or knowledge if the airframe is sound. It’s realistic to build aircraft where software is required to fly said aircraft depending on the flight dynamics, and the pilot(s) are fully aware of what’s running. But that changes the type rating and blows Boeing’s regulatory sidestep out of the sky.
- TylerE 7y agoGod it's frustrating seeing people here talk about aviation. Flight computers are a fundamental part of normal aeronautical design. Asking Boeing to fly a Max without MCAS would be like asking you to write a bug free C++ program... with a compiler with no error messages or validation.
- toomuchtodo 7y ago[removed] Other sibling comments are of higher quality.
- TylerE 7y agoBetter not ever fly on an Airbus then, either. https://en.wikipedia.org/wiki/Air_France_Flight_296 https://en.wikipedia.org/wiki/Air_France_Flight_296 https://www.telegraph.co.uk/technology/9231855/Air-France-Flight-447-Damn-it-were-going-to-crash.html https://www.telegraph.co.uk/technology/9231855/Air-France-Fl...
- windexh8er 7y agoThe MCAS was a workaround implemented as a stopgap, no? How does this fall under the broad category of a flight computer as you've stated? What other airliners have been retrofitted with similar systems? Why doesn't a non-Max 737 need MCAS?
- ethbro 7y agoNo. It was a software fix put in place to satisfy a regulatory requirement under specific, known flight conditions. The following planes (among others) all translate flight inputs. Airbus A320, A330, A340, A350, A380; Boeing 777. https://en.m.wikipedia.org/wiki/Flight_control_modes https://en.m.wikipedia.org/wiki/Flight_control_modes A non-Max 737 doesn't need MCAS because it already behaves like a 737. Essentially, most replies on this boil down to people being shocked (shocked!) that computers are currently helping all planes fly. I'm not sure how they thought AEs were getting efficiency gains while physics stayed the same...
- AnthonBerg 7y agoThe replies do not all boil down to people being shocked that computers help planes fly. That is a willfully distorted charicature. Hundreds of people were killed due to a bad implementation of a deeply irresponsible and insensible approach to make money by skirting flight safety regulation. The bad implementation was in part software, but nobody is confusing that aspect with the whole picture. The 737 MAX does not need MCAS. Nothing needs MCAS. Boeing executives wanted the money that MCAS made them.
- ethbro 7y agoIs it really? If that were the case, then you'd see people debating the relative merits of SDLC approaches and organizational blinders to letting bugs slip through. In reality, that's only about 20% of any Boeing discussion. 80% is outrage about how Boeing could have released such an "obviously flawed" airplane that required flight computer adjustments. And misunderstanding that Boeing pivoted from a clean sheet design to instead build exactly what the carriers asked them to. Generally, HN comments are pretty good, but the amount of kneejerking in Boeing threads in lieu of informed discussion is terrible. Edit: Although reading through new replies this morning, it's nice to see voting mostly sorted the technical wheat from the chaff.
- miketery 7y agoYou're wrong. Sophisticated flight computers are only necessary for aircrafts that are inheritenly unstable (fighter jets) that require special flight characteristics. Safe commercial, and private aircraft are built to be inheritenly stable. It's less complexity. Sure we've added fly by wire, or dynamic power controls. But those are relatively straight forward. Changing the center of gravity of the plane and therefore introducing different (dangerous, risky, and unsafe) flight charectierstics is a major issue.
- TylerE 7y agoDefine "necessary". Depending on how exactly you define it, pilot error is either the #1 or #2 cause of commercial plane crashes. FBW systems seek to reduce or eliminate that.
- ummonk 7y agoThat's not true for Boeing aircraft. They are designed to be flyable manually, unlike Airbuses, which are fly by wire.
- TylerE 7y agoThe 777, 787, 747-8, and 737 Max are all fly by wire.
- inamberclad 7y agoThe Max is not fly by wire, that's the problem. It's a hydraulic/mechanical control. That's why pilots aren't able to pull it out of dives or re-trim it, the aerodynamic forces are too much for the crew to fight against.
- Animats 7y agoRight. If this was a fly by wire aircraft, it would have to have triple or quadruple redundant control systems and redundant air data sensors. But because the auto-trim system wasn't considered primary flight control, it didn't get evaluated like a fly by wire system. Auto-trim has been around for years, and failures are usually more annoying than serious. But the 737 MAX's auto-trim had far too much control authority, and was being used to compensate for bad handling characteristics, making it a flight critical system.
- usrusr 7y agoAnd if they hadn't opted for secrecy, properly put it in the manual instead of hoping that the outcome of bad sensor readings would appear like that of a fried switch, someone might have realized what a perfect trap they had built while writing "engage trim cut-out, then work the manual trim wheel until you regain control or hit the ground, whatever comes first".
- ulfw 7y agoNeither is the 747-8. Half of his examples were made up.
- benj111 7y ago"God it's frustrating seeing people here talk about aviation" Google the 'Murray Gell-Mann Amnesia effect'. Edit: https://en.m.wikipedia.org/wiki/Gell-Mann_amnesia_effect https://en.m.wikipedia.org/wiki/Gell-Mann_amnesia_effect
- natch 7y agoIsn’t the engines being not mountable at a well balanced point a big part of the answer? Which isn’t down to only the size of the engine but also the height of the wings. So yes it’s complicated but the engine is part of the picture. Although not being in the industry, I don’t know, is a strap-on engine added to a design that wasn’t intended to accommodate it technically considered part of the airframe?
- _ph_ 7y agoBasically no jet engine at any airliner are mounted at a point which is well-balanced in all flight situations. At level flight, the 737 MAX is also well balanced. That is just a matter of weight distribution in the machine. The problem appears at high angle of attacks, that means the force vector isn't pointing vertically down as it were only due to gravity. In this situation, the balance of every aircraft which has large engines hanging down from the wings does shift and needs to be compensated for in some way in the control systems.
- djsumdog 7y agoLike the hundreds of other comments on here mentioning how the engines were too far forward. The 737 was originally designed to be low to the ground, and rather than raising the jet and placing engines where they are on other similar planes (meaning it could no longer be classified as a 737 and requiring new manuals/training/certification), they moved them forward and adjusted for the new unexpected handling with the MCAS.
- blackflame7000 7y agoRaising the jet requires a wider body for the landing gear to fold up into
- kayfox 7y agoThe 757 sits a good 4 feet higher with the same fuselage diameter.
- 0az 7y agoIf I remember correctly, the 737 either doesn't have the space for longer landing gear, or there's an issue with the longer landing gear, or both. Citation needed, of course, as this is off of memory.
- kayfox 7y agoIt was designed lower to be easier to work with ground handling and servicing. This lead to a few different designs of plane-deployed airstairs and made it popular with Alaska Air and other airlines serving small airports. https://en.wikipedia.org/wiki/Boeing_737#Background https://en.wikipedia.org/wiki/Boeing_737#Background
- blackflame7000 7y agoThe 757 has a wingspan 30 feet wider than the 737. If you look at a picture of the airplane, you can see that the landing gear is part of the wing. https://qph.fs.quoracdn.net/main-qimg-0f650e809408f3962a1ed01f08a97470 https://qph.fs.quoracdn.net/main-qimg-0f650e809408f3962a1ed0...
- windexh8er 7y agoWe know because hundreds of people died in the airframe. We know the MCAS was a workaround to an aerodynamics problem. Boeing has admitted this both directly and indirectly. Airframes shouldn't need software fixes to accommodate for a design failure and design failures shouldn't be allowed to fly after killing hundreds of people. How do you argue what they did and are continuing to do is just in this situation?
- skybrian 7y agoUncrashable airplanes don't exist. The question isn't whether there were crashes (nobody disputes that). It's whether the problem can be fixed so that pilots can fly it safely. Given all the times the plane flew without incident (other than the two crashes), it seems this should be possible?
- visarga 7y agoYeah, it was perfectly safe except for two crashes. But that's two crashes more than I can tolerate. The problem is now the lack of public trust in their work. They might fix the software, but how to prove they're not lying again?
- ethbro 7y agoThe same way you prove Airbus isn't lying?
- callalex 7y agoPresumably Airbus is still being watched by a regulator or two. Unlike Boeing which has not been watched as the FAA has clearly been gutted.
- _ph_ 7y agoThe 737 MAX will be watched by all regulators world-wide. So it will be checked as carefuly, or actually even way more carefully than any competing aircraft.
- tus88 7y agoBecause MCAS is required, unlike every other aerodynamically stable airplane that came before it.
- deleted 7y ago[deleted]
- blackflame7000 7y agohttps://en.m.wikipedia.org/wiki/Qantas_Flight_72 https://en.m.wikipedia.org/wiki/Qantas_Flight_72
- makomk 7y agoQantas Flight 72 is probably a good demonstration of why using MCAS as a band-aid for the 737 MAX's stability issues is a bad idea. One of the key reasons that fault didn't lead to a crash that killed everyone on board is that Airbus placed much safer limits on the amount of control authority their flight envelope protections had and the altitude at which they could operate.
- danjayh 7y agoAirbus does it too. They have several control laws that are used to provide flight envelope protection. It was the pilot's failure to understand his plane's software that caused AF447 to crash. Essentially he didn't realize that the flight control software had changed modes, that it wasn't providing the normal handling augmentations, and that his inputs were putting the aircraft into a stall, which caused the crash. See: https://en.wikipedia.org/wiki/Air_France_Flight_447 https://en.wikipedia.org/wiki/Air_France_Flight_447 https://aviation.stackexchange.com/questions/62338/why-did-af447-never-return-to-normal-law https://aviation.stackexchange.com/questions/62338/why-did-a...
- tus88 7y agoBuild unstable airframes? Not outside of forward canard jet fighters. And that pilot crashed a perfectly fine airliner after he lost situational awareness and then did the one thing you should never do - pull the steering column back in a mad panic until the plane stalls.
- mseidl 7y agoThe plane was built in the 50s, it was low to the ground. But Boeing wanted to fit bigger/newer/better engines on it, but they wont fit since you can't make the landing gear longer. They had to move the engines higher and much more forward.