It's crazy to me that that would be an acceptable compromise.
With regard to the other point, I don't think anyone is advocating for very high aerodynamic stability. That would be a B52 carrying nuclear weapons. It was designed to be extremely stable and forgiving. That being said, you don't want to rely solely on stability augmentation for trimming an airliner.
It reminds me of Air Canada flight 143, the pilots lost both engines and power. yet they were able to land the plane safely on an abandoned airport. I'm not sure if that would be possible with a 737 Max.
That is what the RAT is for, alternative electrical power. If the entire electrical system is down, ie electrons no longer flow anywhere anyhow, then everyone is doomed. But that is up there with the tail falling off. The are no backups for the wings/tail either.
When I say stability control, we're not generally talking about unstable or "relaxed stability" airframes where the system failing would cause a pitching moment to accelerate rather than converge and the aircraft would tumble and disintegrate. From an efficiency and handling standpoint, this would be ideal, but it's only used in tactical military aircraft where the crew can bail if there's a problem.
In most cases, we're talking about preventing stall in a swept wing aircraft. Swept wings are necessary to cruise efficiently beyond ~300mph at high altitude so they have to stay obviously, however they have VERY poor stall characteristics. As such, we have to do some things to prevent the aircraft from stalling such as playing with trim, using a stick pusher, etc.
Layman here, but 737, 747, etc. don't have swept wings, right? So they all cruise inefficiently... but are in fact stable... which is the opposite of what you wrote earlier? Sorry, I'm just really confused.
BTW since it's been tossed around a lot, good stall response is when the whole wing stalls at the same time and both wings tend to stall together, therefore you get a clean lurch downward in a straight predictable line. Bad stall response is one part of one wing stalling before the rest such that the wing drops and the plane has to be fought to avoid a spin or if extreme enough, a tail slide or extreme side slip.
They do, in fact, have swept wings.
Suppose, for instance, that an aircraft needs more yaw stability.
There's all sorts of design choices that could be made, but consider either A: a larger vertical stabilizer or B: automatic application of the rudder to damp oscillations.
The vertical stabilizer here is essentially a bit of metal. We know very, very well what can go wrong with bits of metal. Fatigue, corrosion, manufacturing defects, bad repairs... But, in 2019, we've pretty much figured out the failure modes of big bits of metal on an aircraft, and we generally know how to prevent and/or minimize them.
Now, the dynamic stabilization approach. We'll need gyroscope data (from the IRS, probably), a software model of flight dynamics (which almost certainly already exists and is running), and possibly faster servo valves for the rudder actuator.
This can work! We can formally verify that the control system we've created damps oscillations throughout all normal flight regimes. The gyroscopes are already redundant and well-tested. And you might not even need the faster servos.
Problem is, now avionics failures are even scarier. Will the stabilization here still operate when you get dropped into secondary mode? Probably not- so now, in unexpected situations, pilots need to keep in the back of their minds that yaw oscillations are more possible, that they may need to damp them manually, etc, etc.
Now you throw in some extra factors- turbulence, IMC (which would probably make detecting those oscillations manually that much more stressful), and trying to solve whatever problem dropped you into secondary mode in the first place... and you have something a bit concerning!
A bit of metal won't do that to you. We can make much better estimates of a bit of metal's reliability, and its failures are also less correlated- they aren't much more likely to crop up when you already have another problem.
That said, the cost of not using latest fuel efficient airplane would indeed be huge and the actual reliability of modern aircraft is very high and has been increasing over the years in which fuel efficiency also increased.
Sometimes, human can hit on a formula that produces objects that satisfy all the given parameters more fully rather than compromising on any of the requirement. But it's quite plausible that these formulas cannot be milked forever - thus the "Max" may be the point where tradeoffs stop working.
A quick look at the numbers suggests that a 737 MAX 8 is about 10% more efficient on fuel burn compared to a 737 300. That is not "massive" in my book and I'm more than happy to pay a little bit more per ticket if it means a higher safety margin.
Did you mean something older and less efficient than a 737 300?
As a curious bystander, I assumed using fly by wire tech to achieve stability would involve using control surfaces, which increase drag by their nature. How would an airframe that's naturally stable and doesn't require control inputs burn more fuel?
That said, an easy (but different) case to visualize is a traditional tailplane. The center of gravity on an airplane is in front of the wing so it wants to pitch down slowly. The tail pushes DOWN in the back to keep the nose up. Nose heavy planes are stable and forgiving but you induce drag because the wing needs to supply some lift just to counteract the tail which is producing negative lift. If you move the CG backward, you get less stability because the airplane wants to pitch up/down more violently with a control input but you have less negative lift from the tail.
We don’t build planes with training wheels anymore because the performance cost was too high. Planes are still the safest way to travel even without the training wheels.
I don’t think 737 MAX 8 pushes the envelope too far. I think they screwed up on re-training the disengage, and they may have screwed up on redundancy by only using a single AoA sensor, but I also am guessing the latest crash has absolutely nothing to do with trim.
Makes sense then, that those opposing aerodynamic forces induce drag.
The original design of the 737 did not have ovoid inlets.
You can see regular circular nacelle inlets on the 737-100:
https://secure.boeingimages.com/archive/Boeing-737-100-2JRSX...
and on the 737-200 here:
https://secure.boeingimages.com/Assets/V2/jrZYYwCXohU1rDmk4e...
The ovoid inlet design was introduced with the 737-300, when the engine was changed to the CFM56.
His tweet sounds dumb but there is some truth in it.
As you say, planes and procedures have become very complicated. And I think there are only two options: making planes simple again which make them less efficient or let computers fly the plane and make the interface simple(r).
If you look at the rockets of SpaceX then you can say they are the extreme form of fly by wire and very instable when it comes to aerodynamics. But computers can land them within centimeters when they fall out of space.
So maybe that will be the future. Planes that are very efficient instable flying 'rockets' that are controlled by computers.
There really isn't. Automation is part of what has made flying safer over the years. Also, compare the cockpit of an Airbus with e.g. an old B737, the 300 series for instance. The Airbus cockpit is much simpler, in the sense that there are less gauges and knobs for the pilots to be concerned about. Automation has, over all, made things simpler and safer.
The most convincing popular article I've read on this topic is https://www.vanityfair.com/news/business/2014/10/air-france-...
It's far from clear-cut that the way automation is happening is advisable, however conservative it might appear to be, and I'm sure you'd agree that there are many confounding variables that make it difficult to say just what is responsible for the trajectory of aircraft safety. There's not much of a control group of advanced modern aircraft which omit automated features.
Fast forward to today where airport infrastructure is much more developed and these small/medium size airliners are being pressed into front line service including intercontinental routes. The aircraft has changed drastically to accommodate these changes through the years, enough that it may be time for a clean sheet design. They've changed just about everything on the air-frame from the fuel load/cabin length/wing to the avionics to make this all work.
Now, the other side of that coin is with systems. In theory this should be fine, but obviously isn't. It's hard to differentiate bandaids from regular systems and if either fails then safety is compromised. Obviously the amount of unnecessary systems should be minimized but as time goes on more systems WILL be added to gain the rewards of automation, which is a good thing. As such, we need to educate pilots on ALL of the systems, and rigorously test them before they enter service.
Additionally, if you do as the pilots want and achieve very high aerodynamic stability through the air-frame instead of stability control systems (fly by wire essentially) it reduces the aerodynamic efficiency of the airliner, particularly with current conventional designs.